SecretStore: generating signatures (#5764)

* refactoring traits

* separate generation session

* generalized ClusterSessions

* signing session prototype

* full_signature_math_session

* consensus session prototype

* continue signing session

* continue signing session

* continue signing session

* continue signing session

* isolated consensus logic

* started work on signing test

* complete_gen_sign_session works

* consensus tests

* get rid of duplicated data in SigningSession

* TODOs in signing session

* fixing tests

* fixed last test

* signing session in http listener

* new key server tests

* fix after merge

* enabled warnings

* fixed possible race

* ignore previous jobs responses

* include sef node in consensus when confirmed

* fixed warning

* removed extra clones

* consensus_restarts_after_node_timeout

* encrypt signature before return

* return error text along with HTTP status

* fix for odd-of-N (share check fails + not equal to local sign)

* fixed t-of-N for odd t

* fixed test cases in complete_gen_sign_session

* fixed mistimed response reaction

* jobs draft

* DecryptionJob

* consensus session tets

* fixed decryption tests

* signing job implementation

* siginng_session using new consensus_session

* added license preambles

* same_consensus_group_returned_after_second_selection

* database upgrade v0 -> v1

* typo

* fixed grumbles

ethkey/src/secret.rs

@@ -92,6 +92,15 @@ impl Secret {
 		Ok(())
 	}
 
+	/// Inplace negate secret key (-scalar)
+	pub fn neg(&mut self) -> Result<(), Error> {
+		let mut key_secret = self.to_secp256k1_secret()?;
+		key_secret.mul_assign(&SECP256K1, &key::MINUS_ONE_KEY)?;
+
+		*self = key_secret.into();
+		Ok(())
+	}
+
 	/// Inplace inverse secret key (1 / scalar)
 	pub fn inv(&mut self) -> Result<(), Error> {
 		let mut key_secret = self.to_secp256k1_secret()?;

secret_store/src/acl_storage.rs

@@ -20,14 +20,14 @@ use parking_lot::Mutex;
 use ethkey::public_to_address;
 use ethcore::client::{Client, BlockChainClient, BlockId};
 use native_contracts::SecretStoreAclStorage;
-use types::all::{Error, DocumentAddress, Public};
+use types::all::{Error, ServerKeyId, Public};
 
 const ACL_CHECKER_CONTRACT_REGISTRY_NAME: &'static str = "secretstore_acl_checker";
 
 /// ACL storage of Secret Store
 pub trait AclStorage: Send + Sync {
 	/// Check if requestor with `public` key can access document with hash `document`
-	fn check(&self, public: &Public, document: &DocumentAddress) -> Result<bool, Error>;
+	fn check(&self, public: &Public, document: &ServerKeyId) -> Result<bool, Error>;
 }
 
 /// On-chain ACL storage implementation.
@@ -48,7 +48,7 @@ impl OnChainAclStorage {
 }
 
 impl AclStorage for OnChainAclStorage {
-	fn check(&self, public: &Public, document: &DocumentAddress) -> Result<bool, Error> {
+	fn check(&self, public: &Public, document: &ServerKeyId) -> Result<bool, Error> {
 		let mut contract = self.contract.lock();
 		if !contract.is_some() {
 			*contract = self.client.registry_address(ACL_CHECKER_CONTRACT_REGISTRY_NAME.to_owned())
@@ -74,19 +74,19 @@ impl AclStorage for OnChainAclStorage {
 pub mod tests {
 	use std::collections::{HashMap, HashSet};
 	use parking_lot::RwLock;
-	use types::all::{Error, DocumentAddress, Public};
+	use types::all::{Error, ServerKeyId, Public};
 	use super::AclStorage;
 
 	#[derive(Default, Debug)]
 	/// Dummy ACL storage implementation
 	pub struct DummyAclStorage {
-		prohibited: RwLock<HashMap<Public, HashSet<DocumentAddress>>>,
+		prohibited: RwLock<HashMap<Public, HashSet<ServerKeyId>>>,
 	}
 
 	impl DummyAclStorage {
 		#[cfg(test)]
 		/// Prohibit given requestor access to given document
-		pub fn prohibit(&self, public: Public, document: DocumentAddress) {
+		pub fn prohibit(&self, public: Public, document: ServerKeyId) {
 			self.prohibited.write()
 				.entry(public)
 				.or_insert_with(Default::default)
@@ -95,7 +95,7 @@ pub mod tests {
 	}
 
 	impl AclStorage for DummyAclStorage {
-		fn check(&self, public: &Public, document: &DocumentAddress) -> Result<bool, Error> {
+		fn check(&self, public: &Public, document: &ServerKeyId) -> Result<bool, Error> {
 			Ok(self.prohibited.read()
 				.get(public)
 				.map(|docs| !docs.contains(document))

secret_store/src/http_listener.rs

@@ -21,14 +21,23 @@ use hyper::method::Method as HttpMethod;
 use hyper::status::StatusCode as HttpStatusCode;
 use hyper::server::{Server as HttpServer, Request as HttpRequest, Response as HttpResponse, Handler as HttpHandler,
 	Listening as HttpListening};
+use serde::Serialize;
 use serde_json;
 use url::percent_encoding::percent_decode;
 
-use traits::KeyServer;
+use traits::{ServerKeyGenerator, DocumentKeyServer, MessageSigner, KeyServer};
-use serialization::{SerializableDocumentEncryptedKeyShadow, SerializableBytes};
+use serialization::{SerializableEncryptedDocumentKeyShadow, SerializableBytes, SerializablePublic};
-use types::all::{Error, NodeAddress, RequestSignature, DocumentAddress, DocumentEncryptedKey, DocumentEncryptedKeyShadow};
+use types::all::{Error, Public, MessageHash, EncryptedMessageSignature, NodeAddress, RequestSignature, ServerKeyId,
+	EncryptedDocumentKey, EncryptedDocumentKeyShadow};
+
+/// Key server http-requests listener. Available requests:
+/// To generate server key:							POST		/shadow/{server_key_id}/{signature}/{threshold}
+/// To store pregenerated encrypted document key: 	POST		/shadow/{server_key_id}/{signature}/{common_point}/{encrypted_key} 
+/// To generate server && document key:				POST		/{server_key_id}/{signature}/{threshold} 
+/// To get document key:							GET			/{server_key_id}/{signature}
+/// To get document key shadow:						GET			/shadow/{server_key_id}/{signature} 
+/// To sign message with server key:				GET			/{server_key_id}/{signature}/{message_hash}
 
-/// Key server http-requests listener
 pub struct KeyServerHttpListener<T: KeyServer + 'static> {
 	_http_server: HttpListening,
 	handler: Arc<KeyServerSharedHttpHandler<T>>,
@@ -39,12 +48,18 @@ pub struct KeyServerHttpListener<T: KeyServer + 'static> {
 enum Request {
 	/// Invalid request
 	Invalid,
+	/// Generate server key.
+	GenerateServerKey(ServerKeyId, RequestSignature, usize),
+	/// Store document key.
+	StoreDocumentKey(ServerKeyId, RequestSignature, Public, Public),
 	/// Generate encryption key.
-	GenerateDocumentKey(DocumentAddress, RequestSignature, usize),
+	GenerateDocumentKey(ServerKeyId, RequestSignature, usize),
 	/// Request encryption key of given document for given requestor.
-	GetDocumentKey(DocumentAddress, RequestSignature),
+	GetDocumentKey(ServerKeyId, RequestSignature),
 	/// Request shadow of encryption key of given document for given requestor.
-	GetDocumentKeyShadow(DocumentAddress, RequestSignature),
+	GetDocumentKeyShadow(ServerKeyId, RequestSignature),
+	/// Sign message.
+	SignMessage(ServerKeyId, RequestSignature, MessageHash),
 }
 
 /// Cloneable http handler
@@ -78,17 +93,35 @@ impl<T> KeyServerHttpListener<T> where T: KeyServer + 'static {
 	}
 }
 
-impl<T> KeyServer for KeyServerHttpListener<T> where T: KeyServer + 'static {
+impl<T> KeyServer for KeyServerHttpListener<T> where T: KeyServer + 'static {}
-	fn generate_document_key(&self, signature: &RequestSignature, document: &DocumentAddress, threshold: usize) -> Result<DocumentEncryptedKey, Error> {
+
-		self.handler.key_server.generate_document_key(signature, document, threshold)
+impl<T> ServerKeyGenerator for KeyServerHttpListener<T> where T: KeyServer + 'static {
+	fn generate_key(&self, key_id: &ServerKeyId, signature: &RequestSignature, threshold: usize) -> Result<Public, Error> {
+		self.handler.key_server.generate_key(key_id, signature, threshold)
+	}
+}
+
+impl<T> DocumentKeyServer for KeyServerHttpListener<T> where T: KeyServer + 'static {
+	fn store_document_key(&self, key_id: &ServerKeyId, signature: &RequestSignature, common_point: Public, encrypted_document_key: Public) -> Result<(), Error> {
+		self.handler.key_server.store_document_key(key_id, signature, common_point, encrypted_document_key)
 	}
 
-	fn document_key(&self, signature: &RequestSignature, document: &DocumentAddress) -> Result<DocumentEncryptedKey, Error> {
+	fn generate_document_key(&self, key_id: &ServerKeyId, signature: &RequestSignature, threshold: usize) -> Result<EncryptedDocumentKey, Error> {
-		self.handler.key_server.document_key(signature, document)
+		self.handler.key_server.generate_document_key(key_id, signature, threshold)
 	}
 
-	fn document_key_shadow(&self, signature: &RequestSignature, document: &DocumentAddress) -> Result<DocumentEncryptedKeyShadow, Error> {
+	fn restore_document_key(&self, key_id: &ServerKeyId, signature: &RequestSignature) -> Result<EncryptedDocumentKey, Error> {
-		self.handler.key_server.document_key_shadow(signature, document)
+		self.handler.key_server.restore_document_key(key_id, signature)
+	}
+
+	fn restore_document_key_shadow(&self, key_id: &ServerKeyId, signature: &RequestSignature) -> Result<EncryptedDocumentKeyShadow, Error> {
+		self.handler.key_server.restore_document_key_shadow(key_id, signature)
+	}
+}
+
+impl <T> MessageSigner for KeyServerHttpListener<T> where T: KeyServer + 'static {
+	fn sign_message(&self, key_id: &ServerKeyId, signature: &RequestSignature, message: MessageHash) -> Result<EncryptedMessageSignature, Error> {
+		self.handler.key_server.sign_message(key_id, signature, message)
 	}
 }
 
@@ -111,47 +144,47 @@ impl<T> HttpHandler for KeyServerHttpHandler<T> where T: KeyServer + 'static {
 		let req_uri = req.uri.clone();
 		match &req_uri {
 			&RequestUri::AbsolutePath(ref path) => match parse_request(&req_method, &path) {
+				Request::GenerateServerKey(document, signature, threshold) => {
+					return_server_public_key(req, res, self.handler.key_server.generate_key(&document, &signature, threshold)
+						.map_err(|err| {
+							warn!(target: "secretstore", "GenerateServerKey request {} has failed with: {}", req_uri, err);
+							err
+						}));
+				},
+				Request::StoreDocumentKey(document, signature, common_point, encrypted_document_key) => {
+					return_empty(req, res, self.handler.key_server.store_document_key(&document, &signature, common_point, encrypted_document_key)
+						.map_err(|err| {
+							warn!(target: "secretstore", "StoreDocumentKey request {} has failed with: {}", req_uri, err);
+							err
+						}));
+				},
 				Request::GenerateDocumentKey(document, signature, threshold) => {
-					return_document_key(req, res, self.handler.key_server.generate_document_key(&signature, &document, threshold)
+					return_document_key(req, res, self.handler.key_server.generate_document_key(&document, &signature, threshold)
 						.map_err(|err| {
 							warn!(target: "secretstore", "GenerateDocumentKey request {} has failed with: {}", req_uri, err);
 							err
 						}));
 				},
 				Request::GetDocumentKey(document, signature) => {
-					return_document_key(req, res, self.handler.key_server.document_key(&signature, &document)
+					return_document_key(req, res, self.handler.key_server.restore_document_key(&document, &signature)
 						.map_err(|err| {
 							warn!(target: "secretstore", "GetDocumentKey request {} has failed with: {}", req_uri, err);
 							err
 						}));
 				},
 				Request::GetDocumentKeyShadow(document, signature) => {
-					match self.handler.key_server.document_key_shadow(&signature, &document)
+					return_document_key_shadow(req, res, self.handler.key_server.restore_document_key_shadow(&document, &signature)
 						.map_err(|err| {
 							warn!(target: "secretstore", "GetDocumentKeyShadow request {} has failed with: {}", req_uri, err);
 							err
-						}) {
+						}));
-						Ok(document_key_shadow) => {
+				},
-							let document_key_shadow = SerializableDocumentEncryptedKeyShadow {
+				Request::SignMessage(document, signature, message_hash) => {
-								decrypted_secret: document_key_shadow.decrypted_secret.into(),
+					return_message_signature(req, res, self.handler.key_server.sign_message(&document, &signature, message_hash)
-								common_point: document_key_shadow.common_point.expect("always filled when requesting document_key_shadow; qed").into(),
+						.map_err(|err| {
-								decrypt_shadows: document_key_shadow.decrypt_shadows.expect("always filled when requesting document_key_shadow; qed").into_iter().map(Into::into).collect(),
+							warn!(target: "secretstore", "SignMessage request {} has failed with: {}", req_uri, err);
-							};
+							err
-							match serde_json::to_vec(&document_key_shadow) {
+						}));
-								Ok(document_key) => {
-									res.headers_mut().set(header::ContentType::json());
-									if let Err(err) = res.send(&document_key) {
-										// nothing to do, but to log an error
-										warn!(target: "secretstore", "response to request {} has failed with: {}", req.uri, err);
-									}
-								},
-								Err(err) => {
-									warn!(target: "secretstore", "response to request {} has failed with: {}", req.uri, err);
-								}
-							}
-						},
-						Err(err) => return_error(res, err),
-					}
 				},
 				Request::Invalid => {
 					warn!(target: "secretstore", "Ignoring invalid {}-request {}", req_method, req_uri);
@@ -166,17 +199,45 @@ impl<T> HttpHandler for KeyServerHttpHandler<T> where T: KeyServer + 'static {
 	}
 }
 
-fn return_document_key(req: HttpRequest, mut res: HttpResponse, document_key: Result<DocumentEncryptedKey, Error>) {
+fn return_empty(req: HttpRequest, res: HttpResponse, empty: Result<(), Error>) {
-	let document_key = document_key.
+	return_bytes::<i32>(req, res, empty.map(|_| None))
-		and_then(|k| serde_json::to_vec(&SerializableBytes(k)).map_err(|e| Error::Serde(e.to_string())));
+}
-	match document_key {
+
-		Ok(document_key) => {
+fn return_server_public_key(req: HttpRequest, res: HttpResponse, server_public: Result<Public, Error>) {
-			res.headers_mut().set(header::ContentType::plaintext());
+	return_bytes(req, res, server_public.map(|k| Some(SerializablePublic(k))))
-			if let Err(err) = res.send(&document_key) {
+}
-				// nothing to do, but to log an error
+
+fn return_message_signature(req: HttpRequest, res: HttpResponse, signature: Result<EncryptedDocumentKey, Error>) {
+	return_bytes(req, res, signature.map(|s| Some(SerializableBytes(s))))
+}
+
+fn return_document_key(req: HttpRequest, res: HttpResponse, document_key: Result<EncryptedDocumentKey, Error>) {
+	return_bytes(req, res, document_key.map(|k| Some(SerializableBytes(k))))
+}
+
+fn return_document_key_shadow(req: HttpRequest, res: HttpResponse, document_key_shadow: Result<EncryptedDocumentKeyShadow, Error>) {
+	return_bytes(req, res, document_key_shadow.map(|k| Some(SerializableEncryptedDocumentKeyShadow {
+		decrypted_secret: k.decrypted_secret.into(),
+		common_point: k.common_point.expect("always filled when requesting document_key_shadow; qed").into(),
+		decrypt_shadows: k.decrypt_shadows.expect("always filled when requesting document_key_shadow; qed").into_iter().map(Into::into).collect(),
+	})))
+}
+
+fn return_bytes<T: Serialize>(req: HttpRequest, mut res: HttpResponse, result: Result<Option<T>, Error>) {
+	match result {
+		Ok(Some(result)) => match serde_json::to_vec(&result) {
+			Ok(result) => {
+				res.headers_mut().set(header::ContentType::json());
+				if let Err(err) = res.send(&result) {
+					// nothing to do, but to log an error
+					warn!(target: "secretstore", "response to request {} has failed with: {}", req.uri, err);
+				}
+			},
+			Err(err) => {
 				warn!(target: "secretstore", "response to request {} has failed with: {}", req.uri, err);
 			}
 		},
+		Ok(None) => *res.status_mut() = HttpStatusCode::Ok,
 		Err(err) => return_error(res, err),
 	}
 }
@@ -190,6 +251,13 @@ fn return_error(mut res: HttpResponse, err: Error) {
 		Error::Database(_) => *res.status_mut() = HttpStatusCode::InternalServerError,
 		Error::Internal(_) => *res.status_mut() = HttpStatusCode::InternalServerError,
 	}
+
+	// return error text. ignore errors when returning error
+	let error_text = format!("\"{}\"", err);
+	if let Ok(error_text) = serde_json::to_vec(&error_text) {
+		res.headers_mut().set(header::ContentType::json());
+		let _ = res.send(&error_text);
+	}
 }
 
 fn parse_request(method: &HttpMethod, uri_path: &str) -> Request {
@@ -202,24 +270,39 @@ fn parse_request(method: &HttpMethod, uri_path: &str) -> Request {
 	if path.len() == 0 {
 		return Request::Invalid;
 	}
-	let (args_prefix, args_offset) = if &path[0] == "shadow" {
-		("shadow", 1)
-	} else {
-		("", 0)
-	};
 
-	if path.len() < 2 + args_offset || path[args_offset].is_empty() || path[args_offset + 1].is_empty() {
+	let (is_shadow_request, args_offset) = if &path[0] == "shadow" { (true, 1) } else { (false, 0) };
+	let args_count = path.len() - args_offset;
+	if args_count < 2 || path[args_offset].is_empty() || path[args_offset + 1].is_empty() {
 		return Request::Invalid;
 	}
 
-	let args_len = path.len();
+	let document = match path[args_offset].parse() {
-	let document = path[args_offset].parse();
+		Ok(document) => document,
-	let signature = path[args_offset + 1].parse();
+		_ => return Request::Invalid,
-	let threshold = (if args_len > args_offset + 2 { &path[args_offset + 2] } else { "" }).parse();
+	};
-	match (args_prefix, args_len, method, document, signature, threshold) {
+	let signature = match path[args_offset + 1].parse() {
-		("",		3, &HttpMethod::Post, Ok(document), Ok(signature), Ok(threshold)) => Request::GenerateDocumentKey(document, signature, threshold),
+		Ok(signature) => signature,
-		("",		2, &HttpMethod::Get, Ok(document), Ok(signature), _) => Request::GetDocumentKey(document, signature),
+		_ => return Request::Invalid,
-		("shadow",	3, &HttpMethod::Get, Ok(document), Ok(signature), _) => Request::GetDocumentKeyShadow(document, signature),
+	};
+
+	let threshold = path.get(args_offset + 2).map(|v| v.parse());
+	let message_hash = path.get(args_offset + 2).map(|v| v.parse());
+	let common_point = path.get(args_offset + 2).map(|v| v.parse());
+	let encrypted_key = path.get(args_offset + 3).map(|v| v.parse());
+	match (is_shadow_request, args_count, method, threshold, message_hash, common_point, encrypted_key) {
+		(true, 3, &HttpMethod::Post, Some(Ok(threshold)), _, _, _) =>
+			Request::GenerateServerKey(document, signature, threshold),
+		(true, 4, &HttpMethod::Post, _, _, Some(Ok(common_point)), Some(Ok(encrypted_key))) =>
+			Request::StoreDocumentKey(document, signature, common_point, encrypted_key),
+		(false, 3, &HttpMethod::Post, Some(Ok(threshold)), _, _, _) =>
+			Request::GenerateDocumentKey(document, signature, threshold),
+		(false, 2, &HttpMethod::Get, _, _, _, _) =>
+			Request::GetDocumentKey(document, signature),
+		(true, 2, &HttpMethod::Get, _, _, _, _) =>
+			Request::GetDocumentKeyShadow(document, signature),
+		(false, 3, &HttpMethod::Get, _, Some(Ok(message_hash)), _, _) =>
+			Request::SignMessage(document, signature, message_hash),
 		_ => Request::Invalid,
 	}
 }
@@ -241,19 +324,49 @@ mod tests {
 
 	#[test]
 	fn parse_request_successful() {
+		// POST		/shadow/{server_key_id}/{signature}/{threshold}						=> generate server key
+		assert_eq!(parse_request(&HttpMethod::Post, "/shadow/0000000000000000000000000000000000000000000000000000000000000001/a199fb39e11eefb61c78a4074a53c0d4424600a3e74aad4fb9d93a26c30d067e1d4d29936de0c73f19827394a1dd049480a0d581aee7ae7546968da7d3d1c2fd01/2"),
+			Request::GenerateServerKey("0000000000000000000000000000000000000000000000000000000000000001".into(),
+				"a199fb39e11eefb61c78a4074a53c0d4424600a3e74aad4fb9d93a26c30d067e1d4d29936de0c73f19827394a1dd049480a0d581aee7ae7546968da7d3d1c2fd01".parse().unwrap(),
+				2));
+		// POST		/shadow/{server_key_id}/{signature}/{common_point}/{encrypted_key}	=> store encrypted document key
+		assert_eq!(parse_request(&HttpMethod::Post, "/shadow/0000000000000000000000000000000000000000000000000000000000000001/a199fb39e11eefb61c78a4074a53c0d4424600a3e74aad4fb9d93a26c30d067e1d4d29936de0c73f19827394a1dd049480a0d581aee7ae7546968da7d3d1c2fd01/b486d3840218837b035c66196ecb15e6b067ca20101e11bd5e626288ab6806ecc70b8307012626bd512bad1559112d11d21025cef48cc7a1d2f3976da08f36c8/1395568277679f7f583ab7c0992da35f26cde57149ee70e524e49bdae62db3e18eb96122501e7cbb798b784395d7bb5a499edead0706638ad056d886e56cf8fb"),
+			Request::StoreDocumentKey("0000000000000000000000000000000000000000000000000000000000000001".into(),
+				"a199fb39e11eefb61c78a4074a53c0d4424600a3e74aad4fb9d93a26c30d067e1d4d29936de0c73f19827394a1dd049480a0d581aee7ae7546968da7d3d1c2fd01".parse().unwrap(),
+				"b486d3840218837b035c66196ecb15e6b067ca20101e11bd5e626288ab6806ecc70b8307012626bd512bad1559112d11d21025cef48cc7a1d2f3976da08f36c8".parse().unwrap(),
+				"1395568277679f7f583ab7c0992da35f26cde57149ee70e524e49bdae62db3e18eb96122501e7cbb798b784395d7bb5a499edead0706638ad056d886e56cf8fb".parse().unwrap()));
+		// POST		/{server_key_id}/{signature}/{threshold}							=> generate server && document key
+		assert_eq!(parse_request(&HttpMethod::Post, "/0000000000000000000000000000000000000000000000000000000000000001/a199fb39e11eefb61c78a4074a53c0d4424600a3e74aad4fb9d93a26c30d067e1d4d29936de0c73f19827394a1dd049480a0d581aee7ae7546968da7d3d1c2fd01/2"),
+			Request::GenerateDocumentKey("0000000000000000000000000000000000000000000000000000000000000001".into(),
+				"a199fb39e11eefb61c78a4074a53c0d4424600a3e74aad4fb9d93a26c30d067e1d4d29936de0c73f19827394a1dd049480a0d581aee7ae7546968da7d3d1c2fd01".parse().unwrap(),
+				2));
+		// GET		/{server_key_id}/{signature}										=> get document key
 		assert_eq!(parse_request(&HttpMethod::Get, "/0000000000000000000000000000000000000000000000000000000000000001/a199fb39e11eefb61c78a4074a53c0d4424600a3e74aad4fb9d93a26c30d067e1d4d29936de0c73f19827394a1dd049480a0d581aee7ae7546968da7d3d1c2fd01"),
 			Request::GetDocumentKey("0000000000000000000000000000000000000000000000000000000000000001".into(),
 				"a199fb39e11eefb61c78a4074a53c0d4424600a3e74aad4fb9d93a26c30d067e1d4d29936de0c73f19827394a1dd049480a0d581aee7ae7546968da7d3d1c2fd01".parse().unwrap()));
 		assert_eq!(parse_request(&HttpMethod::Get, "/%30000000000000000000000000000000000000000000000000000000000000001/a199fb39e11eefb61c78a4074a53c0d4424600a3e74aad4fb9d93a26c30d067e1d4d29936de0c73f19827394a1dd049480a0d581aee7ae7546968da7d3d1c2fd01"),
 			Request::GetDocumentKey("0000000000000000000000000000000000000000000000000000000000000001".into(),
 				"a199fb39e11eefb61c78a4074a53c0d4424600a3e74aad4fb9d93a26c30d067e1d4d29936de0c73f19827394a1dd049480a0d581aee7ae7546968da7d3d1c2fd01".parse().unwrap()));
+		// GET		/shadow/{server_key_id}/{signature}									=> get document key shadow
+		assert_eq!(parse_request(&HttpMethod::Get, "/shadow/0000000000000000000000000000000000000000000000000000000000000001/a199fb39e11eefb61c78a4074a53c0d4424600a3e74aad4fb9d93a26c30d067e1d4d29936de0c73f19827394a1dd049480a0d581aee7ae7546968da7d3d1c2fd01"),
+			Request::GetDocumentKeyShadow("0000000000000000000000000000000000000000000000000000000000000001".into(),
+				"a199fb39e11eefb61c78a4074a53c0d4424600a3e74aad4fb9d93a26c30d067e1d4d29936de0c73f19827394a1dd049480a0d581aee7ae7546968da7d3d1c2fd01".parse().unwrap()));
+		// GET		/{server_key_id}/{signature}/{message_hash}							=> sign message with server key
+		assert_eq!(parse_request(&HttpMethod::Get, "/0000000000000000000000000000000000000000000000000000000000000001/a199fb39e11eefb61c78a4074a53c0d4424600a3e74aad4fb9d93a26c30d067e1d4d29936de0c73f19827394a1dd049480a0d581aee7ae7546968da7d3d1c2fd01/281b6bf43cb86d0dc7b98e1b7def4a80f3ce16d28d2308f934f116767306f06c"),
+			Request::SignMessage("0000000000000000000000000000000000000000000000000000000000000001".into(),
+				"a199fb39e11eefb61c78a4074a53c0d4424600a3e74aad4fb9d93a26c30d067e1d4d29936de0c73f19827394a1dd049480a0d581aee7ae7546968da7d3d1c2fd01".parse().unwrap(),
+				"281b6bf43cb86d0dc7b98e1b7def4a80f3ce16d28d2308f934f116767306f06c".parse().unwrap()));
 	}
 
 	#[test]
 	fn parse_request_failed() {
+		assert_eq!(parse_request(&HttpMethod::Get, ""), Request::Invalid);
+		assert_eq!(parse_request(&HttpMethod::Get, "/shadow"), Request::Invalid);
+		assert_eq!(parse_request(&HttpMethod::Get, "///2"), Request::Invalid);
+		assert_eq!(parse_request(&HttpMethod::Get, "/shadow///2"), Request::Invalid);
 		assert_eq!(parse_request(&HttpMethod::Get, "/0000000000000000000000000000000000000000000000000000000000000001"), Request::Invalid);
 		assert_eq!(parse_request(&HttpMethod::Get, "/0000000000000000000000000000000000000000000000000000000000000001/"), Request::Invalid);
 		assert_eq!(parse_request(&HttpMethod::Get, "/a/b"), Request::Invalid);
-		assert_eq!(parse_request(&HttpMethod::Get, "/0000000000000000000000000000000000000000000000000000000000000001/a199fb39e11eefb61c78a4074a53c0d4424600a3e74aad4fb9d93a26c30d067e1d4d29936de0c73f19827394a1dd049480a0d581aee7ae7546968da7d3d1c2fd01/0000000000000000000000000000000000000000000000000000000000000002"), Request::Invalid);
+		assert_eq!(parse_request(&HttpMethod::Get, "/0000000000000000000000000000000000000000000000000000000000000001/a199fb39e11eefb61c78a4074a53c0d4424600a3e74aad4fb9d93a26c30d067e1d4d29936de0c73f19827394a1dd049480a0d581aee7ae7546968da7d3d1c2fd01/0000000000000000000000000000000000000000000000000000000000000002/0000000000000000000000000000000000000000000000000000000000000002"), Request::Invalid);
 	}
 }

secret_store/src/key_server.rs

@@ -24,9 +24,10 @@ use ethcrypto;
 use ethkey;
 use super::acl_storage::AclStorage;
 use super::key_storage::KeyStorage;
-use key_server_cluster::ClusterCore;
+use key_server_cluster::{math, ClusterCore};
-use traits::KeyServer;
+use traits::{ServerKeyGenerator, DocumentKeyServer, MessageSigner, KeyServer};
-use types::all::{Error, RequestSignature, DocumentAddress, DocumentEncryptedKey, DocumentEncryptedKeyShadow, ClusterConfiguration};
+use types::all::{Error, Public, RequestSignature, ServerKeyId, EncryptedDocumentKey, EncryptedDocumentKeyShadow,
+	ClusterConfiguration, MessageHash, EncryptedMessageSignature};
 use key_server_cluster::{ClusterClient, ClusterConfiguration as NetClusterConfiguration};
 
 /// Secret store key server implementation
@@ -56,15 +57,41 @@ impl KeyServerImpl {
 	}
 }
 
-impl KeyServer for KeyServerImpl {
+impl KeyServer for KeyServerImpl {}
-	fn generate_document_key(&self, signature: &RequestSignature, document: &DocumentAddress, threshold: usize) -> Result<DocumentEncryptedKey, Error> {
+
+impl ServerKeyGenerator for KeyServerImpl {
+	fn generate_key(&self, key_id: &ServerKeyId, signature: &RequestSignature, threshold: usize) -> Result<Public, Error> {
 		// recover requestor' public key from signature
-		let public = ethkey::recover(signature, document)
+		let public = ethkey::recover(signature, key_id)
 			.map_err(|_| Error::BadSignature)?;
 
-		// generate document key
+		// generate server key
-		let encryption_session = self.data.lock().cluster.new_encryption_session(document.clone(), threshold)?;
+		let generation_session = self.data.lock().cluster.new_generation_session(key_id.clone(), public, threshold)?;
-		let document_key = encryption_session.wait(None)?;
+		generation_session.wait(None).map_err(Into::into)
+	}
+}
+
+impl DocumentKeyServer for KeyServerImpl {
+	fn store_document_key(&self, key_id: &ServerKeyId, signature: &RequestSignature, common_point: Public, encrypted_document_key: Public) -> Result<(), Error> {
+		// store encrypted key
+		let encryption_session = self.data.lock().cluster.new_encryption_session(key_id.clone(), signature.clone(), common_point, encrypted_document_key)?;
+		encryption_session.wait(None).map_err(Into::into)
+	}
+
+	fn generate_document_key(&self, key_id: &ServerKeyId, signature: &RequestSignature, threshold: usize) -> Result<EncryptedDocumentKey, Error> {
+		// recover requestor' public key from signature
+		let public = ethkey::recover(signature, key_id)
+			.map_err(|_| Error::BadSignature)?;
+
+		// generate server key
+		let server_key = self.generate_key(key_id, signature, threshold)?;
+
+		// generate random document key
+		let document_key = math::generate_random_point()?;
+		let encrypted_document_key = math::encrypt_secret(&document_key, &server_key)?;
+
+		// store document key in the storage
+		self.store_document_key(key_id, signature, encrypted_document_key.common_point, encrypted_document_key.encrypted_point)?;
 
 		// encrypt document key with requestor public key
 		let document_key = ethcrypto::ecies::encrypt(&public, &ethcrypto::DEFAULT_MAC, &document_key)
@@ -72,14 +99,13 @@ impl KeyServer for KeyServerImpl {
 		Ok(document_key)
 	}
 
-	fn document_key(&self, signature: &RequestSignature, document: &DocumentAddress) -> Result<DocumentEncryptedKey, Error> {
+	fn restore_document_key(&self, key_id: &ServerKeyId, signature: &RequestSignature) -> Result<EncryptedDocumentKey, Error> {
 		// recover requestor' public key from signature
-		let public = ethkey::recover(signature, document)
+		let public = ethkey::recover(signature, key_id)
 			.map_err(|_| Error::BadSignature)?;
 
-
 		// decrypt document key
-		let decryption_session = self.data.lock().cluster.new_decryption_session(document.clone(), signature.clone(), false)?;
+		let decryption_session = self.data.lock().cluster.new_decryption_session(key_id.clone(), signature.clone(), false)?;
 		let document_key = decryption_session.wait()?.decrypted_secret;
 
 		// encrypt document key with requestor public key
@@ -88,12 +114,34 @@ impl KeyServer for KeyServerImpl {
 		Ok(document_key)
 	}
 
-	fn document_key_shadow(&self, signature: &RequestSignature, document: &DocumentAddress) -> Result<DocumentEncryptedKeyShadow, Error> {
+	fn restore_document_key_shadow(&self, key_id: &ServerKeyId, signature: &RequestSignature) -> Result<EncryptedDocumentKeyShadow, Error> {
-		let decryption_session = self.data.lock().cluster.new_decryption_session(document.clone(), signature.clone(), true)?;
+		let decryption_session = self.data.lock().cluster.new_decryption_session(key_id.clone(), signature.clone(), true)?;
 		decryption_session.wait().map_err(Into::into)
 	}
 }
 
+impl MessageSigner for KeyServerImpl {
+	fn sign_message(&self, key_id: &ServerKeyId, signature: &RequestSignature, message: MessageHash) -> Result<EncryptedMessageSignature, Error> {
+		// recover requestor' public key from signature
+		let public = ethkey::recover(signature, key_id)
+			.map_err(|_| Error::BadSignature)?;
+
+		// sign message
+		let signing_session = self.data.lock().cluster.new_signing_session(key_id.clone(), signature.clone(), message)?;
+		let message_signature = signing_session.wait()?;
+
+		// compose two message signature components into single one
+		let mut combined_signature = [0; 64];
+		combined_signature[..32].clone_from_slice(&**message_signature.0);
+		combined_signature[32..].clone_from_slice(&**message_signature.1);
+
+		// encrypt combined signature with requestor public key
+		let message_signature = ethcrypto::ecies::encrypt(&public, &ethcrypto::DEFAULT_MAC, &combined_signature)
+			.map_err(|err| Error::Internal(format!("Error encrypting message signature: {}", err)))?;
+		Ok(message_signature)
+	}
+}
+
 impl KeyServerCore {
 	pub fn new(config: &ClusterConfiguration, acl_storage: Arc<AclStorage>, key_storage: Arc<KeyStorage>) -> Result<Self, Error> {
 		let config = NetClusterConfiguration {
@@ -146,24 +194,46 @@ pub mod tests {
 	use std::time;
 	use std::sync::Arc;
 	use ethcrypto;
-	use ethkey::{self, Random, Generator};
+	use ethkey::{self, Secret, Random, Generator};
 	use acl_storage::tests::DummyAclStorage;
 	use key_storage::tests::DummyKeyStorage;
-	use types::all::{Error, ClusterConfiguration, NodeAddress, RequestSignature, DocumentAddress, DocumentEncryptedKey, DocumentEncryptedKeyShadow};
+	use key_server_cluster::math;
-	use super::{KeyServer, KeyServerImpl};
+	use util::H256;
+	use types::all::{Error, Public, ClusterConfiguration, NodeAddress, RequestSignature, ServerKeyId,
+		EncryptedDocumentKey, EncryptedDocumentKeyShadow, MessageHash, EncryptedMessageSignature};
+	use traits::{ServerKeyGenerator, DocumentKeyServer, MessageSigner, KeyServer};
+	use super::KeyServerImpl;
 
 	pub struct DummyKeyServer;
 
-	impl KeyServer for DummyKeyServer {
+	impl KeyServer for DummyKeyServer {}
-		fn generate_document_key(&self, _signature: &RequestSignature, _document: &DocumentAddress, _threshold: usize) -> Result<DocumentEncryptedKey, Error> {
+
+	impl ServerKeyGenerator for DummyKeyServer {
+		fn generate_key(&self, _key_id: &ServerKeyId, _signature: &RequestSignature, _threshold: usize) -> Result<Public, Error> {
+			unimplemented!()
+		}
+	}
+
+	impl DocumentKeyServer for DummyKeyServer {
+		fn store_document_key(&self, _key_id: &ServerKeyId, _signature: &RequestSignature, _common_point: Public, _encrypted_document_key: Public) -> Result<(), Error> {
 			unimplemented!()
 		}
 
-		fn document_key(&self, _signature: &RequestSignature, _document: &DocumentAddress) -> Result<DocumentEncryptedKey, Error> {
+		fn generate_document_key(&self, _key_id: &ServerKeyId, _signature: &RequestSignature, _threshold: usize) -> Result<EncryptedDocumentKey, Error> {
 			unimplemented!()
 		}
 
-		fn document_key_shadow(&self, _signature: &RequestSignature, _document: &DocumentAddress) -> Result<DocumentEncryptedKeyShadow, Error> {
+		fn restore_document_key(&self, _key_id: &ServerKeyId, _signature: &RequestSignature) -> Result<EncryptedDocumentKey, Error> {
+			unimplemented!()
+		}
+
+		fn restore_document_key_shadow(&self, _key_id: &ServerKeyId, _signature: &RequestSignature) -> Result<EncryptedDocumentKeyShadow, Error> {
+			unimplemented!()
+		}
+	}
+
+	impl MessageSigner for DummyKeyServer {
+		fn sign_message(&self, _key_id: &ServerKeyId, _signature: &RequestSignature, _message: MessageHash) -> Result<EncryptedMessageSignature, Error> {
 			unimplemented!()
 		}
 	}
@@ -228,12 +298,12 @@ pub mod tests {
 		let document = Random.generate().unwrap().secret().clone();
 		let secret = Random.generate().unwrap().secret().clone();
 		let signature = ethkey::sign(&secret, &document).unwrap();
-		let generated_key = key_servers[0].generate_document_key(&signature, &document, threshold).unwrap();
+		let generated_key = key_servers[0].generate_document_key(&document, &signature, threshold).unwrap();
 		let generated_key = ethcrypto::ecies::decrypt(&secret, &ethcrypto::DEFAULT_MAC, &generated_key).unwrap();
 
