775 lines
29 KiB
Markdown
775 lines
29 KiB
Markdown
# Ethereum 2.0 Sharding -- Beacon Chain changes
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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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<!-- 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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- [Configuration](#configuration)
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- [Misc](#misc)
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- [Shard block configs](#shard-block-configs)
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- [Precomputed size verification points](#precomputed-size-verification-points)
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- [Gwei values](#gwei-values)
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- [Time parameters](#time-parameters)
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- [Domain types](#domain-types)
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- [Updated containers](#updated-containers)
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- [`AttestationData`](#attestationdata)
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- [`BeaconBlockBody`](#beaconblockbody)
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- [`BeaconState`](#beaconstate)
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- [New containers](#new-containers)
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- [`DataCommitment`](#datacommitment)
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- [`ShardBlobBodySummary`](#shardblobbodysummary)
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- [`ShardBlobHeader`](#shardblobheader)
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- [`SignedShardBlobHeader`](#signedshardblobheader)
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- [`PendingShardHeader`](#pendingshardheader)
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- [`ShardBlobReference`](#shardblobreference)
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- [`SignedShardBlobReference`](#signedshardblobreference)
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- [`ShardProposerSlashing`](#shardproposerslashing)
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- [Helper functions](#helper-functions)
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- [Misc](#misc-1)
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- [`next_power_of_two`](#next_power_of_two)
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- [`compute_previous_slot`](#compute_previous_slot)
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- [`compute_updated_gasprice`](#compute_updated_gasprice)
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- [`compute_committee_source_epoch`](#compute_committee_source_epoch)
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- [Beacon state accessors](#beacon-state-accessors)
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- [Updated `get_committee_count_per_slot`](#updated-get_committee_count_per_slot)
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- [`get_active_shard_count`](#get_active_shard_count)
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- [`get_shard_committee`](#get_shard_committee)
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- [`compute_proposer_index`](#compute_proposer_index)
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- [`get_shard_proposer_index`](#get_shard_proposer_index)
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- [`get_start_shard`](#get_start_shard)
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- [`compute_shard_from_committee_index`](#compute_shard_from_committee_index)
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- [`compute_committee_index_from_shard`](#compute_committee_index_from_shard)
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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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- [Updated `process_attestation`](#updated-process_attestation)
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- [`update_pending_votes`](#update_pending_votes)
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- [`process_shard_header`](#process_shard_header)
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- [Shard Proposer slashings](#shard-proposer-slashings)
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- [Epoch transition](#epoch-transition)
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- [Pending headers](#pending-headers)
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- [Shard epoch increment](#shard-epoch-increment)
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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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This document describes the extensions made to the Phase 0 design of The Beacon Chain to support data sharding,
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based on the ideas [here](https://hackmd.io/G-Iy5jqyT7CXWEz8Ssos8g) and more broadly [here](https://arxiv.org/abs/1809.09044),
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using KZG10 commitments to commit to data to remove any need for fraud proofs (and hence, safety-critical synchrony assumptions) in the design.
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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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| `BLSCommitment` | `Bytes48` | A G1 curve point |
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| `BLSPoint` | `uint256` | A number `x` in the range `0 <= x < MODULUS` |
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## Constants
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The following values are (non-configurable) constants used throughout the specification.
