Merge branch 'master' into lmd-ghost

eth2/types/src/attestation.rs

@@ -2,7 +2,7 @@ use super::{AttestationData, Bitfield};
 use crate::test_utils::TestRandom;
 use bls::AggregateSignature;
 use rand::RngCore;
-use ssz::{Decodable, DecodeError, Encodable, SszStream};
+use ssz::{hash, Decodable, DecodeError, Encodable, SszStream, TreeHash};
 
 #[derive(Debug, Clone, PartialEq)]
 pub struct Attestation {
@@ -49,6 +49,17 @@ impl Attestation {
     }
 }
 
+impl TreeHash for Attestation {
+    fn hash_tree_root(&self) -> Vec<u8> {
+        let mut result: Vec<u8> = vec![];
+        result.append(&mut self.data.hash_tree_root());
+        result.append(&mut self.aggregation_bitfield.hash_tree_root());
+        result.append(&mut self.custody_bitfield.hash_tree_root());
+        result.append(&mut self.aggregate_signature.hash_tree_root());
+        hash(&result)
+    }
+}
+
 impl<T: RngCore> TestRandom<T> for Attestation {
     fn random_for_test(rng: &mut T) -> Self {
         Self {
@@ -76,4 +87,16 @@ mod tests {
 
         assert_eq!(original, decoded);
     }
+
+    #[test]
+    pub fn test_hash_tree_root() {
+        let mut rng = XorShiftRng::from_seed([42; 16]);
+        let original = Attestation::random_for_test(&mut rng);
+
+        let result = original.hash_tree_root();
+
+        assert_eq!(result.len(), 32);
+        // TODO: Add further tests
+        // https://github.com/sigp/lighthouse/issues/170
+    }
 }

eth2/types/src/attestation_data.rs

@@ -1,7 +1,7 @@
 use super::Hash256;
 use crate::test_utils::TestRandom;
 use rand::RngCore;
-use ssz::{Decodable, DecodeError, Encodable, SszStream};
+use ssz::{hash, Decodable, DecodeError, Encodable, SszStream, TreeHash};
 
 pub const SSZ_ATTESTION_DATA_LENGTH: usize = {
     8 +             // slot
@@ -85,6 +85,21 @@ impl Decodable for AttestationData {
     }
 }
 
+impl TreeHash for AttestationData {
+    fn hash_tree_root(&self) -> Vec<u8> {
+        let mut result: Vec<u8> = vec![];
+        result.append(&mut self.slot.hash_tree_root());
+        result.append(&mut self.shard.hash_tree_root());
+        result.append(&mut self.beacon_block_root.hash_tree_root());
+        result.append(&mut self.epoch_boundary_root.hash_tree_root());
+        result.append(&mut self.shard_block_root.hash_tree_root());
+        result.append(&mut self.latest_crosslink_root.hash_tree_root());
+        result.append(&mut self.justified_slot.hash_tree_root());
+        result.append(&mut self.justified_block_root.hash_tree_root());
+        hash(&result)
+    }
+}
+
 impl<T: RngCore> TestRandom<T> for AttestationData {
     fn random_for_test(rng: &mut T) -> Self {
         Self {
@@ -116,4 +131,16 @@ mod tests {
 
         assert_eq!(original, decoded);
     }
+
+    #[test]
+    pub fn test_hash_tree_root() {
+        let mut rng = XorShiftRng::from_seed([42; 16]);
+        let original = AttestationData::random_for_test(&mut rng);
+
+        let result = original.hash_tree_root();
+
+        assert_eq!(result.len(), 32);
+        // TODO: Add further tests
+        // https://github.com/sigp/lighthouse/issues/170
+    }
 }

eth2/types/src/attestation_data_and_custody_bit.rs

@@ -1,7 +1,7 @@
 use super::AttestationData;
 use crate::test_utils::TestRandom;
 use rand::RngCore;
-use ssz::{Decodable, DecodeError, Encodable, SszStream};
+use ssz::{hash, Decodable, DecodeError, Encodable, SszStream, TreeHash};
 
 #[derive(Debug, Clone, PartialEq, Default)]
 pub struct AttestationDataAndCustodyBit {
@@ -27,6 +27,16 @@ impl Decodable for AttestationDataAndCustodyBit {
     }
 }
 
+impl TreeHash for AttestationDataAndCustodyBit {
+    fn hash_tree_root(&self) -> Vec<u8> {
+        let mut result: Vec<u8> = vec![];
+        result.append(&mut self.data.hash_tree_root());
+        // TODO: add bool ssz
+        // result.append(custody_bit.hash_tree_root());
+        ssz::hash(&result)
+    }
+}
+
 impl<T: RngCore> TestRandom<T> for AttestationDataAndCustodyBit {
     fn random_for_test(rng: &mut T) -> Self {
         Self {
@@ -55,4 +65,16 @@ mod test {
 
         assert_eq!(original, decoded);
     }
+
+    #[test]
+    pub fn test_hash_tree_root() {
+        let mut rng = XorShiftRng::from_seed([42; 16]);
+        let original = AttestationDataAndCustodyBit::random_for_test(&mut rng);
+
+        let result = original.hash_tree_root();
+
+        assert_eq!(result.len(), 32);
+        // TODO: Add further tests
+        // https://github.com/sigp/lighthouse/issues/170
+    }
 }

eth2/types/src/beacon_block/mod.rs

@@ -3,7 +3,7 @@ use crate::test_utils::TestRandom;
 use bls::Signature;
 use hashing::canonical_hash;
 use rand::RngCore;
-use ssz::{ssz_encode, Decodable, DecodeError, Encodable, SszStream};
+use ssz::{hash, ssz_encode, Decodable, DecodeError, Encodable, SszStream, TreeHash};
 
 mod signing;
 
