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nimbus-eth2/beacon_chain/spec/beaconstate.nim

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# beacon_chain
# Copyright (c) 2018 Status Research & Development GmbH
# Licensed and distributed under either of
# * MIT license (license terms in the root directory or at http://opensource.org/licenses/MIT).
# * Apache v2 license (license terms in the root directory or at http://www.apache.org/licenses/LICENSE-2.0).
# at your option. This file may not be copied, modified, or distributed except according to those terms.
import
chronicles, math, options, sequtils,
../extras, ../ssz,
./crypto, ./datatypes, ./digest, ./helpers, ./validator
func get_effective_balance*(state: BeaconState, index: Uint24): uint64 =
# Validators collect rewards which increases their balance but not their
# influence. Validators may also lose balance if they fail to do their duty
# in which case their influence decreases. Once they drop below a certain
# balance, they're removed from the validator registry.
min(state.validator_balances[index], MAX_DEPOSIT * GWEI_PER_ETH)
func sum_effective_balances*(
state: BeaconState, validator_indices: openArray[Uint24]): uint64 =
# TODO spec - add as helper? Used pretty often
for index in validator_indices:
result += get_effective_balance(state, index)
func validate_proof_of_possession(state: BeaconState,
pubkey: ValidatorPubKey,
proof_of_possession: ValidatorSig,
withdrawal_credentials: Eth2Digest,
randao_commitment: Eth2Digest): bool =
let proof_of_possession_data = DepositInput(
pubkey: pubkey,
withdrawal_credentials: withdrawal_credentials,
randao_commitment: randao_commitment
)
bls_verify(
pubkey,
hash_tree_root_final(proof_of_possession_data).data,
proof_of_possession,
get_domain(
state.fork_data,
state.slot,
DOMAIN_DEPOSIT,
)
)
func process_deposit(state: var BeaconState,
pubkey: ValidatorPubKey,
deposit: uint64,
proof_of_possession: ValidatorSig,
withdrawal_credentials: Eth2Digest,
randao_commitment: Eth2Digest,
custody_commitment: Eth2Digest) : Uint24 =
## Process a deposit from Ethereum 1.0.
if false:
# TODO return error; currently, just fails if ever called
# but hadn't been set up to run at all
doAssert validate_proof_of_possession(
state, pubkey, proof_of_possession, withdrawal_credentials,
randao_commitment)
let validator_pubkeys = state.validator_registry.mapIt(it.pubkey)
if pubkey notin validator_pubkeys:
# Add new validator
let validator = Validator(
status: UNUSED,
pubkey: pubkey,
withdrawal_credentials: withdrawal_credentials,
randao_commitment: randao_commitment,
randao_layers: 0,
activation_slot: FAR_FUTURE_SLOT,
exit_slot: FAR_FUTURE_SLOT,
withdrawal_slot: FAR_FUTURE_SLOT,
penalized_slot: FAR_FUTURE_SLOT,
exit_count: 0,
status_flags: 0,
custody_commitment: custody_commitment,
latest_custody_reseed_slot: GENESIS_SLOT,
penultimate_custody_reseed_slot: GENESIS_SLOT
)
let index = min_empty_validator_index(
state.validator_registry, state.validator_balances, state.slot)
if index.isNone():
state.validator_registry.add(validator)
state.validator_balances.add(deposit)
(len(state.validator_registry) - 1).Uint24
else:
state.validator_registry[index.get()] = validator
state.validator_balances[index.get()] = deposit
index.get().Uint24
else:
# Increase balance by deposit amount
let index = validator_pubkeys.find(pubkey)
let validator = addr state.validator_registry[index]