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| Name | Value | Notes |
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| - | - | - |
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| `PRIMITIVE_ROOT_OF_UNITY` | `5` | Primitive root of unity of the BLS12_381 (inner) modulus |
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| `DATA_AVAILABILITY_INVERSE_CODING_RATE` | `2**1` (= 2) | Factor by which samples are extended for data availability encoding |
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| `POINTS_PER_SAMPLE` | `uint64(2**3)` (= 8) | 31 * 8 = 248 bytes |
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| `MODULUS` | `0x73eda753299d7d483339d80809a1d80553bda402fffe5bfeffffffff00000001` (curve order of BLS12_381) |
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## Configuration
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### Misc
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| Name | Value | Notes |
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| - | - | - |
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| `MAX_SHARDS` | `uint64(2**10)` (= 1,024) | Theoretical max shard count (used to determine data structure sizes) |
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| `INITIAL_ACTIVE_SHARDS` | `uint64(2**6)` (= 64) | Initial shard count |
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| `GASPRICE_ADJUSTMENT_COEFFICIENT` | `uint64(2**3)` (= 8) | Gasprice may decrease/increase by at most exp(1 / this value) *per epoch* |
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| `MAX_SHARD_HEADERS_PER_SHARD` | `4` | |
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| `MAX_SHARD_PROPOSER_SLASHINGS` | `2**4` (= 16) | Maximum amount of shard proposer slashing operations per block |
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### Shard block configs
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| Name | Value | Notes |
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| - | - | - |
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| `MAX_SAMPLES_PER_BLOCK` | `uint64(2**11)` (= 2,048) | 248 * 2,048 = 507,904 bytes |
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| `TARGET_SAMPLES_PER_BLOCK` | `uint64(2**10)` (= 1,024) | 248 * 1,024 = 253,952 bytes |
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### Precomputed size verification points
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| Name | Value |
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| - | - |
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| `G1_SETUP` | Type `List[G1]`. The G1-side trusted setup `[G, G*s, G*s**2....]`; note that the first point is the generator. |
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| `G2_SETUP` | Type `List[G2]`. The G2-side trusted setup `[G, G*s, G*s**2....]` |
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| `ROOT_OF_UNITY` | `pow(PRIMITIVE_ROOT_OF_UNITY, (MODULUS - 1) // int(MAX_SAMPLES_PER_BLOCK * POINTS_PER_SAMPLE), MODULUS)` |
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### Gwei values
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| Name | Value | Unit | Description |
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| - | - | - | - |
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| `MAX_GASPRICE` | `Gwei(2**33)` (= 8,589,934,592) | Gwei | Max gasprice charged for a TARGET-sized shard block |
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| `MIN_GASPRICE` | `Gwei(2**3)` (= 8) | Gwei | Min gasprice charged for a TARGET-sized shard block |
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### Time parameters
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| Name | Value | Unit | Duration |
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| - | - | :-: | :-: |
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| `SHARD_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_SHARD_PROPOSER` | `DomainType('0x80000000')` |
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| `DOMAIN_SHARD_COMMITTEE` | `DomainType('0x81000000')` |
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## Updated containers
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The following containers have updated definitions to support Sharding.
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### `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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# Shard header root
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shard_header_root: Root # [New in Sharding]
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```
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### `BeaconBlockBody`
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```python
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class BeaconBlockBody(merge.BeaconBlockBody): # [extends The Merge block body]
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shard_proposer_slashings: List[ShardProposerSlashing, MAX_SHARD_PROPOSER_SLASHINGS]
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shard_headers: List[SignedShardBlobHeader, MAX_SHARDS * MAX_SHARD_HEADERS_PER_SHARD]
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```
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### `BeaconState`
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```python
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class BeaconState(merge.BeaconState): # [extends The Merge block body]
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# [Updated fields]
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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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# [New fields]
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previous_epoch_pending_shard_headers: List[PendingShardHeader, MAX_SHARDS * MAX_SHARD_HEADERS_PER_SHARD * SLOTS_PER_EPOCH]
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current_epoch_pending_shard_headers: List[PendingShardHeader, MAX_SHARDS * MAX_SHARD_HEADERS_PER_SHARD * SLOTS_PER_EPOCH]
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grandparent_epoch_confirmed_commitments: Vector[Vector[DataCommitment, SLOTS_PER_EPOCH], MAX_SHARDS]
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shard_gasprice: uint64
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current_epoch_start_shard: Shard
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```
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## New containers
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The shard data itself is network-layer only, and can be found in the [P2P specification](./p2p-interface.md).
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The beacon chain registers just the commitments of the shard data.
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### `DataCommitment`
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```python
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class DataCommitment(Container):
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# KZG10 commitment to the data
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point: BLSCommitment
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# Length of the data in samples
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length: uint64
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```
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### `ShardBlobBodySummary`
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```python
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class ShardBlobBodySummary(Container):
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# The actual data commitment
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commitment: DataCommitment
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# Proof that the degree < commitment.length
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degree_proof: BLSCommitment
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# Hash-tree-root as summary of the data field
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data_root: Root
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# Latest block root of the Beacon Chain, before shard_blob.slot
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beacon_block_root: Root
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```
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### `ShardBlobHeader`
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```python
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class ShardBlobHeader(Container):
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# Slot and shard that this header is intended for
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slot: Slot
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shard: Shard
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body_summary: ShardBlobBodySummary
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# Proposer of the shard-blob
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proposer_index: ValidatorIndex
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```
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### `SignedShardBlobHeader`
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```python
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class SignedShardBlobHeader(Container):
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message: ShardBlobHeader
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signature: BLSSignature
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```
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### `PendingShardHeader`
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```python
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class PendingShardHeader(Container):
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# Slot and shard that this header is intended for
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slot: Slot
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shard: Shard
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# KZG10 commitment to the data
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commitment: DataCommitment
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# hash_tree_root of the ShardHeader (stored so that attestations can be checked against it)
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root: Root
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# Who voted for the header
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votes: Bitlist[MAX_VALIDATORS_PER_COMMITTEE]
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# Has this header been confirmed?
