889 lines
34 KiB
Markdown
889 lines
34 KiB
Markdown
# Sharding -- The Beacon Chain
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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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- [Glossary](#glossary)
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- [Custom types](#custom-types)
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- [Constants](#constants)
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- [Misc](#misc)
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- [Domain types](#domain-types)
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- [Shard Work Status](#shard-work-status)
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- [Misc](#misc-1)
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- [Participation flag indices](#participation-flag-indices)
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- [Incentivization weights](#incentivization-weights)
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- [Preset](#preset)
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- [Misc](#misc-2)
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- [Shard blob samples](#shard-blob-samples)
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- [Precomputed size verification points](#precomputed-size-verification-points)
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- [Gwei values](#gwei-values)
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- [Configuration](#configuration)
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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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- [`Builder`](#builder)
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- [`DataCommitment`](#datacommitment)
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- [`AttestedDataCommitment`](#attesteddatacommitment)
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- [`ShardBlobBody`](#shardblobbody)
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- [`ShardBlobBodySummary`](#shardblobbodysummary)
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- [`ShardBlob`](#shardblob)
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- [`ShardBlobHeader`](#shardblobheader)
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- [`SignedShardBlob`](#signedshardblob)
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- [`SignedShardBlobHeader`](#signedshardblobheader)
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- [`PendingShardHeader`](#pendingshardheader)
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- [`ShardBlobReference`](#shardblobreference)
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- [`ShardProposerSlashing`](#shardproposerslashing)
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- [`ShardWork`](#shardwork)
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- [Helper functions](#helper-functions)
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- [Misc](#misc-3)
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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_sample_price`](#compute_updated_sample_price)
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- [`compute_committee_source_epoch`](#compute_committee_source_epoch)
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- [`batch_apply_participation_flag`](#batch_apply_participation_flag)
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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_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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- [Extended Attestation processing](#extended-attestation-processing)
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- [`process_shard_header`](#process_shard_header)
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- [`process_shard_proposer_slashing`](#process_shard_proposer_slashing)
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- [Epoch transition](#epoch-transition)
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- [`process_pending_shard_confirmations`](#process_pending_shard_confirmations)
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- [`reset_pending_shard_work`](#reset_pending_shard_work)
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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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### Glossary
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- **Data**: A list of KZG points, to translate a byte string into
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- **Blob**: Data with commitments and meta-data, like a flattened bundle of L2 transactions.
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- **Builder**: Independent actor that builds blobs and bids for proposal slots via fee-paying blob-headers, responsible for availability.
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- **Shard proposer**: Validator taking bids from blob builders for shard data opportunity, co-signs with builder to propose the blob.
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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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| `BuilderIndex` | `uint64` | Builder registry index |
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## Constants
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The following values are (non-configurable) constants used throughout the specification.
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### Misc
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| Name | Value | Notes |
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| - | - | - |
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| `PRIMITIVE_ROOT_OF_UNITY` | `7` | 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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### Domain types
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| Name | Value |
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| - | - |
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| `DOMAIN_SHARD_BLOB` | `DomainType('0x80000000')` |
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### Shard Work Status
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| Name | Value | Notes |
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| - | - | - |
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| `SHARD_WORK_UNCONFIRMED` | `0` | Unconfirmed, nullified after confirmation time elapses |
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| `SHARD_WORK_CONFIRMED` | `1` | Confirmed, reduced to just the commitment |
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| `SHARD_WORK_PENDING` | `2` | Pending, a list of competing headers |
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### Misc
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TODO: `PARTICIPATION_FLAG_WEIGHTS` backwards-compatibility is difficult, depends on usage.
