Merge remote-tracking branch 'origin/master' into fix-tx-rpc

2016-12-05 10:44:19 -08:00
parent f77a9aa007 ad36743122
commit 5e1fdc4b11
211 changed files with 3256 additions and 3329 deletions
--- a/ethcore/res/authority_round.json
+++ b/ethcore/res/authority_round.json
@@ -21,8 +21,7 @@
 	"genesis": {
 		"seal": {
 			"generic": {
-				"fields": 2,
-				"rlp": "0x200"
+				"rlp": "0xc28080"
 			}
 		},
 		"difficulty": "0x20000",
--- a/ethcore/res/instant_seal.json
+++ b/ethcore/res/instant_seal.json
@@ -12,7 +12,6 @@
 	"genesis": {
 		"seal": {
 			"generic": {
-				"fields": 0,
 				"rlp": "0x0"
 			}
 		},
--- a/ethcore/src/account_provider/mod.rs
+++ b/ethcore/src/account_provider/mod.rs
@@ -16,9 +16,12 @@

 //! Account management.

-use std::{fs, fmt};
+mod stores;
+
+use self::stores::{AddressBook, DappsSettingsStore};
+
+use std::fmt;
 use std::collections::HashMap;
-use std::path::PathBuf;
 use std::time::{Instant, Duration};
 use util::{Mutex, RwLock};
 use ethstore::{SecretStore, Error as SSError, SafeAccount, EthStore};
@@ -91,84 +94,16 @@ impl KeyDirectory for NullDir {
 	}
 }

-/// Disk-backed map from Address to String. Uses JSON.
-struct AddressBook {
-	path: PathBuf,
-	cache: HashMap<Address, AccountMeta>,
-	transient: bool,
-}
-
-impl AddressBook {
-	pub fn new(path: String) -> Self {
-		trace!(target: "addressbook", "new({})", path);
-		let mut path: PathBuf = path.into();
-		path.push("address_book.json");
-		trace!(target: "addressbook", "path={:?}", path);
-		let mut r = AddressBook {
-			path: path,
-			cache: HashMap::new(),
-			transient: false,
-		};
-		r.revert();
-		r
-	}
-
-	pub fn transient() -> Self {
-		let mut book = AddressBook::new(Default::default());
-		book.transient = true;
-		book
-	}
-
-	pub fn get(&self) -> HashMap<Address, AccountMeta> {
-		self.cache.clone()
-	}
-
-	pub fn set_name(&mut self, a: Address, name: String) {
-		let mut x = self.cache.get(&a)
-			.cloned()
-			.unwrap_or_else(|| AccountMeta {name: Default::default(), meta: "{}".to_owned(), uuid: None});
-		x.name = name;
-		self.cache.insert(a, x);
-		self.save();
-	}
-
-	pub fn set_meta(&mut self, a: Address, meta: String) {
-		let mut x = self.cache.get(&a)
-			.cloned()
-			.unwrap_or_else(|| AccountMeta {name: "Anonymous".to_owned(), meta: Default::default(), uuid: None});
-		x.meta = meta;
-		self.cache.insert(a, x);
-		self.save();
-	}
-
-	fn revert(&mut self) {
-		if self.transient { return; }
-		trace!(target: "addressbook", "revert");
-		let _ = fs::File::open(self.path.clone())
-			.map_err(|e| trace!(target: "addressbook", "Couldn't open address book: {}", e))
-			.and_then(|f| AccountMeta::read_address_map(&f)
-				.map_err(|e| warn!(target: "addressbook", "Couldn't read address book: {}", e))
-				.and_then(|m| { self.cache = m; Ok(()) })
-			);
-	}
-
-	fn save(&mut self) {
-		if self.transient { return; }
-		trace!(target: "addressbook", "save");
-		let _ = fs::File::create(self.path.clone())
-			.map_err(|e| warn!(target: "addressbook", "Couldn't open address book for writing: {}", e))
-			.and_then(|mut f| AccountMeta::write_address_map(&self.cache, &mut f)
-				.map_err(|e| warn!(target: "addressbook", "Couldn't write to address book: {}", e))
-			);
-	}
-}
+/// Dapp identifier
+pub type DappId = String;

 /// Account management.
 /// Responsible for unlocking accounts.
 pub struct AccountProvider {
 	unlocked: Mutex<HashMap<Address, AccountData>>,
 	sstore: Box<SecretStore>,
-	address_book: Mutex<AddressBook>,
+	address_book: RwLock<AddressBook>,
+	dapps_settings: RwLock<DappsSettingsStore>,
 }

 impl AccountProvider {
@@ -176,7 +111,8 @@ impl AccountProvider {
 	pub fn new(sstore: Box<SecretStore>) -> Self {
 		AccountProvider {
 			unlocked: Mutex::new(HashMap::new()),
-			address_book: Mutex::new(AddressBook::new(sstore.local_path().into())),
+			address_book: RwLock::new(AddressBook::new(sstore.local_path().into())),
+			dapps_settings: RwLock::new(DappsSettingsStore::new(sstore.local_path().into())),
 			sstore: sstore,
 		}
 	}
@@ -185,7 +121,8 @@ impl AccountProvider {
 	pub fn transient_provider() -> Self {
 		AccountProvider {
 			unlocked: Mutex::new(HashMap::new()),
-			address_book: Mutex::new(AddressBook::transient()),
+			address_book: RwLock::new(AddressBook::transient()),
+			dapps_settings: RwLock::new(DappsSettingsStore::transient()),
 			sstore: Box::new(EthStore::open(Box::new(NullDir::default()))
 				.expect("NullDir load always succeeds; qed"))
 		}
@@ -230,19 +167,31 @@ impl AccountProvider {
 		Ok(accounts)
 	}

+	/// Gets addresses visile for dapp.
+	pub fn dapps_addresses(&self, dapp: DappId) -> Result<Vec<Address>, Error> {
+		let accounts = self.dapps_settings.read().get();
+		Ok(accounts.get(&dapp).map(|settings| settings.accounts.clone()).unwrap_or_else(Vec::new))
+	}
+
+	/// Sets addresses visile for dapp.
+	pub fn set_dapps_addresses(&self, dapp: DappId, addresses: Vec<Address>) -> Result<(), Error> {
+		self.dapps_settings.write().set_accounts(dapp, addresses);
+		Ok(())
+	}
+
 	/// Returns each address along with metadata.
 	pub fn addresses_info(&self) -> Result<HashMap<Address, AccountMeta>, Error> {
-		Ok(self.address_book.lock().get())
+		Ok(self.address_book.read().get())
 	}

 	/// Returns each address along with metadata.
 	pub fn set_address_name(&self, account: Address, name: String) -> Result<(), Error> {
-		Ok(self.address_book.lock().set_name(account, name))
+		Ok(self.address_book.write().set_name(account, name))
 	}

 	/// Returns each address along with metadata.
 	pub fn set_address_meta(&self, account: Address, meta: String) -> Result<(), Error> {
-		Ok(self.address_book.lock().set_meta(account, meta))
+		Ok(self.address_book.write().set_meta(account, meta))
 	}

 	/// Returns each account along with name and meta.
@@ -379,23 +328,9 @@ impl AccountProvider {

 #[cfg(test)]
 mod tests {
-	use super::{AccountProvider, AddressBook, Unlock};
-	use std::collections::HashMap;
+	use super::{AccountProvider, Unlock};
 	use std::time::Instant;
-	use ethjson::misc::AccountMeta;
 	use ethstore::ethkey::{Generator, Random};
-	use devtools::RandomTempPath;
-
-	#[test]
-	fn should_save_and_reload_address_book() {
-		let temp = RandomTempPath::create_dir();
-		let path = temp.as_str().to_owned();
-		let mut b = AddressBook::new(path.clone());
-		b.set_name(1.into(), "One".to_owned());
-		b.set_meta(1.into(), "{1:1}".to_owned());
-		let b = AddressBook::new(path);
-		assert_eq!(b.get(), hash_map![1.into() => AccountMeta{name: "One".to_owned(), meta: "{1:1}".to_owned(), uuid: None}]);
-	}