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confirmed: boolean
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```
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### `ShardBlobReference`
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```python
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class ShardBlobReference(Container):
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# Slot and shard that this reference is intended for
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slot: Slot
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shard: Shard
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# Hash-tree-root of commitment data
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body_root: Root
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# Proposer of the shard-blob
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proposer_index: ValidatorIndex
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```
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### `SignedShardBlobReference`
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```python
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class SignedShardBlobReference(Container):
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message: ShardBlobReference
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signature: BLSSignature
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```
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### `ShardProposerSlashing`
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```python
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class ShardProposerSlashing(Container):
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signed_reference_1: SignedShardBlobReference
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signed_reference_2: SignedShardBlobReference
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```
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## Helper functions
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### Misc
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#### `next_power_of_two`
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```python
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def next_power_of_two(x):
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return 2 ** ((x - 1).bit_length())
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```
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#### `compute_previous_slot`
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```python
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def compute_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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#### `compute_updated_gasprice`
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```python
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def compute_updated_gasprice(prev_gasprice: Gwei, shard_block_length: uint64, adjustment_quotient: uint64) -> Gwei:
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if shard_block_length > TARGET_SAMPLES_PER_BLOCK:
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delta = max(1, prev_gasprice * (shard_block_length - TARGET_SAMPLES_PER_BLOCK)
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// TARGET_SAMPLES_PER_BLOCK // adjustment_quotient)
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return min(prev_gasprice + delta, MAX_GASPRICE)
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else:
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delta = max(1, prev_gasprice * (TARGET_SAMPLES_PER_BLOCK - shard_block_length)
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// TARGET_SAMPLES_PER_BLOCK // adjustment_quotient)
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return max(prev_gasprice, MIN_GASPRICE + delta) - delta
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```
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#### `compute_committee_source_epoch`
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```python
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def compute_committee_source_epoch(epoch: Epoch, period: uint64) -> Epoch:
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"""
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Return the source epoch for computing the committee.
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"""
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source_epoch = Epoch(epoch - epoch % period)
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if source_epoch >= period:
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source_epoch -= period # `period` epochs lookahead
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return source_epoch
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```
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### Beacon state accessors
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#### Updated `get_committee_count_per_slot`
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```python
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def get_committee_count_per_slot(state: BeaconState, epoch: Epoch) -> uint64:
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"""
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Return the number of committees in each slot for the given ``epoch``.
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"""
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return max(uint64(1), min(
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get_active_shard_count(state, epoch),
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uint64(len(get_active_validator_indices(state, epoch))) // SLOTS_PER_EPOCH // TARGET_COMMITTEE_SIZE,
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))
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```
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#### `get_active_shard_count`
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```python
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def get_active_shard_count(state: BeaconState, epoch: Epoch) -> uint64:
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"""
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Return the number of active shards.
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Note that this puts an upper bound on the number of committees per slot.
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"""
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return INITIAL_ACTIVE_SHARDS
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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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"""
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Return the shard committee of the given ``epoch`` of the given ``shard``.
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"""
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source_epoch = compute_committee_source_epoch(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(
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indices=active_validator_indices,
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seed=seed,
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index=shard,
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count=get_active_shard_count(beacon_state, epoch),
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)
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```
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#### `compute_proposer_index`
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Updated version to get a proposer index that will only allow proposers with a certain minimum balance,
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ensuring that the balance is always sufficient to cover gas costs.
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```python
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def compute_proposer_index(beacon_state: BeaconState,
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indices: Sequence[ValidatorIndex],
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seed: Bytes32,
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min_effective_balance: GWei = GWei(0)) -> ValidatorIndex:
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"""
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Return from ``indices`` a random index sampled by effective balance.