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| Name | Value |
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| - | - |
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| `PARTICIPATION_FLAG_WEIGHTS` | `[TIMELY_SOURCE_WEIGHT, TIMELY_TARGET_WEIGHT, TIMELY_HEAD_WEIGHT, TIMELY_SHARD_WEIGHT]` |
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### Participation flag indices
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| Name | Value |
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| - | - |
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| `TIMELY_SHARD_FLAG_INDEX` | `3` |
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### Incentivization weights
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TODO: determine weight for shard attestations
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| Name | Value |
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| - | - |
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| `TIMELY_SHARD_WEIGHT` | `uint64(8)` |
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TODO: `WEIGHT_DENOMINATOR` needs to be adjusted, but this breaks a lot of Altair code.
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## Preset
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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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| `SAMPLE_PRICE_ADJUSTMENT_COEFFICIENT` | `uint64(2**3)` (= 8) | Sample price may decrease/increase by at most exp(1 / this value) *per epoch* |
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| `MAX_SHARD_PROPOSER_SLASHINGS` | `2**4` (= 16) | Maximum amount of shard proposer slashing operations per block |
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| `MAX_SHARD_HEADERS_PER_SHARD` | `4` | |
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| `SHARD_STATE_MEMORY_SLOTS` | `uint64(2**8)` (= 256) | Number of slots for which shard commitments and confirmation status is directly available in the state |
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| `BLOB_BUILDER_REGISTRY_LIMIT` | `uint64(2**40)` (= 1,099,511,627,776) | shard blob builders |
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### Shard blob samples
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| Name | Value | Notes |
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| `MAX_SAMPLES_PER_BLOB` | `uint64(2**11)` (= 2,048) | 248 * 2,048 = 507,904 bytes |
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| `TARGET_SAMPLES_PER_BLOB` | `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_BLOB * 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_SAMPLE_PRICE` | `Gwei(2**33)` (= 8,589,934,592) | Gwei | Max sample charged for a TARGET-sized shard blob |
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| `MIN_SAMPLE_PRICE` | `Gwei(2**3)` (= 8) | Gwei | Min sample price charged for a TARGET-sized shard blob |
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## Configuration
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Note: Some preset variables may become run-time configurable for testnets, but default to a preset while the spec is unstable.
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E.g. `INITIAL_ACTIVE_SHARDS`, `MAX_SAMPLES_PER_BLOB` and `TARGET_SAMPLES_PER_BLOB`.
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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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# Hash-tree-root of ShardBlob
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shard_blob_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(bellatrix.BeaconBlockBody): # [extends Bellatrix 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(bellatrix.BeaconState):
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# Blob builder registry.
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blob_builders: List[Builder, BLOB_BUILDER_REGISTRY_LIMIT]
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blob_builder_balances: List[Gwei, BLOB_BUILDER_REGISTRY_LIMIT]
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# A ring buffer of the latest slots, with information per active shard.
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shard_buffer: Vector[List[ShardWork, MAX_SHARDS], SHARD_STATE_MEMORY_SLOTS]
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shard_sample_price: uint64
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```
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## New containers
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### `Builder`
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```python
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class Builder(Container):
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pubkey: BLSPubkey
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# TODO: fields for either an expiry mechanism (refunding execution account with remaining balance)
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# and/or a builder-transaction mechanism.
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```
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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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samples_count: uint64
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```
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### `AttestedDataCommitment`
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```python
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class AttestedDataCommitment(Container):
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# KZG10 commitment to the data, and length
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commitment: DataCommitment
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# hash_tree_root of the ShardBlobHeader (stored so that attestations can be checked against it)
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root: Root
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# The proposer who included the shard-header
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includer_index: ValidatorIndex
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```
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### `ShardBlobBody`
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Unsigned shard data, bundled by a shard-builder.
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Unique, signing different bodies as shard proposer for the same `(slot, shard)` is slashable.
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```python
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class ShardBlobBody(Container):
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# The actual data commitment
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commitment: DataCommitment
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# Proof that the degree < commitment.samples_count * POINTS_PER_SAMPLE
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degree_proof: BLSCommitment
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# The actual data. Should match the commitment and degree proof.
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data: List[BLSPoint, POINTS_PER_SAMPLE * MAX_SAMPLES_PER_BLOB]
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# fee payment fields (EIP 1559 like)
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# TODO: express in MWei instead?
