diff --git a/Cargo.lock b/Cargo.lock
index 1a701042e..daf0501ba 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -216,6 +216,7 @@ dependencies = [
  "ethash 1.1.0",
  "ethcore-devtools 1.1.0",
  "ethcore-util 1.1.0",
+ "ethjson 0.1.0",
  "heapsize 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "lazy_static 0.1.15 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.3.5 (registry+https://github.com/rust-lang/crates.io-index)",
diff --git a/ethcore/Cargo.toml b/ethcore/Cargo.toml
index 1d16cc34a..cf75949f1 100644
--- a/ethcore/Cargo.toml
+++ b/ethcore/Cargo.toml
@@ -21,6 +21,7 @@ clippy = { version = "0.0.50", optional = true }
 crossbeam = "0.1.5"
 lazy_static = "0.1"
 ethcore-devtools = { path = "../devtools" }
+ethjson = { path = "../json" }
 
 [features]
 jit = ["evmjit"]
diff --git a/ethcore/src/lib.rs b/ethcore/src/lib.rs
index 572cda2fa..662dea641 100644
--- a/ethcore/src/lib.rs
+++ b/ethcore/src/lib.rs
@@ -83,6 +83,7 @@ extern crate time;
 extern crate env_logger;
 extern crate num_cpus;
 extern crate crossbeam;
+extern crate ethjson;
 
 #[cfg(test)] extern crate ethcore_devtools as devtools;
 #[cfg(feature = "jit" )] extern crate evmjit;
diff --git a/ethcore/src/spec/genesis.rs b/ethcore/src/spec/genesis.rs
new file mode 100644
index 000000000..686e8f6d1
--- /dev/null
+++ b/ethcore/src/spec/genesis.rs
@@ -0,0 +1,91 @@
+// 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/>.
+
+use util::rlp::*;
+use util::numbers::{Uint, U256};
+use util::hash::{H64, Address, H256};
+use ethjson;
+
+/// Genesis seal type.
+pub enum Seal {
+	/// Classic ethereum seal.
+	Ethereum {
+		/// Seal nonce.
+		nonce: H64,
+		/// Seal mix hash.
+		mix_hash: H256,
+	},
+	/// Generic seal.
+	Generic {
+		/// Number of seal fields.
+		fields: usize,
+		/// Seal rlp.
+		rlp: Vec<u8>,
+	},
+}
+
+/// Genesis components.
+pub struct Genesis {
+	/// Seal.
+	pub seal: Seal,
+	/// Difficulty.
+	pub difficulty: U256,
+	/// Author.
+	pub author: Address,
+	/// Timestamp.
+	pub timestamp: u64,
+	/// Parent hash.
+	pub parent_hash: H256,
+	/// Gas limit.
+	pub gas_limit: U256,
+	/// Transactions root.
+	pub transactions_root: H256,
+	/// Receipts root.
+	pub receipts_root: H256,
+	/// State root.
+	pub state_root: Option<H256>,
+	/// Gas used.
+	pub gas_used: U256,
+	/// Extra data.
+	pub extra_data: Vec<u8>,
+}
+
+impl From<ethjson::spec::Genesis> for Genesis {
+	fn from(g: ethjson::spec::Genesis) -> Self {
+		Genesis {
+			seal: match (g.nonce, g.mix_hash) {
+				(Some(nonce), Some(mix_hash)) => Seal::Ethereum {
+					nonce: nonce.into(),
+					mix_hash: mix_hash.into(),
+				},
+				_ => Seal::Generic {
+					fields: g.seal_fields.unwrap(),
+					rlp: g.seal_rlp.unwrap().into(),
+				}
+			},
+			difficulty: g.difficulty.into(),
+			author: g.author.into(),
+			timestamp: g.timestamp.into(),
+			parent_hash: g.parent_hash.into(),
+			gas_limit: g.gas_limit.into(),
+			transactions_root: g.transactions_root.map_or_else(|| SHA3_NULL_RLP.clone(), Into::into),
+			receipts_root: g.receipts_root.map_or_else(|| SHA3_NULL_RLP.clone(), Into::into),
+			state_root: g.state_root.map(Into::into),
+			gas_used: g.gas_used.map_or_else(U256::zero, Into::into),
+			extra_data: g.extra_data.map_or_else(Vec::new, Into::into),
+		}
+	}
+}
diff --git a/ethcore/src/spec/mod.rs b/ethcore/src/spec/mod.rs
new file mode 100644
index 000000000..e9c7a0356
--- /dev/null
+++ b/ethcore/src/spec/mod.rs
@@ -0,0 +1,22 @@
+// 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/>.
+
+//! Blockchain params.
+
+mod genesis;
+pub mod spec;
+
+pub use self::spec::*;
diff --git a/ethcore/src/spec.rs b/ethcore/src/spec/spec.rs
similarity index 92%
rename from ethcore/src/spec.rs
rename to ethcore/src/spec/spec.rs
index 2208350cc..c7e2e4e9f 100644
--- a/ethcore/src/spec.rs
+++ b/ethcore/src/spec/spec.rs
@@ -21,6 +21,8 @@ use engine::*;
 use pod_state::*;
 use null_engine::*;
 use account_db::*;
+use ethereum;
+use super::genesis::{Seal as GenesisSeal, Genesis};
 
