diff --git a/specs/core/0_beacon-chain.md b/specs/core/0_beacon-chain.md index 2c0bc2554..991c35494 100644 --- a/specs/core/0_beacon-chain.md +++ b/specs/core/0_beacon-chain.md @@ -28,7 +28,7 @@ - [`Eth1DataVote`](#eth1datavote) - [`AttestationData`](#attestationdata) - [`AttestationDataAndCustodyBit`](#attestationdataandcustodybit) - - [`SlashableAttestation`](#slashableattestation) + - [`IndexedAttestation`](#indexedattestation) - [`DepositData`](#depositdata) - [`BeaconBlockHeader`](#beaconblockheader) - [`Validator`](#validator) @@ -77,6 +77,7 @@ - [`generate_seed`](#generate_seed) - [`get_beacon_proposer_index`](#get_beacon_proposer_index) - [`verify_merkle_branch`](#verify_merkle_branch) + - [`get_crosslink_committee_for_attestation`](#get_crosslink_committee_for_attestation) - [`get_attestation_participants`](#get_attestation_participants) - [`int_to_bytes1`, `int_to_bytes2`, ...](#int_to_bytes1-int_to_bytes2-) - [`bytes_to_int`](#bytes_to_int) @@ -86,7 +87,8 @@ - [`get_domain`](#get_domain) - [`get_bitfield_bit`](#get_bitfield_bit) - [`verify_bitfield`](#verify_bitfield) - - [`verify_slashable_attestation`](#verify_slashable_attestation) + - [`convert_to_indexed`](#convert_to_indexed) + - [`verify_indexed_attestation`](#verify_indexed_attestation) - [`is_double_vote`](#is_double_vote) - [`is_surround_vote`](#is_surround_vote) - [`integer_squareroot`](#integer_squareroot) @@ -183,7 +185,7 @@ Code snippets appearing in `this style` are to be interpreted as Python code. | `SHARD_COUNT` | `2**10` (= 1,024) | | `TARGET_COMMITTEE_SIZE` | `2**7` (= 128) | | `MAX_BALANCE_CHURN_QUOTIENT` | `2**5` (= 32) | -| `MAX_SLASHABLE_ATTESTATION_PARTICIPANTS` | `2**12` (= 4,096) | +| `MAX_ATTESTATION_PARTICIPANTS` | `2**12` (= 4,096) | | `MAX_EXIT_DEQUEUES_PER_EPOCH` | `2**2` (= 4) | | `SHUFFLE_ROUND_COUNT` | 90 | @@ -369,16 +371,15 @@ The types are defined topologically to aid in facilitating an executable version } ``` -#### `SlashableAttestation` +#### `IndexedAttestation` ```python { # Validator indices - 'validator_indices': ['uint64'], + 'custody_bit_0_indices': ['uint64'], + 'custody_bit_1_indices': ['uint64'], # Attestation data 'data': AttestationData, - # Custody bitfield - 'custody_bitfield': 'bytes', # Aggregate signature 'aggregate_signature': 'bytes96', } @@ -478,10 +479,10 @@ The types are defined topologically to aid in facilitating an executable version ```python { - # First slashable attestation - 'slashable_attestation_1': SlashableAttestation, - # Second slashable attestation - 'slashable_attestation_2': SlashableAttestation, + # First attestation + 'attestation_1': IndexedAttestation, + # Second attestation + 'attestation_2': IndexedAttestation, } ``` @@ -1036,6 +1037,20 @@ def verify_merkle_branch(leaf: Bytes32, proof: List[Bytes32], depth: int, index: return value == root ``` +### `get_crosslink_committee_for_attestation` + +```python +def get_crosslink_committee_for_attestation(state: BeaconState, + attestation_data: AttestationData) -> List[ValidatorIndex]: + # Find the committee in the list with the desired shard + crosslink_committees = get_crosslink_committees_at_slot(state, attestation_data.slot) + + assert attestation_data.shard in [shard for _, shard in crosslink_committees] + crosslink_committee = [committee for committee, shard in crosslink_committees if shard == attestation_data.shard][0] + + return crosslink_committee +``` + ### `get_attestation_participants` ```python @@ -1043,13 +1058,9 @@ def get_attestation_participants(state: BeaconState, attestation_data: AttestationData, bitfield: bytes) -> List[ValidatorIndex]: """ - Return the participant indices corresponding to ``attestation_data`` and ``bitfield``. + Return the sorted participant indices corresponding to ``attestation_data`` and ``bitfield``. """ - # Find the committee in the list with the desired shard - crosslink_committees = get_crosslink_committees_at_slot(state, attestation_data.slot) - - assert attestation_data.shard in [shard for _, shard in crosslink_committees] - crosslink_committee = [committee for committee, shard in crosslink_committees if shard == attestation_data.shard][0] + crosslink_committee = get_crosslink_committee_for_attestation(state, attestation_data) assert verify_bitfield(bitfield, len(crosslink_committee)) @@ -1059,7 +1070,7 @@ def get_attestation_participants(state: