675 lines
29 KiB
Markdown
675 lines
29 KiB
Markdown
# Ethereum 2.0 Altair Beacon chain changes
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## Table of contents
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<!-- TOC -->
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<!-- START doctoc generated TOC please keep comment here to allow auto update -->
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<!-- DON'T EDIT THIS SECTION, INSTEAD RE-RUN doctoc TO UPDATE -->
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- [Introduction](#introduction)
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- [Custom types](#custom-types)
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- [Constants](#constants)
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- [Participation flag indices](#participation-flag-indices)
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- [Participation flag fractions](#participation-flag-fractions)
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- [Misc](#misc)
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- [Configuration](#configuration)
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- [Updated penalty values](#updated-penalty-values)
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- [Misc](#misc-1)
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- [Time parameters](#time-parameters)
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- [Domain types](#domain-types)
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- [Containers](#containers)
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- [Modified containers](#modified-containers)
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- [`BeaconBlockBody`](#beaconblockbody)
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- [`BeaconState`](#beaconstate)
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- [New containers](#new-containers)
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- [`SyncCommittee`](#synccommittee)
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- [Helper functions](#helper-functions)
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- [`Predicates`](#predicates)
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- [`eth2_fast_aggregate_verify`](#eth2_fast_aggregate_verify)
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- [Misc](#misc-2)
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- [`get_flag_indices_and_numerators`](#get_flag_indices_and_numerators)
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- [`add_flag`](#add_flag)
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- [`has_flag`](#has_flag)
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- [Beacon state accessors](#beacon-state-accessors)
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- [`get_sync_committee_indices`](#get_sync_committee_indices)
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- [`get_sync_committee`](#get_sync_committee)
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- [`get_base_reward`](#get_base_reward)
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- [`get_unslashed_participating_indices`](#get_unslashed_participating_indices)
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- [`get_flag_index_deltas`](#get_flag_index_deltas)
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- [Modified `get_inactivity_penalty_deltas`](#modified-get_inactivity_penalty_deltas)
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- [Beacon state mutators](#beacon-state-mutators)
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- [Modified `slash_validator`](#modified-slash_validator)
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- [Block processing](#block-processing)
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- [Modified `process_attestation`](#modified-process_attestation)
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- [Modified `process_deposit`](#modified-process_deposit)
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- [Sync committee processing](#sync-committee-processing)
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- [Epoch processing](#epoch-processing)
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- [Justification and finalization](#justification-and-finalization)
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- [Inactivity scores](#inactivity-scores)
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- [Rewards and penalties](#rewards-and-penalties)
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- [Slashings](#slashings)
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- [Participation flags updates](#participation-flags-updates)
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- [Sync committee updates](#sync-committee-updates)
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<!-- END doctoc generated TOC please keep comment here to allow auto update -->
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<!-- /TOC -->
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## Introduction
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Altair is the first beacon chain hard fork. Its main features are:
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* sync committees to support light clients
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* incentive accounting reforms to reduce spec complexity
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* penalty parameter updates to move them to their planned maximally punitive configuration
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## Custom types
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| Name | SSZ equivalent | Description |
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| - | - | - |
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| `ParticipationFlags` | `uint8` | a succinct representation of 8 boolean participation flags |
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## Constants
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### Participation flag indices
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| Name | Value |
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| - | - |
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| `TIMELY_HEAD_FLAG_INDEX` | `0` |
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| `TIMELY_SOURCE_FLAG_INDEX` | `1` |
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| `TIMELY_TARGET_FLAG_INDEX` | `2` |
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### Participation flag fractions
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| Name | Value |
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| - | - |
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| `TIMELY_HEAD_FLAG_NUMERATOR` | `12` |
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| `TIMELY_SOURCE_FLAG_NUMERATOR` | `12` |
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| `TIMELY_TARGET_FLAG_NUMERATOR` | `32` |
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| `FLAG_DENOMINATOR` | `64` |
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**Note**: The sum of the participatition flag fractions (7/8) plus the proposer reward fraction (1/8) equals 1.
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### Misc
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| Name | Value |
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| - | - |
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| `G2_POINT_AT_INFINITY` | `BLSSignature(b'\xc0' + b'\x00' * 95)` |
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## Configuration
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### Updated penalty values
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This patch updates a few configuration values to move penalty parameters toward their final, maxmium security values.
