helpers

package
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 Go to latest Published: Oct 19, 2023 License: GPL-3.0 Imports: 32 Imported by: 0

Documentation

Overview

Package helpers contains helper functions outlined in the Ethereum Beacon Chain spec, such as computing committees, randao, rewards/penalties, and more.

Package helpers contains helper functions outlined in the Ethereum Beacon Chain spec, such as computing committees, randao, rewards/penalties, and more.

Index

Constants

This section is empty.

Variables

View Source 
var CommitteeCacheInProgressHit = promauto.NewCounter(prometheus.CounterOpts{
	Name: "committee_cache_in_progress_hit",
	Help: "The number of committee requests that are present in the cache.",
})
View Source 
var (
	ErrTooLate = errors.New("attestation is too late")
)

Functions

func ActivationExitEpoch 

func ActivationExitEpoch(epoch primitives.Epoch) primitives.Epoch

ActivationExitEpoch takes in epoch number and returns when the validator is eligible for activation and exit.

Spec pseudocode definition: 

def compute_activation_exit_epoch(epoch: Epoch) -> Epoch:
  """
  Return the epoch during which validator activations and exits initiated in ``epoch`` take effect.
  """
  return Epoch(epoch + 1 + MAX_SEED_LOOKAHEAD)

func ActiveValidatorCount 

func ActiveValidatorCount(ctx context.Context, s state.ReadOnlyBeaconState, epoch primitives.Epoch) (uint64, error)

ActiveValidatorCount returns the number of active validators in the state at the given epoch.

func ActiveValidatorIndices 

func ActiveValidatorIndices(ctx context.Context, s state.ReadOnlyBeaconState, epoch primitives.Epoch) ([]primitives.ValidatorIndex, error)

ActiveValidatorIndices filters out active validators based on validator status and returns their indices in a list.

WARNING: This method allocates a new copy of the validator index set and is considered to be very memory expensive. Avoid using this unless you really need the active validator indices for some specific reason.

Spec pseudocode definition: 

def get_active_validator_indices(state: BeaconState, epoch: Epoch) -> Sequence[ValidatorIndex]:
  """
  Return the sequence of active validator indices at ``epoch``.
  """
  return [ValidatorIndex(i) for i, v in enumerate(state.validators) if is_active_validator(v, epoch)]

func BeaconCommittee 

func BeaconCommittee(
	ctx context.Context,
	validatorIndices []primitives.ValidatorIndex,
	seed [32]byte,
	slot primitives.Slot,
	committeeIndex primitives.CommitteeIndex,
) ([]primitives.ValidatorIndex, error)

BeaconCommittee returns the beacon committee of a given slot and committee index. The validator indices and seed are provided as an argument rather than an imported implementation from the spec definition. Having them as an argument allows for cheaper computation run time.

Spec pseudocode definition: 

def get_beacon_committee(state: BeaconState, slot: Slot, index: CommitteeIndex) -> Sequence[ValidatorIndex]:
 """
 Return the beacon committee at ``slot`` for ``index``.
 """
 epoch = compute_epoch_at_slot(slot)
 committees_per_slot = get_committee_count_per_slot(state, epoch)
 return compute_committee(
     indices=get_active_validator_indices(state, epoch),
     seed=get_seed(state, epoch, DOMAIN_BEACON_ATTESTER),
     index=(slot % SLOTS_PER_EPOCH) * committees_per_slot + index,
     count=committees_per_slot * SLOTS_PER_EPOCH,
 )

func BeaconCommitteeFromState 

func BeaconCommitteeFromState(ctx context.Context, state state.ReadOnlyBeaconState, slot primitives.Slot, committeeIndex primitives.CommitteeIndex) ([]primitives.ValidatorIndex, error)

BeaconCommitteeFromState returns the crosslink committee of a given slot and committee index. This is a spec implementation where state is used as an argument. In case of state retrieval becomes expensive, consider using BeaconCommittee below.

