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eth2.0-specs/specs/deneb/beacon-chain.md

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# Deneb -- The Beacon Chain
## 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)
- [Custom types](#custom-types)
- [Constants](#constants)
- [Blob](#blob)
- [Preset](#preset)
- [Execution](#execution)
- [Configuration](#configuration)
- [Execution](#execution-1)
- [Validator cycle](#validator-cycle)
- [Containers](#containers)
- [Extended containers](#extended-containers)
- [`BeaconBlockBody`](#beaconblockbody)
- [`ExecutionPayload`](#executionpayload)
- [`ExecutionPayloadHeader`](#executionpayloadheader)
- [Helper functions](#helper-functions)
- [Misc](#misc)
- [`kzg_commitment_to_versioned_hash`](#kzg_commitment_to_versioned_hash)
- [Beacon state accessors](#beacon-state-accessors)
- [Modified `get_attestation_participation_flag_indices`](#modified-get_attestation_participation_flag_indices)
- [New `get_validator_activation_churn_limit`](#new-get_validator_activation_churn_limit)
- [Beacon chain state transition function](#beacon-chain-state-transition-function)
- [Execution engine](#execution-engine)
- [Request data](#request-data)
- [Modified `NewPayloadRequest`](#modified-newpayloadrequest)
- [Engine APIs](#engine-apis)
- [`is_valid_block_hash`](#is_valid_block_hash)
- [`is_valid_versioned_hashes`](#is_valid_versioned_hashes)
- [Modified `notify_new_payload`](#modified-notify_new_payload)
- [Modified `verify_and_notify_new_payload`](#modified-verify_and_notify_new_payload)
- [Block processing](#block-processing)
- [Modified `process_attestation`](#modified-process_attestation)
- [Execution payload](#execution-payload)
- [Modified `process_execution_payload`](#modified-process_execution_payload)
- [Modified `process_voluntary_exit`](#modified-process_voluntary_exit)
- [Epoch processing](#epoch-processing)
- [Registry updates](#registry-updates)
- [Testing](#testing)
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## Introduction
Deneb is a consensus-layer upgrade containing a number of features. Including:
* [EIP-4788](https://eips.ethereum.org/EIPS/eip-4788): Beacon block root in the EVM
* [EIP-4844](https://eips.ethereum.org/EIPS/eip-4844): Shard Blob Transactions scale data-availability of Ethereum in a simple, forwards-compatible manner
* [EIP-7044](https://eips.ethereum.org/EIPS/eip-7044): Perpetually Valid Signed Voluntary Exits
* [EIP-7045](https://eips.ethereum.org/EIPS/eip-7045): Increase Max Attestation Inclusion Slot
* [EIP-7514](https://eips.ethereum.org/EIPS/eip-7514): Add Max Epoch Churn Limit
## Custom types
| Name | SSZ equivalent | Description |
| - | - | - |
| `VersionedHash` | `Bytes32` | *[New in Deneb:EIP4844]* |
| `BlobIndex` | `uint64` | *[New in Deneb:EIP4844]* |
## Constants
### Blob
| Name | Value |
| - | - |
| `VERSIONED_HASH_VERSION_KZG` | `Bytes1('0x01')` |
## Preset
### Execution
| Name | Value | Description |
| - | - | - |
| `MAX_BLOB_COMMITMENTS_PER_BLOCK` | `uint64(2**12)` (= 4096) | *[New in Deneb:EIP4844]* hardfork independent fixed theoretical limit same as `LIMIT_BLOBS_PER_TX` (see EIP 4844) |
## Configuration
### Execution
| Name | Value | Description |
| - | - | - |
| `MAX_BLOBS_PER_BLOCK` | `uint64(6)` | *[New in Deneb:EIP4844]* maximum number of blobs in a single block limited by `MAX_BLOB_COMMITMENTS_PER_BLOCK` |
*Note*: The blob transactions are packed into the execution payload by the EL/builder with their corresponding blobs being independently transmitted
and are limited by `MAX_BLOB_GAS_PER_BLOCK // GAS_PER_BLOB`. However the CL limit is independently defined by `MAX_BLOBS_PER_BLOCK`.
