700 lines
29 KiB
Markdown
700 lines
29 KiB
Markdown
# Ethereum 2.0 Altair
|
|
|
|
## 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)
|
|
- [Participation flag indices](#participation-flag-indices)
|
|
- [Participation flag fractions](#participation-flag-fractions)
|
|
- [Misc](#misc)
|
|
- [Configuration](#configuration)
|
|
- [Updated penalty values](#updated-penalty-values)
|
|
- [Misc](#misc-1)
|
|
- [Time parameters](#time-parameters)
|
|
- [Domain types](#domain-types)
|
|
- [Containers](#containers)
|
|
- [Modified containers](#modified-containers)
|
|
- [`BeaconBlockBody`](#beaconblockbody)
|
|
- [`BeaconState`](#beaconstate)
|
|
- [New containers](#new-containers)
|
|
- [`SyncCommittee`](#synccommittee)
|
|
- [Helper functions](#helper-functions)
|
|
- [`Predicates`](#predicates)
|
|
- [`eth2_fast_aggregate_verify`](#eth2_fast_aggregate_verify)
|
|
- [Misc](#misc-2)
|
|
- [`get_flag_indices_and_numerators`](#get_flag_indices_and_numerators)
|
|
- [`add_flag`](#add_flag)
|
|
- [`has_flag`](#has_flag)
|
|
- [Beacon state accessors](#beacon-state-accessors)
|
|
- [`get_sync_committee_indices`](#get_sync_committee_indices)
|
|
- [`get_sync_committee`](#get_sync_committee)
|
|
- [`get_base_reward`](#get_base_reward)
|
|
- [`get_unslashed_participating_indices`](#get_unslashed_participating_indices)
|
|
- [`get_flag_deltas`](#get_flag_deltas)
|
|
- [New `get_inactivity_penalty_deltas`](#new-get_inactivity_penalty_deltas)
|
|
- [Beacon state mutators](#beacon-state-mutators)
|
|
- [New `slash_validator`](#new-slash_validator)
|
|
- [Block processing](#block-processing)
|
|
- [Modified `process_attestation`](#modified-process_attestation)
|
|
- [Modified `process_deposit`](#modified-process_deposit)
|
|
- [Sync committee processing](#sync-committee-processing)
|
|
- [Epoch processing](#epoch-processing)
|
|
- [Justification and finalization](#justification-and-finalization)
|
|
- [Leak scores](#leak-scores)
|
|
- [Rewards and penalties](#rewards-and-penalties)
|
|
- [Slashings](#slashings)
|
|
- [Participation flags updates](#participation-flags-updates)
|
|
- [Sync committee updates](#sync-committee-updates)
|
|
|
|
<!-- END doctoc generated TOC please keep comment here to allow auto update -->
|
|
<!-- /TOC -->
|
|
|
|
## Introduction
|
|
|
|
Altair is a patch implementing the first hard fork to the beacon chain.
|
|
It has four main features:
|
|
|
|
* Light client support via sync committees
|
|
* Incentive accounting reforms, reducing spec complexity
|
|
and [TODO] reducing the cost of processing chains that have very little or zero participation for a long span of epochs
|
|
* Update penalty configuration values, moving them toward their planned maximally punitive configuration
|
|
* Fork choice rule changes to address weaknesses recently discovered in the existing fork choice
|
|
|
|
## Custom types
|
|
|
|
| Name | SSZ equivalent | Description |
|
|
| - | - | - |
|
|
| `ParticipationFlags` | `uint8` | A succinct representation of 8 boolean participation flags |
|
|
|
|
## Constants
|
|
|
|
### Participation flag indices
|
|
|
|
| Name | Value |
|
|
| - | - |
|
|
| `TIMELY_HEAD_FLAG_INDEX` | `0` |
|
|
| `TIMELY_SOURCE_FLAG_INDEX` | `1` |
|
|
| `TIMELY_TARGET_FLAG_INDEX` | `2` |
|
|
|
|
### Participation flag fractions
|
|
|
|
| Name | Value |
|
|
| - | - |
|
|
| `TIMELY_HEAD_FLAG_NUMERATOR` | `12` |
|
|
| `TIMELY_SOURCE_FLAG_NUMERATOR` | `12` |
|
|
| `TIMELY_TARGET_FLAG_NUMERATOR` | `32` |
|
|
| `FLAG_DENOMINATOR` | `64` |
|
|
|
|
**Note**: The participatition flag fractions add up to 7/8.
|
|
The remaining 1/8 is for proposer incentives and other future micro-incentives.