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"""
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assert len(indices) > 0
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MAX_RANDOM_BYTE = 2**8 - 1
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i = uint64(0)
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total = uint64(len(indices))
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while True:
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candidate_index = indices[compute_shuffled_index(i % total, total, seed)]
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random_byte = hash(seed + uint_to_bytes(uint64(i // 32)))[i % 32]
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effective_balance = beacon_state.validators[candidate_index].effective_balance
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if effective_balance <= min_effective_balance:
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continue
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if effective_balance * MAX_RANDOM_BYTE >= MAX_EFFECTIVE_BALANCE * random_byte:
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return candidate_index
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i += 1
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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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"""
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Return the proposer's index of shard block at ``slot``.
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"""
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epoch = compute_epoch_at_slot(slot)
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committee = get_shard_committee(beacon_state, epoch, shard)
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seed = hash(get_seed(beacon_state, epoch, DOMAIN_BEACON_PROPOSER) + uint_to_bytes(slot))
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# Proposer must have sufficient balance to pay for worst case fee burn
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EFFECTIVE_BALANCE_MAX_DOWNWARD_DEVIATION = (
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(EFFECTIVE_BALANCE_INCREMENT - EFFECTIVE_BALANCE_INCREMENT)
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* HYSTERESIS_DOWNWARD_MULTIPLIER // HYSTERESIS_QUOTIENT
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)
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min_effective_balance = (
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beacon_state.shard_gasprice * MAX_SAMPLES_PER_BLOCK // TARGET_SAMPLES_PER_BLOCK
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+ EFFECTIVE_BALANCE_MAX_DOWNWARD_DEVIATION
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)
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return compute_proposer_index(beacon_state, committee, seed, min_effective_balance)
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```
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#### `get_start_shard`
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```python
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def get_start_shard(state: BeaconState, slot: Slot) -> Shard:
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"""
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Return the start shard at ``slot``.
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"""
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current_epoch_start_slot = compute_start_slot_at_epoch(get_current_epoch(state))
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shard = state.current_epoch_start_shard
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if slot > current_epoch_start_slot:
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# Current epoch or the next epoch lookahead
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for _slot in range(current_epoch_start_slot, slot):
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committee_count = get_committee_count_per_slot(state, compute_epoch_at_slot(Slot(_slot)))
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active_shard_count = get_active_shard_count(state, compute_epoch_at_slot(Slot(_slot)))
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shard = (shard + committee_count) % active_shard_count
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elif slot < current_epoch_start_slot:
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# Previous epoch
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for _slot in list(range(slot, current_epoch_start_slot))[::-1]:
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committee_count = get_committee_count_per_slot(state, compute_epoch_at_slot(Slot(_slot)))
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active_shard_count = get_active_shard_count(state, compute_epoch_at_slot(Slot(_slot)))
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# Ensure positive
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shard = (shard + active_shard_count - committee_count) % active_shard_count
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return Shard(shard)
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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, slot: Slot, index: CommitteeIndex) -> Shard:
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active_shards = get_active_shard_count(state, compute_epoch_at_slot(slot))
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return Shard((index + get_start_shard(state, slot)) % active_shards)
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```
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#### `compute_committee_index_from_shard`
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```python
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def compute_committee_index_from_shard(state: BeaconState, slot: Slot, shard: Shard) -> CommitteeIndex:
|
|
active_shards = get_active_shard_count(state, compute_epoch_at_slot(slot))
|
|
return CommitteeIndex((active_shards + shard - get_start_shard(state, slot)) % active_shards)
|
|
```
|
|
|
|
|
|
### 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)
|
|
process_operations(state, block.body) # [Modified in Sharding]
|
|
process_execution_payload(state, block.body) # [New in Merge]
|
|
```
|
|
|
|
#### 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 shard proposer slashing processing
|
|
for_ops(body.shard_proposer_slashings, process_shard_proposer_slashing)
|
|
# Limit is dynamic based on active shard count
|
|
assert len(body.shard_headers) <= MAX_SHARD_HEADERS_PER_SHARD * get_active_shard_count(state, get_current_epoch(state))
|
|
for_ops(body.shard_headers, process_shard_header)
|
|
# New attestation processing
|
|
for_ops(body.attestations, process_attestation)
|
|
for_ops(body.deposits, process_deposit)
|
|
for_ops(body.voluntary_exits, process_voluntary_exit)
|
|
```
|
|
|
|
### New Attestation processing
|
|
|
|
#### Updated `process_attestation`
|
|
|
|
```python
|
|
def process_attestation(state: BeaconState, attestation: Attestation) -> None:
|
|
phase0.process_attestation(state, attestation)
|
|
update_pending_votes(state, attestation)
|
|
```
|
|
|
|
#### `update_pending_votes`
|
|
|
|
```python
|
|
def update_pending_votes(state: BeaconState, attestation: Attestation) -> None:
|
|
# Find and update the PendingShardHeader object, invalid block if pending header not in state
|
|
if compute_epoch_at_slot(attestation.data.slot) == get_current_epoch(state):
|
|
pending_headers = state.current_epoch_pending_shard_headers
|
|
else:
|
|
pending_headers = state.previous_epoch_pending_shard_headers
|
|
pending_header = None
|
|
for header in pending_headers:
|
|
if header.root == attestation.data.shard_header_root:
|
|
pending_header = header
|
|
assert pending_header is not None
|
|
assert pending_header.slot == attestation.data.slot
|
|
assert pending_header.shard == compute_shard_from_committee_index(
|
|
state,
|
|
attestation.data.slot,
|
|
attestation.data.index,
|
|
)
|
|
for i in range(len(pending_header.votes)):
|
|
pending_header.votes[i] = pending_header.votes[i] or attestation.aggregation_bits[i]
|
|
|
|
# Check if the PendingShardHeader is eligible for expedited confirmation
|
|
# Requirement 1: nothing else confirmed
|
|
all_candidates = [
|
|
c for c in pending_headers if
|
|
(c.slot, c.shard) == (pending_header.slot, pending_header.shard)
|
|
]
|
|
if True in [c.confirmed for c in all_candidates]:
|
|
return
|
|
|
|
# Requirement 2: >= 2/3 of balance attesting
|
|
participants = get_attesting_indices(state, attestation.data, pending_header.votes)
|
|
participants_balance = get_total_balance(state, participants)
|
|
full_committee = get_beacon_committee(state, attestation.data.slot, attestation.data.index)
|
|
full_committee_balance = get_total_balance(state, full_committee)
|
|
if participants_balance * 3 >= full_committee_balance * 2:
|
|
pending_header.confirmed = True
|
|
```
|
|
|
|
#### `process_shard_header`
|
|
|
|
```python
|
|
def process_shard_header(state: BeaconState,
|
|
signed_header: SignedShardBlobHeader) -> None:
|
|
header = signed_header.message
|
|
# Verify the header is not 0, and not from the future.
|
|
assert Slot(0) < header.slot <= state.slot
|
|
header_epoch = compute_epoch_at_slot(header.slot)
|
|
# Verify that the header is within the processing time window
|
|
assert header_epoch in [get_previous_epoch(state), get_current_epoch(state)]
|
|
# Verify that the shard is active
|
|
assert header.shard < get_active_shard_count(state, header_epoch)
|
|
# Verify that the block root matches,
|
|
# to ensure the header will only be included in this specific Beacon Chain sub-tree.
|
|
assert header.beacon_block_root == get_block_root_at_slot(state, header.slot - 1)
|
|
# Verify proposer
|
|
assert header.proposer_index == get_shard_proposer_index(state, header.slot, header.shard)
|
|
# Verify signature
|
|
signing_root = compute_signing_root(header, get_domain(state, DOMAIN_SHARD_HEADER))
|
|
assert bls.Verify(state.validators[header.proposer_index].pubkey, signing_root, signed_header.signature)
|
|
|
|
# Verify the length by verifying the degree.
|
|
body_summary = header.body_summary
|
|
if body_summary.commitment.length == 0:
|
|
assert body_summary.degree_proof == G1_SETUP[0]
|
|
assert (
|
|
bls.Pairing(body_summary.degree_proof, G2_SETUP[0])
|
|
== bls.Pairing(body_summary.commitment.point, G2_SETUP[-body_summary.commitment.length])
|
|
)
|
|
|
|
# Get the correct pending header list
|
|
if header_epoch == get_current_epoch(state):
|
|
pending_headers = state.current_epoch_pending_shard_headers
|
|
else:
|
|
pending_headers = state.previous_epoch_pending_shard_headers
|
|
|
|
header_root = hash_tree_root(header)
|
|
# Check that this header is not yet in the pending list
|
|
assert header_root not in [pending_header.root for pending_header in pending_headers]
|
|
|
|
# Include it in the pending list
|
|
index = compute_committee_index_from_shard(state, header.slot, header.shard)
|
|
committee_length = len(get_beacon_committee(state, header.slot, index))
|
|
pending_headers.append(PendingShardHeader(
|
|
slot=header.slot,
|
|
shard=header.shard,
|
|
commitment=body_summary.commitment,
|
|
root=header_root,
|
|
votes=Bitlist[MAX_VALIDATORS_PER_COMMITTEE]([0] * committee_length),
|
|
confirmed=False,
|
|
))
|
|
```
|
|
|
|
The degree proof works as follows. For a block `B` with length `l` (so `l` values in `[0...l - 1]`, seen as a polynomial `B(X)` which takes these values),
|
|
the length proof is the commitment to the polynomial `B(X) * X**(MAX_DEGREE + 1 - l)`,
|
|
where `MAX_DEGREE` is the maximum power of `s` available in the setup, which is `MAX_DEGREE = len(G2_SETUP) - 1`.