### Validator cycle
| Name | Value |
| - | - |
| `MAX_PER_EPOCH_ACTIVATION_CHURN_LIMIT` | `uint64(2**3)` (= 8) |
## Containers
### Extended containers
#### `BeaconBlockBody`
Note: `BeaconBlock` and `SignedBeaconBlock` types are updated indirectly.
```python
class BeaconBlockBody(Container):
randao_reveal: BLSSignature
eth1_data: Eth1Data # Eth1 data vote
graffiti: Bytes32 # Arbitrary data
# Operations
proposer_slashings: List[ProposerSlashing, MAX_PROPOSER_SLASHINGS]
attester_slashings: List[AttesterSlashing, MAX_ATTESTER_SLASHINGS]
attestations: List[Attestation, MAX_ATTESTATIONS]
deposits: List[Deposit, MAX_DEPOSITS]
voluntary_exits: List[SignedVoluntaryExit, MAX_VOLUNTARY_EXITS]
sync_aggregate: SyncAggregate
# Execution
execution_payload: ExecutionPayload # [Modified in Deneb:EIP4844]
bls_to_execution_changes: List[SignedBLSToExecutionChange, MAX_BLS_TO_EXECUTION_CHANGES]
blob_kzg_commitments: List[KZGCommitment, MAX_BLOB_COMMITMENTS_PER_BLOCK] # [New in Deneb:EIP4844]
```
#### `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
# Extra payload fields
block_hash: Hash32 # Hash of execution block
transactions: List[Transaction, MAX_TRANSACTIONS_PER_PAYLOAD]
withdrawals: List[Withdrawal, MAX_WITHDRAWALS_PER_PAYLOAD]
blob_gas_used: uint64 # [New in Deneb:EIP4844]
excess_blob_gas: uint64 # [New in Deneb:EIP4844]
```
#### `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
# Extra payload fields
block_hash: Hash32 # Hash of execution block
transactions_root: Root
withdrawals_root: Root
blob_gas_used: uint64 # [New in Deneb:EIP4844]
excess_blob_gas: uint64 # [New in Deneb:EIP4844]
```
## Helper functions
### Misc
#### `kzg_commitment_to_versioned_hash`
```python
def kzg_commitment_to_versioned_hash(kzg_commitment: KZGCommitment) -> VersionedHash:
return VERSIONED_HASH_VERSION_KZG + hash(kzg_commitment)[1:]
```
### Beacon state accessors
#### Modified `get_attestation_participation_flag_indices`
*Note:* The function `get_attestation_participation_flag_indices` is modified to set the `TIMELY_TARGET_FLAG` for any correct target attestation, regardless of `inclusion_delay` as a baseline reward for any speed of inclusion of an attestation that contributes to justification of the contained chain for EIP-7045.
```python
def get_attestation_participation_flag_indices(state: BeaconState,
data: AttestationData,
inclusion_delay: uint64) -> Sequence[int]:
"""
Return the flag indices that are satisfied by an attestation.
"""
if data.target.epoch == get_current_epoch(state):
justified_checkpoint = state.current_justified_checkpoint
else:
justified_checkpoint = state.previous_justified_checkpoint
# Matching roots
is_matching_source = data.source == justified_checkpoint
is_matching_target = is_matching_source and data.target.root == get_block_root(state, data.target.epoch)
is_matching_head = is_matching_target and data.beacon_block_root == get_block_root_at_slot(state, data.slot)
assert is_matching_source
participation_flag_indices = []
if is_matching_source and inclusion_delay <= integer_squareroot(SLOTS_PER_EPOCH):
participation_flag_indices.append(TIMELY_SOURCE_FLAG_INDEX)
if is_matching_target: # [Modified in Deneb:EIP7045]
participation_flag_indices.append(TIMELY_TARGET_FLAG_INDEX)
if is_matching_head and inclusion_delay == MIN_ATTESTATION_INCLUSION_DELAY:
participation_flag_indices.append(TIMELY_HEAD_FLAG_INDEX)
return participation_flag_indices
```
#### New `get_validator_activation_churn_limit`
```python
def get_validator_activation_churn_limit(state: BeaconState) -> uint64:
"""
Return the validator activation churn limit for the current epoch.
