909 lines
34 KiB
Markdown
909 lines
34 KiB
Markdown
# Ethereum 2.0 Phase 1 -- The Beacon Chain for Shards
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**Notice**: This document is a work-in-progress for researchers and implementers.
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## Table of contents
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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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**Table of Contents**
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- [Introduction](#introduction)
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- [Custom types](#custom-types)
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- [Configuration](#configuration)
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- [Misc](#misc)
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- [Updated containers](#updated-containers)
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- [Extended `AttestationData`](#extended-attestationdata)
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- [Extended `Attestation`](#extended-attestation)
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- [Extended `PendingAttestation`](#extended-pendingattestation)
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- [`IndexedAttestation`](#indexedattestation)
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- [Extended `AttesterSlashing`](#extended-attesterslashing)
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- [Extended `Validator`](#extended-validator)
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- [Extended `BeaconBlockBody`](#extended-beaconblockbody)
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- [Extended `BeaconBlock`](#extended-beaconblock)
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- [Extended `SignedBeaconBlock`](#extended-signedbeaconblock)
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- [Extended `BeaconState`](#extended-beaconstate)
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- [New containers](#new-containers)
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- [`ShardBlockWrapper`](#shardblockwrapper)
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- [`ShardSignableHeader`](#shardsignableheader)
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- [`ShardState`](#shardstate)
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- [`ShardTransition`](#shardtransition)
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- [`CompactCommittee`](#compactcommittee)
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- [`AttestationCustodyBitWrapper`](#attestationcustodybitwrapper)
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- [Helper functions](#helper-functions)
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- [Misc](#misc-1)
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- [`get_previous_slot`](#get_previous_slot)
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- [`pack_compact_validator`](#pack_compact_validator)
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- [`committee_to_compact_committee`](#committee_to_compact_committee)
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- [`compute_shard_from_committee_index`](#compute_shard_from_committee_index)
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- [Beacon state accessors](#beacon-state-accessors)
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- [`get_active_shard_count`](#get_active_shard_count)
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- [`get_online_validator_indices`](#get_online_validator_indices)
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- [`get_shard_committee`](#get_shard_committee)
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- [`get_shard_proposer_index`](#get_shard_proposer_index)
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- [`get_light_client_committee`](#get_light_client_committee)
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- [`get_indexed_attestation`](#get_indexed_attestation)
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- [`get_updated_gasprice`](#get_updated_gasprice)
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- [`get_start_shard`](#get_start_shard)
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- [`get_shard`](#get_shard)
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- [`get_next_slot_for_shard`](#get_next_slot_for_shard)
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- [`get_offset_slots`](#get_offset_slots)
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- [Predicates](#predicates)
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- [Updated `is_valid_indexed_attestation`](#updated-is_valid_indexed_attestation)
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- [Block processing](#block-processing)
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- [Operations](#operations)
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- [New Attestation processing](#new-attestation-processing)
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- [`validate_attestation`](#validate_attestation)
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- [`apply_shard_transition`](#apply_shard_transition)
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- [`process_crosslink_for_shard`](#process_crosslink_for_shard)
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- [`process_crosslinks`](#process_crosslinks)
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- [`process_attestations`](#process_attestations)
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- [New Attester slashing processing](#new-attester-slashing-processing)
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- [Shard transition false positives](#shard-transition-false-positives)
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- [Light client processing](#light-client-processing)
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- [Epoch transition](#epoch-transition)
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- [Custody game updates](#custody-game-updates)
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- [Online-tracking](#online-tracking)
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- [Light client committee updates](#light-client-committee-updates)
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<!-- END doctoc generated TOC please keep comment here to allow auto update -->
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## Introduction
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This document describes the extensions made to the Phase 0 design of The Beacon Chain
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to facilitate the new shards as part of Phase 1 of Eth2.
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## Custom types
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We define the following Python custom types for type hinting and readability:
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| Name | SSZ equivalent | Description |
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| - | - | - |
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| `Shard` | `uint64` | a shard number |
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| `OnlineEpochs` | `uint8` | online countdown epochs |
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## Configuration
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Configuration is not namespaced. Instead it is strictly an extension;
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no constants of phase 0 change, but new constants are adopted for changing behaviors.