@@ -63,6 +63,20 @@ impl Decodable for BeaconBlock {
     }
 }
 
+impl TreeHash for BeaconBlock {
+    fn hash_tree_root(&self) -> Vec<u8> {
+        let mut result: Vec<u8> = vec![];
+        result.append(&mut self.slot.hash_tree_root());
+        result.append(&mut self.parent_root.hash_tree_root());
+        result.append(&mut self.state_root.hash_tree_root());
+        result.append(&mut self.randao_reveal.hash_tree_root());
+        result.append(&mut self.eth1_data.hash_tree_root());
+        result.append(&mut self.signature.hash_tree_root());
+        result.append(&mut self.body.hash_tree_root());
+        hash(&result)
+    }
+}
+
 impl<T: RngCore> TestRandom<T> for BeaconBlock {
     fn random_for_test(rng: &mut T) -> Self {
         Self {
@@ -93,4 +107,16 @@ mod tests {
 
         assert_eq!(original, decoded);
     }
+
+    #[test]
+    pub fn test_hash_tree_root() {
+        let mut rng = XorShiftRng::from_seed([42; 16]);
+        let original = BeaconBlock::random_for_test(&mut rng);
+
+        let result = original.hash_tree_root();
+
+        assert_eq!(result.len(), 32);
+        // TODO: Add further tests
+        // https://github.com/sigp/lighthouse/issues/170
+    }
 }

eth2/types/src/beacon_block/signing.rs

@@ -1,5 +1,5 @@
 use crate::{BeaconBlock, ChainSpec, Hash256, ProposalSignedData};
-use hashing::hash_tree_root;
+use ssz::TreeHash;
 
 impl BeaconBlock {
     pub fn proposal_root(&self, spec: &ChainSpec) -> Hash256 {
@@ -14,6 +14,6 @@ impl BeaconBlock {
             shard: spec.beacon_chain_shard_number,
             block_root: block_without_signature_root,
         };
-        Hash256::from_slice(&hash_tree_root(&proposal)[..])
+        Hash256::from_slice(&proposal.hash_tree_root()[..])
     }
 }

eth2/types/src/beacon_block_body.rs

@@ -1,7 +1,7 @@
 use super::{Attestation, CasperSlashing, Deposit, Exit, ProposerSlashing};
 use crate::test_utils::TestRandom;
 use rand::RngCore;
-use ssz::{Decodable, DecodeError, Encodable, SszStream};
+use ssz::{hash, Decodable, DecodeError, Encodable, SszStream, TreeHash};
 
 // The following types are just dummy classes as they will not be defined until
 // Phase 1 (Sharding phase)
@@ -61,6 +61,21 @@ impl Decodable for BeaconBlockBody {
     }
 }
 
+impl TreeHash for BeaconBlockBody {
+    fn hash_tree_root(&self) -> Vec<u8> {
+        let mut result: Vec<u8> = vec![];
+        result.append(&mut self.proposer_slashings.hash_tree_root());
+        result.append(&mut self.casper_slashings.hash_tree_root());
+        result.append(&mut self.attestations.hash_tree_root());
+        result.append(&mut self.custody_reseeds.hash_tree_root());
+        result.append(&mut self.custody_challenges.hash_tree_root());
+        result.append(&mut self.custody_responses.hash_tree_root());
+        result.append(&mut self.deposits.hash_tree_root());
+        result.append(&mut self.exits.hash_tree_root());
+        hash(&result)
+    }
+}
+
 impl<T: RngCore> TestRandom<T> for BeaconBlockBody {
     fn random_for_test(rng: &mut T) -> Self {
         Self {
@@ -92,4 +107,16 @@ mod tests {
 
         assert_eq!(original, decoded);
     }
+
+    #[test]
+    pub fn test_hash_tree_root() {
+        let mut rng = XorShiftRng::from_seed([42; 16]);
+        let original = BeaconBlockBody::random_for_test(&mut rng);
+
+        let result = original.hash_tree_root();
+
+        assert_eq!(result.len(), 32);
+        // TODO: Add further tests
+        // https://github.com/sigp/lighthouse/issues/170
+    }
 }

eth2/types/src/beacon_state/mod.rs

@@ -8,7 +8,7 @@ use super::Hash256;
 use crate::test_utils::TestRandom;
 use hashing::canonical_hash;
 use rand::RngCore;
-use ssz::{ssz_encode, Decodable, DecodeError, Encodable, SszStream};
+use ssz::{hash, ssz_encode, Decodable, DecodeError, Encodable, SszStream, TreeHash};
 
 mod slot_advance;
 
@@ -170,6 +170,41 @@ impl Decodable for BeaconState {
     }
 }
 
+impl TreeHash for BeaconState {
+    fn hash_tree_root(&self) -> Vec<u8> {
+        let mut result: Vec<u8> = vec![];
+        result.append(&mut self.slot.hash_tree_root());
+        result.append(&mut self.genesis_time.hash_tree_root());
+        result.append(&mut self.fork_data.hash_tree_root());
+        result.append(&mut self.validator_registry.hash_tree_root());
+        result.append(&mut self.validator_balances.hash_tree_root());
+        result.append(&mut self.validator_registry_update_slot.hash_tree_root());
+        result.append(&mut self.validator_registry_exit_count.hash_tree_root());
+        result.append(&mut self.validator_registry_delta_chain_tip.hash_tree_root());
+        result.append(&mut self.latest_randao_mixes.hash_tree_root());
+        result.append(&mut self.latest_vdf_outputs.hash_tree_root());
+        result.append(&mut self.previous_epoch_start_shard.hash_tree_root());
+        result.append(&mut self.current_epoch_start_shard.hash_tree_root());
+        result.append(&mut self.previous_epoch_calculation_slot.hash_tree_root());
+        result.append(&mut self.current_epoch_calculation_slot.hash_tree_root());
+        result.append(&mut self.previous_epoch_randao_mix.hash_tree_root());
+        result.append(&mut self.current_epoch_randao_mix.hash_tree_root());
+        result.append(&mut self.custody_challenges.hash_tree_root());
+        result.append(&mut self.previous_justified_slot.hash_tree_root());
+        result.append(&mut self.justified_slot.hash_tree_root());
+        result.append(&mut self.justification_bitfield.hash_tree_root());
+        result.append(&mut self.finalized_slot.hash_tree_root());
+        result.append(&mut self.latest_crosslinks.hash_tree_root());
+        result.append(&mut self.latest_block_roots.hash_tree_root());
+        result.append(&mut self.latest_penalized_exit_balances.hash_tree_root());
+        result.append(&mut self.latest_attestations.hash_tree_root());
+        result.append(&mut self.batched_block_roots.hash_tree_root());
+        result.append(&mut self.latest_eth1_data.hash_tree_root());
+        result.append(&mut self.eth1_data_votes.hash_tree_root());
+        hash(&result)
+    }
+}
+
 impl<T: RngCore> TestRandom<T> for BeaconState {
     fn random_for_test(rng: &mut T) -> Self {
         Self {
@@ -221,4 +256,16 @@ mod tests {
 
         assert_eq!(original, decoded);
     }
+
+    #[test]
+    pub fn test_hash_tree_root() {
+        let mut rng = XorShiftRng::from_seed([42; 16]);
+        let original = BeaconState::random_for_test(&mut rng);
+
+        let result = original.hash_tree_root();
+
+        assert_eq!(result.len(), 32);
+        // TODO: Add further tests
+        // https://github.com/sigp/lighthouse/issues/170
+    }
 }

eth2/types/src/casper_slashing.rs

@@ -1,7 +1,7 @@
 use super::SlashableVoteData;
 use crate::test_utils::TestRandom;
 use rand::RngCore;
-use ssz::{Decodable, DecodeError, Encodable, SszStream};
+use ssz::{hash, Decodable, DecodeError, Encodable, SszStream, TreeHash};
 