 /// Convert JSON value to equivalent RLP representation.
 // TODO: handle container types.
@@ -106,7 +108,7 @@ impl Spec {
 	pub fn to_engine(self) -> Result<Box<Engine>, Error> {
 		match self.engine_name.as_ref() {
 			"NullEngine" => Ok(NullEngine::new_boxed(self)),
-			"Ethash" => Ok(super::ethereum::Ethash::new_boxed(self)),
+			"Ethash" => Ok(ethereum::Ethash::new_boxed(self)),
 			_ => Err(Error::UnknownEngineName(self.engine_name.clone()))
 		}
 	}
@@ -197,6 +199,32 @@ impl Spec {
 		self.state_root_memo = RwLock::new(genesis.find("stateRoot").and_then(|_| Some(H256::from_json(&genesis["stateRoot"]))));
 	}
 
+	/// Overwrite the genesis components.
+	pub fn overwrite_genesis_params(&mut self, g: Genesis) {
+		let (seal_fields, seal_rlp) = match g.seal {
+			GenesisSeal::Generic { fields, rlp } => (fields, rlp),
+			GenesisSeal::Ethereum { nonce, mix_hash } => {
+				let mut s = RlpStream::new();
+				s.append(&mix_hash);
+				s.append(&nonce);
+				(2, s.out())
+			}
+		};
+
+		self.parent_hash = g.parent_hash;
+		self.transactions_root = g.transactions_root;
+		self.receipts_root = g.receipts_root;
+		self.author = g.author;
+		self.difficulty = g.difficulty;
+		self.gas_limit = g.gas_limit;
+		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);
+	}
+
 	/// Alter the value of the genesis state.
 	pub fn set_genesis_state(&mut self, s: PodState) {
 		self.genesis_state = s;
@@ -304,7 +332,7 @@ impl Spec {
 	}
 
 	/// Create a new Spec which conforms to the Morden chain except that it's a NullEngine consensus.
-	pub fn new_test() -> Spec { Self::from_json_utf8(include_bytes!("../res/null_morden.json")) }
+	pub fn new_test() -> Spec { Self::from_json_utf8(include_bytes!("../../res/null_morden.json")) }
 }
 
 #[cfg(test)]
diff --git a/json/src/blockchain/blockchain.rs b/json/src/blockchain/blockchain.rs
index 75d321a4d..d9e879ae9 100644
--- a/json/src/blockchain/blockchain.rs
+++ b/json/src/blockchain/blockchain.rs
@@ -59,6 +59,11 @@ impl BlockChain {
 			timestamp: self.genesis_block.timestamp,
 			parent_hash: self.genesis_block.parent_hash.clone(),
 			gas_limit: self.genesis_block.gas_limit,
+			transactions_root: Some(self.genesis_block.transactions_root.clone()),
+			receipts_root: Some(self.genesis_block.receipts_root.clone()),
+			state_root: Some(self.genesis_block.state_root.clone()),
+			gas_used: Some(self.genesis_block.gas_used),
+			extra_data: Some(self.genesis_block.extra_data.clone()),
 		}
 	}
 }
diff --git a/json/src/blockchain/header.rs b/json/src/blockchain/header.rs
index f4ebee01b..ece6d6359 100644
--- a/json/src/blockchain/header.rs
+++ b/json/src/blockchain/header.rs
@@ -53,7 +53,7 @@ pub struct Header {
 	pub parent_hash: H256,
 	/// Receipt root.
 	#[serde(rename="receiptTrie")]
-	pub receipt_root: H256,
+	pub receipts_root: H256,
 	/// State root.
 	#[serde(rename="stateRoot")]
 	pub state_root: H256,
diff --git a/json/src/spec/genesis.rs b/json/src/spec/genesis.rs
index a8b5b30e3..a2b484397 100644
--- a/json/src/spec/genesis.rs
+++ b/json/src/spec/genesis.rs
@@ -33,7 +33,7 @@ pub struct Genesis {
 	// new seal // TODO: consider moving it to a separate seal structure
 	#[serde(rename="sealFields")]
 	/// Number of seal fields.
-	pub seal_fields: Option<Uint>,
+	pub seal_fields: Option<usize>,
 	#[serde(rename="sealRlp")]
 	/// Seal rlp.
 	pub seal_rlp: Option<Bytes>,
@@ -50,6 +50,21 @@ pub struct Genesis {
 	/// Gas limit.
 	#[serde(rename="gasLimit")]
 	pub gas_limit: Uint,
+	/// Transactions root.
+	#[serde(rename="transactionsRoot")]
+	pub transactions_root: Option<H256>,
+	/// Receipts root.
+	#[serde(rename="receiptsRoot")]
+	pub receipts_root: Option<H256>,
+	/// State root.
+	#[serde(rename="stateRoot")]
+	pub state_root: Option<H256>,
+	/// Gas used.
+	#[serde(rename="gasUsed")]
+	pub gas_used: Option<Uint>,
+	/// Extra data.
+	#[serde(rename="extraData")]
+	pub extra_data: Option<Bytes>,
 }
 
 #[cfg(test)]
diff --git a/json/src/uint.rs b/json/src/uint.rs
index 2d24c3f7e..f6eae80e4 100644
--- a/json/src/uint.rs
+++ b/json/src/uint.rs
@@ -31,6 +31,12 @@ impl Into<U256> for Uint {
 	}
 }
 
+impl Into<u64> for Uint {
+	fn into(self) -> u64 {
+		u64::from(self.0)
+	}
+}
+
 impl Deserialize for Uint {
 	fn deserialize<D>(deserializer: &mut D) -> Result<Self, D::Error>
 		where D: Deserializer {