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### Misc
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| Name | Value | Unit | Duration |
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| - | - | - | - |
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| `MAX_SHARDS` | `2**10` (= 1024) |
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| `ONLINE_PERIOD` | `OnlineEpochs(2**3)` (= 8) | online epochs | ~51 min |
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| `LIGHT_CLIENT_COMMITTEE_SIZE` | `2**7` (= 128) |
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| `LIGHT_CLIENT_COMMITTEE_PERIOD` | `Epoch(2**8)` (= 256) | epochs | ~27 hours |
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| `SHARD_COMMITTEE_PERIOD` | `Epoch(2**8)` (= 256) | epochs | ~27 hours |
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| `MAX_SHARD_BLOCK_SIZE` | `2**20` (= 1,048,576) | |
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| `TARGET_SHARD_BLOCK_SIZE` | `2**18` (= 262,144) | |
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| `SHARD_BLOCK_OFFSETS` | `[1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233]` | |
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| `MAX_SHARD_BLOCKS_PER_ATTESTATION` | `len(SHARD_BLOCK_OFFSETS)` | |
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| `MAX_GASPRICE` | `Gwei(2**14)` (= 16,384) | Gwei | |
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| `MIN_GASPRICE` | `Gwei(2**5)` (= 32) | Gwei | |
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| `GASPRICE_ADJUSTMENT_COEFFICIENT` | `2**3` (= 8) | |
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| `DOMAIN_SHARD_PROPOSAL` | `DomainType('0x80000000')` | |
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| `DOMAIN_SHARD_COMMITTEE` | `DomainType('0x81000000')` | |
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| `DOMAIN_LIGHT_CLIENT` | `DomainType('0x82000000')` | |
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## Updated containers
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The following containers have updated definitions in Phase 1.
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### Extended `AttestationData`
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```python
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class AttestationData(Container):
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slot: Slot
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index: CommitteeIndex
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# LMD GHOST vote
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beacon_block_root: Root
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# FFG vote
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source: Checkpoint
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target: Checkpoint
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# Current-slot shard block root
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head_shard_root: Root
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# Shard transition root
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shard_transition_root: Root
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```
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### Extended `Attestation`
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```python
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class Attestation(Container):
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aggregation_bits: Bitlist[MAX_VALIDATORS_PER_COMMITTEE]
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data: AttestationData
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custody_bits_blocks: List[Bitlist[MAX_VALIDATORS_PER_COMMITTEE], MAX_SHARD_BLOCKS_PER_ATTESTATION]
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signature: BLSSignature
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```
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### Extended `PendingAttestation`
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```python
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class PendingAttestation(Container):
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aggregation_bits: Bitlist[MAX_VALIDATORS_PER_COMMITTEE]
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data: AttestationData
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inclusion_delay: Slot
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proposer_index: ValidatorIndex
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crosslink_success: boolean
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```
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### `IndexedAttestation`
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```python
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class IndexedAttestation(Container):
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committee: List[ValidatorIndex, MAX_VALIDATORS_PER_COMMITTEE]
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attestation: Attestation
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```
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#### Extended `AttesterSlashing`
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Note that the `attestation_1` and `attestation_2` have a new `IndexedAttestation` definition.
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```python
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class AttesterSlashing(Container):
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attestation_1: IndexedAttestation
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attestation_2: IndexedAttestation
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```
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### Extended `Validator`
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```python
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class Validator(Container):
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pubkey: BLSPubkey
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withdrawal_credentials: Bytes32 # Commitment to pubkey for withdrawals
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effective_balance: Gwei # Balance at stake
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slashed: boolean
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# Status epochs
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activation_eligibility_epoch: Epoch # When criteria for activation were met
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activation_epoch: Epoch
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exit_epoch: Epoch
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withdrawable_epoch: Epoch # When validator can withdraw funds
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# Custody game
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# next_custody_secret_to_reveal is initialised to the custody period
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# (of the particular validator) in which the validator is activated
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# = get_custody_period_for_validator(...)
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next_custody_secret_to_reveal: uint64
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max_reveal_lateness: Epoch
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```
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### Extended `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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# Slashings
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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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# Attesting
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attestations: List[Attestation, MAX_ATTESTATIONS]
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# Entry & exit
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deposits: List[Deposit, MAX_DEPOSITS]
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voluntary_exits: List[SignedVoluntaryExit, MAX_VOLUNTARY_EXITS]
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# Custody game
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custody_slashings: List[SignedCustodySlashing, MAX_CUSTODY_SLASHINGS]
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custody_key_reveals: List[CustodyKeyReveal, MAX_CUSTODY_KEY_REVEALS]
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early_derived_secret_reveals: List[EarlyDerivedSecretReveal, MAX_EARLY_DERIVED_SECRET_REVEALS]
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# Shards
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shard_transitions: Vector[ShardTransition, MAX_SHARDS]
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# Light clients
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light_client_signature_bitfield: Bitvector[LIGHT_CLIENT_COMMITTEE_SIZE]
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light_client_signature: BLSSignature
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```
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### Extended `BeaconBlock`
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Note that the `body` has a new `BeaconBlockBody` definition.
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```python
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class BeaconBlock(Container):
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slot: Slot
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proposer_index: ValidatorIndex
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parent_root: Root
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state_root: Root
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body: BeaconBlockBody
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```
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#### Extended `SignedBeaconBlock`
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Note that the `message` has a new `BeaconBlock` definition.
