Spec draft for the verge

Co-Authored-By: Dankrad Feist <mail@dankradfeist.de>
This commit is contained in:
Guillaume Ballet 2023-01-26 09:14:08 +01:00
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# The Verge -- The Beacon Chain
## Table of contents
<!-- TOC -->
<!-- START doctoc generated TOC please keep comment here to allow auto update -->
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- [Introduction](#introduction)
- [Custom types](#custom-types)
- [Preset](#preset)
- [Execution](#execution)
- [Containers](#containers)
- [Extended containers](#extended-containers)
- [`ExecutionPayload`](#executionpayload)
- [`ExecutionPayloadHeader`](#executionpayloadheader)
- [New containers](#new-containers)
- [`SuffixStateDiff`](#suffixstatediff)
- [`StemStateDiff`](#stemstatediff)
- [`IPAProof`](#ipaproof)
- [`VerkleProof`](#verkleproof)
- [`ExecutionWitness`](#executionwitness)
- [Beacon chain state transition function](#beacon-chain-state-transition-function)
- [Execution engine](#execution-engine)
- [`notify_new_payload`](#notify_new_payload)
- [Block processing](#block-processing)
- [Execution payload](#execution-payload)
- [`process_execution_payload`](#process_execution_payload)
- [Testing](#testing)
<!-- END doctoc generated TOC please keep comment here to allow auto update -->
<!-- /TOC -->
## Introduction
This upgrade adds transaction execution to the beacon chain as part of the Verge upgrade.
## Custom types
| Name | SSZ equivalent | Description |
| - | - | - |
| `StateDiff` | `List[StemStateDiff, MAX_STEMS]` | Only valid if list is sorted by stems |
| `BandersnatchGroupElement` | `Bytes32` | |
| `BandersnatchFieldElement` | `Bytes32` | |
| `Stem` | `Bytes31` | |
## Preset
### Execution
| Name | Value |
| - | - |
| `MAX_STEMS` | `2**16` |
| `MAX_COMMITMENTS_PER_STEM` | `33` |
| `VERKLE_WIDTH` | `256` |
| `IPA_PROOF_DEPTH` | `8` |
## Containers
### Extended containers
#### `ExecutionPayload`
```python
class ExecutionPayload(Container):
# Execution block header fields
parent_hash: Hash32
fee_recipient: ExecutionAddress # 'beneficiary' in the yellow paper
state_root: Bytes32
receipts_root: Bytes32
logs_bloom: ByteVector[BYTES_PER_LOGS_BLOOM]
prev_randao: Bytes32 # 'difficulty' in the yellow paper
block_number: uint64 # 'number' in the yellow paper
gas_limit: uint64
gas_used: uint64
timestamp: uint64
extra_data: ByteList[MAX_EXTRA_DATA_BYTES]
base_fee_per_gas: uint256
block_hash: Hash32 # Hash of execution block
# Extra payload field
execution_witness: ExecutionWitness
transactions: List[Transaction, MAX_TRANSACTIONS_PER_PAYLOAD]
```
#### `ExecutionPayloadHeader`
```python
class ExecutionPayloadHeader(Container):
# Execution block header fields
parent_hash: Hash32
fee_recipient: ExecutionAddress
state_root: Bytes32
receipts_root: Bytes32
logs_bloom: ByteVector[BYTES_PER_LOGS_BLOOM]
prev_randao: Bytes32
block_number: uint64
gas_limit: uint64
gas_used: uint64
timestamp: uint64
extra_data: ByteList[MAX_EXTRA_DATA_BYTES]
base_fee_per_gas: uint256
block_hash: Hash32 # Hash of execution block
transactions_root: Root
# Extra payload fields
execution_witness: ExecutionWitness
```
### New containers
#### `SuffixStateDiff`
```python
class SuffixStateDiff(Container):
suffix: Byte
# Null means not currently present
current_value: Union[Null, Bytes32]
# Null means value not updated
new_value: Union[Null, Bytes32]
```
*Note*: on the Kaustinen testnet, `new_value` is ommitted from the container.