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max_priority_fee_per_sample: Gwei
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max_fee_per_sample: Gwei
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```
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### `ShardBlobBodySummary`
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Summary version of the `ShardBlobBody`, omitting the data payload, while preserving the data-commitments.
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The commitments are not further collapsed to a single hash,
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to avoid an extra network roundtrip between proposer and builder, to include the header on-chain more quickly.
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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.samples_count * POINTS_PER_SAMPLE
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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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# fee payment fields (EIP 1559 like)
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# TODO: express in MWei instead?
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max_priority_fee_per_sample: Gwei
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max_fee_per_sample: Gwei
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```
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### `ShardBlob`
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`ShardBlobBody` wrapped with the header data that is unique to the shard blob proposal.
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```python
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class ShardBlob(Container):
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slot: Slot
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shard: Shard
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# Builder of the data, pays data-fee to proposer
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builder_index: BuilderIndex
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# Proposer of the shard-blob
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proposer_index: ValidatorIndex
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# Blob contents
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body: ShardBlobBody
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```
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### `ShardBlobHeader`
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Header version of `ShardBlob`.
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```python
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class ShardBlobHeader(Container):
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slot: Slot
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shard: Shard
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# Builder of the data, pays data-fee to proposer
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builder_index: BuilderIndex
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# Proposer of the shard-blob
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proposer_index: ValidatorIndex
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# Blob contents, without the full data
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body_summary: ShardBlobBodySummary
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```
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### `SignedShardBlob`
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Full blob data, signed by the shard builder (ensuring fee payment) and shard proposer (ensuring a single proposal).
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```python
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class SignedShardBlob(Container):
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message: ShardBlob
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signature: BLSSignature
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```
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### `SignedShardBlobHeader`
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Header of the blob, the signature is equally applicable to `SignedShardBlob`.
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Shard proposers can accept `SignedShardBlobHeader` as a data-transaction by co-signing the header.
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```python
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class SignedShardBlobHeader(Container):
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message: ShardBlobHeader
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# Signature by builder.
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# Once accepted by proposer, the signatures is the aggregate of both.
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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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# The commitment that is attested
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attested: AttestedDataCommitment
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# Who voted for the header
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votes: Bitlist[MAX_VALIDATORS_PER_COMMITTEE]
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# Sum of effective balances of votes
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weight: Gwei
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# When the header was last updated, as reference for weight accuracy
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update_slot: Slot
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```
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### `ShardBlobReference`
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Reference version of `ShardBlobHeader`, substituting the body for just a hash-tree-root.
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```python
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class ShardBlobReference(Container):
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slot: Slot
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shard: Shard
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# Builder of the data
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builder_index: BuilderIndex
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# Proposer of the shard-blob
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proposer_index: ValidatorIndex
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# Blob hash-tree-root for slashing reference
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body_root: Root
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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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slot: Slot
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shard: Shard
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proposer_index: ValidatorIndex
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builder_index_1: BuilderIndex
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builder_index_2: BuilderIndex
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body_root_1: Root
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body_root_2: Root
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signature_1: BLSSignature
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signature_2: BLSSignature
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```
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### `ShardWork`
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```python
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class ShardWork(Container):
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# Upon confirmation the data is reduced to just the commitment.
