176 lines
6.0 KiB
Markdown
176 lines
6.0 KiB
Markdown
# Ethereum 2.0 The Merge
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**Warning:** This document is currently based on [Phase 0](../phase0/beacon-chain.md) but will be rebased to [Altair](../altair/beacon-chain.md) once the latter is shipped.
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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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- [Transition](#transition)
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- [Execution](#execution)
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- [Containers](#containers)
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- [Extended containers](#extended-containers)
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- [`BeaconBlockBody`](#beaconblockbody)
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- [`BeaconState`](#beaconstate)
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- [New containers](#new-containers)
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- [`ApplicationPayload`](#applicationpayload)
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- [Helper functions](#helper-functions)
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- [Misc](#misc)
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- [`is_transition_completed`](#is_transition_completed)
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- [`is_transition_block`](#is_transition_block)
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- [Block processing](#block-processing)
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- [Application payload processing](#application-payload-processing)
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- [`get_application_state`](#get_application_state)
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- [`application_state_transition`](#application_state_transition)
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- [`process_application_payload`](#process_application_payload)
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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 is a patch implementing the executable beacon chain proposal.
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It enshrines application-layer execution and validity as a first class citizen at the core of the beacon chain.
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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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| `OpaqueTransaction` | `ByteList[MAX_BYTES_PER_OPAQUE_TRANSACTION]` | a byte-list containing a single [typed transaction envelope](https://eips.ethereum.org/EIPS/eip-2718#opaque-byte-array-rather-than-an-rlp-array) structured as `TransactionType \|\| TransactionPayload` |
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## Constants
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### Transition
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| Name | Value |
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| - | - |
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| `TRANSITION_TOTAL_DIFFICULTY` | **TBD** |
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### Execution
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| Name | Value |
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| - | - |
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| `MAX_BYTES_PER_OPAQUE_TRANSACTION` | `uint64(2**20)` (= 1,048,576) |
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| `MAX_APPLICATION_TRANSACTIONS` | `uint64(2**14)` (= 16,384) |
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| `BYTES_PER_LOGS_BLOOM` | `uint64(2**8)` (= 256) |
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## Containers
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### Extended containers
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*Note*: Extended SSZ containers inherit all fields from the parent in the original
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order and append any additional fields to the end.
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#### `BeaconBlockBody`
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*Note*: `BeaconBlockBody` fields remain unchanged other than the addition of `application_payload`.
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```python
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class BeaconBlockBody(phase0.BeaconBlockBody):
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application_payload: ApplicationPayload # [New in Merge] application payload
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```
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#### `BeaconState`
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*Note*: `BeaconState` fields remain unchanged other than addition of `application_state_root` and `application_block_hash`.
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```python
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class BeaconState(phase0.BeaconState):
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# Application-layer
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application_state_root: Bytes32 # [New in Merge]
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application_block_hash: Bytes32 # [New in Merge]
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```
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### New containers
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#### `ApplicationPayload`
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The application payload included in a `BeaconBlockBody`.
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```python
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class ApplicationPayload(Container):
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block_hash: Bytes32 # Hash of application block
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coinbase: Bytes20
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state_root: Bytes32
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gas_limit: uint64
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gas_used: uint64
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receipt_root: Bytes32
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logs_bloom: ByteVector[BYTES_PER_LOGS_BLOOM]
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transactions: List[OpaqueTransaction, MAX_APPLICATION_TRANSACTIONS]
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```
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## Helper functions
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### Misc
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#### `is_transition_completed`
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```python
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def is_transition_completed(state: BeaconState) -> boolean:
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return state.application_block_hash != Bytes32()
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```
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#### `is_transition_block`
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```python
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def is_transition_block(state: BeaconState, block_body: BeaconBlockBody) -> boolean:
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return state.application_block_hash == Bytes32() and block_body.application_payload.block_hash != Bytes32()
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```
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### Block processing
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```python
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def process_block(state: BeaconState, block: BeaconBlock) -> None:
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process_block_header(state, block)
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process_randao(state, block.body)
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process_eth1_data(state, block.body)
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process_operations(state, block.body)
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process_application_payload(state, block.body) # [New in Merge]
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```
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#### Application payload processing
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##### `get_application_state`
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*Note*: `ApplicationState` class is an abstract class representing ethereum application state.
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Let `get_application_state(application_state_root: Bytes32) -> ApplicationState` be the function that given the root hash returns a copy of ethereum application state.
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The body of the function is implementation dependent.
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##### `application_state_transition`
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Let `application_state_transition(application_state: ApplicationState, application_payload: ApplicationPayload) -> None` be the transition function of ethereum application state.
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The body of the function is implementation dependent.
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*Note*: `application_state_transition` must throw `AssertionError` if either the transition itself or one of the post-transition verifications has failed.
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##### `process_application_payload`
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```python
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def process_application_payload(state: BeaconState, body: BeaconBlockBody) -> None:
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"""
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Note: This function is designed to be able to be run in parallel with the other `process_block` sub-functions
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"""
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if is_transition_completed(state):
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application_state = get_application_state(state.application_state_root)
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application_state_transition(application_state, body.application_payload)
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state.application_state_root = body.application_payload.state_root
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state.application_block_hash = body.application_payload.block_hash
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elif is_transition_block(state, body):
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assert body.application_payload == ApplicationPayload(block_hash=body.application_payload.block_hash)
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state.application_block_hash = body.application_payload.block_hash
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else:
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assert body.application_payload == ApplicationPayload()
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```
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