Add initial merge spec

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Mikhail Kalinin 2021-03-11 18:33:36 +06:00
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# Ethereum 2.0 The Merge
**Notice**: This document is a work-in-progress for researchers and implementers.
## Table of contents
<!-- TOC -->
<!-- START doctoc generated TOC please keep comment here to allow auto update -->
<!-- DON'T EDIT THIS SECTION, INSTEAD RE-RUN doctoc TO UPDATE -->
- [Introduction](#introduction)
- [Constants](#constants)
- [Execution](#execution)
- [Containers](#containers)
- [Extended containers](#extended-containers)
- [`BeaconBlockBody`](#beaconblockbody)
- [`BeaconState`](#beaconstate)
- [New containers](#new-containers)
- [`Transaction`](#transaction)
- [`ApplicationPayload`](#applicationpayload)
- [Helper functions](#helper-functions)
- [Misc](#misc)
- [`compute_randao_mix`](#compute_randao_mix)
- [`compute_time_at_slot`](#compute_time_at_slot)
- [Beacon state accessors](#beacon-state-accessors)
- [`get_recent_beacon_block_roots`](#get_recent_beacon_block_roots)
- [`get_evm_beacon_block_roots`](#get_evm_beacon_block_roots)
- [Block processing](#block-processing)
- [Modified `process_eth1_data`](#modified-process_eth1_data)
- [Application payload processing](#application-payload-processing)
- [`BeaconChainData`](#beaconchaindata)
- [`get_application_state`](#get_application_state)
- [`application_state_transition`](#application_state_transition)
- [`process_application_payload`](#process_application_payload)
<!-- END doctoc generated TOC please keep comment here to allow auto update -->
<!-- /TOC -->
## Introduction
This is a patch implementing executable beacon chain proposal.
It enshrines application execution and validity as a first class citizen at the core of the beacon chain.
## Constants
### Execution
| Name | Value |
| - | - |
| `MAX_BYTES_PER_TRANSACTION_PAYLOAD` | `2**20` |
| `MAX_APPLICATION_TRANSACTIONS` | `2**14` |
| `BYTES_PER_LOGS_BLOOM` | `2**8` |
| `EVM_BLOCK_ROOTS_SIZE` | `2**8` |
## Containers
### Extended containers
*Note*: Extended SSZ containers inherit all fields from the parent in the original
order and append any additional fields to the end.
#### `BeaconBlockBody`
*Note*: `BeaconBlockBody` fields remain unchanged other than the addition of `application_payload`.
```python
class BeaconBlockBody(phase0.BeaconBlockBody):
application_payload: ApplicationPayload # User execution payload
```
#### `BeaconState`
*Note*: `BeaconState` fields remain unchanged other than the removal of `eth1_data_votes` and addition of `application_state_root`.
The latter stores the root hash of ethereum application state.
```python
class BeaconState(Container):
# Versioning
genesis_time: uint64
genesis_validators_root: Root
slot: Slot
fork: Fork
# History
latest_block_header: BeaconBlockHeader
block_roots: Vector[Root, SLOTS_PER_HISTORICAL_ROOT]
state_roots: Vector[Root, SLOTS_PER_HISTORICAL_ROOT]
historical_roots: List[Root, HISTORICAL_ROOTS_LIMIT]
# Eth1
eth1_data: Eth1Data
# [removed] eth1_data_votes
eth1_deposit_index: uint64
# [new] Hash of the root of application state
application_state_root: Bytes32
# [new] Hash of recent application block
application_block_hash: Bytes32
# Registry
validators: List[Validator, VALIDATOR_REGISTRY_LIMIT]
balances: List[Gwei, VALIDATOR_REGISTRY_LIMIT]
# Randomness
randao_mixes: Vector[Bytes32, EPOCHS_PER_HISTORICAL_VECTOR]
# Slashings
slashings: Vector[Gwei, EPOCHS_PER_SLASHINGS_VECTOR] # Per-epoch sums of slashed effective balances
# Attestations
previous_epoch_attestations: List[PendingAttestation, MAX_ATTESTATIONS * SLOTS_PER_EPOCH]
current_epoch_attestations: List[PendingAttestation, MAX_ATTESTATIONS * SLOTS_PER_EPOCH]
# Finality
justification_bits: Bitvector[JUSTIFICATION_BITS_LENGTH] # Bit set for every recent justified epoch
previous_justified_checkpoint: Checkpoint # Previous epoch snapshot
current_justified_checkpoint: Checkpoint
finalized_checkpoint: Checkpoint
```
### New containers
#### `Transaction`
Application transaction fields structured as an SSZ object for inclusion in an `ApplicationPayload` contained within a `BeaconBlock`.