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status: Union[ # See Shard Work Status enum
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None, # SHARD_WORK_UNCONFIRMED
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AttestedDataCommitment, # SHARD_WORK_CONFIRMED
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List[PendingShardHeader, MAX_SHARD_HEADERS_PER_SHARD] # SHARD_WORK_PENDING
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]
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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: int) -> int:
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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_sample_price`
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```python
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def compute_updated_sample_price(prev_price: Gwei, samples_length: uint64, active_shards: uint64) -> Gwei:
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adjustment_quotient = active_shards * SLOTS_PER_EPOCH * SAMPLE_PRICE_ADJUSTMENT_COEFFICIENT
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if samples_length > TARGET_SAMPLES_PER_BLOB:
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delta = max(1, prev_price * (samples_length - TARGET_SAMPLES_PER_BLOB) // TARGET_SAMPLES_PER_BLOB // adjustment_quotient)
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return min(prev_price + delta, MAX_SAMPLE_PRICE)
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else:
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delta = max(1, prev_price * (TARGET_SAMPLES_PER_BLOB - samples_length) // TARGET_SAMPLES_PER_BLOB // adjustment_quotient)
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return max(prev_price, MIN_SAMPLE_PRICE + 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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#### `batch_apply_participation_flag`
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```python
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def batch_apply_participation_flag(state: BeaconState, bits: Bitlist[MAX_VALIDATORS_PER_COMMITTEE],
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epoch: Epoch, full_committee: Sequence[ValidatorIndex], flag_index: int):
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if epoch == get_current_epoch(state):
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epoch_participation = state.current_epoch_participation
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else:
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epoch_participation = state.previous_epoch_participation
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for bit, index in zip(bits, full_committee):
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if bit:
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epoch_participation[index] = add_flag(epoch_participation[index], flag_index)
|
|
```
|
|
|
|
### Beacon state accessors
|
|
|
|
#### Updated `get_committee_count_per_slot`
|
|
|
|
```python
|
|
def get_committee_count_per_slot(state: BeaconState, epoch: Epoch) -> uint64:
|
|
"""
|
|
Return the number of committees in each slot for the given ``epoch``.
|
|
"""
|
|
return max(uint64(1), min(
|
|
get_active_shard_count(state, epoch),
|
|
uint64(len(get_active_validator_indices(state, epoch))) // SLOTS_PER_EPOCH // TARGET_COMMITTEE_SIZE,
|
|
))
|
|
```
|
|
|
|
#### `get_active_shard_count`
|
|
|
|
```python
|
|
def get_active_shard_count(state: BeaconState, epoch: Epoch) -> uint64:
|
|
"""
|
|
Return the number of active shards.
|
|
Note that this puts an upper bound on the number of committees per slot.
|
|
"""
|
|
return INITIAL_ACTIVE_SHARDS
|
|
```
|
|
|
|
#### `get_shard_proposer_index`
|
|
|
|
```python
|
|
def get_shard_proposer_index(state: BeaconState, slot: Slot, shard: Shard) -> ValidatorIndex:
|
|
"""
|
|
Return the proposer's index of shard block at ``slot``.
|
|
"""
|
|
epoch = compute_epoch_at_slot(slot)
|
|
seed = hash(get_seed(state, epoch, DOMAIN_SHARD_BLOB) + uint_to_bytes(slot) + uint_to_bytes(shard))
|
|
indices = get_active_validator_indices(state, epoch)
|
|
return compute_proposer_index(state, indices, seed)
|
|
```
|
|
|
|
#### `get_start_shard`
|
|
|
|
```python
|
|
def get_start_shard(state: BeaconState, slot: Slot) -> Shard:
|
|
"""
|
|
Return the start shard at ``slot``.
|
|
"""
|
|
epoch = compute_epoch_at_slot(Slot(slot))
|
|
committee_count = get_committee_count_per_slot(state, epoch)
|
|
active_shard_count = get_active_shard_count(state, epoch)
|
|
return committee_count * slot % active_shard_count
|
|
```
|
|
|
|
#### `compute_shard_from_committee_index`
|
|
|
|
```python
|
|
def compute_shard_from_committee_index(state: BeaconState, slot: Slot, index: CommitteeIndex) -> Shard:
|
|
active_shards = get_active_shard_count(state, compute_epoch_at_slot(slot))
|
|
assert index < active_shards
|
|
return Shard((index + get_start_shard(state, slot)) % active_shards)
|
|
```
|
|
|
|
#### `compute_committee_index_from_shard`
|
|
|
|
```python
|
|
def compute_committee_index_from_shard(state: BeaconState, slot: Slot, shard: Shard) -> CommitteeIndex:
|
|
epoch = compute_epoch_at_slot(slot)
|
|
active_shards = get_active_shard_count(state, epoch)
|
|
index = CommitteeIndex((active_shards + shard - get_start_shard(state, slot)) % active_shards)
|
|
assert index < get_committee_count_per_slot(state, epoch)
|
|
return index
|
|
```
|
|
|
|
|
|
### Block processing
|
|
|
|
```python
|
|
def process_block(state: BeaconState, block: BeaconBlock) -> None:
|
|
process_block_header(state, block)