 	#[test]
 	fn unlock_account_temp() {
@@ -433,4 +368,17 @@ mod tests {
 		ap.unlocked.lock().get_mut(&kp.address()).unwrap().unlock = Unlock::Timed(Instant::now());
 		assert!(ap.sign(kp.address(), None, Default::default()).is_err());
 	}
+
+	#[test]
+	fn should_set_dapps_addresses() {
+		// given
+		let ap = AccountProvider::transient_provider();
+		let app = "app1".to_owned();
+
+		// when
+		ap.set_dapps_addresses(app.clone(), vec![1.into(), 2.into()]).unwrap();
+
+		// then
+		assert_eq!(ap.dapps_addresses(app.clone()).unwrap(), vec![1.into(), 2.into()]);
+	}
 }
--- a/ethcore/src/account_provider/stores.rs
+++ b/ethcore/src/account_provider/stores.rs
@@ -0,0 +1,247 @@
+// Copyright 2015, 2016 Ethcore (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/>.
+
+//! Address Book and Dapps Settings Store
+
+use std::{fs, fmt, hash, ops};
+use std::collections::HashMap;
+use std::path::PathBuf;
+
+use ethstore::ethkey::Address;
+use ethjson::misc::{AccountMeta, DappsSettings as JsonSettings};
+use account_provider::DappId;
+
+/// Disk-backed map from Address to String. Uses JSON.
+pub struct AddressBook {
+	cache: DiskMap<Address, AccountMeta>,
+}
+
+impl AddressBook {
+	/// Creates new address book at given directory.
+	pub fn new(path: String) -> Self {
+		let mut r = AddressBook {
+			cache: DiskMap::new(path, "address_book.json".into())
+		};
+		r.cache.revert(AccountMeta::read_address_map);
+		r
+	}
+
+	/// Creates transient address book (no changes are saved to disk).
+	pub fn transient() -> Self {
+		AddressBook {
+			cache: DiskMap::transient()
+		}
+	}
+
+	/// Get the address book.
+	pub fn get(&self) -> HashMap<Address, AccountMeta> {
+		self.cache.clone()
+	}
+
+	fn save(&self) {
+		self.cache.save(AccountMeta::write_address_map)
+	}
+
+	/// Sets new name for given address.
+	pub fn set_name(&mut self, a: Address, name: String) {
+		{
+			let mut x = self.cache.entry(a)
+				.or_insert_with(|| AccountMeta {name: Default::default(), meta: "{}".to_owned(), uuid: None});
+			x.name = name;
+		}
+		self.save();
+	}
+
+	/// Sets new meta for given address.
+	pub fn set_meta(&mut self, a: Address, meta: String) {
+		{
+			let mut x = self.cache.entry(a)
+				.or_insert_with(|| AccountMeta {name: "Anonymous".to_owned(), meta: Default::default(), uuid: None});
+			x.meta = meta;
+		}
+		self.save();
+	}
+}
+
+/// Dapps user settings
+#[derive(Debug, Default, Clone, Eq, PartialEq)]
+pub struct DappsSettings {
+	/// A list of visible accounts
+	pub accounts: Vec<Address>,
+}
+
+impl From<JsonSettings> for DappsSettings {
+	fn from(s: JsonSettings) -> Self {
+		DappsSettings {
+			accounts: s.accounts.into_iter().map(Into::into).collect(),
+		}
+	}
+}
+
+impl From<DappsSettings> for JsonSettings {
+	fn from(s: DappsSettings) -> Self {
+		JsonSettings {
+			accounts: s.accounts.into_iter().map(Into::into).collect(),
+		}
+	}
+}
+
+/// Disk-backed map from DappId to Settings. Uses JSON.
+pub struct DappsSettingsStore {
+	cache: DiskMap<DappId, DappsSettings>,
+}
+
+impl DappsSettingsStore {
+	/// Creates new store at given directory path.
+	pub fn new(path: String) -> Self {
+		let mut r = DappsSettingsStore {
+			cache: DiskMap::new(path, "dapps_accounts.json".into())
+		};
+		r.cache.revert(JsonSettings::read_dapps_settings);
+		r
+	}
+
+	/// Creates transient store (no changes are saved to disk).
+	pub fn transient() -> Self {
+		DappsSettingsStore {
+			cache: DiskMap::transient()
+		}
+	}
+
+	/// Get copy of the dapps settings
+	pub fn get(&self) -> HashMap<DappId, DappsSettings> {
+		self.cache.clone()
+	}
+
+	fn save(&self) {
+		self.cache.save(JsonSettings::write_dapps_settings)
+	}
+
+	pub fn set_accounts(&mut self, id: DappId, accounts: Vec<Address>) {
+		{
+			let mut settings = self.cache.entry(id).or_insert_with(DappsSettings::default);
+			settings.accounts = accounts;
+		}
+		self.save();
+	}
+}
+
+/// Disk-serializable HashMap
+#[derive(Debug)]
+struct DiskMap<K: hash::Hash + Eq, V> {
+	path: PathBuf,
+	cache: HashMap<K, V>,
+	transient: bool,
+}
+
+impl<K: hash::Hash + Eq, V> ops::Deref for DiskMap<K, V> {
+	type Target = HashMap<K, V>;
+	fn deref(&self) -> &Self::Target {
+		&self.cache
+	}
+}
+
+impl<K: hash::Hash + Eq, V> ops::DerefMut for DiskMap<K, V> {
+	fn deref_mut(&mut self) -> &mut Self::Target {
+		&mut self.cache
+	}
+}
+
+impl<K: hash::Hash + Eq, V> DiskMap<K, V> {
+	pub fn new(path: String, file_name: String) -> Self {
+		trace!(target: "diskmap", "new({})", path);
+		let mut path: PathBuf = path.into();
+		path.push(file_name);
+		trace!(target: "diskmap", "path={:?}", path);
+		DiskMap {
+			path: path,
+			cache: HashMap::new(),
+			transient: false,
+		}
+	}
+
+	pub fn transient() -> Self {
+		let mut map = DiskMap::new(Default::default(), "diskmap.json".into());
+		map.transient = true;
+		map
+	}
+
+	fn revert<F, E>(&mut self, read: F) where
+		F: Fn(fs::File) -> Result<HashMap<K, V>, E>,
+		E: fmt::Display,
+	{
+		if self.transient { return; }
+		trace!(target: "diskmap", "revert {:?}", self.path);
+		let _ = fs::File::open(self.path.clone())
+			.map_err(|e| trace!(target: "diskmap", "Couldn't open disk map: {}", e))
+			.and_then(|f| read(f).map_err(|e| warn!(target: "diskmap", "Couldn't read disk map: {}", e)))
+			.and_then(|m| {
+				self.cache = m;
+				Ok(())
+			});
+	}
+
+	fn save<F, E>(&self, write: F) where
+		F: Fn(&HashMap<K, V>, &mut fs::File) -> Result<(), E>,
+		E: fmt::Display,
+	{
+		if self.transient { return; }
+		trace!(target: "diskmap", "save {:?}", self.path);
+		let _ = fs::File::create(self.path.clone())
+			.map_err(|e| warn!(target: "diskmap", "Couldn't open disk map for writing: {}", e))
+			.and_then(|mut f| {
+				write(&self.cache, &mut f).map_err(|e| warn!(target: "diskmap", "Couldn't write to disk map: {}", e))
+			});
+	}
+}
+
+#[cfg(test)]
+mod tests {
+	use super::{AddressBook, DappsSettingsStore, DappsSettings};
+	use std::collections::HashMap;
+	use ethjson::misc::AccountMeta;
+	use devtools::RandomTempPath;
+
+	#[test]
+	fn should_save_and_reload_address_book() {
+		let temp = RandomTempPath::create_dir();
+		let path = temp.as_str().to_owned();
+		let mut b = AddressBook::new(path.clone());
+		b.set_name(1.into(), "One".to_owned());
+		b.set_meta(1.into(), "{1:1}".to_owned());
+		let b = AddressBook::new(path);
+		assert_eq!(b.get(), hash_map![1.into() => AccountMeta{name: "One".to_owned(), meta: "{1:1}".to_owned(), uuid: None}]);
+	}
+
+	#[test]
+	fn should_save_and_reload_dapps_settings() {
+		// given
+		let temp = RandomTempPath::create_dir();
+		let path = temp.as_str().to_owned();
+		let mut b = DappsSettingsStore::new(path.clone());
+
+		// when
+		b.set_accounts("dappOne".into(), vec![1.into(), 2.into()]);
+
+		// then
+		let b = DappsSettingsStore::new(path);
+		assert_eq!(b.get(), hash_map![
+			"dappOne".into() => DappsSettings {
+				accounts: vec![1.into(), 2.into()],
+			}
+		]);
+	}
+}
--- a/ethcore/src/blockchain/blockchain.rs
+++ b/ethcore/src/blockchain/blockchain.rs
@@ -34,6 +34,7 @@ use blockchain::update::ExtrasUpdate;
 use blockchain::{CacheSize, ImportRoute, Config};
 use db::{self, Writable, Readable, CacheUpdatePolicy};
 use cache_manager::CacheManager;
+use engines::Engine;