assert state.validator_registry[index].withdrawal_credentials ==
withdrawal_credentials
state.validator_balances[index] += deposit
index.Uint24
func activate_validator(state: var BeaconState,
index: Uint24,
genesis: bool) =
## Activate the validator with the given ``index``.
let validator = addr state.validator_registry[index]
validator.status = ACTIVE
validator.activation_slot = if genesis: GENESIS_SLOT else: state.slot + ENTRY_EXIT_DELAY
state.validator_registry_delta_chain_tip =
get_new_validator_registry_delta_chain_tip(
state.validator_registry_delta_chain_tip,
index,
validator.pubkey,
validator.activation_slot,
ACTIVATION,
)
func initiate_validator_exit(state: var BeaconState,
index: Uint24) =
## Initiate exit for the validator with the given ``index``.
var validator = state.validator_registry[index]
validator.status_flags = validator.status_flags or INITIATED_EXIT
state.validator_registry[index] = validator
func exit_validator*(state: var BeaconState,
index: Uint24) =
## Exit the validator with the given ``index``.
let validator = addr state.validator_registry[index]
# The following updates only occur if not previous exited
if validator.exit_slot <= state.slot + ENTRY_EXIT_DELAY:
return
validator.exit_slot = state.slot + ENTRY_EXIT_DELAY
# The following updates only occur if not previous exited
state.validator_registry_exit_count += 1
validator.exit_count = state.validator_registry_exit_count
state.validator_registry_delta_chain_tip =
get_new_validator_registry_delta_chain_tip(
state.validator_registry_delta_chain_tip,
index,
validator.pubkey,
validator.exit_slot,
ValidatorSetDeltaFlags.EXIT
)
func process_penalties_and_exits_eligible(state: BeaconState, index: int): bool =
let validator = state.validator_registry[index]
if validator.penalized_slot <= state.slot:
# strangely uppercase variable-ish name
let PENALIZED_WITHDRAWAL_TIME = (LATEST_PENALIZED_EXIT_LENGTH * EPOCH_LENGTH div 2).uint64
return state.slot >= validator.penalized_slot + PENALIZED_WITHDRAWAL_TIME
else:
return state.slot >= validator.exit_slot + MIN_VALIDATOR_WITHDRAWAL_TIME
func process_penalties_and_exits(state: var BeaconState) =
# The active validators
let active_validator_indices = get_active_validator_indices(state.validator_registry, state.slot)
# The total effective balance of active validators
var total_balance : uint64 = 0
for i in active_validator_indices:
total_balance += get_effective_balance(state, i)
for index, validator in state.validator_registry:
if (state.slot div EPOCH_LENGTH) == (validator.penalized_slot div EPOCH_LENGTH) + LATEST_PENALIZED_EXIT_LENGTH div 2:
let
e = ((state.slot div EPOCH_LENGTH) mod LATEST_PENALIZED_EXIT_LENGTH).int
total_at_start = state.latest_penalized_exit_balances[(e + 1) mod LATEST_PENALIZED_EXIT_LENGTH]
total_at_end = state.latest_penalized_exit_balances[e]
total_penalties = total_at_end - total_at_start
penalty = get_effective_balance(state, index.Uint24) * min(total_penalties * 3, total_balance) div total_balance
state.validator_balances[index] -= penalty
## 'state' is of type <var BeaconState> which cannot be captured as it
## would violate memory safety, when using nested function approach in
## spec directly. That said, the spec approach evidently is not meant,
## based on its abundant and pointless memory copies, for production.
var eligible_indices : seq[Uint24] = @[]
for i in 0 ..< len(state.validator_registry):