|
|
# is_execution_enabled is omitted, execution is enabled by default.
|
|
process_execution_payload(state, block.body.execution_payload, EXECUTION_ENGINE)
|
|
process_randao(state, block.body)
|
|
process_eth1_data(state, block.body)
|
|
process_operations(state, block.body) # [Modified in Sharding]
|
|
process_sync_aggregate(state, block.body.sync_aggregate)
|
|
```
|
|
|
|
#### 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)
|
|
|
|
# TODO: to avoid parallel shards racing, and avoid inclusion-order problems,
|
|
# update the fee price per slot, instead of per header.
|
|
# state.shard_sample_price = compute_updated_sample_price(state.shard_sample_price, ?, shard_count)
|
|
```
|
|
|
|
##### Extended Attestation processing
|
|
|
|
```python
|
|
def process_attestation(state: BeaconState, attestation: Attestation) -> None:
|
|
altair.process_attestation(state, attestation)
|
|
process_attested_shard_work(state, attestation)
|
|
```
|
|
|
|
```python
|
|
def process_attested_shard_work(state: BeaconState, attestation: Attestation) -> None:
|
|
attestation_shard = compute_shard_from_committee_index(
|
|
state,
|
|
attestation.data.slot,
|
|
attestation.data.index,
|
|
)
|
|
full_committee = get_beacon_committee(state, attestation.data.slot, attestation.data.index)
|
|
|
|
buffer_index = attestation.data.slot % SHARD_STATE_MEMORY_SLOTS
|
|
committee_work = state.shard_buffer[buffer_index][attestation_shard]
|
|
|
|
# Skip attestation vote accounting if the header is not pending
|
|
if committee_work.status.selector != SHARD_WORK_PENDING:
|
|
# If the data was already confirmed, check if this matches, to apply the flag to the attesters.
|
|
if committee_work.status.selector == SHARD_WORK_CONFIRMED:
|
|
attested: AttestedDataCommitment = committee_work.status.value
|
|
if attested.root == attestation.data.shard_blob_root:
|
|
batch_apply_participation_flag(state, attestation.aggregation_bits,
|
|
attestation.data.target.epoch,
|
|
full_committee, TIMELY_SHARD_FLAG_INDEX)
|
|
return
|
|
|
|
current_headers: Sequence[PendingShardHeader] = committee_work.status.value
|
|
|
|
# Find the corresponding header, abort if it cannot be found
|
|
header_index = len(current_headers)
|
|
for i, header in enumerate(current_headers):
|
|
if attestation.data.shard_blob_root == header.attested.root:
|
|
header_index = i
|
|
break
|
|
|
|
# Attestations for an unknown header do not count towards shard confirmations, but can otherwise be valid.
|
|
if header_index == len(current_headers):
