diff --git a/src/bytes.rs b/src/bytes.rs
index 1f1ee8c05..91b0e849c 100644
--- a/src/bytes.rs
+++ b/src/bytes.rs
@@ -306,10 +306,28 @@ impl <T>FromBytes for T where T: FixedHash {
 			use std::{mem, ptr};
 
 			let mut res: T = mem::uninitialized();
-			ptr::copy(bytes.as_ptr(), res.mut_bytes().as_mut_ptr(), T::size());
+			ptr::copy(bytes.as_ptr(), res.as_slice_mut().as_mut_ptr(), T::size());
 
 			Ok(res)
 		}
 	}
 }
 
+// TODO: tests and additional docs for these two.
+
+/// Simple trait to allow for raw population of a Sized object from a byte slice.
+pub trait Populatable {
+	/// Populate self from byte slice `d` in a raw fashion.
+	fn populate_raw(&mut self, d: &[u8]);
+}
+
+impl<T> Populatable for T where T: Sized {
+	fn populate_raw(&mut self, d: &[u8]) {
+		use std::mem;
+		use std::slice;
+		use std::io::Write;
+		unsafe {
+			slice::from_raw_parts_mut(self as *mut T as *mut u8, mem::size_of::<T>())
+		}.write(&d).unwrap();
+	}
+}
diff --git a/src/crypto.rs b/src/crypto.rs
index 0d1ae9c05..9a1203921 100644
--- a/src/crypto.rs
+++ b/src/crypto.rs
@@ -3,9 +3,24 @@ use secp256k1::Secp256k1;
 use secp256k1::key;
 use rand::os::OsRng;
 
-pub type Secret=H256;
-pub type Public=H512;
-pub type Signature=H520;
+pub type Secret = H256;
+pub type Public = H512;
+pub type Signature = H520;
+
+impl Signature {
+	/// Create a new signature from the R, S and V componenets.
+	pub fn from_rsv(r: &H256, s: &H256, v: u8) -> Signature {
+		use std::ptr;
+		let mut ret: Signature = Signature::new();
+		unsafe {
+			let retslice: &mut [u8] = &mut ret;
+			ptr::copy(r.as_ptr(), retslice.as_mut_ptr(), 32);
+			ptr::copy(s.as_ptr(), retslice.as_mut_ptr().offset(32), 32);
+		}
+		ret[64] = v;
+		ret
+	}
+}
 
 #[derive(Debug)]
 pub enum CryptoError {
@@ -92,6 +107,9 @@ impl KeyPair {
 	pub fn secret(&self) -> &Secret {
 		&self.secret
 	}
+
+	/// Sign a message with our secret key.
+	pub fn sign(&self, message: &H256) -> Result<Signature, CryptoError> { sign(&self.secret, message) }
 }
 
 /// Recovers Public key from signed message hash.
@@ -102,8 +120,11 @@ pub fn recover(signature: &Signature, message: &H256) -> Result<Public, CryptoEr
 	let publ = try!(context.recover(&try!(Message::from_slice(&message)), &rsig));
 	let serialized = publ.serialize_vec(&context, false);
 	let p: Public = Public::from_slice(&serialized[1..65]);
+	//TODO: check if it's the zero key and fail if so.
+
 	Ok(p)
 }
+
 /// Returns siganture of message hash.
 pub fn sign(secret: &Secret, message: &H256) -> Result<Signature, CryptoError> {
 	use secp256k1::*;
@@ -116,6 +137,16 @@ pub fn sign(secret: &Secret, message: &H256) -> Result<Signature, CryptoError> {
 	signature[64] = rec_id.to_i32() as u8;
 	Ok(signature)
 }
+
+/// Check if each component of the signature is in range.
+pub fn is_valid(sig: &Signature) -> bool {
+	sig[64] <= 1 &&
+		H256::from_slice(&sig[0..32]) < h256_from_hex("fffffffffffffffffffffffffffffffebaaedce6af48a03bbfd25e8cd0364141") &&
+		H256::from_slice(&sig[32..64]) < h256_from_hex("fffffffffffffffffffffffffffffffebaaedce6af48a03bbfd25e8cd0364141") &&
+		H256::from_slice(&sig[32..64]) >= h256_from_u64(1) &&
+		H256::from_slice(&sig[0..32]) >= h256_from_u64(1)
+}
+
 /// Verify signature.
 pub fn verify(public: &Public, signature: &Signature, message: &H256) -> Result<bool, CryptoError> {
 	use secp256k1::*;
@@ -142,6 +173,8 @@ mod tests {
 	use hash::*;
 	use crypto::*;
 
