move attestation index outside signed message

pysetup/spec_builders/phase0.py

@@ -98,8 +98,8 @@ get_matching_head_attestations = cache_this(
 
 _get_attesting_indices = get_attesting_indices
 get_attesting_indices = cache_this(
-    lambda state, data, bits: (
+    lambda state, attestation: (
         state.randao_mixes.hash_tree_root(),
-        state.validators.hash_tree_root(), data.hash_tree_root(), bits.hash_tree_root()
+        state.validators.hash_tree_root(), attestation.hash_tree_root()
     ),
     _get_attesting_indices, lru_size=SLOTS_PER_EPOCH * MAX_COMMITTEES_PER_SLOT * 3)'''

specs/_features/custody_game/beacon-chain.md

@@ -401,7 +401,7 @@ def process_chunk_challenge(state: BeaconState, challenge: CustodyChunkChallenge
     # Verify responder is slashable
     assert is_slashable_validator(responder, get_current_epoch(state))
     # Verify the responder participated in the attestation
-    attesters = get_attesting_indices(state, challenge.attestation.data, challenge.attestation.aggregation_bits)
+    attesters = get_attesting_indices(state, challenge)
     assert challenge.responder_index in attesters
     # Verify shard transition is correctly given
     assert hash_tree_root(challenge.shard_transition) == challenge.attestation.data.shard_transition_root
@@ -594,7 +594,7 @@ def process_custody_slashing(state: BeaconState, signed_custody_slashing: Signed
     assert len(custody_slashing.data) == shard_transition.shard_block_lengths[custody_slashing.data_index]
     assert hash_tree_root(custody_slashing.data) == shard_transition.shard_data_roots[custody_slashing.data_index]
     # Verify existence and participation of claimed malefactor
-    attesters = get_attesting_indices(state, attestation.data, attestation.aggregation_bits)
+    attesters = get_attesting_indices(state, attestation)
     assert custody_slashing.malefactor_index in attesters
     
     # Verify the malefactor custody key

specs/_features/eip7549/beacon-chain.md

@@ -0,0 +1,64 @@
+# EIP-7549 -- The Beacon Chain
+
+## Table of contents
+
+<!-- TOC -->
+<!-- START doctoc generated TOC please keep comment here to allow auto update -->
+<!-- DON'T EDIT THIS SECTION, INSTEAD RE-RUN doctoc TO UPDATE -->
+
+- [Introduction](#introduction)
+- [Containers](#containers)
+  - [Extended containers](#extended-containers)
+    - [AttestationData](#attestationdata)
+    - [Attestation](#attestation)
+- [Helper functions](#helper-functions)
+  - [Beacon state accessors](#beacon-state-accessors)
+    - [Modified `get_attestation_index`](#modified-get_attestation_index)
+
+<!-- END doctoc generated TOC please keep comment here to allow auto update -->
+<!-- /TOC -->
+
+## Introduction
+
+This is the beacon chain specification to move the attestation committee index outside of the signed message. For motivation, refer to [EIP-7549](https://eips.ethereum.org/EIPS/eip-7549).
+
+*Note:* This specification is built upon [Deneb](../../deneb/beacon_chain.md) and is under active development.
+
+## Containers
+
+### Extended containers
+
+#### AttestationData
+
+```python
+class AttestationData(Container):
+    slot: Slot
+    # index: CommitteeIndex  # [Modified in EIP7549]
+    # LMD GHOST vote
+    beacon_block_root: Root
+    # FFG vote
+    source: Checkpoint
+    target: Checkpoint
+```
+
+#### Attestation
+
+```python
+class Attestation(Container):
+    aggregation_bits: Bitlist[MAX_VALIDATORS_PER_COMMITTEE]
+    data: AttestationData
+    index: CommitteeIndex  # [New in EIP7549]
+    signature: BLSSignature
+```
+
+## Helper functions
+
+### Beacon state accessors
+
+#### Modified `get_attestation_index`
+
+```python
+def get_attestation_index(attestation: Attestation) -> CommitteeIndex:
+    return attestation.index
+```
+

specs/altair/beacon-chain.md

@@ -496,7 +496,7 @@ 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, data, attestation.aggregation_bits):
+    for index in get_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/altair/fork.md

@@ -69,7 +69,7 @@ def translate_participation(state: BeaconState, pending_attestations: Sequence[p
 