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*Note*: The spec does *not* override previous configuration values but instead creates new values and replaces usage throughout.
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| Name | Value |
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| - | - |
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| `ALTAIR_INACTIVITY_PENALTY_QUOTIENT` | `uint64(3 * 2**24)` (= 50,331,648) |
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| `ALTAIR_MIN_SLASHING_PENALTY_QUOTIENT` | `uint64(2**6)` (= 64) |
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| `ALTAIR_PROPORTIONAL_SLASHING_MULTIPLIER` | `uint64(2)` |
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### Misc
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| Name | Value |
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| - | - |
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| `SYNC_COMMITTEE_SIZE` | `uint64(2**10)` (= 1,024) |
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| `SYNC_SUBCOMMITTEE_SIZE` | `uint64(2**6)` (= 64) |
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| `INACTIVITY_SCORE_BIAS` | `uint64(4)` |
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### Time parameters
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| Name | Value | Unit | Duration |
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| - | - | :-: | :-: |
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| `EPOCHS_PER_SYNC_COMMITTEE_PERIOD` | `Epoch(2**8)` (= 256) | epochs | ~27 hours |
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### Domain types
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| Name | Value |
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| - | - |
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| `DOMAIN_SYNC_COMMITTEE` | `DomainType('0x07000000')` |
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## Containers
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### Modified containers
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#### `BeaconBlockBody`
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```python
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class BeaconBlockBody(Container):
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randao_reveal: BLSSignature
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eth1_data: Eth1Data # Eth1 data vote
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graffiti: Bytes32 # Arbitrary data
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# Operations
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proposer_slashings: List[ProposerSlashing, MAX_PROPOSER_SLASHINGS]
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attester_slashings: List[AttesterSlashing, MAX_ATTESTER_SLASHINGS]
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attestations: List[Attestation, MAX_ATTESTATIONS]
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deposits: List[Deposit, MAX_DEPOSITS]
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voluntary_exits: List[SignedVoluntaryExit, MAX_VOLUNTARY_EXITS]
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# Sync committee aggregate signature
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sync_committee_bits: Bitvector[SYNC_COMMITTEE_SIZE] # [New in Altair]
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sync_committee_signature: BLSSignature # [New in Altair]
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```
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#### `BeaconState`
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```python
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class BeaconState(Container):
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# Versioning
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genesis_time: uint64
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genesis_validators_root: Root
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slot: Slot
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fork: Fork
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# History
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latest_block_header: BeaconBlockHeader
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block_roots: Vector[Root, SLOTS_PER_HISTORICAL_ROOT]
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state_roots: Vector[Root, SLOTS_PER_HISTORICAL_ROOT]
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historical_roots: List[Root, HISTORICAL_ROOTS_LIMIT]
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# Eth1
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eth1_data: Eth1Data
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eth1_data_votes: List[Eth1Data, EPOCHS_PER_ETH1_VOTING_PERIOD * SLOTS_PER_EPOCH]
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eth1_deposit_index: uint64
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# Registry
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validators: List[Validator, VALIDATOR_REGISTRY_LIMIT]
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balances: List[Gwei, VALIDATOR_REGISTRY_LIMIT]
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# Randomness
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randao_mixes: Vector[Bytes32, EPOCHS_PER_HISTORICAL_VECTOR]
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# Slashings
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slashings: Vector[Gwei, EPOCHS_PER_SLASHINGS_VECTOR] # Per-epoch sums of slashed effective balances
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# Participation
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previous_epoch_participation: List[ParticipationFlags, VALIDATOR_REGISTRY_LIMIT] # [Modified in Altair]
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current_epoch_participation: List[ParticipationFlags, VALIDATOR_REGISTRY_LIMIT] # [Modified in Altair]
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# Finality
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justification_bits: Bitvector[JUSTIFICATION_BITS_LENGTH] # Bit set for every recent justified epoch
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previous_justified_checkpoint: Checkpoint
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current_justified_checkpoint: Checkpoint
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finalized_checkpoint: Checkpoint
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# Inactivity
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inactivity_scores: List[uint64, VALIDATOR_REGISTRY_LIMIT] # [New in Altair]
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# Sync
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current_sync_committee: SyncCommittee # [New in Altair]
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next_sync_committee: SyncCommittee # [New in Altair]
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```
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### New containers
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#### `SyncCommittee`
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```python
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class SyncCommittee(Container):
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pubkeys: Vector[BLSPubkey, SYNC_COMMITTEE_SIZE]
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pubkey_aggregates: Vector[BLSPubkey, SYNC_COMMITTEE_SIZE // SYNC_SUBCOMMITTEE_SIZE]
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```
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## Helper functions
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### `Predicates`
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#### `eth2_fast_aggregate_verify`
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```python
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def eth2_fast_aggregate_verify(pubkeys: Sequence[BLSPubkey], message: Bytes32, signature: BLSSignature) -> bool:
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"""
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Wrapper to ``bls.FastAggregateVerify`` accepting the ``G2_POINT_AT_INFINITY`` signature when ``pubkeys`` is empty.
