EIP-7549: Move committee index outside Attestation

pysetup/spec_builders/phase0.py

@@ -98,8 +98,8 @@ def wrapper(*args, **kw):  # type: ignore
 
 _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 +1,146 @@
+# 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)
+- [Preset](#preset)
+- [Containers](#containers)
+  - [Modified containers](#modified-containers)
+    - [Attestation](#attestation)
+    - [IndexedAttestation](#indexedattestation)
+- [Helper functions](#helper-functions)
+  - [Misc](#misc)
+    - [`get_committee_indices`](#get_committee_indices)
+  - [Beacon state accessors](#beacon-state-accessors)
+    - [New `get_committee_attesters`](#new-get_committee_attesters)
+    - [Modified `get_attesting_indices`](#modified-get_attesting_indices)
+  - [Block processing](#block-processing)
+    - [Modified `process_attestation`](#modified-process_attestation)
+
+<!-- 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.
+
+## Preset
+
+| Name | Value | Description |
+| - | - | - |
+| `MAX_ATTESTER_SLASHINGS` | `2**0` (= 1) |
+| `MAX_ATTESTATIONS`       | `2**3` (= 8) |
+
+## Containers
+
+### Modified containers
+
+#### Attestation
+
+```python
+class Attestation(Container):
+     aggregation_bits: List[Bitlist[MAX_VALIDATORS_PER_COMMITTEE], MAX_COMMITTEES_PER_SLOT]  # [Modified in EIP7549]
+     data: AttestationData
+     committee_bits: Bitvector[MAX_COMMITTEES_PER_SLOT]  # [New in EIP7549]
+     signature: BLSSignature
+```
+
+#### IndexedAttestation
+
+```python
+class IndexedAttestation(Container):
+    attesting_indices: List[ValidatorIndex, MAX_VALIDATORS_PER_COMMITTEE * MAX_COMMITTEES_PER_SLOT]  # [Modified in EIP7549]
+    data: AttestationData
+    signature: BLSSignature
+```
+
+## Helper functions
+
+### Misc
+
+#### `get_committee_indices`
+
+```python
+def get_committee_indices(commitee_bits: Bitvector) -> List[CommitteeIndex]:
+     return [CommitteeIndex(index) for bit, index in enumerate(commitee_bits) if bit]
+```
+
+### Beacon state accessors
+
+#### New `get_committee_attesters`
+
+```python
+def get_committee_attesters(state: BeaconState, attesting_bits: Bitlist, index: CommitteeIndex) -> Set[ValidatorIndex]:
+    committee = get_beacon_committee(state, data.slot, index)
+    return set(index for i, index in enumerate(committee) if attesting_bits[i])
+```
+
+#### Modified `get_attesting_indices`
+
+```python
+def get_attesting_indices(state: BeaconState, attestation: Attestation) -> Set[ValidatorIndex]:
+    """
+    Return the set of attesting indices corresponding to ``aggregation_bits`` and ``committee_bits``.
+    """
+
+    output = set()
+    committee_indices = get_committee_indices(attestation.committee_bits)
+    for index in committee_indices:
+        attesting_bits = attestation.attesting_bits[index]
+        committee_attesters = get_committee_attesters(state, attesting_bits, index)
+        output = output.union(committee_attesters)
+
+    return output
+```
+
+### Block processing
+
+#### Modified `process_attestation`
+
+```python
+def process_attestation(state: BeaconState, attestation: Attestation) -> 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)
+    assert data.slot + MIN_ATTESTATION_INCLUSION_DELAY <= state.slot
+
+    # [Modified in EIP7549]
+    assert data.index == 0
+    committee_indices = get_committee_indices(attestation.committee_bits)
+    assert len(committee_indices) > 0
+    assert len(committee_indices) == len(attestation.aggregation_bits)
+    for index in committee_indices:
+        assert index < get_committee_count_per_slot(state, data.target.epoch)
+        committee = get_beacon_committee(state, data.slot, index)
+        assert len(attestation.aggregation_bits[index]) == len(committee)
+
+    # Participation flag indices
+    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))
+
+    # Update epoch participation flags
+    if data.target.epoch == get_current_epoch(state):
+        epoch_participation = state.current_epoch_participation
+    else:
+        epoch_participation = state.previous_epoch_participation
+
+    proposer_reward_numerator = 0
+    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)
+                proposer_reward_numerator += get_base_reward(state, index) * weight
+
+    # Reward proposer
+    proposer_reward_denominator = (WEIGHT_DENOMINATOR - PROPOSER_WEIGHT) * WEIGHT_DENOMINATOR // PROPOSER_WEIGHT
+    proposer_reward = Gwei(proposer_reward_numerator // proposer_reward_denominator)
+    increase_balance(state, get_beacon_proposer_index(state), proposer_reward)
+```