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```python
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class SignedBeaconBlock(Container):
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message: BeaconBlock
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signature: BLSSignature
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```
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### Extended `BeaconState`
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Note that aside from the new additions, `Validator` and `PendingAttestation` have new definitions.
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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[Root, 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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# Attestations
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previous_epoch_attestations: List[PendingAttestation, MAX_ATTESTATIONS * SLOTS_PER_EPOCH]
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current_epoch_attestations: List[PendingAttestation, MAX_ATTESTATIONS * SLOTS_PER_EPOCH]
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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 # Previous epoch snapshot
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current_justified_checkpoint: Checkpoint
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finalized_checkpoint: Checkpoint
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# Phase 1
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shard_states: List[ShardState, MAX_SHARDS]
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online_countdown: List[OnlineEpochs, VALIDATOR_REGISTRY_LIMIT] # not a raw byte array, considered its large size.
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current_light_committee: CompactCommittee
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next_light_committee: CompactCommittee
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# Custody game
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# Future derived secrets already exposed; contains the indices of the exposed validator
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# at RANDAO reveal period % EARLY_DERIVED_SECRET_PENALTY_MAX_FUTURE_EPOCHS
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exposed_derived_secrets: Vector[List[ValidatorIndex, MAX_EARLY_DERIVED_SECRET_REVEALS * SLOTS_PER_EPOCH],
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EARLY_DERIVED_SECRET_PENALTY_MAX_FUTURE_EPOCHS]
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```
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## New containers
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The following containers are new in Phase 1.
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### `ShardBlockWrapper`
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_Wrapper for being broadcasted over the network._
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```python
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class ShardBlockWrapper(Container):
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shard_parent_root: Root
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beacon_parent_root: Root
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slot: Slot
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body: ByteList[MAX_SHARD_BLOCK_SIZE]
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signature: BLSSignature
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```
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### `ShardSignableHeader`
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```python
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class ShardSignableHeader(Container):
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shard_parent_root: Root
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beacon_parent_root: Root
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slot: Slot
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body_root: Root
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```
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### `ShardState`
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```python
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class ShardState(Container):
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slot: Slot
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gasprice: Gwei
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data: Bytes32
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latest_block_root: Root
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```
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### `ShardTransition`
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```python
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class ShardTransition(Container):
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# Starting from slot
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start_slot: Slot
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# Shard block lengths
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shard_block_lengths: List[uint64, MAX_SHARD_BLOCKS_PER_ATTESTATION]
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# Shard data roots
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shard_data_roots: List[Bytes32, MAX_SHARD_BLOCKS_PER_ATTESTATION]
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# Intermediate shard states
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shard_states: List[ShardState, MAX_SHARD_BLOCKS_PER_ATTESTATION]
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# Proposer signature aggregate
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proposer_signature_aggregate: BLSSignature
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```
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### `CompactCommittee`
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```python
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class CompactCommittee(Container):
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pubkeys: List[BLSPubkey, MAX_VALIDATORS_PER_COMMITTEE]
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compact_validators: List[uint64, MAX_VALIDATORS_PER_COMMITTEE]
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```
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### `AttestationCustodyBitWrapper`
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```python
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class AttestationCustodyBitWrapper(Container):
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attestation_data_root: Root
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block_index: uint64
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bit: boolean
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```
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## Helper functions
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### Misc
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#### `get_previous_slot`
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```python
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def get_previous_slot(slot: Slot) -> Slot:
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if slot > 0:
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return Slot(slot - 1)
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else:
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return Slot(0)
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```
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#### `pack_compact_validator`
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```python
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def pack_compact_validator(index: int, slashed: bool, balance_in_increments: int) -> int:
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"""
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Creates a compact validator object representing index, slashed status, and compressed balance.
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Takes as input balance-in-increments (// EFFECTIVE_BALANCE_INCREMENT) to preserve symmetry with
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the unpacking function.
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"""
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return (index << 16) + (slashed << 15) + balance_in_increments
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```
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#### `committee_to_compact_committee`
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```python
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def committee_to_compact_committee(state: BeaconState, committee: Sequence[ValidatorIndex]) -> CompactCommittee:
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"""
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Given a state and a list of validator indices, outputs the CompactCommittee representing them.
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"""
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validators = [state.validators[i] for i in committee]
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compact_validators = [
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pack_compact_validator(i, v.slashed, v.effective_balance // EFFECTIVE_BALANCE_INCREMENT)
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for i, v in zip(committee, validators)
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]
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pubkeys = [v.pubkey for v in validators]
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return CompactCommittee(pubkeys=pubkeys, compact_validators=compact_validators)
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```
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#### `compute_shard_from_committee_index`
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```python
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def compute_shard_from_committee_index(state: BeaconState, index: CommitteeIndex, slot: Slot) -> Shard:
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active_shards = get_active_shard_count(state)
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return Shard((index + get_start_shard(state, slot)) % active_shards)
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```
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### Beacon state accessors
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#### `get_active_shard_count`
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```python
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def get_active_shard_count(state: BeaconState) -> uint64:
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return len(state.shard_states) # May adapt in the future, or change over time.