```python
class Transaction(Container):
nonce: uint64
gas_price: uint256
gas_limit: uint64
recipient: Bytes20
value: uint256
input: List[Bytes1, MAX_BYTES_PER_TRANSACTION_PAYLOAD]
v: uint256
r: uint256
s: uint256
```
#### `ApplicationPayload`
The application payload included in a `BeaconBlock`.
```python
class ApplicationPayload(Container):
block_hash: Bytes32 # Hash of application block
coinbase: Bytes20
state_root: Bytes32
gas_limit: uint64
gas_used: uint64
receipt_root: Bytes32
logs_bloom: Vector[Bytes1, BYTES_PER_LOGS_BLOOM]
difficulty: uint64 # Temporary field, will be removed later on
transactions: List[Transaction, MAX_APPLICATION_TRANSACTIONS]
```
## Helper functions
### Misc
#### `compute_randao_mix`
```python
def compute_randao_mix(state: BeaconState, randao_reveal: BLSSignature) -> Bytes32:
epoch = get_current_epoch(state)
return xor(get_randao_mix(state, epoch), hash(randao_reveal))
```
#### `compute_time_at_slot`
```python
def compute_time_at_slot(state: BeaconState, slot: Slot) -> uint64:
return uint64(state.genesis_time + slot * SECONDS_PER_SLOT)
```
### Beacon state accessors
#### `get_recent_beacon_block_roots`
```python
def get_recent_beacon_block_roots(state: BeaconState, qty: uint64) -> Sequence[Bytes32]:
return [get_block_root_at_slot(state.slot - i) if GENESIS_SLOT + i < state.slot else Bytes32() for i in reversed(range(1, qty + 1))]
```
#### `get_evm_beacon_block_roots`
```python
def get_evm_beacon_block_roots(state: BeaconState) -> Sequence[Bytes32]:
num_block_roots = min(BLOCK_ROOTS_FOR_EVM_SIZE, SLOTS_PER_HISTORICAL_ROOT)
return get_recent_beacon_block_roots(state, num_block_roots)
```
### 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) # [Modified in The Merge]
process_operations(state, block.body)
process_application_payload(state, block.body) # [New in The Merge]
```
#### Modified `process_eth1_data`
*Note*: The function `process_eth1_data` is modified to update `state.eth1_data` with `eth1_data` of each block.
```python
def process_eth1_data(state: BeaconState, body: BeaconBlockBody) -> None:
state.eth1_data = body.eth1_data
```
#### Application payload processing
##### `BeaconChainData`
*Note*: `BeaconChainData` contains beacon state data that is used by the application state transition function.
```python
class BeaconChainData(Container):
slot: Slot
randao_mix: Bytes32
timestamp: uint64
recent_block_roots: Sequence[Bytes32]
```
##### `get_application_state`
*Note*: `ApplicationState` class is an abstract class representing ethereum application state.
Let `get_application_state(application_state_root: Bytes32) -> ApplicationState` be the function that given the root hash returns a copy of ethereum application state.
The body of the function is implementation dependant.
##### `application_state_transition`
Let `application_state_transition(application_state: ApplicationState, beacon_chain_data: BeaconChainData, application_payload: ApplicationPayload) -> None` be the transition function of ethereum application state.
The body of the function is implementation dependant.
*Note*: `application_state_transition` must throw `AssertionError` if either transition itself or post-transition verifications has failed.