         # Apply flags to all attesting validators
         epoch_participation = state.previous_epoch_participation
-        for index in get_attesting_indices(state, data, attestation.aggregation_bits):
+        for index in get_attesting_indices(state, attestation):
             for flag_index in participation_flag_indices:
                 epoch_participation[index] = add_flag(epoch_participation[index], flag_index)
 

specs/deneb/beacon-chain.md

@@ -316,12 +316,13 @@ def verify_and_notify_new_payload(self: ExecutionEngine,
 ```python
 def process_attestation(state: BeaconState, attestation: Attestation) -> None:
     data = attestation.data
+    index = get_attestation_index(attestation)
     assert data.target.epoch in (get_previous_epoch(state), get_current_epoch(state))
     assert data.target.epoch == compute_epoch_at_slot(data.slot)
     assert data.slot + MIN_ATTESTATION_INCLUSION_DELAY <= state.slot  # [Modified in Deneb:EIP7045]
-    assert data.index < get_committee_count_per_slot(state, data.target.epoch)
+    assert index < get_committee_count_per_slot(state, data.target.epoch)
 
-    committee = get_beacon_committee(state, data.slot, data.index)
+    committee = get_beacon_committee(state, data.slot, index)
     assert len(attestation.aggregation_bits) == len(committee)
 
     # Participation flag indices
@@ -337,7 +338,7 @@ 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, data, attestation.aggregation_bits):
+    for index in get_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/phase0/beacon-chain.md

@@ -100,6 +100,7 @@
     - [`get_domain`](#get_domain)
     - [`get_indexed_attestation`](#get_indexed_attestation)
     - [`get_attesting_indices`](#get_attesting_indices)
+    - [`get_attestation_index`](#get_attestation_index)
   - [Beacon state mutators](#beacon-state-mutators)
     - [`increase_balance`](#increase_balance)
     - [`decrease_balance`](#decrease_balance)
@@ -1082,7 +1083,7 @@ def get_indexed_attestation(state: BeaconState, attestation: Attestation) -> Ind
     """
     Return the indexed attestation corresponding to ``attestation``.
     """
-    attesting_indices = get_attesting_indices(state, attestation.data, attestation.aggregation_bits)
+    attesting_indices = get_attesting_indices(state, attestation)
 
     return IndexedAttestation(
         attesting_indices=sorted(attesting_indices),
@@ -1094,14 +1095,19 @@ def get_indexed_attestation(state: BeaconState, attestation: Attestation) -> Ind
 #### `get_attesting_indices`
 
 ```python
-def get_attesting_indices(state: BeaconState,
-                          data: AttestationData,
-                          bits: Bitlist[MAX_VALIDATORS_PER_COMMITTEE]) -> Set[ValidatorIndex]:
+def get_attesting_indices(state: BeaconState, attestation: Attestation) -> Set[ValidatorIndex]:
     """
     Return the set of attesting indices corresponding to ``data`` and ``bits``.
     """
-    committee = get_beacon_committee(state, data.slot, data.index)
-    return set(index for i, index in enumerate(committee) if bits[i])
+    committee = get_beacon_committee(state, attestation.data.slot, get_attestation_index(attestation))
+    return set(index for i, index in enumerate(committee) if attestation.aggregation_bits[i])
+```
+
+#### `get_attestation_index`
+
+```python
+def get_attestation_index(attestation: Attestation) -> CommitteeIndex:
+    return attestation.data.index
 ```
 
 ### Beacon state mutators
@@ -1339,7 +1345,7 @@ def get_unslashed_attesting_indices(state: BeaconState,
                                     attestations: Sequence[PendingAttestation]) -> Set[ValidatorIndex]:
     output = set()  # type: Set[ValidatorIndex]
     for a in attestations:
-        output = output.union(get_attesting_indices(state, a.data, a.aggregation_bits))
+        output = output.union(get_attesting_indices(state, a))
     return set(filter(lambda index: not state.validators[index].slashed, output))
 ```
 
@@ -1512,7 +1518,7 @@ def get_inclusion_delay_deltas(state: BeaconState) -> Tuple[Sequence[Gwei], Sequ
     for index in get_unslashed_attesting_indices(state, matching_source_attestations):
         attestation = min([
             a for a in matching_source_attestations
-            if index in get_attesting_indices(state, a.data, a.aggregation_bits)
+            if index in get_attesting_indices(state, a)
         ], key=lambda a: a.inclusion_delay)
         rewards[attestation.proposer_index] += get_proposer_reward(state, index)
         max_attester_reward = Gwei(get_base_reward(state, index) - get_proposer_reward(state, index))

specs/phase0/p2p-interface.md

@@ -354,7 +354,7 @@ The `beacon_aggregate_and_proof` topic is used to propagate aggregated attestati
 to subscribing nodes (typically validators) to be included in future blocks.
 