 		// now let's try to retrieve key back
 		for key_server in key_servers.iter() {
-			let retrieved_key = key_server.document_key(&signature, &document).unwrap();
+			let retrieved_key = key_server.restore_document_key(&document, &signature).unwrap();
 			let retrieved_key = ethcrypto::ecies::decrypt(&secret, &ethcrypto::DEFAULT_MAC, &retrieved_key).unwrap();
 			assert_eq!(retrieved_key, generated_key);
 		}
@@ -250,15 +320,70 @@ pub mod tests {
 			let document = Random.generate().unwrap().secret().clone();
 			let secret = Random.generate().unwrap().secret().clone();
 			let signature = ethkey::sign(&secret, &document).unwrap();
-			let generated_key = key_servers[0].generate_document_key(&signature, &document, *threshold).unwrap();
+			let generated_key = key_servers[0].generate_document_key(&document, &signature, *threshold).unwrap();
 			let generated_key = ethcrypto::ecies::decrypt(&secret, &ethcrypto::DEFAULT_MAC, &generated_key).unwrap();
 
 			// now let's try to retrieve key back
 			for key_server in key_servers.iter() {
-				let retrieved_key = key_server.document_key(&signature, &document).unwrap();
+				let retrieved_key = key_server.restore_document_key(&document, &signature).unwrap();
 				let retrieved_key = ethcrypto::ecies::decrypt(&secret, &ethcrypto::DEFAULT_MAC, &retrieved_key).unwrap();
 				assert_eq!(retrieved_key, generated_key);
 			}
 		}
 	}
+
+	#[test]
+	fn server_key_generation_and_storing_document_key_works_over_network_with_3_nodes() {
+		//::logger::init_log();
+		let key_servers = make_key_servers(6090, 3);
+
+		let test_cases = [0, 1, 2];
+		for threshold in &test_cases {
+			// generate server key
+			let server_key_id = Random.generate().unwrap().secret().clone();
+			let requestor_secret = Random.generate().unwrap().secret().clone();
+			let signature = ethkey::sign(&requestor_secret, &server_key_id).unwrap();
+			let server_public = key_servers[0].generate_key(&server_key_id, &signature, *threshold).unwrap();
+
+			// generate document key (this is done by KS client so that document key is unknown to any KS)
+			let generated_key = Random.generate().unwrap().public().clone();
+			let encrypted_document_key = math::encrypt_secret(&generated_key, &server_public).unwrap();
+
+			// store document key
+			key_servers[0].store_document_key(&server_key_id, &signature, encrypted_document_key.common_point, encrypted_document_key.encrypted_point).unwrap();
+
+			// now let's try to retrieve key back
+			for key_server in key_servers.iter() {
+				let retrieved_key = key_server.restore_document_key(&server_key_id, &signature).unwrap();
+				let retrieved_key = ethcrypto::ecies::decrypt(&requestor_secret, &ethcrypto::DEFAULT_MAC, &retrieved_key).unwrap();
+				let retrieved_key = Public::from_slice(&retrieved_key);
+				assert_eq!(retrieved_key, generated_key);
+			}
+		}
+	}
+
+	#[test]
+	fn server_key_generation_and_message_signing_works_over_network_with_3_nodes() {
+		//::logger::init_log();
+		let key_servers = make_key_servers(6100, 3);
+
+		let test_cases = [0, 1, 2];
+		for threshold in &test_cases {
+			// generate server key
+			let server_key_id = Random.generate().unwrap().secret().clone();
+			let requestor_secret = Random.generate().unwrap().secret().clone();
+			let signature = ethkey::sign(&requestor_secret, &server_key_id).unwrap();
+			let server_public = key_servers[0].generate_key(&server_key_id, &signature, *threshold).unwrap();
+
+			// sign message
+			let message_hash = H256::from(42);
+			let combined_signature = key_servers[0].sign_message(&server_key_id, &signature, message_hash.clone()).unwrap();
+			let combined_signature = ethcrypto::ecies::decrypt(&requestor_secret, &ethcrypto::DEFAULT_MAC, &combined_signature).unwrap();
+			let signature_c = Secret::from_slice(&combined_signature[..32]);
+			let signature_s = Secret::from_slice(&combined_signature[32..]);
+
+			// check signature
+			assert_eq!(math::verify_signature(&server_public, &(signature_c, signature_s), &message_hash), Ok(true));
+		}
+	}
 }

secret_store/src/key_server_cluster/cluster.rs

@@ -16,9 +16,8 @@
 
 use std::io;
 use std::time;
-use std::sync::{Arc, Weak};
+use std::sync::Arc;
-use std::sync::atomic::{AtomicBool, Ordering};
+use std::collections::{BTreeMap, BTreeSet};
-use std::collections::{BTreeMap, BTreeSet, VecDeque};
 use std::collections::btree_map::Entry;
 use std::net::{SocketAddr, IpAddr};
 use futures::{finished, failed, Future, Stream, BoxFuture};
@@ -27,13 +26,19 @@ use parking_lot::{RwLock, Mutex};
 use tokio_io::IoFuture;
 use tokio_core::reactor::{Handle, Remote, Interval};
 use tokio_core::net::{TcpListener, TcpStream};
-use ethkey::{Public, Secret, KeyPair, Signature, Random, Generator};
+use ethkey::{Public, KeyPair, Signature, Random, Generator};
-use key_server_cluster::{Error, NodeId, SessionId, AclStorage, KeyStorage, DocumentEncryptedKeyShadow};
+use util::H256;
-use key_server_cluster::message::{self, Message, ClusterMessage, EncryptionMessage, DecryptionMessage};
+use key_server_cluster::{Error, NodeId, SessionId, AclStorage, KeyStorage};
-use key_server_cluster::decryption_session::{SessionImpl as DecryptionSessionImpl, SessionState as DecryptionSessionState,
+use key_server_cluster::cluster_sessions::{ClusterSession, ClusterSessions, GenerationSessionWrapper, EncryptionSessionWrapper,
-	SessionParams as DecryptionSessionParams, Session as DecryptionSession, DecryptionSessionId};
+	DecryptionSessionWrapper, SigningSessionWrapper};
-use key_server_cluster::encryption_session::{SessionImpl as EncryptionSessionImpl, SessionState as EncryptionSessionState,
+use key_server_cluster::message::{self, Message, ClusterMessage, GenerationMessage, EncryptionMessage, DecryptionMessage,
-	SessionParams as EncryptionSessionParams, Session as EncryptionSession};
+	SigningMessage, ConsensusMessage};
+use key_server_cluster::generation_session::{Session as GenerationSession, SessionState as GenerationSessionState};
+#[cfg(test)]
+use key_server_cluster::generation_session::SessionImpl as GenerationSessionImpl;
+use key_server_cluster::decryption_session::{Session as DecryptionSession, DecryptionSessionId};
+use key_server_cluster::encryption_session::{Session as EncryptionSession, SessionState as EncryptionSessionState};
+use key_server_cluster::signing_session::{Session as SigningSession, SigningSessionId};
 use key_server_cluster::io::{DeadlineStatus, ReadMessage, SharedTcpStream, read_encrypted_message, WriteMessage, write_encrypted_message};
 use key_server_cluster::net::{accept_connection as net_accept_connection, connect as net_connect, Connection as NetConnection};
 
@@ -50,18 +55,6 @@ const KEEP_ALIVE_SEND_INTERVAL: u64 = 30;
 /// we must treat this node as non-responding && disconnect from it.
 const KEEP_ALIVE_DISCONNECT_INTERVAL: u64 = 60;
 
-/// When there are no encryption session-related messages for ENCRYPTION_SESSION_TIMEOUT_INTERVAL seconds,
-/// we must treat this session as stalled && finish it with an error.
-/// This timeout is for cases when node is responding to KeepAlive messages, but intentionally ignores
-/// session messages.
-const ENCRYPTION_SESSION_TIMEOUT_INTERVAL: u64 = 60;
-
-/// When there are no decryption session-related messages for DECRYPTION_SESSION_TIMEOUT_INTERVAL seconds,
-/// we must treat this session as stalled && finish it with an error.
-/// This timeout is for cases when node is responding to KeepAlive messages, but intentionally ignores
-/// session messages.
-const DECRYPTION_SESSION_TIMEOUT_INTERVAL: u64 = 60;
-
 /// Encryption sesion timeout interval. It works
 /// Empty future.
 type BoxedEmptyFuture = BoxFuture<(), ()>;
@@ -70,23 +63,27 @@ type BoxedEmptyFuture = BoxFuture<(), ()>;
 pub trait ClusterClient: Send + Sync {
 	/// Get cluster state.
 	fn cluster_state(&self) -> ClusterState;
+	/// Start new generation session.
+	fn new_generation_session(&self, session_id: SessionId, author: Public, threshold: usize) -> Result<Arc<GenerationSession>, Error>;
 	/// Start new encryption session.
-	fn new_encryption_session(&self, session_id: SessionId, threshold: usize) -> Result<Arc<EncryptionSession>, Error>;
+	fn new_encryption_session(&self, session_id: SessionId, requestor_signature: Signature, common_point: Public, encrypted_point: Public) -> Result<Arc<EncryptionSession>, Error>;
 	/// Start new decryption session.
 	fn new_decryption_session(&self, session_id: SessionId, requestor_signature: Signature, is_shadow_decryption: bool) -> Result<Arc<DecryptionSession>, Error>;
+	/// Start new signing session.
+	fn new_signing_session(&self, session_id: SessionId, requestor_signature: Signature, message_hash: H256) -> Result<Arc<SigningSession>, Error>;
 
 	#[cfg(test)]
-	/// Ask node to make 'faulty' encryption sessions.
+	/// Ask node to make 'faulty' generation sessions.
-	fn make_faulty_encryption_sessions(&self);
+	fn make_faulty_generation_sessions(&self);
 	#[cfg(test)]
-	/// Get active encryption session with given id.
+	/// Get active generation session with given id.
-	fn encryption_session(&self, session_id: &SessionId) -> Option<Arc<EncryptionSessionImpl>>;
+	fn generation_session(&self, session_id: &SessionId) -> Option<Arc<GenerationSessionImpl>>;
 	#[cfg(test)]
 	/// Try connect to disconnected nodes.
 	fn connect(&self);
 }
 
-/// Cluster access for single encryption/decryption participant.
+/// Cluster access for single encryption/decryption/signing participant.
 pub trait Cluster: Send + Sync {
 	/// Broadcast message to all other nodes.
 	fn broadcast(&self, message: Message) -> Result<(), Error>;
@@ -166,52 +163,6 @@ pub struct ClusterConnections {
 	pub connections: RwLock<BTreeMap<NodeId, Arc<Connection>>>,
 }
 
-/// Active sessions on this cluster.
-pub struct ClusterSessions {
-	/// Self node id.
-	pub self_node_id: NodeId,
-	/// All nodes ids.
-	pub nodes: BTreeSet<NodeId>,
-	/// Reference to key storage
-	pub key_storage: Arc<KeyStorage>,
-	/// Reference to ACL storage
-	pub acl_storage: Arc<AclStorage>,
-	/// Active encryption sessions.
-	pub encryption_sessions: RwLock<BTreeMap<SessionId, QueuedEncryptionSession>>,
-	/// Active decryption sessions.
-	pub decryption_sessions: RwLock<BTreeMap<DecryptionSessionId, QueuedDecryptionSession>>,
-	/// Make faulty encryption sessions.
-	pub make_faulty_encryption_sessions: AtomicBool,
-}
-
-/// Encryption session and its message queue.
-pub struct QueuedEncryptionSession {
-	/// Session master.
-	pub master: NodeId,
-	/// Cluster view.
-	pub cluster_view: Arc<ClusterView>,
-	/// Last received message time.
-	pub last_message_time: time::Instant,
-	/// Encryption session.
-	pub session: Arc<EncryptionSessionImpl>,
-	/// Messages queue.
-	pub queue: VecDeque<(NodeId, EncryptionMessage)>,
-}
-
-/// Decryption session and its message queue.
-pub struct QueuedDecryptionSession {
-	/// Session master.
-	pub master: NodeId,
-	/// Cluster view.
-	pub cluster_view: Arc<ClusterView>,
-	/// Last received message time.
-	pub last_message_time: time::Instant,
-	/// Decryption session.
-	pub session: Arc<DecryptionSessionImpl>,
-	/// Messages queue.
-	pub queue: VecDeque<(NodeId, DecryptionMessage)>,
-}
-
 /// Cluster view core.
 struct ClusterViewCore {
 	/// Cluster reference.
@@ -236,28 +187,6 @@ pub struct Connection {
 	last_message_time: Mutex<time::Instant>,
 }
 
-/// Encryption session implementation, which removes session from cluster on drop.
-struct EncryptionSessionWrapper {
-	/// Wrapped session.
-	session: Arc<EncryptionSession>,
-	/// Session Id.
-	session_id: SessionId,
-	/// Cluster data reference.
-	cluster: Weak<ClusterData>,
-}
-
-/// Decryption session implementation, which removes session from cluster on drop.
-struct DecryptionSessionWrapper {
-	/// Wrapped session.
-	session: Arc<DecryptionSession>,
-	/// Session Id.
-	session_id: SessionId,
-	/// Session sub id.
-	access_key: Secret,
-	/// Cluster data reference.
-	cluster: Weak<ClusterData>,
-}
-
 impl ClusterCore {
 	pub fn new(handle: Handle, config: ClusterConfiguration) -> Result<Arc<Self>, Error> {
 		let listen_address = make_socket_address(&config.listen_address.0, config.listen_address.1)?;
@@ -461,62 +390,49 @@ impl ClusterCore {
 		connection.set_last_message_time(time::Instant::now());
 		trace!(target: "secretstore_net", "{}: received message {} from {}", data.self_key_pair.public(), message, connection.node_id());
 		match message {
+			Message::Generation(message) => ClusterCore::process_generation_message(data, connection, message),
 			Message::Encryption(message) => ClusterCore::process_encryption_message(data, connection, message),
 			Message::Decryption(message) => ClusterCore::process_decryption_message(data, connection, message),
+			Message::Signing(message) => ClusterCore::process_signing_message(data, connection, message),
 			Message::Cluster(message) => ClusterCore::process_cluster_message(data, connection, message),
 		}
 	}
 
-	/// Process single encryption message from the connection.
+	/// Process single generation message from the connection.
-	fn process_encryption_message(data: Arc<ClusterData>, connection: Arc<Connection>, mut message: EncryptionMessage) {
+	fn process_generation_message(data: Arc<ClusterData>, connection: Arc<Connection>, mut message: GenerationMessage) {
 		let session_id = message.session_id().clone();
 		let mut sender = connection.node_id().clone();
 		let session = match message {
-			EncryptionMessage::InitializeSession(_) => {
+			GenerationMessage::InitializeSession(_) => {
 				let mut connected_nodes = data.connections.connected_nodes();
 				connected_nodes.insert(data.self_key_pair.public().clone());
 
 				let cluster = Arc::new(ClusterView::new(data.clone(), connected_nodes));
-				data.sessions.new_encryption_session(sender.clone(), session_id.clone(), cluster)
+				data.sessions.new_generation_session(sender.clone(), session_id.clone(), cluster)
 			},
 			_ => {
-				data.sessions.encryption_session(&session_id)
+				data.sessions.generation_sessions.get(&session_id)
 					.ok_or(Error::InvalidSessionId)
 			},
 		};
 
 		let mut is_queued_message = false;
 		loop {
-			match session.clone().and_then(|session| match message {
+			match session.clone().and_then(|session| session.process_message(&sender, &message)) {
-				EncryptionMessage::InitializeSession(ref message) =>
-					session.on_initialize_session(sender.clone(), message),
-				EncryptionMessage::ConfirmInitialization(ref message) =>
-					session.on_confirm_initialization(sender.clone(), message),
-				EncryptionMessage::CompleteInitialization(ref message) =>
-					session.on_complete_initialization(sender.clone(), message),
-				EncryptionMessage::KeysDissemination(ref message) =>
-					session.on_keys_dissemination(sender.clone(), message),
-				EncryptionMessage::PublicKeyShare(ref message) =>
-					session.on_public_key_share(sender.clone(), message),
-				EncryptionMessage::SessionError(ref message) =>
-					session.on_session_error(sender.clone(), message),
-				EncryptionMessage::SessionCompleted(ref message) => 
-					session.on_session_completed(sender.clone(), message),
-			}) {
 				Ok(_) => {
 					// if session is completed => stop
 					let session = session.clone().expect("session.method() call finished with success; session exists; qed");
 					let session_state = session.state();
-					if session_state == EncryptionSessionState::Finished {
+					if session_state == GenerationSessionState::Finished {
-						info!(target: "secretstore_net", "{}: encryption session completed", data.self_key_pair.public());
+						info!(target: "secretstore_net", "{}: generation session completed", data.self_key_pair.public());
 					}
-					if session_state == EncryptionSessionState::Finished || session_state == EncryptionSessionState::Failed {
+					if session_state == GenerationSessionState::Finished || session_state == GenerationSessionState::Failed {
-						data.sessions.remove_encryption_session(&session_id);
+						data.sessions.generation_sessions.remove(&session_id);
 						break;
 					}
 
 					// try to dequeue message
-					match data.sessions.dequeue_encryption_message(&session_id) {
+					match data.sessions.generation_sessions.dequeue_message(&session_id) {
 						Some((msg_sender, msg)) => {
 							is_queued_message = true;
 							sender = msg_sender;
@@ -526,17 +442,86 @@ impl ClusterCore {
 					}
 				},
 				Err(Error::TooEarlyForRequest) => {
-					data.sessions.enqueue_encryption_message(&session_id, sender, message, is_queued_message);
+					data.sessions.generation_sessions.enqueue_message(&session_id, sender, message, is_queued_message);
 					break;
 				},
 				Err(err) => {
-					warn!(target: "secretstore_net", "{}: encryption session error {} when processing message {} from node {}", data.self_key_pair.public(), err, message, sender);
+					warn!(target: "secretstore_net", "{}: generation session error {} when processing message {} from node {}", data.self_key_pair.public(), err, message, sender);
-					data.sessions.respond_with_encryption_error(&session_id, message::SessionError {
+					data.sessions.respond_with_generation_error(&session_id, message::SessionError {
 						session: session_id.clone().into(),
 						error: format!("{:?}", err),
 					});
 					if err != Error::InvalidSessionId {
-						data.sessions.remove_encryption_session(&session_id);
+						data.sessions.generation_sessions.remove(&session_id);
+					}
+					break;
+				},
+			}
+		}
+	}
+
+	/// Process single encryption message from the connection.
+	fn process_encryption_message(data: Arc<ClusterData>, connection: Arc<Connection>, mut message: EncryptionMessage) {
+		let session_id = message.session_id().clone();
+		let mut sender = connection.node_id().clone();
+		let session = match message {
+			EncryptionMessage::InitializeEncryptionSession(_) => {
+				let mut connected_nodes = data.connections.connected_nodes();
+				connected_nodes.insert(data.self_key_pair.public().clone());
+
+				let cluster = Arc::new(ClusterView::new(data.clone(), connected_nodes));
+				data.sessions.new_encryption_session(sender.clone(), session_id.clone(), cluster)
+			},
+			_ => {
+				data.sessions.encryption_sessions.get(&session_id)
+					.ok_or(Error::InvalidSessionId)
+			},
+		};
+
+		let mut is_queued_message = false;
+		loop {
+			match session.clone().and_then(|session| match message {
+				EncryptionMessage::InitializeEncryptionSession(ref message) =>
+					session.on_initialize_session(sender.clone(), message),
+				EncryptionMessage::ConfirmEncryptionInitialization(ref message) =>
+					session.on_confirm_initialization(sender.clone(), message),
+				EncryptionMessage::EncryptionSessionError(ref message) =>
+					session.on_session_error(sender.clone(), message),
+			}) {
+				Ok(_) => {
+					// if session is completed => stop
+					let session = session.clone().expect("session.method() call finished with success; session exists; qed");
+					let session_state = session.state();
+					if session_state == EncryptionSessionState::Finished {
+						info!(target: "secretstore_net", "{}: encryption session completed", data.self_key_pair.public());
+					}
+					if session_state == EncryptionSessionState::Finished || session_state == EncryptionSessionState::Failed {
+						data.sessions.encryption_sessions.remove(&session_id);
+						break;
+					}
+
+					// try to dequeue message
+					match data.sessions.encryption_sessions.dequeue_message(&session_id) {
+						Some((msg_sender, msg)) => {
+							is_queued_message = true;
+							sender = msg_sender;
+							message = msg;
+						},
+						None => break,
+					}
+				},
+				Err(Error::TooEarlyForRequest) => {
+					data.sessions.encryption_sessions.enqueue_message(&session_id, sender, message, is_queued_message);
+					break;
+				},
+				Err(err) => {
+					warn!(target: "secretstore_net", "{}: encryption session error {} when processing message {} from node {}", data.self_key_pair.public(), err, message, sender);
+					data.sessions.respond_with_encryption_error(&session_id, message::EncryptionSessionError {
+						session: session_id.clone().into(),
+						error: format!("{:?}", err),
+					});
+					if err != Error::InvalidSessionId {
+						data.sessions.encryption_sessions.remove(&session_id);
 					}
 					break;
 				},
@@ -548,63 +533,45 @@ impl ClusterCore {
 	fn process_decryption_message(data: Arc<ClusterData>, connection: Arc<Connection>, mut message: DecryptionMessage) {
 		let session_id = message.session_id().clone();
 		let sub_session_id = message.sub_session_id().clone();
+		let decryption_session_id = DecryptionSessionId::new(session_id.clone(), sub_session_id.clone());
 		let mut sender = connection.node_id().clone();
 		let session = match message {
-			DecryptionMessage::InitializeDecryptionSession(_) => {
+			DecryptionMessage::DecryptionConsensusMessage(ref message) if match message.message {
+				ConsensusMessage::InitializeConsensusSession(_) => true,
+				_ => false,
+			} => {
 				let mut connected_nodes = data.connections.connected_nodes();
 				connected_nodes.insert(data.self_key_pair.public().clone());
 
 				let cluster = Arc::new(ClusterView::new(data.clone(), connected_nodes));
-				data.sessions.new_decryption_session(sender.clone(), session_id.clone(), sub_session_id.clone(), cluster)
+				data.sessions.new_decryption_session(sender.clone(), session_id.clone(), sub_session_id.clone(), cluster, None)
 			},
 			_ => {
-				data.sessions.decryption_session(&session_id, &sub_session_id)
+				data.sessions.decryption_sessions.get(&decryption_session_id)
 					.ok_or(Error::InvalidSessionId)
 			},
 		};
 
-		let mut is_queued_message = false;
 		loop {
-			match session.clone().and_then(|session| match message {
+			match session.clone().and_then(|session| session.process_message(&sender, &message)) {
-				DecryptionMessage::InitializeDecryptionSession(ref message) =>
-					session.on_initialize_session(sender.clone(), message),
-				DecryptionMessage::ConfirmDecryptionInitialization(ref message) =>
-					session.on_confirm_initialization(sender.clone(), message),
-				DecryptionMessage::RequestPartialDecryption(ref message) => 
-					session.on_partial_decryption_requested(sender.clone(), message),
-				DecryptionMessage::PartialDecryption(ref message) => 
-					session.on_partial_decryption(sender.clone(), message),
-				DecryptionMessage::DecryptionSessionError(ref message) => 
-					session.on_session_error(sender.clone(), message),
-				DecryptionMessage::DecryptionSessionCompleted(ref message) => 
-					session.on_session_completed(sender.clone(), message),
-			}) {
 				Ok(_) => {
 					// if session is completed => stop
 					let session = session.clone().expect("session.method() call finished with success; session exists; qed");
-					let session_state = session.state();
+					if session.is_finished() {
-					if session_state == DecryptionSessionState::Finished {
 						info!(target: "secretstore_net", "{}: decryption session completed", data.self_key_pair.public());
-					}
+						data.sessions.decryption_sessions.remove(&decryption_session_id);
-					if session_state == DecryptionSessionState::Finished || session_state == DecryptionSessionState::Failed {
-						data.sessions.remove_decryption_session(&session_id, &sub_session_id);
 						break;
 					}
 
 					// try to dequeue message
-					match data.sessions.dequeue_decryption_message(&session_id, &sub_session_id) {
+					match data.sessions.decryption_sessions.dequeue_message(&decryption_session_id) {
 						Some((msg_sender, msg)) => {
-							is_queued_message = true;
 							sender = msg_sender;
 							message = msg;
 						},
 						None => break,
 					}
 				},
-				Err(Error::TooEarlyForRequest) => {
-					data.sessions.enqueue_decryption_message(&session_id, &sub_session_id, sender, message, is_queued_message);
-					break;
-				},
 				Err(err) => {
 					warn!(target: "secretstore_net", "{}: decryption session error {} when processing message {} from node {}", data.self_key_pair.public(), err, message, sender);
 					data.sessions.respond_with_decryption_error(&session_id, &sub_session_id, &sender, message::DecryptionSessionError {
@@ -613,7 +580,72 @@ impl ClusterCore {
 						error: format!("{:?}", err),
 					});
 					if err != Error::InvalidSessionId {
-						data.sessions.remove_decryption_session(&session_id, &sub_session_id);
+						data.sessions.decryption_sessions.remove(&decryption_session_id);
+					}
+					break;
+				},
+			}
+		}
+	}
+
+	/// Process singlesigning message from the connection.
+	fn process_signing_message(data: Arc<ClusterData>, connection: Arc<Connection>, mut message: SigningMessage) {
+		let session_id = message.session_id().clone();
+		let sub_session_id = message.sub_session_id().clone();
+		let signing_session_id = SigningSessionId::new(session_id.clone(), sub_session_id.clone());
+		let mut sender = connection.node_id().clone();
+		let session = match message {
+			SigningMessage::SigningConsensusMessage(ref message) if match message.message {
+				ConsensusMessage::InitializeConsensusSession(_) => true,
+				_ => false,
+			} => {
+				let mut connected_nodes = data.connections.connected_nodes();
+				connected_nodes.insert(data.self_key_pair.public().clone());
+
+				let cluster = Arc::new(ClusterView::new(data.clone(), connected_nodes));
+				data.sessions.new_signing_session(sender.clone(), session_id.clone(), sub_session_id.clone(), cluster, None)
+			},
+			_ => {
+				data.sessions.signing_sessions.get(&signing_session_id)
+					.ok_or(Error::InvalidSessionId)
+			},
+		};
+
+		let mut is_queued_message = false;
+		loop {
+			match session.clone().and_then(|session| session.process_message(&sender, &message)) {
+				Ok(_) => {
+					// if session is completed => stop
+					let session = session.clone().expect("session.method() call finished with success; session exists; qed");
+					if session.is_finished() {
+						info!(target: "secretstore_net", "{}: signing session completed", data.self_key_pair.public());
+						data.sessions.signing_sessions.remove(&signing_session_id);
+						break;
+					}
+
+					// try to dequeue message
+					match data.sessions.signing_sessions.dequeue_message(&signing_session_id) {
+						Some((msg_sender, msg)) => {
+							is_queued_message = true;
+							sender = msg_sender;
+							message = msg;
+						},
+						None => break,
+					}
+				},
+				Err(Error::TooEarlyForRequest) => {
+					data.sessions.signing_sessions.enqueue_message(&signing_session_id, sender, message, is_queued_message);
+					break;
+				},
+				Err(err) => {
+					warn!(target: "secretstore_net", "{}: signing session error {} when processing message {} from node {}", data.self_key_pair.public(), err, message, sender);
+					data.sessions.respond_with_signing_error(&session_id, &sub_session_id, &sender, message::SigningSessionError {
+						session: session_id.clone().into(),
+						sub_session: sub_session_id.clone().into(),
+						error: format!("{:?}", err),
+					});
+					if err != Error::InvalidSessionId {
+						data.sessions.signing_sessions.remove(&signing_session_id);
 					}
 					break;
 				},
@@ -702,213 +734,6 @@ impl ClusterConnections {
 	}
 }
 
-impl ClusterSessions {
-	pub fn new(config: &ClusterConfiguration) -> Self {
-		ClusterSessions {
-			self_node_id: config.self_key_pair.public().clone(),
-			nodes: config.nodes.keys().cloned().collect(),
-			acl_storage: config.acl_storage.clone(),
-			key_storage: config.key_storage.clone(),
-			encryption_sessions: RwLock::new(BTreeMap::new()),
-			decryption_sessions: RwLock::new(BTreeMap::new()),
-			make_faulty_encryption_sessions: AtomicBool::new(false),
-		}
-	}
-
-	pub fn new_encryption_session(&self, master: NodeId, session_id: SessionId, cluster: Arc<ClusterView>) -> Result<Arc<EncryptionSessionImpl>, Error> {
-		let mut encryption_sessions = self.encryption_sessions.write();
-		// check that there's no active encryption session with the same id
-		if encryption_sessions.contains_key(&session_id) {
-			return Err(Error::DuplicateSessionId);
-		}
-		// check that there's no finished encryption session with the same id
-		if self.key_storage.contains(&session_id) {
-			return Err(Error::DuplicateSessionId);
-		}
-
-		// communicating to all other nodes is crucial for encryption session
-		// => check that we have connections to all cluster nodes
-		if self.nodes.iter().any(|n| !cluster.is_connected(n)) {
-			return Err(Error::NodeDisconnected);
-		}
-
-		let session = Arc::new(EncryptionSessionImpl::new(EncryptionSessionParams {
-			id: session_id.clone(),
-			self_node_id: self.self_node_id.clone(),
-			key_storage: self.key_storage.clone(),
-			cluster: cluster.clone(),
-		}));
-		let encryption_session = QueuedEncryptionSession {
-			master: master,
-			cluster_view: cluster,
-			last_message_time: time::Instant::now(),
-			session: session.clone(),
-			queue: VecDeque::new()
-		};
-		if self.make_faulty_encryption_sessions.load(Ordering::Relaxed) {
-			encryption_session.session.simulate_faulty_behaviour();
-		}
-		encryption_sessions.insert(session_id, encryption_session);
-		Ok(session)
-	}
-
-	pub fn remove_encryption_session(&self, session_id: &SessionId) {
-		self.encryption_sessions.write().remove(session_id);
-	}
-
-	pub fn encryption_session(&self, session_id: &SessionId) -> Option<Arc<EncryptionSessionImpl>> {
-		self.encryption_sessions.read().get(session_id).map(|s| s.session.clone())
-	}
-
-	pub fn enqueue_encryption_message(&self, session_id: &SessionId, sender: NodeId, message: EncryptionMessage, is_queued_message: bool) {
-		self.encryption_sessions.write().get_mut(session_id)
-			.map(|session| if is_queued_message { session.queue.push_front((sender, message)) }
-				else { session.queue.push_back((sender, message)) });
-	}
-
-	pub fn dequeue_encryption_message(&self, session_id: &SessionId) -> Option<(NodeId, EncryptionMessage)> {
-		self.encryption_sessions.write().get_mut(session_id)
-			.and_then(|session| session.queue.pop_front())
-	}
-
-	pub fn respond_with_encryption_error(&self, session_id: &SessionId, error: message::SessionError) {
-		self.encryption_sessions.read().get(session_id)
-			.map(|s| {
-				// error in encryption session is considered fatal
-				// => broadcast error
-
-				// do not bother processing send error, as we already processing error
-				let _ = s.cluster_view.broadcast(Message::Encryption(EncryptionMessage::SessionError(error)));
-			});
-	}
-
-	#[cfg(test)]
-	pub fn make_faulty_encryption_sessions(&self) {
-		self.make_faulty_encryption_sessions.store(true, Ordering::Relaxed);
-	}
-
-	pub fn new_decryption_session(&self, master: NodeId, session_id: SessionId, sub_session_id: Secret, cluster: Arc<ClusterView>) -> Result<Arc<DecryptionSessionImpl>, Error> {
-		let mut decryption_sessions = self.decryption_sessions.write();
-		let session_id = DecryptionSessionId::new(session_id, sub_session_id);
-		if decryption_sessions.contains_key(&session_id) {
-			return Err(Error::DuplicateSessionId);
-		}
-
-		// some of nodes, which were encrypting secret may be down
-		// => do not use these in decryption session
-		let mut encrypted_data = self.key_storage.get(&session_id.id).map_err(|e| Error::KeyStorage(e.into()))?;
-		let disconnected_nodes: BTreeSet<_> = encrypted_data.id_numbers.keys().cloned().collect();
-		let disconnected_nodes: BTreeSet<_> = disconnected_nodes.difference(&cluster.nodes()).cloned().collect();
-		for disconnected_node in disconnected_nodes {
-			encrypted_data.id_numbers.remove(&disconnected_node);
-		}
-
-		let session = Arc::new(DecryptionSessionImpl::new(DecryptionSessionParams {
-			id: session_id.id.clone(),
-			access_key: session_id.access_key.clone(),
-			self_node_id: self.self_node_id.clone(),
-			encrypted_data: encrypted_data,
-			acl_storage: self.acl_storage.clone(),
-			cluster: cluster.clone(),
-		})?);
-		let decryption_session = QueuedDecryptionSession {
-			master: master,
-			cluster_view: cluster,
-			last_message_time: time::Instant::now(),
-			session: session.clone(),
-			queue: VecDeque::new()
-		};
-		decryption_sessions.insert(session_id, decryption_session);
-		Ok(session)
-	}
-
-	pub fn remove_decryption_session(&self, session_id: &SessionId, sub_session_id: &Secret) {
-		let session_id = DecryptionSessionId::new(session_id.clone(), sub_session_id.clone());
-		self.decryption_sessions.write().remove(&session_id);
-	}
-
-	pub fn decryption_session(&self, session_id: &SessionId, sub_session_id: &Secret) -> Option<Arc<DecryptionSessionImpl>> {
-		let session_id = DecryptionSessionId::new(session_id.clone(), sub_session_id.clone());
-		self.decryption_sessions.read().get(&session_id).map(|s| s.session.clone())
-	}
-
-	pub fn enqueue_decryption_message(&self, session_id: &SessionId, sub_session_id: &Secret, sender: NodeId, message: DecryptionMessage, is_queued_message: bool) {
-		let session_id = DecryptionSessionId::new(session_id.clone(), sub_session_id.clone());
-		self.decryption_sessions.write().get_mut(&session_id)
-			.map(|session| if is_queued_message { session.queue.push_front((sender, message)) }
-				else { session.queue.push_back((sender, message)) });
-	}
-
-	pub fn dequeue_decryption_message(&self, session_id: &SessionId, sub_session_id: &Secret) -> Option<(NodeId, DecryptionMessage)> {
-		let session_id = DecryptionSessionId::new(session_id.clone(), sub_session_id.clone());
-		self.decryption_sessions.write().get_mut(&session_id)
-			.and_then(|session| session.queue.pop_front())
-	}
-
-	pub fn respond_with_decryption_error(&self, session_id: &SessionId, sub_session_id: &Secret, to: &NodeId, error: message::DecryptionSessionError) {
-		let session_id = DecryptionSessionId::new(session_id.clone(), sub_session_id.clone());
-		self.decryption_sessions.read().get(&session_id)
-			.map(|s| {
-				// error in decryption session is non-fatal, if occurs on slave node
-				// => either respond with error
-				// => or broadcast error
-
-				// do not bother processing send error, as we already processing error
-				if &s.master == s.session.node() {
-					let _ = s.cluster_view.broadcast(Message::Decryption(DecryptionMessage::DecryptionSessionError(error)));
-				} else {
-					let _ = s.cluster_view.send(to, Message::Decryption(DecryptionMessage::DecryptionSessionError(error)));
-				}
-			});
-	}
-
-	fn stop_stalled_sessions(&self) {
-		{
-			let sessions = self.encryption_sessions.write();
-			for sid in sessions.keys().collect::<Vec<_>>() {
-				let session = sessions.get(&sid).expect("enumerating only existing sessions; qed");
-				if time::Instant::now() - session.last_message_time > time::Duration::from_secs(ENCRYPTION_SESSION_TIMEOUT_INTERVAL) {
-					session.session.on_session_timeout();
-					if session.session.state() == EncryptionSessionState::Finished
-						|| session.session.state() == EncryptionSessionState::Failed {
-						self.remove_encryption_session(&sid);
-					}
-				}
-			}
-		}
-		{
-			let sessions = self.decryption_sessions.write();
-			for sid in sessions.keys().collect::<Vec<_>>() {
-				let session = sessions.get(&sid).expect("enumerating only existing sessions; qed");
-				if time::Instant::now() - session.last_message_time > time::Duration::from_secs(DECRYPTION_SESSION_TIMEOUT_INTERVAL) {
-					session.session.on_session_timeout();
-					if session.session.state() == DecryptionSessionState::Finished
-						|| session.session.state() == DecryptionSessionState::Failed {
-						self.remove_decryption_session(&sid.id, &sid.access_key);
-					}
-				}
-			}
-		}
-	}
-
-	pub fn on_connection_timeout(&self, node_id: &NodeId) {
-		for (sid, session) in self.encryption_sessions.read().iter() {
-			session.session.on_node_timeout(node_id);
-			if session.session.state() == EncryptionSessionState::Finished
-				|| session.session.state() == EncryptionSessionState::Failed {
-				self.remove_encryption_session(sid);
-			}
-		}
-		for (sid, session) in self.decryption_sessions.read().iter() {
-			session.session.on_node_timeout(node_id);
-			if session.session.state() == DecryptionSessionState::Finished
-				|| session.session.state() == DecryptionSessionState::Failed {
-				self.remove_decryption_session(&sid.id, &sid.access_key);
-			}
-		}
-	}
-}
-
 impl ClusterData {
 	pub fn new(handle: &Handle, config: ClusterConfiguration, connections: ClusterConnections, sessions: ClusterSessions) -> Arc<Self> {
 		Arc::new(ClusterData {
@@ -926,6 +751,11 @@ impl ClusterData {
 		self.connections.get(node)
 	}
 