Spec pseudocode definition: 

def get_beacon_committee(state: BeaconState, slot: Slot, index: CommitteeIndex) -> Sequence[ValidatorIndex]:
 """
 Return the beacon committee at ``slot`` for ``index``.
 """
 epoch = compute_epoch_at_slot(slot)
 committees_per_slot = get_committee_count_per_slot(state, epoch)
 return compute_committee(
     indices=get_active_validator_indices(state, epoch),
     seed=get_seed(state, epoch, DOMAIN_BEACON_ATTESTER),
     index=(slot % SLOTS_PER_EPOCH) * committees_per_slot + index,
     count=committees_per_slot * SLOTS_PER_EPOCH,
 )

func BeaconProposerIndex 

func BeaconProposerIndex(ctx context.Context, state state.ReadOnlyBeaconState) (primitives.ValidatorIndex, error)

BeaconProposerIndex returns proposer index of a current slot.

Spec pseudocode definition: 

def get_beacon_proposer_index(state: BeaconState) -> ValidatorIndex:
  """
  Return the beacon proposer index at the current slot.
  """
  epoch = get_current_epoch(state)
  seed = hash(get_seed(state, epoch, DOMAIN_BEACON_PROPOSER) + uint_to_bytes(state.slot))
  indices = get_active_validator_indices(state, epoch)
  return compute_proposer_index(state, indices, seed)

func BlockRoot 

func BlockRoot(state state.ReadOnlyBeaconState, epoch primitives.Epoch) ([]byte, error)

BlockRoot returns the block root stored in the BeaconState for epoch start slot.

Spec pseudocode definition: 

def get_block_root(state: BeaconState, epoch: Epoch) -> Root:
  """
  Return the block root at the start of a recent ``epoch``.
  """
  return get_block_root_at_slot(state, compute_start_slot_at_epoch(epoch))

func BlockRootAtSlot 

func BlockRootAtSlot(state state.ReadOnlyBeaconState, slot primitives.Slot) ([]byte, error)

BlockRootAtSlot returns the block root stored in the BeaconState for a recent slot. It returns an error if the requested block root is not within the slot range.

Spec pseudocode definition: 

def get_block_root_at_slot(state: BeaconState, slot: Slot) -> Root:
  """
  Return the block root at a recent ``slot``.
  """
  assert slot < state.slot <= slot + SLOTS_PER_HISTORICAL_ROOT
  return state.block_roots[slot % SLOTS_PER_HISTORICAL_ROOT]

func ClearCache 

func ClearCache()

ClearCache clears the beacon committee cache and sync committee cache.

func CommitteeAssignments 

func CommitteeAssignments(
	ctx context.Context,
	state state.BeaconState,
	epoch primitives.Epoch,
) (map[primitives.ValidatorIndex]*CommitteeAssignmentContainer, map[primitives.ValidatorIndex][]primitives.Slot, error)

CommitteeAssignments is a map of validator indices pointing to the appropriate committee assignment for the given epoch.

1. Determine the proposer validator index for each slot. 2. Compute all committees. 3. Determine the attesting slot for each committee. 4. Construct a map of validator indices pointing to the respective committees.

func ComputeProposerIndex 

func ComputeProposerIndex(bState state.ReadOnlyValidators, activeIndices []primitives.ValidatorIndex, seed [32]byte) (primitives.ValidatorIndex, error)

ComputeProposerIndex returns the index sampled by effective balance, which is used to calculate proposer.

nolint:dupword Spec pseudocode definition: 

def compute_proposer_index(state: BeaconState, indices: Sequence[ValidatorIndex], seed: Bytes32) -> ValidatorIndex:
  """
  Return from ``indices`` a random index sampled by effective balance.
  """
  assert len(indices) > 0
  MAX_RANDOM_BYTE = 2**8 - 1
  i = uint64(0)
  total = uint64(len(indices))
  while True:
      candidate_index = indices[compute_shuffled_index(i % total, total, seed)]
      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:
          return candidate_index
      i += 1

func ComputeShuffledIndex 

func ComputeShuffledIndex(index primitives.ValidatorIndex, indexCount uint64, seed [32]byte, shuffle bool) (primitives.ValidatorIndex, error)

ComputeShuffledIndex returns the shuffled validator index corresponding to seed and index count. Spec pseudocode definition: 

def compute_shuffled_index(index: uint64, index_count: uint64, seed: Bytes32) -> uint64:
 """
 Return the shuffled index corresponding to ``seed`` (and ``index_count``).
 """
 assert index < index_count