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"""
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if len(pubkeys) == 0 and signature == G2_POINT_AT_INFINITY:
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return True
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return bls.FastAggregateVerify(pubkeys, message, signature)
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```
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### Misc
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#### `get_flag_indices_and_numerators`
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```python
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def get_flag_indices_and_numerators() -> Sequence[Tuple[int, int]]:
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return (
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(TIMELY_HEAD_FLAG_INDEX, TIMELY_HEAD_FLAG_NUMERATOR),
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(TIMELY_SOURCE_FLAG_INDEX, TIMELY_SOURCE_FLAG_NUMERATOR),
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(TIMELY_TARGET_FLAG_INDEX, TIMELY_TARGET_FLAG_NUMERATOR),
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)
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```
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#### `add_flag`
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```python
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def add_flag(flags: ParticipationFlags, flag_index: int) -> ParticipationFlags:
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flag = ParticipationFlags(2**flag_index)
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return flags | flag
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```
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#### `has_flag`
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```python
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def has_flag(flags: ParticipationFlags, flag_index: int) -> bool:
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flag = ParticipationFlags(2**flag_index)
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return flags & flag == flag
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```
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### Beacon state accessors
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#### `get_sync_committee_indices`
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```python
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def get_sync_committee_indices(state: BeaconState, epoch: Epoch) -> Sequence[ValidatorIndex]:
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"""
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Return the sequence of sync committee indices (which may include duplicate indices) for a given state and epoch.
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"""
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MAX_RANDOM_BYTE = 2**8 - 1
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base_epoch = Epoch((max(epoch // EPOCHS_PER_SYNC_COMMITTEE_PERIOD, 1) - 1) * EPOCHS_PER_SYNC_COMMITTEE_PERIOD)
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active_validator_indices = get_active_validator_indices(state, base_epoch)
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active_validator_count = uint64(len(active_validator_indices))
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seed = get_seed(state, base_epoch, DOMAIN_SYNC_COMMITTEE)
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i = 0
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sync_committee_indices: List[ValidatorIndex] = []
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while len(sync_committee_indices) < SYNC_COMMITTEE_SIZE:
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shuffled_index = compute_shuffled_index(uint64(i % active_validator_count), active_validator_count, seed)
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candidate_index = active_validator_indices[shuffled_index]
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random_byte = hash(seed + uint_to_bytes(uint64(i // 32)))[i % 32]
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effective_balance = state.validators[candidate_index].effective_balance
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if effective_balance * MAX_RANDOM_BYTE >= MAX_EFFECTIVE_BALANCE * random_byte: # Sample with replacement
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sync_committee_indices.append(candidate_index)
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i += 1
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return sync_committee_indices
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```
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#### `get_sync_committee`
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```python
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def get_sync_committee(state: BeaconState, epoch: Epoch) -> SyncCommittee:
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"""
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Return the sync committee for a given state and epoch.
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"""
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indices = get_sync_committee_indices(state, epoch)
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pubkeys = [state.validators[index].pubkey for index in indices]
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subcommitees = [pubkeys[i:i + SYNC_SUBCOMMITTEE_SIZE] for i in range(0, len(pubkeys), SYNC_SUBCOMMITTEE_SIZE)]
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pubkey_aggregates = [bls.AggregatePKs(subcommitee) for subcommitee in subcommitees]
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return SyncCommittee(pubkeys=pubkeys, pubkey_aggregates=pubkey_aggregates)
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```
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#### `get_base_reward`
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*Note*: The function `get_base_reward` is modified with the removal of `BASE_REWARDS_PER_EPOCH`.