 #[derive(Debug, PartialEq, Clone)]
 pub struct CasperSlashing {
@@ -31,6 +31,15 @@ impl Decodable for CasperSlashing {
     }
 }
 
+impl TreeHash for CasperSlashing {
+    fn hash_tree_root(&self) -> Vec<u8> {
+        let mut result: Vec<u8> = vec![];
+        result.append(&mut self.slashable_vote_data_1.hash_tree_root());
+        result.append(&mut self.slashable_vote_data_2.hash_tree_root());
+        hash(&result)
+    }
+}
+
 impl<T: RngCore> TestRandom<T> for CasperSlashing {
     fn random_for_test(rng: &mut T) -> Self {
         Self {
@@ -56,4 +65,16 @@ mod tests {
 
         assert_eq!(original, decoded);
     }
+
+    #[test]
+    pub fn test_hash_tree_root() {
+        let mut rng = XorShiftRng::from_seed([42; 16]);
+        let original = CasperSlashing::random_for_test(&mut rng);
+
+        let result = original.hash_tree_root();
+
+        assert_eq!(result.len(), 32);
+        // TODO: Add further tests
+        // https://github.com/sigp/lighthouse/issues/170
+    }
 }

eth2/types/src/crosslink.rs

@@ -1,7 +1,7 @@
 use super::Hash256;
 use crate::test_utils::TestRandom;
 use rand::RngCore;
-use ssz::{Decodable, DecodeError, Encodable, SszStream};
+use ssz::{hash, Decodable, DecodeError, Encodable, SszStream, TreeHash};
 
 #[derive(Clone, Debug, PartialEq)]
 pub struct Crosslink {
@@ -41,6 +41,15 @@ impl Decodable for Crosslink {
     }
 }
 
+impl TreeHash for Crosslink {
+    fn hash_tree_root(&self) -> Vec<u8> {
+        let mut result: Vec<u8> = vec![];
+        result.append(&mut self.slot.hash_tree_root());
+        result.append(&mut self.shard_block_root.hash_tree_root());
+        hash(&result)
+    }
+}
+
 impl<T: RngCore> TestRandom<T> for Crosslink {
     fn random_for_test(rng: &mut T) -> Self {
         Self {
@@ -66,4 +75,16 @@ mod tests {
 
         assert_eq!(original, decoded);
     }
+
+    #[test]
+    pub fn test_hash_tree_root() {
+        let mut rng = XorShiftRng::from_seed([42; 16]);
+        let original = Crosslink::random_for_test(&mut rng);
+
+        let result = original.hash_tree_root();
+
+        assert_eq!(result.len(), 32);
+        // TODO: Add further tests
+        // https://github.com/sigp/lighthouse/issues/170
+    }
 }

eth2/types/src/deposit.rs

@@ -1,7 +1,7 @@
 use super::{DepositData, Hash256};
 use crate::test_utils::TestRandom;
 use rand::RngCore;
-use ssz::{Decodable, DecodeError, Encodable, SszStream};
+use ssz::{hash, Decodable, DecodeError, Encodable, SszStream, TreeHash};
 
 #[derive(Debug, PartialEq, Clone)]
 pub struct Deposit {
@@ -35,6 +35,16 @@ impl Decodable for Deposit {
     }
 }
 
+impl TreeHash for Deposit {
+    fn hash_tree_root(&self) -> Vec<u8> {
+        let mut result: Vec<u8> = vec![];
+        result.append(&mut self.merkle_branch.hash_tree_root());
+        result.append(&mut self.merkle_tree_index.hash_tree_root());
+        result.append(&mut self.deposit_data.hash_tree_root());
+        hash(&result)
+    }
+}
+
 impl<T: RngCore> TestRandom<T> for Deposit {
     fn random_for_test(rng: &mut T) -> Self {
         Self {
@@ -61,4 +71,16 @@ mod tests {
 
         assert_eq!(original, decoded);
     }
+
+    #[test]
+    pub fn test_hash_tree_root() {
+        let mut rng = XorShiftRng::from_seed([42; 16]);
+        let original = Deposit::random_for_test(&mut rng);
+
+        let result = original.hash_tree_root();
+
+        assert_eq!(result.len(), 32);
+        // TODO: Add further tests
+        // https://github.com/sigp/lighthouse/issues/170
+    }
 }

eth2/types/src/deposit_data.rs

@@ -1,7 +1,7 @@
 use super::DepositInput;
 use crate::test_utils::TestRandom;
 use rand::RngCore;
-use ssz::{Decodable, DecodeError, Encodable, SszStream};
+use ssz::{hash, Decodable, DecodeError, Encodable, SszStream, TreeHash};
 
 #[derive(Debug, PartialEq, Clone)]
 pub struct DepositData {
@@ -35,6 +35,16 @@ impl Decodable for DepositData {
     }
 }
 
+impl TreeHash for DepositData {
+    fn hash_tree_root(&self) -> Vec<u8> {
+        let mut result: Vec<u8> = vec![];
+        result.append(&mut self.amount.hash_tree_root());
+        result.append(&mut self.timestamp.hash_tree_root());
+        result.append(&mut self.deposit_input.hash_tree_root());
+        hash(&result)
+    }
+}
+
 impl<T: RngCore> TestRandom<T> for DepositData {
     fn random_for_test(rng: &mut T) -> Self {
         Self {
@@ -61,4 +71,16 @@ mod tests {
 
         assert_eq!(original, decoded);
     }
+
+    #[test]
+    pub fn test_hash_tree_root() {
+        let mut rng = XorShiftRng::from_seed([42; 16]);
+        let original = DepositData::random_for_test(&mut rng);
+
+        let result = original.hash_tree_root();
+
+        assert_eq!(result.len(), 32);
+        // TODO: Add further tests
+        // https://github.com/sigp/lighthouse/issues/170
+    }
 }

eth2/types/src/deposit_input.rs

@@ -2,7 +2,7 @@ use super::Hash256;
 use crate::test_utils::TestRandom;
 use bls::{PublicKey, Signature};
 use rand::RngCore;
-use ssz::{Decodable, DecodeError, Encodable, SszStream};
+use ssz::{hash, Decodable, DecodeError, Encodable, SszStream, TreeHash};
 