+	/// Get sessions reference.
+	pub fn sessions(&self) -> &ClusterSessions {
+		&self.sessions
+	}
+
 	/// Spawns a future using thread pool and schedules execution of it with event loop handle.
 	pub fn spawn<F>(&self, f: F) where F: Future + Send + 'static, F::Item: Send + 'static, F::Error: Send + 'static {
 		let pool_work = self.pool.spawn(f);
@@ -1028,13 +858,23 @@ impl ClusterClient for ClusterClientImpl {
 		self.data.connections.cluster_state()
 	}
 
-	fn new_encryption_session(&self, session_id: SessionId, threshold: usize) -> Result<Arc<EncryptionSession>, Error> {
+	fn new_generation_session(&self, session_id: SessionId, author: Public, threshold: usize) -> Result<Arc<GenerationSession>, Error> {
 		let mut connected_nodes = self.data.connections.connected_nodes();
 		connected_nodes.insert(self.data.self_key_pair.public().clone());
 
 		let cluster = Arc::new(ClusterView::new(self.data.clone(), connected_nodes.clone()));
-		let session = self.data.sessions.new_encryption_session(self.data.self_key_pair.public().clone(), session_id.clone(), cluster)?;
+		let session = self.data.sessions.new_generation_session(self.data.self_key_pair.public().clone(), session_id, cluster)?;
-		session.initialize(threshold, connected_nodes)?;
+		session.initialize(author, threshold, connected_nodes)?;
+		Ok(GenerationSessionWrapper::new(Arc::downgrade(&self.data), session_id, session))
+	}
+
+	fn new_encryption_session(&self, session_id: SessionId, requestor_signature: Signature, common_point: Public, encrypted_point: Public) -> Result<Arc<EncryptionSession>, Error> {
+		let mut connected_nodes = self.data.connections.connected_nodes();
+		connected_nodes.insert(self.data.self_key_pair.public().clone());
+
+		let cluster = Arc::new(ClusterView::new(self.data.clone(), connected_nodes.clone()));
+		let session = self.data.sessions.new_encryption_session(self.data.self_key_pair.public().clone(), session_id, cluster)?;
+		session.initialize(requestor_signature, common_point, encrypted_point)?;
 		Ok(EncryptionSessionWrapper::new(Arc::downgrade(&self.data), session_id, session))
 	}
 
@@ -1044,9 +884,20 @@ impl ClusterClient for ClusterClientImpl {
 
 		let access_key = Random.generate()?.secret().clone();
 		let cluster = Arc::new(ClusterView::new(self.data.clone(), connected_nodes.clone()));
-		let session = self.data.sessions.new_decryption_session(self.data.self_key_pair.public().clone(), session_id, access_key.clone(), cluster)?;
+		let session = self.data.sessions.new_decryption_session(self.data.self_key_pair.public().clone(), session_id, access_key.clone(), cluster, Some(requestor_signature))?;
-		session.initialize(requestor_signature, is_shadow_decryption)?;
+		session.initialize(is_shadow_decryption)?;
-		Ok(DecryptionSessionWrapper::new(Arc::downgrade(&self.data), session_id, access_key, session))
+		Ok(DecryptionSessionWrapper::new(Arc::downgrade(&self.data), DecryptionSessionId::new(session_id, access_key), session))
+	}
+
+	fn new_signing_session(&self, session_id: SessionId, requestor_signature: Signature, message_hash: H256) -> Result<Arc<SigningSession>, Error> {
+		let mut connected_nodes = self.data.connections.connected_nodes();
+		connected_nodes.insert(self.data.self_key_pair.public().clone());
+
+		let access_key = Random.generate()?.secret().clone();
+		let cluster = Arc::new(ClusterView::new(self.data.clone(), connected_nodes.clone()));
+		let session = self.data.sessions.new_signing_session(self.data.self_key_pair.public().clone(), session_id, access_key.clone(), cluster, Some(requestor_signature))?;
+		session.initialize(message_hash)?;
+		Ok(SigningSessionWrapper::new(Arc::downgrade(&self.data), SigningSessionId::new(session_id, access_key), session))
 	}
 
 	#[cfg(test)]
@@ -1055,71 +906,13 @@ impl ClusterClient for ClusterClientImpl {
 	}
 
 	#[cfg(test)]
-	fn make_faulty_encryption_sessions(&self) {
+	fn make_faulty_generation_sessions(&self) {
-		self.data.sessions.make_faulty_encryption_sessions();
+		self.data.sessions.make_faulty_generation_sessions();
 	}
 
 	#[cfg(test)]
-	fn encryption_session(&self, session_id: &SessionId) -> Option<Arc<EncryptionSessionImpl>> {
+	fn generation_session(&self, session_id: &SessionId) -> Option<Arc<GenerationSessionImpl>> {
-		self.data.sessions.encryption_session(session_id)
+		self.data.sessions.generation_sessions.get(session_id)
-	}
-}
-
-impl EncryptionSessionWrapper {
-	pub fn new(cluster: Weak<ClusterData>, session_id: SessionId, session: Arc<EncryptionSession>) -> Arc<Self> {
-		Arc::new(EncryptionSessionWrapper {
-			session: session,
-			session_id: session_id,
-			cluster: cluster,
-		})
-	}
-}
-
-impl EncryptionSession for EncryptionSessionWrapper {
-	fn state(&self) -> EncryptionSessionState {
-		self.session.state()
-	}
-
-	fn wait(&self, timeout: Option<time::Duration>) -> Result<Public, Error> {
-		self.session.wait(timeout)
-	}
-
-	#[cfg(test)]
-	fn joint_public_key(&self) -> Option<Result<Public, Error>> {
-		self.session.joint_public_key()
-	}
-}
-
-impl Drop for EncryptionSessionWrapper {
-	fn drop(&mut self) {
-		if let Some(cluster) = self.cluster.upgrade() {
-			cluster.sessions.remove_encryption_session(&self.session_id);
-		}
-	}
-}
-
-impl DecryptionSessionWrapper {
-	pub fn new(cluster: Weak<ClusterData>, session_id: SessionId, access_key: Secret, session: Arc<DecryptionSession>) -> Arc<Self> {
-		Arc::new(DecryptionSessionWrapper {
-			session: session,
-			session_id: session_id,
-			access_key: access_key,
-			cluster: cluster,
-		})
-	}
-}
-
-impl DecryptionSession for DecryptionSessionWrapper {
-	fn wait(&self) -> Result<DocumentEncryptedKeyShadow, Error> {
-		self.session.wait()
-	}
-}
-
-impl Drop for DecryptionSessionWrapper {
-	fn drop(&mut self) {
-		if let Some(cluster) = self.cluster.upgrade() {
-			cluster.sessions.remove_decryption_session(&self.session_id, &self.access_key);
-		}
 	}
 }
 
@@ -1135,11 +928,11 @@ pub mod tests {
 	use std::collections::VecDeque;
 	use parking_lot::Mutex;
 	use tokio_core::reactor::Core;
-	use ethkey::{Random, Generator};
+	use ethkey::{Random, Generator, Public};
 	use key_server_cluster::{NodeId, SessionId, Error, DummyAclStorage, DummyKeyStorage};
 	use key_server_cluster::message::Message;
 	use key_server_cluster::cluster::{Cluster, ClusterCore, ClusterConfiguration};
-	use key_server_cluster::encryption_session::{Session as EncryptionSession, SessionState as EncryptionSessionState};
+	use key_server_cluster::generation_session::{Session as GenerationSession, SessionState as GenerationSessionState};
 
 	#[derive(Debug)]
 	pub struct DummyCluster {
@@ -1249,11 +1042,11 @@ pub mod tests {
 	}
 
 	#[test]
-	fn cluster_wont_start_encryption_session_if_not_fully_connected() {
+	fn cluster_wont_start_generation_session_if_not_fully_connected() {
 		let core = Core::new().unwrap();
 		let clusters = make_clusters(&core, 6013, 3);
 		clusters[0].run().unwrap();
-		match clusters[0].client().new_encryption_session(SessionId::default(), 1) {
+		match clusters[0].client().new_generation_session(SessionId::default(), Public::default(), 1) {
 			Err(Error::NodeDisconnected) => (),
 			Err(e) => panic!("unexpected error {:?}", e),
 			_ => panic!("unexpected success"),
@@ -1261,50 +1054,50 @@ pub mod tests {
 	}
 
 	#[test]
-	fn error_in_encryption_session_broadcasted_to_all_other_nodes() {
+	fn error_in_generation_session_broadcasted_to_all_other_nodes() {
 		let mut core = Core::new().unwrap();
 		let clusters = make_clusters(&core, 6016, 3);
 		run_clusters(&clusters);
 		loop_until(&mut core, time::Duration::from_millis(300), || clusters.iter().all(all_connections_established));
 
-		// ask one of nodes to produce faulty encryption sessions
+		// ask one of nodes to produce faulty generation sessions
-		clusters[1].client().make_faulty_encryption_sessions();
+		clusters[1].client().make_faulty_generation_sessions();
 
-		// start && wait for encryption session to fail
+		// start && wait for generation session to fail
-		let session = clusters[0].client().new_encryption_session(SessionId::default(), 1).unwrap();
+		let session = clusters[0].client().new_generation_session(SessionId::default(), Public::default(), 1).unwrap();
-		loop_until(&mut core, time::Duration::from_millis(300), || session.joint_public_key().is_some());
+		loop_until(&mut core, time::Duration::from_millis(300), || session.joint_public_and_secret().is_some());
-		assert!(session.joint_public_key().unwrap().is_err());
+		assert!(session.joint_public_and_secret().unwrap().is_err());
 
 		// check that faulty session is either removed from all nodes, or nonexistent (already removed)
-		assert!(clusters[0].client().encryption_session(&SessionId::default()).is_none());
+		assert!(clusters[0].client().generation_session(&SessionId::default()).is_none());
 		for i in 1..3 {
-			if let Some(session) = clusters[i].client().encryption_session(&SessionId::default()) {
+			if let Some(session) = clusters[i].client().generation_session(&SessionId::default()) {
-				loop_until(&mut core, time::Duration::from_millis(300), || session.joint_public_key().is_some());
+				loop_until(&mut core, time::Duration::from_millis(300), || session.joint_public_and_secret().is_some());
-				assert!(session.joint_public_key().unwrap().is_err());
+				assert!(session.joint_public_and_secret().unwrap().is_err());
-				assert!(clusters[i].client().encryption_session(&SessionId::default()).is_none());
+				assert!(clusters[i].client().generation_session(&SessionId::default()).is_none());
 			}
 		}
 	}
 
 	#[test]
-	fn encryption_session_is_removed_when_succeeded() {
+	fn generation_session_is_removed_when_succeeded() {
 		let mut core = Core::new().unwrap();
 		let clusters = make_clusters(&core, 6019, 3);
 		run_clusters(&clusters);
 		loop_until(&mut core, time::Duration::from_millis(300), || clusters.iter().all(all_connections_established));
 
-		// start && wait for encryption session to complete
+		// start && wait for generation session to complete
-		let session = clusters[0].client().new_encryption_session(SessionId::default(), 1).unwrap();
+		let session = clusters[0].client().new_generation_session(SessionId::default(), Public::default(), 1).unwrap();
-		loop_until(&mut core, time::Duration::from_millis(300), || session.state() == EncryptionSessionState::Finished);
+		loop_until(&mut core, time::Duration::from_millis(300), || session.state() == GenerationSessionState::Finished);
-		assert!(session.joint_public_key().unwrap().is_ok());
+		assert!(session.joint_public_and_secret().unwrap().is_ok());
 
 		// check that session is either removed from all nodes, or nonexistent (already removed)
-		assert!(clusters[0].client().encryption_session(&SessionId::default()).is_none());
+		assert!(clusters[0].client().generation_session(&SessionId::default()).is_none());
 		for i in 1..3 {
-			if let Some(session) = clusters[i].client().encryption_session(&SessionId::default()) {
+			if let Some(session) = clusters[i].client().generation_session(&SessionId::default()) {
-				loop_until(&mut core, time::Duration::from_millis(300), || session.state() == EncryptionSessionState::Finished);
+				loop_until(&mut core, time::Duration::from_millis(300), || session.state() == GenerationSessionState::Finished);
-				assert!(session.joint_public_key().unwrap().is_err());
+				assert!(session.joint_public_and_secret().unwrap().is_err());
-				assert!(clusters[i].client().encryption_session(&SessionId::default()).is_none());
+				assert!(clusters[i].client().generation_session(&SessionId::default()).is_none());
 			}
 		}
 	}

secret_store/src/key_server_cluster/cluster_sessions.rs

@@ -0,0 +1,506 @@
+// Copyright 2015-2017 Parity Technologies (UK) Ltd.
+// This file is part of Parity.
+
+// Parity is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Parity is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Parity.  If not, see <http://www.gnu.org/licenses/>.
+
+use std::time;
+use std::sync::{Arc, Weak};
+use std::sync::atomic::{AtomicBool, Ordering};
+use std::collections::{VecDeque, BTreeSet, BTreeMap};
+use parking_lot::RwLock;
+use ethkey::{Public, Secret, Signature};
+use key_server_cluster::{Error, NodeId, SessionId, AclStorage, KeyStorage, DocumentKeyShare, EncryptedDocumentKeyShadow, SessionMeta};
+use key_server_cluster::cluster::{Cluster, ClusterData, ClusterView, ClusterConfiguration};
+use key_server_cluster::message::{self, Message, GenerationMessage, EncryptionMessage, DecryptionMessage, SigningMessage};
+use key_server_cluster::generation_session::{Session as GenerationSession, SessionImpl as GenerationSessionImpl,
+	SessionParams as GenerationSessionParams, SessionState as GenerationSessionState};
+use key_server_cluster::decryption_session::{Session as DecryptionSession, SessionImpl as DecryptionSessionImpl,
+	DecryptionSessionId, SessionParams as DecryptionSessionParams};
+use key_server_cluster::encryption_session::{Session as EncryptionSession, SessionImpl as EncryptionSessionImpl,
+	SessionParams as EncryptionSessionParams, SessionState as EncryptionSessionState};
+use key_server_cluster::signing_session::{Session as SigningSession, SessionImpl as SigningSessionImpl,
+	SigningSessionId, SessionParams as SigningSessionParams};
+
+/// When there are no session-related messages for SESSION_TIMEOUT_INTERVAL seconds,
+/// we must treat this session as stalled && finish it with an error.
+/// This timeout is for cases when node is responding to KeepAlive messages, but intentionally ignores
+/// session messages.
+const SESSION_TIMEOUT_INTERVAL: u64 = 60;
+
+/// Generic cluster session.
+pub trait ClusterSession {
+	/// If session is finished (either with succcess or not).
+	fn is_finished(&self) -> bool;
+	/// When it takes too much time to complete session.
+	fn on_session_timeout(&self);
+	/// When it takes too much time to receive response from the node.
+	fn on_node_timeout(&self, node_id: &NodeId);
+}
+
+/// Active sessions on this cluster.
+pub struct ClusterSessions {
+	/// Key generation sessions.
+	pub generation_sessions: ClusterSessionsContainer<SessionId, GenerationSessionImpl, GenerationMessage>,
+	/// Encryption sessions.
+	pub encryption_sessions: ClusterSessionsContainer<SessionId, EncryptionSessionImpl, EncryptionMessage>,
+	/// Decryption sessions.
+	pub decryption_sessions: ClusterSessionsContainer<DecryptionSessionId, DecryptionSessionImpl, DecryptionMessage>,
+	/// Signing sessions.
+	pub signing_sessions: ClusterSessionsContainer<SigningSessionId, SigningSessionImpl, SigningMessage>,
+	/// Self node id.
+	self_node_id: NodeId,
+	/// All nodes ids.
+	nodes: BTreeSet<NodeId>,
+	/// Reference to key storage
+	key_storage: Arc<KeyStorage>,
+	/// Reference to ACL storage
+	acl_storage: Arc<AclStorage>,
+	/// Make faulty generation sessions.
+	make_faulty_generation_sessions: AtomicBool,
+}
+
+/// Active sessions container.
+pub struct ClusterSessionsContainer<K, V, M> {
+	/// Active sessions.
+	pub sessions: RwLock<BTreeMap<K, QueuedSession<V, M>>>,
+}
+
+/// Session and its message queue.
+pub struct QueuedSession<V, M> {
+	/// Session master.
+	pub master: NodeId,
+	/// Cluster view.
+	pub cluster_view: Arc<ClusterView>,
+	/// Last received message time.
+	pub last_message_time: time::Instant,
+	/// Generation session.
+	pub session: Arc<V>,
+	/// Messages queue.
+	pub queue: VecDeque<(NodeId, M)>,
+}
+
+/// Generation session implementation, which removes session from cluster on drop.
+pub struct GenerationSessionWrapper {
+	/// Wrapped session.
+	session: Arc<GenerationSession>,
+	/// Session Id.
+	session_id: SessionId,
+	/// Cluster data reference.
+	cluster: Weak<ClusterData>,
+}
+
+/// Encryption session implementation, which removes session from cluster on drop.
+pub struct EncryptionSessionWrapper {
+	/// Wrapped session.
+	session: Arc<EncryptionSession>,
+	/// Session Id.
+	session_id: SessionId,
+	/// Cluster data reference.
+	cluster: Weak<ClusterData>,
+}
+
+/// Decryption session implementation, which removes session from cluster on drop.
+pub struct DecryptionSessionWrapper {
+	/// Wrapped session.
+	session: Arc<DecryptionSession>,
+	/// Session Id.
+	session_id: DecryptionSessionId,
+	/// Cluster data reference.
+	cluster: Weak<ClusterData>,
+}
+
+/// Signing session implementation, which removes session from cluster on drop.
+pub struct SigningSessionWrapper {
+	/// Wrapped session.
+	session: Arc<SigningSession>,
+	/// Session Id.
+	session_id: SigningSessionId,
+	/// Cluster data reference.
+	cluster: Weak<ClusterData>,
+}
+
+impl ClusterSessions {
+	/// Create new cluster sessions container.
+	pub fn new(config: &ClusterConfiguration) -> Self {
+		ClusterSessions {
+			self_node_id: config.self_key_pair.public().clone(),
+			nodes: config.nodes.keys().cloned().collect(),
+			acl_storage: config.acl_storage.clone(),
+			key_storage: config.key_storage.clone(),
+			generation_sessions: ClusterSessionsContainer::new(),
+			encryption_sessions: ClusterSessionsContainer::new(),
+			decryption_sessions: ClusterSessionsContainer::new(),
+			signing_sessions: ClusterSessionsContainer::new(),
+			make_faulty_generation_sessions: AtomicBool::new(false),
+		}
+	}
+
+	#[cfg(test)]
+	pub fn make_faulty_generation_sessions(&self) {
+		self.make_faulty_generation_sessions.store(true, Ordering::Relaxed);
+	}
+
+	/// Create new generation session.
+	pub fn new_generation_session(&self, master: NodeId, session_id: SessionId, cluster: Arc<ClusterView>) -> Result<Arc<GenerationSessionImpl>, Error> {
+		// check that there's no finished encryption session with the same id
+		if self.key_storage.contains(&session_id) {
+			return Err(Error::DuplicateSessionId);
+		}
+		// communicating to all other nodes is crucial for encryption session
+		// => check that we have connections to all cluster nodes
+		if self.nodes.iter().any(|n| !cluster.is_connected(n)) {
+			return Err(Error::NodeDisconnected);
+		}
+
+		// check that there's no active encryption session with the same id
+		self.generation_sessions.insert(master, session_id, cluster.clone(), move ||
+			Ok(GenerationSessionImpl::new(GenerationSessionParams {
+				id: session_id.clone(),
+				self_node_id: self.self_node_id.clone(),
+				key_storage: Some(self.key_storage.clone()),
+				cluster: cluster,
+			})))
+			.map(|session| {
+				if self.make_faulty_generation_sessions.load(Ordering::Relaxed) {
+					session.simulate_faulty_behaviour();
+				}
+				session
+			})
+	}
+
+	/// Send generation session error.
+	pub fn respond_with_generation_error(&self, session_id: &SessionId, error: message::SessionError) {
+		self.generation_sessions.sessions.read().get(session_id)
+			.map(|s| {
+				// error in generation session is considered fatal
+				// => broadcast error
+
+				// do not bother processing send error, as we already processing error
+				let _ = s.cluster_view.broadcast(Message::Generation(GenerationMessage::SessionError(error)));
+			});
+	}
+
+	/// Create new encryption session.
+	pub fn new_encryption_session(&self, master: NodeId, session_id: SessionId, cluster: Arc<ClusterView>) -> Result<Arc<EncryptionSessionImpl>, Error> {
+		let encrypted_data = self.read_key_share(&session_id, &cluster)?;
+		self.encryption_sessions.insert(master, session_id, cluster.clone(), move || EncryptionSessionImpl::new(EncryptionSessionParams {
+			id: session_id.clone(),
+			self_node_id: self.self_node_id.clone(),
+			encrypted_data: encrypted_data,
+			key_storage: self.key_storage.clone(),
+			cluster: cluster,
+		}))
+	}
+
+	/// Send encryption session error.
+	pub fn respond_with_encryption_error(&self, session_id: &SessionId, error: message::EncryptionSessionError) {
+		self.encryption_sessions.sessions.read().get(session_id)
+			.map(|s| {
+				// error in encryption session is considered fatal
+				// => broadcast error
+
+				// do not bother processing send error, as we already processing error
+				let _ = s.cluster_view.broadcast(Message::Encryption(EncryptionMessage::EncryptionSessionError(error)));
+			});
+	}
+
+	/// Create new decryption session.
+	pub fn new_decryption_session(&self, master: NodeId, session_id: SessionId, sub_session_id: Secret, cluster: Arc<ClusterView>, requester_signature: Option<Signature>) -> Result<Arc<DecryptionSessionImpl>, Error> {
+		let session_id = DecryptionSessionId::new(session_id, sub_session_id);
+		let encrypted_data = self.read_key_share(&session_id.id, &cluster)?;
+
+		self.decryption_sessions.insert(master, session_id.clone(), cluster.clone(), move || DecryptionSessionImpl::new(DecryptionSessionParams {
+			meta: SessionMeta {
+				id: session_id.id,
+				self_node_id: self.self_node_id.clone(),
+				master_node_id: master,
+				threshold: encrypted_data.threshold,
+			},
+			access_key: session_id.access_key,
+			key_share: encrypted_data,
+			acl_storage: self.acl_storage.clone(),
+			cluster: cluster,
+		}, requester_signature))
+	}
+
+	/// Send decryption session error.
+	pub fn respond_with_decryption_error(&self, session_id: &SessionId, sub_session_id: &Secret, to: &NodeId, error: message::DecryptionSessionError) {
+		let session_id = DecryptionSessionId::new(session_id.clone(), sub_session_id.clone());
+		self.decryption_sessions.sessions.read().get(&session_id)
+			.map(|s| {
+				// error in decryption session is non-fatal, if occurs on slave node
+				// => either respond with error
+				// => or broadcast error
+
+				// do not bother processing send error, as we already processing error
+				if s.master == self.self_node_id {
+					let _ = s.cluster_view.broadcast(Message::Decryption(DecryptionMessage::DecryptionSessionError(error)));
+				} else {
+					let _ = s.cluster_view.send(to, Message::Decryption(DecryptionMessage::DecryptionSessionError(error)));
+				}
+			});
+	}
+
+	/// Create new signing session.
+	pub fn new_signing_session(&self, master: NodeId, session_id: SessionId, sub_session_id: Secret, cluster: Arc<ClusterView>, requester_signature: Option<Signature>) -> Result<Arc<SigningSessionImpl>, Error> {
+		let session_id = SigningSessionId::new(session_id, sub_session_id);
+		let encrypted_data = self.read_key_share(&session_id.id, &cluster)?;
+
+		self.signing_sessions.insert(master, session_id.clone(), cluster.clone(), move || SigningSessionImpl::new(SigningSessionParams {
+			meta: SessionMeta {
+				id: session_id.id,
+				self_node_id: self.self_node_id.clone(),
+				master_node_id: master,
+				threshold: encrypted_data.threshold,
+			},
+			access_key: session_id.access_key,
+			key_share: encrypted_data,
+			acl_storage: self.acl_storage.clone(),
+			cluster: cluster,
+		}, requester_signature))
+	}
+
+	/// Send signing session error.
+	pub fn respond_with_signing_error(&self, session_id: &SessionId, sub_session_id: &Secret, to: &NodeId, error: message::SigningSessionError) {
+		let session_id = SigningSessionId::new(session_id.clone(), sub_session_id.clone());
+		self.signing_sessions.sessions.read().get(&session_id)
+			.map(|s| {
+				// error in signing session is non-fatal, if occurs on slave node
+				// => either respond with error
+				// => or broadcast error
+
+				// do not bother processing send error, as we already processing error
+				if s.master == self.self_node_id {
+					let _ = s.cluster_view.broadcast(Message::Signing(SigningMessage::SigningSessionError(error)));
+				} else {
+					let _ = s.cluster_view.send(to, Message::Signing(SigningMessage::SigningSessionError(error)));
+				}
+			});
+	}
+
+	/// Stop sessions that are stalling.
+	pub fn stop_stalled_sessions(&self) {
+		self.generation_sessions.stop_stalled_sessions();
+		self.encryption_sessions.stop_stalled_sessions();
+		self.decryption_sessions.stop_stalled_sessions();
+		self.signing_sessions.stop_stalled_sessions();
+	}
+
+	/// When connection to node is lost.
+	pub fn on_connection_timeout(&self, node_id: &NodeId) {
+		self.generation_sessions.on_connection_timeout(node_id);
+		self.encryption_sessions.on_connection_timeout(node_id);
+		self.decryption_sessions.on_connection_timeout(node_id);
+		self.signing_sessions.on_connection_timeout(node_id);
+	}
+
+	/// Read key share && remove disconnected nodes.
+	fn read_key_share(&self, key_id: &SessionId, cluster: &Arc<ClusterView>) -> Result<DocumentKeyShare, Error> {
+		let mut encrypted_data = self.key_storage.get(key_id).map_err(|e| Error::KeyStorage(e.into()))?;
+
+		// some of nodes, which were encrypting secret may be down
+		// => do not use these in session
+		let disconnected_nodes: BTreeSet<_> = encrypted_data.id_numbers.keys().cloned().collect();
+		for disconnected_node in disconnected_nodes.difference(&cluster.nodes()) {
+			encrypted_data.id_numbers.remove(&disconnected_node);
+		}
+		Ok(encrypted_data)
+	}
+}
+
+impl<K, V, M> ClusterSessionsContainer<K, V, M> where K: Clone + Ord, V: ClusterSession {
+	pub fn new() -> Self {
+		ClusterSessionsContainer {
+			sessions: RwLock::new(BTreeMap::new()),
+		}
+	}
+
+	pub fn get(&self, session_id: &K) -> Option<Arc<V>> {
+		self.sessions.read().get(session_id).map(|s| s.session.clone())
+	}
+
+	pub fn insert<F: FnOnce() -> Result<V, Error>>(&self, master: NodeId, session_id: K, cluster: Arc<ClusterView>, session: F) -> Result<Arc<V>, Error> {
+		let mut sessions = self.sessions.write();
+		if sessions.contains_key(&session_id) {
+			return Err(Error::DuplicateSessionId);
+		}
+
+		let session = Arc::new(session()?);
+		let queued_session = QueuedSession {
+			master: master,
+			cluster_view: cluster,
+			last_message_time: time::Instant::now(),
+			session: session.clone(),
+			queue: VecDeque::new(),
+		};
+		sessions.insert(session_id, queued_session);
+		Ok(session)
+	}
+
+	pub fn remove(&self, session_id: &K) {
+		self.sessions.write().remove(session_id);
+	}
+
+	pub fn enqueue_message(&self, session_id: &K, sender: NodeId, message: M, is_queued_message: bool) {
+		self.sessions.write().get_mut(session_id)
+			.map(|session| if is_queued_message { session.queue.push_front((sender, message)) }
+				else { session.queue.push_back((sender, message)) });
+	}
+
+	pub fn dequeue_message(&self, session_id: &K) -> Option<(NodeId, M)> {
+		self.sessions.write().get_mut(session_id)
+			.and_then(|session| session.queue.pop_front())
+	}
+
+	pub fn stop_stalled_sessions(&self) {
+		let mut sessions = self.sessions.write();
+		for sid in sessions.keys().cloned().collect::<Vec<_>>() {
+			let remove_session = {
+				let session = sessions.get(&sid).expect("enumerating only existing sessions; qed");
+				if time::Instant::now() - session.last_message_time > time::Duration::from_secs(SESSION_TIMEOUT_INTERVAL) {
+					session.session.on_session_timeout();
+					session.session.is_finished()
+				} else {
+					false
+				}
+			};
+
+			if remove_session {
+				sessions.remove(&sid);
+			}
+		}
+	}
+
+	pub fn on_connection_timeout(&self, node_id: &NodeId) {
+		let mut sessions = self.sessions.write();
+		for sid in sessions.keys().cloned().collect::<Vec<_>>() {
+			let remove_session = {
+				let session = sessions.get(&sid).expect("enumerating only existing sessions; qed");
+				session.session.on_node_timeout(node_id);
+				session.session.is_finished()
+			};
+			if remove_session {
+				sessions.remove(&sid);
+			}
+		}
+	}
+}
+
+impl GenerationSessionWrapper {
+	pub fn new(cluster: Weak<ClusterData>, session_id: SessionId, session: Arc<GenerationSession>) -> Arc<Self> {
+		Arc::new(GenerationSessionWrapper {
+			session: session,
+			session_id: session_id,
+			cluster: cluster,
+		})
+	}
+}
+
+impl GenerationSession for GenerationSessionWrapper {
+	fn state(&self) -> GenerationSessionState {
+		self.session.state()
+	}
+
+	fn wait(&self, timeout: Option<time::Duration>) -> Result<Public, Error> {
+		self.session.wait(timeout)
+	}
+
+	fn joint_public_and_secret(&self) -> Option<Result<(Public, Secret), Error>> {
+		self.session.joint_public_and_secret()
+	}
+}
+
+impl Drop for GenerationSessionWrapper {
+	fn drop(&mut self) {
+		if let Some(cluster) = self.cluster.upgrade() {
+			cluster.sessions().generation_sessions.remove(&self.session_id);
+		}
+	}
+}
+
+impl EncryptionSessionWrapper {
+	pub fn new(cluster: Weak<ClusterData>, session_id: SessionId, session: Arc<EncryptionSession>) -> Arc<Self> {
+		Arc::new(EncryptionSessionWrapper {
+			session: session,
+			session_id: session_id,
+			cluster: cluster,
+		})
+	}
+}
+
+impl EncryptionSession for EncryptionSessionWrapper {
+	fn state(&self) -> EncryptionSessionState {
+		self.session.state()
+	}
+
+	fn wait(&self, timeout: Option<time::Duration>) -> Result<(), Error> {
+		self.session.wait(timeout)
+	}
+}
+
+impl Drop for EncryptionSessionWrapper {
+	fn drop(&mut self) {
+		if let Some(cluster) = self.cluster.upgrade() {
+			cluster.sessions().encryption_sessions.remove(&self.session_id);
+		}
+	}
+}
+
+impl DecryptionSessionWrapper {
+	pub fn new(cluster: Weak<ClusterData>, session_id: DecryptionSessionId, session: Arc<DecryptionSession>) -> Arc<Self> {
+		Arc::new(DecryptionSessionWrapper {
+			session: session,
+			session_id: session_id,
+			cluster: cluster,
+		})
+	}
+}
+
+impl DecryptionSession for DecryptionSessionWrapper {
+	fn wait(&self) -> Result<EncryptedDocumentKeyShadow, Error> {
+		self.session.wait()
+	}
+}
+
+impl Drop for DecryptionSessionWrapper {
+	fn drop(&mut self) {
+		if let Some(cluster) = self.cluster.upgrade() {
+			cluster.sessions().decryption_sessions.remove(&self.session_id);
+		}
+	}
+}
+
+impl SigningSessionWrapper {
+	pub fn new(cluster: Weak<ClusterData>, session_id: SigningSessionId, session: Arc<SigningSession>) -> Arc<Self> {
+		Arc::new(SigningSessionWrapper {
+			session: session,
+			session_id: session_id,
+			cluster: cluster,
+		})
+	}
+}
+
+impl SigningSession for SigningSessionWrapper {
+	fn wait(&self) -> Result<(Secret, Secret), Error> {
+		self.session.wait()
+	}
+}
+
+impl Drop for SigningSessionWrapper {
+	fn drop(&mut self) {
+		if let Some(cluster) = self.cluster.upgrade() {
+			cluster.sessions().signing_sessions.remove(&self.session_id);
+		}
+	}
+}

secret_store/src/key_server_cluster/io/message.rs

@@ -25,7 +25,8 @@ use ethkey::{Public, Secret, KeyPair};
 use ethkey::math::curve_order;
 use util::{H256, U256};
 use key_server_cluster::Error;
-use key_server_cluster::message::{Message, ClusterMessage, EncryptionMessage, DecryptionMessage};
+use key_server_cluster::message::{Message, ClusterMessage, GenerationMessage, EncryptionMessage,
+	DecryptionMessage, SigningMessage};
 
 /// Size of serialized header.
 pub const MESSAGE_HEADER_SIZE: usize = 4;
@@ -67,20 +68,30 @@ pub fn serialize_message(message: Message) -> Result<SerializedMessage, Error> {
 		Message::Cluster(ClusterMessage::KeepAlive(payload))								=> (3, serde_json::to_vec(&payload)),
 		Message::Cluster(ClusterMessage::KeepAliveResponse(payload))						=> (4, serde_json::to_vec(&payload)),
 
-		Message::Encryption(EncryptionMessage::InitializeSession(payload))					=> (50, serde_json::to_vec(&payload)),
+		Message::Generation(GenerationMessage::InitializeSession(payload))					=> (50, serde_json::to_vec(&payload)),
-		Message::Encryption(EncryptionMessage::ConfirmInitialization(payload))				=> (51, serde_json::to_vec(&payload)),
+		Message::Generation(GenerationMessage::ConfirmInitialization(payload))				=> (51, serde_json::to_vec(&payload)),
-		Message::Encryption(EncryptionMessage::CompleteInitialization(payload))				=> (52, serde_json::to_vec(&payload)),
+		Message::Generation(GenerationMessage::CompleteInitialization(payload))				=> (52, serde_json::to_vec(&payload)),
-		Message::Encryption(EncryptionMessage::KeysDissemination(payload))					=> (53, serde_json::to_vec(&payload)),
+		Message::Generation(GenerationMessage::KeysDissemination(payload))					=> (53, serde_json::to_vec(&payload)),
-		Message::Encryption(EncryptionMessage::PublicKeyShare(payload))						=> (54, serde_json::to_vec(&payload)),
+		Message::Generation(GenerationMessage::PublicKeyShare(payload))						=> (54, serde_json::to_vec(&payload)),
-		Message::Encryption(EncryptionMessage::SessionError(payload))						=> (55, serde_json::to_vec(&payload)),
+		Message::Generation(GenerationMessage::SessionError(payload))						=> (55, serde_json::to_vec(&payload)),
-		Message::Encryption(EncryptionMessage::SessionCompleted(payload))					=> (56, serde_json::to_vec(&payload)),
+		Message::Generation(GenerationMessage::SessionCompleted(payload))					=> (56, serde_json::to_vec(&payload)),
 
-		Message::Decryption(DecryptionMessage::InitializeDecryptionSession(payload))		=> (100, serde_json::to_vec(&payload)),
+		Message::Encryption(EncryptionMessage::InitializeEncryptionSession(payload))		=> (100, serde_json::to_vec(&payload)),
-		Message::Decryption(DecryptionMessage::ConfirmDecryptionInitialization(payload))	=> (101, serde_json::to_vec(&payload)),
+		Message::Encryption(EncryptionMessage::ConfirmEncryptionInitialization(payload))	=> (101, serde_json::to_vec(&payload)),
-		Message::Decryption(DecryptionMessage::RequestPartialDecryption(payload))			=> (102, serde_json::to_vec(&payload)),
+		Message::Encryption(EncryptionMessage::EncryptionSessionError(payload))				=> (102, serde_json::to_vec(&payload)),
-		Message::Decryption(DecryptionMessage::PartialDecryption(payload))					=> (103, serde_json::to_vec(&payload)),
+
-		Message::Decryption(DecryptionMessage::DecryptionSessionError(payload))				=> (104, serde_json::to_vec(&payload)),
+		Message::Decryption(DecryptionMessage::DecryptionConsensusMessage(payload))			=> (150, serde_json::to_vec(&payload)),
-		Message::Decryption(DecryptionMessage::DecryptionSessionCompleted(payload))			=> (105, serde_json::to_vec(&payload)),
+		Message::Decryption(DecryptionMessage::RequestPartialDecryption(payload))			=> (151, serde_json::to_vec(&payload)),
+		Message::Decryption(DecryptionMessage::PartialDecryption(payload))					=> (152, serde_json::to_vec(&payload)),
+		Message::Decryption(DecryptionMessage::DecryptionSessionError(payload))				=> (153, serde_json::to_vec(&payload)),
+		Message::Decryption(DecryptionMessage::DecryptionSessionCompleted(payload))			=> (154, serde_json::to_vec(&payload)),
+
+		Message::Signing(SigningMessage::SigningConsensusMessage(payload))					=> (200, serde_json::to_vec(&payload)),
+		Message::Signing(SigningMessage::SigningGenerationMessage(payload))					=> (201, serde_json::to_vec(&payload)),
+		Message::Signing(SigningMessage::RequestPartialSignature(payload))					=> (202, serde_json::to_vec(&payload)),
+		Message::Signing(SigningMessage::PartialSignature(payload))							=> (203, serde_json::to_vec(&payload)),
+		Message::Signing(SigningMessage::SigningSessionError(payload))						=> (204, serde_json::to_vec(&payload)),
+		Message::Signing(SigningMessage::SigningSessionCompleted(payload))					=> (205, serde_json::to_vec(&payload)),
 	};
 
 	let payload = payload.map_err(|err| Error::Serde(err.to_string()))?;
@@ -99,20 +110,30 @@ pub fn deserialize_message(header: &MessageHeader, payload: Vec<u8>) -> Result<M
 		3	=> Message::Cluster(ClusterMessage::KeepAlive(serde_json::from_slice(&payload).map_err(|err| Error::Serde(err.to_string()))?)),
 		4	=> Message::Cluster(ClusterMessage::KeepAliveResponse(serde_json::from_slice(&payload).map_err(|err| Error::Serde(err.to_string()))?)),
 