eligible_indices.add i.Uint24
## TODO figure out that memory safety issue, which would come up again when
## sorting, and then actually do withdrawals
func get_initial_beacon_state*(
initial_validator_deposits: openArray[Deposit],
genesis_time: uint64,
latest_eth1_data: Eth1Data,
flags: UpdateFlags = {}): BeaconState =
## BeaconState constructor
##
## Before the beacon chain starts, validators will register in the Eth1 chain
## and deposit ETH. When enough many validators have registered, a
## `ChainStart` log will be emitted and the beacon chain can start beaconing.
##
## Because the state root hash is part of the genesis block, the beacon state
## must be calculated before creating the genesis block.
# Induct validators
# Not in spec: the system doesn't work unless there are at least EPOCH_LENGTH
# validators - there needs to be at least one member in each committee -
# good to know for testing, though arguably the system is not that useful at
# at that point :)
assert initial_validator_deposits.len >= EPOCH_LENGTH
var state = BeaconState(
# Misc
slot: GENESIS_SLOT,
genesis_time: genesis_time,
fork_data: ForkData(
pre_fork_version: GENESIS_FORK_VERSION,
post_fork_version: GENESIS_FORK_VERSION,
fork_slot: GENESIS_SLOT,
),
validator_registry_latest_change_slot: GENESIS_SLOT,
validator_registry_exit_count: 0,
validator_registry_delta_chain_tip: ZERO_HASH,
# Randomness and committees
previous_epoch_start_shard: GENESIS_START_SHARD,
current_epoch_start_shard: GENESIS_START_SHARD,
previous_epoch_calculation_slot: GENESIS_SLOT,
current_epoch_calculation_slot: GENESIS_SLOT,
previous_epoch_randao_mix: ZERO_HASH,
current_epoch_randao_mix: ZERO_HASH,
# Finality
previous_justified_slot: GENESIS_SLOT,
justified_slot: GENESIS_SLOT,
justification_bitfield: 0,
finalized_slot: GENESIS_SLOT,
# Deposit root
latest_eth1_data: latest_eth1_data,
)
# Process initial deposits
for deposit in initial_validator_deposits:
let validator_index = process_deposit(
state,
deposit.deposit_data.deposit_input.pubkey,
deposit.deposit_data.amount,
deposit.deposit_data.deposit_input.proof_of_possession,
deposit.deposit_data.deposit_input.withdrawal_credentials,
deposit.deposit_data.deposit_input.randao_commitment,
deposit.deposit_data.deposit_input.custody_commitment,
)
if state.validator_balances[validator_index] >= MAX_DEPOSIT:
activate_validator(state, validator_index, true)
# Process initial activations
#for validator_index in 0 ..< state.validator_registry.len:
# let vi = validator_index.Uint24
# if get_effective_balance(state, vi) > MAX_DEPOSIT * GWEI_PER_ETH:
# activate_validator(state, vi, true)
# set initial committee shuffling
let
initial_shuffling =
get_shuffling(Eth2Digest(), state.validator_registry, 0, state.slot)
# initial_shuffling + initial_shuffling in spec, but more ugly
for i, n in initial_shuffling:
state.shard_committees_at_slots[i] = n
state.shard_committees_at_slots[EPOCH_LENGTH + i] = n
# set initial persistent shuffling
let active_validator_indices =
get_active_validator_indices(state.validator_registry, state.slot)
state.persistent_committees = split(shuffle(
active_validator_indices, ZERO_HASH), SHARD_COUNT)
state
func get_block_root*(state: BeaconState,
slot: uint64): Eth2Digest =
doAssert state.slot <= slot + LATEST_BLOCK_ROOTS_LENGTH
doAssert slot < state.slot
state.latest_block_roots[slot mod LATEST_BLOCK_ROOTS_LENGTH]
func get_randao_mix*(state: BeaconState,
slot: uint64): Eth2Digest =
## Returns the randao mix at a recent ``slot``.
assert state.slot < slot + LATEST_RANDAO_MIXES_LENGTH
assert slot <= state.slot
state.latest_randao_mixes[slot mod LATEST_RANDAO_MIXES_LENGTH]
func get_attestation_participants*(state: BeaconState,
attestation_data: AttestationData,
participation_bitfield: seq[byte]): seq[Uint24] =
## Attestation participants in the attestation data are called out in a
## bit field that corresponds to the committee of the shard at the time - this
## function converts it to list of indices in to BeaconState.validators
## Returns empty list if the shard is not found
# TODO Linear search through shard list? borderline ok, it's a small list
# TODO bitfield type needed, once bit order settles down
# TODO iterator candidate
let
sncs_for_slot = get_shard_committees_at_slot(
state, attestation_data.slot)
for snc in sncs_for_slot:
if snc.shard != attestation_data.shard:
continue
# TODO investigate functional library / approach to help avoid loop bugs
assert len(participation_bitfield) == ceil_div8(len(snc.committee))
for i, vindex in snc.committee:
if bitIsSet(participation_bitfield, i):
result.add(vindex)