 #[derive(Debug, PartialEq, Clone)]
 pub struct DepositInput {
@@ -36,6 +36,16 @@ impl Decodable for DepositInput {
     }
 }
 
+impl TreeHash for DepositInput {
+    fn hash_tree_root(&self) -> Vec<u8> {
+        let mut result: Vec<u8> = vec![];
+        result.append(&mut self.pubkey.hash_tree_root());
+        result.append(&mut self.withdrawal_credentials.hash_tree_root());
+        result.append(&mut self.proof_of_possession.hash_tree_root());
+        hash(&result)
+    }
+}
+
 impl<T: RngCore> TestRandom<T> for DepositInput {
     fn random_for_test(rng: &mut T) -> Self {
         Self {
@@ -62,4 +72,16 @@ mod tests {
 
         assert_eq!(original, decoded);
     }
+
+    #[test]
+    pub fn test_hash_tree_root() {
+        let mut rng = XorShiftRng::from_seed([42; 16]);
+        let original = DepositInput::random_for_test(&mut rng);
+
+        let result = original.hash_tree_root();
+
+        assert_eq!(result.len(), 32);
+        // TODO: Add further tests
+        // https://github.com/sigp/lighthouse/issues/170
+    }
 }

eth2/types/src/eth1_data.rs

@@ -1,7 +1,7 @@
 use super::Hash256;
 use crate::test_utils::TestRandom;
 use rand::RngCore;
-use ssz::{Decodable, DecodeError, Encodable, SszStream};
+use ssz::{hash, Decodable, DecodeError, Encodable, SszStream, TreeHash};
 
 // Note: this is refer to as DepositRootVote in specs
 #[derive(Debug, PartialEq, Clone, Default)]
@@ -32,6 +32,15 @@ impl Decodable for Eth1Data {
     }
 }
 
+impl TreeHash for Eth1Data {
+    fn hash_tree_root(&self) -> Vec<u8> {
+        let mut result: Vec<u8> = vec![];
+        result.append(&mut self.deposit_root.hash_tree_root());
+        result.append(&mut self.block_hash.hash_tree_root());
+        hash(&result)
+    }
+}
+
 impl<T: RngCore> TestRandom<T> for Eth1Data {
     fn random_for_test(rng: &mut T) -> Self {
         Self {
@@ -57,4 +66,16 @@ mod tests {
 
         assert_eq!(original, decoded);
     }
+
+    #[test]
+    pub fn test_hash_tree_root() {
+        let mut rng = XorShiftRng::from_seed([42; 16]);
+        let original = Eth1Data::random_for_test(&mut rng);
+
+        let result = original.hash_tree_root();
+
+        assert_eq!(result.len(), 32);
+        // TODO: Add further tests
+        // https://github.com/sigp/lighthouse/issues/170
+    }
 }

eth2/types/src/eth1_data_vote.rs

@@ -1,7 +1,7 @@
 use super::Eth1Data;
 use crate::test_utils::TestRandom;
 use rand::RngCore;
-use ssz::{Decodable, DecodeError, Encodable, SszStream};
+use ssz::{hash, Decodable, DecodeError, Encodable, SszStream, TreeHash};
 
 // Note: this is refer to as DepositRootVote in specs
 #[derive(Debug, PartialEq, Clone, Default)]
@@ -32,6 +32,15 @@ impl Decodable for Eth1DataVote {
     }
 }
 
+impl TreeHash for Eth1DataVote {
+    fn hash_tree_root(&self) -> Vec<u8> {
+        let mut result: Vec<u8> = vec![];
+        result.append(&mut self.eth1_data.hash_tree_root());
+        result.append(&mut self.vote_count.hash_tree_root());
+        hash(&result)
+    }
+}
+
 impl<T: RngCore> TestRandom<T> for Eth1DataVote {
     fn random_for_test(rng: &mut T) -> Self {
         Self {
@@ -57,4 +66,16 @@ mod tests {
 
         assert_eq!(original, decoded);
     }
+
+    #[test]
+    pub fn test_hash_tree_root() {
+        let mut rng = XorShiftRng::from_seed([42; 16]);
+        let original = Eth1DataVote::random_for_test(&mut rng);
+
+        let result = original.hash_tree_root();
+
+        assert_eq!(result.len(), 32);
+        // TODO: Add further tests
+        // https://github.com/sigp/lighthouse/issues/170
+    }
 }

eth2/types/src/exit.rs

@@ -1,7 +1,7 @@
 use crate::test_utils::TestRandom;
 use bls::Signature;
 use rand::RngCore;
-use ssz::{Decodable, DecodeError, Encodable, SszStream};
+use ssz::{hash, Decodable, DecodeError, Encodable, SszStream, TreeHash};
 
 #[derive(Debug, PartialEq, Clone)]
 pub struct Exit {
@@ -35,6 +35,16 @@ impl Decodable for Exit {
     }
 }
 
+impl TreeHash for Exit {
+    fn hash_tree_root(&self) -> Vec<u8> {
+        let mut result: Vec<u8> = vec![];
+        result.append(&mut self.slot.hash_tree_root());
+        result.append(&mut self.validator_index.hash_tree_root());
+        result.append(&mut self.signature.hash_tree_root());
+        hash(&result)
+    }
+}
+
 impl<T: RngCore> TestRandom<T> for Exit {
     fn random_for_test(rng: &mut T) -> Self {
         Self {
@@ -61,4 +71,16 @@ mod tests {
 
         assert_eq!(original, decoded);
     }
+
+    #[test]
+    pub fn test_hash_tree_root() {
+        let mut rng = XorShiftRng::from_seed([42; 16]);
+        let original = Exit::random_for_test(&mut rng);
+
+        let result = original.hash_tree_root();
+
+        assert_eq!(result.len(), 32);
+        // TODO: Add further tests
+        // https://github.com/sigp/lighthouse/issues/170
+    }
 }

eth2/types/src/fork.rs

@@ -1,6 +1,6 @@
 use crate::test_utils::TestRandom;
 use rand::RngCore;
-use ssz::{Decodable, DecodeError, Encodable, SszStream};
+use ssz::{hash, Decodable, DecodeError, Encodable, SszStream, TreeHash};
 
 #[derive(Debug, Clone, PartialEq, Default)]
 pub struct Fork {
@@ -34,6 +34,16 @@ impl Decodable for Fork {
     }
 }
 
