Separate type for onchain attestation aggregates

specs/electra/beacon-chain.md

@@ -31,6 +31,7 @@
     - [`Consolidation`](#consolidation)
     - [`SignedConsolidation`](#signedconsolidation)
     - [`PendingConsolidation`](#pendingconsolidation)
+    - [`OnchainAttestation`](#onchainattestation)
   - [Modified Containers](#modified-containers)
     - [`AttesterSlashing`](#attesterslashing)
   - [Extended Containers](#extended-containers)
@@ -49,6 +50,8 @@
     - [New `has_execution_withdrawal_credential`](#new-has_execution_withdrawal_credential)
     - [Updated `is_fully_withdrawable_validator`](#updated-is_fully_withdrawable_validator)
     - [Updated `is_partially_withdrawable_validator`](#updated-is_partially_withdrawable_validator)
+    - [New `compute_signing_attestation_data`](#new-compute_signing_attestation_data)
+    - [Modified `is_valid_indexed_attestation`](#modified-is_valid_indexed_attestation)
   - [Misc](#misc-1)
     - [`get_committee_indices`](#get_committee_indices)
     - [`get_validator_max_effective_balance`](#get_validator_max_effective_balance)
@@ -58,7 +61,7 @@
     - [New `get_consolidation_churn_limit`](#new-get_consolidation_churn_limit)
     - [New `get_active_balance`](#new-get_active_balance)
     - [New `get_pending_balance_to_withdraw`](#new-get_pending_balance_to_withdraw)
-    - [Modified `get_attesting_indices`](#modified-get_attesting_indices)
+    - [New `get_onchain_attesting_indices`](#new-get_onchain_attesting_indices)
   - [Beacon state mutators](#beacon-state-mutators)
     - [Updated  `initiate_validator_exit`](#updated--initiate_validator_exit)
     - [New `switch_to_compounding_validator`](#new-switch_to_compounding_validator)
@@ -83,7 +86,7 @@
     - [Operations](#operations)
       - [Modified `process_operations`](#modified-process_operations)
       - [Attestations](#attestations)
-        - [Modified `process_attestation`](#modified-process_attestation)
+        - [New `process_onchain_attestation`](#new-process_onchain_attestation)
       - [Deposits](#deposits)
         - [Updated  `apply_deposit`](#updated--apply_deposit)
         - [New `is_valid_deposit_signature`](#new-is_valid_deposit_signature)
@@ -270,6 +273,18 @@ class PendingConsolidation(Container):
     target_index: ValidatorIndex
 ```
 
+#### `OnchainAttestation`
+
+*Note*: The container is new in EIP7549.
+
+```python
+class OnchainAttestation(Container):
+    aggregation_bits: Bitlist[MAX_VALIDATORS_PER_COMMITTEE * MAX_COMMITTEES_PER_SLOT]
+    data: AttestationData
+    committee_bits: Bitvector[MAX_COMMITTEES_PER_SLOT]
+    signature: BLSSignature
+```
+
 ### Modified Containers
 
 #### `AttesterSlashing`
@@ -312,7 +327,7 @@ class BeaconBlockBody(Container):
     # Operations
     proposer_slashings: List[ProposerSlashing, MAX_PROPOSER_SLASHINGS]
     attester_slashings: List[AttesterSlashing, MAX_ATTESTER_SLASHINGS_ELECTRA]  # [Modified in Electra:EIP7549]
-    attestations: List[Attestation, MAX_ATTESTATIONS_ELECTRA]  # [Modified in Electra:EIP7549]
+    attestations: List[OnchainAttestation, MAX_ATTESTATIONS_ELECTRA]  # [Modified in Electra:EIP7549]
     deposits: List[Deposit, MAX_DEPOSITS]
     voluntary_exits: List[SignedVoluntaryExit, MAX_VOLUNTARY_EXITS]
     sync_aggregate: SyncAggregate
@@ -531,6 +546,47 @@ def is_partially_withdrawable_validator(validator: Validator, balance: Gwei) ->
     )
 ```
 
+#### New `compute_signing_attestation_data`
+
+*Note:* This function constructs attestation data for the signing purpose.
+
+```python
+def compute_signing_attestation_data(data: AttestationData) -> AttestationData:
+    """
+    Returns ``AttestationData`` with ``index`` set to ``0``.
+    """
+    return AttestationData(
+        slot = indexed_attestation.data.slot,
+        index = CommitteeIndex(0),
+        beacon_block_root = indexed_attestation.data.beacon_block_root,
+        source = indexed_attestation.data.source,
+        target = indexed_attestation.data.target,
+    )
+```
+
+#### Modified `is_valid_indexed_attestation`
+
+*Note*: This function is modified to verify signature over signing `AttestationData`.
+
+```python
+def is_valid_indexed_attestation(state: BeaconState, indexed_attestation: IndexedAttestation) -> bool:
+    """
+    Check if ``indexed_attestation`` is not empty, has sorted and unique indices and has a valid aggregate signature.
+    """
+    # Verify indices are sorted and unique
+    indices = indexed_attestation.attesting_indices
+    if len(indices) == 0 or not indices == sorted(set(indices)):
+        return False
+    # Verify aggregate signature
+    pubkeys = [state.validators[i].pubkey for i in indices]
+    domain = get_domain(state, DOMAIN_BEACON_ATTESTER, indexed_attestation.data.target.epoch)
+    # [New in Electra:EIP7549]
+    signing_data = compute_signing_attestation_data(indexed_attestation.data)
+    signing_root = compute_signing_root(signed_data, domain)
+    return bls.FastAggregateVerify(pubkeys, signing_root, indexed_attestation.signature)
+```
+
+
 ### Misc
 