 # Swap or not (https://link.springer.com/content/pdf/10.1007%2F978-3-642-32009-5_1.pdf)
 # See the 'generalized domain' algorithm on page 3
 for current_round in range(SHUFFLE_ROUND_COUNT):
     pivot = bytes_to_uint64(hash(seed + uint_to_bytes(uint8(current_round)))[0:8]) % index_count
     flip = (pivot + index_count - index) % index_count
     position = max(index, flip)
     source = hash(
         seed
         + uint_to_bytes(uint8(current_round))
         + uint_to_bytes(uint32(position // 256))
     )
     byte = uint8(source[(position % 256) // 8])
     bit = (byte >> (position % 8)) % 2
     index = flip if bit else index

 return index

func ComputeSubnetForAttestation 

func ComputeSubnetForAttestation(activeValCount uint64, att *ethpb.Attestation) uint64

ComputeSubnetForAttestation returns the subnet for which the provided attestation will be broadcasted to. This differs from the spec definition by instead passing in the active validators indices in the attestation's given epoch.

Spec pseudocode definition: def compute_subnet_for_attestation(committees_per_slot: uint64, slot: Slot, committee_index: CommitteeIndex) -> uint64: 

"""
Compute the correct subnet for an attestation for Phase 0.
Note, this mimics expected future behavior where attestations will be mapped to their shard subnet.
"""
slots_since_epoch_start = uint64(slot % SLOTS_PER_EPOCH)
committees_since_epoch_start = committees_per_slot * slots_since_epoch_start

return uint64((committees_since_epoch_start + committee_index) % ATTESTATION_SUBNET_COUNT)

func ComputeSubnetFromCommitteeAndSlot 

func ComputeSubnetFromCommitteeAndSlot(activeValCount uint64, comIdx primitives.CommitteeIndex, attSlot primitives.Slot) uint64

ComputeSubnetFromCommitteeAndSlot is a flattened version of ComputeSubnetForAttestation where we only pass in the relevant fields from the attestation as function arguments.

Spec pseudocode definition: def compute_subnet_for_attestation(committees_per_slot: uint64, slot: Slot, committee_index: CommitteeIndex) -> uint64: 

"""
Compute the correct subnet for an attestation for Phase 0.
Note, this mimics expected future behavior where attestations will be mapped to their shard subnet.
"""
slots_since_epoch_start = uint64(slot % SLOTS_PER_EPOCH)
committees_since_epoch_start = committees_per_slot * slots_since_epoch_start

return uint64((committees_since_epoch_start + committee_index) % ATTESTATION_SUBNET_COUNT)

func ComputeWeakSubjectivityPeriod 

func ComputeWeakSubjectivityPeriod(ctx context.Context, st state.ReadOnlyBeaconState, cfg *params.BeaconChainConfig) (primitives.Epoch, error)

ComputeWeakSubjectivityPeriod returns weak subjectivity period for the active validator count and finalized epoch.

Reference spec implementation: https://github.com/ethereum/consensus-specs/blob/master/specs/phase0/weak-subjectivity.md#calculating-the-weak-subjectivity-period

def compute_weak_subjectivity_period(state: BeaconState) -> uint64: 

"""
Returns the weak subjectivity period for the current ``state``.
This computation takes into account the effect of:
    - validator set churn (bounded by ``get_validator_churn_limit()`` per epoch), and
    - validator balance top-ups (bounded by ``MAX_DEPOSITS * SLOTS_PER_EPOCH`` per epoch).
A detailed calculation can be found at:
https://github.com/runtimeverification/beacon-chain-verification/blob/master/weak-subjectivity/weak-subjectivity-analysis.pdf
"""
ws_period = MIN_VALIDATOR_WITHDRAWABILITY_DELAY
N = len(get_active_validator_indices(state, get_current_epoch(state)))
t = get_total_active_balance(state) // N // ETH_TO_GWEI
T = MAX_EFFECTIVE_BALANCE // ETH_TO_GWEI
delta = get_validator_churn_limit(state)
Delta = MAX_DEPOSITS * SLOTS_PER_EPOCH
D = SAFETY_DECAY

if T * (200 + 3 * D) < t * (200 + 12 * D):
    epochs_for_validator_set_churn = (
        N * (t * (200 + 12 * D) - T * (200 + 3 * D)) // (600 * delta * (2 * t + T))
    )
    epochs_for_balance_top_ups = (
        N * (200 + 3 * D) // (600 * Delta)
    )
    ws_period += max(epochs_for_validator_set_churn, epochs_for_balance_top_ups)
else:
    ws_period += (
        3 * N * D * t // (200 * Delta * (T - t))
    )

return ws_period

func CurrentPeriodSyncSubcommitteeIndices 

func CurrentPeriodSyncSubcommitteeIndices(
	st state.BeaconState, valIdx primitives.ValidatorIndex,
) ([]primitives.CommitteeIndex, error)