+impl TreeHash for Fork {
+    fn hash_tree_root(&self) -> Vec<u8> {
+        let mut result: Vec<u8> = vec![];
+        result.append(&mut self.pre_fork_version.hash_tree_root());
+        result.append(&mut self.post_fork_version.hash_tree_root());
+        result.append(&mut self.fork_slot.hash_tree_root());
+        hash(&result)
+    }
+}
+
 impl<T: RngCore> TestRandom<T> for Fork {
     fn random_for_test(rng: &mut T) -> Self {
         Self {
@@ -60,4 +70,16 @@ mod tests {
 
         assert_eq!(original, decoded);
     }
+
+    #[test]
+    pub fn test_hash_tree_root() {
+        let mut rng = XorShiftRng::from_seed([42; 16]);
+        let original = Fork::random_for_test(&mut rng);
+
+        let result = original.hash_tree_root();
+
+        assert_eq!(result.len(), 32);
+        // TODO: Add further tests
+        // https://github.com/sigp/lighthouse/issues/170
+    }
 }

eth2/types/src/pending_attestation.rs

@@ -1,7 +1,7 @@
 use super::{AttestationData, Bitfield};
 use crate::test_utils::TestRandom;
 use rand::RngCore;
-use ssz::{Decodable, DecodeError, Encodable, SszStream};
+use ssz::{hash, Decodable, DecodeError, Encodable, SszStream, TreeHash};
 
 #[derive(Debug, Clone, PartialEq)]
 pub struct PendingAttestation {
@@ -39,6 +39,17 @@ impl Decodable for PendingAttestation {
     }
 }
 
+impl TreeHash for PendingAttestation {
+    fn hash_tree_root(&self) -> Vec<u8> {
+        let mut result: Vec<u8> = vec![];
+        result.append(&mut self.data.hash_tree_root());
+        result.append(&mut self.aggregation_bitfield.hash_tree_root());
+        result.append(&mut self.custody_bitfield.hash_tree_root());
+        result.append(&mut self.custody_bitfield.hash_tree_root());
+        hash(&result)
+    }
+}
+
 impl<T: RngCore> TestRandom<T> for PendingAttestation {
     fn random_for_test(rng: &mut T) -> Self {
         Self {
@@ -66,4 +77,16 @@ mod tests {
 
         assert_eq!(original, decoded);
     }
+
+    #[test]
+    pub fn test_hash_tree_root() {
+        let mut rng = XorShiftRng::from_seed([42; 16]);
+        let original = PendingAttestation::random_for_test(&mut rng);
+
+        let result = original.hash_tree_root();
+
+        assert_eq!(result.len(), 32);
+        // TODO: Add further tests
+        // https://github.com/sigp/lighthouse/issues/170
+    }
 }

eth2/types/src/proposal_signed_data.rs

@@ -1,7 +1,7 @@
 use super::Hash256;
 use crate::test_utils::TestRandom;
 use rand::RngCore;
-use ssz::{Decodable, DecodeError, Encodable, SszStream};
+use ssz::{hash, Decodable, DecodeError, Encodable, SszStream, TreeHash};
 
 #[derive(Debug, PartialEq, Clone, Default)]
 pub struct ProposalSignedData {
@@ -35,6 +35,16 @@ impl Decodable for ProposalSignedData {
     }
 }
 
+impl TreeHash for ProposalSignedData {
+    fn hash_tree_root(&self) -> Vec<u8> {
+        let mut result: Vec<u8> = vec![];
+        result.append(&mut self.slot.hash_tree_root());
+        result.append(&mut self.shard.hash_tree_root());
+        result.append(&mut self.block_root.hash_tree_root());
+        hash(&result)
+    }
+}
+
 impl<T: RngCore> TestRandom<T> for ProposalSignedData {
     fn random_for_test(rng: &mut T) -> Self {
         Self {
@@ -61,4 +71,16 @@ mod tests {
 
         assert_eq!(original, decoded);
     }
+
+    #[test]
+    pub fn test_hash_tree_root() {
+        let mut rng = XorShiftRng::from_seed([42; 16]);
+        let original = ProposalSignedData::random_for_test(&mut rng);
+
+        let result = original.hash_tree_root();
+
+        assert_eq!(result.len(), 32);
+        // TODO: Add further tests
+        // https://github.com/sigp/lighthouse/issues/170
+    }
 }

eth2/types/src/proposer_slashing.rs

@@ -2,7 +2,7 @@ use super::ProposalSignedData;
 use crate::test_utils::TestRandom;
 use bls::Signature;
 use rand::RngCore;
-use ssz::{Decodable, DecodeError, Encodable, SszStream};
+use ssz::{hash, Decodable, DecodeError, Encodable, SszStream, TreeHash};
 
 #[derive(Debug, PartialEq, Clone)]
 pub struct ProposerSlashing {
@@ -44,6 +44,18 @@ impl Decodable for ProposerSlashing {
     }
 }
 
+impl TreeHash for ProposerSlashing {
+    fn hash_tree_root(&self) -> Vec<u8> {
+        let mut result: Vec<u8> = vec![];
+        result.append(&mut self.proposer_index.hash_tree_root());
+        result.append(&mut self.proposal_data_1.hash_tree_root());
+        result.append(&mut self.proposal_signature_1.hash_tree_root());
+        result.append(&mut self.proposal_data_2.hash_tree_root());
+        result.append(&mut self.proposal_signature_2.hash_tree_root());
+        hash(&result)
+    }
+}
+
 impl<T: RngCore> TestRandom<T> for ProposerSlashing {
     fn random_for_test(rng: &mut T) -> Self {
         Self {
@@ -72,4 +84,16 @@ mod tests {
 
         assert_eq!(original, decoded);
     }
+
+    #[test]
+    pub fn test_hash_tree_root() {
+        let mut rng = XorShiftRng::from_seed([42; 16]);
+        let original = ProposerSlashing::random_for_test(&mut rng);
+
+        let result = original.hash_tree_root();
+
+        assert_eq!(result.len(), 32);
+        // TODO: Add further tests
+        // https://github.com/sigp/lighthouse/issues/170
+    }
 }

eth2/types/src/shard_committee.rs

@@ -1,6 +1,6 @@
 use crate::test_utils::TestRandom;
 use rand::RngCore;
-use ssz::{Decodable, DecodeError, Encodable, SszStream};
+use ssz::{hash, Decodable, DecodeError, Encodable, SszStream, TreeHash};
 
 #[derive(Clone, Debug, PartialEq)]
 pub struct ShardCommittee {
@@ -24,6 +24,15 @@ impl Decodable for ShardCommittee {
     }
 }
 