##### `process_application_payload`
```python
def process_application_payload(state: BeaconState, body: BeaconBlockBody) -> None:
"""
Note: This function is designed to be able to be run in parallel with
the other `process_block` sub-functions
"""
# Utilizes `compute_randao_mix` to avoid any assumptions about
# the processing of other `process_block` sub-functions
beacon_chain_data = BeaconChainData(
slot=state.slot,
randao_mix=compute_randao_mix(state, body.randao_reveal),
timestamp=compute_time_at_slot(state.genesis_time, state.slot),
recent_block_roots=get_evm_beacon_block_roots(state)
)
application_state = get_application_state(state.application_state_root)
application_state_transition(application_state, beacon_chain_data, body.application_payload)
state.application_state_root = body.application_payload.state_root
state.application_block_hash = body.application_payload.block_hash
```

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# Ethereum 2.0 The Merge
**Notice**: This document is a work-in-progress for researchers and implementers.
## Table of contents
<!-- TOC -->
<!-- START doctoc generated TOC please keep comment here to allow auto update -->
<!-- DON'T EDIT THIS SECTION, INSTEAD RE-RUN doctoc TO UPDATE -->
- [Introduction](#introduction)
- [Helpers](#helpers)
- [`get_eth1_data`](#get_eth1_data)
- [`is_valid_eth1_data`](#is_valid_eth1_data)
- [Updated fork-choice handlers](#updated-fork-choice-handlers)
- [`on_block`](#on_block)
<!-- END doctoc generated TOC please keep comment here to allow auto update -->
<!-- /TOC -->
## Introduction
This is the modification of the fork choice according to the executable beacon chain proposal.
*Note*: It introduces the following change. `Eth1Data` included in a block must correspond to the application state produced by the parent block. This acts as an additional filter on the block subtree under consideration for the beacon block fork choice.
### Helpers
#### `get_eth1_data`
Let `get_eth1_data(state: BeaconState) -> Eth1Data` be the function that returns the `Eth1Data` obtained from the beacon state.
*Note*: This is mostly a function of the state of the beacon chain deposit contract. It can be read from the application state and/or logs. The `block_hash` value of `Eth1Data` must be set to `state.application_block_hash`.
#### `is_valid_eth1_data`
Used by fork-choice handler, `on_block`
```python
def is_valid_eth1_data(store: Store, block: BeaconBlock) -> boolean:
parent_state = store.block_states[block.parent_root]
expected_eth1_data = get_eth1_data(parent_state)
actual_eth1_data = block.body.eth1_data
is_correct_root = expected_eth1_data.deposit_root == actual_eth1_data.deposit_root
is_correct_count = expected_eth1_data.deposit_count == actual_eth1_data.deposit_count
is_correct_block_hash = expected_eth1_data.block_hash == actual_eth1_data.block_hash
return is_correct_root and is_correct_count and is_correct_block_hash
```
### Updated fork-choice handlers
#### `on_block`
*Note*: The only modification is the addition of the `Eth1Data` validity assumption.
```python
def on_block(store: Store, signed_block: SignedBeaconBlock) -> None:
block = signed_block.message
# Parent block must be known
assert block.parent_root in store.block_states
# Make a copy of the state to avoid mutability issues
pre_state = copy(store.block_states[block.parent_root])
# Blocks cannot be in the future. If they are, their consideration must be delayed until the are in the past.
assert get_current_slot(store) >= block.slot
# Check that block is later than the finalized epoch slot (optimization to reduce calls to get_ancestor)
finalized_slot = compute_start_slot_at_epoch(store.finalized_checkpoint.epoch)
assert block.slot > finalized_slot
# Check block is a descendant of the finalized block at the checkpoint finalized slot
assert get_ancestor(store, block.parent_root, finalized_slot) == store.finalized_checkpoint.root
# [Added] Check that Eth1 data is correct
assert is_valid_eth1_data(store, block)
# Check the block is valid and compute the post-state
state = pre_state.copy()
state_transition(state, signed_block, True)
# Add new block to the store
store.blocks[hash_tree_root(block)] = block
# Add new state for this block to the store
store.block_states[hash_tree_root(block)] = state
# Update justified checkpoint
if state.current_justified_checkpoint.epoch > store.justified_checkpoint.epoch:
if state.current_justified_checkpoint.epoch > store.best_justified_checkpoint.epoch:
store.best_justified_checkpoint = state.current_justified_checkpoint
if should_update_justified_checkpoint(store, state.current_justified_checkpoint):
store.justified_checkpoint = state.current_justified_checkpoint
# Update finalized checkpoint
if state.finalized_checkpoint.epoch > store.finalized_checkpoint.epoch:
store.finalized_checkpoint = state.finalized_checkpoint
# Potentially update justified if different from store
if store.justified_checkpoint != state.current_justified_checkpoint:
# Update justified if new justified is later than store justified
if state.current_justified_checkpoint.epoch > store.justified_checkpoint.epoch:
store.justified_checkpoint = state.current_justified_checkpoint
return
# Update justified if store justified is not in chain with finalized checkpoint
finalized_slot = compute_start_slot_at_epoch(store.finalized_checkpoint.epoch)
ancestor_at_finalized_slot = get_ancestor(store, store.justified_checkpoint.root, finalized_slot)
if ancestor_at_finalized_slot != store.finalized_checkpoint.root:
store.justified_checkpoint = state.current_justified_checkpoint
```

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# Ethereum 2.0 Phase 1 -- Honest Validator