+	// TODO: tests for sign/recover roundtrip, at least.
+
 	#[test]
 	fn test_signature() {
 		let pair = KeyPair::create().unwrap();
@@ -154,14 +187,14 @@ mod tests {
 
 	#[test]
 	fn test_invalid_key() {
-		assert!(KeyPair::from_secret(Secret::from_str("ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff").unwrap()).is_err());
-		assert!(KeyPair::from_secret(Secret::from_str("0000000000000000000000000000000000000000000000000000000000000000").unwrap()).is_err());
-		assert!(KeyPair::from_secret(Secret::from_str("fffffffffffffffffffffffffffffffebaaedce6af48a03bbfd25e8cd0364141").unwrap()).is_err());
+		assert!(KeyPair::from_secret(h256_from_hex("ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff")).is_err());
+		assert!(KeyPair::from_secret(h256_from_hex("0000000000000000000000000000000000000000000000000000000000000000")).is_err());
+		assert!(KeyPair::from_secret(h256_from_hex("fffffffffffffffffffffffffffffffebaaedce6af48a03bbfd25e8cd0364141")).is_err());
 	}
 
 	#[test]
 	fn test_key() {
-		let pair = KeyPair::from_secret(Secret::from_str("6f7b0d801bc7b5ce7bbd930b84fd0369b3eb25d09be58d64ba811091046f3aa2").unwrap()).unwrap();
+		let pair = KeyPair::from_secret(h256_from_hex("6f7b0d801bc7b5ce7bbd930b84fd0369b3eb25d09be58d64ba811091046f3aa2")).unwrap();
 		assert_eq!(pair.public().hex(), "101b3ef5a4ea7a1c7928e24c4c75fd053c235d7b80c22ae5c03d145d0ac7396e2a4ffff9adee3133a7b05044a5cee08115fd65145e5165d646bde371010d803c");
 	}
 }
diff --git a/src/hash.rs b/src/hash.rs
index ea041f2ac..e6f9a61c7 100644
--- a/src/hash.rs
+++ b/src/hash.rs
@@ -5,6 +5,7 @@ use std::fmt;
 use std::ops;
 use std::hash::{Hash, Hasher};
 use std::ops::{Index, IndexMut, Deref, DerefMut, BitOr, BitAnd};
+use std::cmp::{PartialOrd, Ordering};
 use rustc_serialize::hex::*;
 use error::EthcoreError;
 use rand::Rng;
@@ -21,7 +22,7 @@ pub trait FixedHash: Sized + BytesConvertable {
 	fn random() -> Self;
 	fn randomize(&mut self);
 	fn size() -> usize;
-	fn mut_bytes(&mut self) -> &mut [u8];
+	fn as_slice_mut(&mut self) -> &mut [u8];
 	fn from_slice(src: &[u8]) -> Self;
 	fn clone_from_slice(&mut self, src: &[u8]) -> usize;
 	fn shift_bloom<'a, T>(&'a mut self, b: &T) -> &'a mut Self where T: FixedHash;
@@ -77,7 +78,7 @@ macro_rules! impl_hash {
 				$size
 			}
 
-			fn mut_bytes(&mut self) -> &mut [u8] {
+			fn as_slice_mut(&mut self) -> &mut [u8] {
 				&mut self.0
 			}
 
@@ -142,7 +143,7 @@ macro_rules! impl_hash {
 						ptr += 1;
 					}
 					index &= mask;
-					ret.mut_bytes()[m - 1 - index / 8] |= 1 << (index % 8);
+					ret.as_slice_mut()[m - 1 - index / 8] |= 1 << (index % 8);
 				}
 
 				ret
@@ -208,6 +209,19 @@ macro_rules! impl_hash {
 			}
 		}
 
+		impl PartialOrd for $from {
+			fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+				for i in 0..$size {
+					if self.0[i] > other.0[i] {
+						return Some(Ordering::Greater);
+					} else if self.0[i] < other.0[i] {
+						return Some(Ordering::Less);
+					}
+				}
+				Some(Ordering::Equal)
+			}
+		}
+
 		impl Hash for $from {
 			fn hash<H>(&self, state: &mut H) where H: Hasher {
 				state.write(&self.0);
@@ -311,7 +325,7 @@ macro_rules! impl_hash {
 }
 
 impl<'a> From<&'a U256> for H256 {
-    fn from(value: &'a U256) -> H256 {
+	fn from(value: &'a U256) -> H256 {
 		unsafe {
 			let mut ret: H256 = ::std::mem::uninitialized();
 			value.to_bytes(&mut ret);
@@ -340,6 +354,26 @@ impl From<Address> for H256 {
 	}
 }
 