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```
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#### `get_online_validator_indices`
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```python
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def get_online_validator_indices(state: BeaconState) -> Set[ValidatorIndex]:
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active_validators = get_active_validator_indices(state, get_current_epoch(state))
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return set([i for i in active_validators if state.online_countdown[i] != 0])
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```
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#### `get_shard_committee`
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```python
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def get_shard_committee(beacon_state: BeaconState, epoch: Epoch, shard: Shard) -> Sequence[ValidatorIndex]:
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source_epoch = epoch - epoch % SHARD_COMMITTEE_PERIOD
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if source_epoch > 0:
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source_epoch -= SHARD_COMMITTEE_PERIOD
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active_validator_indices = get_active_validator_indices(beacon_state, source_epoch)
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seed = get_seed(beacon_state, source_epoch, DOMAIN_SHARD_COMMITTEE)
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return compute_committee(active_validator_indices, seed, shard, get_active_shard_count(beacon_state))
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```
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#### `get_shard_proposer_index`
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```python
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def get_shard_proposer_index(beacon_state: BeaconState, slot: Slot, shard: Shard) -> ValidatorIndex:
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committee = get_shard_committee(beacon_state, compute_epoch_at_slot(slot), shard)
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r = bytes_to_int(get_seed(beacon_state, get_current_epoch(beacon_state), DOMAIN_SHARD_COMMITTEE)[:8])
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return committee[r % len(committee)]
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```
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#### `get_light_client_committee`
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```python
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def get_light_client_committee(beacon_state: BeaconState, epoch: Epoch) -> Sequence[ValidatorIndex]:
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source_epoch = epoch - epoch % LIGHT_CLIENT_COMMITTEE_PERIOD
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if source_epoch > 0:
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source_epoch -= LIGHT_CLIENT_COMMITTEE_PERIOD
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active_validator_indices = get_active_validator_indices(beacon_state, source_epoch)
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seed = get_seed(beacon_state, source_epoch, DOMAIN_LIGHT_CLIENT)
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active_shards = get_active_shard_count(beacon_state)
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return compute_committee(active_validator_indices, seed, 0, active_shards)[:TARGET_COMMITTEE_SIZE]
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```
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#### `get_indexed_attestation`
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```python
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def get_indexed_attestation(beacon_state: BeaconState, attestation: Attestation) -> IndexedAttestation:
|
|
committee = get_beacon_committee(beacon_state, attestation.data.slot, attestation.data.index)
|
|
return IndexedAttestation(
|
|
committee=committee,
|
|
attestation=attestation,
|
|
)
|
|
```
|
|
|
|
#### `get_updated_gasprice`
|
|
|
|
```python
|
|
def get_updated_gasprice(prev_gasprice: Gwei, length: uint8) -> Gwei:
|
|
if length > TARGET_SHARD_BLOCK_SIZE:
|
|
delta = (prev_gasprice * (length - TARGET_SHARD_BLOCK_SIZE)
|
|
// TARGET_SHARD_BLOCK_SIZE // GASPRICE_ADJUSTMENT_COEFFICIENT)
|
|
return min(prev_gasprice + delta, MAX_GASPRICE)
|
|
else:
|
|
delta = (prev_gasprice * (TARGET_SHARD_BLOCK_SIZE - length)
|
|
// TARGET_SHARD_BLOCK_SIZE // GASPRICE_ADJUSTMENT_COEFFICIENT)
|
|
return max(prev_gasprice, MIN_GASPRICE + delta) - delta
|
|
```
|
|
|
|
#### `get_start_shard`
|
|
|
|
```python
|
|
def get_start_shard(state: BeaconState, slot: Slot) -> Shard:
|
|
# TODO: implement start shard logic
|
|
return Shard(0)
|
|
```
|
|
|
|
#### `get_shard`
|
|
|
|
```python
|
|
def get_shard(state: BeaconState, attestation: Attestation) -> Shard:
|
|
return compute_shard_from_committee_index(state, attestation.data.index, attestation.data.slot)
|
|
```
|
|
|
|
#### `get_next_slot_for_shard`
|
|
|
|
```python
|
|
def get_next_slot_for_shard(state: BeaconState, shard: Shard) -> Slot:
|
|
return Slot(state.shard_states[shard].slot + 1)
|
|
```
|
|
|
|
|
|
#### `get_offset_slots`
|
|
|
|
```python
|
|
def get_offset_slots(state: BeaconState, start_slot: Slot) -> Sequence[Slot]:
|
|
return [Slot(start_slot + x) for x in SHARD_BLOCK_OFFSETS if start_slot + x < state.slot]
|
|
```
|
|
|
|
### Predicates
|
|
|
|
#### Updated `is_valid_indexed_attestation`
|
|
|
|
Note that this replaces the Phase 0 `is_valid_indexed_attestation`.