|
|
|
|
### Misc
|
|
|
|
| Name | Value |
|
|
| - | - |
|
|
| `G2_POINT_AT_INFINITY` | `BLSSignature(b'\xc0' + b'\x00' * 95)` |
|
|
|
|
## Configuration
|
|
|
|
### Updated penalty values
|
|
|
|
This patch updates a few configuration values to move penalty constants toward their final, maxmium security values.
|
|
|
|
*Note*: The spec does *not* override previous configuration values but instead creates new values and replaces usage throughout.
|
|
|
|
| Name | Value |
|
|
| - | - |
|
|
| `ALTAIR_INACTIVITY_PENALTY_QUOTIENT` | `uint64(3 * 2**24)` (= 50,331,648) |
|
|
| `ALTAIR_MIN_SLASHING_PENALTY_QUOTIENT` | `uint64(2**6)` (=64) |
|
|
| `ALTAIR_PROPORTIONAL_SLASHING_MULTIPLIER` | `uint64(2)` |
|
|
|
|
### Misc
|
|
|
|
| Name | Value |
|
|
| - | - |
|
|
| `SYNC_COMMITTEE_SIZE` | `uint64(2**10)` (= 1,024) |
|
|
| `SYNC_SUBCOMMITTEE_SIZE` | `uint64(2**6)` (= 64) |
|
|
| `LEAK_SCORE_BIAS` | 4 |
|
|
|
|
### Time parameters
|
|
|
|
| Name | Value | Unit | Duration |
|
|
| - | - | :-: | :-: |
|
|
| `EPOCHS_PER_SYNC_COMMITTEE_PERIOD` | `Epoch(2**8)` (= 256) | epochs | ~27 hours |
|
|
|
|
### Domain types
|
|
|
|
| Name | Value |
|
|
| - | - |
|
|
| `DOMAIN_SYNC_COMMITTEE` | `DomainType('0x07000000')` |
|
|
|
|
## Containers
|
|
|
|
### Modified containers
|
|
|
|
#### `BeaconBlockBody`
|
|
|
|
```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 committee aggregate signature
|
|
sync_committee_bits: Bitvector[SYNC_COMMITTEE_SIZE] # [New in Altair]
|
|
sync_committee_signature: BLSSignature # [New in Altair]
|
|
```
|
|
|
|
#### `BeaconState`
|
|
|
|
```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
|
|
eth1_data_votes: List[Eth1Data, EPOCHS_PER_ETH1_VOTING_PERIOD * SLOTS_PER_EPOCH]
|
|
eth1_deposit_index: uint64
|
|
# 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
|
|
# Participation
|
|
previous_epoch_participation: List[ParticipationFlags, VALIDATOR_REGISTRY_LIMIT] # [New in Altair]
|
|
current_epoch_participation: List[ParticipationFlags, VALIDATOR_REGISTRY_LIMIT] # [New in Altair]
|
|
# Finality
|
|
justification_bits: Bitvector[JUSTIFICATION_BITS_LENGTH] # Bit set for every recent justified epoch
|
|
previous_justified_checkpoint: Checkpoint
|
|
current_justified_checkpoint: Checkpoint
|
|
finalized_checkpoint: Checkpoint
|
|
# Light client sync committees
|
|
current_sync_committee: SyncCommittee # [New in Altair]
|
|
next_sync_committee: SyncCommittee # [New in Altair]
|
|
# Leak
|
|
leak_scores: List[uint64, VALIDATOR_REGISTRY_LIMIT] # [New in Altair]
|
|
```
|
|
|
|
### New containers
|
|
|
|
#### `SyncCommittee`
|
|
|
|
```python
|
|
class SyncCommittee(Container):
|
|
pubkeys: Vector[BLSPubkey, SYNC_COMMITTEE_SIZE]
|
|
pubkey_aggregates: Vector[BLSPubkey, SYNC_COMMITTEE_SIZE // SYNC_SUBCOMMITTEE_SIZE]
|
|
```
|
|
|
|
## Helper functions
|
|
|
|
### `Predicates`
|
|
|
|
#### `eth2_fast_aggregate_verify`
|
|
|
|
```python
|
|
def eth2_fast_aggregate_verify(pubkeys: Sequence[BLSPubkey], message: Bytes32, signature: BLSSignature) -> bool:
|
|
"""
|
|
Wrapper to ``bls.FastAggregateVerify`` accepting the ``G2_POINT_AT_INFINITY`` signature when ``pubkeys`` is empty.