 #### `get_committee_indices`
@@ -603,10 +659,10 @@ def get_pending_balance_to_withdraw(state: BeaconState, validator_index: Validat
     )
 ```
 
-#### Modified `get_attesting_indices`
+#### New `get_onchain_attesting_indices`
 
 ```python
-def get_attesting_indices(state: BeaconState, attestation: Attestation) -> Set[ValidatorIndex]:
+def get_onchain_attesting_indices(state: BeaconState, attestation: OnchainAttestation) -> Set[ValidatorIndex]:
     """
     Return the set of attesting indices corresponding to ``aggregation_bits`` and ``committee_bits``.
     """
@@ -1060,7 +1116,7 @@ def process_operations(state: BeaconState, body: BeaconBlockBody) -> None:
 
     for_ops(body.proposer_slashings, process_proposer_slashing)
     for_ops(body.attester_slashings, process_attester_slashing)
-    for_ops(body.attestations, process_attestation)  # [Modified in Electra:EIP7549]
+    for_ops(body.attestations, process_onchain_attestation)  # [Modified in Electra:EIP7549]
     for_ops(body.deposits, process_deposit)  # [Modified in Electra:EIP7251]
     for_ops(body.voluntary_exits, process_voluntary_exit)  # [Modified in Electra:EIP7251]
     for_ops(body.bls_to_execution_changes, process_bls_to_execution_change)
@@ -1072,10 +1128,10 @@ def process_operations(state: BeaconState, body: BeaconBlockBody) -> None:
 
 ##### Attestations
 
-###### Modified `process_attestation`
+###### New `process_onchain_attestation`
 
 ```python
-def process_attestation(state: BeaconState, attestation: Attestation) -> None:
+def process_onchain_attestation(state: BeaconState, attestation: OnchainAttestation) -> None:
     data = attestation.data
     assert data.target.epoch in (get_previous_epoch(state), get_current_epoch(state))
     assert data.target.epoch == compute_epoch_at_slot(data.slot)
@@ -1096,7 +1152,12 @@ def process_attestation(state: BeaconState, attestation: Attestation) -> None:
     participation_flag_indices = get_attestation_participation_flag_indices(state, data, state.slot - data.slot)
 
     # Verify signature
-    assert is_valid_indexed_attestation(state, get_indexed_attestation(state, attestation))
+    indexed_attestation = IndexedAttestation(
+        attesting_indices=sorted(get_onchain_attesting_indices(state, attestation)),
+        data=attestation.data,
+        signature=attestation.signature,
+    )
+    assert is_valid_indexed_attestation(state, indexed_attestation)
 
     # Update epoch participation flags
     if data.target.epoch == get_current_epoch(state):
@@ -1105,7 +1166,7 @@ def process_attestation(state: BeaconState, attestation: Attestation) -> None:
         epoch_participation = state.previous_epoch_participation
 
     proposer_reward_numerator = 0
-    for index in get_attesting_indices(state, attestation):
+    for index in get_onchain_attesting_indices(state, attestation):
         for flag_index, weight in enumerate(PARTICIPATION_FLAG_WEIGHTS):
             if flag_index in participation_flag_indices and not has_flag(epoch_participation[index], flag_index):
                 epoch_participation[index] = add_flag(epoch_participation[index], flag_index)

specs/electra/p2p-interface.md

@@ -13,9 +13,6 @@ The specification of these changes continues in the same format as the network s
 - [Modifications in Electra](#modifications-in-electra)
   - [The gossip domain: gossipsub](#the-gossip-domain-gossipsub)
     - [Topics and messages](#topics-and-messages)
-    - [Global topics](#global-topics)
-      - [`beacon_aggregate_and_proof`](#beacon_aggregate_and_proof)
-      - [`beacon_attestation_{subnet_id}`](#beacon_attestation_subnet_id)
 
 <!-- END doctoc generated TOC please keep comment here to allow auto update -->
 <!-- /TOC -->
@@ -32,28 +29,6 @@ Topics follow the same specification as in prior upgrades.
 
 The `beacon_block` topic is modified to also support Electra blocks.
 
-The `beacon_aggregate_and_proof` and `beacon_attestation_{subnet_id}` topics are modified to support the gossip of the new attestation type.
-
 The specification around the creation, validation, and dissemination of messages has not changed from the Capella document unless explicitly noted here.
 
 The derivation of the `message-id` remains stable.
-
-#### Global topics
-
-##### `beacon_aggregate_and_proof`
-
-The following convenience variables are re-defined
-- `index = get_committee_indices(aggregate.committee_bits)[0]`
-
-The following validations are added:
-* [REJECT] `len(committee_indices) == 1`, where `committee_indices = get_committee_indices(aggregate)`.
-* [REJECT] `aggregate.data.index == 0`
-
-##### `beacon_attestation_{subnet_id}`
-
-The following convenience variables are re-defined
-- `index = get_committee_indices(attestation.committee_bits)[0]`
-
-The following validations are added:
-* [REJECT] `len(committee_indices) == 1`, where `committee_indices = get_committee_indices(attestation)`.
-* [REJECT] `attestation.data.index == 0`

specs/electra/validator.md

@@ -19,9 +19,7 @@
     - [Deposits](#deposits)
     - [Execution payload](#execution-payload)
 - [Attesting](#attesting)
-  - [Construct attestation](#construct-attestation)
-- [Attestation aggregation](#attestation-aggregation)
-  - [Construct aggregate](#construct-aggregate)
+      - [Modified aggregate signature](#modified-aggregate-signature)
 
 <!-- END doctoc generated TOC please keep comment here to allow auto update -->
 <!-- /TOC -->
@@ -72,14 +70,14 @@ Changed the max attester slashings size to `MAX_ATTESTER_SLASHINGS_ELECTRA`.
 Changed the max attestations size to `MAX_ATTESTATIONS_ELECTRA`.
 
 The network attestation aggregates contain only the assigned committee attestations.
-Attestation aggregates received by the block proposer from the committee aggregators with disjoint `committee_bits` sets and equal `AttestationData` SHOULD be consolidated into a single `Attestation` object.
-The proposer should run the following function to construct an on chain final aggregate form a list of network aggregates with equal `AttestationData`:
+Attestation aggregates received by the block proposer from the committee aggregators with disjoint `committee_bits` sets and equal signing `AttestationData` SHOULD be consolidated into a single `OnchainAttestation` object.
+The proposer should run the following function to construct an on chain final aggregate form a list of network aggregates with equal signing `AttestationData`:
 