-		50	=> Message::Encryption(EncryptionMessage::InitializeSession(serde_json::from_slice(&payload).map_err(|err| Error::Serde(err.to_string()))?)),
+		50	=> Message::Generation(GenerationMessage::InitializeSession(serde_json::from_slice(&payload).map_err(|err| Error::Serde(err.to_string()))?)),
-		51	=> Message::Encryption(EncryptionMessage::ConfirmInitialization(serde_json::from_slice(&payload).map_err(|err| Error::Serde(err.to_string()))?)),
+		51	=> Message::Generation(GenerationMessage::ConfirmInitialization(serde_json::from_slice(&payload).map_err(|err| Error::Serde(err.to_string()))?)),
-		52	=> Message::Encryption(EncryptionMessage::CompleteInitialization(serde_json::from_slice(&payload).map_err(|err| Error::Serde(err.to_string()))?)),
+		52	=> Message::Generation(GenerationMessage::CompleteInitialization(serde_json::from_slice(&payload).map_err(|err| Error::Serde(err.to_string()))?)),
-		53	=> Message::Encryption(EncryptionMessage::KeysDissemination(serde_json::from_slice(&payload).map_err(|err| Error::Serde(err.to_string()))?)),
+		53	=> Message::Generation(GenerationMessage::KeysDissemination(serde_json::from_slice(&payload).map_err(|err| Error::Serde(err.to_string()))?)),
-		54	=> Message::Encryption(EncryptionMessage::PublicKeyShare(serde_json::from_slice(&payload).map_err(|err| Error::Serde(err.to_string()))?)),
+		54	=> Message::Generation(GenerationMessage::PublicKeyShare(serde_json::from_slice(&payload).map_err(|err| Error::Serde(err.to_string()))?)),
-		55	=> Message::Encryption(EncryptionMessage::SessionError(serde_json::from_slice(&payload).map_err(|err| Error::Serde(err.to_string()))?)),
+		55	=> Message::Generation(GenerationMessage::SessionError(serde_json::from_slice(&payload).map_err(|err| Error::Serde(err.to_string()))?)),
-		56	=> Message::Encryption(EncryptionMessage::SessionCompleted(serde_json::from_slice(&payload).map_err(|err| Error::Serde(err.to_string()))?)),
+		56	=> Message::Generation(GenerationMessage::SessionCompleted(serde_json::from_slice(&payload).map_err(|err| Error::Serde(err.to_string()))?)),
 
-		100	=> Message::Decryption(DecryptionMessage::InitializeDecryptionSession(serde_json::from_slice(&payload).map_err(|err| Error::Serde(err.to_string()))?)),
+		100	=> Message::Encryption(EncryptionMessage::InitializeEncryptionSession(serde_json::from_slice(&payload).map_err(|err| Error::Serde(err.to_string()))?)),
-		101	=> Message::Decryption(DecryptionMessage::ConfirmDecryptionInitialization(serde_json::from_slice(&payload).map_err(|err| Error::Serde(err.to_string()))?)),
+		101	=> Message::Encryption(EncryptionMessage::ConfirmEncryptionInitialization(serde_json::from_slice(&payload).map_err(|err| Error::Serde(err.to_string()))?)),
-		102	=> Message::Decryption(DecryptionMessage::RequestPartialDecryption(serde_json::from_slice(&payload).map_err(|err| Error::Serde(err.to_string()))?)),
+		102	=> Message::Encryption(EncryptionMessage::EncryptionSessionError(serde_json::from_slice(&payload).map_err(|err| Error::Serde(err.to_string()))?)),
-		103	=> Message::Decryption(DecryptionMessage::PartialDecryption(serde_json::from_slice(&payload).map_err(|err| Error::Serde(err.to_string()))?)),
+
-		104	=> Message::Decryption(DecryptionMessage::DecryptionSessionError(serde_json::from_slice(&payload).map_err(|err| Error::Serde(err.to_string()))?)),
+		150	=> Message::Decryption(DecryptionMessage::DecryptionConsensusMessage(serde_json::from_slice(&payload).map_err(|err| Error::Serde(err.to_string()))?)),
-		105	=> Message::Decryption(DecryptionMessage::DecryptionSessionCompleted(serde_json::from_slice(&payload).map_err(|err| Error::Serde(err.to_string()))?)),
+		151	=> Message::Decryption(DecryptionMessage::RequestPartialDecryption(serde_json::from_slice(&payload).map_err(|err| Error::Serde(err.to_string()))?)),
+		152	=> Message::Decryption(DecryptionMessage::PartialDecryption(serde_json::from_slice(&payload).map_err(|err| Error::Serde(err.to_string()))?)),
+		153	=> Message::Decryption(DecryptionMessage::DecryptionSessionError(serde_json::from_slice(&payload).map_err(|err| Error::Serde(err.to_string()))?)),
+		154	=> Message::Decryption(DecryptionMessage::DecryptionSessionCompleted(serde_json::from_slice(&payload).map_err(|err| Error::Serde(err.to_string()))?)),
+
+		200	=> Message::Signing(SigningMessage::SigningConsensusMessage(serde_json::from_slice(&payload).map_err(|err| Error::Serde(err.to_string()))?)),
+		201	=> Message::Signing(SigningMessage::SigningGenerationMessage(serde_json::from_slice(&payload).map_err(|err| Error::Serde(err.to_string()))?)),
+		202	=> Message::Signing(SigningMessage::RequestPartialSignature(serde_json::from_slice(&payload).map_err(|err| Error::Serde(err.to_string()))?)),
+		203	=> Message::Signing(SigningMessage::PartialSignature(serde_json::from_slice(&payload).map_err(|err| Error::Serde(err.to_string()))?)),
+		204	=> Message::Signing(SigningMessage::SigningSessionError(serde_json::from_slice(&payload).map_err(|err| Error::Serde(err.to_string()))?)),
+		205	=> Message::Signing(SigningMessage::SigningSessionCompleted(serde_json::from_slice(&payload).map_err(|err| Error::Serde(err.to_string()))?)),
 
 		_ => return Err(Error::Serde(format!("unknown message type {}", header.kind))),
 	})

secret_store/src/key_server_cluster/jobs/consensus_session.rs

@@ -0,0 +1,756 @@
+// Copyright 2015-2017 Parity Technologies (UK) Ltd.
+// This file is part of Parity.
+
+// Parity is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Parity is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Parity.  If not, see <http://www.gnu.org/licenses/>.
+
+use std::collections::BTreeSet;
+use std::sync::Arc;
+use ethkey::{Public, Signature, recover};
+use key_server_cluster::{Error, NodeId, SessionMeta, AclStorage};
+use key_server_cluster::message::ConsensusMessage;
+use key_server_cluster::jobs::job_session::{JobSession, JobSessionState, JobTransport, JobExecutor};
+use key_server_cluster::jobs::key_access_job::KeyAccessJob;
+
+/// Consensus session state.
+#[derive(Debug, Clone, Copy, PartialEq)]
+pub enum ConsensusSessionState {
+	/// Every node starts in this state.
+	WaitingForInitialization,
+	/// Consensus group is establishing.
+	EstablishingConsensus,
+	/// Consensus group is established.
+	/// Master node can start jobs dissemination.
+	/// Slave node waits for partial job requests.
+	ConsensusEstablished,
+	/// Master node waits for partial jobs responses.
+	WaitingForPartialResults,
+	/// Consensus session is completed successfully.
+	/// Master node can call result() to get computation result.
+	Finished,
+	/// Consensus session has failed with error.
+	Failed,
+}
+
+/// Consensus session consists of following states:
+/// 1) consensus group is established
+/// 2) master node sends partial job requests to every member of consensus group
+/// 3) slave nodes are computing partial responses
+/// 4) master node computes result from partial responses
+pub struct ConsensusSession<ConsensusTransport: JobTransport<PartialJobRequest=Signature, PartialJobResponse=bool>, ComputationExecutor: JobExecutor, ComputationTransport: JobTransport<PartialJobRequest=ComputationExecutor::PartialJobRequest, PartialJobResponse=ComputationExecutor::PartialJobResponse>> {
+	/// Current session state.
+	state: ConsensusSessionState,
+	/// Session metadata.
+	meta: SessionMeta,
+	/// Requester, for which consensus group has allowed access.
+	requester: Option<Public>,
+	/// Consensus establish job.
+	consensus_job: JobSession<KeyAccessJob, ConsensusTransport>,
+	/// Consensus group.
+	consensus_group: BTreeSet<NodeId>,
+	/// Computation job.
+	computation_job: Option<JobSession<ComputationExecutor, ComputationTransport>>,
+}
+
+/// Consensus session creation parameters.
+pub struct ConsensusSessionParams<ConsensusTransport: JobTransport<PartialJobRequest=Signature, PartialJobResponse=bool>> {
+	/// Session metadata.
+	pub meta: SessionMeta,
+	/// ACL storage for access check.
+	pub acl_storage: Arc<AclStorage>,
+	/// Transport for consensus establish job.
+	pub consensus_transport: ConsensusTransport,
+}
+
+impl<ConsensusTransport, ComputationExecutor, ComputationTransport> ConsensusSession<ConsensusTransport, ComputationExecutor, ComputationTransport> where ConsensusTransport: JobTransport<PartialJobRequest=Signature, PartialJobResponse=bool>, ComputationExecutor: JobExecutor, ComputationTransport: JobTransport<PartialJobRequest=ComputationExecutor::PartialJobRequest, PartialJobResponse=ComputationExecutor::PartialJobResponse> {
+	/// Create new consensus session on slave node.
+	pub fn new_on_slave(params: ConsensusSessionParams<ConsensusTransport>) -> Result<Self, Error> {
+		debug_assert!(params.meta.self_node_id != params.meta.master_node_id);
+		Self::new(None, KeyAccessJob::new_on_slave(params.meta.id.clone(), params.acl_storage.clone()), params)
+	}
+
+	/// Create new consensus session on master node.
+	pub fn new_on_master(params: ConsensusSessionParams<ConsensusTransport>, signature: Signature) -> Result<Self, Error> {
+		debug_assert!(params.meta.self_node_id == params.meta.master_node_id);
+		Self::new(Some(recover(&signature, &params.meta.id)?),
+			KeyAccessJob::new_on_master(params.meta.id.clone(), params.acl_storage.clone(), signature), params)
+	}
+
+	/// Create new consensus session.
+	fn new(requester: Option<Public>, consensus_job_executor: KeyAccessJob, params: ConsensusSessionParams<ConsensusTransport>) -> Result<Self, Error> {
+		let consensus_job = JobSession::new(params.meta.clone(), consensus_job_executor, params.consensus_transport);
+		debug_assert!(consensus_job.state() == JobSessionState::Inactive);
+
+		Ok(ConsensusSession {
+			state: ConsensusSessionState::WaitingForInitialization,
+			meta: params.meta,
+			requester: requester,
+			consensus_job: consensus_job,
+			consensus_group: BTreeSet::new(),
+			computation_job: None,
+		})
+	}
+
+	/// Get consensus job reference.
+	#[cfg(test)]
+	pub fn consensus_job(&self) -> &JobSession<KeyAccessJob, ConsensusTransport> {
+		&self.consensus_job
+	}
+
+	/// Get computation job reference.
+	#[cfg(test)]
+	pub fn computation_job(&self) -> &JobSession<ComputationExecutor, ComputationTransport> {
+		self.computation_job.as_ref()
+			.expect("computation_job must only be called on master nodes")
+	}
+
+	/// Get consensus session state.
+	pub fn state(&self) -> ConsensusSessionState {
+		self.state
+	}
+
+	/// Get requester, for which consensus has been reached.
+	pub fn requester(&self) -> Result<&Public, Error> {
+		self.requester.as_ref().ok_or(Error::InvalidStateForRequest)
+	}
+
+	/// Get computation result.
+	pub fn result(&self) -> Result<ComputationExecutor::JobResponse, Error> {
+		debug_assert!(self.meta.self_node_id == self.meta.master_node_id);
+		if self.state != ConsensusSessionState::Finished {
+			return Err(Error::InvalidStateForRequest);
+		}
+
+		self.computation_job.as_ref()
+			.expect("we are on master node in finished state; computation_job is set on master node during initialization; qed")
+			.result()
+	}
+
+	/// Initialize session on master node.
+	pub fn initialize(&mut self, nodes: BTreeSet<NodeId>) -> Result<(), Error> {
+		debug_assert!(self.meta.self_node_id == self.meta.master_node_id);
+		let initialization_result = self.consensus_job.initialize(nodes);
+		self.state = ConsensusSessionState::EstablishingConsensus;
+		self.process_result(initialization_result)
+	}
+
+	/// Process consensus message.
+	pub fn on_consensus_message(&mut self, sender: &NodeId, message: &ConsensusMessage) -> Result<(), Error> {
+		let consensus_result = match message {
+			&ConsensusMessage::InitializeConsensusSession(ref message) => {
+				let signature = message.requestor_signature.clone().into();
+				self.requester = Some(recover(&signature, &self.meta.id)?);
+				self.consensus_job.on_partial_request(sender, signature)
+			},
+			&ConsensusMessage::ConfirmConsensusInitialization(ref message) =>
+				self.consensus_job.on_partial_response(sender, message.is_confirmed),
+		};
+		self.process_result(consensus_result)
+	}
+
+	/// Select nodes for processing partial requests.
+	pub fn select_consensus_group(&mut self) -> Result<&BTreeSet<NodeId>, Error> {
+		debug_assert!(self.meta.self_node_id == self.meta.master_node_id);
+		if self.state != ConsensusSessionState::ConsensusEstablished {
+			return Err(Error::InvalidStateForRequest);
+		}
+
+		if self.consensus_group.is_empty() {
+			let consensus_group = self.consensus_job.result()?;
+			let is_self_in_consensus = consensus_group.contains(&self.meta.self_node_id);
+			self.consensus_group = consensus_group.into_iter().take(self.meta.threshold + 1).collect();
+
+			if is_self_in_consensus {
+				self.consensus_group.remove(&self.meta.master_node_id);
+				self.consensus_group.insert(self.meta.master_node_id.clone());
+			}
+		}
+
+		Ok(&self.consensus_group)
+	}
+
+	/// Disseminate jobs from master node.
+	pub fn disseminate_jobs(&mut self, executor: ComputationExecutor, transport: ComputationTransport) -> Result<(), Error> {
+		let consensus_group = self.select_consensus_group()?.clone();
+		self.consensus_group.clear();
+
+		let mut computation_job = JobSession::new(self.meta.clone(), executor, transport);
+		let computation_result = computation_job.initialize(consensus_group);
+		self.computation_job = Some(computation_job);
+		self.state = ConsensusSessionState::WaitingForPartialResults;
+		self.process_result(computation_result)
+	}
+
+	/// Process job request on slave node.
+	pub fn on_job_request(&mut self, node: &NodeId, request: ComputationExecutor::PartialJobRequest, executor: ComputationExecutor, transport: ComputationTransport) -> Result<(), Error> {
+		if &self.meta.master_node_id != node {
+			return Err(Error::InvalidMessage);
+		}
+		if self.state != ConsensusSessionState::ConsensusEstablished {
+			return Err(Error::InvalidStateForRequest);
+		}
+
+		JobSession::new(self.meta.clone(), executor, transport).on_partial_request(node, request)
+	}
+
+	/// Process job response on slave node.
+	pub fn on_job_response(&mut self, node: &NodeId, response: ComputationExecutor::PartialJobResponse) -> Result<(), Error> {
+		if self.state != ConsensusSessionState::WaitingForPartialResults {
+			return Err(Error::InvalidStateForRequest);
+		}
+
+		let computation_result = self.computation_job.as_mut()
+			.expect("WaitingForPartialResults is only set when computation_job is created; qed")
+			.on_partial_response(node, response);
+		self.process_result(computation_result)
+	}
+
+	/// When session is completed on slave node.
+	pub fn on_session_completed(&mut self, node: &NodeId) -> Result<(), Error> {
+		if node != &self.meta.master_node_id {
+			return Err(Error::InvalidMessage);
+		}
+		if self.state != ConsensusSessionState::ConsensusEstablished {
+			return Err(Error::InvalidStateForRequest);
+		}
+
+		self.state = ConsensusSessionState::Finished;
+
+		Ok(())
+	}
+
+	/// When error is received from node.
+	pub fn on_node_error(&mut self, node: &NodeId) -> Result<bool, Error> {
+		let is_self_master = self.meta.master_node_id == self.meta.self_node_id;
+		let is_node_master = self.meta.master_node_id == *node;
+		let (is_restart_needed, timeout_result) = match self.state {
+			ConsensusSessionState::WaitingForInitialization if is_self_master => {
+				// it is strange to receive error before session is initialized && slave doesn't know access_key
+				// => ignore this error for now
+				(false, Ok(()))
+			}
+			ConsensusSessionState::WaitingForInitialization if is_node_master => {
+				// can not establish consensus
+				// => fatal error
+				self.state = ConsensusSessionState::Failed;
+				(false, Err(Error::ConsensusUnreachable))
+			},
+			ConsensusSessionState::EstablishingConsensus => {
+				debug_assert!(is_self_master);
+
+				// consensus still can be established
+				// => try to live without this node
+				(false, self.consensus_job.on_node_error(node))
+			},
+			ConsensusSessionState::ConsensusEstablished => {
+				// we could try to continue without this node, if enough nodes left
+				(false, self.consensus_job.on_node_error(node))
+			},
+			ConsensusSessionState::WaitingForPartialResults => {
+				// check if *current* computation job can continue without this node
+				let is_computation_node = self.computation_job.as_mut()
+					.expect("WaitingForPartialResults state is only set when computation_job is created; qed")
+					.on_node_error(node)
+					.is_err();
+				if !is_computation_node {
+					// it is not used by current computation job
+					// => no restart required
+					(false, Ok(()))
+				} else {
+					// it is used by current computation job
+					// => restart is required if there are still enough nodes
+					self.consensus_group.clear();
+					self.state = ConsensusSessionState::EstablishingConsensus;
+
+					let consensus_result = self.consensus_job.on_node_error(node);
+					let is_consensus_established = self.consensus_job.state() == JobSessionState::Finished;
+					(is_consensus_established, consensus_result)
+				}
+			},
+			// in all other cases - just ignore error
+			ConsensusSessionState::WaitingForInitialization | ConsensusSessionState::Failed | ConsensusSessionState::Finished => (false, Ok(())),
+		};
+		self.process_result(timeout_result)?;
+		Ok(is_restart_needed)
+	}
+
+	/// When session is timeouted.
+	pub fn on_session_timeout(&mut self) -> Result<bool, Error> {
+		match self.state {
+			// if we are waiting for results from slaves, there is a chance to send request to other nodes subset => fall through
+			ConsensusSessionState::WaitingForPartialResults => (),
+			// in some states this error is fatal
+			ConsensusSessionState::WaitingForInitialization | ConsensusSessionState::EstablishingConsensus | ConsensusSessionState::ConsensusEstablished => {
+				let _ = self.consensus_job.on_session_timeout();
+
+				self.consensus_group.clear();
+				self.state = ConsensusSessionState::EstablishingConsensus;
+				return self.process_result(Err(Error::ConsensusUnreachable)).map(|_| unreachable!());
+			},
+			// in all other cases - just ignore error
+			ConsensusSessionState::Finished | ConsensusSessionState::Failed => return Ok(false),
+		};
+
+		let timeouted_nodes = self.computation_job.as_ref()
+			.expect("WaitingForPartialResults state is only set when computation_job is created; qed")
+			.requests()
+			.clone();
+		assert!(!timeouted_nodes.is_empty()); // timeout should not ever happen if no requests are active && we are waiting for responses
+
+		self.consensus_group.clear();
+		for timeouted_node in timeouted_nodes {
+			let timeout_result = self.consensus_job.on_node_error(&timeouted_node);
+			self.state = ConsensusSessionState::EstablishingConsensus;
+			self.process_result(timeout_result)?;
+		}
+
+		Ok(self.state == ConsensusSessionState::ConsensusEstablished)
+	}
+
+	/// Process result of job.
+	fn process_result(&mut self, result: Result<(), Error>) -> Result<(), Error> {
+		match self.state {
+			ConsensusSessionState::WaitingForInitialization | ConsensusSessionState::EstablishingConsensus | ConsensusSessionState::ConsensusEstablished => match self.consensus_job.state() {
+				JobSessionState::Finished => self.state = ConsensusSessionState::ConsensusEstablished,
+				JobSessionState::Failed => self.state = ConsensusSessionState::Failed,
+				_ => (),
+			},
+			ConsensusSessionState::WaitingForPartialResults => match self.computation_job.as_ref()
+				.expect("WaitingForPartialResults state is only set when computation_job is created; qed")
+				.state() {
+				JobSessionState::Finished => self.state = ConsensusSessionState::Finished,
+				JobSessionState::Failed => self.state = ConsensusSessionState::Failed,
+				_ => (),
+			},
+			_ => (),
+		}
+
+		result
+	}
+}
+
+#[cfg(test)]
+mod tests {
+	use std::sync::Arc;
+	use ethkey::{Signature, KeyPair, Random, Generator, sign};
+	use key_server_cluster::{Error, NodeId, SessionId, DummyAclStorage};
+	use key_server_cluster::message::{ConsensusMessage, InitializeConsensusSession, ConfirmConsensusInitialization};
+	use key_server_cluster::jobs::job_session::tests::{make_master_session_meta, make_slave_session_meta, SquaredSumJobExecutor, DummyJobTransport};
+	use super::{ConsensusSession, ConsensusSessionParams, ConsensusSessionState};
+
+	type SquaredSumConsensusSession = ConsensusSession<DummyJobTransport<Signature, bool>, SquaredSumJobExecutor, DummyJobTransport<u32, u32>>;
+
+	fn make_master_consensus_session(threshold: usize, requester: Option<KeyPair>, acl_storage: Option<DummyAclStorage>) -> SquaredSumConsensusSession {
+		let secret = requester.map(|kp| kp.secret().clone()).unwrap_or(Random.generate().unwrap().secret().clone());
+		SquaredSumConsensusSession::new_on_master(ConsensusSessionParams {
+			meta: make_master_session_meta(threshold),
+			acl_storage: Arc::new(acl_storage.unwrap_or(DummyAclStorage::default())),
+			consensus_transport: DummyJobTransport::default(),
+		}, sign(&secret, &SessionId::default()).unwrap()).unwrap()
+	}
+
+	fn make_slave_consensus_session(threshold: usize, acl_storage: Option<DummyAclStorage>) -> SquaredSumConsensusSession {
+		SquaredSumConsensusSession::new_on_slave(ConsensusSessionParams {
+			meta: make_slave_session_meta(threshold),
+			acl_storage: Arc::new(acl_storage.unwrap_or(DummyAclStorage::default())),
+			consensus_transport: DummyJobTransport::default(),
+		}).unwrap()
+	}
+
+	#[test]
+	fn consensus_session_consensus_is_not_reached_when_initializes_with_non_zero_threshold() {
+		let mut session = make_master_consensus_session(1, None, None);
+		session.initialize(vec![NodeId::from(1), NodeId::from(2)].into_iter().collect()).unwrap();
+		assert_eq!(session.state(), ConsensusSessionState::EstablishingConsensus);
+		session.on_consensus_message(&NodeId::from(2), &ConsensusMessage::ConfirmConsensusInitialization(ConfirmConsensusInitialization {
+			is_confirmed: true,
+		})).unwrap();
+		assert_eq!(session.state(), ConsensusSessionState::ConsensusEstablished);
+	}
+
+	#[test]
+	fn consensus_session_consensus_is_reached_when_initializes_with_zero_threshold() {
+		let mut session = make_master_consensus_session(0, None, None);
+		session.initialize(vec![NodeId::from(1), NodeId::from(2)].into_iter().collect()).unwrap();
+		assert_eq!(session.state(), ConsensusSessionState::ConsensusEstablished);
+		session.on_consensus_message(&NodeId::from(2), &ConsensusMessage::ConfirmConsensusInitialization(ConfirmConsensusInitialization {
+			is_confirmed: true,
+		})).unwrap();
+		assert_eq!(session.state(), ConsensusSessionState::ConsensusEstablished);
+	}
+
+	#[test]
+	fn consensus_session_consensus_is_not_reached_when_initializes_with_zero_threshold_and_master_rejects() {
+		let requester = Random.generate().unwrap();
+		let acl_storage = DummyAclStorage::default();
+		acl_storage.prohibit(requester.public().clone(), SessionId::default());
+
+		let mut session = make_master_consensus_session(0, Some(requester), Some(acl_storage));
+		session.initialize(vec![NodeId::from(1), NodeId::from(2)].into_iter().collect()).unwrap();
+		assert_eq!(session.state(), ConsensusSessionState::EstablishingConsensus);
+		session.on_consensus_message(&NodeId::from(2), &ConsensusMessage::ConfirmConsensusInitialization(ConfirmConsensusInitialization {
+			is_confirmed: true,
+		})).unwrap();
+		assert_eq!(session.state(), ConsensusSessionState::ConsensusEstablished);
+	}
+
+	#[test]
+	fn consensus_session_consensus_is_failed_by_master_node() {
+		let requester = Random.generate().unwrap();
+		let acl_storage = DummyAclStorage::default();
+		acl_storage.prohibit(requester.public().clone(), SessionId::default());
+
+		let mut session = make_master_consensus_session(1, Some(requester), Some(acl_storage));
+		assert_eq!(session.initialize(vec![NodeId::from(1), NodeId::from(2)].into_iter().collect()).unwrap_err(), Error::ConsensusUnreachable);
+		assert_eq!(session.state(), ConsensusSessionState::Failed);
+	}
+
+	#[test]
+	fn consensus_session_consensus_is_failed_by_slave_node() {
+		let mut session = make_master_consensus_session(1, None, None);
+		session.initialize(vec![NodeId::from(1), NodeId::from(2)].into_iter().collect()).unwrap();
+		assert_eq!(session.state(), ConsensusSessionState::EstablishingConsensus);
+		assert_eq!(session.on_consensus_message(&NodeId::from(2), &ConsensusMessage::ConfirmConsensusInitialization(ConfirmConsensusInitialization {
+			is_confirmed: false,
+		})).unwrap_err(), Error::ConsensusUnreachable);
+		assert_eq!(session.state(), ConsensusSessionState::Failed);
+	}
+
+	#[test]
+	fn consensus_session_job_dissemination_fails_if_consensus_is_not_reached() {
+		let mut session = make_master_consensus_session(1, None, None);
+		assert_eq!(session.disseminate_jobs(SquaredSumJobExecutor, DummyJobTransport::default()).unwrap_err(), Error::InvalidStateForRequest);
+	}
+
+	#[test]
+	fn consensus_session_job_dissemination_selects_master_node_if_agreed() {
+		let mut session = make_master_consensus_session(0, None, None);
+		session.initialize(vec![NodeId::from(1), NodeId::from(2)].into_iter().collect()).unwrap();
+		assert_eq!(session.state(), ConsensusSessionState::ConsensusEstablished);
+		session.on_consensus_message(&NodeId::from(2), &ConsensusMessage::ConfirmConsensusInitialization(ConfirmConsensusInitialization {
+			is_confirmed: true,
+		})).unwrap();
+		assert_eq!(session.state(), ConsensusSessionState::ConsensusEstablished);
+		session.disseminate_jobs(SquaredSumJobExecutor, DummyJobTransport::default()).unwrap();
+		assert_eq!(session.state(), ConsensusSessionState::Finished);
+		assert!(session.computation_job().responses().contains_key(&NodeId::from(1)));
+	}
+
+	#[test]
+	fn consensus_session_job_dissemination_does_not_select_master_node_if_rejected() {
+		let requester = Random.generate().unwrap();
+		let acl_storage = DummyAclStorage::default();
+		acl_storage.prohibit(requester.public().clone(), SessionId::default());
+
+		let mut session = make_master_consensus_session(0, Some(requester), Some(acl_storage));
+		session.initialize(vec![NodeId::from(1), NodeId::from(2)].into_iter().collect()).unwrap();
+		assert_eq!(session.state(), ConsensusSessionState::EstablishingConsensus);
+		session.on_consensus_message(&NodeId::from(2), &ConsensusMessage::ConfirmConsensusInitialization(ConfirmConsensusInitialization {
+			is_confirmed: true,
+		})).unwrap();
+		assert_eq!(session.state(), ConsensusSessionState::ConsensusEstablished);
+		session.disseminate_jobs(SquaredSumJobExecutor, DummyJobTransport::default()).unwrap();
+		assert_eq!(session.state(), ConsensusSessionState::WaitingForPartialResults);
+		assert!(!session.computation_job().responses().contains_key(&NodeId::from(1)));
+	}
+
+	#[test]
+	fn consensus_session_computation_request_is_rejected_when_received_by_master_node() {
+		let mut session = make_master_consensus_session(0, None, None);
+		assert_eq!(session.on_job_request(&NodeId::from(2), 2, SquaredSumJobExecutor, DummyJobTransport::default()).unwrap_err(), Error::InvalidMessage);
+	}
+
+	#[test]
+	fn consensus_session_computation_request_is_rejected_when_received_before_consensus_is_established() {
+		let mut session = make_slave_consensus_session(0, None);
+		assert_eq!(session.on_job_request(&NodeId::from(1), 2, SquaredSumJobExecutor, DummyJobTransport::default()).unwrap_err(), Error::InvalidStateForRequest);
+	}
+
+	#[test]
+	fn consensus_session_computation_request_is_ignored_when_wrong() {
+		let mut session = make_slave_consensus_session(0, None);
+		assert_eq!(session.state(), ConsensusSessionState::WaitingForInitialization);
+		session.on_consensus_message(&NodeId::from(1), &ConsensusMessage::InitializeConsensusSession(InitializeConsensusSession {
+			requestor_signature: sign(Random.generate().unwrap().secret(), &SessionId::default()).unwrap().into(),
+		})).unwrap();
+		assert_eq!(session.state(), ConsensusSessionState::ConsensusEstablished);
+		assert_eq!(session.on_job_request(&NodeId::from(1), 20, SquaredSumJobExecutor, DummyJobTransport::default()).unwrap_err(), Error::InvalidMessage);
+		assert_eq!(session.state(), ConsensusSessionState::ConsensusEstablished);
+	}
+
+	#[test]
+	fn consensus_session_computation_request_is_processed_when_correct() {
+		let mut session = make_slave_consensus_session(0, None);
+		assert_eq!(session.state(), ConsensusSessionState::WaitingForInitialization);
+		session.on_consensus_message(&NodeId::from(1), &ConsensusMessage::InitializeConsensusSession(InitializeConsensusSession {
+			requestor_signature: sign(Random.generate().unwrap().secret(), &SessionId::default()).unwrap().into(),
+		})).unwrap();
+		assert_eq!(session.state(), ConsensusSessionState::ConsensusEstablished);
+		session.on_job_request(&NodeId::from(1), 2, SquaredSumJobExecutor, DummyJobTransport::default()).unwrap();
+		assert_eq!(session.state(), ConsensusSessionState::ConsensusEstablished);
+	}
+
+	#[test]
+	fn consensus_session_computation_response_is_ignored_when_consensus_is_not_reached() {
+		let mut session = make_master_consensus_session(1, None, None);
+		assert_eq!(session.on_job_response(&NodeId::from(2), 4).unwrap_err(), Error::InvalidStateForRequest);
+	}
+
+	#[test]
+	fn consessus_session_completion_is_ignored_when_received_from_non_master_node() {
+		let mut session = make_slave_consensus_session(0, None);
+		assert_eq!(session.on_session_completed(&NodeId::from(3)).unwrap_err(), Error::InvalidMessage);
+	}
+
+	#[test]
+	fn consessus_session_completion_is_ignored_when_consensus_is_not_established() {
+		let mut session = make_slave_consensus_session(0, None);
+		assert_eq!(session.on_session_completed(&NodeId::from(1)).unwrap_err(), Error::InvalidStateForRequest);
+	}
+
+	#[test]
+	fn consessus_session_completion_is_accepted() {
+		let mut session = make_slave_consensus_session(0, None);
+		session.on_consensus_message(&NodeId::from(1), &ConsensusMessage::InitializeConsensusSession(InitializeConsensusSession {
+			requestor_signature: sign(Random.generate().unwrap().secret(), &SessionId::default()).unwrap().into(),
+		})).unwrap();
+		session.on_session_completed(&NodeId::from(1)).unwrap();
+		assert_eq!(session.state(), ConsensusSessionState::Finished);
+	}
+
+	#[test]
+	fn consensus_session_continues_if_node_error_received_by_uninitialized_master() {
+		let mut session = make_master_consensus_session(0, None, None);
+		assert_eq!(session.on_node_error(&NodeId::from(2)), Ok(false));
+	}
+
+	#[test]
+	fn consensus_session_fails_if_node_error_received_by_uninitialized_slave_from_master() {
+		let mut session = make_slave_consensus_session(0, None);
+		assert_eq!(session.on_node_error(&NodeId::from(1)), Err(Error::ConsensusUnreachable));
+		assert_eq!(session.state(), ConsensusSessionState::Failed);
+	}
+
+	#[test]
+	fn consensus_session_continues_if_node_error_received_by_master_during_establish_and_enough_nodes_left() {
+		let mut session = make_master_consensus_session(1, None, None);
+		session.initialize(vec![NodeId::from(1), NodeId::from(2), NodeId::from(3)].into_iter().collect()).unwrap();
+		assert_eq!(session.on_node_error(&NodeId::from(2)), Ok(false));
+	}
+
+	#[test]
+	fn consensus_session_fails_if_node_error_received_by_master_during_establish_and_not_enough_nodes_left() {
+		let mut session = make_master_consensus_session(1, None, None);
+		session.initialize(vec![NodeId::from(1), NodeId::from(2)].into_iter().collect()).unwrap();
+		assert_eq!(session.on_node_error(&NodeId::from(2)), Err(Error::ConsensusUnreachable));
+		assert_eq!(session.state(), ConsensusSessionState::Failed);
+	}
+
+	#[test]
+	fn consensus_session_continues_if_node2_error_received_by_master_after_consensus_established_and_enough_nodes_left() {
+		let mut session = make_master_consensus_session(1, None, None);
+		session.initialize(vec![NodeId::from(1), NodeId::from(2), NodeId::from(3)].into_iter().collect()).unwrap();
+		session.on_consensus_message(&NodeId::from(2), &ConsensusMessage::ConfirmConsensusInitialization(ConfirmConsensusInitialization {
+			is_confirmed: true,
+		})).unwrap();
+		assert_eq!(session.on_node_error(&NodeId::from(2)), Ok(false));
+		assert_eq!(session.state(), ConsensusSessionState::ConsensusEstablished);
+	}
+
+	#[test]
+	fn consensus_session_continues_if_node3_error_received_by_master_after_consensus_established_and_enough_nodes_left() {
+		let mut session = make_master_consensus_session(1, None, None);
+		session.initialize(vec![NodeId::from(1), NodeId::from(2), NodeId::from(3)].into_iter().collect()).unwrap();
+		session.on_consensus_message(&NodeId::from(2), &ConsensusMessage::ConfirmConsensusInitialization(ConfirmConsensusInitialization {
+			is_confirmed: true,
+		})).unwrap();
+		assert_eq!(session.on_node_error(&NodeId::from(3)), Ok(false));
+		assert_eq!(session.state(), ConsensusSessionState::ConsensusEstablished);
+	}
+
+	#[test]
+	fn consensus_session_fails_if_node_error_received_by_master_after_consensus_established_and_not_enough_nodes_left() {
+		let mut session = make_master_consensus_session(1, None, None);
+		session.initialize(vec![NodeId::from(1), NodeId::from(2)].into_iter().collect()).unwrap();
+		session.on_consensus_message(&NodeId::from(2), &ConsensusMessage::ConfirmConsensusInitialization(ConfirmConsensusInitialization {
+			is_confirmed: true,
+		})).unwrap();
+		assert_eq!(session.on_node_error(&NodeId::from(2)), Err(Error::ConsensusUnreachable));
+		assert_eq!(session.state(), ConsensusSessionState::Failed);
+	}
+
+	#[test]
+	fn consensus_session_continues_if_node_error_received_from_slave_not_participating_in_computation() {
+		let mut session = make_master_consensus_session(1, None, None);
+		session.initialize(vec![NodeId::from(1), NodeId::from(2), NodeId::from(3), NodeId::from(4)].into_iter().collect()).unwrap();
+		session.on_consensus_message(&NodeId::from(2), &ConsensusMessage::ConfirmConsensusInitialization(ConfirmConsensusInitialization {
+			is_confirmed: true,
+		})).unwrap();
+		session.on_consensus_message(&NodeId::from(3), &ConsensusMessage::ConfirmConsensusInitialization(ConfirmConsensusInitialization {
+			is_confirmed: true,
+		})).unwrap();
+		session.disseminate_jobs(SquaredSumJobExecutor, DummyJobTransport::default()).unwrap();
+		assert_eq!(session.on_node_error(&NodeId::from(3)), Ok(false));
+		assert_eq!(session.on_node_error(&NodeId::from(4)), Ok(false));
+		assert_eq!(session.state(), ConsensusSessionState::WaitingForPartialResults);
+	}
+
+	#[test]
+	fn consensus_session_restarts_if_node_error_received_from_slave_participating_in_computation_and_enough_nodes_left() {
+		let mut session = make_master_consensus_session(1, None, None);
+		session.initialize(vec![NodeId::from(1), NodeId::from(2), NodeId::from(3), NodeId::from(4)].into_iter().collect()).unwrap();
+		session.on_consensus_message(&NodeId::from(2), &ConsensusMessage::ConfirmConsensusInitialization(ConfirmConsensusInitialization {
+			is_confirmed: true,
+		})).unwrap();
+		session.disseminate_jobs(SquaredSumJobExecutor, DummyJobTransport::default()).unwrap();
+		assert_eq!(session.state(), ConsensusSessionState::WaitingForPartialResults);
+
+		session.on_consensus_message(&NodeId::from(3), &ConsensusMessage::ConfirmConsensusInitialization(ConfirmConsensusInitialization {
+			is_confirmed: true,
+		})).unwrap();
+		assert_eq!(session.on_node_error(&NodeId::from(2)), Ok(true));
+		assert_eq!(session.state(), ConsensusSessionState::ConsensusEstablished);
+		session.disseminate_jobs(SquaredSumJobExecutor, DummyJobTransport::default()).unwrap();
+		assert_eq!(session.state(), ConsensusSessionState::WaitingForPartialResults);
+
+		assert_eq!(session.on_node_error(&NodeId::from(3)), Ok(false));
+		assert_eq!(session.state(), ConsensusSessionState::EstablishingConsensus);
+	}
+
+	#[test]
+	fn consensus_session_fails_if_node_error_received_from_slave_participating_in_computation_and_not_enough_nodes_left() {
+		let mut session = make_master_consensus_session(1, None, None);
+		session.initialize(vec![NodeId::from(1), NodeId::from(2)].into_iter().collect()).unwrap();
+		session.on_consensus_message(&NodeId::from(2), &ConsensusMessage::ConfirmConsensusInitialization(ConfirmConsensusInitialization {
+			is_confirmed: true,
+		})).unwrap();
+		session.disseminate_jobs(SquaredSumJobExecutor, DummyJobTransport::default()).unwrap();
+		assert_eq!(session.on_node_error(&NodeId::from(2)), Err(Error::ConsensusUnreachable));
+		assert_eq!(session.state(), ConsensusSessionState::Failed);
+	}
+
+	#[test]
+	fn consensus_session_fails_if_uninitialized_session_timeouts() {
+		let mut session = make_master_consensus_session(1, None, None);
+		assert_eq!(session.on_session_timeout(), Err(Error::ConsensusUnreachable));
+	}
+
+	#[test]
+	fn consensus_session_continues_if_session_timeouts_and_enough_nodes_left_for_computation() {
+		let mut session = make_master_consensus_session(1, None, None);
+		session.initialize(vec![NodeId::from(1), NodeId::from(2), NodeId::from(3), NodeId::from(4)].into_iter().collect()).unwrap();
+		session.on_consensus_message(&NodeId::from(2), &ConsensusMessage::ConfirmConsensusInitialization(ConfirmConsensusInitialization {
+			is_confirmed: true,
+		})).unwrap();
+
+		session.disseminate_jobs(SquaredSumJobExecutor, DummyJobTransport::default()).unwrap();
+		assert_eq!(session.state(), ConsensusSessionState::WaitingForPartialResults);
+
+		session.on_consensus_message(&NodeId::from(3), &ConsensusMessage::ConfirmConsensusInitialization(ConfirmConsensusInitialization {
+			is_confirmed: true,
+		})).unwrap();
+		assert_eq!(session.on_session_timeout(), Ok(true));
+		assert_eq!(session.state(), ConsensusSessionState::ConsensusEstablished);
+
+		session.disseminate_jobs(SquaredSumJobExecutor, DummyJobTransport::default()).unwrap();
+		assert_eq!(session.state(), ConsensusSessionState::WaitingForPartialResults);
+
+		assert_eq!(session.on_session_timeout(), Ok(false));
+		assert_eq!(session.state(), ConsensusSessionState::EstablishingConsensus);
+	}
+
+	#[test]
+	fn consensus_session_continues_if_session_timeouts_and_not_enough_nodes_left_for_computation() {
+		let mut session = make_master_consensus_session(1, None, None);
+		session.initialize(vec![NodeId::from(1), NodeId::from(2)].into_iter().collect()).unwrap();
+		session.on_consensus_message(&NodeId::from(2), &ConsensusMessage::ConfirmConsensusInitialization(ConfirmConsensusInitialization {
+			is_confirmed: true,
+		})).unwrap();
+		session.disseminate_jobs(SquaredSumJobExecutor, DummyJobTransport::default()).unwrap();
+		assert_eq!(session.state(), ConsensusSessionState::WaitingForPartialResults);
+
+		assert_eq!(session.on_session_timeout(), Err(Error::ConsensusUnreachable));
+		assert_eq!(session.state(), ConsensusSessionState::Failed);
+	}
+
+	#[test]
+	fn same_consensus_group_returned_after_second_selection() {
+		let mut session = make_master_consensus_session(1, None, None);
+		session.initialize(vec![NodeId::from(1), NodeId::from(2), NodeId::from(3)].into_iter().collect()).unwrap();
+		session.on_consensus_message(&NodeId::from(2), &ConsensusMessage::ConfirmConsensusInitialization(ConfirmConsensusInitialization {
+			is_confirmed: true,
+		})).unwrap();
+		session.on_consensus_message(&NodeId::from(3), &ConsensusMessage::ConfirmConsensusInitialization(ConfirmConsensusInitialization {
+			is_confirmed: true,
+		})).unwrap();
+
+		let consensus_group1 = session.select_consensus_group().unwrap().clone();
+		let consensus_group2 = session.select_consensus_group().unwrap().clone();
+		assert_eq!(consensus_group1, consensus_group2);
+	}
+
+	#[test]
+	fn consensus_session_complete_2_of_4() {
+		let mut session = make_master_consensus_session(1, None, None);
+		session.initialize(vec![NodeId::from(1), NodeId::from(2), NodeId::from(3), NodeId::from(3)].into_iter().collect()).unwrap();
+		assert_eq!(session.state(), ConsensusSessionState::EstablishingConsensus);
+		session.on_consensus_message(&NodeId::from(2), &ConsensusMessage::ConfirmConsensusInitialization(ConfirmConsensusInitialization {
+			is_confirmed: true,
+		})).unwrap();
+		assert_eq!(session.state(), ConsensusSessionState::ConsensusEstablished);
+		session.disseminate_jobs(SquaredSumJobExecutor, DummyJobTransport::default()).unwrap();
+		assert_eq!(session.state(), ConsensusSessionState::WaitingForPartialResults);
+		session.on_job_response(&NodeId::from(2), 16).unwrap();
+		assert_eq!(session.state(), ConsensusSessionState::Finished);
+		assert_eq!(session.result(), Ok(20));
+	}
+
+	#[test]
+	fn consensus_session_complete_2_of_4_after_restart() {
+		let mut session = make_master_consensus_session(1, None, None);
+		session.initialize(vec![NodeId::from(1), NodeId::from(2), NodeId::from(3), NodeId::from(4)].into_iter().collect()).unwrap();
+		assert_eq!(session.state(), ConsensusSessionState::EstablishingConsensus);
+		session.on_consensus_message(&NodeId::from(2), &ConsensusMessage::ConfirmConsensusInitialization(ConfirmConsensusInitialization {
+			is_confirmed: true,
+		})).unwrap();
+		assert_eq!(session.state(), ConsensusSessionState::ConsensusEstablished);
+
+		session.disseminate_jobs(SquaredSumJobExecutor, DummyJobTransport::default()).unwrap();
+		assert_eq!(session.state(), ConsensusSessionState::WaitingForPartialResults);
+
+		session.on_consensus_message(&NodeId::from(3), &ConsensusMessage::ConfirmConsensusInitialization(ConfirmConsensusInitialization {
+			is_confirmed: true,
+		})).unwrap();
+
+		assert_eq!(session.on_node_error(&NodeId::from(2)).unwrap(), true);
+		assert_eq!(session.state(), ConsensusSessionState::ConsensusEstablished);
+
+		session.disseminate_jobs(SquaredSumJobExecutor, DummyJobTransport::default()).unwrap();
+		assert_eq!(session.state(), ConsensusSessionState::WaitingForPartialResults);
+
+		assert_eq!(session.on_node_error(&NodeId::from(3)).unwrap(), false);
+		assert_eq!(session.state(), ConsensusSessionState::EstablishingConsensus);
+
+		session.on_consensus_message(&NodeId::from(4), &ConsensusMessage::ConfirmConsensusInitialization(ConfirmConsensusInitialization {
+			is_confirmed: true,
+		})).unwrap();
+		assert_eq!(session.state(), ConsensusSessionState::ConsensusEstablished);
+
+		session.disseminate_jobs(SquaredSumJobExecutor, DummyJobTransport::default()).unwrap();
+		assert_eq!(session.state(), ConsensusSessionState::WaitingForPartialResults);
+
+		session.on_job_response(&NodeId::from(4), 16).unwrap();
+		assert_eq!(session.state(), ConsensusSessionState::Finished);
+		assert_eq!(session.result(), Ok(20));
+	}
+}