|
|
"""
|
|
if len(pubkeys) == 0 and signature == G2_POINT_AT_INFINITY:
|
|
return True
|
|
return bls.FastAggregateVerify(pubkeys, message, signature)
|
|
```
|
|
|
|
### Misc
|
|
|
|
#### `get_flag_indices_and_numerators`
|
|
|
|
```python
|
|
def get_flag_indices_and_numerators() -> Sequence[Tuple[int, int]]:
|
|
return (
|
|
(TIMELY_HEAD_FLAG_INDEX, TIMELY_HEAD_FLAG_NUMERATOR),
|
|
(TIMELY_SOURCE_FLAG_INDEX, TIMELY_SOURCE_FLAG_NUMERATOR),
|
|
(TIMELY_TARGET_FLAG_INDEX, TIMELY_TARGET_FLAG_NUMERATOR),
|
|
)
|
|
```
|
|
|
|
#### `add_flag`
|
|
|
|
```python
|
|
def add_flag(flags: ParticipationFlags, flag_index: int) -> ParticipationFlags:
|
|
flag = ParticipationFlags(2**flag_index)
|
|
return flags | flag
|
|
```
|
|
|
|
#### `has_flag`
|
|
|
|
```python
|
|
def has_flag(flags: ParticipationFlags, flag_index: int) -> bool:
|
|
flag = ParticipationFlags(2**flag_index)
|
|
return flags & flag == flag
|
|
```
|
|
|
|
### Beacon state accessors
|
|
|
|
#### `get_sync_committee_indices`
|
|
|
|
```python
|
|
def get_sync_committee_indices(state: BeaconState, epoch: Epoch) -> Sequence[ValidatorIndex]:
|
|
"""
|
|
Return the sequence of sync committee indices (which may include duplicate indices) for a given state and epoch.
|
|
"""
|
|
MAX_RANDOM_BYTE = 2**8 - 1
|
|
base_epoch = Epoch((max(epoch // EPOCHS_PER_SYNC_COMMITTEE_PERIOD, 1) - 1) * EPOCHS_PER_SYNC_COMMITTEE_PERIOD)
|
|
active_validator_indices = get_active_validator_indices(state, base_epoch)
|
|
active_validator_count = uint64(len(active_validator_indices))
|
|
seed = get_seed(state, base_epoch, DOMAIN_SYNC_COMMITTEE)
|
|
i = 0
|
|
sync_committee_indices: List[ValidatorIndex] = []
|
|
while len(sync_committee_indices) < SYNC_COMMITTEE_SIZE:
|
|
shuffled_index = compute_shuffled_index(uint64(i % active_validator_count), active_validator_count, seed)
|
|
candidate_index = active_validator_indices[shuffled_index]
|
|
random_byte = hash(seed + uint_to_bytes(uint64(i // 32)))[i % 32]
|
|
effective_balance = state.validators[candidate_index].effective_balance
|
|
if effective_balance * MAX_RANDOM_BYTE >= MAX_EFFECTIVE_BALANCE * random_byte: # Sample with replacement
|
|
sync_committee_indices.append(candidate_index)
|
|
i += 1
|
|
return sync_committee_indices
|
|
```
|
|
|
|
#### `get_sync_committee`
|
|
|
|
```python
|
|
def get_sync_committee(state: BeaconState, epoch: Epoch) -> SyncCommittee:
|
|
"""
|
|
Return the sync committee for a given state and epoch.
|
|
"""
|
|
indices = get_sync_committee_indices(state, epoch)
|
|
pubkeys = [state.validators[index].pubkey for index in indices]
|
|
subcommitees = [pubkeys[i:i + SYNC_SUBCOMMITTEE_SIZE] for i in range(0, len(pubkeys), SYNC_SUBCOMMITTEE_SIZE)]
|
|
pubkey_aggregates = [bls.AggregatePKs(subcommitee) for subcommitee in subcommitees]
|
|
return SyncCommittee(pubkeys=pubkeys, pubkey_aggregates=pubkey_aggregates)
|
|
```
|
|
|
|
#### `get_base_reward`
|
|
|
|
*Note*: The function `get_base_reward` is modified with the removal of `BASE_REWARDS_PER_EPOCH`.