|
|
|
|
```python
|
|
def is_valid_indexed_attestation(state: BeaconState, indexed_attestation: IndexedAttestation) -> bool:
|
|
"""
|
|
Check if ``indexed_attestation`` has valid indices and signature.
|
|
"""
|
|
# Verify aggregate signature
|
|
all_pubkeys = []
|
|
all_signing_roots = []
|
|
attestation = indexed_attestation.attestation
|
|
domain = get_domain(state, DOMAIN_BEACON_ATTESTER, attestation.data.target.epoch)
|
|
aggregation_bits = attestation.aggregation_bits
|
|
assert len(aggregation_bits) == len(indexed_attestation.committee)
|
|
|
|
if len(attestation.custody_bits_blocks) == 0:
|
|
# fall back on phase0 behavior if there is no shard data.
|
|
for participant, abit in zip(indexed_attestation.committee, aggregation_bits):
|
|
if abit:
|
|
all_pubkeys.append(state.validators[participant].pubkey)
|
|
signing_root = compute_signing_root(indexed_attestation.attestation.data, domain)
|
|
return bls.FastAggregateVerify(all_pubkeys, signing_root, signature=attestation.signature)
|
|
else:
|
|
for i, custody_bits in enumerate(attestation.custody_bits_blocks):
|
|
assert len(custody_bits) == len(indexed_attestation.committee)
|
|
for participant, abit, cbit in zip(indexed_attestation.committee, aggregation_bits, custody_bits):
|
|
if abit:
|
|
all_pubkeys.append(state.validators[participant].pubkey)
|
|
# Note: only 2N distinct message hashes
|
|
all_signing_roots.append(compute_signing_root(
|
|
AttestationCustodyBitWrapper(hash_tree_root(attestation.data), i, cbit), domain))
|
|
else:
|
|
assert not cbit
|
|
return bls.AggregateVerify(zip(all_pubkeys, all_signing_roots), signature=attestation.signature)
|
|
```
|
|
|
|
|
|
### Block processing
|
|
|
|
```python
|
|
def process_block(state: BeaconState, block: BeaconBlock) -> None:
|
|
process_block_header(state, block)
|
|
process_randao(state, block.body)
|
|
process_eth1_data(state, block.body)
|
|
verify_shard_transition_false_positives(state, block.body)
|
|
process_light_client_signatures(state, block.body)
|
|
process_operations(state, block.body)
|
|
```
|
|
|
|
|
|
#### Operations
|
|
|
|
```python
|
|
def process_operations(state: BeaconState, body: BeaconBlockBody) -> None:
|
|
# Verify that outstanding deposits are processed up to the maximum number of deposits
|
|
assert len(body.deposits) == min(MAX_DEPOSITS, state.eth1_data.deposit_count - state.eth1_deposit_index)
|
|
|
|
def for_ops(operations: Sequence[Any], fn: Callable[[BeaconState, Any], None]) -> None:
|
|
for operation in operations:
|
|
fn(state, operation)
|
|
|
|
for_ops(body.proposer_slashings, process_proposer_slashing)
|
|
for_ops(body.attester_slashings, process_attester_slashing)
|
|
|
|
# New attestation processing
|
|
process_attestations(state, body, body.attestations)
|
|
|
|
for_ops(body.deposits, process_deposit)
|
|
for_ops(body.voluntary_exits, process_voluntary_exit)
|
|
|
|
# See custody game spec.
|
|
process_custody_game_operations(state, body)
|
|
|
|
# TODO process_operations(body.shard_receipt_proofs, process_shard_receipt_proofs)
|
|
```
|
|
|
|
##### New Attestation processing
|
|
|
|
###### `validate_attestation`
|
|
|
|
```python
|
|
def validate_attestation(state: BeaconState, attestation: Attestation) -> None:
|
|
data = attestation.data
|
|
assert data.index < get_committee_count_at_slot(state, data.slot)
|
|
assert data.index < get_active_shard_count(state)
|
|
assert data.target.epoch in (get_previous_epoch(state), get_current_epoch(state))
|
|
assert data.slot + MIN_ATTESTATION_INCLUSION_DELAY <= state.slot <= data.slot + SLOTS_PER_EPOCH
|
|
|
|
committee = get_beacon_committee(state, data.slot, data.index)
|
|
assert len(attestation.aggregation_bits) == len(committee)
|
|
|
|
if attestation.data.target.epoch == get_current_epoch(state):
|
|
assert attestation.data.source == state.current_justified_checkpoint
|
|
else:
|
|
assert attestation.data.source == state.previous_justified_checkpoint
|
|
|
|
shard = get_shard(state, attestation)
|
|
shard_start_slot = get_next_slot_for_shard(state, shard)
|
|
|
|
# Signature check
|
|
assert is_valid_indexed_attestation(state, get_indexed_attestation(state, attestation))
|
|
# Type 1: on-time attestations
|
|
if attestation.custody_bits_blocks != []:
|
|
# Correct slot
|
|
assert data.slot + MIN_ATTESTATION_INCLUSION_DELAY == state.slot
|
|
# Correct data root count
|
|
assert len(attestation.custody_bits_blocks) == len(get_offset_slots(state, shard_start_slot))
|
|
# Correct parent block root
|
|
assert data.beacon_block_root == get_block_root_at_slot(state, get_previous_slot(state.slot))