"""
return min(MAX_PER_EPOCH_ACTIVATION_CHURN_LIMIT, get_validator_churn_limit(state))
```
## Beacon chain state transition function
### Execution engine
#### Request data
##### Modified `NewPayloadRequest`
```python
@dataclass
class NewPayloadRequest(object):
execution_payload: ExecutionPayload
versioned_hashes: Sequence[VersionedHash]
parent_beacon_block_root: Root
```
#### Engine APIs
##### `is_valid_block_hash`
*Note*: The function `is_valid_block_hash` is modified to include the additional `parent_beacon_block_root` parameter for EIP-4788.
```python
def is_valid_block_hash(self: ExecutionEngine,
execution_payload: ExecutionPayload,
parent_beacon_block_root: Root) -> bool:
"""
Return ``True`` if and only if ``execution_payload.block_hash`` is computed correctly.
"""
...
```
##### `is_valid_versioned_hashes`
```python
def is_valid_versioned_hashes(self: ExecutionEngine, new_payload_request: NewPayloadRequest) -> bool:
"""
Return ``True`` if and only if the version hashes computed by the blob transactions of
``new_payload_request.execution_payload`` matches ``new_payload_request.versioned_hashes``.
"""
...
```
##### Modified `notify_new_payload`
*Note*: The function `notify_new_payload` is modified to include the additional `parent_beacon_block_root` parameter for EIP-4788.
```python
def notify_new_payload(self: ExecutionEngine,
execution_payload: ExecutionPayload,
parent_beacon_block_root: Root) -> bool:
"""
Return ``True`` if and only if ``execution_payload`` is valid with respect to ``self.execution_state``.
"""
...
```
##### Modified `verify_and_notify_new_payload`
```python
def verify_and_notify_new_payload(self: ExecutionEngine,
new_payload_request: NewPayloadRequest) -> bool:
"""
Return ``True`` if and only if ``new_payload_request`` is valid with respect to ``self.execution_state``.
"""
execution_payload = new_payload_request.execution_payload
parent_beacon_block_root = new_payload_request.parent_beacon_block_root
# [Modified in Deneb:EIP4788]
if not self.is_valid_block_hash(execution_payload, parent_beacon_block_root):
return False
# [New in Deneb:EIP4844]
if not self.is_valid_versioned_hashes(new_payload_request):
return False
# [Modified in Deneb:EIP4788]
if not self.notify_new_payload(execution_payload, parent_beacon_block_root):
return False
return True
```
### Block processing
#### Modified `process_attestation`
*Note*: The function `process_attestation` is modified to expand valid slots for inclusion to those in both `target.epoch` epoch and `target.epoch + 1` epoch for EIP-7045. Additionally, it utilizes an updated version of `get_attestation_participation_flag_indices` to ensure rewards are available for the extended attestation inclusion range for EIP-7045.