|
|
|
|
```python
|
|
def get_base_reward(state: BeaconState, index: ValidatorIndex) -> Gwei:
|
|
total_balance = get_total_active_balance(state)
|
|
effective_balance = state.validators[index].effective_balance
|
|
return Gwei(effective_balance * BASE_REWARD_FACTOR // integer_squareroot(total_balance))
|
|
```
|
|
|
|
#### `get_unslashed_participating_indices`
|
|
|
|
```python
|
|
def get_unslashed_participating_indices(state: BeaconState, flag_index: int, epoch: Epoch) -> Set[ValidatorIndex]:
|
|
"""
|
|
Retrieve the active and unslashed validator indices for the given epoch and flag index.
|
|
"""
|
|
assert epoch in (get_previous_epoch(state), get_current_epoch(state))
|
|
if epoch == get_current_epoch(state):
|
|
epoch_participation = state.current_epoch_participation
|
|
else:
|
|
epoch_participation = state.previous_epoch_participation
|
|
active_validator_indices = get_active_validator_indices(state, epoch)
|
|
participating_indices = [i for i in active_validator_indices if has_flag(epoch_participation[i], flag_index)]
|
|
return set(filter(lambda index: not state.validators[index].slashed, participating_indices))
|
|
```
|
|
|
|
#### `get_flag_deltas`
|
|
|
|
```python
|
|
def get_flag_deltas(state: BeaconState,
|
|
flag_index: int,
|
|
numerator: uint64) -> Tuple[Sequence[Gwei], Sequence[Gwei]]:
|
|
"""
|
|
Compute the rewards and penalties associated with a particular duty, by scanning through the participation
|
|
flags to determine who participated and who did not and assigning them the appropriate rewards and penalties.
|
|
"""
|
|
rewards = [Gwei(0)] * len(state.validators)
|
|
penalties = [Gwei(0)] * len(state.validators)
|
|
|
|
unslashed_participating_indices = get_unslashed_participating_indices(state, flag_index, get_previous_epoch(state))
|
|
increment = EFFECTIVE_BALANCE_INCREMENT # Factored out from balances to avoid uint64 overflow
|
|
unslashed_participating_increments = get_total_balance(state, unslashed_participating_indices) // increment
|
|
active_increments = get_total_active_balance(state) // increment
|
|
for index in get_eligible_validator_indices(state):
|
|
base_reward = get_base_reward(state, index)
|
|
if index in unslashed_participating_indices:
|
|
if is_in_inactivity_leak(state):
|
|
# Optimal participation is fully rewarded to cancel the inactivity penalty
|
|
rewards[index] = base_reward * numerator // FLAG_DENOMINATOR
|
|
else:
|
|
rewards[index] = (
|
|
(base_reward * numerator * unslashed_participating_increments)
|
|
// (active_increments * FLAG_DENOMINATOR)
|
|
)
|
|
else:
|
|
penalties[index] = base_reward * numerator // FLAG_DENOMINATOR
|
|
return rewards, penalties
|
|
```
|
|
|
|
#### New `get_inactivity_penalty_deltas`
|
|
|
|
*Note*: The function `get_inactivity_penalty_deltas` is modified in the selection of matching target indices
|
|
and the removal of `BASE_REWARDS_PER_EPOCH`.
|
|
|
|
```python
|
|
def get_inactivity_penalty_deltas(state: BeaconState) -> Tuple[Sequence[Gwei], Sequence[Gwei]]:
|
|
"""
|
|
Compute the penalties associated with the inactivity leak, by scanning through the participation
|
|
flags to determine who participated and who did not, applying the leak penalty globally and applying
|
|
compensatory rewards to participants.