+pub fn h256_from_hex(s: &str) -> H256 {
+	use std::str::FromStr;
+	H256::from_str(s).unwrap()
+}
+
+pub fn h256_from_u64(n: u64) -> H256 {
+	use uint::U256;
+	H256::from(&U256::from(n))
+}
+
+pub fn address_from_hex(s: &str) -> Address {
+	use std::str::FromStr;
+	Address::from_str(s).unwrap()
+}
+
+pub fn address_from_u64(n: u64) -> Address {
+	let h256 = h256_from_u64(n);
+	From::from(h256)
+}
+
 impl_hash!(H32, 4);
 impl_hash!(H64, 8);
 impl_hash!(H128, 16);
diff --git a/src/rlp/rlpstream.rs b/src/rlp/rlpstream.rs
index 43ae83a9a..3a19cab7d 100644
--- a/src/rlp/rlpstream.rs
+++ b/src/rlp/rlpstream.rs
@@ -193,8 +193,11 @@ impl Encoder for BasicEncoder {
 		}
 	}
 
-	fn emit_list<F>(&mut self, f: F) -> () where F: FnOnce(&mut Self) -> ()
-	{
+	fn emit_raw(&mut self, bytes: &[u8]) -> () {
+		self.bytes.append_slice(bytes);
+	}
+
+	fn emit_list<F>(&mut self, f: F) -> () where F: FnOnce(&mut Self) -> () {
 		// get len before inserting a list
 		let before_len = self.bytes.len();
 
diff --git a/src/rlp/rlptraits.rs b/src/rlp/rlptraits.rs
index 067c438bf..5955e132d 100644
--- a/src/rlp/rlptraits.rs
+++ b/src/rlp/rlptraits.rs
@@ -5,6 +5,8 @@ pub trait Decoder: Sized {
 		where F: FnOnce(&[u8]) -> Result<T, DecoderError>;
 
 	fn as_list(&self) -> Result<Vec<Self>, DecoderError>;
+
+	fn as_raw(&self) -> &[u8];
 }
 
 pub trait Decodable: Sized {
@@ -185,6 +187,7 @@ pub trait View<'a, 'view>: Sized {
 pub trait Encoder {
 	fn emit_value(&mut self, bytes: &[u8]) -> ();
 	fn emit_list<F>(&mut self, f: F) -> () where F: FnOnce(&mut Self) -> ();
+	fn emit_raw(&mut self, bytes: &[u8]) -> ();
 }
 
 pub trait Encodable {
diff --git a/src/rlp/untrusted_rlp.rs b/src/rlp/untrusted_rlp.rs
index a8cecf09f..68956d8d0 100644
--- a/src/rlp/untrusted_rlp.rs
+++ b/src/rlp/untrusted_rlp.rs
@@ -305,6 +305,10 @@ impl<'a> Decoder for BasicDecoder<'a> {
 		}
 	}
 
+	fn as_raw(&self) -> &[u8] {
+		self.rlp.raw()
+	}
+
 	fn as_list(&self) -> Result<Vec<Self>, DecoderError> {
 		let v: Vec<BasicDecoder<'a>> = self.rlp.iter()
 			.map(| i | BasicDecoder::new(i))
diff --git a/src/sha3.rs b/src/sha3.rs
index b3676720c..e1337c5f7 100644
--- a/src/sha3.rs
+++ b/src/sha3.rs
@@ -27,7 +27,7 @@ impl<T> Hashable for T where T: BytesConvertable {
 			let mut keccak = Keccak::new_keccak256();
 			keccak.update(self.bytes());
 			let mut ret: H256 = uninitialized();
-			keccak.finalize(ret.mut_bytes());
+			keccak.finalize(ret.as_slice_mut());
 			ret
 		}
 	}
diff --git a/src/trie/triedbmut.rs b/src/trie/triedbmut.rs
index 4c78e7667..e04b7c758 100644
--- a/src/trie/triedbmut.rs
+++ b/src/trie/triedbmut.rs
@@ -686,7 +686,7 @@ mod tests {
 			0 => encode(&j),
 			_ => {
 				let mut h = H256::new();
-				h.mut_bytes()[31] = j as u8;
+				h.as_slice_mut()[31] = j as u8;
 				encode(&h)
 			},
 		}