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```python
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def get_base_reward(state: BeaconState, index: ValidatorIndex) -> Gwei:
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total_balance = get_total_active_balance(state)
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effective_balance = state.validators[index].effective_balance
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return Gwei(effective_balance * BASE_REWARD_FACTOR // integer_squareroot(total_balance))
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```
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#### `get_unslashed_participating_indices`
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```python
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def get_unslashed_participating_indices(state: BeaconState, flag_index: int, epoch: Epoch) -> Set[ValidatorIndex]:
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"""
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Return the active and unslashed validator indices for the given epoch and flag index.
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"""
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assert epoch in (get_previous_epoch(state), get_current_epoch(state))
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if epoch == get_current_epoch(state):
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epoch_participation = state.current_epoch_participation
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else:
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epoch_participation = state.previous_epoch_participation
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active_validator_indices = get_active_validator_indices(state, epoch)
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participating_indices = [i for i in active_validator_indices if has_flag(epoch_participation[i], flag_index)]
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return set(filter(lambda index: not state.validators[index].slashed, participating_indices))
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```
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#### `get_flag_index_deltas`
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```python
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def get_flag_index_deltas(state: BeaconState,
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flag_index: int,
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numerator: uint64) -> Tuple[Sequence[Gwei], Sequence[Gwei]]:
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"""
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Return the deltas for a given flag index by scanning through the participation flags.
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"""
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rewards = [Gwei(0)] * len(state.validators)
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penalties = [Gwei(0)] * len(state.validators)
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unslashed_participating_indices = get_unslashed_participating_indices(state, flag_index, get_previous_epoch(state))
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increment = EFFECTIVE_BALANCE_INCREMENT # Factored out from balances to avoid uint64 overflow
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unslashed_participating_increments = get_total_balance(state, unslashed_participating_indices) // increment
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active_increments = get_total_active_balance(state) // increment
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for index in get_eligible_validator_indices(state):
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base_reward = get_base_reward(state, index)
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if index in unslashed_participating_indices:
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if is_in_inactivity_leak(state):
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# This flag reward cancels the inactivity penalty corresponding to the flag index
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rewards[index] += Gwei(base_reward * numerator // FLAG_DENOMINATOR)
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else:
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reward_numerator = base_reward * numerator * unslashed_participating_increments
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rewards[index] += Gwei(reward_numerator // (active_increments * FLAG_DENOMINATOR))
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else:
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penalties[index] += Gwei(base_reward * numerator // FLAG_DENOMINATOR)
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return rewards, penalties
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```
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#### Modified `get_inactivity_penalty_deltas`
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*Note*: The function `get_inactivity_penalty_deltas` is modified in the selection of matching target indices
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and the removal of `BASE_REWARDS_PER_EPOCH`.
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```python
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def get_inactivity_penalty_deltas(state: BeaconState) -> Tuple[Sequence[Gwei], Sequence[Gwei]]:
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"""
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Return the inactivity penalty deltas by considering timely target participation flags and inactivity scores.
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"""
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rewards = [Gwei(0) for _ in range(len(state.validators))]
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penalties = [Gwei(0) for _ in range(len(state.validators))]
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if is_in_inactivity_leak(state):
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previous_epoch = get_previous_epoch(state)
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matching_target_indices = get_unslashed_participating_indices(state, TIMELY_TARGET_FLAG_INDEX, previous_epoch)
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for index in get_eligible_validator_indices(state):
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for (_, numerator) in get_flag_indices_and_numerators():
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# This inactivity penalty cancels the flag reward corresponding to the flag index
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penalties[index] += Gwei(get_base_reward(state, index) * numerator // FLAG_DENOMINATOR)
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if index not in matching_target_indices:
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penalty_numerator = state.validators[index].effective_balance * state.inactivity_scores[index]
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penalty_denominator = INACTIVITY_SCORE_BIAS * ALTAIR_INACTIVITY_PENALTY_QUOTIENT
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penalties[index] += Gwei(penalty_numerator // penalty_denominator)
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return rewards, penalties
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```
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### Beacon state mutators
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#### Modified `slash_validator`
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*Note*: The function `slash_validator` is modified to use `ALTAIR_MIN_SLASHING_PENALTY_QUOTIENT`.