#### `StemStateDiff`
```python
class StemStateDiff(Container):
stem: Stem
# Valid only if list is sorted by suffixes
suffix_diffs: List[SuffixStateDiff, VERKLE_WIDTH]
```
```python
# Valid only if list is sorted by stems
StateDiff = List[StemStateDiff, MAX_STEMS]
```
#### `IPAProof`
```python
class IpaProof(Container):
C_L = Vector[BandersnatchGroupElement, IPA_PROOF_DEPTH]
C_R = Vector[BandersnatchGroupElement, IPA_PROOF_DEPTH]
final_evaluation = BandersnatchFieldElement
```
#### `VerkleProof`
```python
class VerkleProof(Container):
other_stems: List[Bytes32, MAX_STEMS]
depth_extension_present: List[uint8, MAX_STEMS]
commitments_by_path: List[BandersnatchGroupElement, MAX_STEMS * MAX_COMMITMENTS_PER_STEM]
D: BandersnatchGroupElement
ipa_proof: IpaProof
```
#### `ExecutionWitness`
```python
class ExecutionWitness(container):
state_diff: StateDiff
verkle_proof: VerkleProof
```
## Beacon chain state transition function
### Block processing
#### Execution payload
##### `process_execution_payload`
```python
def process_execution_payload(state: BeaconState, payload: ExecutionPayload, execution_engine: ExecutionEngine) -> None:
# Verify consistency of the parent hash with respect to the previous execution payload header
if is_merge_transition_complete(state):
assert payload.parent_hash == state.latest_execution_payload_header.block_hash
# Verify prev_randao
assert payload.prev_randao == get_randao_mix(state, get_current_epoch(state))
# Verify timestamp
assert payload.timestamp == compute_timestamp_at_slot(state, state.slot)
# Verify the execution payload is valid
assert execution_engine.notify_new_payload(payload)
# Cache execution payload header
state.latest_execution_payload_header = ExecutionPayloadHeader(
parent_hash=payload.parent_hash,
fee_recipient=payload.fee_recipient,
state_root=payload.state_root,
receipts_root=payload.receipts_root,
logs_bloom=payload.logs_bloom,
prev_randao=payload.prev_randao,
block_number=payload.block_number,
gas_limit=payload.gas_limit,
gas_used=payload.gas_used,
timestamp=payload.timestamp,
extra_data=payload.extra_data,
base_fee_per_gas=payload.base_fee_per_gas,
block_hash=payload.block_hash,
transactions_root=hash_tree_root(payload.transactions),
execution_witness=payload.execution_witness,
)
```
## Testing
TBD

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# The Verge -- Fork Logic
## Table of contents
<!-- 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)
- [Configuration](#configuration)
- [Helper functions](#helper-functions)
- [Misc](#misc)
- [Modified `compute_fork_version`](#modified-compute_fork_version)
- [Fork to the Verge](#fork-to-capella)
- [Fork trigger](#fork-trigger)
- [Upgrading the state](#upgrading-the-state)
<!-- END doctoc generated TOC please keep comment here to allow auto update -->
## Introduction
This document describes the process of the Verge upgrade.
## Configuration
Warning: this configuration is not definitive.
| Name | Value |
| - | - |
| `VERGE_FORK_VERSION` | `Version('0x05000000')` |
| `VERGE_FORK_EPOCH` | `Epoch(18446744073709551615)` **TBD** |
## Helper functions
### Misc
#### Modified `compute_fork_version`
```python
def compute_fork_version(epoch: Epoch) -> Version:
"""
Return the fork version at the given ``epoch``.
"""
if epoch >= VERGE_FORK_EPOCH:
return VERGE_FORK_VERSION
if epoch >= CAPELLA_FORK_EPOCH:
return CAPELLA_FORK_VERSION
if epoch >= BELLATRIX_FORK_EPOCH:
return BELLATRIX_FORK_VERSION
if epoch >= ALTAIR_FORK_EPOCH:
return ALTAIR_FORK_VERSION
return GENESIS_FORK_VERSION
```
## Fork to the Verge
### Fork trigger
The fork is triggered at epoch `VERGE_FORK_EPOCH`.