BeaconState, aggregation_bit = get_bitfield_bit(bitfield, i) if aggregation_bit == 0b1: participants.append(validator_index) - return participants + return sorted(participants) ``` ### `int_to_bytes1`, `int_to_bytes2`, ... @@ -1147,33 +1158,47 @@ def verify_bitfield(bitfield: bytes, committee_size: int) -> bool: return True ``` -### `verify_slashable_attestation` +### `convert_to_indexed` ```python -def verify_slashable_attestation(state: BeaconState, slashable_attestation: SlashableAttestation) -> bool: +def convert_to_indexed(state: BeaconState, attestation: Attestation): """ - Verify validity of ``slashable_attestation`` fields. + Convert an attestation to (almost) indexed-verifiable form """ - if slashable_attestation.custody_bitfield != b'\x00' * len(slashable_attestation.custody_bitfield): # [TO BE REMOVED IN PHASE 1] + attesting_indices = get_attestation_participants(state, attestation.data, attestation.aggregation_bitfield) + custody_bit_1_indices = get_attestation_participants(state, attestation.data, attestation.custody_bitfield) + custody_bit_0_indices = [index for index in attesting_indices if index not in custody_bit_1_indices] + + return IndexedAttestation( + custody_bit_0_indices=custody_bit_0_indices, + custody_bit_1_indices=custody_bit_1_indices, + data=attestation.data, + aggregate_signature=attestation.aggregate_signature + ) +``` + +### `verify_indexed_attestation` + +```python +def verify_indexed_attestation(state: BeaconState, indexed_attestation: IndexedAttestation) -> bool: + """ + Verify validity of ``indexed_attestation`` fields. + """ + custody_bit_0_indices = indexed_attestation.custody_bit_0_indices + custody_bit_1_indices = indexed_attestation.custody_bit_1_indices + + if len(custody_bit_1_indices) > 0: # [TO BE REMOVED IN PHASE 1] return False - if not (1 <= len(slashable_attestation.validator_indices) <= MAX_SLASHABLE_ATTESTATION_PARTICIPANTS): + total_attesting_indices = len(custody_bit_0_indices + custody_bit_1_indices) + if not (1 <= total_attesting_indices <= MAX_ATTESTATION_PARTICIPANTS): return False - for i in range(len(slashable_attestation.validator_indices) - 1): - if slashable_attestation.validator_indices[i] >= slashable_attestation.validator_indices[i + 1]: - return False - - if not verify_bitfield(slashable_attestation.custody_bitfield, len(slashable_attestation.validator_indices)): + if custody_bit_0_indices != sorted(custody_bit_0_indices): return False - custody_bit_0_indices = [] - custody_bit_1_indices = [] - for i, validator_index in enumerate(slashable_attestation.validator_indices): - if get_bitfield_bit(slashable_attestation.custody_bitfield, i) == 0b0: - custody_bit_0_indices.append(validator_index) - else: - custody_bit_1_indices.append(validator_index) + if custody_bit_1_indices != sorted(custody_bit_1_indices): + return False return bls_verify_multiple( pubkeys=[ @@ -1181,11 +1206,11 @@ def verify_slashable_attestation(state: BeaconState, slashable_attestation: Slas bls_aggregate_pubkeys([state.validator_registry[i].pubkey for i in custody_bit_1_indices]), ], message_hashes=[ - hash_tree_root(AttestationDataAndCustodyBit(data=slashable_attestation.data, custody_bit=0b0)), - hash_tree_root(AttestationDataAndCustodyBit(data=slashable_attestation.data, custody_bit=0b1)), + hash_tree_root(AttestationDataAndCustodyBit(data=indexed_attestation.data, custody_bit=0b0)), + hash_tree_root(AttestationDataAndCustodyBit(data=indexed_attestation.data, custody_bit=0b1)), ], - signature=slashable_attestation.aggregate_signature, - domain=get_domain(state.fork, slot_to_epoch(slashable_attestation.data.slot), DOMAIN_ATTESTATION), + signature=indexed_attestation.aggregate_signature, + domain=get_domain(state.fork, slot_to_epoch(indexed_attestation.data.slot), DOMAIN_ATTESTATION), ) ``` @@ -2251,16 +2276,17 @@ def process_attester_slashing(state: BeaconState, Process ``AttesterSlashing`` transaction. Note that this function mutates ``state``. """ - attestation1 = attester_slashing.slashable_attestation_1 - attestation2 = attester_slashing.slashable_attestation_2 + attestation1 = attester_slashing.attestation_1 + attestation2 = attester_slashing.attestation_2 # Check that the attestations are conflicting assert attestation1.data != attestation2.data assert ( is_double_vote(attestation1.data, attestation2.data) or