secret_store/src/key_server_cluster/jobs/decryption_job.rs

@@ -0,0 +1,162 @@
+// Copyright 2015-2017 Parity Technologies (UK) Ltd.
+// This file is part of Parity.
+
+// Parity is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Parity is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Parity.  If not, see <http://www.gnu.org/licenses/>.
+
+use std::collections::{BTreeSet, BTreeMap};
+use ethkey::{Public, Secret};
+use ethcrypto::ecies::encrypt;
+use ethcrypto::DEFAULT_MAC;
+use key_server_cluster::{Error, NodeId, DocumentKeyShare, EncryptedDocumentKeyShadow};
+use key_server_cluster::math;
+use key_server_cluster::jobs::job_session::{JobPartialRequestAction, JobPartialResponseAction, JobExecutor};
+
+/// Decryption job.
+pub struct DecryptionJob {
+	/// This node id.
+	self_node_id: NodeId,
+	/// Access key.
+	access_key: Secret,
+	/// Requester public key.
+	requester: Public,
+	/// Key share.
+	key_share: DocumentKeyShare,
+	/// Request id.
+	request_id: Option<Secret>,
+	/// Is shadow decryption requested.
+	is_shadow_decryption: Option<bool>,
+}
+
+/// Decryption job partial request.
+pub struct PartialDecryptionRequest {
+	/// Request id.
+	pub id: Secret,
+	/// Is shadow decryption requested.
+	pub is_shadow_decryption: bool,
+	/// Id of other nodes, participating in decryption.
+	pub other_nodes_ids: BTreeSet<NodeId>,
+}
+
+/// Decryption job partial response.
+pub struct PartialDecryptionResponse {
+	/// Request id.
+	pub request_id: Secret,
+	/// Shadow point.
+	pub shadow_point: Public,
+	/// Decryption shadow coefficient, if requested.
+	pub decrypt_shadow: Option<Vec<u8>>,
+}
+
+impl DecryptionJob {
+	pub fn new_on_slave(self_node_id: NodeId, access_key: Secret, requester: Public, key_share: DocumentKeyShare) -> Result<Self, Error> {
+		debug_assert!(key_share.common_point.is_some() && key_share.encrypted_point.is_some());
+		Ok(DecryptionJob {
+			self_node_id: self_node_id,
+			access_key: access_key,
+			requester: requester,
+			key_share: key_share,
+			request_id: None,
+			is_shadow_decryption: None,
+		})
+	}
+
+	pub fn new_on_master(self_node_id: NodeId, access_key: Secret, requester: Public, key_share: DocumentKeyShare, is_shadow_decryption: bool) -> Result<Self, Error> {
+		debug_assert!(key_share.common_point.is_some() && key_share.encrypted_point.is_some());
+		Ok(DecryptionJob {
+			self_node_id: self_node_id,
+			access_key: access_key,
+			requester: requester,
+			key_share: key_share,
+			request_id: Some(math::generate_random_scalar()?),
+			is_shadow_decryption: Some(is_shadow_decryption),
+		})
+	}
+}
+
+impl JobExecutor for DecryptionJob {
+	type PartialJobRequest = PartialDecryptionRequest;
+	type PartialJobResponse = PartialDecryptionResponse;
+	type JobResponse = EncryptedDocumentKeyShadow;
+
+	fn prepare_partial_request(&self, node: &NodeId, nodes: &BTreeSet<NodeId>) -> Result<PartialDecryptionRequest, Error> {
+		debug_assert!(nodes.len() == self.key_share.threshold + 1);
+
+		let request_id = self.request_id.as_ref()
+			.expect("prepare_partial_request is only called on master nodes; request_id is filed in constructor on master nodes; qed");
+		let is_shadow_decryption = self.is_shadow_decryption
+			.expect("prepare_partial_request is only called on master nodes; is_shadow_decryption is filed in constructor on master nodes; qed");
+		let mut other_nodes_ids = nodes.clone();
+		other_nodes_ids.remove(node);
+
+		Ok(PartialDecryptionRequest {
+			id: request_id.clone(),
+			is_shadow_decryption: is_shadow_decryption,
+			other_nodes_ids: other_nodes_ids,
+		})
+	}
+
+	fn process_partial_request(&self, partial_request: PartialDecryptionRequest) -> Result<JobPartialRequestAction<PartialDecryptionResponse>, Error> {
+		if partial_request.other_nodes_ids.len() != self.key_share.threshold
+			|| partial_request.other_nodes_ids.contains(&self.self_node_id)
+			|| partial_request.other_nodes_ids.iter().any(|n| !self.key_share.id_numbers.contains_key(n)) {
+			return Err(Error::InvalidMessage);
+		}
+
+		let self_id_number = &self.key_share.id_numbers[&self.self_node_id];
+		let other_id_numbers = partial_request.other_nodes_ids.iter().map(|n| &self.key_share.id_numbers[n]);
+		let node_shadow = math::compute_node_shadow(&self.key_share.secret_share, &self_id_number, other_id_numbers)?;
+		let decrypt_shadow = if partial_request.is_shadow_decryption { Some(math::generate_random_scalar()?) } else { None };
+		let common_point = self.key_share.common_point.as_ref().expect("DecryptionJob is only created when common_point is known; qed");
+		let (shadow_point, decrypt_shadow) = math::compute_node_shadow_point(&self.access_key, &common_point, &node_shadow, decrypt_shadow)?;
+		Ok(JobPartialRequestAction::Respond(PartialDecryptionResponse {
+			request_id: partial_request.id,
+			shadow_point: shadow_point,
+			decrypt_shadow: match decrypt_shadow {
+				None => None,
+				Some(decrypt_shadow) => Some(encrypt(&self.requester, &DEFAULT_MAC, &**decrypt_shadow)?),
+			},
+		}))
+	}
+
+	fn check_partial_response(&self, partial_response: &PartialDecryptionResponse) -> Result<JobPartialResponseAction, Error> {
+		if Some(&partial_response.request_id) != self.request_id.as_ref() {
+			return Ok(JobPartialResponseAction::Ignore);
+		}
+		if self.is_shadow_decryption != Some(partial_response.decrypt_shadow.is_some()) {
+			return Ok(JobPartialResponseAction::Reject);
+		}
+		Ok(JobPartialResponseAction::Accept)
+	}
+
+	fn compute_response(&self, partial_responses: &BTreeMap<NodeId, PartialDecryptionResponse>) -> Result<EncryptedDocumentKeyShadow, Error> {
+		let is_shadow_decryption = self.is_shadow_decryption
+			.expect("compute_response is only called on master nodes; is_shadow_decryption is filed in constructor on master nodes; qed");
+		let common_point = self.key_share.common_point.as_ref().expect("DecryptionJob is only created when common_point is known; qed");
+		let encrypted_point = self.key_share.encrypted_point.as_ref().expect("DecryptionJob is only created when encrypted_point is known; qed");
+		let joint_shadow_point = math::compute_joint_shadow_point(partial_responses.values().map(|s| &s.shadow_point))?;
+		let decrypted_secret = math::decrypt_with_joint_shadow(self.key_share.threshold, &self.access_key, encrypted_point, &joint_shadow_point)?;
+		Ok(EncryptedDocumentKeyShadow {
+			decrypted_secret: decrypted_secret,
+			common_point: if is_shadow_decryption {
+				Some(math::make_common_shadow_point(self.key_share.threshold, common_point.clone())?)
+			} else { None },
+			decrypt_shadows: if is_shadow_decryption {
+				Some(partial_responses.values().map(|r| r.decrypt_shadow.as_ref()
+					.expect("is_shadow_decryption == true; decrypt_shadow.is_some() is checked in check_partial_response; qed")
+					.clone())
+					.collect())
+			} else { None },
+		})
+	}
+}

secret_store/src/key_server_cluster/jobs/job_session.rs

@@ -0,0 +1,536 @@
+// Copyright 2015-2017 Parity Technologies (UK) Ltd.
+// This file is part of Parity.
+
+// Parity is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Parity is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Parity.  If not, see <http://www.gnu.org/licenses/>.
+
+use std::collections::{BTreeSet, BTreeMap};
+use key_server_cluster::{Error, NodeId, SessionMeta};
+
+#[derive(Debug, Clone, Copy, PartialEq)]
+/// Partial response action.
+pub enum JobPartialResponseAction {
+	/// Ignore this response.
+	Ignore,
+	/// Mark this response as reject.
+	Reject,
+	/// Accept this response.
+	Accept,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq)]
+/// Partial request action.
+pub enum JobPartialRequestAction<PartialJobResponse> {
+	/// Repond with reject.
+	Reject(PartialJobResponse),
+	/// Respond with this response.
+	Respond(PartialJobResponse),
+}
+
+/// Job executor.
+pub trait JobExecutor {
+	type PartialJobRequest;
+	type PartialJobResponse;
+	type JobResponse;
+
+	/// Prepare job request for given node.
+	fn prepare_partial_request(&self, node: &NodeId, nodes: &BTreeSet<NodeId>) -> Result<Self::PartialJobRequest, Error>;
+	/// Process partial request.
+	fn process_partial_request(&self, partial_request: Self::PartialJobRequest) -> Result<JobPartialRequestAction<Self::PartialJobResponse>, Error>;
+	/// Check partial response of given node.
+	fn check_partial_response(&self, partial_response: &Self::PartialJobResponse) -> Result<JobPartialResponseAction, Error>;
+	/// Compute final job response.
+	fn compute_response(&self, partial_responses: &BTreeMap<NodeId, Self::PartialJobResponse>) -> Result<Self::JobResponse, Error>;
+}
+
+/// Jobs transport.
+pub trait JobTransport {
+	type PartialJobRequest;
+	type PartialJobResponse;
+
+	/// Send partial request to given node.
+	fn send_partial_request(&self, node: &NodeId, request: Self::PartialJobRequest) -> Result<(), Error>;
+	/// Send partial request to given node.
+	fn send_partial_response(&self, node: &NodeId, response: Self::PartialJobResponse) -> Result<(), Error>;
+}
+
+#[derive(Debug, Clone, Copy, PartialEq)]
+/// Current state of job session.
+pub enum JobSessionState {
+	/// Session is inactive.
+	Inactive,
+	/// Session is active.
+	Active,
+	/// Session is finished.
+	Finished,
+	/// Session has failed.
+	Failed,
+}
+
+/// Basic request-response session on a set of nodes.
+pub struct JobSession<Executor: JobExecutor, Transport> where Transport: JobTransport<PartialJobRequest = Executor::PartialJobRequest, PartialJobResponse = Executor::PartialJobResponse> {
+	/// Session meta.
+	meta: SessionMeta,
+	/// Job executor.
+	executor: Executor,
+	/// Jobs transport.
+	transport: Transport,
+	/// Session data.
+	data: JobSessionData<Executor::PartialJobResponse>,
+	//// PartialJobRequest dummy.
+	// dummy: PhantomData<PartialJobRequest>,
+}
+
+/// Data of job session.
+struct JobSessionData<PartialJobResponse> {
+	/// Session state.
+	state: JobSessionState,
+	/// Mutable session data.
+	active_data: Option<ActiveJobSessionData<PartialJobResponse>>,
+}
+
+/// Active job session data.
+struct ActiveJobSessionData<PartialJobResponse> {
+	/// Active partial requests.
+	requests: BTreeSet<NodeId>,
+	/// Rejects to partial requests.
+	rejects: BTreeSet<NodeId>,
+	/// Received partial responses.
+	responses: BTreeMap<NodeId, PartialJobResponse>,
+}
+
+impl<Executor, Transport> JobSession<Executor, Transport> where Executor: JobExecutor, Transport: JobTransport<PartialJobRequest = Executor::PartialJobRequest, PartialJobResponse = Executor::PartialJobResponse> {
+	/// Create new session.
+	pub fn new(meta: SessionMeta, executor: Executor, transport: Transport) -> Self {
+		JobSession {
+			meta: meta,
+			executor: executor,
+			transport: transport,
+			data: JobSessionData {
+				state: JobSessionState::Inactive,
+				active_data: None,
+			},
+		}
+	}
+
+	#[cfg(test)]
+	/// Get transport reference.
+	pub fn transport(&self) -> &Transport {
+		&self.transport
+	}
+
+	/// Get job state.
+	pub fn state(&self) -> JobSessionState {
+		self.data.state
+	}
+
+	#[cfg(test)]
+	/// Get rejects.
+	pub fn rejects(&self) -> &BTreeSet<NodeId> {
+		debug_assert!(self.meta.self_node_id == self.meta.master_node_id);
+
+		&self.data.active_data.as_ref()
+			.expect("rejects is only called on master nodes after initialization; on master nodes active_data is filled during initialization; qed")
+			.rejects
+	}
+
+	/// Get active requests.
+	pub fn requests(&self) -> &BTreeSet<NodeId> {
+		debug_assert!(self.meta.self_node_id == self.meta.master_node_id);
+
+		&self.data.active_data.as_ref()
+			.expect("requests is only called on master nodes after initialization; on master nodes active_data is filled during initialization; qed")
+			.requests
+	}
+
+	#[cfg(test)]
+	/// Get responses.
+	pub fn responses(&self) -> &BTreeMap<NodeId, Executor::PartialJobResponse> {
+		debug_assert!(self.meta.self_node_id == self.meta.master_node_id);
+
+		&self.data.active_data.as_ref()
+			.expect("responses is only called on master nodes after initialization; on master nodes active_data is filled during initialization; qed")
+			.responses
+	}
+
+	/// Get job result.
+	pub fn result(&self) -> Result<Executor::JobResponse, Error> {
+		debug_assert!(self.meta.self_node_id == self.meta.master_node_id);
+
+		if self.data.state != JobSessionState::Finished {
+			return Err(Error::InvalidStateForRequest);
+		}
+
+		self.executor.compute_response(&self.data.active_data.as_ref()
+			.expect("requests is only called on master nodes; on master nodes active_data is filled during initialization; qed")
+			.responses)
+	}
+
+	/// Initialize.
+	pub fn initialize(&mut self, nodes: BTreeSet<NodeId>) -> Result<(), Error> {		
+		debug_assert!(self.meta.self_node_id == self.meta.master_node_id);
+		debug_assert!(nodes.len() >= self.meta.threshold + 1);
+
+		if self.data.state != JobSessionState::Inactive {
+			return Err(Error::InvalidStateForRequest);
+		}
+
+		// send requests to slave nodes
+		let mut waits_for_self = false;
+		let active_data = ActiveJobSessionData {
+			requests: nodes,
+			rejects: BTreeSet::new(),
+			responses: BTreeMap::new(),
+		};
+		for node in &active_data.requests {
+			if node != &self.meta.self_node_id {
+				self.transport.send_partial_request(&node, self.executor.prepare_partial_request(node, &active_data.requests)?)?;
+			} else {
+				waits_for_self = true;
+			}
+		}
+
+		// result from self
+		let self_response = if waits_for_self {
+			let partial_request = self.executor.prepare_partial_request(&self.meta.self_node_id, &active_data.requests)?;
+			Some(self.executor.process_partial_request(partial_request)?)
+		} else {
+			None
+		};
+
+		// update state
+		self.data.active_data = Some(active_data);
+		self.data.state = JobSessionState::Active;
+
+		// if we are waiting for response from self => do it
+		if let Some(self_response) = self_response {
+			let self_node_id = self.meta.self_node_id.clone();
+			match self_response {
+				JobPartialRequestAction::Respond(self_response) => self.on_partial_response(&self_node_id, self_response)?,
+				JobPartialRequestAction::Reject(self_response) => self.on_partial_response(&self_node_id, self_response)?,
+			}
+		}
+
+		Ok(())
+	}
+
+	/// When partial request is received by slave node.
+	pub fn on_partial_request(&mut self, node: &NodeId, request: Executor::PartialJobRequest) -> Result<(), Error> {
+		if node != &self.meta.master_node_id {
+			return Err(Error::InvalidMessage);
+		}
+		if self.meta.self_node_id == self.meta.master_node_id {
+			return Err(Error::InvalidMessage);
+		}
+		if self.data.state != JobSessionState::Inactive && self.data.state != JobSessionState::Finished {
+			return Err(Error::InvalidStateForRequest);
+		}
+
+		let partial_response = match self.executor.process_partial_request(request)? {
+			JobPartialRequestAction::Respond(partial_response) => {
+				self.data.state = JobSessionState::Finished;
+				partial_response
+			},
+			JobPartialRequestAction::Reject(partial_response) => {
+				self.data.state = JobSessionState::Failed;
+				partial_response
+			},
+		};
+		self.transport.send_partial_response(node, partial_response)
+	}
+
+	/// When partial request is received by master node.
+	pub fn on_partial_response(&mut self, node: &NodeId, response: Executor::PartialJobResponse) -> Result<(), Error> {
+		if self.meta.self_node_id != self.meta.master_node_id {
+			return Err(Error::InvalidMessage);
+		}
+		if self.data.state != JobSessionState::Active && self.data.state != JobSessionState::Finished {
+			return Err(Error::InvalidStateForRequest);
+		}
+
+		let active_data = self.data.active_data.as_mut()
+			.expect("on_partial_response is only called on master nodes; on master nodes active_data is filled during initialization; qed");
+		if !active_data.requests.remove(node) {
+			return Err(Error::InvalidNodeForRequest);
+		}
+		
+		match self.executor.check_partial_response(&response)? {
+			JobPartialResponseAction::Ignore => Ok(()),
+			JobPartialResponseAction::Reject => {
+				active_data.rejects.insert(node.clone());
+				if active_data.requests.len() + active_data.responses.len() >= self.meta.threshold + 1 {
+					return Ok(());
+				}
+
+				self.data.state = JobSessionState::Failed;
+				Err(Error::ConsensusUnreachable)
+			},
+			JobPartialResponseAction::Accept => {
+				active_data.responses.insert(node.clone(), response);
+
+				if active_data.responses.len() < self.meta.threshold + 1 {
+					return Ok(());
+				}
+
+				self.data.state = JobSessionState::Finished;
+				Ok(())
+			},
+		}
+	}
+
+	/// When error from node is received.
+	pub fn on_node_error(&mut self, node: &NodeId) -> Result<(), Error> {
+		if self.meta.self_node_id != self.meta.master_node_id {
+			if node != &self.meta.master_node_id {
+				return Ok(());
+			}
+
+			self.data.state = JobSessionState::Failed;
+			return Err(Error::ConsensusUnreachable);
+		}
+
+		let active_data = self.data.active_data.as_mut()
+			.expect("we have checked that we are on master node; on master nodes active_data is filled during initialization; qed");
+		if active_data.rejects.contains(node) {
+			return Ok(());
+		}
+		if active_data.requests.remove(node) || active_data.responses.remove(node).is_some() {
+			active_data.rejects.insert(node.clone());
+			if self.data.state == JobSessionState::Finished && active_data.responses.len() < self.meta.threshold + 1 {
+				self.data.state = JobSessionState::Active;
+			}
+			if active_data.requests.len() + active_data.responses.len() >= self.meta.threshold + 1 {
+				return Ok(());
+			}
+
+			self.data.state = JobSessionState::Failed;
+			return Err(Error::ConsensusUnreachable);
+		}
+
+		Ok(())
+	}
+
+	/// When session timeouted.
+	pub fn on_session_timeout(&mut self) -> Result<(), Error> {
+		if self.data.state == JobSessionState::Finished || self.data.state == JobSessionState::Failed {
+			return Ok(());
+		}
+
+		self.data.state = JobSessionState::Failed;
+		Err(Error::ConsensusUnreachable)
+	}
+}
+
+
+#[cfg(test)]
+pub mod tests {
+	use std::collections::{VecDeque, BTreeMap, BTreeSet};
+	use parking_lot::Mutex;
+	use ethkey::Public;
+	use key_server_cluster::{Error, NodeId, SessionId, SessionMeta};
+	use super::{JobPartialResponseAction, JobPartialRequestAction, JobExecutor, JobTransport, JobSession, JobSessionState};
+
+	pub struct SquaredSumJobExecutor;
+
+	impl JobExecutor for SquaredSumJobExecutor {
+		type PartialJobRequest = u32;
+		type PartialJobResponse = u32;
+		type JobResponse = u32;
+
+		fn prepare_partial_request(&self, _n: &NodeId, _nodes: &BTreeSet<NodeId>) -> Result<u32, Error> { Ok(2) }
+		fn process_partial_request(&self, r: u32) -> Result<JobPartialRequestAction<u32>, Error> { if r <= 10 { Ok(JobPartialRequestAction::Respond(r * r)) } else { Err(Error::InvalidMessage) } }
+		fn check_partial_response(&self, r: &u32) -> Result<JobPartialResponseAction, Error> { if r % 2 == 0 { Ok(JobPartialResponseAction::Accept) } else { Ok(JobPartialResponseAction::Reject) } }
+		fn compute_response(&self, r: &BTreeMap<NodeId, u32>) -> Result<u32, Error> { Ok(r.values().fold(0, |v1, v2| v1 + v2)) }
+	}
+
+	#[derive(Default)]
+	pub struct DummyJobTransport<T, U> {
+		pub requests: Mutex<VecDeque<(NodeId, T)>>,
+		pub responses: Mutex<VecDeque<(NodeId, U)>>,
+	}
+
+	impl<T, U> DummyJobTransport<T, U> {
+		pub fn response(&self) -> (NodeId, U) {
+			self.responses.lock().pop_front().unwrap()
+		}
+	}
+
+	impl<T, U> JobTransport for DummyJobTransport<T, U> {
+		type PartialJobRequest = T;
+		type PartialJobResponse = U;
+
+		fn send_partial_request(&self, node: &NodeId, request: T) -> Result<(), Error> { self.requests.lock().push_back((node.clone(), request)); Ok(()) }
+		fn send_partial_response(&self, node: &NodeId, response: U) -> Result<(), Error> { self.responses.lock().push_back((node.clone(), response)); Ok(()) }
+	}
+
+	pub fn make_master_session_meta(threshold: usize) -> SessionMeta {
+		SessionMeta { id: SessionId::default(), master_node_id: NodeId::from(1), self_node_id: NodeId::from(1), threshold: threshold }
+	}
+
+	pub fn make_slave_session_meta(threshold: usize) -> SessionMeta {
+		SessionMeta { id: SessionId::default(), master_node_id: NodeId::from(1), self_node_id: NodeId::from(2), threshold: threshold }
+	}
+
+	#[test]
+	fn job_initialize_fails_if_not_inactive() {
+		let mut job = JobSession::new(make_master_session_meta(0), SquaredSumJobExecutor, DummyJobTransport::default());
+		job.initialize(vec![Public::from(1)].into_iter().collect()).unwrap();
+		assert_eq!(job.initialize(vec![Public::from(1)].into_iter().collect()).unwrap_err(), Error::InvalidStateForRequest);
+	}
+
+	#[test]
+	fn job_initialization_leads_to_finish_if_single_node_is_required() {
+		let mut job = JobSession::new(make_master_session_meta(0), SquaredSumJobExecutor, DummyJobTransport::default());
+		job.initialize(vec![Public::from(1)].into_iter().collect()).unwrap();
+		assert_eq!(job.state(), JobSessionState::Finished);
+		assert_eq!(job.result(), Ok(4));
+	}
+
+	#[test]
+	fn job_initialization_does_not_leads_to_finish_if_single_other_node_is_required() {
+		let mut job = JobSession::new(make_master_session_meta(0), SquaredSumJobExecutor, DummyJobTransport::default());
+		job.initialize(vec![Public::from(2)].into_iter().collect()).unwrap();
+		assert_eq!(job.state(), JobSessionState::Active);
+	}
+
+	#[test]
+	fn job_request_fails_if_comes_from_non_master_node() {
+		let mut job = JobSession::new(make_slave_session_meta(0), SquaredSumJobExecutor, DummyJobTransport::default());
+		assert_eq!(job.on_partial_request(&NodeId::from(3), 2).unwrap_err(), Error::InvalidMessage);
+	}
+
+	#[test]
+	fn job_request_fails_if_comes_to_master_node() {
+		let mut job = JobSession::new(make_master_session_meta(0), SquaredSumJobExecutor, DummyJobTransport::default());
+		assert_eq!(job.on_partial_request(&NodeId::from(1), 2).unwrap_err(), Error::InvalidMessage);
+	}
+
+	#[test]
+	fn job_request_fails_if_comes_to_failed_state() {
+		let mut job = JobSession::new(make_slave_session_meta(0), SquaredSumJobExecutor, DummyJobTransport::default());
+		job.on_session_timeout().unwrap_err();
+		assert_eq!(job.on_partial_request(&NodeId::from(1), 2).unwrap_err(), Error::InvalidStateForRequest);
+	}
+
+	#[test]
+	fn job_request_succeeds_if_comes_to_finished_state() {
+		let mut job = JobSession::new(make_slave_session_meta(0), SquaredSumJobExecutor, DummyJobTransport::default());
+		job.on_partial_request(&NodeId::from(1), 2).unwrap();
+		assert_eq!(job.transport().response(), (NodeId::from(1), 4));
+		assert_eq!(job.state(), JobSessionState::Finished);
+		job.on_partial_request(&NodeId::from(1), 3).unwrap();
+		assert_eq!(job.transport().response(), (NodeId::from(1), 9));
+		assert_eq!(job.state(), JobSessionState::Finished);
+	}
+
+	#[test]
+	fn job_response_fails_if_comes_to_slave_node() {
+		let mut job = JobSession::new(make_slave_session_meta(0), SquaredSumJobExecutor, DummyJobTransport::default());
+		assert_eq!(job.on_partial_response(&NodeId::from(1), 2).unwrap_err(), Error::InvalidMessage);
+	}
+
+	#[test]
+	fn job_response_fails_if_comes_to_failed_state() {
+		let mut job = JobSession::new(make_master_session_meta(0), SquaredSumJobExecutor, DummyJobTransport::default());
+		job.initialize(vec![Public::from(2)].into_iter().collect()).unwrap();
+		job.on_session_timeout().unwrap_err();
+		assert_eq!(job.on_partial_response(&NodeId::from(2), 2).unwrap_err(), Error::InvalidStateForRequest);
+	}
+
+	#[test]
+	fn job_response_fails_if_comes_from_unknown_node() {
+		let mut job = JobSession::new(make_master_session_meta(0), SquaredSumJobExecutor, DummyJobTransport::default());
+		job.initialize(vec![Public::from(2)].into_iter().collect()).unwrap();
+		assert_eq!(job.on_partial_response(&NodeId::from(3), 2).unwrap_err(), Error::InvalidNodeForRequest);
+	}
+
+	#[test]
+	fn job_response_leads_to_failure_if_too_few_nodes_left() {
+		let mut job = JobSession::new(make_master_session_meta(1), SquaredSumJobExecutor, DummyJobTransport::default());
+		job.initialize(vec![Public::from(1), Public::from(2)].into_iter().collect()).unwrap();
+		assert_eq!(job.state(), JobSessionState::Active);
+		assert_eq!(job.on_partial_response(&NodeId::from(2), 3).unwrap_err(), Error::ConsensusUnreachable);
+		assert_eq!(job.state(), JobSessionState::Failed);
+	}
+
+	#[test]
+	fn job_response_succeeds() {
+		let mut job = JobSession::new(make_master_session_meta(2), SquaredSumJobExecutor, DummyJobTransport::default());
+		job.initialize(vec![Public::from(1), Public::from(2), Public::from(3)].into_iter().collect()).unwrap();
+		assert_eq!(job.state(), JobSessionState::Active);
+		job.on_partial_response(&NodeId::from(2), 2).unwrap();
+		assert_eq!(job.state(), JobSessionState::Active);
+	}
+
+	#[test]
+	fn job_response_leads_to_finish() {
+		let mut job = JobSession::new(make_master_session_meta(1), SquaredSumJobExecutor, DummyJobTransport::default());
+		job.initialize(vec![Public::from(1), Public::from(2)].into_iter().collect()).unwrap();
+		assert_eq!(job.state(), JobSessionState::Active);
+		job.on_partial_response(&NodeId::from(2), 2).unwrap();
+		assert_eq!(job.state(), JobSessionState::Finished);
+	}
+
+	#[test]
+	fn job_node_error_ignored_when_slave_disconnects_from_slave() {
+		let mut job = JobSession::new(make_slave_session_meta(1), SquaredSumJobExecutor, DummyJobTransport::default());
+		assert_eq!(job.state(), JobSessionState::Inactive);
+		job.on_node_error(&NodeId::from(3)).unwrap();
+		assert_eq!(job.state(), JobSessionState::Inactive);
+	}
+
+	#[test]
+	fn job_node_error_leads_to_fail_when_slave_disconnects_from_master() {
+		let mut job = JobSession::new(make_slave_session_meta(1), SquaredSumJobExecutor, DummyJobTransport::default());
+		assert_eq!(job.state(), JobSessionState::Inactive);
+		assert_eq!(job.on_node_error(&NodeId::from(1)).unwrap_err(), Error::ConsensusUnreachable);
+		assert_eq!(job.state(), JobSessionState::Failed);
+	}
+
+	#[test]
+	fn job_node_error_ignored_when_disconnects_from_rejected() {
+		let mut job = JobSession::new(make_master_session_meta(1), SquaredSumJobExecutor, DummyJobTransport::default());
+		job.initialize(vec![Public::from(1), Public::from(2), Public::from(3)].into_iter().collect()).unwrap();
+		assert_eq!(job.state(), JobSessionState::Active);
+		job.on_partial_response(&NodeId::from(2), 3).unwrap();
+		job.on_node_error(&NodeId::from(2)).unwrap();
+		assert_eq!(job.state(), JobSessionState::Active);
+	}
+
+	#[test]
+	fn job_node_error_ignored_when_disconnects_from_unknown() {
+		let mut job = JobSession::new(make_master_session_meta(1), SquaredSumJobExecutor, DummyJobTransport::default());
+		job.initialize(vec![Public::from(1), Public::from(2)].into_iter().collect()).unwrap();
+		assert_eq!(job.state(), JobSessionState::Active);
+		job.on_node_error(&NodeId::from(3)).unwrap();
+		assert_eq!(job.state(), JobSessionState::Active);
+	}
+
+	#[test]
+	fn job_node_error_ignored_when_disconnects_from_requested_and_enough_nodes_left() {
+		let mut job = JobSession::new(make_master_session_meta(1), SquaredSumJobExecutor, DummyJobTransport::default());
+		job.initialize(vec![Public::from(1), Public::from(2), Public::from(3)].into_iter().collect()).unwrap();
+		assert_eq!(job.state(), JobSessionState::Active);
+		job.on_node_error(&NodeId::from(3)).unwrap();
+		assert_eq!(job.state(), JobSessionState::Active);
+	}
+
+	#[test]
+	fn job_node_error_leads_to_fail_when_disconnects_from_requested_and_not_enough_nodes_left() {
+		let mut job = JobSession::new(make_master_session_meta(1), SquaredSumJobExecutor, DummyJobTransport::default());
+		job.initialize(vec![Public::from(1), Public::from(2)].into_iter().collect()).unwrap();
+		assert_eq!(job.state(), JobSessionState::Active);
+		assert_eq!(job.on_node_error(&NodeId::from(2)).unwrap_err(), Error::ConsensusUnreachable);
+		assert_eq!(job.state(), JobSessionState::Failed);
+	}
+}