|
|
# Type 2: no shard transition, no custody bits # TODO: could only allow for older attestations.
|
|
else:
|
|
# assert state.slot - compute_start_slot_at_epoch(compute_epoch_at_slot(data.slot)) < SLOTS_PER_EPOCH
|
|
assert data.shard_transition_root == Root()
|
|
```
|
|
|
|
###### `apply_shard_transition`
|
|
|
|
```python
|
|
def apply_shard_transition(state: BeaconState, shard: Shard, transition: ShardTransition) -> None:
|
|
# Slot the attestation starts counting from
|
|
start_slot = get_next_slot_for_shard(state, shard)
|
|
|
|
# Correct data root count
|
|
offset_slots = get_offset_slots(state, start_slot)
|
|
assert (
|
|
len(transition.shard_data_roots)
|
|
== len(transition.shard_states)
|
|
== len(transition.shard_block_lengths)
|
|
== len(offset_slots)
|
|
)
|
|
assert transition.start_slot == start_slot
|
|
|
|
# Reconstruct shard headers
|
|
headers = []
|
|
proposers = []
|
|
shard_parent_root = state.shard_states[shard].latest_block_root
|
|
for i in range(len(offset_slots)):
|
|
if any(transition.shard_data_roots):
|
|
headers.append(ShardSignableHeader(
|
|
shard_parent_root=shard_parent_root,
|
|
parent_hash=get_block_root_at_slot(state, get_previous_slot(state.slot)),
|
|
slot=offset_slots[i],
|
|
body_root=transition.shard_data_roots[i]
|
|
))
|
|
proposers.append(get_shard_proposer_index(state, shard, offset_slots[i]))
|
|
shard_parent_root = hash_tree_root(headers[-1])
|
|
|
|
# Verify correct calculation of gas prices and slots
|
|
prev_gasprice = state.shard_states[shard].gasprice
|
|
for i in range(len(offset_slots)):
|
|
shard_state = transition.shard_states[i]
|
|
block_length = transition.shard_block_lengths[i]
|
|
assert shard_state.gasprice == get_updated_gasprice(prev_gasprice, block_length)
|
|
assert shard_state.slot == offset_slots[i]
|
|
prev_gasprice = shard_state.gasprice
|
|
|
|
pubkeys = [state.validators[proposer].pubkey for proposer in proposers]
|
|
signing_roots = [
|
|
compute_signing_root(header, get_domain(state, DOMAIN_SHARD_PROPOSAL, compute_epoch_at_slot(header.slot)))
|
|
for header in headers
|
|
]
|
|
# Verify combined proposer signature
|
|
assert bls.AggregateVerify(zip(pubkeys, signing_roots), signature=transition.proposer_signature_aggregate)
|
|
|
|
# Save updated state
|
|
state.shard_states[shard] = transition.shard_states[-1]
|
|
state.shard_states[shard].slot = state.slot - 1
|
|
```
|
|
|
|
###### `process_crosslink_for_shard`
|
|
|
|
```python
|
|
def process_crosslink_for_shard(state: BeaconState,
|
|
shard: Shard,
|
|
shard_transition: ShardTransition,
|
|
attestations: Sequence[Attestation]) -> Root:
|
|
committee = get_beacon_committee(state, get_current_epoch(state), shard)
|
|
online_indices = get_online_validator_indices(state)
|
|
|
|
# Loop over all shard transition roots
|
|
shard_transition_roots = set([a.data.shard_transition_root for a in attestations])
|
|
for shard_transition_root in sorted(shard_transition_roots):
|
|
transition_attestations = [a for a in attestations if a.data.shard_transition_root == shard_transition_root]
|
|
transition_participants: Set[ValidatorIndex] = set()
|
|
for attestation in transition_attestations:
|
|
participants = get_attesting_indices(state, attestation.data, attestation.aggregation_bits)
|
|
transition_participants = transition_participants.union(participants)
|
|
|
|
enough_online_stake = (
|
|
get_total_balance(state, online_indices.intersection(transition_participants)) * 3 >=
|
|
get_total_balance(state, online_indices.intersection(committee)) * 2
|
|
)
|
|
# If not enough stake, try next transition root
|
|
if not enough_online_stake:
|
|
continue
|
|
|
|
# Attestation <-> shard transition consistency
|
|
assert shard_transition_root == hash_tree_root(shard_transition)
|
|
assert attestation.data.head_shard_root == shard_transition.shard_data_roots[-1]
|
|
|
|
# Apply transition
|
|
apply_shard_transition(state, shard, shard_transition)
|
|
# Apply proposer reward and cost
|
|
beacon_proposer_index = get_beacon_proposer_index(state)
|
|
estimated_attester_reward = sum([get_base_reward(state, attester) for attester in transition_participants])