|
|
"""
|
|
rewards = [Gwei(0) for _ in range(len(state.validators))]
|
|
penalties = [Gwei(0) for _ in range(len(state.validators))]
|
|
|
|
if not is_in_inactivity_leak(state):
|
|
return rewards, penalties
|
|
|
|
reward_numerator_sum = sum(numerator for (_, numerator) in get_flag_indices_and_numerators())
|
|
matching_target_attesting_indices = get_unslashed_participating_indices(
|
|
state, TIMELY_TARGET_FLAG_INDEX, get_previous_epoch(state)
|
|
)
|
|
for index in get_eligible_validator_indices(state):
|
|
# If validator is performing optimally this cancels all attestation rewards for a neutral balance
|
|
penalties[index] += Gwei(get_base_reward(state, index) * reward_numerator_sum // FLAG_DENOMINATOR)
|
|
if index not in matching_target_attesting_indices and state.leak_scores[index] >= LEAK_SCORE_BIAS:
|
|
effective_balance = state.validators[index].effective_balance
|
|
leak_penalty = Gwei(
|
|
effective_balance * state.leak_scores[index] // LEAK_SCORE_BIAS // ALTAIR_INACTIVITY_PENALTY_QUOTIENT
|
|
)
|
|
penalties[index] += leak_penalty
|
|
|
|
return rewards, penalties
|
|
```
|
|
|
|
### Beacon state mutators
|
|
|
|
#### New `slash_validator`
|
|
|
|
*Note*: The function `slash_validator` is modified
|
|
with the substitution of `MIN_SLASHING_PENALTY_QUOTIENT` with `ALTAIR_MIN_SLASHING_PENALTY_QUOTIENT`.
|
|
|
|
```python
|
|
def slash_validator(state: BeaconState,
|
|
slashed_index: ValidatorIndex,
|
|
whistleblower_index: ValidatorIndex=None) -> None:
|
|
"""
|
|
Slash the validator with index ``slashed_index``.
|
|
"""
|
|
epoch = get_current_epoch(state)
|
|
initiate_validator_exit(state, slashed_index)
|
|
validator = state.validators[slashed_index]
|
|
validator.slashed = True
|
|
validator.withdrawable_epoch = max(validator.withdrawable_epoch, Epoch(epoch + EPOCHS_PER_SLASHINGS_VECTOR))
|
|
state.slashings[epoch % EPOCHS_PER_SLASHINGS_VECTOR] += validator.effective_balance
|
|
decrease_balance(state, slashed_index, validator.effective_balance // ALTAIR_MIN_SLASHING_PENALTY_QUOTIENT)
|
|
|
|
# Apply proposer and whistleblower rewards
|
|
proposer_index = get_beacon_proposer_index(state)
|
|
if whistleblower_index is None:
|
|
whistleblower_index = proposer_index
|
|
whistleblower_reward = Gwei(validator.effective_balance // WHISTLEBLOWER_REWARD_QUOTIENT)
|
|
proposer_reward = Gwei(whistleblower_reward // PROPOSER_REWARD_QUOTIENT)
|
|
increase_balance(state, proposer_index, proposer_reward)
|
|
increase_balance(state, whistleblower_index, Gwei(whistleblower_reward - proposer_reward))
|
|
```
|
|
|
|
### 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)
|
|
process_operations(state, block.body) # [Modified in Altair]
|
|
process_sync_committee(state, block.body) # [New in Altair]
|
|
```
|
|
|
|
#### Modified `process_attestation`
|
|
|
|
*Note*: The function `process_attestation` is modified to do incentive accounting with epoch participation flags.
|
|
|
|
```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 <= data.slot + SLOTS_PER_EPOCH
|
|
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)
|
|
|
|
if data.target.epoch == get_current_epoch(state):
|
|
epoch_participation = state.current_epoch_participation
|
|
justified_checkpoint = state.current_justified_checkpoint
|
|
else:
|
|
epoch_participation = state.previous_epoch_participation
|
|
justified_checkpoint = state.previous_justified_checkpoint
|
|
|
|
# Matching roots
|
|
is_matching_head = data.beacon_block_root == get_block_root_at_slot(state, data.slot)
|
|
is_matching_source = data.source == justified_checkpoint
|
|
is_matching_target = data.target.root == get_block_root(state, data.target.epoch)
|
|
assert is_matching_source
|
|
|
|
# Verify signature
|
|
assert is_valid_indexed_attestation(state, get_indexed_attestation(state, attestation))
|
|
|
|
# Participation flag indices
|
|
participation_flag_indices = []
|
|
if is_matching_head and is_matching_target and state.slot <= data.slot + MIN_ATTESTATION_INCLUSION_DELAY:
|
|
participation_flag_indices.append(TIMELY_HEAD_FLAG_INDEX)
|
|
if is_matching_source and state.slot <= data.slot + integer_squareroot(SLOTS_PER_EPOCH):
|
|
participation_flag_indices.append(TIMELY_SOURCE_FLAG_INDEX)
|
|
if is_matching_target and state.slot <= data.slot + SLOTS_PER_EPOCH:
|
|
participation_flag_indices.append(TIMELY_TARGET_FLAG_INDEX)
|
|
|
|
# Update epoch participation flags
|
|
proposer_reward_numerator = 0
|
|
for index in get_attesting_indices(state, data, attestation.aggregation_bits):
|
|
for flag_index, flag_numerator in get_flag_indices_and_numerators():
|
|
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) * flag_numerator
|
|
|
|
# Reward proposer
|
|
proposer_reward = Gwei(proposer_reward_numerator // (FLAG_DENOMINATOR * PROPOSER_REWARD_QUOTIENT))
|
|
increase_balance(state, get_beacon_proposer_index(state), proposer_reward)
|
|
```
|
|
|
|
|
|
#### Modified `process_deposit`
|
|
|
|
*Note*: The function `process_deposit` is modified to initialize `leak_scores`, `previous_epoch_participation`, `current_epoch_participation`.