CurrentPeriodSyncSubcommitteeIndices returns the subcommittee indices of the current period sync committee for input validator.

func DecreaseBalance 

func DecreaseBalance(state state.BeaconState, idx primitives.ValidatorIndex, delta uint64) error

DecreaseBalance decreases validator with the given 'index' balance by 'delta' in Gwei.

Spec pseudocode definition: 

def decrease_balance(state: BeaconState, index: ValidatorIndex, delta: Gwei) -> None:
  """
  Decrease the validator balance at index ``index`` by ``delta``, with underflow protection.
  """
  state.balances[index] = 0 if delta > state.balances[index] else state.balances[index] - delta

func DecreaseBalanceWithVal 

func DecreaseBalanceWithVal(currBalance, delta uint64) uint64

DecreaseBalanceWithVal decreases validator with the given 'index' balance by 'delta' in Gwei. This method is flattened version of the spec method, taking in the raw balance and returning the post balance.

Spec pseudocode definition: 

def decrease_balance(state: BeaconState, index: ValidatorIndex, delta: Gwei) -> None:
  """
  Decrease the validator balance at index ``index`` by ``delta``, with underflow protection.
  """
  state.balances[index] = 0 if delta > state.balances[index] else state.balances[index] - delta

func FinalityDelay 

func FinalityDelay(prevEpoch, finalizedEpoch primitives.Epoch) primitives.Epoch

FinalityDelay returns the finality delay using the beacon state.

Spec code: def get_finality_delay(state: BeaconState) -> uint64: 

return get_previous_epoch(state) - state.finalized_checkpoint.epoch

func IncreaseBalance 

func IncreaseBalance(state state.BeaconState, idx primitives.ValidatorIndex, delta uint64) error

IncreaseBalance increases validator with the given 'index' balance by 'delta' in Gwei.

Spec pseudocode definition: 

def increase_balance(state: BeaconState, index: ValidatorIndex, delta: Gwei) -> None:
  """
  Increase the validator balance at index ``index`` by ``delta``.
  """
  state.balances[index] += delta

func IncreaseBalanceWithVal 

func IncreaseBalanceWithVal(currBalance, delta uint64) (uint64, error)

IncreaseBalanceWithVal increases validator with the given 'index' balance by 'delta' in Gwei. This method is flattened version of the spec method, taking in the raw balance and returning the post balance.

Spec pseudocode definition: 

def increase_balance(state: BeaconState, index: ValidatorIndex, delta: Gwei) -> None:
  """
  Increase the validator balance at index ``index`` by ``delta``.
  """
  state.balances[index] += delta

func IsActiveNonSlashedValidatorUsingTrie 

func IsActiveNonSlashedValidatorUsingTrie(validator state.ReadOnlyValidator, epoch primitives.Epoch) bool

IsActiveNonSlashedValidatorUsingTrie checks if a read only validator is active and not slashed

func IsActiveValidator 

func IsActiveValidator(validator *ethpb.Validator, epoch primitives.Epoch) bool

IsActiveValidator returns the boolean value on whether the validator is active or not.

Spec pseudocode definition: 

def is_active_validator(validator: Validator, epoch: Epoch) -> bool:
  """
  Check if ``validator`` is active.
  """
  return validator.activation_epoch <= epoch < validator.exit_epoch

func IsActiveValidatorUsingTrie 

func IsActiveValidatorUsingTrie(validator state.ReadOnlyValidator, epoch primitives.Epoch) bool

IsActiveValidatorUsingTrie checks if a read only validator is active.

func IsAggregated 

func IsAggregated(attestation *ethpb.Attestation) bool

IsAggregated returns true if the attestation is an aggregated attestation, false otherwise.

func IsAggregator 

func IsAggregator(committeeCount uint64, slotSig []byte) (bool, error)

IsAggregator returns true if the signature is from the input validator. The committee count is provided as an argument rather than imported implementation from spec. Having committee count as an argument allows cheaper computation at run time.

