From 3ee9fc0cc775a05042f7acbfc46e03ec24d14104 Mon Sep 17 00:00:00 2001 From: vbuterin Date: Fri, 22 Mar 2019 06:10:44 -0500 Subject: [PATCH] Merge attestation verification logic Also rename slashable attestation to standalone attestation to reflect its broader functionality in phase 1. --- specs/core/0_beacon-chain.md | 84 +++++++++++++++++++----------------- 1 file changed, 45 insertions(+), 39 deletions(-) diff --git a/specs/core/0_beacon-chain.md b/specs/core/0_beacon-chain.md index c29aa113d..a4d5f5ec6 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) + - [`StandaloneAttestation`](#standaloneattestation) - [`DepositInput`](#depositinput) - [`DepositData`](#depositdata) - [`BeaconBlockHeader`](#beaconblockheader) @@ -90,7 +90,8 @@ - [`get_domain`](#get_domain) - [`get_bitfield_bit`](#get_bitfield_bit) - [`verify_bitfield`](#verify_bitfield) - - [`verify_slashable_attestation`](#verify_slashable_attestation) + - [`convert_to_standalone`](#convert_to_standalone) + - [`verify_standalone_attestation`](#verify_standalone_attestation) - [`is_double_vote`](#is_double_vote) - [`is_surround_vote`](#is_surround_vote) - [`integer_squareroot`](#integer_squareroot) @@ -187,7 +188,7 @@ 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 | @@ -369,7 +370,7 @@ The types are defined topologically to aid in facilitating an executable version } ``` -#### `SlashableAttestation` +#### `StandaloneAttestation` ```python { @@ -489,10 +490,10 @@ 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': StandaloneAttestation, + # Second attestation + 'attestation_2': StandaloneAttestation, } ``` @@ -1116,7 +1117,7 @@ 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) ``` ### `is_power_of_two` @@ -1214,30 +1215,45 @@ def verify_bitfield(bitfield: bytes, committee_size: int) -> bool: return True ``` -### `verify_slashable_attestation` +### `convert_to_standalone` ```python -def verify_slashable_attestation(state: BeaconState, slashable_attestation: SlashableAttestation) -> bool: +def convert_to_standalone(state: BeaconState, attestation: Attestation): """ - Verify validity of ``slashable_attestation`` fields. + Converts an attestation to (almost) standalone-verifiable form """ - if slashable_attestation.custody_bitfield != b'\x00' * len(slashable_attestation.custody_bitfield): # [TO BE REMOVED IN PHASE 1] + return StandaloneAttestation( + validator_indices=get_attestation_participants(state, attestation.data, attestation.aggregation_bitfield), + data=attestation.data, + custody_bitfield=attestation.custody_bitfield, + aggregate_signature=attestation.aggregate_signature + ) +``` + +### `verify_standalone_attestation` + +```python +def verify_standalone_attestation(state: BeaconState, standalone_attestation: StandaloneAttestation) -> bool: + """ + Verify validity of ``standalone_attestation`` fields. + """ + if standalone_attestation.custody_bitfield != b'\x00' * len(standalone_attestation.custody_bitfield): # [TO BE REMOVED IN PHASE 1] return False - if not (1 <= len(slashable_attestation.validator_indices) <= MAX_SLASHABLE_ATTESTATION_PARTICIPANTS): + if not (1 <= len(standalone_attestation.validator_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]: + for i in range(len(standalone_attestation.validator_indices) - 1): + if standalone_attestation.validator_indices[i] >= standalone_attestation.validator_indices[i + 1]: return False - if not verify_bitfield(slashable_attestation.custody_bitfield, len(slashable_attestation.validator_indices)): + if not verify_bitfield(standalone_attestation.custody_bitfield, len(standalone_attestation.validator_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: + for i, validator_index in enumerate(standalone_attestation.validator_indices): + if get_bitfield_bit(standalone_attestation.custody_bitfield, i) == 0b0: custody_bit_0_indices.append(validator_index) else: custody_bit_1_indices.append(validator_index) @@ -1248,11 +1264,11 @@ 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=standalone_attestation.data, custody_bit=0b0)), + hash_tree_root(AttestationDataAndCustodyBit(data=standalone_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=standalone_attestation.aggregate_signature, + domain=get_domain(state.fork, slot_to_epoch(standalone_attestation.data.slot), DOMAIN_ATTESTATION), ) ``` @@ -2408,16 +2424,16 @@ 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_standalone_attestation(state, attestation1) + assert verify_standalone_attestation(state, attestation2) slashable_indices = [ index for index in attestation1.validator_indices if ( @@ -2462,18 +2478,8 @@ 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_standalone_attestation(state, convert_to_standalone(state, attestation)) # Cache pending attestation pending_attestation = PendingAttestation(