 The following validations MUST pass before forwarding the `signed_aggregate_and_proof` on the network.
-(We define the following for convenience -- `aggregate_and_proof = signed_aggregate_and_proof.message` and `aggregate = aggregate_and_proof.aggregate`)
+(We define the following for convenience -- `aggregate_and_proof = signed_aggregate_and_proof.message`, `aggregate = aggregate_and_proof.aggregate` and `index = get_attestation_index(aggregate)`)
 - _[IGNORE]_ `aggregate.data.slot` is within the last `ATTESTATION_PROPAGATION_SLOT_RANGE` slots (with a `MAXIMUM_GOSSIP_CLOCK_DISPARITY` allowance) --
   i.e. `aggregate.data.slot + ATTESTATION_PROPAGATION_SLOT_RANGE >= current_slot >= aggregate.data.slot`
   (a client MAY queue future aggregates for processing at the appropriate slot).
@@ -364,12 +364,11 @@ The following validations MUST pass before forwarding the `signed_aggregate_and_
   (via aggregate gossip, within a verified block, or through the creation of an equivalent aggregate locally).
 - _[IGNORE]_ The `aggregate` is the first valid aggregate received for the aggregator
   with index `aggregate_and_proof.aggregator_index` for the epoch `aggregate.data.target.epoch`.
-- _[REJECT]_ The attestation has participants --
-  that is, `len(get_attesting_indices(state, aggregate.data, aggregate.aggregation_bits)) >= 1`.
+- _[REJECT]_ The attestation has participants -- that is, `len(get_attesting_indices(state, aggregate)) >= 1`.
 - _[REJECT]_ `aggregate_and_proof.selection_proof` selects the validator as an aggregator for the slot --
-  i.e. `is_aggregator(state, aggregate.data.slot, aggregate.data.index, aggregate_and_proof.selection_proof)` returns `True`.
+  i.e. `is_aggregator(state, aggregate.data.slot, index, aggregate_and_proof.selection_proof)` returns `True`.
 - _[REJECT]_ The aggregator's validator index is within the committee --
-  i.e. `aggregate_and_proof.aggregator_index in get_beacon_committee(state, aggregate.data.slot, aggregate.data.index)`.
+  i.e. `aggregate_and_proof.aggregator_index in get_beacon_committee(state, aggregate.data.slot, index)`.
 - _[REJECT]_ The `aggregate_and_proof.selection_proof` is a valid signature
   of the `aggregate.data.slot` by the validator with index `aggregate_and_proof.aggregator_index`.
 - _[REJECT]_ The aggregator signature, `signed_aggregate_and_proof.signature`, is valid.
@@ -425,9 +424,10 @@ The `beacon_attestation_{subnet_id}` topics are used to propagate unaggregated a
 to the subnet `subnet_id` (typically beacon and persistent committees) to be aggregated before being gossiped to `beacon_aggregate_and_proof`.
 