 const LOG_BLOOMS_LEVELS: usize = 3;
 const LOG_BLOOMS_ELEMENTS_PER_INDEX: usize = 16;
@@ -198,6 +199,9 @@ pub struct BlockChain {
 	pending_block_hashes: RwLock<HashMap<BlockNumber, H256>>,
 	pending_block_details: RwLock<HashMap<H256, BlockDetails>>,
 	pending_transaction_addresses: RwLock<HashMap<H256, Option<TransactionAddress>>>,
+
+	// Used for block ordering.
+	engine: Arc<Engine>,
 }

 impl BlockProvider for BlockChain {
@@ -415,9 +419,8 @@ impl<'a> Iterator for AncestryIter<'a> {
 }

 impl BlockChain {
-	#[cfg_attr(feature="dev", allow(useless_let_if_seq))]
-	/// Create new instance of blockchain from given Genesis
-	pub fn new(config: Config, genesis: &[u8], db: Arc<Database>) -> BlockChain {
+	/// Create new instance of blockchain from given Genesis and block picking rules of Engine.
+	pub fn new(config: Config, genesis: &[u8], db: Arc<Database>, engine: Arc<Engine>) -> BlockChain {
 		// 400 is the avarage size of the key
 		let cache_man = CacheManager::new(config.pref_cache_size, config.max_cache_size, 400);

@@ -442,6 +445,7 @@ impl BlockChain {
 			pending_block_hashes: RwLock::new(HashMap::new()),
 			pending_block_details: RwLock::new(HashMap::new()),
 			pending_transaction_addresses: RwLock::new(HashMap::new()),
+			engine: engine,
 		};

 		// load best block
@@ -858,13 +862,12 @@ impl BlockChain {
 		let number = header.number();
 		let parent_hash = header.parent_hash();
 		let parent_details = self.block_details(&parent_hash).unwrap_or_else(|| panic!("Invalid parent hash: {:?}", parent_hash));
-		let total_difficulty = parent_details.total_difficulty + header.difficulty();
-		let is_new_best = total_difficulty > self.best_block_total_difficulty();
+		let is_new_best = self.engine.is_new_best_block(self.best_block_total_difficulty(), HeaderView::new(&self.best_block_header()), &parent_details, header);

 		BlockInfo {
 			hash: hash,
 			number: number,
-			total_difficulty: total_difficulty,
+			total_difficulty: parent_details.total_difficulty + header.difficulty(),
 			location: if is_new_best {
 				// on new best block we need to make sure that all ancestors
 				// are moved to "canon chain"
@@ -1319,11 +1322,16 @@ mod tests {
 	use views::BlockView;
 	use transaction::{Transaction, Action};
 	use log_entry::{LogEntry, LocalizedLogEntry};
+	use spec::Spec;

 	fn new_db(path: &str) -> Arc<Database> {
 		Arc::new(Database::open(&DatabaseConfig::with_columns(::db::NUM_COLUMNS), path).unwrap())
 	}

+	fn new_chain(genesis: &[u8], db: Arc<Database>) -> BlockChain {
+		BlockChain::new(Config::default(), genesis, db, Spec::new_null().engine) 
+	}
+
 	#[test]
 	fn should_cache_best_block() {
 		// given
@@ -1334,7 +1342,7 @@ mod tests {

 		let temp = RandomTempPath::new();
 		let db = new_db(temp.as_str());
-		let bc = BlockChain::new(Config::default(), &genesis, db.clone());
+		let bc = new_chain(&genesis, db.clone());
 		assert_eq!(bc.best_block_number(), 0);

 		// when
@@ -1360,7 +1368,7 @@ mod tests {

 		let temp = RandomTempPath::new();
 		let db = new_db(temp.as_str());
-		let bc = BlockChain::new(Config::default(), &genesis, db.clone());
+		let bc = new_chain(&genesis, db.clone());

 		assert_eq!(bc.genesis_hash(), genesis_hash.clone());
 		assert_eq!(bc.best_block_hash(), genesis_hash.clone());
@@ -1391,7 +1399,7 @@ mod tests {

 		let temp = RandomTempPath::new();
 		let db = new_db(temp.as_str());
-		let bc = BlockChain::new(Config::default(), &genesis, db.clone());
+		let bc = new_chain(&genesis, db.clone());

 		let mut block_hashes = vec![genesis_hash.clone()];
 		let mut batch = db.transaction();
@@ -1427,7 +1435,7 @@ mod tests {

 		let temp = RandomTempPath::new();
 		let db = new_db(temp.as_str());
-		let bc = BlockChain::new(Config::default(), &genesis, db.clone());
+		let bc = new_chain(&genesis, db.clone());

 		let mut batch =db.transaction();
 		for b in &[&b1a, &b1b, &b2a, &b2b, &b3a, &b3b, &b4a, &b4b, &b5a, &b5b] {
@@ -1489,7 +1497,7 @@ mod tests {

 		let temp = RandomTempPath::new();
 		let db = new_db(temp.as_str());
-		let bc = BlockChain::new(Config::default(), &genesis, db.clone());
+		let bc = new_chain(&genesis, db.clone());

 		let mut batch = db.transaction();
 		let _ = bc.insert_block(&mut batch, &b1a, vec![]);
@@ -1577,7 +1585,7 @@ mod tests {

 		let temp = RandomTempPath::new();
 		let db = new_db(temp.as_str());
-		let bc = BlockChain::new(Config::default(), &genesis, db.clone());
+		let bc = new_chain(&genesis, db.clone());

 		let mut batch = db.transaction();
 		let _ = bc.insert_block(&mut batch, &b1a, vec![]);
@@ -1639,7 +1647,7 @@ mod tests {

 		let temp = RandomTempPath::new();
 		let db = new_db(temp.as_str());
-		let bc = BlockChain::new(Config::default(), &genesis, db.clone());
+		let bc = new_chain(&genesis, db.clone());

 		let mut batch = db.transaction();
 		let ir1 = bc.insert_block(&mut batch, &b1, vec![]);
@@ -1755,7 +1763,7 @@ mod tests {
 		let temp = RandomTempPath::new();
 		{
 			let db = new_db(temp.as_str());
-			let bc = BlockChain::new(Config::default(), &genesis, db.clone());
+			let bc = new_chain(&genesis, db.clone());
 			assert_eq!(bc.best_block_hash(), genesis_hash);
 			let mut batch =db.transaction();
 			bc.insert_block(&mut batch, &first, vec![]);
@@ -1766,7 +1774,7 @@ mod tests {