|
|
proposer_reward = Gwei(estimated_attester_reward // PROPOSER_REWARD_QUOTIENT)
|
|
increase_balance(state, beacon_proposer_index, proposer_reward)
|
|
states_slots_lengths = zip(
|
|
shard_transition.shard_states,
|
|
get_offset_slots(state, get_next_slot_for_shard(state, shard)),
|
|
shard_transition.shard_block_lengths
|
|
)
|
|
for shard_state, slot, length in states_slots_lengths:
|
|
proposer_index = get_shard_proposer_index(state, shard, slot)
|
|
decrease_balance(state, proposer_index, shard_state.gasprice * length)
|
|
|
|
# Return winning transition root
|
|
return shard_transition_root
|
|
|
|
# No winning transition root, ensure empty and return empty root
|
|
assert shard_transition == ShardTransition()
|
|
return Root()
|
|
```
|
|
|
|
###### `process_crosslinks`
|
|
|
|
```python
|
|
def process_crosslinks(state: BeaconState,
|
|
block_body: BeaconBlockBody,
|
|
attestations: Sequence[Attestation]) -> Set[Tuple[Shard, Root]]:
|
|
winners: Set[Tuple[Shard, Root]] = set()
|
|
committee_count = get_committee_count_at_slot(state, state.slot)
|
|
for committee_index in map(CommitteeIndex, range(committee_count)):
|
|
shard = compute_shard_from_committee_index(state, committee_index, state.slot)
|
|
# All attestations in the block for this shard
|
|
shard_attestations = [
|
|
attestation for attestation in attestations
|
|
if get_shard(state, attestation) == shard and attestation.data.slot == state.slot
|
|
]
|
|
shard_transition = block_body.shard_transitions[shard]
|
|
winning_root = process_crosslink_for_shard(state, shard, shard_transition, shard_attestations)
|
|
if winning_root != Root():
|
|
winners.add((shard, winning_root))
|
|
return winners
|
|
```
|
|
|
|
###### `process_attestations`
|
|
|
|
```python
|
|
def process_attestations(state: BeaconState, block_body: BeaconBlockBody, attestations: Sequence[Attestation]) -> None:
|
|
# Basic validation
|
|
for attestation in attestations:
|
|
validate_attestation(state, attestation)
|
|
|
|
# Process crosslinks
|
|
winners = process_crosslinks(state, block_body, attestations)
|
|
|
|
# Store pending attestations for epoch processing
|
|
for attestation in attestations:
|
|
is_winning_transition = (get_shard(state, attestation), attestation.data.shard_transition_root) in winners
|
|
pending_attestation = PendingAttestation(
|
|
aggregation_bits=attestation.aggregation_bits,
|
|
data=attestation.data,
|
|
inclusion_delay=state.slot - attestation.data.slot,
|
|
crosslink_success=is_winning_transition and attestation.data.slot == state.slot,
|
|
proposer_index=get_beacon_proposer_index(state),
|
|
)
|
|
if attestation.data.target.epoch == get_current_epoch(state):
|
|
state.current_epoch_attestations.append(pending_attestation)
|
|
else:
|
|
state.previous_epoch_attestations.append(pending_attestation)
|
|
```
|
|
|
|
##### New Attester slashing processing
|
|
|
|
```python
|
|
def get_indices_from_committee(
|
|
committee: List[ValidatorIndex, MAX_VALIDATORS_PER_COMMITTEE],
|
|
bits: Bitlist[MAX_VALIDATORS_PER_COMMITTEE]) -> List[ValidatorIndex, MAX_VALIDATORS_PER_COMMITTEE]:
|
|
assert len(bits) == len(committee)
|
|
return List[ValidatorIndex, MAX_VALIDATORS_PER_COMMITTEE](
|
|
[validator_index for i, validator_index in enumerate(committee) if bits[i]]
|
|
)
|
|
```
|
|
|
|
```python
|
|
def process_attester_slashing(state: BeaconState, attester_slashing: AttesterSlashing) -> None:
|
|
indexed_attestation_1 = attester_slashing.attestation_1
|
|
indexed_attestation_2 = attester_slashing.attestation_2
|
|
assert is_slashable_attestation_data(
|
|
indexed_attestation_1.attestation.data,
|
|
indexed_attestation_2.attestation.data,
|
|
)
|
|
assert is_valid_indexed_attestation(state, indexed_attestation_1)
|
|
assert is_valid_indexed_attestation(state, indexed_attestation_2)
|
|
|
|
indices_1 = get_indices_from_committee(
|
|
indexed_attestation_1.committee,
|
|
indexed_attestation_1.attestation.aggregation_bits,
|
|
)
|
|
indices_2 = get_indices_from_committee(
|
|
indexed_attestation_2.committee,
|
|