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```python
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def slash_validator(state: BeaconState,
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slashed_index: ValidatorIndex,
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whistleblower_index: ValidatorIndex=None) -> None:
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"""
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Slash the validator with index ``slashed_index``.
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"""
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epoch = get_current_epoch(state)
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initiate_validator_exit(state, slashed_index)
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validator = state.validators[slashed_index]
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validator.slashed = True
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validator.withdrawable_epoch = max(validator.withdrawable_epoch, Epoch(epoch + EPOCHS_PER_SLASHINGS_VECTOR))
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state.slashings[epoch % EPOCHS_PER_SLASHINGS_VECTOR] += validator.effective_balance
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decrease_balance(state, slashed_index, validator.effective_balance // ALTAIR_MIN_SLASHING_PENALTY_QUOTIENT)
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# Apply proposer and whistleblower rewards
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proposer_index = get_beacon_proposer_index(state)
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if whistleblower_index is None:
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whistleblower_index = proposer_index
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whistleblower_reward = Gwei(validator.effective_balance // WHISTLEBLOWER_REWARD_QUOTIENT)
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proposer_reward = Gwei(whistleblower_reward // PROPOSER_REWARD_QUOTIENT)
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increase_balance(state, proposer_index, proposer_reward)
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increase_balance(state, whistleblower_index, Gwei(whistleblower_reward - proposer_reward))
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```
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### Block processing
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```python
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def process_block(state: BeaconState, block: BeaconBlock) -> None:
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process_block_header(state, block)
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process_randao(state, block.body)
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process_eth1_data(state, block.body)
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process_operations(state, block.body) # [Modified in Altair]
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process_sync_committee(state, block.body) # [New in Altair]
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```
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#### Modified `process_attestation`
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*Note*: The function `process_attestation` is modified to do incentive accounting with epoch participation flags.
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```python
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def process_attestation(state: BeaconState, attestation: Attestation) -> None:
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data = attestation.data
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assert data.target.epoch in (get_previous_epoch(state), get_current_epoch(state))
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assert data.target.epoch == compute_epoch_at_slot(data.slot)
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assert data.slot + MIN_ATTESTATION_INCLUSION_DELAY <= state.slot <= data.slot + SLOTS_PER_EPOCH
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assert data.index < get_committee_count_per_slot(state, data.target.epoch)
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committee = get_beacon_committee(state, data.slot, data.index)
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assert len(attestation.aggregation_bits) == len(committee)
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if data.target.epoch == get_current_epoch(state):
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epoch_participation = state.current_epoch_participation
|
|
justified_checkpoint = state.current_justified_checkpoint
|
|
else:
|
|
epoch_participation = state.previous_epoch_participation
|
|
justified_checkpoint = state.previous_justified_checkpoint
|
|
|
|
# Matching roots
|
|
is_matching_head = data.beacon_block_root == get_block_root_at_slot(state, data.slot)
|
|
is_matching_source = data.source == justified_checkpoint
|
|
is_matching_target = data.target.root == get_block_root(state, data.target.epoch)
|
|
assert is_matching_source
|
|
|
|
# Verify signature
|
|
assert is_valid_indexed_attestation(state, get_indexed_attestation(state, attestation))
|
|
|
|
# Participation flag indices
|
|
participation_flag_indices = []
|
|
if is_matching_head and is_matching_target and state.slot <= data.slot + MIN_ATTESTATION_INCLUSION_DELAY:
|
|
participation_flag_indices.append(TIMELY_HEAD_FLAG_INDEX)
|
|
if is_matching_source and state.slot <= data.slot + integer_squareroot(SLOTS_PER_EPOCH):
|
|
participation_flag_indices.append(TIMELY_SOURCE_FLAG_INDEX)
|
|
if is_matching_target and state.slot <= data.slot + SLOTS_PER_EPOCH:
|
|
participation_flag_indices.append(TIMELY_TARGET_FLAG_INDEX)
|
|
|
|
# Update epoch participation flags
|
|
proposer_reward_numerator = 0
|
|
for index in get_attesting_indices(state, data, attestation.aggregation_bits):
|
|
for flag_index, flag_numerator in get_flag_indices_and_numerators():
|
|
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) * flag_numerator
|
|
|
|
# Reward proposer
|
|
proposer_reward = Gwei(proposer_reward_numerator // (FLAG_DENOMINATOR * PROPOSER_REWARD_QUOTIENT))
|
|
increase_balance(state, get_beacon_proposer_index(state), proposer_reward)
|
|
```
|
|
|
|
#### Modified `process_deposit`
|
|
|
|
*Note*: The function `process_deposit` is modified to initialize `inactivity_scores`, `previous_epoch_participation`, `current_epoch_participation`.