specs/_features/eip7549/p2p-interface.md

@@ -0,0 +1,54 @@
+# EIP-7549 -- Networking
+
+This document contains the consensus-layer networking specification for EIP-7549.
+
+The specification of these changes continues in the same format as the network specifications of previous upgrades, and assumes them as pre-requisite.
+
+## 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 -->
+
+- [Modifications in EIP-7549](#modifications-in-eip-7549)
+  - [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 -->
+
+## Modifications in EIP-7549
+
+### The gossip domain: gossipsub
+
+#### Topics and messages
+
+The `beacon_aggregate_and_proof` and `beacon_attestation_{subnet_id}` topics are modified to support the gossip of a new attestation type.
+
+##### Global topics
+
+###### `beacon_aggregate_and_proof`
+
+*[Modified in EIP7549]*
+
+The following convenience variables are re-defined
+- `index = get_committee_indices(aggregate.committee_bits)[0]`
+- `aggregation_bits = aggregate.aggregation_bits[0]`
+
+The following validations are added:
+* [REJECT] `len(committee_indices) == len(aggregate.attestation_bits) == 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]`
+- `aggregation_bits = attestation.aggregation_bits[0]`
+
+The following validations are added:
+* [REJECT] `len(committee_indices) == len(attestation.attestation_bits) == 1`, where `committee_indices = get_committee_indices(attestation)`.
+* [REJECT] `attestation.data.index == 0`
+

specs/_features/eip7549/validator.md

@@ -0,0 +1,49 @@
+# Deneb -- Honest Validator
+
+## 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 -->
+
+- [Modifications in EIP-7549](#modifications-in-eip-7549)
+  - [Block proposal](#block-proposal)
+    - [Constructing the `BeaconBlockBody`](#constructing-the-beaconblockbody)
+      - [Attestations](#attestations)
+  - [Attesting](#attesting)
+    - [Construct attestation](#construct-attestation)
+  - [Attestation aggregation](#attestation-aggregation)
+    - [Construct aggregate](#construct-aggregate)
+
+<!-- END doctoc generated TOC please keep comment here to allow auto update -->
+<!-- /TOC -->
+
+## Modifications in EIP-7549
+
+### Block proposal
+
+#### Constructing the `BeaconBlockBody`
+
+##### Attestations
+
+Attestations received from aggregators with disjoint `committee_bits` sets and equal `AttestationData` SHOULD be consolidated into a single `Attestation` object.
+
+### Attesting
+
+#### Construct attestation
+
+- Set `attestation_data.index = 0`.
+- Let `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`.
+- Set `attestation.aggregation_bits = [aggregation_bits]`, a list of length 1
+
+*Note*: Calling `get_attesting_indices(state, attestation)` should return a list of length equal to 1, containing `validator_index`.
+
+### Attestation aggregation
+
+#### Construct aggregate
+
+- Set `attestation_data.index = 0`.
+- Let `aggregation_bits` be a `Bitlist[MAX_VALIDATORS_PER_COMMITTEE]` of length `len(committee)`, where each bit set from each individual attestation is set to `0b1`.
+- Set `attestation.aggregation_bits = [aggregation_bits]`, a list of length 1
+
+

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

@@ -337,7 +337,7 @@ 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

@@ -1086,7 +1086,7 @@ 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),
@@ -1098,14 +1098,12 @@ 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, attestation.data.index)
+    return set(index for i, index in enumerate(committee) if attestation.aggregation_bits[i])
 ```
 
 ### Beacon state mutators
@@ -1343,7 +1341,7 @@ 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))
 ```
 
@@ -1516,7 +1514,7 @@ 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))