diff --git a/ethcore/res/authority_round.json b/ethcore/res/authority_round.json
index 85beb51b4..efc0cdeb4 100644
--- a/ethcore/res/authority_round.json
+++ b/ethcore/res/authority_round.json
@@ -21,8 +21,9 @@
 	},
 	"genesis": {
 		"seal": {
-			"generic": {
-				"rlp": "0xc28080"
+			"authority_round": {
+				"step": "0x0",
+				"signature": "0x0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
 			}
 		},
 		"difficulty": "0x20000",
diff --git a/ethcore/res/basic_authority.json b/ethcore/res/basic_authority.json
index 51276d487..db4374160 100644
--- a/ethcore/res/basic_authority.json
+++ b/ethcore/res/basic_authority.json
@@ -17,10 +17,7 @@
 	},
 	"genesis": {
 		"seal": {
-			"generic": {
-				"fields": 1,
-				"rlp": "0x11bbe8db4e347b4e8c937c1c8370e4b5ed33adb3db69cbdb7a38e1e50b1b82fa"
-			}
+			"generic": "0x11bbe8db4e347b4e8c937c1c8370e4b5ed33adb3db69cbdb7a38e1e50b1b82fa"
 		},
 		"difficulty": "0x20000",
 		"author": "0x0000000000000000000000000000000000000000",
diff --git a/ethcore/res/instant_seal.json b/ethcore/res/instant_seal.json
index 3bbcab9f8..6a3964e89 100644
--- a/ethcore/res/instant_seal.json
+++ b/ethcore/res/instant_seal.json
@@ -11,9 +11,7 @@
 	},
 	"genesis": {
 		"seal": {
-			"generic": {
-				"rlp": "0x0"
-			}
+			"generic": "0x0"
 		},
 		"difficulty": "0x20000",
 		"author": "0x0000000000000000000000000000000000000000",
diff --git a/ethcore/src/spec/seal.rs b/ethcore/src/spec/seal.rs
index eaf951189..d5257ab79 100644
--- a/ethcore/src/spec/seal.rs
+++ b/ethcore/src/spec/seal.rs
@@ -17,7 +17,7 @@
 //! Spec seal.
 
 use rlp::*;
-use util::hash::{H64, H256};
+use util::hash::{H64, H256, H520};
 use ethjson;
 
 /// Classic ethereum seal.
@@ -32,23 +32,35 @@ impl Into<Generic> for Ethereum {
 	fn into(self) -> Generic {
 		let mut s = RlpStream::new_list(2);
 		s.append(&self.mix_hash).append(&self.nonce);
-		Generic {
-			rlp: s.out()
-		}
+		Generic(s.out())
 	}
 }
 
-/// Generic seal.
-pub struct Generic {
-	/// Seal rlp.
-	pub rlp: Vec<u8>,
+/// AuthorityRound seal.
+pub struct AuthorityRound {
+	/// Seal step.
+	pub step: usize,
+	/// Seal signature.
+	pub signature: H520,
 }
 
+impl Into<Generic> for AuthorityRound {
+	fn into(self) -> Generic {
+		let mut s = RlpStream::new_list(2);
+		s.append(&self.step).append(&self.signature);
+		Generic(s.out())
+	}
+}
+
+pub struct Generic(pub Vec<u8>);
+
 /// Genesis seal type.
 pub enum Seal {
 	/// Classic ethereum seal.
 	Ethereum(Ethereum),
-	/// Generic seal.
+	/// AuthorityRound seal.
+	AuthorityRound(AuthorityRound),
+	/// Generic RLP seal.
 	Generic(Generic),
 }
 
@@ -59,9 +71,11 @@ impl From<ethjson::spec::Seal> for Seal {
 				nonce: eth.nonce.into(),
 				mix_hash: eth.mix_hash.into()
 			}),
-			ethjson::spec::Seal::Generic(g) => Seal::Generic(Generic {
-				rlp: g.rlp.into()
-			})
+			ethjson::spec::Seal::AuthorityRound(ar) => Seal::AuthorityRound(AuthorityRound {
+				step: ar.step.into(),
+				signature: ar.signature.into()
+			}),
+			ethjson::spec::Seal::Generic(g) => Seal::Generic(Generic(g.into())),
 		}
 	}
 }
@@ -70,7 +84,8 @@ impl Into<Generic> for Seal {
 	fn into(self) -> Generic {
 		match self {
 			Seal::Generic(generic) => generic,
-			Seal::Ethereum(eth) => eth.into()
+			Seal::Ethereum(eth) => eth.into(),
+			Seal::AuthorityRound(ar) => ar.into(),
 		}
 	}
 }
diff --git a/ethcore/src/spec/spec.rs b/ethcore/src/spec/spec.rs
index 5d0cc8360..bfd2ebd1d 100644
--- a/ethcore/src/spec/spec.rs
+++ b/ethcore/src/spec/spec.rs
@@ -107,7 +107,7 @@ impl From<ethjson::spec::Spec> for Spec {
 	fn from(s: ethjson::spec::Spec) -> Self {
 		let builtins = s.accounts.builtins().into_iter().map(|p| (p.0.into(), From::from(p.1))).collect();
 		let g = Genesis::from(s.genesis);
-		let seal: GenericSeal = g.seal.into();
+		let GenericSeal(seal_rlp) = g.seal.into();
 		let params = CommonParams::from(s.params);
 		Spec {
 			name: s.name.into(),
@@ -124,7 +124,7 @@ impl From<ethjson::spec::Spec> for Spec {
 			gas_used: g.gas_used,
 			timestamp: g.timestamp,
 			extra_data: g.extra_data,
-			seal_rlp: seal.rlp,
+			seal_rlp: seal_rlp,
 			state_root_memo: RwLock::new(g.state_root),
 			genesis_state: From::from(s.accounts),
 		}
@@ -208,7 +208,7 @@ impl Spec {
 