```python
def process_attestation(state: BeaconState, attestation: Attestation) -> None:
data = attestation.data
assert data.target.epoch in (get_previous_epoch(state), get_current_epoch(state))
assert data.target.epoch == compute_epoch_at_slot(data.slot)
assert data.slot + MIN_ATTESTATION_INCLUSION_DELAY <= state.slot # [Modified in Deneb:EIP7045]
assert data.index < get_committee_count_per_slot(state, data.target.epoch)
committee = get_beacon_committee(state, data.slot, data.index)
assert len(attestation.aggregation_bits) == len(committee)
# Participation flag indices
participation_flag_indices = get_attestation_participation_flag_indices(state, data, state.slot - data.slot)
# Verify signature
assert is_valid_indexed_attestation(state, get_indexed_attestation(state, attestation))
# Update epoch participation flags
if data.target.epoch == get_current_epoch(state):
epoch_participation = state.current_epoch_participation
else:
epoch_participation = state.previous_epoch_participation
proposer_reward_numerator = 0
for index in get_attesting_indices(state, attestation):
for flag_index, weight in enumerate(PARTICIPATION_FLAG_WEIGHTS):
if flag_index in participation_flag_indices and not has_flag(epoch_participation[index], flag_index):
epoch_participation[index] = add_flag(epoch_participation[index], flag_index)
proposer_reward_numerator += get_base_reward(state, index) * weight
# Reward proposer
proposer_reward_denominator = (WEIGHT_DENOMINATOR - PROPOSER_WEIGHT) * WEIGHT_DENOMINATOR // PROPOSER_WEIGHT
proposer_reward = Gwei(proposer_reward_numerator // proposer_reward_denominator)
increase_balance(state, get_beacon_proposer_index(state), proposer_reward)
```
#### Execution payload
##### Modified `process_execution_payload`
*Note*: The function `process_execution_payload` is modified to pass `versioned_hashes` into `execution_engine.verify_and_notify_new_payload` and to assign the new fields in `ExecutionPayloadHeader` for EIP-4844. It is also modified to pass in the parent beacon block root to support EIP-4788.
```python
def process_execution_payload(state: BeaconState, body: BeaconBlockBody, execution_engine: ExecutionEngine) -> None:
payload = body.execution_payload
# Verify consistency of the parent hash with respect to the previous execution payload header
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)
# [New in Deneb:EIP4844] Verify commitments are under limit
assert len(body.blob_kzg_commitments) <= MAX_BLOBS_PER_BLOCK
# Verify the execution payload is valid
# [Modified in Deneb:EIP4844] Pass `versioned_hashes` to Execution Engine
# [Modified in Deneb:EIP4788] Pass `parent_beacon_block_root` to Execution Engine
versioned_hashes = [kzg_commitment_to_versioned_hash(commitment) for commitment in body.blob_kzg_commitments]
assert execution_engine.verify_and_notify_new_payload(
NewPayloadRequest(
execution_payload=payload,
versioned_hashes=versioned_hashes,
parent_beacon_block_root=state.latest_block_header.parent_root,
)
)
# 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),
withdrawals_root=hash_tree_root(payload.withdrawals),
blob_gas_used=payload.blob_gas_used, # [New in Deneb:EIP4844]
excess_blob_gas=payload.excess_blob_gas, # [New in Deneb:EIP4844]
)
```
#### Modified `process_voluntary_exit`
*Note*: The function `process_voluntary_exit` is modified to use the a fixed fork version -- `CAPELLA_FORK_VERSION` -- for EIP-7044.
```python
def process_voluntary_exit(state: BeaconState, signed_voluntary_exit: SignedVoluntaryExit) -> None:
voluntary_exit = signed_voluntary_exit.message
validator = state.validators[voluntary_exit.validator_index]
# Verify the validator is active
assert is_active_validator(validator, get_current_epoch(state))
# Verify exit has not been initiated
assert validator.exit_epoch == FAR_FUTURE_EPOCH
# Exits must specify an epoch when they become valid; they are not valid before then
assert get_current_epoch(state) >= voluntary_exit.epoch
# Verify the validator has been active long enough
assert get_current_epoch(state) >= validator.activation_epoch + SHARD_COMMITTEE_PERIOD
# Verify signature
# [Modified in Deneb:EIP7044]
domain = compute_domain(DOMAIN_VOLUNTARY_EXIT, CAPELLA_FORK_VERSION, state.genesis_validators_root)
signing_root = compute_signing_root(voluntary_exit, domain)
assert bls.Verify(validator.pubkey, signing_root, signed_voluntary_exit.signature)
# Initiate exit
initiate_validator_exit(state, voluntary_exit.validator_index)
```
### Epoch processing
#### Registry updates
*Note*: The function `process_registry_updates` is modified to utilize `get_validator_activation_churn_limit()` to rate limit the activation queue for EIP-7514.