|
|
# Note: Attestations may be re-included if headers are included late.
|
|
return
|
|
|
|
pending_header: PendingShardHeader = current_headers[header_index]
|
|
|
|
# The weight may be outdated if it is not the initial weight, and from a previous epoch
|
|
if pending_header.weight != 0 and compute_epoch_at_slot(pending_header.update_slot) < get_current_epoch(state):
|
|
pending_header.weight = sum(state.validators[index].effective_balance for index, bit
|
|
in zip(full_committee, pending_header.votes) if bit)
|
|
|
|
pending_header.update_slot = state.slot
|
|
|
|
full_committee_balance = Gwei(0)
|
|
# Update votes bitfield in the state, update weights
|
|
for i, bit in enumerate(attestation.aggregation_bits):
|
|
weight = state.validators[full_committee[i]].effective_balance
|
|
full_committee_balance += weight
|
|
if bit:
|
|
if not pending_header.votes[i]:
|
|
pending_header.weight += weight
|
|
pending_header.votes[i] = True
|
|
|
|
# Check if the PendingShardHeader is eligible for expedited confirmation, requiring 2/3 of balance attesting
|
|
if pending_header.weight * 3 >= full_committee_balance * 2:
|
|
# participants of the winning header are remembered with participation flags
|
|
batch_apply_participation_flag(state, pending_header.votes, attestation.data.target.epoch,
|
|
full_committee, TIMELY_SHARD_FLAG_INDEX)
|
|
|
|
if pending_header.attested.commitment == DataCommitment():
|
|
# The committee voted to not confirm anything
|
|
state.shard_buffer[buffer_index][attestation_shard].status.change(
|
|
selector=SHARD_WORK_UNCONFIRMED,
|
|
value=None,
|
|
)
|
|
else:
|
|
state.shard_buffer[buffer_index][attestation_shard].status.change(
|
|
selector=SHARD_WORK_CONFIRMED,
|
|
value=pending_header.attested,
|
|
)
|
|
```
|
|
|
|
##### `process_shard_header`
|
|
|
|
```python
|
|
def process_shard_header(state: BeaconState, signed_header: SignedShardBlobHeader) -> None:
|
|
header: ShardBlobHeader = signed_header.message
|
|
slot = header.slot
|
|
shard = header.shard
|
|
|
|
# Verify the header is not 0, and not from the future.
|
|
assert Slot(0) < slot <= state.slot
|
|
header_epoch = compute_epoch_at_slot(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 valid
|
|
shard_count = get_active_shard_count(state, header_epoch)
|
|
assert shard < shard_count
|
|
# Verify that a committee is able to attest this (slot, shard)
|
|
start_shard = get_start_shard(state, slot)
|
|
committee_index = (shard_count + shard - start_shard) % shard_count
|
|
committees_per_slot = get_committee_count_per_slot(state, header_epoch)
|
|
assert committee_index <= committees_per_slot
|
|
|
|
# Check that this data is still pending
|
|
committee_work = state.shard_buffer[slot % SHARD_STATE_MEMORY_SLOTS][shard]
|
|
assert committee_work.status.selector == SHARD_WORK_PENDING
|
|
|
|
# Check that this header is not yet in the pending list
|
|
current_headers: List[PendingShardHeader, MAX_SHARD_HEADERS_PER_SHARD] = committee_work.status.value
|
|
header_root = hash_tree_root(header)
|
|
assert header_root not in [pending_header.attested.root for pending_header in current_headers]
|
|
|
|
# Verify proposer matches
|
|
assert header.proposer_index == get_shard_proposer_index(state, slot, shard)
|
|
|
|
# Verify builder and proposer aggregate signature
|
|
blob_signing_root = compute_signing_root(header, get_domain(state, DOMAIN_SHARD_BLOB))
|
|
builder_pubkey = state.blob_builders[header.builder_index].pubkey
|
|
proposer_pubkey = state.validators[header.proposer_index].pubkey
|
|
assert bls.FastAggregateVerify([builder_pubkey, proposer_pubkey], blob_signing_root, signed_header.signature)
|
|
|
|
# Verify the length by verifying the degree.
|
|
body_summary = header.body_summary
|
|
points_count = body_summary.commitment.samples_count * POINTS_PER_SAMPLE
|
|
if points_count == 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[-points_count])
|
|
)