 	/// Overwrite the genesis components.
 	pub fn overwrite_genesis_params(&mut self, g: Genesis) {
-		let seal: GenericSeal = g.seal.into();
+		let GenericSeal(seal_rlp) = g.seal.into();
 		self.parent_hash = g.parent_hash;
 		self.transactions_root = g.transactions_root;
 		self.receipts_root = g.receipts_root;
@@ -218,7 +218,7 @@ impl Spec {
 		self.gas_used = g.gas_used;
 		self.timestamp = g.timestamp;
 		self.extra_data = g.extra_data;
-		self.seal_rlp = seal.rlp;
+		self.seal_rlp = seal_rlp;
 		self.state_root_memo = RwLock::new(g.state_root);
 	}
 
diff --git a/json/src/hash.rs b/json/src/hash.rs
index 9aad33115..b09c596f1 100644
--- a/json/src/hash.rs
+++ b/json/src/hash.rs
@@ -20,7 +20,7 @@ use std::str::FromStr;
 use serde::{Deserialize, Deserializer, Serialize, Serializer, Error};
 use serde::de::Visitor;
 use rustc_serialize::hex::ToHex;
-use util::hash::{H64 as Hash64, H160 as Hash160, H256 as Hash256, H2048 as Hash2048};
+use util::hash::{H64 as Hash64, H160 as Hash160, H256 as Hash256, H520 as Hash520, H2048 as Hash2048};
 
 
 macro_rules! impl_hash {
@@ -87,6 +87,7 @@ macro_rules! impl_hash {
 impl_hash!(H64, Hash64);
 impl_hash!(Address, Hash160);
 impl_hash!(H256, Hash256);
+impl_hash!(H520, Hash520);
 impl_hash!(Bloom, Hash2048);
 
 #[cfg(test)]
diff --git a/json/src/spec/mod.rs b/json/src/spec/mod.rs
index 19b9974d9..dcd1f3361 100644
--- a/json/src/spec/mod.rs
+++ b/json/src/spec/mod.rs
@@ -33,7 +33,7 @@ pub use self::builtin::{Builtin, Pricing, Linear};
 pub use self::genesis::Genesis;
 pub use self::params::Params;
 pub use self::spec::Spec;
-pub use self::seal::{Seal, Ethereum, Generic};
+pub use self::seal::{Seal, Ethereum, AuthorityRoundSeal};
 pub use self::engine::Engine;
 pub use self::state::State;
 pub use self::ethash::{Ethash, EthashParams};
diff --git a/json/src/spec/seal.rs b/json/src/spec/seal.rs
index eba75840a..d586ed501 100644
--- a/json/src/spec/seal.rs
+++ b/json/src/spec/seal.rs
@@ -16,7 +16,8 @@
 
 //! Spec seal deserialization.
 
-use hash::{H64, H256};
+use hash::*;
+use uint::Uint;
 use bytes::Bytes;
 
 /// Ethereum seal.
@@ -29,11 +30,13 @@ pub struct Ethereum {
 	pub mix_hash: H256,
 }
 
-/// Generic seal.
+/// AuthorityRound seal.
 #[derive(Debug, PartialEq, Deserialize)]
-pub struct Generic {
-	/// Seal rlp.
-	pub rlp: Bytes,
+pub struct AuthorityRoundSeal {
+	/// Seal step.
+	pub step: Uint,
+	/// Seal signature.
+	pub signature: H520,
 }
 
 /// Seal variants.
@@ -42,9 +45,12 @@ pub enum Seal {
 	/// Ethereum seal.
 	#[serde(rename="ethereum")]
 	Ethereum(Ethereum),
+	/// AuthorityRound seal.
+	#[serde(rename="authority_round")]
+	AuthorityRound(AuthorityRoundSeal),
 	/// Generic seal.
 	#[serde(rename="generic")]
-	Generic(Generic),
+	Generic(Bytes),
 }
 
 #[cfg(test)]
@@ -53,15 +59,18 @@ mod tests {
 	use spec::Seal;
 
 	#[test]
-	fn builtin_deserialization() {
+	fn seal_deserialization() {
 		let s = r#"[{
 			"ethereum": {
 				"nonce": "0x0000000000000042",
 				"mixHash": "0x0000000000000000000000000000000000000000000000000000000000000000"
 			}
 		},{
-			"generic": {
-				"rlp": "0xe011bbe8db4e347b4e8c937c1c8370e4b5ed33adb3db69cbdb7a38e1e50b1b82fa"
+			"generic": "0xe011bbe8db4e347b4e8c937c1c8370e4b5ed33adb3db69cbdb7a38e1e50b1b82fa"
+		},{
+			"authority_round": {
+				"step": "0x0",
+				"signature": "0x0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
 			}
 		}]"#;
 		let _deserialized: Vec<Seal> = serde_json::from_str(s).unwrap();