Spec pseudocode definition: 

def is_aggregator(state: BeaconState, slot: Slot, index: CommitteeIndex, slot_signature: BLSSignature) -> bool:
 committee = get_beacon_committee(state, slot, index)
 modulo = max(1, len(committee) // TARGET_AGGREGATORS_PER_COMMITTEE)
 return bytes_to_uint64(hash(slot_signature)[0:8]) % modulo == 0

func IsCurrentPeriodSyncCommittee 

func IsCurrentPeriodSyncCommittee(st state.BeaconState, valIdx primitives.ValidatorIndex) (bool, error)

IsCurrentPeriodSyncCommittee returns true if the input validator index belongs in the current period sync committee along with the sync committee root. 1. Checks if the public key exists in the sync committee cache 2. If 1 fails, checks if the public key exists in the input current sync committee object

func IsEligibleForActivation 

func IsEligibleForActivation(state state.ReadOnlyCheckpoint, validator *ethpb.Validator) bool

IsEligibleForActivation checks if the validator is eligible for activation.

Spec pseudocode definition: 

def is_eligible_for_activation(state: BeaconState, validator: Validator) -> bool:
  """
  Check if ``validator`` is eligible for activation.
  """
  return (
      # Placement in queue is finalized
      validator.activation_eligibility_epoch <= state.finalized_checkpoint.epoch
      # Has not yet been activated
      and validator.activation_epoch == FAR_FUTURE_EPOCH
  )

func IsEligibleForActivationQueue 

func IsEligibleForActivationQueue(validator *ethpb.Validator) bool

IsEligibleForActivationQueue checks if the validator is eligible to be placed into the activation queue.

Spec pseudocode definition: 

def is_eligible_for_activation_queue(validator: Validator) -> bool:
  """
  Check if ``validator`` is eligible to be placed into the activation queue.
  """
  return (
      validator.activation_eligibility_epoch == FAR_FUTURE_EPOCH
      and validator.effective_balance == MAX_EFFECTIVE_BALANCE
  )

func IsEligibleForActivationQueueUsingTrie 

func IsEligibleForActivationQueueUsingTrie(validator state.ReadOnlyValidator) bool

IsEligibleForActivationQueueUsingTrie checks if the read-only validator is eligible to be placed into the activation queue.

func IsEligibleForActivationUsingTrie 

func IsEligibleForActivationUsingTrie(state state.ReadOnlyCheckpoint, validator state.ReadOnlyValidator) bool

IsEligibleForActivationUsingTrie checks if the validator is eligible for activation.

func IsInInactivityLeak 

func IsInInactivityLeak(prevEpoch, finalizedEpoch primitives.Epoch) bool

IsInInactivityLeak returns true if the state is experiencing inactivity leak.

Spec code: def is_in_inactivity_leak(state: BeaconState) -> bool: 

return get_finality_delay(state) > MIN_EPOCHS_TO_INACTIVITY_PENALTY

func IsNextPeriodSyncCommittee 

func IsNextPeriodSyncCommittee(
	st state.BeaconState, valIdx primitives.ValidatorIndex,
) (bool, error)

IsNextPeriodSyncCommittee returns true if the input validator index belongs in the next period sync committee along with the sync period boundary root. 1. Checks if the public key exists in the sync committee cache 2. If 1 fails, checks if the public key exists in the input next sync committee object

func IsSlashableValidator 

func IsSlashableValidator(activationEpoch, withdrawableEpoch primitives.Epoch, slashed bool, epoch primitives.Epoch) bool

IsSlashableValidator returns the boolean value on whether the validator is slashable or not.

Spec pseudocode definition: 

def is_slashable_validator(validator: Validator, epoch: Epoch) -> bool:
"""
Check if ``validator`` is slashable.
"""
return (not validator.slashed) and (validator.activation_epoch <= epoch < validator.withdrawable_epoch)

func IsSlashableValidatorUsingTrie 

func IsSlashableValidatorUsingTrie(val state.ReadOnlyValidator, epoch primitives.Epoch) bool

IsSlashableValidatorUsingTrie checks if a read only validator is slashable.

func IsWithinWeakSubjectivityPeriod 

func IsWithinWeakSubjectivityPeriod(
	ctx context.Context, currentEpoch primitives.Epoch, wsState state.ReadOnlyBeaconState, wsStateRoot [fieldparams.RootLength]byte, wsEpoch primitives.Epoch, cfg *params.BeaconChainConfig) (bool, error)

IsWithinWeakSubjectivityPeriod verifies if a given weak subjectivity checkpoint is not stale i.e. the current node is so far beyond, that a given state and checkpoint are not for the latest weak subjectivity point. Provided checkpoint still can be used to double-check that node's block root at a given epoch matches that of the checkpoint.

