Add SszEx.hash function

lib/lambda_ethereum_consensus/state_transition/accessors.ex

@@ -3,6 +3,7 @@ defmodule LambdaEthereumConsensus.StateTransition.Accessors do
   Functions accessing the current `BeaconState`
   """
 
+  alias LambdaEthereumConsensus.SszEx
   alias LambdaEthereumConsensus.StateTransition.{Math, Misc, Predicates}
   alias SszTypes.{Attestation, BeaconState, IndexedAttestation, SyncCommittee, Validator}
 
@@ -86,7 +87,7 @@ defmodule LambdaEthereumConsensus.StateTransition.Accessors do
       candidate_index = active_validator_indices |> Enum.fetch!(shuffled_index)
 
       <<_::binary-size(rem(index, 32)), random_byte, _::binary>> =
-        :crypto.hash(:sha256, seed <> Misc.uint64_to_bytes(div(index, 32)))
+        SszEx.hash(seed <> Misc.uint64_to_bytes(div(index, 32)))
 
       effective_balance = Enum.fetch!(validators, candidate_index).effective_balance
 
@@ -240,7 +241,7 @@ defmodule LambdaEthereumConsensus.StateTransition.Accessors do
 
     state
     |> get_seed(epoch, Constants.domain_beacon_proposer())
-    |> then(&:crypto.hash(:sha256, &1 <> Misc.uint64_to_bytes(state.slot)))
+    |> then(&SszEx.hash(&1 <> Misc.uint64_to_bytes(state.slot)))
     |> then(&Misc.compute_proposer_index(state, indices, &1))
   end
 
@@ -410,7 +411,7 @@ defmodule LambdaEthereumConsensus.StateTransition.Accessors do
           ChainSpec.get("MIN_SEED_LOOKAHEAD") - 1
       )
 
-    :crypto.hash(:sha256, domain_type <> Misc.uint64_to_bytes(epoch) <> mix)
+    SszEx.hash(domain_type <> Misc.uint64_to_bytes(epoch) <> mix)
   end
 
   @doc """

lib/lambda_ethereum_consensus/state_transition/misc.ex

@@ -3,6 +3,7 @@ defmodule LambdaEthereumConsensus.StateTransition.Misc do
   Misc functions
   """
 
+  alias LambdaEthereumConsensus.SszEx
   alias SszTypes.BeaconState
   import Bitwise
   alias SszTypes.BeaconState
@@ -55,7 +56,7 @@ defmodule LambdaEthereumConsensus.StateTransition.Misc do
       Enum.reduce(0..(shuffle_round_count - 1), index, fn round, current_index ->
         round_as_bytes = <<round>>
 
-        hash_of_seed_round = :crypto.hash(:sha256, seed <> round_as_bytes)
+        hash_of_seed_round = SszEx.hash(seed <> round_as_bytes)
 
         pivot = rem(bytes_to_uint64(hash_of_seed_round), index_count)
 
@@ -65,7 +66,7 @@ defmodule LambdaEthereumConsensus.StateTransition.Misc do
         position_div_256 = uint_to_bytes4(div(position, 256))
 
         source =
-          :crypto.hash(:sha256, seed <> round_as_bytes <> position_div_256)
+          SszEx.hash(seed <> round_as_bytes <> position_div_256)
 
         byte_index = div(rem(position, 256), 8)
         <<_::binary-size(byte_index), byte, _::binary>> = source
@@ -146,7 +147,7 @@ defmodule LambdaEthereumConsensus.StateTransition.Misc do
     total = length(indices)
     {:ok, i} = compute_shuffled_index(rem(i, total), total, seed)
     candidate_index = Enum.at(indices, i)
-    random_byte = :crypto.hash(:sha256, seed <> uint_to_bytes4(div(i, 32)))
+    random_byte = SszEx.hash(seed <> uint_to_bytes4(div(i, 32)))
     <<_::binary-size(rem(i, 32)), byte, _::binary>> = random_byte
 
     effective_balance = Enum.at(state.validators, candidate_index).effective_balance

lib/lambda_ethereum_consensus/state_transition/operations.ex

@@ -3,6 +3,7 @@ defmodule LambdaEthereumConsensus.StateTransition.Operations do
   This module contains functions for handling state transition
   """
 
+  alias LambdaEthereumConsensus.SszEx
   alias LambdaEthereumConsensus.StateTransition.{Accessors, Math, Misc, Mutators, Predicates}
   alias LambdaEthereumConsensus.Utils.BitVector
 
@@ -782,7 +783,7 @@ defmodule LambdaEthereumConsensus.StateTransition.Operations do
 
       if Bls.valid?(proposer.pubkey, signing_root, randao_reveal) do
         randao_mix = Accessors.get_randao_mix(state, epoch)
-        hash = :crypto.hash(:sha256, randao_reveal)
+        hash = SszEx.hash(randao_reveal)
 
         # Mix in RANDAO reveal
         mix = :crypto.exor(randao_mix, hash)
@@ -963,7 +964,7 @@ defmodule LambdaEthereumConsensus.StateTransition.Operations do
 
   defp validate_withdrawal_credentials(validator, address_change) do
     <<prefix::binary-size(1), address::binary-size(31)>> = validator.withdrawal_credentials
-    <<_, hash::binary-size(31)>> = :crypto.hash(:sha256, address_change.from_bls_pubkey)
+    <<_, hash::binary-size(31)>> = SszEx.hash(address_change.from_bls_pubkey)
 
     if prefix == Constants.bls_withdrawal_prefix() and address == hash do
       {:ok}

lib/lambda_ethereum_consensus/state_transition/predicates.ex

@@ -3,6 +3,7 @@ defmodule LambdaEthereumConsensus.StateTransition.Predicates do
   Range of predicates enabling verification of state
   """
 
+  alias LambdaEthereumConsensus.SszEx
   alias LambdaEthereumConsensus.StateTransition.{Accessors, Misc}
   alias SszTypes.BeaconState
   alias SszTypes.Validator
@@ -131,9 +132,9 @@ defmodule LambdaEthereumConsensus.StateTransition.Predicates do
 
   defp hash_merkle_node(value_1, value_2, index, i) do
     if rem(div(index, 2 ** i), 2) == 1 do
-      :crypto.hash(:sha256, value_1 <> value_2)
+      SszEx.hash(value_1 <> value_2)
     else
-      :crypto.hash(:sha256, value_2 <> value_1)
+      SszEx.hash(value_2 <> value_1)
     end
   end
 

lib/ssz_ex.ex

@@ -2,9 +2,14 @@ defmodule LambdaEthereumConsensus.SszEx do
   @moduledoc """
     SSZ library in Elixir
   """
+
   #################
   ### Public API
   #################
+
+  @spec hash(iodata()) :: binary()
+  def hash(data), do: :crypto.hash(:sha256, data)
+
   def encode(value, {:int, size}), do: encode_int(value, size)
   def encode(value, :bool), do: encode_bool(value)