|
|
|
|
```python
|
|
def process_deposit(state: BeaconState, deposit: Deposit) -> None:
|
|
# Verify the Merkle branch
|
|
assert is_valid_merkle_branch(
|
|
leaf=hash_tree_root(deposit.data),
|
|
branch=deposit.proof,
|
|
depth=DEPOSIT_CONTRACT_TREE_DEPTH + 1, # Add 1 for the List length mix-in
|
|
index=state.eth1_deposit_index,
|
|
root=state.eth1_data.deposit_root,
|
|
)
|
|
|
|
# Deposits must be processed in order
|
|
state.eth1_deposit_index += 1
|
|
|
|
pubkey = deposit.data.pubkey
|
|
amount = deposit.data.amount
|
|
validator_pubkeys = [validator.pubkey for validator in state.validators]
|
|
if pubkey not in validator_pubkeys:
|
|
# Verify the deposit signature (proof of possession) which is not checked by the deposit contract
|
|
deposit_message = DepositMessage(
|
|
pubkey=deposit.data.pubkey,
|
|
withdrawal_credentials=deposit.data.withdrawal_credentials,
|
|
amount=deposit.data.amount,
|
|
)
|
|
domain = compute_domain(DOMAIN_DEPOSIT) # Fork-agnostic domain since deposits are valid across forks
|
|
signing_root = compute_signing_root(deposit_message, domain)
|
|
# Initialize validator if the deposit signature is valid
|
|
if bls.Verify(pubkey, signing_root, deposit.data.signature):
|
|
state.validators.append(get_validator_from_deposit(state, deposit))
|
|
state.balances.append(amount)
|
|
state.previous_epoch_participation.append(ParticipationFlags(0b0000_0000))
|
|
state.current_epoch_participation.append(ParticipationFlags(0b0000_0000))
|
|
state.inactivity_scores.append(0)
|
|
else:
|
|
# Increase balance by deposit amount
|
|
index = ValidatorIndex(validator_pubkeys.index(pubkey))
|
|
increase_balance(state, index, amount)
|
|
```
|
|
|
|
#### Sync committee processing
|
|
|
|
```python
|
|
def process_sync_committee(state: BeaconState, body: BeaconBlockBody) -> None:
|
|
# Verify sync committee aggregate signature signing over the previous slot block root
|
|
previous_slot = Slot(max(int(state.slot), 1) - 1)
|
|
committee_indices = get_sync_committee_indices(state, get_current_epoch(state))
|
|
participant_indices = [index for index, bit in zip(committee_indices, body.sync_committee_bits) if bit]
|
|
committee_pubkeys = state.current_sync_committee.pubkeys
|
|
participant_pubkeys = [pubkey for pubkey, bit in zip(committee_pubkeys, body.sync_committee_bits) if bit]
|
|
domain = get_domain(state, DOMAIN_SYNC_COMMITTEE, compute_epoch_at_slot(previous_slot))
|
|
signing_root = compute_signing_root(get_block_root_at_slot(state, previous_slot), domain)
|
|
assert eth2_fast_aggregate_verify(participant_pubkeys, signing_root, body.sync_committee_signature)
|
|
|
|
# Reward sync committee participants
|
|
proposer_rewards = Gwei(0)
|
|
active_validator_count = uint64(len(get_active_validator_indices(state, get_current_epoch(state))))
|
|
for participant_index in participant_indices:
|
|
proposer_reward = get_proposer_reward(state, participant_index)
|
|
proposer_rewards += proposer_reward
|
|
base_reward = get_base_reward(state, participant_index)
|
|
max_participant_reward = base_reward - proposer_reward
|
|
reward = Gwei(max_participant_reward * active_validator_count // (len(committee_indices) * SLOTS_PER_EPOCH))
|
|
increase_balance(state, participant_index, reward)
|
|
|
|
# Reward beacon proposer
|
|
increase_balance(state, get_beacon_proposer_index(state), proposer_rewards)
|
|
```
|
|
|
|
### Epoch processing
|
|
|
|
```python
|
|
def process_epoch(state: BeaconState) -> None:
|
|