Reference implementation: https://github.com/ethereum/consensus-specs/blob/master/specs/phase0/weak-subjectivity.md#checking-for-stale-weak-subjectivity-checkpoint

def is_within_weak_subjectivity_period(store: Store, ws_state: BeaconState, ws_checkpoint: Checkpoint) -> bool: 

# Clients may choose to validate the input state against the input Weak Subjectivity Checkpoint
assert ws_state.latest_block_header.state_root == ws_checkpoint.root
assert compute_epoch_at_slot(ws_state.slot) == ws_checkpoint.epoch

ws_period = compute_weak_subjectivity_period(ws_state)
ws_state_epoch = compute_epoch_at_slot(ws_state.slot)
current_epoch = compute_epoch_at_slot(get_current_slot(store))
return current_epoch <= ws_state_epoch + ws_period

func LastActivatedValidatorIndex 

func LastActivatedValidatorIndex(ctx context.Context, st state.ReadOnlyBeaconState) (primitives.ValidatorIndex, error)

LastActivatedValidatorIndex provides the last activated validator given a state

func LatestWeakSubjectivityEpoch 

func LatestWeakSubjectivityEpoch(ctx context.Context, st state.ReadOnlyBeaconState, cfg *params.BeaconChainConfig) (primitives.Epoch, error)

LatestWeakSubjectivityEpoch returns epoch of the most recent weak subjectivity checkpoint known to a node.

Within the weak subjectivity period, if two conflicting blocks are finalized, 1/3 - D (D := safety decay) of validators will get slashed. Therefore, it is safe to assume that any finalized checkpoint within that period is protected by this safety margin.

func NextPeriodSyncSubcommitteeIndices 

func NextPeriodSyncSubcommitteeIndices(
	st state.BeaconState, valIdx primitives.ValidatorIndex,
) ([]primitives.CommitteeIndex, error)

NextPeriodSyncSubcommitteeIndices returns the subcommittee indices of the next period sync committee for input validator.

func ParseWeakSubjectivityInputString 

func ParseWeakSubjectivityInputString(wsCheckpointString string) (*v1alpha1.Checkpoint, error)

ParseWeakSubjectivityInputString parses "blocks_root:epoch_number" string into a checkpoint.

func RandaoMix 

func RandaoMix(state state.ReadOnlyBeaconState, epoch primitives.Epoch) ([]byte, error)

RandaoMix returns the randao mix (xor'ed seed) of a given slot. It is used to shuffle validators.

Spec pseudocode definition: 

def get_randao_mix(state: BeaconState, epoch: Epoch) -> Bytes32:
 """
 Return the randao mix at a recent ``epoch``.
 """
 return state.randao_mixes[epoch % EPOCHS_PER_HISTORICAL_VECTOR]

func Seed 

func Seed(state state.ReadOnlyBeaconState, epoch primitives.Epoch, domain [bls.DomainByteLength]byte) ([32]byte, error)

Seed returns the randao seed used for shuffling of a given epoch.

Spec pseudocode definition: 

def get_seed(state: BeaconState, epoch: Epoch, domain_type: DomainType) -> Bytes32:
  """
  Return the seed at ``epoch``.
  """
  mix = get_randao_mix(state, Epoch(epoch + EPOCHS_PER_HISTORICAL_VECTOR - MIN_SEED_LOOKAHEAD - 1))  # Avoid underflow
  return hash(domain_type + uint_to_bytes(epoch) + mix)

func ShuffleList 

func ShuffleList(input []primitives.ValidatorIndex, seed [32]byte) ([]primitives.ValidatorIndex, error)