+impl TreeHash for ShardCommittee {
+    fn hash_tree_root(&self) -> Vec<u8> {
+        let mut result: Vec<u8> = vec![];
+        result.append(&mut self.shard.hash_tree_root());
+        result.append(&mut self.committee.hash_tree_root());
+        hash(&result)
+    }
+}
+
 impl<T: RngCore> TestRandom<T> for ShardCommittee {
     fn random_for_test(rng: &mut T) -> Self {
         Self {
@@ -49,4 +58,16 @@ mod tests {
 
         assert_eq!(original, decoded);
     }
+
+    #[test]
+    pub fn test_hash_tree_root() {
+        let mut rng = XorShiftRng::from_seed([42; 16]);
+        let original = ShardCommittee::random_for_test(&mut rng);
+
+        let result = original.hash_tree_root();
+
+        assert_eq!(result.len(), 32);
+        // TODO: Add further tests
+        // https://github.com/sigp/lighthouse/issues/170
+    }
 }

eth2/types/src/shard_reassignment_record.rs

@@ -1,6 +1,6 @@
 use crate::test_utils::TestRandom;
 use rand::RngCore;
-use ssz::{Decodable, DecodeError, Encodable, SszStream};
+use ssz::{hash, Decodable, DecodeError, Encodable, SszStream, TreeHash};
 
 #[derive(Debug, PartialEq, Clone)]
 pub struct ShardReassignmentRecord {
@@ -34,6 +34,16 @@ impl Decodable for ShardReassignmentRecord {
     }
 }
 
+impl TreeHash for ShardReassignmentRecord {
+    fn hash_tree_root(&self) -> Vec<u8> {
+        let mut result: Vec<u8> = vec![];
+        result.append(&mut self.validator_index.hash_tree_root());
+        result.append(&mut self.shard.hash_tree_root());
+        result.append(&mut self.slot.hash_tree_root());
+        hash(&result)
+    }
+}
+
 impl<T: RngCore> TestRandom<T> for ShardReassignmentRecord {
     fn random_for_test(rng: &mut T) -> Self {
         Self {
@@ -60,4 +70,16 @@ mod tests {
 
         assert_eq!(original, decoded);
     }
+
+    #[test]
+    pub fn test_hash_tree_root() {
+        let mut rng = XorShiftRng::from_seed([42; 16]);
+        let original = ShardReassignmentRecord::random_for_test(&mut rng);
+
+        let result = original.hash_tree_root();
+
+        assert_eq!(result.len(), 32);
+        // TODO: Add further tests
+        // https://github.com/sigp/lighthouse/issues/170
+    }
 }

eth2/types/src/slashable_vote_data.rs

@@ -2,7 +2,7 @@ use super::AttestationData;
 use crate::test_utils::TestRandom;
 use bls::AggregateSignature;
 use rand::RngCore;
-use ssz::{Decodable, DecodeError, Encodable, SszStream};
+use ssz::{hash, Decodable, DecodeError, Encodable, SszStream, TreeHash};
 
 #[derive(Debug, PartialEq, Clone)]
 pub struct SlashableVoteData {
@@ -40,6 +40,17 @@ impl Decodable for SlashableVoteData {
     }
 }
 
+impl TreeHash for SlashableVoteData {
+    fn hash_tree_root(&self) -> Vec<u8> {
+        let mut result: Vec<u8> = vec![];
+        result.append(&mut self.custody_bit_0_indices.hash_tree_root());
+        result.append(&mut self.custody_bit_1_indices.hash_tree_root());
+        result.append(&mut self.data.hash_tree_root());
+        result.append(&mut self.aggregate_signature.hash_tree_root());
+        hash(&result)
+    }
+}
+
 impl<T: RngCore> TestRandom<T> for SlashableVoteData {
     fn random_for_test(rng: &mut T) -> Self {
         Self {
@@ -67,4 +78,16 @@ mod tests {
 
         assert_eq!(original, decoded);
     }
+
+    #[test]
+    pub fn test_hash_tree_root() {
+        let mut rng = XorShiftRng::from_seed([42; 16]);
+        let original = SlashableVoteData::random_for_test(&mut rng);
+
+        let result = original.hash_tree_root();
+
+        assert_eq!(result.len(), 32);
+        // TODO: Add further tests
+        // https://github.com/sigp/lighthouse/issues/170
+    }
 }

eth2/types/src/special_record.rs

@@ -1,4 +1,4 @@
-use ssz::{Decodable, DecodeError, Encodable, SszStream};
+use ssz::{hash, Decodable, DecodeError, Encodable, SszStream, TreeHash};
 
 /// The value of the "type" field of SpecialRecord.
 ///
@@ -71,6 +71,15 @@ impl Decodable for SpecialRecord {
     }
 }
 
+impl TreeHash for SpecialRecord {
+    fn hash_tree_root(&self) -> Vec<u8> {
+        let mut result: Vec<u8> = vec![];
+        result.append(&mut self.kind.hash_tree_root());
+        result.append(&mut self.data.as_slice().hash_tree_root());
+        hash(&result)
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;

eth2/types/src/validator.rs

@@ -2,7 +2,7 @@ use super::Hash256;
 use crate::test_utils::TestRandom;
 use bls::PublicKey;
 use rand::RngCore;
-use ssz::{Decodable, DecodeError, Encodable, SszStream};
+use ssz::{hash, Decodable, DecodeError, Encodable, SszStream, TreeHash};
 
 const STATUS_FLAG_INITIATED_EXIT: u8 = 1;
 const STATUS_FLAG_WITHDRAWABLE: u8 = 2;
@@ -142,6 +142,24 @@ impl Decodable for Validator {
     }
 }
 
+impl TreeHash for Validator {
+    fn hash_tree_root(&self) -> Vec<u8> {
+        let mut result: Vec<u8> = vec![];
+        result.append(&mut self.pubkey.hash_tree_root());
+        result.append(&mut self.withdrawal_credentials.hash_tree_root());
+        result.append(&mut self.proposer_slots.hash_tree_root());
+        result.append(&mut self.activation_slot.hash_tree_root());
+        result.append(&mut self.exit_slot.hash_tree_root());
+        result.append(&mut self.withdrawal_slot.hash_tree_root());
+        result.append(&mut self.penalized_slot.hash_tree_root());
+        result.append(&mut self.exit_count.hash_tree_root());
+        result.append(&mut (status_flag_to_byte(self.status_flags) as u64).hash_tree_root());
+        result.append(&mut self.latest_custody_reseed_slot.hash_tree_root());
+        result.append(&mut self.penultimate_custody_reseed_slot.hash_tree_root());
+        hash(&result)
+    }
+}
+
 impl<T: RngCore> TestRandom<T> for Validator {
     fn random_for_test(rng: &mut T) -> Self {
         Self {
@@ -198,4 +216,16 @@ mod tests {
             }
         }
     }
+
+    #[test]
+    pub fn test_hash_tree_root() {
+        let mut rng = XorShiftRng::from_seed([42; 16]);
+        let original = Validator::random_for_test(&mut rng);
+
+        let result = original.hash_tree_root();
+
+        assert_eq!(result.len(), 32);
+        // TODO: Add further tests
+        // https://github.com/sigp/lighthouse/issues/170
+    }
 }

eth2/types/src/validator_registry_delta_block.rs

@@ -2,7 +2,7 @@ use super::Hash256;
 use crate::test_utils::TestRandom;
 use bls::PublicKey;
 use rand::RngCore;
-use ssz::{Decodable, DecodeError, Encodable, SszStream};
+use ssz::{hash, Decodable, DecodeError, Encodable, SszStream, TreeHash};
 
