113 lines
4.6 KiB
Markdown
113 lines
4.6 KiB
Markdown
# Deneb -- Honest Validator
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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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- [Prerequisites](#prerequisites)
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- [Helpers](#helpers)
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- [`get_blobs_and_kzg_commitments`](#get_blobs_and_kzg_commitments)
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- [Beacon chain responsibilities](#beacon-chain-responsibilities)
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- [Block and sidecar proposal](#block-and-sidecar-proposal)
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- [Constructing the `BeaconBlockBody`](#constructing-the-beaconblockbody)
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- [Blob KZG commitments](#blob-kzg-commitments)
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- [Constructing the `SignedBlobSidecar`s](#constructing-the-signedblobsidecars)
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- [Sidecar](#sidecar)
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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 represents the changes to be made in the code of an "honest validator" to implement Deneb.
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## Prerequisites
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This document is an extension of the [Capella -- Honest Validator](../capella/validator.md) guide.
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All behaviors and definitions defined in this document, and documents it extends, carry over unless explicitly noted or overridden.
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All terminology, constants, functions, and protocol mechanics defined in the updated [Beacon Chain doc of Deneb](./beacon-chain.md) are requisite for this document and used throughout.
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Please see related Beacon Chain doc before continuing and use them as a reference throughout.
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## Helpers
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### `get_blobs_and_kzg_commitments`
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The interface to retrieve blobs and corresponding kzg commitments.
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Note: This API is *unstable*. `get_blobs_and_kzg_commitments` and `get_payload` may be unified.
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Implementers may also retrieve blobs individually per transaction.
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```python
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def get_blobs_and_kzg_commitments(payload_id: PayloadId) -> Tuple[Sequence[BLSFieldElement], Sequence[KZGCommitment]]:
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# pylint: disable=unused-argument
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...
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```
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## Beacon chain responsibilities
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All validator responsibilities remain unchanged other than those noted below.
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Namely, the blob handling and the addition of `SignedBeaconBlockAndBlobsSidecar`.
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### Block and sidecar proposal
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#### Constructing the `BeaconBlockBody`
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##### Blob KZG commitments
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1. After retrieving the execution payload from the execution engine as specified in Capella,
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use the `payload_id` to retrieve `blobs` and `blob_kzg_commitments` via `get_blobs_and_kzg_commitments(payload_id)`.
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2. Validate `blobs` and `blob_kzg_commitments`:
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```python
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def validate_blobs_and_kzg_commitments(execution_payload: ExecutionPayload,
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blobs: Sequence[Blob],
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blob_kzg_commitments: Sequence[KZGCommitment]) -> None:
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# Optionally sanity-check that the KZG commitments match the versioned hashes in the transactions
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assert verify_kzg_commitments_against_transactions(execution_payload.transactions, blob_kzg_commitments)
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# Optionally sanity-check that the KZG commitments match the blobs (as produced by the execution engine)
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assert len(blob_kzg_commitments) == len(blobs)
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assert [blob_to_kzg_commitment(blob) == commitment for blob, commitment in zip(blobs, blob_kzg_commitments)]
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```
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3. If valid, set `block.body.blob_kzg_commitments = blob_kzg_commitments`.
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#### Constructing the `SignedBlobSidecar`s
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To construct a `SignedBlobSidecar`, a `signed_blob_sidecar` is defined with the necessary context for block and sidecar proposal.
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##### Sidecar
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Blobs associated with a block are packaged into sidecar objects for distribution to the network.
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Each `sidecar` is obtained from:
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```python
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def get_blob_sidecars(block: BeaconBlock, blobs: Sequence[Blob]) -> Sequence[BlobsSidecar]:
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return [
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BlobsSidecar(
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block_root=hash_tree_root(block),
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index=index,
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slot=block.slot,
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block_parent_root=block.parent_root,
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blob=blob,
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kzg_commitment=block.body.blob_kzg_commitments[idx],
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kzg_proof=compute_kzg_proof(blob),
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)
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for index, blob in enumerate(blobs)
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]
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```
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Each `sidecar` is then published to the global `blob_sidecar_{index}` topics according to its index.
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After publishing the peers on the network may request the sidecar through sync-requests, or a local user may be interested.
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The validator MUST hold on to sidecars for `MIN_EPOCHS_FOR_BLOBS_SIDECARS_REQUESTS` epochs and serve when capable,
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to ensure the data-availability of these blobs throughout the network.
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After `MIN_EPOCHS_FOR_BLOBS_SIDECARS_REQUESTS` nodes MAY prune the sidecars and/or stop serving them.
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