52 lines
1.9 KiB
Markdown
52 lines
1.9 KiB
Markdown
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# Ethereum 2.0 Phase 1 -- Beacon Chain Fork Choice
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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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- [Fork choice](#fork-choice)
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- [Handlers](#handlers)
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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 is the beacon chain fork choice spec for part of Ethereum 2.0 Phase 1.
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## Fork choice
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Due to the changes in the structure of `IndexedAttestation` in Phase 1, `on_attestation` must be re-specified to handle this. The bulk of `on_attestation` has been moved out into a few helpers to reduce code duplication where possible.
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The rest of the fork choice remains stable.
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### Handlers
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```python
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def on_attestation(store: Store, attestation: Attestation) -> None:
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"""
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Run ``on_attestation`` upon receiving a new ``attestation`` from either within a block or directly on the wire.
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An ``attestation`` that is asserted as invalid may be valid at a later time,
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consider scheduling it for later processing in such case.
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"""
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validate_on_attestation(store, attestation)
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store_target_checkpoint_state(store, attestation.data.target)
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# Get state at the `target` to fully validate attestation
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target_state = store.checkpoint_states[attestation.data.target]
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indexed_attestation = get_indexed_attestation(target_state, attestation)
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assert is_valid_indexed_attestation(target_state, indexed_attestation)
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# Update latest messages for attesting indices
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attesting_indices = [
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index for i, index in enumerate(indexed_attestation.committee)
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if attestation.aggregation_bits[i]
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]
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update_latest_messages(store, attesting_indices, attestation)
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```
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