ShuffleList returns list of shuffled indexes in a pseudorandom permutation `p` of `0...list_size - 1` with “seed“ as entropy. We utilize 'swap or not' shuffling in this implementation; we are allocating the memory with the seed that stays constant between iterations instead of reallocating it each iteration as in the spec. This implementation is based on the original implementation from protolambda, https://github.com/protolambda/eth2-shuffle 

improvements:
 - seed is always the first 32 bytes of the hash input, we just copy it into the buffer one time.
 - add round byte to seed and hash that part of the buffer.
 - split up the for-loop in two:
  1. Handle the part from 0 (incl) to pivot (incl). This is mirrored around (pivot / 2).
  2. Handle the part from pivot (excl) to N (excl). This is mirrored around ((pivot / 2) + (size/2)).
 - hash source every 256 iterations.
 - change byteV every 8 iterations.
 - we start at the edges, and work back to the mirror point.
   this makes us process each pear exactly once (instead of unnecessarily twice, like in the spec).

func ShuffledIndex 

func ShuffledIndex(index primitives.ValidatorIndex, indexCount uint64, seed [32]byte) (primitives.ValidatorIndex, error)

ShuffledIndex returns `p(index)` in a pseudorandom permutation `p` of `0...list_size - 1` with “seed“ as entropy. We utilize 'swap or not' shuffling in this implementation; we are allocating the memory with the seed that stays constant between iterations instead of reallocating it each iteration as in the spec. This implementation is based on the original implementation from protolambda, https://github.com/protolambda/eth2-shuffle

func ShuffledIndices 

func ShuffledIndices(s state.ReadOnlyBeaconState, epoch primitives.Epoch) ([]primitives.ValidatorIndex, error)

ShuffledIndices uses input beacon state and returns the shuffled indices of the input epoch, the shuffled indices then can be used to break up into committees.

func SlotCommitteeCount 

func SlotCommitteeCount(activeValidatorCount uint64) uint64

SlotCommitteeCount returns the number of beacon committees of a slot. The active validator count is provided as an argument rather than an imported implementation from the spec definition. Having the active validator count as an argument allows for cheaper computation, instead of retrieving head state, one can retrieve the validator count.

Spec pseudocode definition: 

def get_committee_count_per_slot(state: BeaconState, epoch: Epoch) -> uint64:
 """
 Return the number of committees in each slot for the given ``epoch``.
 """
 return max(uint64(1), min(
     MAX_COMMITTEES_PER_SLOT,
     uint64(len(get_active_validator_indices(state, epoch))) // SLOTS_PER_EPOCH // TARGET_COMMITTEE_SIZE,
 ))

func SplitIndices 

func SplitIndices(l []uint64, n uint64) [][]uint64

SplitIndices splits a list into n pieces.

func StateRootAtSlot 

func StateRootAtSlot(state state.ReadOnlyBeaconState, slot primitives.Slot) ([]byte, error)

StateRootAtSlot returns the cached state root at that particular slot. If no state root has been cached it will return a zero-hash.

func TotalActiveBalance 

func TotalActiveBalance(s state.ReadOnlyBeaconState) (uint64, error)

TotalActiveBalance returns the total amount at stake in Gwei of active validators.

Spec pseudocode definition: 

def get_total_active_balance(state: BeaconState) -> Gwei:
 """
 Return the combined effective balance of the active validators.
 Note: ``get_total_balance`` returns ``EFFECTIVE_BALANCE_INCREMENT`` Gwei minimum to avoid divisions by zero.
 """
 return get_total_balance(state, set(get_active_validator_indices(state, get_current_epoch(state))))

func TotalBalance 

func TotalBalance(state state.ReadOnlyValidators, indices []primitives.ValidatorIndex) uint64

TotalBalance returns the total amount at stake in Gwei of input validators.

Spec pseudocode definition: 

def get_total_balance(state: BeaconState, indices: Set[ValidatorIndex]) -> Gwei:
 """
 Return the combined effective balance of the ``indices``.
 ``EFFECTIVE_BALANCE_INCREMENT`` Gwei minimum to avoid divisions by zero.
 Math safe up to ~10B ETH, afterwhich this overflows uint64.
 """
 return Gwei(max(EFFECTIVE_BALANCE_INCREMENT, sum([state.validators[index].effective_balance for index in indices])))

func UnShuffledIndex 

func UnShuffledIndex(index primitives.ValidatorIndex, indexCount uint64, seed [32]byte) (primitives.ValidatorIndex, error)

UnShuffledIndex returns the inverse of ShuffledIndex. This implementation is based on the original implementation from protolambda, https://github.com/protolambda/eth2-shuffle

func UnshuffleList 

func UnshuffleList(input []primitives.ValidatorIndex, seed [32]byte) ([]primitives.ValidatorIndex, error)