is_surround_vote(attestation1.data, attestation2.data) ) - assert verify_slashable_attestation(state, attestation1) - assert verify_slashable_attestation(state, attestation2) + + assert verify_indexed_attestation(state, attestation1) + assert verify_indexed_attestation(state, attestation2) slashable_indices = [ index for index in attestation1.validator_indices if ( @@ -2306,18 +2332,8 @@ def process_attestation(state: BeaconState, attestation: Attestation) -> None: ), } - # Check custody bits [to be generalised in phase 1] - assert attestation.custody_bitfield == b'\x00' * len(attestation.custody_bitfield) - - # Check aggregate signature [to be generalised in phase 1] - participants = get_attestation_participants(state, attestation.data, attestation.aggregation_bitfield) - assert len(participants) != 0 - assert bls_verify( - pubkey=bls_aggregate_pubkeys([state.validator_registry[i].pubkey for i in participants]), - message_hash=hash_tree_root(AttestationDataAndCustodyBit(data=attestation.data, custody_bit=0b0)), - signature=attestation.aggregate_signature, - domain=get_domain(state.fork, target_epoch, DOMAIN_ATTESTATION), - ) + # Check signature and bitfields + assert verify_indexed_attestation(state, convert_to_indexed(state, attestation)) # Cache pending attestation pending_attestation = PendingAttestation( diff --git a/tests/phase0/block_processing/test_process_attestation.py b/tests/phase0/block_processing/test_process_attestation.py index 08cab11ff..ca6933ce7 100644 --- a/tests/phase0/block_processing/test_process_attestation.py +++ b/tests/phase0/block_processing/test_process_attestation.py @@ -135,7 +135,7 @@ def test_non_empty_custody_bitfield(state): attestation = get_valid_attestation(state) state.slot += spec.MIN_ATTESTATION_INCLUSION_DELAY - attestation.custody_bitfield = b'\x01' + attestation.custody_bitfield[1:] + attestation.custody_bitfield = deepcopy(attestation.aggregation_bitfield) pre_state, post_state = run_attestation_processing(state, attestation, False) diff --git a/tests/phase0/helpers.py b/tests/phase0/helpers.py index d7f4ae6e8..e5e335d80 100644 --- a/tests/phase0/helpers.py +++ b/tests/phase0/helpers.py @@ -22,12 +22,14 @@ from build.phase0.spec import ( get_active_validator_indices, get_attestation_participants, get_block_root, + get_crosslink_committee_for_attestation, get_crosslink_committees_at_slot, get_current_epoch, get_domain, get_empty_block, get_epoch_start_slot, get_genesis_beacon_state, + slot_to_epoch, verify_merkle_branch, hash, ) @@ -248,12 +250,11 @@ def get_valid_attestation(state, slot=None): shard = state.latest_start_shard attestation_data = build_attestation_data(state, slot, shard) - crosslink_committees = get_crosslink_committees_at_slot(state, slot) - crosslink_committee = [committee for committee, _shard in crosslink_committees if _shard == attestation_data.shard][0] + crosslink_committee = get_crosslink_committee_for_attestation(state, attestation_data) committee_size = len(crosslink_committee) bitfield_length = (committee_size + 7) // 8 - aggregation_bitfield = b'\x01' + b'\x00' * (bitfield_length - 1) + aggregation_bitfield = b'\xC0' + b'\x00' * (bitfield_length - 1) custody_bitfield = b'\x00' * bitfield_length attestation = Attestation( aggregation_bitfield=aggregation_bitfield, @@ -266,23 +267,35 @@ def get_valid_attestation(state, slot=None): attestation.data, attestation.aggregation_bitfield, ) - assert len(participants) == 1 + assert len(participants) == 2 - validator_index = participants[0] - privkey = privkeys[validator_index] + signatures = [] + for validator_index in participants: + privkey = privkeys[validator_index] + signatures.append( + get_attestation_signature( + state, + attestation.data, + privkey + ) + ) + attestation.aggregation_signature = bls.aggregate_signatures(signatures) + return attestation + + +def get_attestation_signature(state, attestation_data, privkey, custody_bit=0b0): message_hash = AttestationDataAndCustodyBit( - data=attestation.data, - custody_bit=0b0, + data=attestation_data, + custody_bit=custody_bit, ).hash_tree_root() - attestation.aggregation_signature = bls.sign( + return bls.sign( message_hash=message_hash, privkey=privkey, domain=get_domain( fork=state.fork, - epoch=get_current_epoch(state), + epoch=slot_to_epoch(attestation_data.slot), domain_type=spec.DOMAIN_ATTESTATION, ) ) - return attestation