implement new RANDAO reveals (#92)

* implement new RANDAO reveals

beacon_chain/beacon_node.nim

@@ -210,7 +210,7 @@ proc proposeBlock(node: BeaconNode,
   var newBlock = BeaconBlock(
     slot: slot,
     parent_root: node.headBlockRoot,
-    randao_reveal: ValidatorSig(), # TODO probably wrong
+    randao_reveal: validator.genRandaoReveal(state),
     eth1_data: node.mainchainMonitor.getBeaconBlockRef(),
     signature: ValidatorSig(), # we need the rest of the block first!
     body: blockBody)

beacon_chain/spec/beaconstate.nim

@@ -47,8 +47,7 @@ func process_deposit(state: var BeaconState,
                      pubkey: ValidatorPubKey,
                      amount: uint64,
                      proof_of_possession: ValidatorSig,
-                     withdrawal_credentials: Eth2Digest,
+                     withdrawal_credentials: Eth2Digest) =
-                     randao_commitment: Eth2Digest) =
   ## Process a deposit from Ethereum 1.0.
 
   if false:
@@ -206,7 +205,6 @@ func get_initial_beacon_state*(
       deposit.deposit_data.amount,
       deposit.deposit_data.deposit_input.proof_of_possession,
       deposit.deposit_data.deposit_input.withdrawal_credentials,
-      deposit.deposit_data.deposit_input.randao_commitment,
     )
 
   # Process initial activations

beacon_chain/spec/datatypes.nim

@@ -252,7 +252,6 @@ type
   DepositInput* = object
     pubkey*: ValidatorPubKey
     withdrawal_credentials*: Eth2Digest
-    randao_commitment*: Eth2Digest # Initial RANDAO commitment
     proof_of_possession*: ValidatorSig ##\
     ## BLS proof of possession (a BLS signature)
 

beacon_chain/validator_keygen.nim

@@ -49,8 +49,7 @@ cli do (validators: int,
 
       proofOfPossessionData = DepositInput(
         pubkey: pubKey,
-        withdrawal_credentials: withdrawalCredentials,
+        withdrawal_credentials: withdrawalCredentials)
-        randao_commitment: randaoCommitment)
 
       proofOfPossession = bls_sign(
         privkey, hash_tree_root_final(proofOfPossessionData).data,
@@ -64,8 +63,7 @@ cli do (validators: int,
         deposit_input: DepositInput(
           pubkey: pubKey,
           proof_of_possession: proofOfPossession,
-          withdrawal_credentials: withdrawalCredentials,
+          withdrawal_credentials: withdrawalCredentials)))
-          randao_commitment: randaoCommitment)))
 
   startupData.genesisTime = uint64(int(now() div 1000) + startupDelay)
 

beacon_chain/validator_pool.nim

@@ -1,7 +1,7 @@
 import
   tables, random,
   chronos,
-  spec/[datatypes, crypto, digest], randao, ssz
+  spec/[datatypes, crypto, digest, helpers], randao, ssz
 
 type
   ValidatorKind = enum
@@ -83,3 +83,17 @@ proc randaoReveal*(v: AttachedValidator, commitment: Eth2Digest): Future[Eth2Dig
     # send RPC
     discard
 
+# TODO move elsewhere when something else wants this utility function
+func int_to_bytes32(x: uint64) : array[32, byte] =
+  for i in 0 ..< 8:
+    result[31 - i] = byte((x shr i*8) and 0xff)
+
+func genRandaoReveal*(k: ValidatorPrivKey, state: BeaconState):
+    ValidatorSig =
+  # https://github.com/ethereum/eth2.0-specs/blob/v0.1/specs/core/0_beacon-chain.md#randao
+  bls_sign(k, int_to_bytes32(get_current_epoch(state)),
+           get_domain(state.fork, get_current_epoch(state), DOMAIN_RANDAO))
+
+func genRandaoReveal*(v: AttachedValidator, state: BeaconState):
+    ValidatorSig =
+  genRandaoReveal(v.privKey, state)

tests/testutil.nim

@@ -7,12 +7,9 @@
 
 import
   options, sequtils,
-  ../beacon_chain/[extras, ssz, state_transition],
+  ../beacon_chain/[extras, ssz, state_transition, validator_pool],
   ../beacon_chain/spec/[beaconstate, crypto, datatypes, digest, helpers, validator]
 
-const
-  randaoRounds = 100
-
 func makeValidatorPrivKey(i: int): ValidatorPrivKey =
   var i = i + 1 # 0 does not work, as private key...
   copyMem(result.x[0].addr, i.addr, min(sizeof(result.x), sizeof(i)))
@@ -36,7 +33,6 @@ func makeDeposit(i: int, flags: UpdateFlags): Deposit =
     privkey = makeValidatorPrivKey(i)
     pubkey = privkey.pubKey()
     withdrawal_credentials = makeFakeHash(i)
-    randao_commitment = repeat_hash(withdrawal_credentials, randaoRounds)
 
   let pop =
     if skipValidation in flags:
@@ -45,7 +41,6 @@ func makeDeposit(i: int, flags: UpdateFlags): Deposit =
       let proof_of_possession_data = DepositInput(
         pubkey: pubkey,
         withdrawal_credentials: withdrawal_credentials,
-        randao_commitment: randao_commitment
       )
       let domain = 0'u64
       bls_sign(privkey, hash_tree_root_final(proof_of_possession_data).data, domain)
@@ -56,7 +51,6 @@ func makeDeposit(i: int, flags: UpdateFlags): Deposit =
         pubkey: pubkey,
         proof_of_possession: pop,
         withdrawal_credentials: withdrawal_credentials,
-        randao_commitment: randao_commitment
       ),
       amount: MAX_DEPOSIT_AMOUNT,
     )
@@ -96,6 +90,7 @@ proc addBlock*(
   let
     # Index from the new state, but registry from the old state.. hmm...
     proposer = state.validator_registry[proposer_index]
+    privKey = hackPrivKey(proposer)
 
   var
     # In order to reuse the state transition function, we first create a dummy
@@ -105,7 +100,7 @@ proc addBlock*(
       slot: state.slot + 1,
       parent_root: previous_block_root,
       state_root: Eth2Digest(), # we need the new state first
-      randao_reveal: ValidatorSig(), # TODO
+      randao_reveal: privKey.genRandaoReveal(state),
       eth1_data: Eth1Data(), # TODO
       signature: ValidatorSig(), # we need the rest of the block first!
       body: body