**Notice**: This document is a work-in-progress for researchers and implementers.
## Table of contents
<!-- TOC -->
<!-- START doctoc generated TOC please keep comment here to allow auto update -->
<!-- DON'T EDIT THIS SECTION, INSTEAD RE-RUN doctoc TO UPDATE -->
- [Introduction](#introduction)
- [Prerequisites](#prerequisites)
- [Beacon chain responsibilities](#beacon-chain-responsibilities)
- [Block proposal](#block-proposal)
- [Constructing the `BeaconBlockBody`](#constructing-the-beaconblockbody)
- [Eth1 data](#eth1-data)
- [`get_eth1_data`](#get_eth1_data)
- [Application Payload](#application-payload)
- [`produce_application_payload`](#produce_application_payload)
<!-- END doctoc generated TOC please keep comment here to allow auto update -->
<!-- /TOC -->
## Introduction
This document represents the changes to be made in the code of an "honest validator" to implement executable beacon chain proposal.
## Prerequisites
This document is an extension of the [Phase 0 -- Validator](../phase0/validator.md). All behaviors and definitions defined in the Phase 0 doc carry over unless explicitly noted or overridden.
All terminology, constants, functions, and protocol mechanics defined in the updated Beacon Chain doc of [The Merge](./beacon-chain.md) are requisite for this document and used throughout. Please see related Beacon Chain doc before continuing and use them as a reference throughout.
## Beacon chain responsibilities
All validator responsibilities remain unchanged other than those noted below. Namely, the modification of `Eth1Data` and the addition of `ApplicationPayload`.
### Block proposal
#### Constructing the `BeaconBlockBody`
##### Eth1 data
The `block.body.eth1_data` field is for block proposers to publish recent Eth1 data. This recent data contains deposit root (as calculated by the get_deposit_root() method of the deposit contract) and deposit count after processing of the parent block. The fork choice verifies Eth1 data of a block, then `state.eth1_data` updates immediately allowing new deposits to be processed. Each deposit in `block.body.deposits` must verify against `state.eth1_data.deposit_root`.
###### `get_eth1_data`
Let `get_eth1_data(state: BeaconState) -> Eth1Data` be the function that returns the `Eth1Data` obtained from the beacon state.
*Note*: This is mostly a function of the state of the beacon chain deposit contract. It can be read from the application state and/or logs. The `block_hash` value of `Eth1Data` must be set to `state.application_block_hash`.
Set `block.body.eth1_data = get_eth1_data(state)`.
##### Application Payload
###### `produce_application_payload`
Let `produce_application_payload(parent_hash: Bytes32, beacon_chain_data: BeaconChainData) -> ApplicationPayload` be the function that produces new instance of application payload.
* Let `randao_reveal` be `block.body.randao_reveal` of the block that is being produced
* Set `block.body.application_payload = get_application_payload(state, randao_reveal)` where:
```python
def get_application_payload(state: BeaconState, randao_reveal: BLSSignature) -> ApplicationPayload:
application_parent_hash = state.application_block_hash
beacon_chain_data = BeaconChainData(
slot=state.slot,
randao_mix=compute_randao_mix(state, randao_reveal),
timestamp=compute_time_at_slot(state.genesis_time, state.slot),
recent_block_roots=get_evm_beacon_block_roots(state)
)
return produce_application_payload(application_parent_hash, beacon_chain_data)
```