process_justification_and_finalization(state) # [Modified in Altair]
|
|
process_inactivity_updates(state) # [New in Altair]
|
|
process_rewards_and_penalties(state) # [Modified in Altair]
|
|
process_registry_updates(state)
|
|
process_slashings(state) # [Modified in Altair]
|
|
process_eth1_data_reset(state)
|
|
process_effective_balance_updates(state)
|
|
process_slashings_reset(state)
|
|
process_randao_mixes_reset(state)
|
|
process_historical_roots_update(state)
|
|
process_participation_flag_updates(state) # [New in Altair]
|
|
process_sync_committee_updates(state) # [New in Altair]
|
|
```
|
|
|
|
#### Justification and finalization
|
|
|
|
*Note*: The function `process_justification_and_finalization` is modified with `matching_target_attestations` replaced by `matching_target_indices`.
|
|
|
|
```python
|
|
def process_justification_and_finalization(state: BeaconState) -> None:
|
|
# Initial FFG checkpoint values have a `0x00` stub for `root`.
|
|
# Skip FFG updates in the first two epochs to avoid corner cases that might result in modifying this stub.
|
|
if get_current_epoch(state) <= GENESIS_EPOCH + 1:
|
|
return
|
|
previous_epoch = get_previous_epoch(state)
|
|
current_epoch = get_current_epoch(state)
|
|
old_previous_justified_checkpoint = state.previous_justified_checkpoint
|
|
old_current_justified_checkpoint = state.current_justified_checkpoint
|
|
|
|
# Process justifications
|
|
state.previous_justified_checkpoint = state.current_justified_checkpoint
|
|
state.justification_bits[1:] = state.justification_bits[:JUSTIFICATION_BITS_LENGTH - 1]
|
|
state.justification_bits[0] = 0b0
|
|
matching_target_indices = get_unslashed_participating_indices(state, TIMELY_TARGET_FLAG_INDEX, previous_epoch)
|
|
if get_total_balance(state, matching_target_indices) * 3 >= get_total_active_balance(state) * 2:
|
|
state.current_justified_checkpoint = Checkpoint(epoch=previous_epoch,
|
|
root=get_block_root(state, previous_epoch))
|
|
state.justification_bits[1] = 0b1
|
|
matching_target_indices = get_unslashed_participating_indices(state, TIMELY_TARGET_FLAG_INDEX, current_epoch)
|
|
if get_total_balance(state, matching_target_indices) * 3 >= get_total_active_balance(state) * 2:
|
|
state.current_justified_checkpoint = Checkpoint(epoch=current_epoch,
|
|
root=get_block_root(state, current_epoch))
|
|
state.justification_bits[0] = 0b1
|
|
|
|
# Process finalizations
|
|
bits = state.justification_bits
|
|
# The 2nd/3rd/4th most recent epochs are justified, the 2nd using the 4th as source
|
|
if all(bits[1:4]) and old_previous_justified_checkpoint.epoch + 3 == current_epoch:
|
|
state.finalized_checkpoint = old_previous_justified_checkpoint
|
|
# The 2nd/3rd most recent epochs are justified, the 2nd using the 3rd as source
|
|
if all(bits[1:3]) and old_previous_justified_checkpoint.epoch + 2 == current_epoch:
|
|
state.finalized_checkpoint = old_previous_justified_checkpoint
|
|
# The 1st/2nd/3rd most recent epochs are justified, the 1st using the 3rd as source
|
|
if all(bits[0:3]) and old_current_justified_checkpoint.epoch + 2 == current_epoch:
|
|
state.finalized_checkpoint = old_current_justified_checkpoint
|
|
# The 1st/2nd most recent epochs are justified, the 1st using the 2nd as source
|
|
if all(bits[0:2]) and old_current_justified_checkpoint.epoch + 1 == current_epoch:
|
|
state.finalized_checkpoint = old_current_justified_checkpoint
|
|
```
|
|
|
|
#### Inactivity scores
|
|
|
|
*Note*: The function `process_inactivity_updates` is new.