|
|
|
|
```python
|
|
def process_deposit(state: BeaconState, deposit: Deposit) -> None:
|
|
# Verify the Merkle branch
|
|
assert is_valid_merkle_branch(
|
|
leaf=hash_tree_root(deposit.data),
|
|
branch=deposit.proof,
|
|
depth=DEPOSIT_CONTRACT_TREE_DEPTH + 1, # Add 1 for the List length mix-in
|
|
index=state.eth1_deposit_index,
|
|
root=state.eth1_data.deposit_root,
|
|
)
|
|
|
|
# Deposits must be processed in order
|
|
state.eth1_deposit_index += 1
|
|
|
|
pubkey = deposit.data.pubkey
|
|
amount = deposit.data.amount
|
|
validator_pubkeys = [v.pubkey for v in state.validators]
|
|
if pubkey not in validator_pubkeys:
|
|
# Verify the deposit signature (proof of possession) which is not checked by the deposit contract
|
|
deposit_message = DepositMessage(
|
|
pubkey=deposit.data.pubkey,
|
|
withdrawal_credentials=deposit.data.withdrawal_credentials,
|
|
amount=deposit.data.amount,
|
|
)
|
|
domain = compute_domain(DOMAIN_DEPOSIT) # Fork-agnostic domain since deposits are valid across forks
|
|
signing_root = compute_signing_root(deposit_message, domain)
|
|
if not bls.Verify(pubkey, signing_root, deposit.data.signature):
|
|
return
|
|
|
|
# Add validator and balance entries
|
|
state.validators.append(get_validator_from_deposit(state, deposit))
|
|
state.balances.append(amount)
|
|
state.previous_epoch_participation.append(ParticipationFlags(0b0000_0000)) # [New in Altair]
|
|
state.current_epoch_participation.append(ParticipationFlags(0b0000_0000)) # [New in Altair]
|
|
state.leak_scores.append(0) # [New in Altair]
|
|
else:
|
|
# Increase balance by deposit amount
|
|
index = ValidatorIndex(validator_pubkeys.index(pubkey))
|
|
increase_balance(state, index, amount)
|
|
```
|
|
|
|
#### Sync committee processing
|
|
|
|
```python
|
|
def process_sync_committee(state: BeaconState, body: BeaconBlockBody) -> None:
|
|
# Verify sync committee aggregate signature signing over the previous slot block root
|
|
previous_slot = Slot(max(int(state.slot), 1) - 1)
|
|
committee_indices = get_sync_committee_indices(state, get_current_epoch(state))
|
|
participant_indices = [index for index, bit in zip(committee_indices, body.sync_committee_bits) if bit]
|
|
committee_pubkeys = state.current_sync_committee.pubkeys
|
|
participant_pubkeys = [pubkey for pubkey, bit in zip(committee_pubkeys, body.sync_committee_bits) if bit]
|
|
domain = get_domain(state, DOMAIN_SYNC_COMMITTEE, compute_epoch_at_slot(previous_slot))
|
|
signing_root = compute_signing_root(get_block_root_at_slot(state, previous_slot), domain)
|
|
assert eth2_fast_aggregate_verify(participant_pubkeys, signing_root, body.sync_committee_signature)
|
|
|
|
# Reward sync committee participants
|
|
proposer_rewards = Gwei(0)
|
|
active_validator_count = uint64(len(get_active_validator_indices(state, get_current_epoch(state))))
|
|
for participant_index in participant_indices:
|
|
proposer_reward = get_proposer_reward(state, participant_index)
|
|
proposer_rewards += proposer_reward
|
|
base_reward = get_base_reward(state, participant_index)
|
|
max_participant_reward = base_reward - proposer_reward
|
|
reward = Gwei(max_participant_reward * active_validator_count // (len(committee_indices) * SLOTS_PER_EPOCH))
|
|
increase_balance(state, participant_index, reward)
|
|
|
|
# Reward beacon proposer
|
|
increase_balance(state, get_beacon_proposer_index(state), proposer_rewards)
|
|
```
|
|
|
|
### Epoch processing
|
|
|
|
```python
|
|
def process_epoch(state: BeaconState) -> None:
|