 		{
 			let db = new_db(temp.as_str());
-			let bc = BlockChain::new(Config::default(), &genesis, db.clone());
+			let bc = new_chain(&genesis, db.clone());

 			assert_eq!(bc.best_block_hash(), first_hash);
 		}
@@ -1821,7 +1829,7 @@ mod tests {

 		let temp = RandomTempPath::new();
 		let db = new_db(temp.as_str());
-		let bc = BlockChain::new(Config::default(), &genesis, db.clone());
+		let bc = new_chain(&genesis, db.clone());
 		let mut batch =db.transaction();
 		bc.insert_block(&mut batch, &b1, vec![]);
 		db.write(batch).unwrap();
@@ -1881,7 +1889,7 @@ mod tests {

 		let temp = RandomTempPath::new();
 		let db = new_db(temp.as_str());
-		let bc = BlockChain::new(Config::default(), &genesis, db.clone());
+		let bc = new_chain(&genesis, db.clone());
 		insert_block(&db, &bc, &b1, vec![Receipt {
 			state_root: H256::default(),
 			gas_used: 10_000.into(),
@@ -1985,7 +1993,7 @@ mod tests {

 		let temp = RandomTempPath::new();
 		let db = new_db(temp.as_str());
-		let bc = BlockChain::new(Config::default(), &genesis, db.clone());
+		let bc = new_chain(&genesis, db.clone());

 		let blocks_b1 = bc.blocks_with_bloom(&bloom_b1, 0, 5);
 		let blocks_b2 = bc.blocks_with_bloom(&bloom_b2, 0, 5);
@@ -2042,7 +2050,7 @@ mod tests {

 		{
 			let db = new_db(temp.as_str());
-			let bc = BlockChain::new(Config::default(), &genesis, db.clone());
+			let bc = new_chain(&genesis, db.clone());
 			let uncle = canon_chain.fork(1).generate(&mut finalizer.fork()).unwrap();

 			let mut batch =db.transaction();
@@ -2061,7 +2069,7 @@ mod tests {

 		// re-loading the blockchain should load the correct best block.
 		let db = new_db(temp.as_str());
-		let bc = BlockChain::new(Config::default(), &genesis, db.clone());
+		let bc = new_chain(&genesis, db.clone());
 		assert_eq!(bc.best_block_number(), 5);
 	}

@@ -2078,7 +2086,7 @@ mod tests {

 		let temp = RandomTempPath::new();
 		let db = new_db(temp.as_str());
-		let bc = BlockChain::new(Config::default(), &genesis, db.clone());
+		let bc = new_chain(&genesis, db.clone());

 		let mut batch =db.transaction();
 		bc.insert_block(&mut batch, &first, vec![]);
--- a/ethcore/src/client/client.rs
+++ b/ethcore/src/client/client.rs
@@ -164,7 +164,7 @@ impl Client {
 		let gb = spec.genesis_block();

 		let db = Arc::new(try!(Database::open(&db_config, &path.to_str().expect("DB path could not be converted to string.")).map_err(ClientError::Database)));
-		let chain = Arc::new(BlockChain::new(config.blockchain.clone(), &gb, db.clone()));
+		let chain = Arc::new(BlockChain::new(config.blockchain.clone(), &gb, db.clone(), spec.engine.clone()));
 		let tracedb = RwLock::new(TraceDB::new(config.tracing.clone(), db.clone(), chain.clone()));

 		let trie_spec = match config.fat_db {
@@ -787,7 +787,7 @@ impl snapshot::DatabaseRestore for Client {

 		let cache_size = state_db.cache_size();
 		*state_db = StateDB::new(journaldb::new(db.clone(), self.pruning, ::db::COL_STATE), cache_size);
-		*chain = Arc::new(BlockChain::new(self.config.blockchain.clone(), &[], db.clone()));
+		*chain = Arc::new(BlockChain::new(self.config.blockchain.clone(), &[], db.clone(), self.engine.clone()));
 		*tracedb = TraceDB::new(self.config.tracing.clone(), db.clone(), chain.clone());
 		Ok(())
 	}
@@ -1272,7 +1272,7 @@ impl BlockChainClient for Client {
 		self.miner.pending_transactions(self.chain.read().best_block_number())
 	}

-	fn signing_network_id(&self) -> Option<u8> {
+	fn signing_network_id(&self) -> Option<u64> {
 		self.engine.signing_network_id(&self.latest_env_info())
 	}

--- a/ethcore/src/client/test_client.rs
+++ b/ethcore/src/client/test_client.rs
@@ -662,7 +662,7 @@ impl BlockChainClient for TestBlockChainClient {
 		self.miner.pending_transactions(self.chain_info().best_block_number)
 	}

-	fn signing_network_id(&self) -> Option<u8> { None }
+	fn signing_network_id(&self) -> Option<u64> { None }

 	fn mode(&self) -> Mode { Mode::Active }

--- a/ethcore/src/client/traits.rs
+++ b/ethcore/src/client/traits.rs
@@ -237,7 +237,7 @@ pub trait BlockChainClient : Sync + Send {
 	}

 	/// Get the preferred network ID to sign on
-	fn signing_network_id(&self) -> Option<u8>;
+	fn signing_network_id(&self) -> Option<u64>;

 	/// Get the mode.
 	fn mode(&self) -> Mode;
--- a/ethcore/src/engines/authority_round.rs
+++ b/ethcore/src/engines/authority_round.rs
@@ -21,7 +21,7 @@ use std::sync::Weak;
 use std::time::{UNIX_EPOCH, Duration};
 use util::*;
 use ethkey::{verify_address, Signature};
-use rlp::{UntrustedRlp, View, encode};
+use rlp::{Rlp, UntrustedRlp, View, encode};
 use account_provider::AccountProvider;
 use block::*;
 use spec::CommonParams;
@@ -35,6 +35,8 @@ use service::ClientIoMessage;
 use transaction::SignedTransaction;
 use env_info::EnvInfo;
 use builtin::Builtin;
+use blockchain::extras::BlockDetails;
+use views::HeaderView;

 /// `AuthorityRound` params.
 #[derive(Debug, PartialEq)]
@@ -272,7 +274,6 @@ impl Engine for AuthorityRound {
 	}

 	fn verify_block_family(&self, header: &Header, parent: &Header, _block: Option<&[u8]>) -> Result<(), Error> {
-		// Don't calculate difficulty for genesis blocks.
 		if header.number() == 0 {
 			return Err(From::from(BlockError::RidiculousNumber(OutOfBounds { min: Some(1), max: None, found: header.number() })));
 		}
@@ -284,10 +285,6 @@ impl Engine for AuthorityRound {
 			try!(Err(BlockError::DoubleVote(header.author().clone())));
 		}

-		// Check difficulty is correct given the two timestamps.
-		if header.difficulty() != parent.difficulty() {
-			return Err(From::from(BlockError::InvalidDifficulty(Mismatch { expected: *parent.difficulty(), found: *header.difficulty() })))
-		}
 		let gas_limit_divisor = self.our_params.gas_limit_bound_divisor;
 		let min_gas = parent.gas_limit().clone() - parent.gas_limit().clone() / gas_limit_divisor;
 		let max_gas = parent.gas_limit().clone() + parent.gas_limit().clone() / gas_limit_divisor;
@@ -310,6 +307,19 @@ impl Engine for AuthorityRound {
 		let mut guard = self.message_channel.lock();
 		*guard = Some(message_channel);
 	}
+
+	fn is_new_best_block(&self, _best_total_difficulty: U256, best_header: HeaderView, _parent_details: &BlockDetails, new_header: &HeaderView) -> bool {
+		let new_number = new_header.number();
+		let best_number = best_header.number();
+		if new_number != best_number {
+			new_number > best_number
+		} else {
+			// Take the oldest step at given height.
+			let new_step: usize = Rlp::new(&new_header.seal()[0]).as_val();
+			let best_step: usize = Rlp::new(&best_header.seal()[0]).as_val();
+			new_step < best_step
+		}
+	}
 }

 #[cfg(test)]
--- a/ethcore/src/engines/mod.rs
+++ b/ethcore/src/engines/mod.rs
@@ -38,6 +38,9 @@ use io::IoChannel;
 use service::ClientIoMessage;
 use header::Header;
 use transaction::SignedTransaction;
+use ethereum::ethash;
+use blockchain::extras::BlockDetails;
+use views::HeaderView;