UnshuffleList un-shuffles the list by running backwards through the round count.

func UpdateCommitteeCache 

func UpdateCommitteeCache(ctx context.Context, state state.ReadOnlyBeaconState, e primitives.Epoch) error

UpdateCommitteeCache gets called at the beginning of every epoch to cache the committee shuffled indices list with committee index and epoch number. It caches the shuffled indices for the input epoch.

func UpdateGenesisEth1Data 

func UpdateGenesisEth1Data(state state.BeaconState, deposits []*ethpb.Deposit, eth1Data *ethpb.Eth1Data) (state.BeaconState, error)

UpdateGenesisEth1Data updates eth1 data for genesis state.

func UpdateProposerIndicesInCache 

func UpdateProposerIndicesInCache(ctx context.Context, state state.ReadOnlyBeaconState, epoch primitives.Epoch) error

UpdateProposerIndicesInCache updates proposer indices entry of the committee cache. Input state is used to retrieve active validator indices. Input epoch is the epoch to retrieve proposer indices for.

func UpdateSyncCommitteeCache 

func UpdateSyncCommitteeCache(st state.BeaconState) error

UpdateSyncCommitteeCache updates sync committee cache. It uses `state`'s latest block header root as key. To avoid misuse, it disallows block header with state root zeroed out.

func ValidateAttestationTime 

func ValidateAttestationTime(attSlot primitives.Slot, genesisTime time.Time, clockDisparity time.Duration) error

ValidateAttestationTime Validates that the incoming attestation is in the desired time range. An attestation is valid only if received within the last ATTESTATION_PROPAGATION_SLOT_RANGE slots.

Example: 

ATTESTATION_PROPAGATION_SLOT_RANGE = 5
clockDisparity = 24 seconds
current_slot = 100
invalid_attestation_slot = 92
invalid_attestation_slot = 103
valid_attestation_slot = 98
valid_attestation_slot = 101

In the attestation must be within the range of 95 to 102 in the example above.

func ValidateNilAttestation 

func ValidateNilAttestation(attestation *ethpb.Attestation) error

ValidateNilAttestation checks if any composite field of input attestation is nil. Access to these nil fields will result in run time panic, it is recommended to run these checks as first line of defense.

func ValidateSlotTargetEpoch 

func ValidateSlotTargetEpoch(data *ethpb.AttestationData) error

ValidateSlotTargetEpoch checks if attestation data's epoch matches target checkpoint's epoch. It is recommended to run `ValidateNilAttestation` first to ensure `data.Target` can't be nil.

func ValidatorChurnLimit 

func ValidatorChurnLimit(activeValidatorCount uint64) (uint64, error)

ValidatorChurnLimit returns the number of validators that are allowed to enter and exit validator pool for an epoch.

Spec pseudocode definition: 

def get_validator_churn_limit(state: BeaconState) -> uint64:
 """
 Return the validator churn limit for the current epoch.
 """
 active_validator_indices = get_active_validator_indices(state, get_current_epoch(state))
 return max(MIN_PER_EPOCH_CHURN_LIMIT, uint64(len(active_validator_indices)) // CHURN_LIMIT_QUOTIENT)

func VerifyAttestationBitfieldLengths 

func VerifyAttestationBitfieldLengths(ctx context.Context, state state.ReadOnlyBeaconState, att *ethpb.Attestation) error

VerifyAttestationBitfieldLengths verifies that an attestations aggregation bitfields is a valid length matching the size of the committee.

func VerifyBitfieldLength 

func VerifyBitfieldLength(bf bitfield.Bitfield, committeeSize uint64) error

VerifyBitfieldLength verifies that a bitfield length matches the given committee size.

func VerifyCheckpointEpoch 

func VerifyCheckpointEpoch(c *ethpb.Checkpoint, genesis time.Time) bool

VerifyCheckpointEpoch is within current epoch and previous epoch with respect to current time. Returns true if it's within, false if it's not.

Types

type CommitteeAssignmentContainer 

type CommitteeAssignmentContainer struct {
	Committee      []primitives.ValidatorIndex
	AttesterSlot   primitives.Slot
	CommitteeIndex primitives.CommitteeIndex
}

CommitteeAssignmentContainer represents a committee list, committee index, and to be attested slot for a given epoch.

Source Files

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