 // The information gathered from the PoW chain validator registration function.
 #[derive(Debug, Clone, PartialEq)]
@@ -58,6 +58,18 @@ impl Decodable for ValidatorRegistryDeltaBlock {
     }
 }
 
+impl TreeHash for ValidatorRegistryDeltaBlock {
+    fn hash_tree_root(&self) -> Vec<u8> {
+        let mut result: Vec<u8> = vec![];
+        result.append(&mut self.latest_registry_delta_root.hash_tree_root());
+        result.append(&mut self.validator_index.hash_tree_root());
+        result.append(&mut self.pubkey.hash_tree_root());
+        result.append(&mut self.slot.hash_tree_root());
+        result.append(&mut self.flag.hash_tree_root());
+        hash(&result)
+    }
+}
+
 impl<T: RngCore> TestRandom<T> for ValidatorRegistryDeltaBlock {
     fn random_for_test(rng: &mut T) -> Self {
         Self {
@@ -86,4 +98,16 @@ mod tests {
 
         assert_eq!(original, decoded);
     }
+
+    #[test]
+    pub fn test_hash_tree_root() {
+        let mut rng = XorShiftRng::from_seed([42; 16]);
+        let original = ValidatorRegistryDeltaBlock::random_for_test(&mut rng);
+
+        let result = original.hash_tree_root();
+
+        assert_eq!(result.len(), 32);
+        // TODO: Add further tests
+        // https://github.com/sigp/lighthouse/issues/170
+    }
 }

eth2/utils/bls/src/aggregate_signature.rs

@@ -1,6 +1,6 @@
 use super::{AggregatePublicKey, Signature};
 use bls_aggregates::AggregateSignature as RawAggregateSignature;
-use ssz::{decode_ssz_list, Decodable, DecodeError, Encodable, SszStream};
+use ssz::{decode_ssz_list, hash, Decodable, DecodeError, Encodable, SszStream, TreeHash};
 
 /// A BLS aggregate signature.
 ///
@@ -44,6 +44,12 @@ impl Decodable for AggregateSignature {
     }
 }
 
+impl TreeHash for AggregateSignature {
+    fn hash_tree_root(&self) -> Vec<u8> {
+        hash(&self.0.as_bytes())
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::super::{Keypair, Signature};

eth2/utils/bls/src/public_key.rs

@@ -1,7 +1,9 @@
 use super::SecretKey;
 use bls_aggregates::PublicKey as RawPublicKey;
 use hex::encode as hex_encode;
-use ssz::{decode_ssz_list, ssz_encode, Decodable, DecodeError, Encodable, SszStream};
+use ssz::{
+    decode_ssz_list, hash, ssz_encode, Decodable, DecodeError, Encodable, SszStream, TreeHash,
+};
 use std::default;
 use std::hash::{Hash, Hasher};
 
@@ -53,6 +55,12 @@ impl Decodable for PublicKey {
     }
 }
 
+impl TreeHash for PublicKey {
+    fn hash_tree_root(&self) -> Vec<u8> {
+        hash(&self.0.as_bytes())
+    }
+}
+
 impl PartialEq for PublicKey {
     fn eq(&self, other: &PublicKey) -> bool {
         ssz_encode(self) == ssz_encode(other)

eth2/utils/bls/src/secret_key.rs

@@ -1,5 +1,5 @@
 use bls_aggregates::{DecodeError as BlsDecodeError, SecretKey as RawSecretKey};
-use ssz::{decode_ssz_list, Decodable, DecodeError, Encodable, SszStream};
+use ssz::{decode_ssz_list, Decodable, DecodeError, Encodable, SszStream, TreeHash};
 
 /// A single BLS signature.
 ///
@@ -40,6 +40,12 @@ impl Decodable for SecretKey {
     }
 }
 
+impl TreeHash for SecretKey {
+    fn hash_tree_root(&self) -> Vec<u8> {
+        self.0.as_bytes().clone()
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;

eth2/utils/bls/src/signature.rs

@@ -1,6 +1,6 @@
 use super::{PublicKey, SecretKey};
 use bls_aggregates::Signature as RawSignature;
-use ssz::{decode_ssz_list, Decodable, DecodeError, Encodable, SszStream};
+use ssz::{decode_ssz_list, hash, Decodable, DecodeError, Encodable, SszStream, TreeHash};
 
 /// A single BLS signature.
 ///
@@ -57,6 +57,12 @@ impl Decodable for Signature {
     }
 }
 
+impl TreeHash for Signature {
+    fn hash_tree_root(&self) -> Vec<u8> {
+        hash(&self.0.as_bytes())
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::super::Keypair;

eth2/utils/boolean-bitfield/src/lib.rs

@@ -149,6 +149,12 @@ impl ssz::Decodable for BooleanBitfield {
     }
 }
 
+impl ssz::TreeHash for BooleanBitfield {
+    fn hash_tree_root(&self) -> Vec<u8> {
+        self.to_bytes().hash_tree_root()
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;

eth2/utils/hashing/Cargo.toml

@@ -6,4 +6,3 @@ edition = "2018"
 
 [dependencies]
 tiny-keccak = "1.4.2"
-ssz = { path = "../ssz" }

eth2/utils/hashing/src/lib.rs

@@ -1,4 +1,3 @@
-use ssz::{ssz_encode, Encodable as SszEncodable};
 use tiny_keccak::Keccak;
 
 pub fn canonical_hash(input: &[u8]) -> Vec<u8> {
@@ -9,10 +8,6 @@ pub fn canonical_hash(input: &[u8]) -> Vec<u8> {
     result
 }
 