Note that for the pure verge networks, we don't apply `upgrade_to_verge` since it starts with the Verge version logic.
### Upgrading the state
If `state.slot % SLOTS_PER_EPOCH == 0` and `compute_epoch_at_slot(state.slot) == VERGE_FORK_EPOCH`,
an irregular state change is made to upgrade to the Verge.
The upgrade occurs after the completion of the inner loop of `process_slots` that sets `state.slot` equal to `VERGE_FORK_EPOCH * SLOTS_PER_EPOCH`.
Care must be taken when transitioning through the fork boundary as implementations will need a modified [state transition function](../phase0/beacon-chain.md#beacon-chain-state-transition-function) that deviates from the Phase 0 document.
In particular, the outer `state_transition` function defined in the Phase 0 document will not expose the precise fork slot to execute the upgrade in the presence of skipped slots at the fork boundary. Instead, the logic must be within `process_slots`.
```python
def upgrade_to_verge(pre: capella.BeaconState) -> BeaconState:
epoch = capella.get_current_epoch(pre)
latest_execution_payload_header = ExecutionPayloadHeader(
parent_hash=pre.latest_execution_payload_header.parent_hash,
fee_recipient=pre.latest_execution_payload_header.fee_recipient,
state_root=pre.latest_execution_payload_header.state_root,
receipts_root=pre.latest_execution_payload_header.receipts_root,
logs_bloom=pre.latest_execution_payload_header.logs_bloom,
prev_randao=pre.latest_execution_payload_header.prev_randao,
block_number=pre.latest_execution_payload_header.block_number,
gas_limit=pre.latest_execution_payload_header.gas_limit,
gas_used=pre.latest_execution_payload_header.gas_used,
timestamp=pre.latest_execution_payload_header.timestamp,
extra_data=pre.latest_execution_payload_header.extra_data,
base_fee_per_gas=pre.latest_execution_payload_header.base_fee_per_gas,
block_hash=pre.latest_execution_payload_header.block_hash,
transactions_root=pre.latest_execution_payload_header.transactions_root,
withdrawals_root=pre.latest_execution_payload_header.withdrawals_root,
execution_witness=ExecutionWitness([], []) # New in the Verge
)
post = BeaconState(
# Versioning
genesis_time=pre.genesis_time,
genesis_validators_root=pre.genesis_validators_root,
slot=pre.slot,
fork=Fork(
previous_version=pre.fork.current_version,
current_version=VERGE_FORK_VERSION,
epoch=epoch,
),
# History
latest_block_header=pre.latest_block_header,
block_roots=pre.block_roots,
state_roots=pre.state_roots,
historical_roots=pre.historical_roots,
# Eth1
eth1_data=pre.eth1_data,
eth1_data_votes=pre.eth1_data_votes,
eth1_deposit_index=pre.eth1_deposit_index,
# Registry
validators=pre.validators,
balances=pre.balances,
# Randomness
randao_mixes=pre.randao_mixes,
# Slashings
slashings=pre.slashings,
# Participation
previous_epoch_participation=pre.previous_epoch_participation,
current_epoch_participation=pre.current_epoch_participation,
# Finality
justification_bits=pre.justification_bits,
previous_justified_checkpoint=pre.previous_justified_checkpoint,
current_justified_checkpoint=pre.current_justified_checkpoint,
finalized_checkpoint=pre.finalized_checkpoint,
# Inactivity
inactivity_scores=pre.inactivity_scores,
# Sync
current_sync_committee=pre.current_sync_committee,
next_sync_committee=pre.next_sync_committee,
# Execution-layer
latest_execution_payload_header=latest_execution_payload_header,
# Withdrawals
next_withdrawal_index=pre.next_withdrawal_index,
next_withdrawal_validator_index=pre.next_withdrawal_validator_index,
# Deep history valid from Capella onwards
# FIXME most likely wrong
historical_summaries=List[HistoricalSummary, HISTORICAL_ROOTS_LIMIT]([]), # [New in Capella]
)
return post
```