|
|
|
|
# Charge EIP 1559 fee, builder pays for opportunity, and is responsible for later availability,
|
|
# or fail to publish at their own expense.
|
|
samples = body_summary.commitment.samples_count
|
|
# TODO: overflows, need bigger int type
|
|
max_fee = body_summary.max_fee_per_sample * samples
|
|
|
|
# Builder must have sufficient balance, even if max_fee is not completely utilized
|
|
assert state.blob_builder_balances[header.builder_index] >= max_fee
|
|
|
|
base_fee = state.shard_sample_price * samples
|
|
# Base fee must be paid
|
|
assert max_fee >= base_fee
|
|
|
|
# Remaining fee goes towards proposer for prioritizing, up to a maximum
|
|
max_priority_fee = body_summary.max_priority_fee_per_sample * samples
|
|
priority_fee = min(max_fee - base_fee, max_priority_fee)
|
|
|
|
# Burn base fee, take priority fee
|
|
# priority_fee <= max_fee - base_fee, thus priority_fee + base_fee <= max_fee, thus sufficient balance.
|
|
state.blob_builder_balances[header.builder_index] -= base_fee + priority_fee
|
|
# Pay out priority fee
|
|
increase_balance(state, header.proposer_index, priority_fee)
|
|
|
|
# Initialize the pending header
|
|
index = compute_committee_index_from_shard(state, slot, shard)
|
|
committee_length = len(get_beacon_committee(state, slot, index))
|
|
initial_votes = Bitlist[MAX_VALIDATORS_PER_COMMITTEE]([0] * committee_length)
|
|
pending_header = PendingShardHeader(
|
|
attested=AttestedDataCommitment(
|
|
commitment=body_summary.commitment,
|
|
root=header_root,
|
|
includer_index=get_beacon_proposer_index(state),
|
|
),
|
|
votes=initial_votes,
|
|
weight=0,
|
|
update_slot=state.slot,
|
|
)
|
|
|
|
# Include it in the pending list
|
|
current_headers.append(pending_header)
|
|
```
|
|
|
|
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).
|
|
|
|
##### `process_shard_proposer_slashing`
|
|
|
|
```python
|
|
def process_shard_proposer_slashing(state: BeaconState, proposer_slashing: ShardProposerSlashing) -> None:
|
|
slot = proposer_slashing.slot
|
|
shard = proposer_slashing.shard
|
|
proposer_index = proposer_slashing.proposer_index
|
|
|
|
reference_1 = ShardBlobReference(slot=slot, shard=shard,
|
|
proposer_index=proposer_index,
|
|
builder_index=proposer_slashing.builder_index_1,
|
|
body_root=proposer_slashing.body_root_1)
|
|
reference_2 = ShardBlobReference(slot=slot, shard=shard,
|
|
proposer_index=proposer_index,
|
|
builder_index=proposer_slashing.builder_index_2,
|
|
body_root=proposer_slashing.body_root_2)
|
|
|
|
# Verify the signed messages are different
|
|
assert reference_1 != reference_2
|
|
|
|
# Verify the proposer is slashable
|
|
proposer = state.validators[proposer_index]
|
|
assert is_slashable_validator(proposer, get_current_epoch(state))
|
|
|
|
# The builders are not slashed, the proposer co-signed with them
|
|
builder_pubkey_1 = state.blob_builders[proposer_slashing.builder_index_1].pubkey
|
|
builder_pubkey_2 = state.blob_builders[proposer_slashing.builder_index_2].pubkey
|
|
domain = get_domain(state, DOMAIN_SHARD_PROPOSER, compute_epoch_at_slot(slot))
|
|
signing_root_1 = compute_signing_root(reference_1, domain)
|
|
signing_root_2 = compute_signing_root(reference_2, domain)
|
|
assert bls.FastAggregateVerify([builder_pubkey_1, proposer.pubkey], signing_root_1, proposer_slashing.signature_1)
|
|
assert bls.FastAggregateVerify([builder_pubkey_2, proposer.pubkey], signing_root_2, proposer_slashing.signature_2)