 /// A consensus mechanism for the chain. Generally either proof-of-work or proof-of-stake-based.
 /// Provides hooks into each of the major parts of block import.
@@ -113,7 +116,7 @@ pub trait Engine : Sync + Send {
 	fn verify_transaction(&self, _t: &SignedTransaction, _header: &Header) -> Result<(), Error> { Ok(()) }

 	/// The network ID that transactions should be signed with.
-	fn signing_network_id(&self, _env_info: &EnvInfo) -> Option<u8> { None }
+	fn signing_network_id(&self, _env_info: &EnvInfo) -> Option<u64> { None }

 	/// Verify the seal of a block. This is an auxilliary method that actually just calls other `verify_` methods
 	/// to get the job done. By default it must pass `verify_basic` and `verify_block_unordered`. If more or fewer
@@ -146,5 +149,9 @@ pub trait Engine : Sync + Send {

 	/// Add a channel for communication with Client which can be used for sealing.
 	fn register_message_channel(&self, _message_channel: IoChannel<ClientIoMessage>) {}
-	// TODO: sealing stuff - though might want to leave this for later.
+
+	/// Check if new block should be chosen as the one  in chain.
+	fn is_new_best_block(&self, best_total_difficulty: U256, _best_header: HeaderView, parent_details: &BlockDetails, new_header: &HeaderView) -> bool {
+		ethash::is_new_best_block(best_total_difficulty, parent_details, new_header)
+	}
 }
--- a/ethcore/src/engines/null_engine.rs
+++ b/ethcore/src/engines/null_engine.rs
@@ -38,6 +38,12 @@ impl NullEngine {
 	}
 }

+impl Default for NullEngine {
+	fn default() -> Self {
+		Self::new(Default::default(), Default::default())
+	}
+}
+
 impl Engine for NullEngine {
 	fn name(&self) -> &str {
 		"NullEngine"
--- a/ethcore/src/ethereum/ethash.rs
+++ b/ethcore/src/ethereum/ethash.rs
@@ -21,6 +21,7 @@ use builtin::Builtin;
 use env_info::EnvInfo;
 use error::{BlockError, TransactionError, Error};
 use header::Header;
+use views::HeaderView;
 use state::CleanupMode;
 use spec::CommonParams;
 use transaction::SignedTransaction;
@@ -28,6 +29,7 @@ use engines::Engine;
 use evm::Schedule;
 use ethjson;
 use rlp::{self, UntrustedRlp, View};
+use blockchain::extras::BlockDetails;

 /// Ethash params.
 #[derive(Debug, PartialEq)]
@@ -163,9 +165,9 @@ impl Engine for Ethash {
 		}
 	}

-	fn signing_network_id(&self, env_info: &EnvInfo) -> Option<u8> {
-		if env_info.number >= self.ethash_params.eip155_transition && self.params().network_id < 127 {
-			Some(self.params().network_id as u8)
+	fn signing_network_id(&self, env_info: &EnvInfo) -> Option<u64> {
+		if env_info.number >= self.ethash_params.eip155_transition {
+			Some(self.params().network_id)
 		} else {
 			None
 		}
@@ -314,7 +316,7 @@ impl Engine for Ethash {
 		}

 		if let Some(n) = t.network_id() {
-			if header.number() < self.ethash_params.eip155_transition || n as usize != self.params().network_id {
+			if header.number() < self.ethash_params.eip155_transition || n != self.params().network_id {
 				return Err(TransactionError::InvalidNetworkId.into())
 			}
 		}
@@ -325,6 +327,15 @@ impl Engine for Ethash {
 	fn verify_transaction(&self, t: &SignedTransaction, _header: &Header) -> Result<(), Error> {
 		t.sender().map(|_|()) // Perform EC recovery and cache sender
 	}
+
+	fn is_new_best_block(&self, best_total_difficulty: U256, _best_header: HeaderView, parent_details: &BlockDetails, new_header: &HeaderView) -> bool {
+		is_new_best_block(best_total_difficulty, parent_details, new_header)
+	}
+}
+
+/// Check if a new block should replace the best blockchain block.
+pub fn is_new_best_block(best_total_difficulty: U256, parent_details: &BlockDetails, new_header: &HeaderView) -> bool {
+	parent_details.total_difficulty + new_header.difficulty() > best_total_difficulty
 }

 #[cfg_attr(feature="dev", allow(wrong_self_convention))]
--- a/ethcore/src/snapshot/service.rs
+++ b/ethcore/src/snapshot/service.rs
@@ -81,6 +81,7 @@ struct Restoration {
 struct RestorationParams<'a> {
 	manifest: ManifestData, // manifest to base restoration on.
 	pruning: Algorithm, // pruning algorithm for the database.
+	engine: Arc<Engine>, // consensus engine of the chain.
 	db_path: PathBuf, // database path
 	db_config: &'a DatabaseConfig, // configuration for the database.
 	writer: Option<LooseWriter>, // writer for recovered snapshot.
@@ -99,7 +100,7 @@ impl Restoration {
 		let raw_db = Arc::new(try!(Database::open(params.db_config, &*params.db_path.to_string_lossy())
 			.map_err(UtilError::SimpleString)));

-		let chain = BlockChain::new(Default::default(), params.genesis, raw_db.clone());
+		let chain = BlockChain::new(Default::default(), params.genesis, raw_db.clone(), params.engine);
 		let blocks = try!(BlockRebuilder::new(chain, raw_db.clone(), &manifest));

 		let root = manifest.state_root.clone();
@@ -420,6 +421,7 @@ impl Service {
 		let params = RestorationParams {
 			manifest: manifest,
 			pruning: self.pruning,
+			engine: self.engine.clone(),
 			db_path: self.restoration_db(),
 			db_config: &self.db_config,
 			writer: writer,
--- a/ethcore/src/snapshot/tests/blocks.rs
+++ b/ethcore/src/snapshot/tests/blocks.rs
@@ -37,13 +37,14 @@ fn chunk_and_restore(amount: u64) {
 	let genesis = canon_chain.generate(&mut finalizer).unwrap();
 	let db_cfg = DatabaseConfig::with_columns(::db::NUM_COLUMNS);

+	let engine = Arc::new(::engines::NullEngine::default());
 	let orig_path = RandomTempPath::create_dir();
 	let new_path = RandomTempPath::create_dir();
 	let mut snapshot_path = new_path.as_path().to_owned();
 	snapshot_path.push("SNAP");

 	let old_db = Arc::new(Database::open(&db_cfg, orig_path.as_str()).unwrap());
-	let bc = BlockChain::new(Default::default(), &genesis, old_db.clone());
+	let bc = BlockChain::new(Default::default(), &genesis, old_db.clone(), engine.clone());

 	// build the blockchain.
 	let mut batch = old_db.transaction();
@@ -73,21 +74,20 @@ fn chunk_and_restore(amount: u64) {

 	// restore it.
 	let new_db = Arc::new(Database::open(&db_cfg, new_path.as_str()).unwrap());
-	let new_chain = BlockChain::new(Default::default(), &genesis, new_db.clone());
+	let new_chain = BlockChain::new(Default::default(), &genesis, new_db.clone(), engine.clone());
 	let mut rebuilder = BlockRebuilder::new(new_chain, new_db.clone(), &manifest).unwrap();
 	let reader = PackedReader::new(&snapshot_path).unwrap().unwrap();
-	let engine = ::engines::NullEngine::new(Default::default(), Default::default());
 	let flag = AtomicBool::new(true);
 	for chunk_hash in &reader.manifest().block_hashes {
 		let compressed = reader.chunk(*chunk_hash).unwrap();
 		let chunk = snappy::decompress(&compressed).unwrap();
-		rebuilder.feed(&chunk, &engine, &flag).unwrap();
+		rebuilder.feed(&chunk, engine.as_ref(), &flag).unwrap();
 	}

 	rebuilder.finalize(HashMap::new()).unwrap();

 	// and test it.
-	let new_chain = BlockChain::new(Default::default(), &genesis, new_db);
+	let new_chain = BlockChain::new(Default::default(), &genesis, new_db, engine);
 	assert_eq!(new_chain.best_block_hash(), best_hash);
 }