|
|
The goal is to ensure that a proof can only be constructed if `deg(B) < l` (there are not hidden higher-order terms in the polynomial, which would thwart reconstruction).
|
|
|
|
##### Shard Proposer slashings
|
|
|
|
```python
|
|
def process_shard_proposer_slashing(state: BeaconState, proposer_slashing: ShardProposerSlashing) -> None:
|
|
reference_1 = proposer_slashing.signed_reference_1.message
|
|
reference_2 = proposer_slashing.signed_reference_2.message
|
|
|
|
# Verify header slots match
|
|
assert reference_1.slot == reference_2.slot
|
|
# Verify header shards match
|
|
assert reference_1.shard == reference_2.shard
|
|
# Verify header proposer indices match
|
|
assert reference_1.proposer_index == reference_2.proposer_index
|
|
# Verify the headers are different (i.e. different body)
|
|
assert reference_1 != reference_2
|
|
# Verify the proposer is slashable
|
|
proposer = state.validators[reference_1.proposer_index]
|
|
assert is_slashable_validator(proposer, get_current_epoch(state))
|
|
# Verify signatures
|
|
for signed_header in (proposer_slashing.signed_reference_1, proposer_slashing.signed_reference_2):
|
|
domain = get_domain(state, DOMAIN_SHARD_PROPOSER, compute_epoch_at_slot(signed_header.message.slot))
|
|
signing_root = compute_signing_root(signed_header.message, domain)
|
|
assert bls.Verify(proposer.pubkey, signing_root, signed_header.signature)
|
|
|
|
slash_validator(state, reference_1.proposer_index)
|
|
```
|
|
|
|
### Epoch transition
|
|
|
|
This epoch transition overrides the Merge epoch transition:
|
|
|
|
```python
|
|
def process_epoch(state: BeaconState) -> None:
|
|
process_justification_and_finalization(state)
|
|
process_rewards_and_penalties(state)
|
|
process_registry_updates(state)
|
|
|
|
process_slashings(state)
|
|
|
|
# Sharding
|
|
process_pending_headers(state)
|
|
process_confirmed_header_fees(state)
|
|
reset_pending_headers(state)
|
|
|
|
# Final updates
|
|
# Phase 0
|
|
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_record_updates(state)
|
|
|
|
process_shard_epoch_increment(state)
|
|
```
|
|
|
|
#### Pending headers
|
|
|
|
```python
|
|
def process_pending_headers(state: BeaconState) -> None:
|
|
# Pending header processing applies to the previous epoch.
|
|
# Skip if `GENESIS_EPOCH` because no prior epoch to process.
|
|
if get_current_epoch(state) == GENESIS_EPOCH:
|
|
return
|
|
|
|
previous_epoch_start_slot = compute_start_slot_at_epoch(get_previous_epoch(state))
|
|
for slot in range(previous_epoch_start_slot, previous_epoch_start_slot + SLOTS_PER_EPOCH):
|
|
for shard in range(get_active_shard_count(state)):
|
|
# Pending headers for this (slot, shard) combo
|
|
candidates = [
|
|
c for c in state.previous_epoch_pending_shard_headers
|
|
if (c.slot, c.shard) == (slot, shard)
|
|
]
|
|
# The entire committee (and its balance)
|
|
full_committee = get_beacon_committee(state, slot, shard)
|
|
full_committee_balance = get_total_balance(state, full_committee)
|
|
# If any candidates already confirmed, skip
|
|
if True in [c.confirmed for c in candidates]:
|
|
continue
|
|
|
|
# The set of voters who voted for each header (and their total balances)
|
|
voting_sets = [
|
|
[v for i, v in enumerate(full_committee) if c.votes[i]]
|
|
for c in candidates
|
|
]
|
|
voting_balances = [
|
|
get_total_balance(state, voters)
|
|
for voters in voting_sets
|
|
]