|
|
|
|
slash_validator(state, proposer_index)
|
|
```
|
|
|
|
### Epoch transition
|
|
|
|
This epoch transition overrides Bellatrix epoch transition:
|
|
|
|
```python
|
|
def process_epoch(state: BeaconState) -> None:
|
|
# Sharding pre-processing
|
|
process_pending_shard_confirmations(state)
|
|
reset_pending_shard_work(state)
|
|
|
|
# Base functionality
|
|
process_justification_and_finalization(state)
|
|
process_inactivity_updates(state)
|
|
process_rewards_and_penalties(state) # Note: modified, see new TIMELY_SHARD_FLAG_INDEX
|
|
process_registry_updates(state)
|
|
process_slashings(state)
|
|
process_eth1_data_reset(state)
|
|
process_effective_balance_updates(state)
|
|
process_slashings_reset(state)
|
|
process_randao_mixes_reset(state)
|
|
process_historical_roots_update(state)
|
|
process_participation_flag_updates(state)
|
|
process_sync_committee_updates(state)
|
|
```
|
|
|
|
#### `process_pending_shard_confirmations`
|
|
|
|
```python
|
|
def process_pending_shard_confirmations(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 = get_previous_epoch(state)
|
|
previous_epoch_start_slot = compute_start_slot_at_epoch(previous_epoch)
|
|
|
|
# Mark stale headers as unconfirmed
|
|
for slot in range(previous_epoch_start_slot, previous_epoch_start_slot + SLOTS_PER_EPOCH):
|
|
buffer_index = slot % SHARD_STATE_MEMORY_SLOTS
|
|
for shard_index in range(len(state.shard_buffer[buffer_index])):
|
|
committee_work = state.shard_buffer[buffer_index][shard_index]
|
|
if committee_work.status.selector == SHARD_WORK_PENDING:
|
|
winning_header = max(committee_work.status.value, key=lambda header: header.weight)
|
|
if winning_header.attested.commitment == DataCommitment():
|
|
committee_work.status.change(selector=SHARD_WORK_UNCONFIRMED, value=None)
|
|
else:
|
|
committee_work.status.change(selector=SHARD_WORK_CONFIRMED, value=winning_header.attested)
|
|
```
|
|
|
|
#### `reset_pending_shard_work`
|
|
|
|
```python
|
|
def reset_pending_shard_work(state: BeaconState) -> None:
|
|
# Add dummy "empty" PendingShardHeader (default vote if no shard header is available)
|
|
next_epoch = get_current_epoch(state) + 1
|
|
next_epoch_start_slot = compute_start_slot_at_epoch(next_epoch)
|
|
committees_per_slot = get_committee_count_per_slot(state, next_epoch)
|
|
active_shards = get_active_shard_count(state, next_epoch)
|
|
|
|
for slot in range(next_epoch_start_slot, next_epoch_start_slot + SLOTS_PER_EPOCH):
|
|
buffer_index = slot % SHARD_STATE_MEMORY_SLOTS
|
|
|
|
# Reset the shard work tracking
|
|
state.shard_buffer[buffer_index] = [ShardWork() for _ in range(active_shards)]
|
|
|
|
start_shard = get_start_shard(state, slot)
|
|
for committee_index in range(committees_per_slot):
|
|
shard = (start_shard + committee_index) % active_shards
|
|
# a committee is available, initialize a pending shard-header list
|
|
committee_length = len(get_beacon_committee(state, slot, CommitteeIndex(committee_index)))
|
|
state.shard_buffer[buffer_index][shard].status.change(
|
|
selector=SHARD_WORK_PENDING,
|
|
value=List[PendingShardHeader, MAX_SHARD_HEADERS_PER_SHARD](
|
|
PendingShardHeader(
|
|
attested=AttestedDataCommitment(),
|
|
votes=Bitlist[MAX_VALIDATORS_PER_COMMITTEE]([0] * committee_length),
|
|
weight=0,
|
|
update_slot=slot,
|
|
)
|
|
)
|
|
)
|
|
# a shard without committee available defaults to SHARD_WORK_UNCONFIRMED.
|
|
```
|