secret_store/src/key_server_cluster/jobs/key_access_job.rs

@@ -0,0 +1,73 @@
+// Copyright 2015-2017 Parity Technologies (UK) Ltd.
+// This file is part of Parity.
+
+// Parity is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Parity is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Parity.  If not, see <http://www.gnu.org/licenses/>.
+
+use std::sync::Arc;
+use std::collections::{BTreeSet, BTreeMap};
+use ethkey::{Signature, recover};
+use key_server_cluster::{Error, NodeId, SessionId, AclStorage};
+use key_server_cluster::jobs::job_session::{JobPartialResponseAction, JobPartialRequestAction, JobExecutor};
+
+/// Purpose of this job is to construct set of nodes, which have agreed to provide access to the given key for the given requestor.
+pub struct KeyAccessJob {
+	/// Key id.
+	id: SessionId,
+	/// ACL storage.
+	acl_storage: Arc<AclStorage>,
+	/// Requester signature.
+	signature: Option<Signature>,
+}
+
+impl KeyAccessJob {
+	pub fn new_on_slave(id: SessionId, acl_storage: Arc<AclStorage>) -> Self {
+		KeyAccessJob {
+			id: id,
+			acl_storage: acl_storage,
+			signature: None,
+		}
+	}
+
+	pub fn new_on_master(id: SessionId, acl_storage: Arc<AclStorage>, signature: Signature) -> Self {
+		KeyAccessJob {
+			id: id,
+			acl_storage: acl_storage,
+			signature: Some(signature),
+		}
+	}
+}
+
+impl JobExecutor for KeyAccessJob {
+	type PartialJobRequest = Signature;
+	type PartialJobResponse = bool;
+	type JobResponse = BTreeSet<NodeId>;
+
+	fn prepare_partial_request(&self, _node: &NodeId, _nodes: &BTreeSet<NodeId>) -> Result<Signature, Error> {
+		Ok(self.signature.as_ref().expect("prepare_partial_request is only called on master nodes; new_on_master fills the signature; qed").clone())
+	}
+
+	fn process_partial_request(&self, partial_request: Signature) -> Result<JobPartialRequestAction<bool>, Error> {
+		self.acl_storage.check(&recover(&partial_request, &self.id)?, &self.id)
+			.map_err(|_| Error::AccessDenied)
+			.map(|is_confirmed| if is_confirmed { JobPartialRequestAction::Respond(true) } else { JobPartialRequestAction::Reject(false) })
+	}
+
+	fn check_partial_response(&self, partial_response: &bool) -> Result<JobPartialResponseAction, Error> {
+		Ok(if *partial_response { JobPartialResponseAction::Accept } else { JobPartialResponseAction::Reject })
+	}
+
+	fn compute_response(&self, partial_responses: &BTreeMap<NodeId, bool>) -> Result<BTreeSet<NodeId>, Error> {
+		Ok(partial_responses.keys().cloned().collect())
+	}
+}

secret_store/src/key_server_cluster/jobs/mod.rs

@@ -0,0 +1,21 @@
+// Copyright 2015-2017 Parity Technologies (UK) Ltd.
+// This file is part of Parity.
+
+// Parity is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Parity is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Parity.  If not, see <http://www.gnu.org/licenses/>.
+
+pub mod consensus_session;
+pub mod decryption_job;
+pub mod job_session;
+pub mod key_access_job;
+pub mod signing_job;

secret_store/src/key_server_cluster/jobs/signing_job.rs

@@ -0,0 +1,145 @@
+// Copyright 2015-2017 Parity Technologies (UK) Ltd.
+// This file is part of Parity.
+
+// Parity is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Parity is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Parity.  If not, see <http://www.gnu.org/licenses/>.
+
+use std::collections::{BTreeSet, BTreeMap};
+use ethkey::{Public, Secret};
+use util::H256;
+use key_server_cluster::{Error, NodeId, DocumentKeyShare};
+use key_server_cluster::math;
+use key_server_cluster::jobs::job_session::{JobPartialRequestAction, JobPartialResponseAction, JobExecutor};
+
+/// Signing job.
+pub struct SigningJob {
+	/// This node id.
+	self_node_id: NodeId,
+	/// Key share.
+	key_share: DocumentKeyShare,
+	/// Session public key.
+	session_public: Public,
+	/// Session secret coefficient.
+	session_secret_coeff: Secret,
+	/// Request id.
+	request_id: Option<Secret>,
+	/// Message hash.
+	message_hash: Option<H256>,
+}
+
+/// Signing job partial request.
+pub struct PartialSigningRequest {
+	/// Request id.
+	pub id: Secret,
+	/// Message hash.
+	pub message_hash: H256,
+	/// Id of other nodes, participating in signing.
+	pub other_nodes_ids: BTreeSet<NodeId>,
+}
+
+/// Signing job partial response.
+pub struct PartialSigningResponse {
+	/// Request id.
+	pub request_id: Secret,
+	/// Partial signature.
+	pub partial_signature: Secret,
+}
+
+impl SigningJob {
+	pub fn new_on_slave(self_node_id: NodeId, key_share: DocumentKeyShare, session_public: Public, session_secret_coeff: Secret) -> Result<Self, Error> {
+		Ok(SigningJob {
+			self_node_id: self_node_id,
+			key_share: key_share,
+			session_public: session_public,
+			session_secret_coeff: session_secret_coeff,
+			request_id: None,
+			message_hash: None,
+		})
+	}
+
+	pub fn new_on_master(self_node_id: NodeId, key_share: DocumentKeyShare, session_public: Public, session_secret_coeff: Secret, message_hash: H256) -> Result<Self, Error> {
+		Ok(SigningJob {
+			self_node_id: self_node_id,
+			key_share: key_share,
+			session_public: session_public,
+			session_secret_coeff: session_secret_coeff,
+			request_id: Some(math::generate_random_scalar()?),
+			message_hash: Some(message_hash),
+		})
+	}
+}
+
+impl JobExecutor for SigningJob {
+	type PartialJobRequest = PartialSigningRequest;
+	type PartialJobResponse = PartialSigningResponse;
+	type JobResponse = (Secret, Secret);
+
+	fn prepare_partial_request(&self, node: &NodeId, nodes: &BTreeSet<NodeId>) -> Result<PartialSigningRequest, Error> {
+		debug_assert!(nodes.len() == self.key_share.threshold + 1);
+
+		let request_id = self.request_id.as_ref()
+			.expect("prepare_partial_request is only called on master nodes; request_id is filed in constructor on master nodes; qed");
+		let message_hash = self.message_hash.as_ref()
+			.expect("compute_response is only called on master nodes; message_hash is filed in constructor on master nodes; qed");
+		let mut other_nodes_ids = nodes.clone();
+		other_nodes_ids.remove(node);
+
+		Ok(PartialSigningRequest {
+			id: request_id.clone(),
+			message_hash: message_hash.clone(),
+			other_nodes_ids: other_nodes_ids,
+		})
+	}
+
+	fn process_partial_request(&self, partial_request: PartialSigningRequest) -> Result<JobPartialRequestAction<PartialSigningResponse>, Error> {
+		if partial_request.other_nodes_ids.len() != self.key_share.threshold
+			|| partial_request.other_nodes_ids.contains(&self.self_node_id)
+			|| partial_request.other_nodes_ids.iter().any(|n| !self.key_share.id_numbers.contains_key(n)) {
+			return Err(Error::InvalidMessage);
+		}
+
+		let self_id_number = &self.key_share.id_numbers[&self.self_node_id];
+		let other_id_numbers = partial_request.other_nodes_ids.iter().map(|n| &self.key_share.id_numbers[n]);
+		let combined_hash = math::combine_message_hash_with_public(&partial_request.message_hash, &self.session_public)?;
+		Ok(JobPartialRequestAction::Respond(PartialSigningResponse {
+			request_id: partial_request.id,
+			partial_signature: math::compute_signature_share(
+				self.key_share.threshold,
+				&combined_hash,
+				&self.session_secret_coeff,
+				&self.key_share.secret_share,
+				self_id_number,
+				other_id_numbers
+			)?,
+		}))
+	}
+
+	fn check_partial_response(&self, partial_response: &PartialSigningResponse) -> Result<JobPartialResponseAction, Error> {
+		if Some(&partial_response.request_id) != self.request_id.as_ref() {
+			return Ok(JobPartialResponseAction::Ignore);
+		}
+		// TODO: check_signature_share()
+
+		Ok(JobPartialResponseAction::Accept)
+	}
+
+	fn compute_response(&self, partial_responses: &BTreeMap<NodeId, PartialSigningResponse>) -> Result<(Secret, Secret), Error> {
+		let message_hash = self.message_hash.as_ref()
+			.expect("compute_response is only called on master nodes; message_hash is filed in constructor on master nodes; qed");
+
+		let signature_c = math::combine_message_hash_with_public(message_hash, &self.session_public)?;
+		let signature_s = math::compute_signature(partial_responses.values().map(|r| &r.partial_signature))?;
+	
+		Ok((signature_c, signature_s))
+	}
+}

secret_store/src/key_server_cluster/math.rs

@@ -15,6 +15,7 @@
 // along with Parity.  If not, see <http://www.gnu.org/licenses/>.
 
 use ethkey::{Public, Secret, Random, Generator, math};
+use util::{U256, H256, Hashable};
 use key_server_cluster::Error;
 
 #[derive(Debug)]
@@ -36,6 +37,48 @@ pub fn generate_random_point() -> Result<Public, Error> {
 	Ok(Random.generate()?.public().clone())
 }
 
+/// Compute publics sum.
+pub fn compute_public_sum<'a, I>(mut publics: I) -> Result<Public, Error> where I: Iterator<Item=&'a Public> {
+	let mut sum = publics.next().expect("compute_public_sum is called when there's at least one public; qed").clone();
+	while let Some(public) = publics.next() {
+		math::public_add(&mut sum, &public)?;
+	}
+	Ok(sum)
+}
+
+/// Compute secrets sum.
+pub fn compute_secret_sum<'a, I>(mut secrets: I) -> Result<Secret, Error> where I: Iterator<Item=&'a Secret> {
+	let mut sum = secrets.next().expect("compute_secret_sum is called when there's at least one secret; qed").clone();
+	while let Some(secret) = secrets.next() {
+		sum.add(secret)?;
+	}
+	Ok(sum)
+}
+
+/// Compute secrets 'shadow' multiplication: coeff * multiplication(s[j] / (s[i] - s[j])) for every i != j
+pub fn compute_shadow_mul<'a, I>(coeff: &Secret, self_secret: &Secret, mut other_secrets: I) -> Result<Secret, Error> where I: Iterator<Item=&'a Secret> {
+	// when there are no other secrets, only coeff is left
+	let other_secret = match other_secrets.next() {
+		Some(other_secret) => other_secret,
+		None => return Ok(coeff.clone()),
+	};
+
+	let mut shadow_mul = self_secret.clone();
+	shadow_mul.sub(other_secret)?;
+	shadow_mul.inv()?;
+	shadow_mul.mul(other_secret)?;
+	while let Some(other_secret) = other_secrets.next() {
+		let mut shadow_mul_element = self_secret.clone();
+		shadow_mul_element.sub(other_secret)?;
+		shadow_mul_element.inv()?;
+		shadow_mul_element.mul(other_secret)?;
+		shadow_mul.mul(&shadow_mul_element)?;
+	}
+
+	shadow_mul.mul(coeff)?;
+	Ok(shadow_mul)
+}
+
 /// Update point by multiplying to random scalar
 pub fn update_random_point(point: &mut Public) -> Result<(), Error> {
 	Ok(math::public_mul_secret(point, &generate_random_scalar()?)?)
@@ -43,12 +86,9 @@ pub fn update_random_point(point: &mut Public) -> Result<(), Error> {
 
 /// Generate random polynom of threshold degree
 pub fn generate_random_polynom(threshold: usize) -> Result<Vec<Secret>, Error> {
-	let mut polynom: Vec<_> = Vec::with_capacity(threshold + 1);
+	(0..threshold + 1)
-	for _ in 0..threshold + 1 {
+		.map(|_| generate_random_scalar())
-		polynom.push(generate_random_scalar()?);
+		.collect()
-	}
-	debug_assert_eq!(polynom.len(), threshold + 1);
-	Ok(polynom)
 }
 
 /// Compute value of polynom, using `node_number` as argument
@@ -125,12 +165,8 @@ pub fn keys_verification(threshold: usize, derived_point: &Public, number_id: &S
 }
 
 /// Compute secret share.
-pub fn compute_secret_share<'a, I>(mut secret_values: I) -> Result<Secret, Error> where I: Iterator<Item=&'a Secret> {
+pub fn compute_secret_share<'a, I>(secret_values: I) -> Result<Secret, Error> where I: Iterator<Item=&'a Secret> {
-	let mut secret_share = secret_values.next().expect("compute_secret_share is called when cluster has at least one node; qed").clone();
+	compute_secret_sum(secret_values)
-	while let Some(secret_value) = secret_values.next() {
-		secret_share.add(secret_value)?;
-	}
-	Ok(secret_share)
 }
 
 /// Compute public key share.
@@ -141,22 +177,14 @@ pub fn compute_public_share(self_secret_value: &Secret) -> Result<Public, Error>
 }
 
 /// Compute joint public key.
-pub fn compute_joint_public<'a, I>(mut public_shares: I) -> Result<Public, Error> where I: Iterator<Item=&'a Public> {
+pub fn compute_joint_public<'a, I>(public_shares: I) -> Result<Public, Error> where I: Iterator<Item=&'a Public> {
-	let mut joint_public = public_shares.next().expect("compute_joint_public is called when cluster has at least one node; qed").clone();
+	compute_public_sum(public_shares)
-	while let Some(public_share) = public_shares.next() {
-		math::public_add(&mut joint_public, &public_share)?;
-	}
-	Ok(joint_public)
 }
 
 #[cfg(test)]
 /// Compute joint secret key.
-pub fn compute_joint_secret<'a, I>(mut secret_coeffs: I) -> Result<Secret, Error> where I: Iterator<Item=&'a Secret> {
+pub fn compute_joint_secret<'a, I>(secret_coeffs: I) -> Result<Secret, Error> where I: Iterator<Item=&'a Secret> {
-	let mut joint_secret = secret_coeffs.next().expect("compute_joint_private is called when cluster has at least one node; qed").clone();
+	compute_secret_sum(secret_coeffs)
-	while let Some(secret_coeff) = secret_coeffs.next() {
-		joint_secret.add(secret_coeff)?;
-	}
-	Ok(joint_secret)
 }
 
 /// Encrypt secret with joint public key.
@@ -180,26 +208,8 @@ pub fn encrypt_secret(secret: &Public, joint_public: &Public) -> Result<Encrypte
 }
 
 /// Compute shadow for the node.
-pub fn compute_node_shadow<'a, I>(node_number: &Secret, node_secret_share: &Secret, mut other_nodes_numbers: I) -> Result<Secret, Error> where I: Iterator<Item=&'a Secret> {
+pub fn compute_node_shadow<'a, I>(node_secret_share: &Secret, node_number: &Secret, other_nodes_numbers: I) -> Result<Secret, Error> where I: Iterator<Item=&'a Secret> {
-	let other_node_number = match other_nodes_numbers.next() {
+	compute_shadow_mul(node_secret_share, node_number, other_nodes_numbers)
-		Some(other_node_number) => other_node_number,
-		None => return Ok(node_secret_share.clone()),
-	};
-
-	let mut shadow = node_number.clone();
-	shadow.sub(other_node_number)?;
-	shadow.inv()?;
-	shadow.mul(other_node_number)?;
-	while let Some(other_node_number) = other_nodes_numbers.next() {
-		let mut shadow_element = node_number.clone();
-		shadow_element.sub(other_node_number)?;
-		shadow_element.inv()?;
-		shadow_element.mul(other_node_number)?;
-		shadow.mul(&shadow_element)?;
-	}
-
-	shadow.mul(&node_secret_share)?;
-	Ok(shadow)
 }
 
 /// Compute shadow point for the node.
@@ -224,21 +234,14 @@ pub fn compute_node_shadow_point(access_key: &Secret, common_point: &Public, nod
 }
 
 /// Compute joint shadow point.
-pub fn compute_joint_shadow_point<'a, I>(mut nodes_shadow_points: I) -> Result<Public, Error> where I: Iterator<Item=&'a Public> {
+pub fn compute_joint_shadow_point<'a, I>(nodes_shadow_points: I) -> Result<Public, Error> where I: Iterator<Item=&'a Public> {
-	let mut joint_shadow_point = nodes_shadow_points.next().expect("compute_joint_shadow_point is called when at least two nodes are required to decrypt secret; qed").clone();
+	compute_public_sum(nodes_shadow_points)
-	while let Some(node_shadow_point) = nodes_shadow_points.next() {
-		math::public_add(&mut joint_shadow_point, &node_shadow_point)?;
-	}
-	Ok(joint_shadow_point)
 }
 
 #[cfg(test)]
 /// Compute joint shadow point (version for tests).
-pub fn compute_joint_shadow_point_test<'a, I>(access_key: &Secret, common_point: &Public, mut nodes_shadows: I) -> Result<Public, Error> where I: Iterator<Item=&'a Secret> {
+pub fn compute_joint_shadow_point_test<'a, I>(access_key: &Secret, common_point: &Public, nodes_shadows: I) -> Result<Public, Error> where I: Iterator<Item=&'a Secret> {
-	let mut joint_shadow = nodes_shadows.next().expect("compute_joint_shadow_point_test is called when at least two nodes are required to decrypt secret; qed").clone();
+	let mut joint_shadow = compute_secret_sum(nodes_shadows)?;
-	while let Some(node_shadow) = nodes_shadows.next() {
-		joint_shadow.add(node_shadow)?;
-	}
 	joint_shadow.mul(access_key)?;
 
 	let mut joint_shadow_point = common_point.clone();
@@ -277,10 +280,7 @@ pub fn make_common_shadow_point(threshold: usize, mut common_point: Public) -> R
 #[cfg(test)]
 /// Decrypt shadow-encrypted secret.
 pub fn decrypt_with_shadow_coefficients(mut decrypted_shadow: Public, mut common_shadow_point: Public, shadow_coefficients: Vec<Secret>) -> Result<Public, Error> {
-	let mut shadow_coefficients_sum = shadow_coefficients[0].clone();
+	let shadow_coefficients_sum = compute_secret_sum(shadow_coefficients.iter())?;
-	for shadow_coefficient in shadow_coefficients.iter().skip(1) {
-		shadow_coefficients_sum.add(shadow_coefficient)?;
-	}
 	math::public_mul_secret(&mut common_shadow_point, &shadow_coefficients_sum)?;
 	math::public_add(&mut decrypted_shadow, &common_shadow_point)?;
 	Ok(decrypted_shadow)
@@ -298,11 +298,139 @@ pub fn decrypt_with_joint_secret(encrypted_point: &Public, common_point: &Public
 	Ok(decrypted_point)
 }
 
+/// Combine message hash with public key X coordinate.
+pub fn combine_message_hash_with_public(message_hash: &H256, public: &Public) -> Result<Secret, Error> {
+	// buffer is just [message_hash | public.x]
+	let mut buffer = [0; 64];
+	buffer[0..32].copy_from_slice(&message_hash[0..32]);
+	buffer[32..64].copy_from_slice(&public[0..32]);
+
+	// calculate hash of buffer
+	let hash = (&buffer[..]).sha3();
+
+	// map hash to EC finite field value
+	let hash: U256 = hash.into();
+	let hash: H256 = (hash % math::curve_order()).into();
+	let hash = Secret::from_slice(&*hash);
+	hash.check_validity()?;
+
+	Ok(hash)
+}
+
+/// Compute signature share.
+pub fn compute_signature_share<'a, I>(threshold: usize, combined_hash: &Secret, one_time_secret_coeff: &Secret, node_secret_share: &Secret, node_number: &Secret, other_nodes_numbers: I)
+	-> Result<Secret, Error> where I: Iterator<Item=&'a Secret> {
+	let mut sum = one_time_secret_coeff.clone();
+	let mut subtrahend = compute_shadow_mul(combined_hash, node_number, other_nodes_numbers)?;
+	subtrahend.mul(node_secret_share)?;
+	if threshold % 2 == 0 {
+		sum.sub(&subtrahend)?;
+	} else {
+		sum.add(&subtrahend)?;
+	}
+	Ok(sum)
+}
+
+/// Check signature share.
+pub fn _check_signature_share<'a, I>(_combined_hash: &Secret, _signature_share: &Secret, _public_share: &Public, _one_time_public_share: &Public, _node_numbers: I)
+	-> Result<bool, Error> where I: Iterator<Item=&'a Secret> {
+	// TODO: in paper partial signature is checked using comparison:
+	//    sig[i] * T                                  = r[i] - c * lagrange_coeff(i) * y[i]
+	// => (k[i] - c * lagrange_coeff(i) * s[i]) * T   = r[i] - c * lagrange_coeff(i) * y[i]
+	// => k[i] * T - c * lagrange_coeff(i) * s[i] * T = k[i] * T - c * lagrange_coeff(i) * y[i]
+	// => this means that y[i] = s[i] * T
+	// but when verifying signature (for t = 1), nonce public (r) is restored using following expression:
+	// r = (sig[0] + sig[1]) * T - c * y
+	// r = (k[0] - c * lagrange_coeff(0) * s[0] + k[1] - c * lagrange_coeff(1) * s[1]) * T - c * y
+	// r = (k[0] + k[1]) * T - c * (lagrange_coeff(0) * s[0] + lagrange_coeff(1) * s[1]) * T - c * y
+	// r = r - c * (lagrange_coeff(0) * s[0] + lagrange_coeff(1) * s[1]) * T - c * y
+	// => -c * y = c * (lagrange_coeff(0) * s[0] + lagrange_coeff(1) * s[1]) * T
+	// => -y = (lagrange_coeff(0) * s[0] + lagrange_coeff(1) * s[1]) * T
+	// => y[i] != s[i] * T
+	// => some other way is required
+	Ok(true)
+}
+
+/// Compute signature.
+pub fn compute_signature<'a, I>(signature_shares: I) -> Result<Secret, Error> where I: Iterator<Item=&'a Secret> {
+	compute_secret_sum(signature_shares)
+}
+
+#[cfg(test)]
+/// Locally compute Schnorr signature as described in https://en.wikipedia.org/wiki/Schnorr_signature#Signing.
+pub fn local_compute_signature(nonce: &Secret, secret: &Secret, message_hash: &Secret) -> Result<(Secret, Secret), Error> {
+	let mut nonce_public = math::generation_point();
+	math::public_mul_secret(&mut nonce_public, &nonce).unwrap();
+
+	let combined_hash = combine_message_hash_with_public(message_hash, &nonce_public)?;
+
+	let mut sig_subtrahend = combined_hash.clone();
+	sig_subtrahend.mul(secret)?;
+	let mut sig = nonce.clone();
+	sig.sub(&sig_subtrahend)?;
+
+	Ok((combined_hash, sig))
+}
+
+#[cfg(test)]
+/// Verify signature as described in https://en.wikipedia.org/wiki/Schnorr_signature#Verifying.
+pub fn verify_signature(public: &Public, signature: &(Secret, Secret), message_hash: &H256) -> Result<bool, Error> {
+	let mut addendum = math::generation_point();
+	math::public_mul_secret(&mut addendum, &signature.1)?;
+	let mut nonce_public = public.clone();
+	math::public_mul_secret(&mut nonce_public, &signature.0)?;
+	math::public_add(&mut nonce_public, &addendum)?;
+
+	let combined_hash = combine_message_hash_with_public(message_hash, &nonce_public)?;
+	Ok(combined_hash == signature.0)
+}
+
 #[cfg(test)]
 pub mod tests {
+	use std::iter::once;
 	use ethkey::KeyPair;
 	use super::*;
 
+	#[derive(Clone)]
+	struct KeyGenerationArtifacts {
+		id_numbers: Vec<Secret>,
+		polynoms1: Vec<Vec<Secret>>,
+		secrets1: Vec<Vec<Secret>>,
+		public_shares: Vec<Public>,
+		secret_shares: Vec<Secret>,
+		joint_public: Public,
+	}
+
+	fn run_key_generation(t: usize, n: usize, id_numbers: Option<Vec<Secret>>) -> KeyGenerationArtifacts {
+		// === PART1: DKG ===
+
+		// data, gathered during initialization
+		let id_numbers: Vec<_> = match id_numbers {
+			Some(id_numbers) => id_numbers,
+			None => (0..n).map(|_| generate_random_scalar().unwrap()).collect(),
+		};
+
+		// data, generated during keys dissemination
+		let polynoms1: Vec<_> = (0..n).map(|_| generate_random_polynom(t).unwrap()).collect();
+		let secrets1: Vec<_> = (0..n).map(|i| (0..n).map(|j| compute_polynom(&polynoms1[i], &id_numbers[j]).unwrap()).collect::<Vec<_>>()).collect();
+
+		// data, generated during keys generation
+		let public_shares: Vec<_> = (0..n).map(|i| compute_public_share(&polynoms1[i][0]).unwrap()).collect();
+		let secret_shares: Vec<_> = (0..n).map(|i| compute_secret_share(secrets1.iter().map(|s| &s[i])).unwrap()).collect();
+
+		// joint public key, as a result of DKG
+		let joint_public = compute_joint_public(public_shares.iter()).unwrap();
+
+		KeyGenerationArtifacts {
+			id_numbers: id_numbers,
+			polynoms1: polynoms1,
+			secrets1: secrets1,
+			public_shares: public_shares,
+			secret_shares: secret_shares,
+			joint_public: joint_public,
+		}
+	}
+
 	pub fn do_encryption_and_decryption(t: usize, joint_public: &Public, id_numbers: &[Secret], secret_shares: &[Secret], joint_secret: Option<&Secret>, document_secret_plain: Public) -> (Public, Public) {
 		// === PART2: encryption using joint public key ===
 
@@ -316,7 +444,7 @@ pub mod tests {
 
 		// use t + 1 nodes to compute joint shadow point
 		let nodes_shadows: Vec<_> = (0..t + 1).map(|i|
-			compute_node_shadow(&id_numbers[i], &secret_shares[i], id_numbers.iter()
+			compute_node_shadow(&secret_shares[i], &id_numbers[i], id_numbers.iter()
 				.enumerate()
 				.filter(|&(j, _)| j != i)
 				.take(t)
@@ -349,39 +477,108 @@ pub mod tests {
 		let test_cases = [(0, 2), (1, 2), (1, 3), (2, 3), (1, 4), (2, 4), (3, 4), (1, 5), (2, 5), (3, 5), (4, 5),
 			(1, 10), (2, 10), (3, 10), (4, 10), (5, 10), (6, 10), (7, 10), (8, 10), (9, 10)];
 		for &(t, n) in &test_cases {
-			// === PART1: DKG ===
+			let artifacts = run_key_generation(t, n, None);
-			
-			// data, gathered during initialization
-			let id_numbers: Vec<_> = (0..n).map(|_| generate_random_scalar().unwrap()).collect();
-
-			// data, generated during keys dissemination
-			let polynoms1: Vec<_> = (0..n).map(|_| generate_random_polynom(t).unwrap()).collect();
-			let secrets1: Vec<_> = (0..n).map(|i| (0..n).map(|j| compute_polynom(&polynoms1[i], &id_numbers[j]).unwrap()).collect::<Vec<_>>()).collect();
-
-			// data, generated during keys generation
-			let public_shares: Vec<_> = (0..n).map(|i| compute_public_share(&polynoms1[i][0]).unwrap()).collect();
-			let secret_shares: Vec<_> = (0..n).map(|i| compute_secret_share(secrets1.iter().map(|s| &s[i])).unwrap()).collect();
-
-			// joint public key, as a result of DKG
-			let joint_public = compute_joint_public(public_shares.iter()).unwrap();
 
 			// compute joint private key [just for test]
-			let joint_secret = compute_joint_secret(polynoms1.iter().map(|p| &p[0])).unwrap();
+			let joint_secret = compute_joint_secret(artifacts.polynoms1.iter().map(|p| &p[0])).unwrap();
 			let joint_key_pair = KeyPair::from_secret(joint_secret.clone()).unwrap();
-			assert_eq!(&joint_public, joint_key_pair.public());
+			assert_eq!(&artifacts.joint_public, joint_key_pair.public());
 
 			// check secret shares computation [just for test]
-			let secret_shares_polynom: Vec<_> = (0..t + 1).map(|k| compute_secret_share(polynoms1.iter().map(|p| &p[k])).unwrap()).collect();
+			let secret_shares_polynom: Vec<_> = (0..t + 1).map(|k| compute_secret_share(artifacts.polynoms1.iter().map(|p| &p[k])).unwrap()).collect();
-			let secret_shares_calculated_from_polynom: Vec<_> = id_numbers.iter().map(|id_number| compute_polynom(&*secret_shares_polynom, id_number).unwrap()).collect();
+			let secret_shares_calculated_from_polynom: Vec<_> = artifacts.id_numbers.iter().map(|id_number| compute_polynom(&*secret_shares_polynom, id_number).unwrap()).collect();
-			assert_eq!(secret_shares, secret_shares_calculated_from_polynom);
+			assert_eq!(artifacts.secret_shares, secret_shares_calculated_from_polynom);
 
 			// now encrypt and decrypt data
 			let document_secret_plain = generate_random_point().unwrap();
 			let (document_secret_decrypted, document_secret_decrypted_test) =
-				do_encryption_and_decryption(t, &joint_public, &id_numbers, &secret_shares, Some(&joint_secret), document_secret_plain.clone());
+				do_encryption_and_decryption(t, &artifacts.joint_public, &artifacts.id_numbers, &artifacts.secret_shares, Some(&joint_secret), document_secret_plain.clone());
 
 			assert_eq!(document_secret_plain, document_secret_decrypted_test);
 			assert_eq!(document_secret_plain, document_secret_decrypted);
 		}
 	}
+
+	#[test]
+	fn local_signature_works() {
+		let key_pair = Random.generate().unwrap();
+		let message_hash = "0000000000000000000000000000000000000000000000000000000000000042".parse().unwrap();
+		let nonce = generate_random_scalar().unwrap();
+		let signature = local_compute_signature(&nonce, key_pair.secret(), &message_hash).unwrap();
+		assert_eq!(verify_signature(key_pair.public(), &signature, &message_hash), Ok(true));
+	}
+
+	#[test]
+	fn full_signature_math_session() {
+		let test_cases = [(0, 1), (0, 2), (1, 2), (1, 3), (2, 3), (1, 4), (2, 4), (3, 4), (1, 5), (2, 5), (3, 5), (4, 5),
+			(1, 10), (2, 10), (3, 10), (4, 10), (5, 10), (6, 10), (7, 10), (8, 10), (9, 10)];
+		for &(t, n) in &test_cases {
+			// hash of the message to be signed
+			let message_hash: Secret = "0000000000000000000000000000000000000000000000000000000000000042".parse().unwrap();
+
+			// === MiDS-S algorithm ===
+			// setup: all nodes share master secret key && every node knows master public key
+			let artifacts = run_key_generation(t, n, None);
+
+			// in this gap (not related to math):
+			// master node should ask every other node if it is able to do a signing
+			// if there are < than t+1 nodes, able to sign => error
+			// select t+1 nodes for signing session
+			// all steps below are for this subset of nodes
+			let n = t + 1;
+
+			// step 1: run DKG to generate one-time secret key (nonce)
+			let id_numbers = artifacts.id_numbers.iter().cloned().take(n).collect();
+			let one_time_artifacts = run_key_generation(t, n, Some(id_numbers));
+
+			// step 2: message hash && x coordinate of one-time public value are combined
+			let combined_hash = combine_message_hash_with_public(&message_hash, &one_time_artifacts.joint_public).unwrap();
+
+			// step 3: compute signature shares
+			let partial_signatures: Vec<_> = (0..n)
+				.map(|i| compute_signature_share(
+					t,
+					&combined_hash,
+					&one_time_artifacts.polynoms1[i][0],
+					&artifacts.secret_shares[i],
+					&artifacts.id_numbers[i],
+					artifacts.id_numbers.iter()
+						.enumerate()
+						.filter(|&(j, _)| i != j)
+						.map(|(_, n)| n)
+						.take(t)
+				).unwrap())
+				.collect();
+
+			// step 4: receive and verify signatures shares from other nodes
+			let received_signatures: Vec<Vec<_>> = (0..n)
+				.map(|i| (0..n)
+					.filter(|j| i != *j)
+					.map(|j| {
+						let signature_share = partial_signatures[j].clone();
+						assert!(_check_signature_share(&combined_hash,
+							&signature_share,
+							&artifacts.public_shares[j],
+							&one_time_artifacts.public_shares[j],
+							artifacts.id_numbers.iter().take(t)).unwrap_or(false));
+						signature_share
+					})
+					.collect())
+				.collect();
+
+			// step 5: compute signature
+			let signatures: Vec<_> = (0..n)
+				.map(|i| (combined_hash.clone(), compute_signature(received_signatures[i].iter().chain(once(&partial_signatures[i]))).unwrap()))
+				.collect();
+
+			// === verify signature ===
+			let master_secret = compute_joint_secret(artifacts.polynoms1.iter().map(|p| &p[0])).unwrap();
+			let nonce = compute_joint_secret(one_time_artifacts.polynoms1.iter().map(|p| &p[0])).unwrap();
+			let local_signature = local_compute_signature(&nonce, &master_secret, &message_hash).unwrap();
+			for signature in &signatures {
+				assert_eq!(signature, &local_signature);
+				assert_eq!(verify_signature(&artifacts.joint_public, signature, &message_hash), Ok(true));
+			}
+		}
+	}
 }

secret_store/src/key_server_cluster/message.rs

@@ -18,7 +18,7 @@ use std::fmt;
 use std::collections::{BTreeSet, BTreeMap};
 use ethkey::Secret;
 use key_server_cluster::SessionId;
-use super::{SerializableH256, SerializablePublic, SerializableSecret, SerializableSignature};
+use super::{SerializableH256, SerializablePublic, SerializableSecret, SerializableSignature, SerializableMessageHash};
 
 pub type MessageSessionId = SerializableH256;
 pub type MessageNodeId = SerializablePublic;
@@ -28,10 +28,14 @@ pub type MessageNodeId = SerializablePublic;
 pub enum Message {
 	/// Cluster message.
 	Cluster(ClusterMessage),
+	/// Key generation message.
+	Generation(GenerationMessage),
 	/// Encryption message.
 	Encryption(EncryptionMessage),
 	/// Decryption message.
 	Decryption(DecryptionMessage),
+	/// Signing message.
+	Signing(SigningMessage),
 }
 
 #[derive(Clone, Debug)]
@@ -47,9 +51,9 @@ pub enum ClusterMessage {
 	KeepAliveResponse(KeepAliveResponse),
 }
 
-#[derive(Clone, Debug)]
+#[derive(Clone, Debug, Serialize, Deserialize)]
-/// All possible messages that can be sent during encryption session.
+/// All possible messages that can be sent during key generation session.
-pub enum EncryptionMessage {
+pub enum GenerationMessage {
 	/// Initialize new DKG session.
 	InitializeSession(InitializeSession),
 	/// Confirm DKG session initialization.
@@ -66,16 +70,34 @@ pub enum EncryptionMessage {
 	SessionCompleted(SessionCompleted),
 }
 