@@ -121,8 +121,8 @@ fn checks_flag() {

 	let db_cfg = DatabaseConfig::with_columns(::db::NUM_COLUMNS);
 	let db = Arc::new(Database::open(&db_cfg, path.as_str()).unwrap());
-	let chain = BlockChain::new(Default::default(), &genesis, db.clone());
-	let engine = ::engines::NullEngine::new(Default::default(), Default::default());
+	let engine = Arc::new(::engines::NullEngine::default());
+	let chain = BlockChain::new(Default::default(), &genesis, db.clone(), engine.clone());

 	let manifest = ::snapshot::ManifestData {
 		state_hashes: Vec::new(),
@@ -134,8 +134,8 @@ fn checks_flag() {

 	let mut rebuilder = BlockRebuilder::new(chain, db.clone(), &manifest).unwrap();

-	match rebuilder.feed(&chunk, &engine, &AtomicBool::new(false)) {
+	match rebuilder.feed(&chunk, engine.as_ref(), &AtomicBool::new(false)) {
 		Err(Error::Snapshot(SnapshotError::RestorationAborted)) => {}
 		_ => panic!("Wrong result on abort flag set")
 	}
-}
+}
--- a/ethcore/src/spec/seal.rs
+++ b/ethcore/src/spec/seal.rs
@@ -30,11 +30,9 @@ pub struct Ethereum {

 impl Into<Generic> for Ethereum {
 	fn into(self) -> Generic {
-		let mut s = RlpStream::new();
-		s.append(&self.mix_hash);
-		s.append(&self.nonce);
+		let mut s = RlpStream::new_list(2);
+		s.append(&self.mix_hash).append(&self.nonce);
 		Generic {
-			fields: 2,
 			rlp: s.out()
 		}
 	}
@@ -42,8 +40,6 @@ impl Into<Generic> for Ethereum {

 /// Generic seal.
 pub struct Generic {
-	/// Number of seal fields.
-	pub fields: usize,
 	/// Seal rlp.
 	pub rlp: Vec<u8>,
 }
@@ -64,7 +60,6 @@ impl From<ethjson::spec::Seal> for Seal {
 				mix_hash: eth.mix_hash.into()
 			}),
 			ethjson::spec::Seal::Generic(g) => Seal::Generic(Generic {
-				fields: g.fields,
 				rlp: g.rlp.into()
 			})
 		}
--- a/ethcore/src/spec/spec.rs
+++ b/ethcore/src/spec/spec.rs
@@ -30,15 +30,14 @@ use ethjson;
 use rlp::{Rlp, RlpStream, View, Stream};

 /// Parameters common to all engines.
-#[derive(Debug, PartialEq, Clone)]
-#[cfg_attr(test, derive(Default))]
+#[derive(Debug, PartialEq, Clone, Default)]
 pub struct CommonParams {
 	/// Account start nonce.
 	pub account_start_nonce: U256,
 	/// Maximum size of extra data.
 	pub maximum_extra_data_size: usize,
 	/// Network id.
-	pub network_id: usize,
+	pub network_id: u64,
 	/// Main subprotocol name.
 	pub subprotocol_name: String,
 	/// Minimum gas limit.
@@ -94,8 +93,6 @@ pub struct Spec {
 	pub receipts_root: H256,
 	/// The genesis block's extra data field.
 	pub extra_data: Bytes,
-	/// The number of seal fields in the genesis block.
-	pub seal_fields: usize,
 	/// Each seal field, expressed as RLP, concatenated.
 	pub seal_rlp: Bytes,

@@ -127,7 +124,6 @@ impl From<ethjson::spec::Spec> for Spec {
 			gas_used: g.gas_used,
 			timestamp: g.timestamp,
 			extra_data: g.extra_data,
-			seal_fields: seal.fields,
 			seal_rlp: seal.rlp,
 			state_root_memo: RwLock::new(g.state_root),
 			genesis_state: From::from(s.accounts),
@@ -167,7 +163,7 @@ impl Spec {
 	pub fn nodes(&self) -> &[String] { &self.nodes }

 	/// Get the configured Network ID.
-	pub fn network_id(&self) -> usize { self.params.network_id }
+	pub fn network_id(&self) -> u64 { self.params.network_id }

 	/// Get the configured subprotocol name.
 	pub fn subprotocol_name(&self) -> String { self.params.subprotocol_name.clone() }
@@ -192,13 +188,8 @@ impl Spec {
 		header.set_gas_limit(self.gas_limit.clone());
 		header.set_difficulty(self.difficulty.clone());
 		header.set_seal({
-			let seal = {
-				let mut s = RlpStream::new_list(self.seal_fields);
-				s.append_raw(&self.seal_rlp, self.seal_fields);
-				s.out()
-			};
-			let r = Rlp::new(&seal);
-			(0..self.seal_fields).map(|i| r.at(i).as_raw().to_vec()).collect()
+			let r = Rlp::new(&self.seal_rlp);
+			r.iter().map(|f| f.as_raw().to_vec()).collect()
 		});
 		trace!(target: "spec", "Header hash is {}", header.hash());
 		header
@@ -227,7 +218,6 @@ impl Spec {
 		self.gas_used = g.gas_used;
 		self.timestamp = g.timestamp;
 		self.extra_data = g.extra_data;
-		self.seal_fields = seal.fields;
 		self.seal_rlp = seal.rlp;
 		self.state_root_memo = RwLock::new(g.state_root);
 	}
--- a/ethcore/src/state/mod.rs
+++ b/ethcore/src/state/mod.rs
--- a/ethcore/src/tests/helpers.rs
+++ b/ethcore/src/tests/helpers.rs
@@ -286,7 +286,7 @@ fn new_db(path: &str) -> Arc<Database> {
 pub fn generate_dummy_blockchain(block_number: u32) -> GuardedTempResult<BlockChain> {
 	let temp = RandomTempPath::new();
 	let db = new_db(temp.as_str());
-	let bc = BlockChain::new(BlockChainConfig::default(), &create_unverifiable_block(0, H256::zero()), db.clone());
+	let bc = BlockChain::new(BlockChainConfig::default(), &create_unverifiable_block(0, H256::zero()), db.clone(), Spec::new_null().engine);

 	let mut batch = db.transaction();
 	for block_order in 1..block_number {
@@ -304,7 +304,7 @@ pub fn generate_dummy_blockchain(block_number: u32) -> GuardedTempResult<BlockCh
 pub fn generate_dummy_blockchain_with_extra(block_number: u32) -> GuardedTempResult<BlockChain> {
 	let temp = RandomTempPath::new();
 	let db = new_db(temp.as_str());
-	let bc = BlockChain::new(BlockChainConfig::default(), &create_unverifiable_block(0, H256::zero()), db.clone());
+	let bc = BlockChain::new(BlockChainConfig::default(), &create_unverifiable_block(0, H256::zero()), db.clone(), Spec::new_null().engine);


 	let mut batch = db.transaction();
@@ -323,7 +323,7 @@ pub fn generate_dummy_blockchain_with_extra(block_number: u32) -> GuardedTempRes
 pub fn generate_dummy_empty_blockchain() -> GuardedTempResult<BlockChain> {
 	let temp = RandomTempPath::new();
 	let db = new_db(temp.as_str());
-	let bc = BlockChain::new(BlockChainConfig::default(), &create_unverifiable_block(0, H256::zero()), db.clone());
+	let bc = BlockChain::new(BlockChainConfig::default(), &create_unverifiable_block(0, H256::zero()), db.clone(), Spec::new_null().engine);