indexed_attestation_2.attestation.aggregation_bits,
|
|
)
|
|
|
|
slashed_any = False
|
|
indices = set(indices_1).intersection(indices_2)
|
|
for index in sorted(indices):
|
|
if is_slashable_validator(state.validators[index], get_current_epoch(state)):
|
|
slash_validator(state, index)
|
|
slashed_any = True
|
|
assert slashed_any
|
|
```
|
|
|
|
#### Shard transition false positives
|
|
|
|
```python
|
|
def verify_shard_transition_false_positives(state: BeaconState, block_body: BeaconBlockBody) -> None:
|
|
# Verify that a `shard_transition` in a block is empty if an attestation was not processed for it
|
|
for shard in range(get_active_shard_count(state)):
|
|
if state.shard_states[shard].slot != state.slot - 1:
|
|
assert block_body.shard_transitions[shard] == ShardTransition()
|
|
```
|
|
|
|
#### Light client processing
|
|
|
|
```python
|
|
def process_light_client_signatures(state: BeaconState, block_body: BeaconBlockBody) -> None:
|
|
committee = get_light_client_committee(state, get_current_epoch(state))
|
|
total_reward = Gwei(0)
|
|
signer_pubkeys = []
|
|
for bit_index, participant_index in enumerate(committee):
|
|
if block_body.light_client_signature_bitfield[bit_index]:
|
|
signer_pubkeys.append(state.validators[participant_index].pubkey)
|
|
increase_balance(state, participant_index, get_base_reward(state, participant_index))
|
|
total_reward += get_base_reward(state, participant_index)
|
|
|
|
increase_balance(state, get_beacon_proposer_index(state), Gwei(total_reward // PROPOSER_REWARD_QUOTIENT))
|
|
|
|
slot = get_previous_slot(state.slot)
|
|
signing_root = compute_signing_root(get_block_root_at_slot(state, slot),
|
|
get_domain(state, DOMAIN_LIGHT_CLIENT, compute_epoch_at_slot(slot)))
|
|
return bls.FastAggregateVerify(signer_pubkeys, signing_root, signature=block_body.light_client_signature)
|
|
```
|
|
|
|
|
|
### Epoch transition
|
|
|
|
This epoch transition overrides the phase0 epoch transition:
|
|
|
|
```python
|
|
def process_epoch(state: BeaconState) -> None:
|
|
process_justification_and_finalization(state)
|
|
process_rewards_and_penalties(state)
|
|
process_registry_updates(state)
|
|
process_reveal_deadlines(state)
|
|
process_slashings(state)
|
|
process_final_updates(state)
|
|
process_custody_final_updates(state)
|
|
process_online_tracking(state)
|
|
process_light_client_committee_updates(state)
|
|
```
|
|
|
|
#### Custody game updates
|
|
|
|
`process_reveal_deadlines` and `process_custody_final_updates` are defined in [the Custody Game spec](./1_custody-game.md),
|
|
|
|
#### Online-tracking
|
|
|
|
```python
|
|
def process_online_tracking(state: BeaconState) -> None:
|
|
# Slowly remove validators from the "online" set if they do not show up
|
|
for index in range(len(state.validators)):
|
|
if state.online_countdown[index] != 0:
|
|
state.online_countdown[index] = state.online_countdown[index] - 1
|
|
|
|
# Process pending attestations
|
|
for pending_attestation in state.current_epoch_attestations + state.previous_epoch_attestations:
|
|
for index in get_attesting_indices(state, pending_attestation.data, pending_attestation.aggregation_bits):
|
|
state.online_countdown[index] = ONLINE_PERIOD
|
|
```
|
|
|
|
#### Light client committee updates
|
|
|
|
```python
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def process_light_client_committee_updates(state: BeaconState) -> None:
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# Update light client committees
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if get_current_epoch(state) % LIGHT_CLIENT_COMMITTEE_PERIOD == 0:
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state.current_light_committee = state.next_light_committee
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new_committee = get_light_client_committee(state, get_current_epoch(state) + LIGHT_CLIENT_COMMITTEE_PERIOD)
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state.next_light_committee = committee_to_compact_committee(state, new_committee)
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```
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