-pub fn hash_tree_root<T: SszEncodable>(input: &T) -> Vec<u8> {
-    canonical_hash(&ssz_encode(input))
-}
-
 #[cfg(test)]
 mod tests {
     use super::*;

eth2/utils/ssz/Cargo.toml

@@ -7,3 +7,4 @@ edition = "2018"
 [dependencies]
 bytes = "0.4.9"
 ethereum-types = "0.4.0"
+hashing = { path = "../hashing" }

eth2/utils/ssz/src/impl_encode.rs

@@ -79,6 +79,14 @@ mod tests {
         assert_eq!(ssz.drain(), vec![0; 32]);
     }
 
+    #[test]
+    fn test_ssz_encode_address() {
+        let h = Address::zero();
+        let mut ssz = SszStream::new();
+        ssz.append(&h);
+        assert_eq!(ssz.drain(), vec![0; 20]);
+    }
+
     #[test]
     fn test_ssz_encode_u8() {
         let x: u8 = 0;

eth2/utils/ssz/src/impl_tree_hash.rs

@@ -0,0 +1,78 @@
+use super::ethereum_types::{Address, H256};
+use super::{hash, merkle_hash, ssz_encode, TreeHash};
+
+impl TreeHash for u8 {
+    fn hash_tree_root(&self) -> Vec<u8> {
+        ssz_encode(self)
+    }
+}
+
+impl TreeHash for u16 {
+    fn hash_tree_root(&self) -> Vec<u8> {
+        ssz_encode(self)
+    }
+}
+
+impl TreeHash for u32 {
+    fn hash_tree_root(&self) -> Vec<u8> {
+        ssz_encode(self)
+    }
+}
+
+impl TreeHash for u64 {
+    fn hash_tree_root(&self) -> Vec<u8> {
+        ssz_encode(self)
+    }
+}
+
+impl TreeHash for usize {
+    fn hash_tree_root(&self) -> Vec<u8> {
+        ssz_encode(self)
+    }
+}
+
+impl TreeHash for Address {
+    fn hash_tree_root(&self) -> Vec<u8> {
+        ssz_encode(self)
+    }
+}
+
+impl TreeHash for H256 {
+    fn hash_tree_root(&self) -> Vec<u8> {
+        ssz_encode(self)
+    }
+}
+
+impl TreeHash for [u8] {
+    fn hash_tree_root(&self) -> Vec<u8> {
+        if self.len() > 32 {
+            return hash(&self);
+        }
+        self.to_vec()
+    }
+}
+
+impl<T> TreeHash for Vec<T>
+where
+    T: TreeHash,
+{
+    /// Returns the merkle_hash of a list of hash_tree_root values created
+    /// from the given list.
+    /// Note: A byte vector, Vec<u8>, must be converted to a slice (as_slice())
+    ///       to be handled properly (i.e. hashed) as byte array.
+    fn hash_tree_root(&self) -> Vec<u8> {
+        let mut tree_hashes = self.iter().map(|x| x.hash_tree_root()).collect();
+        merkle_hash(&mut tree_hashes)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_impl_tree_hash_vec() {
+        let result = vec![1u32, 2, 3, 4, 5, 6, 7].hash_tree_root();
+        assert_eq!(result.len(), 32);
+    }
+}

eth2/utils/ssz/src/lib.rs

@@ -12,12 +12,15 @@ extern crate ethereum_types;
 
 pub mod decode;
 pub mod encode;
+pub mod tree_hash;
 
 mod impl_decode;
 mod impl_encode;
+mod impl_tree_hash;
 
 pub use crate::decode::{decode_ssz, decode_ssz_list, Decodable, DecodeError};
 pub use crate::encode::{Encodable, SszStream};
+pub use crate::tree_hash::{hash, merkle_hash, TreeHash};
 
 pub const LENGTH_BYTES: usize = 4;
 pub const MAX_LIST_SIZE: usize = 1 << (4 * 8);

eth2/utils/ssz/src/tree_hash.rs

@@ -0,0 +1,86 @@
+use hashing::canonical_hash;
+
+const SSZ_CHUNK_SIZE: usize = 128;
+const HASHSIZE: usize = 32;
+
+pub trait TreeHash {
+    fn hash_tree_root(&self) -> Vec<u8>;
+}
+
+/// Returns a 32 byte hash of 'list' - a vector of byte vectors.
+/// Note that this will consume 'list'.
+pub fn merkle_hash(list: &mut Vec<Vec<u8>>) -> Vec<u8> {
+    // flatten list
+    let (mut chunk_size, mut chunkz) = list_to_blob(list);
+
+    // get data_len as bytes. It will hashed will the merkle root
+    let datalen = list.len().to_le_bytes();
+
+    // Tree-hash
+    while chunkz.len() > HASHSIZE {
+        let mut new_chunkz: Vec<u8> = Vec::new();
+
+        for two_chunks in chunkz.chunks(chunk_size * 2) {
+            if two_chunks.len() == chunk_size {
+                // Odd number of chunks
+                let mut c = two_chunks.to_vec();
+                c.append(&mut vec![0; SSZ_CHUNK_SIZE]);
+                new_chunkz.append(&mut hash(&c));
+            } else {
+                // Hash two chuncks together
+                new_chunkz.append(&mut hash(two_chunks));
+            }
+            chunk_size = HASHSIZE;
+        }
+        chunkz = new_chunkz;
+    }
+
+    chunkz.append(&mut datalen.to_vec());
+    hash(&chunkz)
+}
+
+fn list_to_blob(list: &mut Vec<Vec<u8>>) -> (usize, Vec<u8>) {
+    let chunk_size = if list.is_empty() {
+        SSZ_CHUNK_SIZE
+    } else if list[0].len() < SSZ_CHUNK_SIZE {
+        let items_per_chunk = SSZ_CHUNK_SIZE / list[0].len();
+        items_per_chunk * list[0].len()
+    } else {
+        list[0].len()
+    };
+
+    let mut data = Vec::new();
+    if list.is_empty() {
+        // handle and empty list
+        data.append(&mut vec![0; SSZ_CHUNK_SIZE]);
+    } else {
+        // just create a blob here; we'll divide into
+        // chunked slices when we merklize
+        data.reserve(list[0].len() * list.len());
+        for item in list.iter_mut() {
+            data.append(item);
+        }
+    }
+    (chunk_size, data)
+}
+
+pub fn hash(data: &[u8]) -> Vec<u8> {
+    canonical_hash(data)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_merkle_hash() {
+        let data1 = vec![1; 100];
+        let data2 = vec![2; 100];
+        let data3 = vec![3; 100];
+        let mut list = vec![data1, data2, data3];
+        let result = merkle_hash(&mut list);
+
+        //note: should test againt a known test hash value
+        assert_eq!(HASHSIZE, result.len());
+    }
+}