|
|
|
|
```python
|
|
def process_inactivity_updates(state: BeaconState) -> None:
|
|
for index in get_eligible_validator_indices(state):
|
|
if index in get_unslashed_participating_indices(state, TIMELY_TARGET_FLAG_INDEX, get_previous_epoch(state)):
|
|
if state.inactivity_scores[index] > 0:
|
|
state.inactivity_scores[index] -= 1
|
|
elif is_in_inactivity_leak(state):
|
|
state.inactivity_scores[index] += INACTIVITY_SCORE_BIAS
|
|
```
|
|
|
|
#### Rewards and penalties
|
|
|
|
*Note*: The function `process_rewards_and_penalties` is modified to support the incentive accounting reforms.
|
|
|
|
```python
|
|
def process_rewards_and_penalties(state: BeaconState) -> None:
|
|
# No rewards are applied at the end of `GENESIS_EPOCH` because rewards are for work done in the previous epoch
|
|
if get_current_epoch(state) == GENESIS_EPOCH:
|
|
return
|
|
|
|
flag_indices_and_numerators = get_flag_indices_and_numerators()
|
|
flag_deltas = [get_flag_index_deltas(state, index, numerator) for (index, numerator) in flag_indices_and_numerators]
|
|
deltas = flag_deltas + [get_inactivity_penalty_deltas(state)]
|
|
for (rewards, penalties) in deltas:
|
|
for index in range(len(state.validators)):
|
|
increase_balance(state, ValidatorIndex(index), rewards[index])
|
|
decrease_balance(state, ValidatorIndex(index), penalties[index])
|
|
```
|
|
|
|
#### Slashings
|
|
|
|
*Note*: The function `process_slashings` is modified to use `ALTAIR_PROPORTIONAL_SLASHING_MULTIPLIER`.
|
|
|
|
```python
|
|
def process_slashings(state: BeaconState) -> None:
|
|
epoch = get_current_epoch(state)
|
|
total_balance = get_total_active_balance(state)
|
|
adjusted_total_slashing_balance = min(sum(state.slashings) * ALTAIR_PROPORTIONAL_SLASHING_MULTIPLIER, total_balance)
|
|
for index, validator in enumerate(state.validators):
|
|
if validator.slashed and epoch + EPOCHS_PER_SLASHINGS_VECTOR // 2 == validator.withdrawable_epoch:
|
|
increment = EFFECTIVE_BALANCE_INCREMENT # Factored out from penalty numerator to avoid uint64 overflow
|
|
penalty_numerator = validator.effective_balance // increment * adjusted_total_slashing_balance
|
|
penalty = penalty_numerator // total_balance * increment
|
|
decrease_balance(state, ValidatorIndex(index), penalty)
|
|
```
|
|
|
|
#### Participation flags updates
|
|
|
|
*Note*: The function `process_participation_flag_updates` is new.
|
|
|
|
```python
|
|
def process_participation_flag_updates(state: BeaconState) -> None:
|
|
state.previous_epoch_participation = state.current_epoch_participation
|
|
state.current_epoch_participation = [ParticipationFlags(0b0000_0000) for _ in range(len(state.validators))]
|
|
```
|
|
|
|
#### Sync committee updates
|
|
|
|
*Note*: The function `process_sync_committee_updates` is new.
|
|
|
|
```python
|
|
def process_sync_committee_updates(state: BeaconState) -> None:
|
|
next_epoch = get_current_epoch(state) + Epoch(1)
|
|
if next_epoch % EPOCHS_PER_SYNC_COMMITTEE_PERIOD == 0:
|
|
state.current_sync_committee = state.next_sync_committee
|
|
state.next_sync_committee = get_sync_committee(state, next_epoch + EPOCHS_PER_SYNC_COMMITTEE_PERIOD)
|
|
```
|