|
process_justification_and_finalization(state) # [Modified in Altair]
|
|
process_leak_updates(state) # [New in Altair]
|
|
process_rewards_and_penalties(state) # [Modified in Altair]
|
|
process_registry_updates(state)
|
|
process_slashings(state) # [Modified in Altair]
|
|
process_eth1_data_reset(state)
|
|
process_effective_balance_updates(state)
|
|
process_slashings_reset(state)
|
|
process_randao_mixes_reset(state)
|
|
process_historical_roots_update(state)
|
|
process_participation_flag_updates(state) # [New in Altair]
|
|
process_sync_committee_updates(state) # [New in Altair]
|
|
```
|
|
|
|
#### Justification and finalization
|
|
|
|
*Note*: The function `process_justification_and_finalization` is modified with `matching_target_attestations` replaced by `matching_target_indices`.
|
|
|
|
```python
|
|
def process_justification_and_finalization(state: BeaconState) -> None:
|
|
# Initial FFG checkpoint values have a `0x00` stub for `root`.
|
|
# Skip FFG updates in the first two epochs to avoid corner cases that might result in modifying this stub.
|
|
if get_current_epoch(state) <= GENESIS_EPOCH + 1:
|
|
return
|
|
previous_epoch = get_previous_epoch(state)
|
|
current_epoch = get_current_epoch(state)
|
|
old_previous_justified_checkpoint = state.previous_justified_checkpoint
|
|
old_current_justified_checkpoint = state.current_justified_checkpoint
|
|
|
|
# Process justifications
|
|
state.previous_justified_checkpoint = state.current_justified_checkpoint
|
|
state.justification_bits[1:] = state.justification_bits[:JUSTIFICATION_BITS_LENGTH - 1]
|
|
state.justification_bits[0] = 0b0
|
|
matching_target_indices = get_unslashed_participating_indices(state, TIMELY_TARGET_FLAG_INDEX, previous_epoch)
|
|
if get_total_balance(state, matching_target_indices) * 3 >= get_total_active_balance(state) * 2:
|
|
state.current_justified_checkpoint = Checkpoint(epoch=previous_epoch,
|
|
root=get_block_root(state, previous_epoch))
|
|
state.justification_bits[1] = 0b1
|
|
matching_target_indices = get_unslashed_participating_indices(state, TIMELY_TARGET_FLAG_INDEX, current_epoch)
|
|
if get_total_balance(state, matching_target_indices) * 3 >= get_total_active_balance(state) * 2:
|
|
state.current_justified_checkpoint = Checkpoint(epoch=current_epoch,
|
|
root=get_block_root(state, current_epoch))
|
|
state.justification_bits[0] = 0b1
|
|
|
|
# Process finalizations
|
|
bits = state.justification_bits
|
|
# The 2nd/3rd/4th most recent epochs are justified, the 2nd using the 4th as source
|
|
if all(bits[1:4]) and old_previous_justified_checkpoint.epoch + 3 == current_epoch:
|
|
state.finalized_checkpoint = old_previous_justified_checkpoint
|
|
# The 2nd/3rd most recent epochs are justified, the 2nd using the 3rd as source
|
|
if all(bits[1:3]) and old_previous_justified_checkpoint.epoch + 2 == current_epoch:
|
|
state.finalized_checkpoint = old_previous_justified_checkpoint
|
|
# The 1st/2nd/3rd most recent epochs are justified, the 1st using the 3rd as source
|
|
if all(bits[0:3]) and old_current_justified_checkpoint.epoch + 2 == current_epoch:
|
|
state.finalized_checkpoint = old_current_justified_checkpoint
|
|
# The 1st/2nd most recent epochs are justified, the 1st using the 2nd as source
|
|
if all(bits[0:2]) and old_current_justified_checkpoint.epoch + 1 == current_epoch:
|
|
state.finalized_checkpoint = old_current_justified_checkpoint
|
|
```
|
|
|
|
#### Leak scores
|
|
|
|
*Note*: The function `process_leak_updates` is new.