 	GuardedTempResult::<BlockChain> {
 		_temp: temp,
--- a/ethcore/src/types/transaction.rs
+++ b/ethcore/src/types/transaction.rs
@@ -72,7 +72,7 @@ pub struct Transaction {

 impl Transaction {
 	/// Append object with a without signature into RLP stream
-	pub fn rlp_append_unsigned_transaction(&self, s: &mut RlpStream, network_id: Option<u8>) {
+	pub fn rlp_append_unsigned_transaction(&self, s: &mut RlpStream, network_id: Option<u64>) {
 		s.begin_list(if network_id.is_none() { 6 } else { 9 });
 		s.append(&self.nonce);
 		s.append(&self.gas_price);
@@ -140,26 +140,26 @@ impl From<ethjson::transaction::Transaction> for SignedTransaction {

 impl Transaction {
 	/// The message hash of the transaction.
-	pub fn hash(&self, network_id: Option<u8>) -> H256 {
+	pub fn hash(&self, network_id: Option<u64>) -> H256 {
 		let mut stream = RlpStream::new();
 		self.rlp_append_unsigned_transaction(&mut stream, network_id);
 		stream.out().sha3()
 	}

 	/// Signs the transaction as coming from `sender`.
-	pub fn sign(self, secret: &Secret, network_id: Option<u8>) -> SignedTransaction {
+	pub fn sign(self, secret: &Secret, network_id: Option<u64>) -> SignedTransaction {
 		let sig = ::ethkey::sign(secret, &self.hash(network_id))
 			.expect("data is valid and context has signing capabilities; qed");
 		self.with_signature(sig, network_id)
 	}

 	/// Signs the transaction with signature.
-	pub fn with_signature(self, sig: Signature, network_id: Option<u8>) -> SignedTransaction {
+	pub fn with_signature(self, sig: Signature, network_id: Option<u64>) -> SignedTransaction {
 		SignedTransaction {
 			unsigned: self,
 			r: sig.r().into(),
 			s: sig.s().into(),
-			v: sig.v() + if let Some(n) = network_id { 35 + n * 2 } else { 27 },
+			v: sig.v() as u64 + if let Some(n) = network_id { 35 + n * 2 } else { 27 },
 			hash: Cell::new(None),
 			sender: Cell::new(None),
 		}
@@ -211,7 +211,7 @@ pub struct SignedTransaction {
 	unsigned: Transaction,
 	/// The V field of the signature; the LS bit described which half of the curve our point falls
 	/// in. The MS bits describe which network this transaction is for. If 27/28, its for all networks.
-	v: u8,
+	v: u64,
 	/// The R field of the signature; helps describe the point on the curve.
 	r: U256,
 	/// The S field of the signature; helps describe the point on the curve.
@@ -302,13 +302,13 @@ impl SignedTransaction {
 	}

 	/// 0 if `v` would have been 27 under "Electrum" notation, 1 if 28 or 4 if invalid.
-	pub fn standard_v(&self) -> u8 { match self.v { v if v == 27 || v == 28 || v > 36 => (v - 1) % 2, _ => 4 } }
+	pub fn standard_v(&self) -> u8 { match self.v { v if v == 27 || v == 28 || v > 36 => ((v - 1) % 2) as u8, _ => 4 } }

 	/// The `v` value that appears in the RLP.
 	pub fn original_v(&self) -> u8 { self.v }

-	/// The network ID, or `None` if this is a global transaction. 
-	pub fn network_id(&self) -> Option<u8> {
+	/// The network ID, or `None` if this is a global transaction.
+	pub fn network_id(&self) -> Option<u64> {
 		match self.v {
 			v if v > 36 => Some((v - 35) / 2),
 			_ => None,
--- a/ethcore/src/verification/queue/mod.rs
+++ b/ethcore/src/verification/queue/mod.rs
@@ -17,7 +17,7 @@
 //! A queue of blocks. Sits between network or other I/O and the `BlockChain`.
 //! Sorts them ready for blockchain insertion.

-use std::thread::{JoinHandle, self};
+use std::thread::{self, JoinHandle};
 use std::sync::atomic::{AtomicBool, AtomicUsize, Ordering as AtomicOrdering};
 use std::sync::{Condvar as SCondvar, Mutex as SMutex};
 use util::*;
@@ -64,35 +64,11 @@ impl Default for Config {
 	}
 }

-struct VerifierHandle {
-	deleting: Arc<AtomicBool>,
-	sleep: Arc<AtomicBool>,
-	thread: JoinHandle<()>,
-}
-
-impl VerifierHandle {
-	// signal to the verifier thread that it should sleep.
-	fn sleep(&self) {
-		self.sleep.store(true, AtomicOrdering::SeqCst);
-	}
-
-	// signal to the verifier thread that it should wake up.
-	fn wake_up(&self) {
-		self.sleep.store(false, AtomicOrdering::SeqCst);
-		self.thread.thread().unpark();
-	}
-
-	// signal to the verifier thread that it should conclude its
-	// operations.
-	fn conclude(&self) {
-		self.wake_up();
-		self.deleting.store(true, AtomicOrdering::Release);
-	}
-
-	// join the verifier thread.
-	fn join(self) {
-		self.thread.join().expect("Verifier thread panicked");
-	}
+// pool states
+enum State {
+	// all threads with id < inner value are to work.
+	Work(usize),
+	Exit,
 }

 /// An item which is in the process of being verified.
@@ -131,7 +107,6 @@ pub struct VerificationQueue<K: Kind> {
 	engine: Arc<Engine>,
 	more_to_verify: Arc<SCondvar>,
 	verification: Arc<Verification<K>>,
-	verifiers: Mutex<(Vec<VerifierHandle>, usize)>,
 	deleting: Arc<AtomicBool>,
 	ready_signal: Arc<QueueSignal>,
 	empty: Arc<SCondvar>,
@@ -139,6 +114,8 @@ pub struct VerificationQueue<K: Kind> {
 	ticks_since_adjustment: AtomicUsize,
 	max_queue_size: usize,
 	max_mem_use: usize,
+	verifier_handles: Vec<JoinHandle<()>>,	
+	state: Arc<(Mutex<State>, Condvar)>,
 }

 struct QueueSignal {
@@ -224,40 +201,39 @@ impl<K: Kind> VerificationQueue<K> {

 		let max_verifiers = min(::num_cpus::get(), MAX_VERIFIERS);
 		let default_amount = max(::num_cpus::get(), 3) - 2;
-		let mut verifiers = Vec::with_capacity(max_verifiers);
+		let state = Arc::new((Mutex::new(State::Work(default_amount)), Condvar::new()));
+		let mut verifier_handles = Vec::with_capacity(max_verifiers);

 		debug!(target: "verification", "Allocating {} verifiers, {} initially active", max_verifiers, default_amount);

 		for i in 0..max_verifiers {
 			debug!(target: "verification", "Adding verification thread #{}", i);

-			let deleting = deleting.clone();
 			let panic_handler = panic_handler.clone();
 			let verification = verification.clone();
 			let engine = engine.clone();
 			let wait = more_to_verify.clone();
 			let ready = ready_signal.clone();
 			let empty = empty.clone();
+			let state = state.clone();

-			// enable only the first few verifiers.
-			let sleep = if i < default_amount {
-				Arc::new(AtomicBool::new(false))
-			} else {
-				Arc::new(AtomicBool::new(true))
-			};
-
-			verifiers.push(VerifierHandle {
-				deleting: deleting.clone(),
-				sleep: sleep.clone(),
-				thread: thread::Builder::new()
-					.name(format!("Verifier #{}", i))
-					.spawn(move || {
-						panic_handler.catch_panic(move || {
-							VerificationQueue::verify(verification, engine, wait, ready, deleting, empty, sleep)
-						}).unwrap()
-					})
-					.expect("Failed to create verifier thread.")
-			});
+			let handle = thread::Builder::new()
+				.name(format!("Verifier #{}", i))
+				.spawn(move || {
+					panic_handler.catch_panic(move || {
+						VerificationQueue::verify(
+							verification, 
+							engine, 
+							wait, 
+							ready, 
+							empty, 
+							state,
+							i,
+						)
+					}).unwrap()
+				})
+				.expect("Failed to create verifier thread.");
+			verifier_handles.push(handle);
 		}