+#[derive(Clone, Debug)]
+/// All possible messages that can be sent during encryption session.
+pub enum EncryptionMessage {
+	/// Initialize encryption session.
+	InitializeEncryptionSession(InitializeEncryptionSession),
+	/// Confirm/reject encryption session initialization.
+	ConfirmEncryptionInitialization(ConfirmEncryptionInitialization),
+	/// When encryption session error has occured.
+	EncryptionSessionError(EncryptionSessionError),
+}
+
+#[derive(Clone, Debug, Serialize, Deserialize)]
+/// All possible messages that can be sent during consensus establishing.
+pub enum ConsensusMessage {
+	/// Initialize consensus session.
+	InitializeConsensusSession(InitializeConsensusSession),
+	/// Confirm/reject consensus session initialization.
+	ConfirmConsensusInitialization(ConfirmConsensusInitialization),
+}
+
 #[derive(Clone, Debug)]
 /// All possible messages that can be sent during decryption session.
 pub enum DecryptionMessage {
-	/// Initialize decryption session.
+	/// Consensus establishing message.
-	InitializeDecryptionSession(InitializeDecryptionSession),
+	DecryptionConsensusMessage(DecryptionConsensusMessage),
-	/// Confirm/reject decryption session initialization.
-	ConfirmDecryptionInitialization(ConfirmDecryptionInitialization),
 	/// Request partial decryption from node.
 	RequestPartialDecryption(RequestPartialDecryption),
-	/// Partial decryption is completed
+	/// Partial decryption is completed.
 	PartialDecryption(PartialDecryption),
 	/// When decryption session error has occured.
 	DecryptionSessionError(DecryptionSessionError),
@@ -83,6 +105,23 @@ pub enum DecryptionMessage {
 	DecryptionSessionCompleted(DecryptionSessionCompleted),
 }
 
+#[derive(Clone, Debug)]
+/// All possible messages that can be sent during signing session.
+pub enum SigningMessage {
+	/// Consensus establishing message.
+	SigningConsensusMessage(SigningConsensusMessage),
+	/// Session key generation message.
+	SigningGenerationMessage(SigningGenerationMessage),
+	/// Request partial signature from node.
+	RequestPartialSignature(RequestPartialSignature),
+	/// Partial signature is generated.
+	PartialSignature(PartialSignature),
+	/// Signing error occured.
+	SigningSessionError(SigningSessionError),
+	/// Signing session completed.
+	SigningSessionCompleted(SigningSessionCompleted),
+}
+
 #[derive(Clone, Debug, Serialize, Deserialize)]
 /// Introduce node public key.
 pub struct NodePublicKey {
@@ -115,6 +154,13 @@ pub struct KeepAliveResponse {
 pub struct InitializeSession {
 	/// Session Id.
 	pub session: MessageSessionId,
+	/// Session author.
+	pub author: SerializablePublic,
+	/// All session participants along with their identification numbers.
+	pub nodes: BTreeMap<MessageNodeId, SerializableSecret>,
+	/// Decryption threshold. During decryption threshold-of-route.len() nodes must came to
+	/// consensus to successfully decrypt message.
+	pub threshold: usize,
 	/// Derived generation point. Starting from originator, every node must multiply this
 	/// point by random scalar (unknown by other nodes). At the end of initialization
 	/// `point` will be some (k1 * k2 * ... * kn) * G = `point` where `(k1 * k2 * ... * kn)`
@@ -136,11 +182,6 @@ pub struct ConfirmInitialization {
 pub struct CompleteInitialization {
 	/// Session Id.
 	pub session: MessageSessionId,
-	/// All session participants along with their identification numbers.
-	pub nodes: BTreeMap<MessageNodeId, SerializableSecret>,
-	/// Decryption threshold. During decryption threshold-of-route.len() nodes must came to
-	/// consensus to successfully decrypt message.
-	pub threshold: usize,
 	/// Derived generation point.
 	pub derived_point: SerializablePublic,
 }
@@ -181,37 +222,132 @@ pub struct SessionError {
 pub struct SessionCompleted {
 	/// Session Id.
 	pub session: MessageSessionId,
-	/// Common (shared) encryption point.
+}
+
+#[derive(Clone, Debug, Serialize, Deserialize)]
+/// Node is requested to prepare for saving encrypted data.
+pub struct InitializeEncryptionSession {
+	/// Encryption session Id.
+	pub session: MessageSessionId,
+	/// Requestor signature.
+	pub requestor_signature: SerializableSignature,
+	/// Common point.
 	pub common_point: SerializablePublic,
-	/// Encrypted point.
+	/// Encrypted data.
 	pub encrypted_point: SerializablePublic,
 }
 
 #[derive(Clone, Debug, Serialize, Deserialize)]
-/// Node is requested to decrypt data, encrypted in given session.
+/// Node is responding to encryption initialization request.
-pub struct InitializeDecryptionSession {
+pub struct ConfirmEncryptionInitialization {
 	/// Encryption session Id.
 	pub session: MessageSessionId,
-	/// Decryption session Id.
-	pub sub_session: SerializableSecret,
-	/// Requestor signature.
-	pub requestor_signature: SerializableSignature,
-	/// Is shadow decryption requested? When true, decryption result
-	/// will be visible to the owner of requestor public key only.
-	pub is_shadow_decryption: bool,
 }
 
 #[derive(Clone, Debug, Serialize, Deserialize)]
-/// Node is responding to decryption request.
+/// When encryption session error has occured.
-pub struct ConfirmDecryptionInitialization {
+pub struct EncryptionSessionError {
 	/// Encryption session Id.
 	pub session: MessageSessionId,
-	/// Decryption session Id.
+	/// Error message.
-	pub sub_session: SerializableSecret,
+	pub error: String,
-	/// Is node confirmed to make a decryption?.
+}
+
+#[derive(Clone, Debug, Serialize, Deserialize)]
+/// Node is asked to be part of consensus group.
+pub struct InitializeConsensusSession {
+	/// Requestor signature.
+	pub requestor_signature: SerializableSignature,
+}
+
+#[derive(Clone, Debug, Serialize, Deserialize)]
+/// Node is responding to consensus initialization request.
+pub struct ConfirmConsensusInitialization {
+	/// Is node confirmed consensus participation.
 	pub is_confirmed: bool,
 }
 
+#[derive(Clone, Debug, Serialize, Deserialize)]
+/// Consensus-related signing message.
+pub struct SigningConsensusMessage {
+	/// Generation session Id.
+	pub session: MessageSessionId,
+	/// Signing session Id.
+	pub sub_session: SerializableSecret,
+	/// Consensus message.
+	pub message: ConsensusMessage,
+}
+
+#[derive(Clone, Debug, Serialize, Deserialize)]
+/// Session key generation message.
+pub struct SigningGenerationMessage {
+	/// Generation session Id.
+	pub session: MessageSessionId,
+	/// Signing session Id.
+	pub sub_session: SerializableSecret,
+	/// Generation message.
+	pub message: GenerationMessage,
+}
+
+#[derive(Clone, Debug, Serialize, Deserialize)]
+/// Request partial signature.
+pub struct RequestPartialSignature {
+	/// Generation session Id.
+	pub session: MessageSessionId,
+	/// Signing session Id.
+	pub sub_session: SerializableSecret,
+	/// Request id.
+	pub request_id: SerializableSecret,
+	/// Message hash.
+	pub message_hash: SerializableMessageHash,
+	/// Selected nodes.
+	pub nodes: BTreeSet<MessageNodeId>,
+}
+
+#[derive(Clone, Debug, Serialize, Deserialize)]
+/// Partial signature.
+pub struct PartialSignature {
+	/// Generation session Id.
+	pub session: MessageSessionId,
+	/// Signing session Id.
+	pub sub_session: SerializableSecret,
+	/// Request id.
+	pub request_id: SerializableSecret,
+	/// S part of signature.
+	pub partial_signature: SerializableSecret,
+}
+
+#[derive(Clone, Debug, Serialize, Deserialize)]
+/// When signing session error has occured.
+pub struct SigningSessionError {
+	/// Encryption session Id.
+	pub session: MessageSessionId,
+	/// Signing session Id.
+	pub sub_session: SerializableSecret,
+	/// Error description.
+	pub error: String,
+}
+
+#[derive(Clone, Debug, Serialize, Deserialize)]
+/// Signing session completed.
+pub struct SigningSessionCompleted {
+	/// Generation session Id.
+	pub session: MessageSessionId,
+	/// Signing session Id.
+	pub sub_session: SerializableSecret,
+}
+
+#[derive(Clone, Debug, Serialize, Deserialize)]
+/// Consensus-related decryption message.
+pub struct DecryptionConsensusMessage {
+	/// Generation session Id.
+	pub session: MessageSessionId,
+	/// Signing session Id.
+	pub sub_session: SerializableSecret,
+	/// Consensus message.
+	pub message: ConsensusMessage,
+}
+
 #[derive(Clone, Debug, Serialize, Deserialize)]
 /// Node is requested to do a partial decryption.
 pub struct RequestPartialDecryption {
@@ -219,6 +355,11 @@ pub struct RequestPartialDecryption {
 	pub session: MessageSessionId,
 	/// Decryption session Id.
 	pub sub_session: SerializableSecret,
+	/// Request id.
+	pub request_id: SerializableSecret,
+	/// Is shadow decryption requested? When true, decryption result
+	/// will be visible to the owner of requestor public key only.
+	pub is_shadow_decryption: bool,
 	/// Nodes that are agreed to do a decryption.
 	pub nodes: BTreeSet<MessageNodeId>,
 }
@@ -230,6 +371,8 @@ pub struct PartialDecryption {
 	pub session: MessageSessionId,
 	/// Decryption session Id.
 	pub sub_session: SerializableSecret,
+	/// Request id.
+	pub request_id: SerializableSecret,
 	/// Partially decrypted secret.
 	pub shadow_point: SerializablePublic,
 	/// Decrypt shadow coefficient (if requested), encrypted with requestor public.
@@ -256,16 +399,26 @@ pub struct DecryptionSessionCompleted {
 	pub sub_session: SerializableSecret,
 }
 
+impl GenerationMessage {
+	pub fn session_id(&self) -> &SessionId {
+		match *self {
+			GenerationMessage::InitializeSession(ref msg) => &msg.session,
+			GenerationMessage::ConfirmInitialization(ref msg) => &msg.session,
+			GenerationMessage::CompleteInitialization(ref msg) => &msg.session,
+			GenerationMessage::KeysDissemination(ref msg) => &msg.session,
+			GenerationMessage::PublicKeyShare(ref msg) => &msg.session,
+			GenerationMessage::SessionError(ref msg) => &msg.session,
+			GenerationMessage::SessionCompleted(ref msg) => &msg.session,
+		}
+	}
+}
+
 impl EncryptionMessage {
 	pub fn session_id(&self) -> &SessionId {
 		match *self {
-			EncryptionMessage::InitializeSession(ref msg) => &msg.session,
+			EncryptionMessage::InitializeEncryptionSession(ref msg) => &msg.session,
-			EncryptionMessage::ConfirmInitialization(ref msg) => &msg.session,
+			EncryptionMessage::ConfirmEncryptionInitialization(ref msg) => &msg.session,
-			EncryptionMessage::CompleteInitialization(ref msg) => &msg.session,
+			EncryptionMessage::EncryptionSessionError(ref msg) => &msg.session,
-			EncryptionMessage::KeysDissemination(ref msg) => &msg.session,
-			EncryptionMessage::PublicKeyShare(ref msg) => &msg.session,
-			EncryptionMessage::SessionError(ref msg) => &msg.session,
-			EncryptionMessage::SessionCompleted(ref msg) => &msg.session,
 		}
 	}
 }
@@ -273,8 +426,7 @@ impl EncryptionMessage {
 impl DecryptionMessage {
 	pub fn session_id(&self) -> &SessionId {
 		match *self {
-			DecryptionMessage::InitializeDecryptionSession(ref msg) => &msg.session,
+			DecryptionMessage::DecryptionConsensusMessage(ref msg) => &msg.session,
-			DecryptionMessage::ConfirmDecryptionInitialization(ref msg) => &msg.session,
 			DecryptionMessage::RequestPartialDecryption(ref msg) => &msg.session,
 			DecryptionMessage::PartialDecryption(ref msg) => &msg.session,
 			DecryptionMessage::DecryptionSessionError(ref msg) => &msg.session,
@@ -284,8 +436,7 @@ impl DecryptionMessage {
 
 	pub fn sub_session_id(&self) -> &Secret {
 		match *self {
-			DecryptionMessage::InitializeDecryptionSession(ref msg) => &msg.sub_session,
+			DecryptionMessage::DecryptionConsensusMessage(ref msg) => &msg.sub_session,
-			DecryptionMessage::ConfirmDecryptionInitialization(ref msg) => &msg.sub_session,
 			DecryptionMessage::RequestPartialDecryption(ref msg) => &msg.sub_session,
 			DecryptionMessage::PartialDecryption(ref msg) => &msg.sub_session,
 			DecryptionMessage::DecryptionSessionError(ref msg) => &msg.sub_session,
@@ -294,12 +445,38 @@ impl DecryptionMessage {
 	}
 }
 
+impl SigningMessage {
+	pub fn session_id(&self) -> &SessionId {
+		match *self {
+			SigningMessage::SigningConsensusMessage(ref msg) => &msg.session,
+			SigningMessage::SigningGenerationMessage(ref msg) => &msg.session,
+			SigningMessage::RequestPartialSignature(ref msg) => &msg.session,
+			SigningMessage::PartialSignature(ref msg) => &msg.session,
+			SigningMessage::SigningSessionError(ref msg) => &msg.session,
+			SigningMessage::SigningSessionCompleted(ref msg) => &msg.session,
+		}
+	}
+
+	pub fn sub_session_id(&self) -> &Secret {
+		match *self {
+			SigningMessage::SigningConsensusMessage(ref msg) => &msg.sub_session,
+			SigningMessage::SigningGenerationMessage(ref msg) => &msg.sub_session,
+			SigningMessage::RequestPartialSignature(ref msg) => &msg.sub_session,
+			SigningMessage::PartialSignature(ref msg) => &msg.sub_session,
+			SigningMessage::SigningSessionError(ref msg) => &msg.sub_session,
+			SigningMessage::SigningSessionCompleted(ref msg) => &msg.sub_session,
+		}
+	}
+}
+
 impl fmt::Display for Message {
 	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 		match *self {
 			Message::Cluster(ref message) => write!(f, "Cluster.{}", message),
+			Message::Generation(ref message) => write!(f, "Generation.{}", message),
 			Message::Encryption(ref message) => write!(f, "Encryption.{}", message),
 			Message::Decryption(ref message) => write!(f, "Decryption.{}", message),
+			Message::Signing(ref message) => write!(f, "Signing.{}", message),
 		}
 	}
 }
@@ -315,16 +492,35 @@ impl fmt::Display for ClusterMessage {
 	}
 }
 
+impl fmt::Display for GenerationMessage {
+	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+		match *self {
+			GenerationMessage::InitializeSession(_) => write!(f, "InitializeSession"),
+			GenerationMessage::ConfirmInitialization(_) => write!(f, "ConfirmInitialization"),
+			GenerationMessage::CompleteInitialization(_) => write!(f, "CompleteInitialization"),
+			GenerationMessage::KeysDissemination(_) => write!(f, "KeysDissemination"),
+			GenerationMessage::PublicKeyShare(_) => write!(f, "PublicKeyShare"),
+			GenerationMessage::SessionError(ref msg) => write!(f, "SessionError({})", msg.error),
+			GenerationMessage::SessionCompleted(_) => write!(f, "SessionCompleted"),
+		}
+	}
+}
+
 impl fmt::Display for EncryptionMessage {
 	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 		match *self {
-			EncryptionMessage::InitializeSession(_) => write!(f, "InitializeSession"),
+			EncryptionMessage::InitializeEncryptionSession(_) => write!(f, "InitializeEncryptionSession"),
-			EncryptionMessage::ConfirmInitialization(_) => write!(f, "ConfirmInitialization"),
+			EncryptionMessage::ConfirmEncryptionInitialization(_) => write!(f, "ConfirmEncryptionInitialization"),
-			EncryptionMessage::CompleteInitialization(_) => write!(f, "CompleteInitialization"),
+			EncryptionMessage::EncryptionSessionError(ref msg) => write!(f, "EncryptionSessionError({})", msg.error),
-			EncryptionMessage::KeysDissemination(_) => write!(f, "KeysDissemination"),
+		}
-			EncryptionMessage::PublicKeyShare(_) => write!(f, "PublicKeyShare"),
+	}
-			EncryptionMessage::SessionError(ref msg) => write!(f, "SessionError({})", msg.error),
+}
-			EncryptionMessage::SessionCompleted(_) => write!(f, "SessionCompleted"),
+
+impl fmt::Display for ConsensusMessage {
+	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+		match *self {
+			ConsensusMessage::InitializeConsensusSession(_) => write!(f, "InitializeConsensusSession"),
+			ConsensusMessage::ConfirmConsensusInitialization(_) => write!(f, "ConfirmConsensusInitialization"),
 		}
 	}
 }
@@ -332,8 +528,7 @@ impl fmt::Display for EncryptionMessage {
 impl fmt::Display for DecryptionMessage {
 	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 		match *self {
-			DecryptionMessage::InitializeDecryptionSession(_) => write!(f, "InitializeDecryptionSession"),
+			DecryptionMessage::DecryptionConsensusMessage(ref m) => write!(f, "DecryptionConsensusMessage.{}", m.message),
-			DecryptionMessage::ConfirmDecryptionInitialization(_) => write!(f, "ConfirmDecryptionInitialization"),
 			DecryptionMessage::RequestPartialDecryption(_) => write!(f, "RequestPartialDecryption"),
 			DecryptionMessage::PartialDecryption(_) => write!(f, "PartialDecryption"),
 			DecryptionMessage::DecryptionSessionError(_) => write!(f, "DecryptionSessionError"),
@@ -341,3 +536,16 @@ impl fmt::Display for DecryptionMessage {
 		}
 	}
 }
+
+impl fmt::Display for SigningMessage {
+	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+		match *self {
+			SigningMessage::SigningConsensusMessage(ref m) => write!(f, "SigningConsensusMessage.{}", m.message),
+			SigningMessage::SigningGenerationMessage(ref m) => write!(f, "SigningGenerationMessage.{}", m.message),
+			SigningMessage::RequestPartialSignature(_) => write!(f, "RequestPartialSignature"),
+			SigningMessage::PartialSignature(_) => write!(f, "PartialSignature"),
+			SigningMessage::SigningSessionError(_) => write!(f, "SigningSessionError"),
+			SigningMessage::SigningSessionCompleted(_) => write!(f, "SigningSessionCompleted"),
+		}
+	}
+}

secret_store/src/key_server_cluster/mod.rs

@@ -18,13 +18,14 @@ use std::fmt;
 use std::io::Error as IoError;
 use ethkey;
 use ethcrypto;
-use super::types::all::DocumentAddress;
+use super::types::all::ServerKeyId;
 
-pub use super::types::all::{NodeId, DocumentEncryptedKeyShadow};
+pub use super::types::all::{NodeId, EncryptedDocumentKeyShadow};
 pub use super::acl_storage::AclStorage;
 pub use super::key_storage::{KeyStorage, DocumentKeyShare};
-pub use super::serialization::{SerializableSignature, SerializableH256, SerializableSecret, SerializablePublic};
+pub use super::serialization::{SerializableSignature, SerializableH256, SerializableSecret, SerializablePublic, SerializableMessageHash};
 pub use self::cluster::{ClusterCore, ClusterConfiguration, ClusterClient};
+pub use self::generation_session::Session as GenerationSession;
 pub use self::encryption_session::Session as EncryptionSession;
 pub use self::decryption_session::Session as DecryptionSession;
 
@@ -33,7 +34,20 @@ pub use super::key_storage::tests::DummyKeyStorage;
 #[cfg(test)]
 pub use super::acl_storage::tests::DummyAclStorage;
 
-pub type SessionId = DocumentAddress;
+pub type SessionId = ServerKeyId;
+
+#[derive(Debug, Clone)]
+/// Session metadata.
+pub struct SessionMeta {
+	/// Key id.
+	pub id: SessionId,
+	/// Id of node, which has started this session.
+	pub master_node_id: NodeId,
+	/// Id of node, on which this session is running.
+	pub self_node_id: NodeId,
+	/// Session threshold.
+	pub threshold: usize,
+}
 
 #[derive(Clone, Debug, PartialEq)]
 /// Errors which can occur during encryption/decryption session
@@ -44,6 +58,10 @@ pub enum Error {
 	InvalidNodeId,
 	/// Session with the given id already exists.
 	DuplicateSessionId,
+	/// Session with the same id already completed.
+	CompletedSessionId,
+	/// Session is not ready to start yet (required data is not ready).
+	NotStartedSessionId,
 	/// Session with the given id is unknown.
 	InvalidSessionId,
 	/// Invalid number of nodes.
@@ -61,6 +79,8 @@ pub enum Error {
 	/// Current state of encryption/decryption session does not allow to proceed request.
 	/// This means that either there is some comm-failure or node is misbehaving/cheating.
 	InvalidStateForRequest,
+	/// Request cannot be sent/received from this node.
+	InvalidNodeForRequest,
 	/// Message or some data in the message was recognized as invalid.
 	/// This means that node is misbehaving/cheating.
 	InvalidMessage,
@@ -74,6 +94,8 @@ pub enum Error {
 	Serde(String),
 	/// Key storage error.
 	KeyStorage(String),
+	/// Consensus is unreachable.
+	ConsensusUnreachable,
 	/// Acl storage error.
 	AccessDenied,
 }
@@ -102,18 +124,22 @@ impl fmt::Display for Error {
 			Error::InvalidNodeAddress => write!(f, "invalid node address has been passed"),
 			Error::InvalidNodeId => write!(f, "invalid node id has been passed"),
 			Error::DuplicateSessionId => write!(f, "session with the same id is already registered"),
+			Error::CompletedSessionId => write!(f, "session with the same id is already completed"),
+			Error::NotStartedSessionId => write!(f, "not enough data to start session with the given id"),
 			Error::InvalidSessionId => write!(f, "invalid session id has been passed"),
 			Error::InvalidNodesCount => write!(f, "invalid nodes count"),
 			Error::InvalidNodesConfiguration => write!(f, "invalid nodes configuration"),
 			Error::InvalidThreshold => write!(f, "invalid threshold value has been passed"),
 			Error::TooEarlyForRequest => write!(f, "session is not yet ready to process this request"),
 			Error::InvalidStateForRequest => write!(f, "session is in invalid state for processing this request"),
+			Error::InvalidNodeForRequest => write!(f, "invalid node for this request"),
 			Error::InvalidMessage => write!(f, "invalid message is received"),
 			Error::NodeDisconnected => write!(f, "node required for this operation is currently disconnected"),
 			Error::EthKey(ref e) => write!(f, "cryptographic error {}", e),
 			Error::Io(ref e) => write!(f, "i/o error {}", e),
 			Error::Serde(ref e) => write!(f, "serde error {}", e),
 			Error::KeyStorage(ref e) => write!(f, "key storage error {}", e),
+			Error::ConsensusUnreachable => write!(f, "Consensus unreachable"),
 			Error::AccessDenied => write!(f, "Access denied"),
 		}
 	}
@@ -126,9 +152,13 @@ impl Into<String> for Error {
 }
 
 mod cluster;
+mod cluster_sessions;
 mod decryption_session;
 mod encryption_session;
+mod generation_session;
 mod io;
-mod math;
+mod jobs;
+pub mod math;
 mod message;
+mod signing_session;
 mod net;

secret_store/src/key_server_cluster/signing_session.rs

@@ -0,0 +1,706 @@
+// Copyright 2015-2017 Parity Technologies (UK) Ltd.
+// This file is part of Parity.
+
+// Parity is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Parity is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Parity.  If not, see <http://www.gnu.org/licenses/>.
+
+use std::collections::BTreeSet;
+use std::sync::Arc;
+use parking_lot::{Mutex, Condvar};
+use ethkey::{Public, Secret, Signature};
+use util::H256;
+use key_server_cluster::{Error, NodeId, SessionId, SessionMeta, AclStorage, DocumentKeyShare};
+use key_server_cluster::cluster::{Cluster};
+use key_server_cluster::cluster_sessions::ClusterSession;
+use key_server_cluster::generation_session::{SessionImpl as GenerationSession, SessionParams as GenerationSessionParams,
+	Session as GenerationSessionApi, SessionState as GenerationSessionState};
+use key_server_cluster::message::{Message, SigningMessage, SigningConsensusMessage, SigningGenerationMessage,
+	RequestPartialSignature, PartialSignature, SigningSessionCompleted, GenerationMessage, ConsensusMessage, SigningSessionError,
+	InitializeConsensusSession, ConfirmConsensusInitialization};
+use key_server_cluster::jobs::job_session::JobTransport;
+use key_server_cluster::jobs::signing_job::{PartialSigningRequest, PartialSigningResponse, SigningJob};
+use key_server_cluster::jobs::consensus_session::{ConsensusSessionParams, ConsensusSessionState, ConsensusSession};
+
+pub use key_server_cluster::decryption_session::DecryptionSessionId as SigningSessionId;
+
+/// Signing session API.
+pub trait Session: Send + Sync + 'static {
+	/// Wait until session is completed. Returns signed message.
+	fn wait(&self) -> Result<(Secret, Secret), Error>;
+}
+
+/// Distributed signing session.
+/// Based on "Efficient Multi-Party Digital Signature using Adaptive Secret Sharing for Low-Power Devices in Wireless Network" paper.
+/// Brief overview:
+/// 1) initialization: master node (which has received request for signing the message) requests all other nodes to sign the message
+/// 2) ACL check: all nodes which have received the request are querying ACL-contract to check if requestor has access to the private key
+/// 3) partial signing: every node which has succussfully checked access for the requestor do a partial signing
+/// 4) signing: master node receives all partial signatures of the secret and computes the signature
+pub struct SessionImpl {
+	/// Session core.
+	core: SessionCore,
+	/// Session data.
+	data: Mutex<SessionData>,
+}
+
+/// Immutable session data.
+struct SessionCore {
+	/// Session metadata.
+	pub meta: SessionMeta,
+	/// Signing session access key.
+	pub access_key: Secret,
+	/// Key share.
+	pub key_share: DocumentKeyShare,
+	/// Cluster which allows this node to send messages to other nodes in the cluster.
+	pub cluster: Arc<Cluster>,
+	/// SessionImpl completion condvar.
+	pub completed: Condvar,
+}
+
+/// Signing consensus session type.
+type SigningConsensusSession = ConsensusSession<SigningConsensusTransport, SigningJob, SigningJobTransport>;
+
+/// Mutable session data.
+struct SessionData {
+	/// Session state.
+	pub state: SessionState,
+	/// Message hash.
+	pub message_hash: Option<H256>,
+	/// Consensus-based signing session.
+	pub consensus_session: SigningConsensusSession,
+	/// Session key generation session.
+	pub generation_session: Option<GenerationSession>,
+	/// Decryption result.
+	pub result: Option<Result<(Secret, Secret), Error>>,
+}
+
+/// Signing session state.
+#[derive(Debug, PartialEq)]
+pub enum SessionState {
+	/// State when consensus is establishing.
+	ConsensusEstablishing,
+	/// State when session key is generating.
+	SessionKeyGeneration,
+	/// State when signature is computing.
+	SignatureComputing,
+}
+
+/// Session creation parameters
+pub struct SessionParams {
+	/// Session metadata.
+	pub meta: SessionMeta,
+	/// Session access key.
+	pub access_key: Secret,
+	/// Key share.
+	pub key_share: DocumentKeyShare,
+	/// ACL storage.
+	pub acl_storage: Arc<AclStorage>,
+	/// Cluster
+	pub cluster: Arc<Cluster>,
+}
+
+/// Signing consensus transport.
+struct SigningConsensusTransport {
+	/// Session id.
+	id: SessionId,
+	/// Session access key.
+	access_key: Secret,
+	/// Cluster.
+	cluster: Arc<Cluster>,
+}
+
+/// Signing key generation transport.
+struct SessionKeyGenerationTransport {
+	/// Session access key.
+	access_key: Secret,
+	/// Cluster.
+	cluster: Arc<Cluster>,
+	/// Other nodes ids.
+	other_nodes_ids: BTreeSet<NodeId>,
+}
+
+/// Signing job transport
+struct SigningJobTransport {
+	/// Session id.
+	id: SessionId,
+	//// Session access key.
+	access_key: Secret,
+	/// Cluster.
+	cluster: Arc<Cluster>,
+}
+
+impl SessionImpl {
+	/// Create new signing session.
+	pub fn new(params: SessionParams, requester_signature: Option<Signature>) -> Result<Self, Error> {
+		debug_assert_eq!(params.meta.threshold, params.key_share.threshold);
+		debug_assert_eq!(params.meta.self_node_id == params.meta.master_node_id, requester_signature.is_some());
+
+		use key_server_cluster::generation_session::{check_cluster_nodes, check_threshold};
+
+		// check nodes and threshold
+		let nodes = params.key_share.id_numbers.keys().cloned().collect();
+		check_cluster_nodes(&params.meta.self_node_id, &nodes)?;
+		check_threshold(params.key_share.threshold, &nodes)?;
+
+		let consensus_transport = SigningConsensusTransport {
+			id: params.meta.id.clone(),
+			access_key: params.access_key.clone(),
+			cluster: params.cluster.clone(),
+		};
+
+		Ok(SessionImpl {
+			core: SessionCore {
+				meta: params.meta.clone(),
+				access_key: params.access_key,
+				key_share: params.key_share,
+				cluster: params.cluster,
+				completed: Condvar::new(),
+			},
+			data: Mutex::new(SessionData {
+				state: SessionState::ConsensusEstablishing,
+				message_hash: None,
+				consensus_session: match requester_signature {
+					Some(requester_signature) => ConsensusSession::new_on_master(ConsensusSessionParams {
+						meta: params.meta,
+						acl_storage: params.acl_storage.clone(),
+						consensus_transport: consensus_transport,
+					}, requester_signature)?,
+					None => ConsensusSession::new_on_slave(ConsensusSessionParams {
+						meta: params.meta,
+						acl_storage: params.acl_storage.clone(),
+						consensus_transport: consensus_transport,
+					})?,
+				},
+				generation_session: None,
+				result: None,
+			}),
+		})
+	}
+
+	/// Initialize signing session on master node.
+	pub fn initialize(&self, message_hash: H256) -> Result<(), Error> {
+		let mut data = self.data.lock();
+		data.message_hash = Some(message_hash);
+		data.consensus_session.initialize(self.core.key_share.id_numbers.keys().cloned().collect())?;
+
+		if data.consensus_session.state() == ConsensusSessionState::ConsensusEstablished {
+			let generation_session = GenerationSession::new(GenerationSessionParams {
+				id: self.core.meta.id.clone(),
+				self_node_id: self.core.meta.self_node_id.clone(),
+				key_storage: None,
+				cluster: Arc::new(SessionKeyGenerationTransport {
+					access_key: self.core.access_key.clone(),
+					cluster: self.core.cluster.clone(),
+					other_nodes_ids: BTreeSet::new()
+				}),
+			});
+			generation_session.initialize(Public::default(), 0, vec![self.core.meta.self_node_id.clone()].into_iter().collect())?;
+
+			debug_assert_eq!(generation_session.state(), GenerationSessionState::WaitingForGenerationConfirmation);
+			let joint_public_and_secret = generation_session
+				.joint_public_and_secret()
+				.expect("session key is generated before signature is computed; we are in SignatureComputing state; qed")?;
+			data.generation_session = Some(generation_session);
+			data.state = SessionState::SignatureComputing;
+
+			self.core.disseminate_jobs(&mut data.consensus_session, joint_public_and_secret.0, joint_public_and_secret.1, message_hash)?;
+
+			debug_assert!(data.consensus_session.state() == ConsensusSessionState::Finished);
+			data.result = Some(Ok(data.consensus_session.result()?));
+			self.core.completed.notify_all();
+		}
+
+		Ok(())
+	}
+
+	/// Process signing message.
+	pub fn process_message(&self, sender: &NodeId, message: &SigningMessage) -> Result<(), Error> {
+		match message {
+			&SigningMessage::SigningConsensusMessage(ref message) =>
+				self.on_consensus_message(sender, message),
+			&SigningMessage::SigningGenerationMessage(ref message) =>
+				self.on_generation_message(sender, message),
+			&SigningMessage::RequestPartialSignature(ref message) => 
+				self.on_partial_signature_requested(sender, message),
+			&SigningMessage::PartialSignature(ref message) => 
+				self.on_partial_signature(sender, message),
+			&SigningMessage::SigningSessionError(ref message) => 
+				self.on_session_error(sender, message),
+			&SigningMessage::SigningSessionCompleted(ref message) => 
+				self.on_session_completed(sender, message),
+		}
+	}
+
+	/// When consensus-related message is received.
+	pub fn on_consensus_message(&self, sender: &NodeId, message: &SigningConsensusMessage) -> Result<(), Error> {
+		debug_assert!(self.core.meta.id == *message.session);
+		debug_assert!(self.core.access_key == *message.sub_session);
+		debug_assert!(sender != &self.core.meta.self_node_id);
+
+		let mut data = self.data.lock();
+		let is_establishing_consensus = data.consensus_session.state() == ConsensusSessionState::EstablishingConsensus;
+		data.consensus_session.on_consensus_message(&sender, &message.message)?;
+
+		let is_consensus_established = data.consensus_session.state() == ConsensusSessionState::ConsensusEstablished;
+		if self.core.meta.self_node_id != self.core.meta.master_node_id || !is_establishing_consensus || !is_consensus_established {
+			return Ok(());
+		}
+
+		let consensus_group = data.consensus_session.select_consensus_group()?.clone();
+		let mut other_consensus_group_nodes = consensus_group.clone();
+		other_consensus_group_nodes.remove(&self.core.meta.self_node_id);
+
+		let generation_session = GenerationSession::new(GenerationSessionParams {
+			id: self.core.meta.id.clone(),
+			self_node_id: self.core.meta.self_node_id.clone(),
+			key_storage: None,
+			cluster: Arc::new(SessionKeyGenerationTransport {
+				access_key: self.core.access_key.clone(),
+				cluster: self.core.cluster.clone(),
+				other_nodes_ids: other_consensus_group_nodes,
+			}),
+		});
+		generation_session.initialize(Public::default(), self.core.key_share.threshold, consensus_group)?;
+		data.generation_session = Some(generation_session);
+		data.state = SessionState::SessionKeyGeneration;
+
+		Ok(())
+	}
+
+	/// When session key related message is received.
+	pub fn on_generation_message(&self, sender: &NodeId, message: &SigningGenerationMessage) -> Result<(), Error> {
+		debug_assert!(self.core.meta.id == *message.session);
+		debug_assert!(self.core.access_key == *message.sub_session);
+		debug_assert!(sender != &self.core.meta.self_node_id);
+
+		let mut data = self.data.lock();
+
+		if let &GenerationMessage::InitializeSession(ref message) = &message.message {
+			if &self.core.meta.master_node_id != sender {
+				return Err(Error::InvalidMessage);
+			}
+
+			let consensus_group: BTreeSet<NodeId> = message.nodes.keys().cloned().map(Into::into).collect();
+			let mut other_consensus_group_nodes = consensus_group.clone();
+			other_consensus_group_nodes.remove(&self.core.meta.self_node_id);
+
+			let generation_session = GenerationSession::new(GenerationSessionParams {
+				id: self.core.meta.id.clone(),
+				self_node_id: self.core.meta.self_node_id.clone(),
+				key_storage: None,
+				cluster: Arc::new(SessionKeyGenerationTransport {
+					access_key: self.core.access_key.clone(),
+					cluster: self.core.cluster.clone(),
+					other_nodes_ids: other_consensus_group_nodes
+				}),
+			});
+			data.generation_session = Some(generation_session);
+			data.state = SessionState::SessionKeyGeneration;
+		}
+
+		{
+			let generation_session = data.generation_session.as_ref().ok_or(Error::InvalidStateForRequest)?;
+			let is_key_generating = generation_session.state() != GenerationSessionState::Finished;
+			generation_session.process_message(sender, &message.message)?;
+
+			let is_key_generated = generation_session.state() == GenerationSessionState::Finished;
+			if !is_key_generating || !is_key_generated {
+				return Ok(());
+			}
+		}
+
+		data.state = SessionState::SignatureComputing;
+		if self.core.meta.master_node_id != self.core.meta.self_node_id {
+			return Ok(());
+		}
+
+		let message_hash = data.message_hash
+			.expect("we are on master node; on master node message_hash is filled in initialize(); on_generation_message follows initialize; qed");
+		let joint_public_and_secret = data.generation_session.as_ref()
+			.expect("session key is generated before signature is computed; we are in SignatureComputing state; qed")
+			.joint_public_and_secret()
+			.expect("session key is generated before signature is computed; we are in SignatureComputing state; qed")?;
+		self.core.disseminate_jobs(&mut data.consensus_session, joint_public_and_secret.0, joint_public_and_secret.1, message_hash)
+	}
+
+	/// When partial signature is requested.
+	pub fn on_partial_signature_requested(&self, sender: &NodeId, message: &RequestPartialSignature) -> Result<(), Error> {
+		debug_assert!(self.core.meta.id == *message.session);
+		debug_assert!(self.core.access_key == *message.sub_session);
+		debug_assert!(sender != &self.core.meta.self_node_id);
+
+		let mut data = self.data.lock();
+
+		if sender != &self.core.meta.master_node_id {
+			return Err(Error::InvalidMessage);
+		}
+		if data.state != SessionState::SignatureComputing {
+			return Err(Error::InvalidStateForRequest);
+		}
+
+		let joint_public_and_secret = data.generation_session.as_ref()
+			.expect("session key is generated before signature is computed; we are in SignatureComputing state; qed")
+			.joint_public_and_secret()
+			.expect("session key is generated before signature is computed; we are in SignatureComputing state; qed")?;
+		let signing_job = SigningJob::new_on_slave(self.core.meta.self_node_id.clone(), self.core.key_share.clone(), joint_public_and_secret.0, joint_public_and_secret.1)?;
+		let signing_transport = self.core.signing_transport();
+
+		data.consensus_session.on_job_request(sender, PartialSigningRequest {
+			id: message.request_id.clone().into(),
+			message_hash: message.message_hash.clone().into(),
+			other_nodes_ids: message.nodes.iter().cloned().map(Into::into).collect(),
+		}, signing_job, signing_transport)
+	}
+
+	/// When partial signature is received.
+	pub fn on_partial_signature(&self, sender: &NodeId, message: &PartialSignature) -> Result<(), Error> {
+		debug_assert!(self.core.meta.id == *message.session);
+		debug_assert!(self.core.access_key == *message.sub_session);
+		debug_assert!(sender != &self.core.meta.self_node_id);
+
+		let mut data = self.data.lock();
+		data.consensus_session.on_job_response(sender, PartialSigningResponse {
+			request_id: message.request_id.clone().into(),
+			partial_signature: message.partial_signature.clone().into(),
+		})?;
+
+		if data.consensus_session.state() != ConsensusSessionState::Finished {
+			return Ok(());
+		}
+
+		self.core.cluster.broadcast(Message::Signing(SigningMessage::SigningSessionCompleted(SigningSessionCompleted {
+			session: self.core.meta.id.clone().into(),
+			sub_session: self.core.access_key.clone().into(),
+		})))?;
+
+		data.result = Some(Ok(data.consensus_session.result()?));
+		self.core.completed.notify_all();
+
+		Ok(())
+	}
+
+	/// When session is completed.
+	pub fn on_session_completed(&self, sender: &NodeId, message: &SigningSessionCompleted) -> Result<(), Error> {
+		debug_assert!(self.core.meta.id == *message.session);
+		debug_assert!(self.core.access_key == *message.sub_session);
+		debug_assert!(sender != &self.core.meta.self_node_id);
+
+		self.data.lock().consensus_session.on_session_completed(sender)
+	}
+
+	/// When error has occured on another node.
+	pub fn on_session_error(&self, sender: &NodeId, message: &SigningSessionError) -> Result<(), Error> {
+		self.process_node_error(Some(&sender), &message.error)
+	}
+
+	/// Process error from the other node.
+	fn process_node_error(&self, node: Option<&NodeId>, error: &String) -> Result<(), Error> {
+		let mut data = self.data.lock();
+		match {
+			match node {
+				Some(node) => data.consensus_session.on_node_error(node),
+				None => data.consensus_session.on_session_timeout(),
+			}
+		} {
+			Ok(false) => Ok(()),
+			Ok(true) => {
+				let message_hash = data.message_hash.as_ref().cloned()
+					.expect("on_node_error returned true; this means that jobs must be REsent; this means that jobs already have been sent; jobs are sent when message_hash.is_some(); qed");
+				let joint_public_and_secret = data.generation_session.as_ref()
+					.expect("on_node_error returned true; this means that jobs must be REsent; this means that jobs already have been sent; jobs are sent when message_hash.is_some(); qed")
+					.joint_public_and_secret()
+					.expect("on_node_error returned true; this means that jobs must be REsent; this means that jobs already have been sent; jobs are sent when message_hash.is_some(); qed")?;
+				let disseminate_result = self.core.disseminate_jobs(&mut data.consensus_session, joint_public_and_secret.0, joint_public_and_secret.1, message_hash);
+				match disseminate_result {
+					Ok(()) => Ok(()),
+					Err(err) => {
+						warn!("{}: signing session failed with error: {:?} from {:?}", &self.core.meta.self_node_id, error, node);
+
+						data.result = Some(Err(err.clone()));
+						self.core.completed.notify_all();
+						Err(err)
+					}
+				}
+			},
+			Err(err) => {
+				warn!("{}: signing session failed with error: {:?} from {:?}", &self.core.meta.self_node_id, error, node);
+
+				data.result = Some(Err(err.clone()));
+				self.core.completed.notify_all();
+				Err(err)
+			},
+		}
+	}
+}
+
+impl ClusterSession for SessionImpl {
+	fn is_finished(&self) -> bool {
+		let data = self.data.lock();
+		data.consensus_session.state() == ConsensusSessionState::Failed
+			|| data.consensus_session.state() == ConsensusSessionState::Finished
+	}
+
+	fn on_node_timeout(&self, node: &NodeId) {
+		// ignore error, only state matters
+		let _ = self.process_node_error(Some(node), &Error::NodeDisconnected.into());
+	}
+
+	fn on_session_timeout(&self) {
+		// ignore error, only state matters
+		let _ = self.process_node_error(None, &Error::NodeDisconnected.into());
+	}
+}
+
+impl Session for SessionImpl {
+	fn wait(&self) -> Result<(Secret, Secret), Error> {
+		let mut data = self.data.lock();
+		if !data.result.is_some() {
+			self.core.completed.wait(&mut data);
+		}
+
+		data.result.as_ref()
+			.expect("checked above or waited for completed; completed is only signaled when result.is_some(); qed")
+			.clone()
+	}
+}
+
+impl SessionKeyGenerationTransport {
+	fn map_message(&self, message: Message) -> Result<Message, Error> {
+		match message {
+			Message::Generation(message) => Ok(Message::Signing(SigningMessage::SigningGenerationMessage(SigningGenerationMessage {
+				session: message.session_id().clone().into(),
+				sub_session: self.access_key.clone().into(),
+				message: message,
+			}))),
+			_ => Err(Error::InvalidMessage),
+		}
+	}
+}
+
+impl Cluster for SessionKeyGenerationTransport {
+	fn broadcast(&self, message: Message) -> Result<(), Error> {
+		let message = self.map_message(message)?;
+		for to in &self.other_nodes_ids {
+			self.cluster.send(to, message.clone())?;
+		}
+		Ok(())
+	}
+
+	fn send(&self, to: &NodeId, message: Message) -> Result<(), Error> {
+		debug_assert!(self.other_nodes_ids.contains(to));
+		self.cluster.send(to, self.map_message(message)?)
+	}
+}
+
+impl SessionCore {
+	pub fn signing_transport(&self) -> SigningJobTransport {
+		SigningJobTransport {
+			id: self.meta.id.clone(),
+			access_key: self.access_key.clone(),
+			cluster: self.cluster.clone()
+		}
+	}
+
+	pub fn disseminate_jobs(&self, consensus_session: &mut SigningConsensusSession, session_public: Public, session_secret_share: Secret, message_hash: H256) -> Result<(), Error> {
+		let signing_job = SigningJob::new_on_master(self.meta.self_node_id.clone(), self.key_share.clone(), session_public, session_secret_share, message_hash)?;
+		consensus_session.disseminate_jobs(signing_job, self.signing_transport())
+	}
+}
+
+impl JobTransport for SigningConsensusTransport {
+	type PartialJobRequest=Signature;
+	type PartialJobResponse=bool;
+
+	fn send_partial_request(&self, node: &NodeId, request: Signature) -> Result<(), Error> {
+		self.cluster.send(node, Message::Signing(SigningMessage::SigningConsensusMessage(SigningConsensusMessage {
+			session: self.id.clone().into(),
+			sub_session: self.access_key.clone().into(),
+			message: ConsensusMessage::InitializeConsensusSession(InitializeConsensusSession {
+				requestor_signature: request.into(),
+			})
+		})))
+	}
+
+	fn send_partial_response(&self, node: &NodeId, response: bool) -> Result<(), Error> {
+		self.cluster.send(node, Message::Signing(SigningMessage::SigningConsensusMessage(SigningConsensusMessage {
+			session: self.id.clone().into(),
+			sub_session: self.access_key.clone().into(),
+			message: ConsensusMessage::ConfirmConsensusInitialization(ConfirmConsensusInitialization {
+				is_confirmed: response,
+			})
+		})))
+	}
+}
+
+impl JobTransport for SigningJobTransport {
+	type PartialJobRequest=PartialSigningRequest;
+	type PartialJobResponse=PartialSigningResponse;
+
+	fn send_partial_request(&self, node: &NodeId, request: PartialSigningRequest) -> Result<(), Error> {
+		self.cluster.send(node, Message::Signing(SigningMessage::RequestPartialSignature(RequestPartialSignature {
+			session: self.id.clone().into(),
+			sub_session: self.access_key.clone().into(),
+			request_id: request.id.into(),
+			message_hash: request.message_hash.into(),
+			nodes: request.other_nodes_ids.into_iter().map(Into::into).collect(),
+		})))
+	}
+
+	fn send_partial_response(&self, node: &NodeId, response: PartialSigningResponse) -> Result<(), Error> {
+		self.cluster.send(node, Message::Signing(SigningMessage::PartialSignature(PartialSignature {
+			session: self.id.clone().into(),
+			sub_session: self.access_key.clone().into(),
+			request_id: response.request_id.into(),
+			partial_signature: response.partial_signature.into(),
+		})))
+	}
+}
+
+#[cfg(test)]
+mod tests {
+	use std::sync::Arc;
+	use std::collections::{BTreeMap, VecDeque};
+	use ethkey::{self, Random, Generator, Public};
+	use util::H256;
+	use super::super::super::acl_storage::tests::DummyAclStorage;
+	use key_server_cluster::{NodeId, SessionId, SessionMeta, Error, KeyStorage};
+	use key_server_cluster::cluster::tests::DummyCluster;
+	use key_server_cluster::generation_session::{Session as GenerationSession};
+	use key_server_cluster::generation_session::tests::MessageLoop as KeyGenerationMessageLoop;
+	use key_server_cluster::math;
+	use key_server_cluster::message::{Message, SigningMessage};
+	use key_server_cluster::signing_session::{Session, SessionImpl, SessionParams};
+
+	struct Node {
+		pub node_id: NodeId,
+		pub cluster: Arc<DummyCluster>,
+		pub session: SessionImpl,
+	}
+
+	struct MessageLoop {
+		pub session_id: SessionId,
+		pub nodes: BTreeMap<NodeId, Node>,
+		pub queue: VecDeque<(NodeId, NodeId, Message)>,
+	}
+
+	impl MessageLoop {
+		pub fn new(gl: &KeyGenerationMessageLoop) -> Self {
+			let mut nodes = BTreeMap::new();
+			let session_id = gl.session_id.clone();
+			let requester = Random.generate().unwrap();
+			let signature = Some(ethkey::sign(requester.secret(), &SessionId::default()).unwrap());
+			let master_node_id = gl.nodes.keys().nth(0).unwrap().clone();
+			for (i, (gl_node_id, gl_node)) in gl.nodes.iter().enumerate() {
+				let acl_storage = Arc::new(DummyAclStorage::default());
+				let cluster = Arc::new(DummyCluster::new(gl_node_id.clone()));
+				let session = SessionImpl::new(SessionParams {
+					meta: SessionMeta {
+						id: session_id.clone(),
+						self_node_id: gl_node_id.clone(),
+						master_node_id: master_node_id.clone(),
+						threshold: gl_node.key_storage.get(&session_id).unwrap().threshold,
+					},
+					access_key: "834cb736f02d9c968dfaf0c37658a1d86ff140554fc8b59c9fdad5a8cf810eec".parse().unwrap(),
+					key_share: gl_node.key_storage.get(&session_id).unwrap(),
+					acl_storage: acl_storage,
+					cluster: cluster.clone(),
+				}, if i == 0 { signature.clone() } else { None }).unwrap();
+				nodes.insert(gl_node_id.clone(), Node { node_id: gl_node_id.clone(), cluster: cluster, session: session });
+			}
+
+			let nodes_ids: Vec<_> = nodes.keys().cloned().collect();
+			for node in nodes.values() {
+				for node_id in &nodes_ids {
+					node.cluster.add_node(node_id.clone());
+				}
+			}
+
+			MessageLoop {
+				session_id: session_id,
+				nodes: nodes,
+				queue: VecDeque::new(),
+			}
+		}
+
+		pub fn master(&self) -> &SessionImpl {
+			&self.nodes.values().nth(0).unwrap().session
+		}
+
+		pub fn take_message(&mut self) -> Option<(NodeId, NodeId, Message)> {
+			self.nodes.values()
+				.filter_map(|n| n.cluster.take_message().map(|m| (n.node_id.clone(), m.0, m.1)))
+				.nth(0)
+				.or_else(|| self.queue.pop_front())
+		}
+
+		pub fn process_message(&mut self, mut msg: (NodeId, NodeId, Message)) -> Result<(), Error> {
+			let mut is_queued_message = false;
+			loop {
+				match {
+					match msg.2 {
+						Message::Signing(SigningMessage::SigningConsensusMessage(ref message)) => self.nodes[&msg.1].session.on_consensus_message(&msg.0, &message),
+						Message::Signing(SigningMessage::SigningGenerationMessage(ref message)) => self.nodes[&msg.1].session.on_generation_message(&msg.0, &message),
+						Message::Signing(SigningMessage::RequestPartialSignature(ref message)) => self.nodes[&msg.1].session.on_partial_signature_requested(&msg.0, &message),
+						Message::Signing(SigningMessage::PartialSignature(ref message)) => self.nodes[&msg.1].session.on_partial_signature(&msg.0, &message),
+						Message::Signing(SigningMessage::SigningSessionCompleted(ref message)) => self.nodes[&msg.1].session.on_session_completed(&msg.0, &message),
+						_ => panic!("unexpected"),
+					}
+				} {
+					Ok(_) => {
+						if let Some(message) = self.queue.pop_front() {
+							msg = message;
+							is_queued_message = true;
+							continue;
+						}
+						return Ok(());
+					},
+					Err(Error::TooEarlyForRequest) => {
+						if is_queued_message {
+							self.queue.push_front(msg);
+						} else {
+							self.queue.push_back(msg);
+						}
+						return Ok(());
+					},
+					Err(err) => return Err(err),
+				}
+			}
+		}
+	}
+
+	#[test]
+	fn complete_gen_sign_session() {
+		let test_cases = [(0, 1), (0, 5), (2, 5), (3, 5)];
+		for &(threshold, num_nodes) in &test_cases {
+			// run key generation sessions
+			let mut gl = KeyGenerationMessageLoop::new(num_nodes);
+			gl.master().initialize(Public::default(), threshold, gl.nodes.keys().cloned().collect()).unwrap();
+			while let Some((from, to, message)) = gl.take_message() {
+				gl.process_message((from, to, message)).unwrap();
+			}
+
+			// run signing session
+			let message_hash = H256::from(777);
+			let mut sl = MessageLoop::new(&gl);
+			sl.master().initialize(message_hash).unwrap();
+			while let Some((from, to, message)) = sl.take_message() {
+				sl.process_message((from, to, message)).unwrap();
+			}
+
+			// verify signature
+			let public = gl.master().joint_public_and_secret().unwrap().unwrap().0;
+			let signature = sl.master().wait().unwrap();
+			assert!(math::verify_signature(&public, &signature, &message_hash).unwrap());
+		}
+	}
+}

