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Merge pull request #69 from ethereum/vbuterin-patch-7

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Add RANDAO multi-hashing
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Danny Ryan 2018-10-15 13:14:59 -05:00 committed by GitHub
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1 changed files with 14 additions and 4 deletions
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18
specs/beacon-chain.md
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@ -42,6 +42,7 @@ The primary source of load on the beacon chain are "attestations". Attestations
| `WITHDRAWAL_PERIOD` | 2**19 (= 524,288) | slots | ~97 days |
| `BASE_REWARD_QUOTIENT` | 2**15 (= 32,768) | — |
| `MAX_VALIDATOR_CHURN_QUOTIENT` | 2**5 (= 32) | — |
| `RANDAO_SLOTS_PER_LAYER` | 2**12 (=4096) | slots | ~18 hours |
| `LOGOUT_MESSAGE` | `"LOGOUT"` | — |
| `MIN_ONLINE_DEPOSIT_SIZE` | 2**4 (= 16) | ETH |
@ -226,6 +227,8 @@ A `ValidatorRecord` has the following fields:
'withdrawal_address': 'address',
# RANDAO commitment
'randao_commitment': 'hash32',
# Slot the RANDAO commitment was last changed
'randao_last_change': 'int64',
# Balance
'balance': 'int64',
# Status code
@ -487,7 +490,8 @@ def on_startup(initial_validator_entries: List[Any]) -> Tuple[CrystallizedState,
proof_of_possession=proof_of_possession,
withdrawal_shard=withdrawal_shard,
withdrawal_address=withdrawal_address,
randao_commitment=randao_commitment
randao_commitment=randao_commitment,
current_slot=0
)
# Setup crystallized state
x = get_new_shuffling(bytes([0] * 32), validators, 0)
@ -542,7 +546,8 @@ def add_validator(validators: List[ValidatorRecord],
proof_of_possession: bytes,
withdrawal_shard: int,
withdrawal_address: Address,
randao_commitment: Hash32) -> int:
randao_commitment: Hash32,
current_slot: int) -> int:
# if following assert fails, validator induction failed
# move on to next validator registration log
assert BLSVerify(pub=pubkey,
@ -553,6 +558,7 @@ def add_validator(validators: List[ValidatorRecord],
withdrawal_shard=withdrawal_shard,
withdrawal_address=withdrawal_address,
randao_commitment=randao_commitment,
randao_last_change=current_slot,
balance=DEPOSIT_SIZE * GWEI_PER_ETH, # in Gwei
status=PENDING_ACTIVATION,
exit_slot=0
@ -623,9 +629,13 @@ For each one of these attestations:
Extend the list of `AttestationRecord` objects in the `active_state` with those included in the block, ordering the new additions in the same order as they came in the block. Similarly extend the list of `SpecialRecord` objects in the `active_state` with those included in the block.
Let `proposer_index` be the validator index of the `parent.slot % len(get_shards_and_committees_for_slot(crystallized_state, parent.slot)[0].committee)`'th attester in `get_shards_and_committees_for_slot(crystallized_state, parent.slot)[0]`. Verify that an attestation from this validator is part of the first (ie. item 0 in the array) `AttestationRecord` object; this attester can be considered to be the proposer of the parent block. In general, when a block is produced, it is broadcasted at the network layer along with the attestation from its proposer.
Let `curblock_proposer_index` be the validator index of the `block.slot % len(get_shards_and_committees_for_slot(crystallized_state, block.slot)[0].committee)`'th attester in `get_shards_and_committees_for_slot(crystallized_state, block.slot)[0]`, and `parent_proposer_index` be the validator index of the parent block, calculated similarly. Verify that an attestation from the `parent_proposer_index`'th validator is part of the first (ie. item 0 in the array) `AttestationRecord` object; this attester can be considered to be the proposer of the parent block. In general, when a block is produced, it is broadcasted at the network layer along with the attestation from its proposer.
Additionally, verify that `hash(block.randao_reveal) == crystallized_state.validators[proposer_index].randao_commitment`, and set `active_state.randao_mix = xor(active_state.randao_mix, block.randao_reveal)` and append to `ActiveState.pending_specials` a `SpecialObject(kind=RANDAO_CHANGE, data=[bytes8(proposer_index), block.randao_reveal])`.
Additionally, verify and update the RANDAO reveal. This is done as follows:
* Let `repeat_hash(x, n) = x if n == 0 else repeat_hash(hash(x), n-1)`.
* Let `V = crystallized_state.validators[curblock_proposer_index]`.
* Verify that `repeat_hash(block.randao_reveal, (block.slot - V.randao_last_reveal) // RANDAO_SLOTS_PER_LAYER + 1) == V.randao_commitment`, and set `active_state.randao_mix = xor(active_state.randao_mix, block.randao_reveal)` and append to `ActiveState.pending_specials` a `SpecialObject(kind=RANDAO_CHANGE, data=[bytes8(curblock_proposer_index), block.randao_reveal])`.
### State recalculations (every `CYCLE_LENGTH` slots)