 The following validations MUST pass before forwarding the `attestation` on the subnet.
-- _[REJECT]_ The committee index is within the expected range -- i.e. `data.index < get_committee_count_per_slot(state, data.target.epoch)`.
+(We define the following for convenience -- `index = get_attestation_index(attestation)`)
+- _[REJECT]_ The committee index is within the expected range -- i.e. `index < get_committee_count_per_slot(state, data.target.epoch)`.
 - _[REJECT]_ The attestation is for the correct subnet --
-  i.e. `compute_subnet_for_attestation(committees_per_slot, attestation.data.slot, attestation.data.index) == subnet_id`,
+  i.e. `compute_subnet_for_attestation(committees_per_slot, attestation.data.slot, index) == subnet_id`,
   where `committees_per_slot = get_committee_count_per_slot(state, attestation.data.target.epoch)`,
   which may be pre-computed along with the committee information for the signature check.
 - _[IGNORE]_ `attestation.data.slot` is within the last `ATTESTATION_PROPAGATION_SLOT_RANGE` slots
@@ -439,7 +439,7 @@ The following validations MUST pass before forwarding the `attestation` on the s
 - _[REJECT]_ The attestation is unaggregated --
   that is, it has exactly one participating validator (`len([bit for bit in attestation.aggregation_bits if bit]) == 1`, i.e. exactly 1 bit is set).
 - _[REJECT]_ The number of aggregation bits matches the committee size -- i.e.
-  `len(attestation.aggregation_bits) == len(get_beacon_committee(state, data.slot, data.index))`.
+  `len(attestation.aggregation_bits) == len(get_beacon_committee(state, data.slot, index))`.
 - _[IGNORE]_ There has been no other valid attestation seen on an attestation subnet
   that has an identical `attestation.data.target.epoch` and participating validator index.
 - _[REJECT]_ The signature of `attestation` is valid.

specs/phase0/validator.md

@@ -494,7 +494,7 @@ Set `attestation.data = attestation_data` where `attestation_data` is the `Attes
 
 - Let `attestation.aggregation_bits` be a `Bitlist[MAX_VALIDATORS_PER_COMMITTEE]` of length `len(committee)`, where the bit of the index of the validator in the `committee` is set to `0b1`.
 
-*Note*: Calling `get_attesting_indices(state, attestation.data, attestation.aggregation_bits)` should return a list of length equal to 1, containing `validator_index`.
+*Note*: Calling `get_attesting_indices(state, attestation)` should return a list of length equal to 1, containing `validator_index`.
 
 ##### Aggregate signature
 

tests/core/pyspec/eth2spec/test/helpers/attestations.py

@@ -104,11 +104,7 @@ def get_valid_attestation(spec,
 
     attestation_data = build_attestation_data(spec, state, slot=slot, index=index, beacon_block_root=beacon_block_root)
 
-    beacon_committee = spec.get_beacon_committee(
-        state,
-        attestation_data.slot,
-        attestation_data.index,
-    )
+    beacon_committee = spec.get_beacon_committee(state, slot, index)
 
     committee_size = len(beacon_committee)
     aggregation_bits = Bitlist[spec.MAX_VALIDATORS_PER_COMMITTEE](*([0] * committee_size))
@@ -144,11 +140,7 @@ def sign_indexed_attestation(spec, state, indexed_attestation):
 
 
 def sign_attestation(spec, state, attestation):
-    participants = spec.get_attesting_indices(
-        state,
-        attestation.data,
-        attestation.aggregation_bits,
-    )
+    participants = spec.get_attesting_indices(state, attestation)
 
     attestation.signature = sign_aggregate_attestation(spec, state, attestation.data, participants)
 
@@ -175,7 +167,7 @@ def fill_aggregate_attestation(spec, state, attestation, signed=False, filter_pa
     beacon_committee = spec.get_beacon_committee(
         state,
         attestation.data.slot,
-        attestation.data.index,
+        spec.get_attestation_index(attestation),
     )
     # By default, have everyone participate
     participants = set(beacon_committee)

tests/core/pyspec/eth2spec/test/helpers/rewards.py

@@ -201,7 +201,7 @@ def run_get_inclusion_delay_deltas(spec, state):
             # Track proposer of earliest included attestation for the validator defined by index
             earliest_attestation = min([
                 a for a in eligible_attestations
-                if index in spec.get_attesting_indices(state, a.data, a.aggregation_bits)
+                if index in spec.get_attesting_indices(state, a)
             ], key=lambda a: a.inclusion_delay)
             rewarded_proposer_indices.add(earliest_attestation.proposer_index)
 

tests/core/pyspec/eth2spec/test/phase0/block_processing/test_process_attestation.py

@@ -236,11 +236,7 @@ def test_invalid_future_target_epoch(spec, state):
 
     attestation = get_valid_attestation(spec, state)
 
-    participants = spec.get_attesting_indices(
-        state,
-        attestation.data,
-        attestation.aggregation_bits
-    )
+    participants = spec.get_attesting_indices(state, attestation)
     attestation.data.target.epoch = spec.get_current_epoch(state) + 1  # target epoch will be too new to handle
 
     # manually add signature for correct participants