secret_store/src/key_storage.rs

@@ -19,12 +19,17 @@ use std::collections::BTreeMap;
 use serde_json;
 use ethkey::{Secret, Public};
 use util::Database;
-use types::all::{Error, ServiceConfiguration, DocumentAddress, NodeId};
+use types::all::{Error, ServiceConfiguration, ServerKeyId, NodeId};
 use serialization::{SerializablePublic, SerializableSecret};
 
+/// Key of version value.
+const DB_META_KEY_VERSION: &'static [u8; 7] = b"version";
+
 #[derive(Debug, Clone, PartialEq)]
 /// Encrypted key share, stored by key storage on the single key server.
 pub struct DocumentKeyShare {
+	/// Author of the entry.
+	pub author: Public,
 	/// Decryption threshold (at least threshold + 1 nodes are required to decrypt data).
 	pub threshold: usize,
 	/// Nodes ids numbers.
@@ -32,19 +37,21 @@ pub struct DocumentKeyShare {
 	/// Node secret share.
 	pub secret_share: Secret,
 	/// Common (shared) encryption point.
-	pub common_point: Public,
+	pub common_point: Option<Public>,
 	/// Encrypted point.
-	pub encrypted_point: Public,
+	pub encrypted_point: Option<Public>,
 }
 
 /// Document encryption keys storage
 pub trait KeyStorage: Send + Sync {
 	/// Insert document encryption key
-	fn insert(&self, document: DocumentAddress, key: DocumentKeyShare) -> Result<(), Error>;
+	fn insert(&self, document: ServerKeyId, key: DocumentKeyShare) -> Result<(), Error>;
+	/// Update document encryption key
+	fn update(&self, document: ServerKeyId, key: DocumentKeyShare) -> Result<(), Error>;
 	/// Get document encryption key
-	fn get(&self, document: &DocumentAddress) -> Result<DocumentKeyShare, Error>;
+	fn get(&self, document: &ServerKeyId) -> Result<DocumentKeyShare, Error>;
 	/// Check if storage contains document encryption key
-	fn contains(&self, document: &DocumentAddress) -> bool;
+	fn contains(&self, document: &ServerKeyId) -> bool;
 }
 
 /// Persistent document encryption keys storage
@@ -53,8 +60,8 @@ pub struct PersistentKeyStorage {
 }
 
 #[derive(Serialize, Deserialize)]
-/// Encrypted key share, as it is stored by key storage on the single key server.
+/// V0 of encrypted key share, as it is stored by key storage on the single key server.
-struct SerializableDocumentKeyShare {
+struct SerializableDocumentKeyShareV0 {
 	/// Decryption threshold (at least threshold + 1 nodes are required to decrypt data).
 	pub threshold: usize,
 	/// Nodes ids numbers.
@@ -67,6 +74,23 @@ struct SerializableDocumentKeyShare {
 	pub encrypted_point: SerializablePublic,
 }
 
+#[derive(Serialize, Deserialize)]
+/// V1 of encrypted key share, as it is stored by key storage on the single key server.
+struct SerializableDocumentKeyShareV1 {
+	/// Authore of the entry.
+	pub author: SerializablePublic,
+	/// Decryption threshold (at least threshold + 1 nodes are required to decrypt data).
+	pub threshold: usize,
+	/// Nodes ids numbers.
+	pub id_numbers: BTreeMap<SerializablePublic, SerializableSecret>,
+	/// Node secret share.
+	pub secret_share: SerializableSecret,
+	/// Common (shared) encryption point.
+	pub common_point: Option<SerializablePublic>,
+	/// Encrypted point.
+	pub encrypted_point: Option<SerializablePublic>,
+}
+
 impl PersistentKeyStorage {
 	/// Create new persistent document encryption keys storage
 	pub fn new(config: &ServiceConfiguration) -> Result<Self, Error> {
@@ -74,57 +98,96 @@ impl PersistentKeyStorage {
 		db_path.push("db");
 		let db_path = db_path.to_str().ok_or(Error::Database("Invalid secretstore path".to_owned()))?;
 
+		let db = Database::open_default(&db_path).map_err(Error::Database)?;
+		let db = upgrade_db(db)?;
+
 		Ok(PersistentKeyStorage {
-			db: Database::open_default(&db_path).map_err(Error::Database)?,
+			db: db,
 		})
 	}
 }
 
+fn upgrade_db(db: Database) -> Result<Database, Error> {
+	let version = db.get(None, DB_META_KEY_VERSION).map_err(Error::Database)?;
+	let version = version.and_then(|v| v.get(0).cloned()).unwrap_or(0);
+	match version {
+		0 => {
+			let mut batch = db.transaction();
+			batch.put(None, DB_META_KEY_VERSION, &[1]);
+			for (db_key, db_value) in db.iter(None).into_iter().flat_map(|inner| inner) {
+				let v0_key = serde_json::from_slice::<SerializableDocumentKeyShareV0>(&db_value).map_err(|e| Error::Database(e.to_string()))?;
+				let v1_key = SerializableDocumentKeyShareV1 {
+					// author is used in separate generation + encrypt sessions.
+					// in v0 there have been only simultaneous GenEnc sessions.
+					author: Public::default().into(), 
+					threshold: v0_key.threshold,
+					id_numbers: v0_key.id_numbers,
+					secret_share: v0_key.secret_share,
+					common_point: Some(v0_key.common_point),
+					encrypted_point: Some(v0_key.encrypted_point),
+				};
+				let db_value = serde_json::to_vec(&v1_key).map_err(|e| Error::Database(e.to_string()))?;
+				batch.put(None, &*db_key, &*db_value);
+			}
+			db.write(batch).map_err(Error::Database)?;
+			Ok(db)
+		},
+		1 => Ok(db),
+		_ => Err(Error::Database(format!("unsupported SecretStore database version:? {}", version))),
+	}
+}
+
 impl KeyStorage for PersistentKeyStorage {
-	fn insert(&self, document: DocumentAddress, key: DocumentKeyShare) -> Result<(), Error> {
+	fn insert(&self, document: ServerKeyId, key: DocumentKeyShare) -> Result<(), Error> {
-		let key: SerializableDocumentKeyShare = key.into();
+		let key: SerializableDocumentKeyShareV1 = key.into();
 		let key = serde_json::to_vec(&key).map_err(|e| Error::Database(e.to_string()))?;
 		let mut batch = self.db.transaction();
 		batch.put(None, &document, &key);
 		self.db.write(batch).map_err(Error::Database)
 	}
 
-	fn get(&self, document: &DocumentAddress) -> Result<DocumentKeyShare, Error> {
+	fn update(&self, document: ServerKeyId, key: DocumentKeyShare) -> Result<(), Error> {
+		self.insert(document, key)
+	}
+
+	fn get(&self, document: &ServerKeyId) -> Result<DocumentKeyShare, Error> {
 		self.db.get(None, document)
 			.map_err(Error::Database)?
 			.ok_or(Error::DocumentNotFound)
 			.map(|key| key.into_vec())
-			.and_then(|key| serde_json::from_slice::<SerializableDocumentKeyShare>(&key).map_err(|e| Error::Database(e.to_string())))
+			.and_then(|key| serde_json::from_slice::<SerializableDocumentKeyShareV1>(&key).map_err(|e| Error::Database(e.to_string())))
 			.map(Into::into)
 	}
 
-	fn contains(&self, document: &DocumentAddress) -> bool {
+	fn contains(&self, document: &ServerKeyId) -> bool {
 		self.db.get(None, document)
 			.map(|k| k.is_some())
 			.unwrap_or(false)
 	}
 }
 
-impl From<DocumentKeyShare> for SerializableDocumentKeyShare {
+impl From<DocumentKeyShare> for SerializableDocumentKeyShareV1 {
 	fn from(key: DocumentKeyShare) -> Self {
-		SerializableDocumentKeyShare {
+		SerializableDocumentKeyShareV1 {
+			author: key.author.into(),
 			threshold: key.threshold,
 			id_numbers: key.id_numbers.into_iter().map(|(k, v)| (k.into(), v.into())).collect(),
 			secret_share: key.secret_share.into(),
-			common_point: key.common_point.into(),
+			common_point: key.common_point.map(Into::into),
-			encrypted_point: key.encrypted_point.into(),
+			encrypted_point: key.encrypted_point.map(Into::into),
 		}
 	}
 }
 
-impl From<SerializableDocumentKeyShare> for DocumentKeyShare {
+impl From<SerializableDocumentKeyShareV1> for DocumentKeyShare {
-	fn from(key: SerializableDocumentKeyShare) -> Self {
+	fn from(key: SerializableDocumentKeyShareV1) -> Self {
 		DocumentKeyShare {
+			author: key.author.into(),
 			threshold: key.threshold,
 			id_numbers: key.id_numbers.into_iter().map(|(k, v)| (k.into(), v.into())).collect(),
 			secret_share: key.secret_share.into(),
-			common_point: key.common_point.into(),
+			common_point: key.common_point.map(Into::into),
-			encrypted_point: key.encrypted_point.into(),
+			encrypted_point: key.encrypted_point.map(Into::into),
 		}
 	}
 }
@@ -133,28 +196,36 @@ impl From<SerializableDocumentKeyShare> for DocumentKeyShare {
 pub mod tests {
 	use std::collections::{BTreeMap, HashMap};
 	use parking_lot::RwLock;
+	use serde_json;
 	use devtools::RandomTempPath;
-	use ethkey::{Random, Generator};
+	use ethkey::{Random, Generator, Public, Secret};
-	use super::super::types::all::{Error, NodeAddress, ServiceConfiguration, ClusterConfiguration, DocumentAddress};
+	use util::Database;
-	use super::{KeyStorage, PersistentKeyStorage, DocumentKeyShare};
+	use super::super::types::all::{Error, NodeAddress, ServiceConfiguration, ClusterConfiguration, ServerKeyId};
+	use super::{DB_META_KEY_VERSION, KeyStorage, PersistentKeyStorage, DocumentKeyShare,
+		SerializableDocumentKeyShareV0, SerializableDocumentKeyShareV1, upgrade_db};
 
 	#[derive(Default)]
 	/// In-memory document encryption keys storage
 	pub struct DummyKeyStorage {
-		keys: RwLock<HashMap<DocumentAddress, DocumentKeyShare>>,
+		keys: RwLock<HashMap<ServerKeyId, DocumentKeyShare>>,
 	}
 
 	impl KeyStorage for DummyKeyStorage {
-		fn insert(&self, document: DocumentAddress, key: DocumentKeyShare) -> Result<(), Error> {
+		fn insert(&self, document: ServerKeyId, key: DocumentKeyShare) -> Result<(), Error> {
 			self.keys.write().insert(document, key);
 			Ok(())
 		}
 
-		fn get(&self, document: &DocumentAddress) -> Result<DocumentKeyShare, Error> {
+		fn update(&self, document: ServerKeyId, key: DocumentKeyShare) -> Result<(), Error> {
+			self.keys.write().insert(document, key);
+			Ok(())
+		}
+
+		fn get(&self, document: &ServerKeyId) -> Result<DocumentKeyShare, Error> {
 			self.keys.read().get(document).cloned().ok_or(Error::DocumentNotFound)
 		}
 
-		fn contains(&self, document: &DocumentAddress) -> bool {
+		fn contains(&self, document: &ServerKeyId) -> bool {
 			self.keys.read().contains_key(document)
 		}
 	}
@@ -180,27 +251,29 @@ pub mod tests {
 			},
 		};
 		
-		let key1 = DocumentAddress::from(1);
+		let key1 = ServerKeyId::from(1);
 		let value1 = DocumentKeyShare {
+			author: Public::default(),
 			threshold: 100,
 			id_numbers: vec![
 				(Random.generate().unwrap().public().clone(), Random.generate().unwrap().secret().clone())
 			].into_iter().collect(),
 			secret_share: Random.generate().unwrap().secret().clone(),
-			common_point: Random.generate().unwrap().public().clone(),
+			common_point: Some(Random.generate().unwrap().public().clone()),
-			encrypted_point: Random.generate().unwrap().public().clone(),
+			encrypted_point: Some(Random.generate().unwrap().public().clone()),
 		};
-		let key2 = DocumentAddress::from(2);
+		let key2 = ServerKeyId::from(2);
 		let value2 = DocumentKeyShare {
+			author: Public::default(),
 			threshold: 200,
 			id_numbers: vec![
 				(Random.generate().unwrap().public().clone(), Random.generate().unwrap().secret().clone())
 			].into_iter().collect(),
 			secret_share: Random.generate().unwrap().secret().clone(),
-			common_point: Random.generate().unwrap().public().clone(),
+			common_point: Some(Random.generate().unwrap().public().clone()),
-			encrypted_point: Random.generate().unwrap().public().clone(),
+			encrypted_point: Some(Random.generate().unwrap().public().clone()),
 		};
-		let key3 = DocumentAddress::from(3);
+		let key3 = ServerKeyId::from(3);
 
 		let key_storage = PersistentKeyStorage::new(&config).unwrap();
 		key_storage.insert(key1.clone(), value1.clone()).unwrap();
@@ -215,4 +288,43 @@ pub mod tests {
 		assert_eq!(key_storage.get(&key2), Ok(value2));
 		assert_eq!(key_storage.get(&key3), Err(Error::DocumentNotFound));
 	}
+
+	#[test]
+	fn upgrade_db_0_to_1() {
+		let db_path = RandomTempPath::create_dir();
+		let db = Database::open_default(db_path.as_str()).unwrap();
+
+		// prepare v0 database
+		{
+			let key = serde_json::to_vec(&SerializableDocumentKeyShareV0 {
+				threshold: 777,
+				id_numbers: vec![(
+					"b486d3840218837b035c66196ecb15e6b067ca20101e11bd5e626288ab6806ecc70b8307012626bd512bad1559112d11d21025cef48cc7a1d2f3976da08f36c8".into(),
+					"281b6bf43cb86d0dc7b98e1b7def4a80f3ce16d28d2308f934f116767306f06c".parse::<Secret>().unwrap().into(),
+				)].into_iter().collect(),
+				secret_share: "00125d85a05e5e63e214cb60fe63f132eec8a103aa29266b7e6e6c5b7597230b".parse::<Secret>().unwrap().into(),
+				common_point: "99e82b163b062d55a64085bacfd407bb55f194ba5fb7a1af9c34b84435455520f1372e0e650a4f91aed0058cb823f62146ccb5599c8d13372c300dea866b69fc".into(),
+				encrypted_point: "7e05df9dd077ec21ed4bc45c9fe9e0a43d65fa4be540630de615ced5e95cf5c3003035eb713317237d7667feeeb64335525158f5f7411f67aca9645169ea554c".into(),
+			}).unwrap();
+			let mut batch = db.transaction();
+			batch.put(None, &[7], &key);
+			db.write(batch).unwrap();
+		}
+
+		// upgrade database
+		let db = upgrade_db(db).unwrap();
+
+		// check upgrade
+		assert_eq!(db.get(None, DB_META_KEY_VERSION).unwrap().unwrap()[0], 1);
+		let key = serde_json::from_slice::<SerializableDocumentKeyShareV1>(&db.get(None, &[7]).unwrap().map(|key| key.to_vec()).unwrap()).unwrap();
+		assert_eq!(Public::default(), key.author.clone().into());
+		assert_eq!(777, key.threshold);
+		assert_eq!(vec![(
+			"b486d3840218837b035c66196ecb15e6b067ca20101e11bd5e626288ab6806ecc70b8307012626bd512bad1559112d11d21025cef48cc7a1d2f3976da08f36c8".parse::<Public>().unwrap(),
+			"281b6bf43cb86d0dc7b98e1b7def4a80f3ce16d28d2308f934f116767306f06c".parse::<Secret>().unwrap(),
+		)], key.id_numbers.clone().into_iter().map(|(k, v)| (k.into(), v.into())).collect::<Vec<(Public, Secret)>>());
+		assert_eq!("00125d85a05e5e63e214cb60fe63f132eec8a103aa29266b7e6e6c5b7597230b".parse::<Secret>().unwrap(), key.secret_share.into());
+		assert_eq!(Some("99e82b163b062d55a64085bacfd407bb55f194ba5fb7a1af9c34b84435455520f1372e0e650a4f91aed0058cb823f62146ccb5599c8d13372c300dea866b69fc".parse::<Public>().unwrap()), key.common_point.clone().map(Into::into));
+		assert_eq!(Some("7e05df9dd077ec21ed4bc45c9fe9e0a43d65fa4be540630de615ced5e95cf5c3003035eb713317237d7667feeeb64335525158f5f7411f67aca9645169ea554c".parse::<Public>().unwrap()), key.encrypted_point.clone().map(Into::into));
+	}
 }

secret_store/src/lib.rs

@@ -60,7 +60,7 @@ mod serialization;
 use std::sync::Arc;
 use ethcore::client::Client;
 
-pub use types::all::{DocumentAddress, DocumentKey, DocumentEncryptedKey, RequestSignature, Public,
+pub use types::all::{ServerKeyId, EncryptedDocumentKey, RequestSignature, Public,
 	Error, NodeAddress, ServiceConfiguration, ClusterConfiguration};
 pub use traits::{KeyServer};
 

secret_store/src/serialization.rs

@@ -23,9 +23,12 @@ use serde::de::{Visitor, Error as SerdeError};
 use ethkey::{Public, Secret, Signature};
 use util::{H256, Bytes};
 
+/// Serializable message hash.
+pub type SerializableMessageHash = SerializableH256;
+
 #[derive(Clone, Debug, Serialize, Deserialize)]
 /// Serializable shadow decryption result.
-pub struct SerializableDocumentEncryptedKeyShadow {
+pub struct SerializableEncryptedDocumentKeyShadow {
 	/// Decrypted secret point. It is partially decrypted if shadow decrpytion was requested.
 	pub decrypted_secret: SerializablePublic,
 	/// Shared common point.

secret_store/src/traits.rs

@@ -14,21 +14,63 @@
 // You should have received a copy of the GNU General Public License
 // along with Parity.  If not, see <http://www.gnu.org/licenses/>.
 
-use types::all::{Error, RequestSignature, DocumentAddress, DocumentEncryptedKey, DocumentEncryptedKeyShadow};
+use types::all::{Error, Public, ServerKeyId, MessageHash, EncryptedMessageSignature, RequestSignature, EncryptedDocumentKey,
+	EncryptedDocumentKeyShadow};
 
-#[ipc(client_ident="RemoteKeyServer")]
+/// Server key (SK) generator.
-/// Secret store key server
+pub trait ServerKeyGenerator {
-pub trait KeyServer: Send + Sync {
+	/// Generate new SK.
-	/// Generate encryption key for given document.
+	/// `key_id` is the caller-provided identifier of generated SK.
-	fn generate_document_key(&self, signature: &RequestSignature, document: &DocumentAddress, threshold: usize) -> Result<DocumentEncryptedKey, Error>;
+	/// `signature` is `key_id`, signed with caller public key.
-	/// Request encryption key of given document for given requestor
+	/// `threshold + 1` is the minimal number of nodes, required to restore private key.
-	fn document_key(&self, signature: &RequestSignature, document: &DocumentAddress) -> Result<DocumentEncryptedKey, Error>;
+	/// Result is a public portion of SK.
-	/// Request encryption key of given document for given requestor.
+	fn generate_key(&self, key_id: &ServerKeyId, signature: &RequestSignature, threshold: usize) -> Result<Public, Error>;
-	/// This method does not reveal document_key to any KeyServer, but it requires additional actions on client.
+}
-	/// To calculate decrypted key on client:
+
+/// Document key (DK) server.
+pub trait DocumentKeyServer: ServerKeyGenerator {
+	/// Store externally generated DK.
+	/// `key_id` is identifier of previously generated SK.
+	/// `signature` is key_id, signed with caller public key. Caller must be the same as in the `generate_key` call.
+	/// `common_point` is a result of `k * T` expression, where `T` is generation point and `k` is random scalar in EC field.
+	/// `encrypted_document_key` is a result of `M + k * y` expression, where `M` is unencrypted document key (point on EC),
+	///   `k` is the same scalar used in `common_point` calculation and `y` is previously generated public part of SK.
+	fn store_document_key(&self, key_id: &ServerKeyId, signature: &RequestSignature, common_point: Public, encrypted_document_key: Public) -> Result<(), Error>;
+	/// Generate and store both SK and DK. This is a shortcut for consequent calls of `generate_key` and `store_document_key`.
+	/// The only difference is that DK is generated by DocumentKeyServer (which might be considered unsafe).
+	/// `key_id` is the caller-provided identifier of generated SK.
+	/// `signature` is `key_id`, signed with caller public key.
+	/// `threshold + 1` is the minimal number of nodes, required to restore private key.
+	/// Result is a DK, encrypted with caller public key.
+	fn generate_document_key(&self, key_id: &ServerKeyId, signature: &RequestSignature, threshold: usize) -> Result<EncryptedDocumentKey, Error>;
+	/// Restore previously stored DK.
+	/// DK is decrypted on the key server (which might be considered unsafe), and then encrypted with caller public key.
+	/// `key_id` is identifier of previously generated SK.
+	/// `signature` is key_id, signed with caller public key. Caller must be on ACL for this function to succeed.
+	/// Result is a DK, encrypted with caller public key.
+	fn restore_document_key(&self, key_id: &ServerKeyId, signature: &RequestSignature) -> Result<EncryptedDocumentKey, Error>;
+	/// Restore previously stored DK.
+	/// To decrypt DK on client:
 	/// 1) use requestor secret key to decrypt secret coefficients from result.decrypt_shadows
 	/// 2) calculate decrypt_shadows_sum = sum of all secrets from (1)
 	/// 3) calculate decrypt_shadow_point: decrypt_shadows_sum * result.common_point
 	/// 4) calculate decrypted_secret: result.decrypted_secret + decrypt_shadow_point
-	fn document_key_shadow(&self, signature: &RequestSignature, document: &DocumentAddress) -> Result<DocumentEncryptedKeyShadow, Error>;
+	/// Result is a DK shadow.
+	fn restore_document_key_shadow(&self, key_id: &ServerKeyId, signature: &RequestSignature) -> Result<EncryptedDocumentKeyShadow, Error>;
+}
+
+/// Message signer.
+pub trait MessageSigner: ServerKeyGenerator {
+	/// Sign message with previously generated SK.
+	/// `key_id` is the caller-provided identifier of generated SK.
+	/// `signature` is `key_id`, signed with caller public key.
+	/// `message` is the message to be signed.
+	/// Result is a signed message, encrypted with caller public key.
+	fn sign_message(&self, key_id: &ServerKeyId, signature: &RequestSignature, message: MessageHash) -> Result<EncryptedMessageSignature, Error>;
+}
+
+
+#[ipc(client_ident="RemoteKeyServer")]
+/// Key server.
+pub trait KeyServer: DocumentKeyServer + MessageSigner + Send + Sync {
 }

secret_store/src/types/all.rs

@@ -24,12 +24,14 @@ use key_server_cluster;
 
 /// Node id.
 pub type NodeId = ethkey::Public;
-/// Document address type.
+/// Server key id. When key is used to encrypt document, it could be document contents hash.
-pub type DocumentAddress = util::H256;
+pub type ServerKeyId = util::H256;
-/// Document key type.
+/// Encrypted document key type.
-pub type DocumentKey = util::Bytes;
+pub type EncryptedDocumentKey = util::Bytes;
-/// Encrypted key type.
+/// Message hash.
-pub type DocumentEncryptedKey = util::Bytes;
+pub type MessageHash = util::H256;
+/// Message signature.
+pub type EncryptedMessageSignature = util::Bytes;
 /// Request signature type.
 pub type RequestSignature = ethkey::Signature;
 /// Public key type.
@@ -95,7 +97,7 @@ pub struct ClusterConfiguration {
 #[derive(Clone, Debug, PartialEq)]
 #[binary]
 /// Shadow decryption result.
-pub struct DocumentEncryptedKeyShadow {
+pub struct EncryptedDocumentKeyShadow {
 	/// Decrypted secret point. It is partially decrypted if shadow decrpytion was requested.
 	pub decrypted_secret: ethkey::Public,
 	/// Shared common point.