 		VerificationQueue {
@@ -266,13 +242,14 @@ impl<K: Kind> VerificationQueue<K> {
 			ready_signal: ready_signal,
 			more_to_verify: more_to_verify,
 			verification: verification,
-			verifiers: Mutex::new((verifiers, default_amount)),
 			deleting: deleting,
 			processing: RwLock::new(HashSet::new()),
 			empty: empty,
 			ticks_since_adjustment: AtomicUsize::new(0),
 			max_queue_size: max(config.max_queue_size, MIN_QUEUE_LIMIT),
 			max_mem_use: max(config.max_mem_use, MIN_MEM_LIMIT),
+			verifier_handles: verifier_handles,
+			state: state,
 		}
 	}

@@ -281,23 +258,30 @@ impl<K: Kind> VerificationQueue<K> {
 		engine: Arc<Engine>,
 		wait: Arc<SCondvar>,
 		ready: Arc<QueueSignal>,
-		deleting: Arc<AtomicBool>,
 		empty: Arc<SCondvar>,
-		sleep: Arc<AtomicBool>,
+		state: Arc<(Mutex<State>, Condvar)>,
+		id: usize,
 	) {
-		while !deleting.load(AtomicOrdering::Acquire) {
+		loop {
+			// check current state.
 			{
-				while sleep.load(AtomicOrdering::SeqCst) {
-					trace!(target: "verification", "Verifier sleeping");
-					::std::thread::park();
-					trace!(target: "verification", "Verifier waking up");
+				let mut cur_state = state.0.lock();
+				while let State::Work(x) = *cur_state {
+					// sleep until this thread is required.
+					if id < x { break }

-					if deleting.load(AtomicOrdering::Acquire) {
-						return;
-					}
+					debug!(target: "verification", "verifier {} sleeping", id);
+					state.1.wait(&mut cur_state);
+					debug!(target: "verification", "verifier {} waking up", id);					
+				}
+
+				if let State::Exit = *cur_state { 
+					debug!(target: "verification", "verifier {} exiting", id);										
+					break;
 				}
 			}

+			// wait for work if empty.
 			{
 				let mut more_to_verify = verification.more_to_verify.lock().unwrap();

@@ -305,15 +289,22 @@ impl<K: Kind> VerificationQueue<K> {
 					empty.notify_all();
 				}

-				while verification.unverified.lock().is_empty() && !deleting.load(AtomicOrdering::Acquire) {
+				while verification.unverified.lock().is_empty() {
+					if let State::Exit = *state.0.lock() {
+						debug!(target: "verification", "verifier {} exiting", id);
+						return;
+					}
+
 					more_to_verify = wait.wait(more_to_verify).unwrap();
 				}

-				if deleting.load(AtomicOrdering::Acquire) {
+				if let State::Exit = *state.0.lock() {
+					debug!(target: "verification", "verifier {} exiting", id);										
 					return;
 				}
 			}

+			// do work.
 			let item = {
 				// acquire these locks before getting the item to verify.
 				let mut unverified = verification.unverified.lock();
@@ -568,6 +559,14 @@ impl<K: Kind> VerificationQueue<K> {
 		}
 	}

+	/// Get the current number of working verifiers.
+	pub fn num_verifiers(&self) -> usize {
+		match *self.state.0.lock() {
+			State::Work(x) => x,
+			State::Exit => panic!("state only set to exit on drop; queue live now; qed"),
+		}
+	}
+
 	/// Optimise memory footprint of the heap fields, and adjust the number of threads
 	/// to better suit the workload.
 	pub fn collect_garbage(&self) {
@@ -604,7 +603,7 @@ impl<K: Kind> VerificationQueue<K> {
 			return;
 		}

-		let current = self.verifiers.lock().1;
+		let current = self.num_verifiers();

 		let diff = (v_len - u_len).abs();
 		let total = v_len + u_len;
@@ -626,27 +625,14 @@ impl<K: Kind> VerificationQueue<K> {
 	// possible, never going over the amount of initially allocated threads
 	// or below 1.
 	fn scale_verifiers(&self, target: usize) {
-		let mut verifiers = self.verifiers.lock();
-		let &mut (ref mut verifiers, ref mut verifier_count) = &mut *verifiers;
-
-		let target = min(verifiers.len(), target);
+		let current = self.num_verifiers();
+		let target = min(self.verifier_handles.len(), target);
 		let target = max(1, target);

-		debug!(target: "verification", "Scaling from {} to {} verifiers", verifier_count, target);
+		debug!(target: "verification", "Scaling from {} to {} verifiers", current, target);

-		// scaling up
-		for i in *verifier_count..target {
-			debug!(target: "verification", "Waking up verifier {}", i);
-			verifiers[i].wake_up();
-		}
-
-		// scaling down.
-		for i in target..*verifier_count {
-			debug!(target: "verification", "Putting verifier {} to sleep", i);
-			verifiers[i].sleep();
-		}
-
-		*verifier_count = target;
+		*self.state.0.lock() = State::Work(target);
+		self.state.1.notify_all();
 	}
 }

@@ -660,22 +646,18 @@ impl<K: Kind> Drop for VerificationQueue<K> {
 	fn drop(&mut self) {
 		trace!(target: "shutdown", "[VerificationQueue] Closing...");
 		self.clear();
-		self.deleting.store(true, AtomicOrdering::Release);
+		self.deleting.store(true, AtomicOrdering::SeqCst);

-		let mut verifiers = self.verifiers.get_mut();
-		let mut verifiers = &mut verifiers.0;
-
-		// first pass to signal conclusion. must be done before
-		// notify or deadlock possible.
-		for handle in verifiers.iter() {
-			handle.conclude();
-		}
+		// set exit state; should be done before `more_to_verify` notification.
+		*self.state.0.lock() = State::Exit;
+		self.state.1.notify_all();

+		// wake up all threads waiting for more work.
 		self.more_to_verify.notify_all();

-		// second pass to join.
-		for handle in verifiers.drain(..) {
-			handle.join();
+		// wait for all verifier threads to join.
+		for thread in self.verifier_handles.drain(..) {
+			thread.join().expect("Propagating verifier thread panic on shutdown");
 		}

 		trace!(target: "shutdown", "[VerificationQueue] Closed.");
@@ -687,7 +669,7 @@ mod tests {
 	use util::*;
 	use io::*;
 	use spec::*;
-	use super::{BlockQueue, Config};
+	use super::{BlockQueue, Config, State};
 	use super::kind::blocks::Unverified;
 	use tests::helpers::*;
 	use error::*;
@@ -784,11 +766,11 @@ mod tests {
 		let queue = get_test_queue();
 		queue.scale_verifiers(MAX_VERIFIERS + 1);

-		assert!(queue.verifiers.lock().1 < MAX_VERIFIERS + 1);
+		assert!(queue.num_verifiers() < MAX_VERIFIERS + 1);

 		queue.scale_verifiers(0);

-		assert!(queue.verifiers.lock().1 == 1);
+		assert!(queue.num_verifiers() == 1);
 	}

 	#[test]
@@ -797,14 +779,7 @@ mod tests {

 		// put all the verifiers to sleep to ensure 
 		// the test isn't timing sensitive.
-		let num_verifiers = {
-			let verifiers = queue.verifiers.lock();
-			for i in 0..verifiers.1 {
-				verifiers.0[i].sleep();
-			}
-
-			verifiers.1
-		};
+		*queue.state.0.lock() = State::Work(0);

 		for block in get_good_dummy_block_seq(5000) {
 			queue.import(Unverified::new(block)).expect("Block good by definition; qed");
@@ -812,20 +787,12 @@ mod tests {

 		// almost all unverified == bump verifier count.
 		queue.collect_garbage();
-		assert_eq!(queue.verifiers.lock().1, num_verifiers + 1);
-
-		// wake them up again and verify everything.
-		{
-			let verifiers = queue.verifiers.lock();
-			for i in 0..verifiers.1 {
-				verifiers.0[i].wake_up();
-			}
-		}
+		assert_eq!(queue.num_verifiers(), 1);

 		queue.flush();

 		// nothing to verify == use minimum number of verifiers.
 		queue.collect_garbage();
-		assert_eq!(queue.verifiers.lock().1, 1);
+		assert_eq!(queue.num_verifiers(), 1);
 	}
 }