 ```python
-def compute_on_chain_aggregate(network_aggregates: Sequence[Attestation]) -> Attestation:
+def compute_on_chain_aggregate(network_aggregates: Sequence[Attestation]) -> OnchainAttestation:
     aggregates = sorted(network_aggregates, key=lambda a: get_committee_indices(a.committee_bits)[0])
 
-    data = aggregates[0].data
+    data = compute_signing_attestation_data(aggregates[0].data)
     aggregation_bits = Bitlist[MAX_VALIDATORS_PER_COMMITTEE * MAX_COMMITTEES_PER_SLOT]()
     for a in aggregates:
         for b in a.aggregation_bits:
@@ -91,7 +89,7 @@ def compute_on_chain_aggregate(network_aggregates: Sequence[Attestation]) -> Att
     committee_flags = [(index in committee_indices) for index in range(0, MAX_COMMITTEES_PER_SLOT)]
     committee_bits = Bitvector[MAX_COMMITTEES_PER_SLOT](committee_flags)
 
-    return Attestation(
+    return OnchainAttestation(
         aggregation_bits=aggregation_bits,
         data=data,
         committee_bits=committee_bits,
@@ -150,18 +148,16 @@ def prepare_execution_payload(state: BeaconState,
 
 ## Attesting
 
-### Construct attestation
+##### Modified aggregate signature
 
-- Set `attestation_data.index = 0`.
-- Let `attestation.aggregation_bits` be a `Bitlist[MAX_VALIDATORS_PER_COMMITTEE * MAX_COMMITTEES_PER_SLOT]` of length `len(committee)`, where the bit of the index of the validator in the `committee` is set to `0b1`.
-- Let `attestation.committee_bits` be a `Bitvector[MAX_COMMITTEES_PER_SLOT]`, where the bit at the index associated with the validator's committee is set to `0b1`.
+*Note:* The `get_attestation_signature` method is modified to use signing attestation data.
 
-*Note*: Calling `get_attesting_indices(state, attestation)` should return a list of length equal to 1, containing `validator_index`.
+Set `attestation.signature = attestation_signature` where `attestation_signature` is obtained from:
 
-## Attestation aggregation
-
-### Construct aggregate
-
-- Set `attestation_data.index = 0`.
-- Let `aggregation_bits` be a `Bitlist[MAX_VALIDATORS_PER_COMMITTEE * MAX_COMMITTEES_PER_SLOT]` of length `len(committee)`, where each bit set from each individual attestation is set to `0b1`.
-- Set `attestation.committee_bits = committee_bits`, where `committee_bits` has the same value as in each individual attestation.
+```python
+def get_attestation_signature(state: BeaconState, attestation_data: AttestationData, privkey: int) -> BLSSignature:
+    domain = get_domain(state, DOMAIN_BEACON_ATTESTER, attestation_data.target.epoch)
+    signing_data = compute_signing_attestation_data(attestation_data)
+    signing_root = compute_signing_root(signing_data, domain)
+    return bls.Sign(privkey, signing_root)
+```