|
|
# Get the index with the most total balance voting for them.
|
|
# NOTE: if two choices get exactly the same voting balance,
|
|
# the candidate earlier in the list wins
|
|
if max(voting_balances) > 0:
|
|
winning_index = voting_balances.index(max(voting_balances))
|
|
else:
|
|
# If no votes, zero wins
|
|
winning_index = [c.root for c in candidates].index(Root())
|
|
candidates[winning_index].confirmed = True
|
|
for slot_index in range(SLOTS_PER_EPOCH):
|
|
for shard in range(SHARD_COUNT):
|
|
state.grandparent_epoch_confirmed_commitments[shard][slot_index] = DataCommitment()
|
|
confirmed_headers = [candidate for candidate in state.previous_epoch_pending_shard_headers if candidate.confirmed]
|
|
for header in confirmed_headers:
|
|
state.grandparent_epoch_confirmed_commitments[c.shard][c.slot % SLOTS_PER_EPOCH] = c.commitment
|
|
```
|
|
|
|
```python
|
|
def charge_confirmed_header_fees(state: BeaconState) -> None:
|
|
new_gasprice = state.shard_gasprice
|
|
adjustment_quotient = (
|
|
get_active_shard_count(state, get_current_epoch(state))
|
|
* SLOTS_PER_EPOCH * GASPRICE_ADJUSTMENT_COEFFICIENT
|
|
)
|
|
previous_epoch_start_slot = compute_start_slot_at_epoch(get_previous_epoch(state))
|
|
for slot in range(previous_epoch_start_slot, previous_epoch_start_slot + SLOTS_PER_EPOCH):
|
|
for shard in range(SHARD_COUNT):
|
|
confirmed_candidates = [
|
|
c for c in state.previous_epoch_pending_shard_headers
|
|
if (c.slot, c.shard, c.confirmed) == (slot, shard, True)
|
|
]
|
|
if not any(confirmed_candidates):
|
|
continue
|
|
candidate = confirmed_candidates[0]
|
|
|
|
# Charge EIP 1559 fee
|
|
proposer = get_shard_proposer(state, slot, shard)
|
|
fee = (
|
|
(state.shard_gasprice * candidate.commitment.length)
|
|
// TARGET_SAMPLES_PER_BLOCK
|
|
)
|
|
decrease_balance(state, proposer, fee)
|
|
|
|
# Track updated gas price
|
|
new_gasprice = compute_updated_gasprice(
|
|
new_gasprice,
|
|
candidate.commitment.length,
|
|
adjustment_quotient,
|
|
)
|
|
state.shard_gasprice = new_gasprice
|
|
```
|
|
|
|
```python
|
|
def reset_pending_headers(state: BeaconState) -> None:
|
|
state.previous_epoch_pending_shard_headers = state.current_epoch_pending_shard_headers
|
|
state.current_epoch_pending_shard_headers = []
|
|
# Add dummy "empty" PendingShardHeader (default vote for if no shard header available)
|
|
next_epoch = get_current_epoch(state) + 1
|
|
next_epoch_start_slot = compute_start_slot_at_epoch(next_epoch)
|
|
for slot in range(next_epoch_start_slot, next_epoch_start_slot + SLOTS_IN_EPOCH):
|
|
for index in range(get_committee_count_per_slot(next_epoch)):
|
|
shard = compute_shard_from_committee_index(state, slot, index)
|
|
committee_length = len(get_beacon_committee(state, slot, shard))
|
|
state.current_epoch_pending_shard_headers.append(PendingShardHeader(
|
|
slot=slot,
|
|
shard=shard,
|
|
commitment=DataCommitment(),
|
|
root=Root(),
|
|
votes=Bitlist[MAX_VALIDATORS_PER_COMMITTEE]([0] * committee_length),
|
|
confirmed=False,
|
|
))
|
|
```
|
|
|
|
#### Shard epoch increment
|
|
|
|
```python
|
|
def process_shard_epoch_increment(state: BeaconState) -> None:
|
|
# Update current_epoch_start_shard
|
|
state.current_epoch_start_shard = get_start_shard(state, Slot(state.slot + 1))
|
|
```
|