```python
def process_registry_updates(state: BeaconState) -> None:
# Process activation eligibility and ejections
for index, validator in enumerate(state.validators):
if is_eligible_for_activation_queue(validator):
validator.activation_eligibility_epoch = get_current_epoch(state) + 1
if (
is_active_validator(validator, get_current_epoch(state))
and validator.effective_balance <= EJECTION_BALANCE
):
initiate_validator_exit(state, ValidatorIndex(index))
# Queue validators eligible for activation and not yet dequeued for activation
activation_queue = sorted([
index for index, validator in enumerate(state.validators)
if is_eligible_for_activation(state, validator)
# Order by the sequence of activation_eligibility_epoch setting and then index
], key=lambda index: (state.validators[index].activation_eligibility_epoch, index))
# Dequeued validators for activation up to activation churn limit
# [Modified in Deneb:EIP7514]
for index in activation_queue[:get_validator_activation_churn_limit(state)]:
validator = state.validators[index]
validator.activation_epoch = compute_activation_exit_epoch(get_current_epoch(state))
```
## Testing
*Note*: The function `initialize_beacon_state_from_eth1` is modified for pure Deneb testing only.
The `BeaconState` initialization is unchanged, except for the use of the updated `deneb.BeaconBlockBody` type
when initializing the first body-root.
```python
def initialize_beacon_state_from_eth1(eth1_block_hash: Hash32,
eth1_timestamp: uint64,
deposits: Sequence[Deposit],
execution_payload_header: ExecutionPayloadHeader=ExecutionPayloadHeader()
) -> BeaconState:
fork = Fork(
previous_version=DENEB_FORK_VERSION, # [Modified in Deneb] for testing only
current_version=DENEB_FORK_VERSION, # [Modified in Deneb]
epoch=GENESIS_EPOCH,
)
state = BeaconState(
genesis_time=eth1_timestamp + GENESIS_DELAY,
fork=fork,
eth1_data=Eth1Data(block_hash=eth1_block_hash, deposit_count=uint64(len(deposits))),
latest_block_header=BeaconBlockHeader(body_root=hash_tree_root(BeaconBlockBody())),
randao_mixes=[eth1_block_hash] * EPOCHS_PER_HISTORICAL_VECTOR, # Seed RANDAO with Eth1 entropy
)
# Process deposits
leaves = list(map(lambda deposit: deposit.data, deposits))
for index, deposit in enumerate(deposits):
deposit_data_list = List[DepositData, 2**DEPOSIT_CONTRACT_TREE_DEPTH](*leaves[:index + 1])
state.eth1_data.deposit_root = hash_tree_root(deposit_data_list)
process_deposit(state, deposit)
# Process activations
for index, validator in enumerate(state.validators):
balance = state.balances[index]
validator.effective_balance = min(balance - balance % EFFECTIVE_BALANCE_INCREMENT, MAX_EFFECTIVE_BALANCE)
if validator.effective_balance == MAX_EFFECTIVE_BALANCE:
validator.activation_eligibility_epoch = GENESIS_EPOCH
validator.activation_epoch = GENESIS_EPOCH
# Set genesis validators root for domain separation and chain versioning
state.genesis_validators_root = hash_tree_root(state.validators)
# Fill in sync committees
# Note: A duplicate committee is assigned for the current and next committee at genesis
state.current_sync_committee = get_next_sync_committee(state)
state.next_sync_committee = get_next_sync_committee(state)
# Initialize the execution payload header
# If empty, will initialize a chain that has not yet gone through the Merge transition
state.latest_execution_payload_header = execution_payload_header
return state
```
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