|
|
|
|
```python
|
|
def process_leak_updates(state: BeaconState) -> None:
|
|
matching_target_attesting_indices = get_unslashed_participating_indices(
|
|
state, TIMELY_TARGET_FLAG_INDEX, get_previous_epoch(state)
|
|
)
|
|
for index in get_eligible_validator_indices(state):
|
|
if index in matching_target_attesting_indices:
|
|
if state.leak_scores[index] > 0:
|
|
state.leak_scores[index] -= 1
|
|
elif is_in_inactivity_leak(state):
|
|
state.leak_scores[index] += LEAK_SCORE_BIAS
|
|
```
|
|
|
|
#### Rewards and penalties
|
|
|
|
*Note*: The function `process_rewards_and_penalties` is modified to support the incentive reforms.
|
|
|
|
```python
|
|
def process_rewards_and_penalties(state: BeaconState) -> None:
|
|
# No rewards are applied at the end of `GENESIS_EPOCH` because rewards are for work done in the previous epoch
|
|
if get_current_epoch(state) == GENESIS_EPOCH:
|
|
return
|
|
flag_deltas = [
|
|
get_flag_deltas(state, flag_index, flag_numerator)
|
|
for (flag_index, flag_numerator) in get_flag_indices_and_numerators()
|
|
]
|
|
deltas = flag_deltas + [get_inactivity_penalty_deltas(state)]
|
|
for (rewards, penalties) in deltas:
|
|
for index in range(len(state.validators)):
|
|
increase_balance(state, ValidatorIndex(index), rewards[index])
|
|
decrease_balance(state, ValidatorIndex(index), penalties[index])
|
|
```
|
|
|
|
#### Slashings
|
|
|
|
*Note*: The function `process_slashings` is modified to use `ALTAIR_PROPORTIONAL_SLASHING_MULTIPLIER`.
|
|
|
|
```python
|
|
def process_slashings(state: BeaconState) -> None:
|
|
epoch = get_current_epoch(state)
|
|
total_balance = get_total_active_balance(state)
|
|
adjusted_total_slashing_balance = min(sum(state.slashings) * ALTAIR_PROPORTIONAL_SLASHING_MULTIPLIER, total_balance)
|
|
for index, validator in enumerate(state.validators):
|
|
if validator.slashed and epoch + EPOCHS_PER_SLASHINGS_VECTOR // 2 == validator.withdrawable_epoch:
|
|
increment = EFFECTIVE_BALANCE_INCREMENT # Factored out from penalty numerator to avoid uint64 overflow
|
|
penalty_numerator = validator.effective_balance // increment * adjusted_total_slashing_balance
|
|
penalty = penalty_numerator // total_balance * increment
|
|
decrease_balance(state, ValidatorIndex(index), penalty)
|
|
```
|
|
|
|
#### Participation flags updates
|
|
|
|
*Note*: The function `process_participation_flag_updates` is new.
|
|
|
|
```python
|
|
def process_participation_flag_updates(state: BeaconState) -> None:
|
|
state.previous_epoch_participation = state.current_epoch_participation
|
|
state.current_epoch_participation = [ParticipationFlags(0b0000_0000) for _ in range(len(state.validators))]
|
|
```
|
|
|
|
#### Sync committee updates
|
|
|
|
*Note*: The function `process_sync_committee_updates` is new.
|
|
|
|
```python
|
|
def process_sync_committee_updates(state: BeaconState) -> None:
|
|
next_epoch = get_current_epoch(state) + Epoch(1)
|
|
if next_epoch % EPOCHS_PER_SYNC_COMMITTEE_PERIOD == 0:
|
|
state.current_sync_committee = state.next_sync_committee
|
|
state.next_sync_committee = get_sync_committee(state, next_epoch + EPOCHS_PER_SYNC_COMMITTEE_PERIOD)
|
|
```
|