return # found the shard, we're done
func process_ejections*(state: var BeaconState) =
## Iterate through the validator registry
## and eject active validators with balance below ``EJECTION_BALANCE``.
for index in get_active_validator_indices(state.validator_registry, state.slot):
if state.validator_balances[index] < EJECTION_BALANCE:
exit_validator(state, index)
func update_validator_registry*(state: var BeaconState) =
let
active_validator_indices =
get_active_validator_indices(state.validator_registry, state.slot)
# The total effective balance of active validators
total_balance = sum_effective_balances(state, active_validator_indices)
# The maximum balance churn in Gwei (for deposits and exits separately)
max_balance_churn = max(
MAX_DEPOSIT * GWEI_PER_ETH,
total_balance div (2 * MAX_BALANCE_CHURN_QUOTIENT)
)
# Activate validators within the allowable balance churn
var balance_churn = 0'u64
for index, validator in state.validator_registry:
if validator.activation_slot > state.slot + ENTRY_EXIT_DELAY and
state.validator_balances[index] >= MAX_DEPOSIT * GWEI_PER_ETH:
# Check the balance churn would be within the allowance
balance_churn += get_effective_balance(state, index.Uint24)
if balance_churn > max_balance_churn:
break
# Activate validator
activate_validator(state, index.Uint24, false)
# Exit validators within the allowable balance churn
balance_churn = 0
for index, validator in state.validator_registry:
if (validator.exit_slot > state.slot + ENTRY_EXIT_DELAY) and
((validator.status_flags and INITIATED_EXIT) == INITIATED_EXIT):
# Check the balance churn would be within the allowance
balance_churn += get_effective_balance(state, index.Uint24)
if balance_churn > max_balance_churn:
break
# Exit validator
exit_validator(state, index.Uint24)
# Perform additional updates
state.previous_epoch_calculation_slot = state.current_epoch_calculation_slot
state.previous_epoch_start_shard = state.current_epoch_start_shard
state.previous_epoch_randao_mix = state.current_epoch_randao_mix
state.current_epoch_calculation_slot = state.slot
state.current_epoch_start_shard = (state.current_epoch_start_shard + get_current_epoch_committee_count_per_slot(state) * EPOCH_LENGTH) mod SHARD_COUNT
state.current_epoch_randao_mix = get_randao_mix(state, state.current_epoch_calculation_slot - SEED_LOOKAHEAD)
# TODO "If a validator registry update does not happen do the following: ..."
process_penalties_and_exits(state)
proc checkAttestation*(
state: BeaconState, attestation: Attestation, flags: UpdateFlags): bool =
## Check that an attestation follows the rules of being included in the state
## at the current slot. When acting as a proposer, the same rules need to
## be followed!
##
## https://github.com/ethereum/eth2.0-specs/blob/master/specs/core/0_beacon-chain.md#attestations-1
if not (attestation.data.slot + MIN_ATTESTATION_INCLUSION_DELAY <= state.slot):
warn("Attestation too new",
attestation_slot = attestation.data.slot, state_slot = state.slot)
return
if not (attestation.data.slot + EPOCH_LENGTH >= state.slot):
warn("Attestation too old",
attestation_slot = attestation.data.slot, state_slot = state.slot)
return
let expected_justified_slot =
if attestation.data.slot >= state.slot - (state.slot mod EPOCH_LENGTH):
state.justified_slot
else:
state.previous_justified_slot
if not (attestation.data.justified_slot == expected_justified_slot):
warn("Unexpected justified slot",
attestation_justified_slot = attestation.data.justified_slot,
expected_justified_slot)
return
let expected_justified_block_root =
get_block_root(state, attestation.data.justified_slot)
if not (attestation.data.justified_block_root == expected_justified_block_root):
warn("Unexpected justified block root",
attestation_justified_block_root = attestation.data.justified_block_root,
expected_justified_block_root)
return
if not (state.latest_crosslinks[attestation.data.shard].shard_block_root in [
attestation.data.latest_crosslink_root,
attestation.data.shard_block_root]):
warn("Unexpected crosslink shard_block_root")
return
let
participants = get_attestation_participants(
state, attestation.data, attestation.participation_bitfield)
group_public_key = bls_aggregate_pubkeys(
participants.mapIt(state.validator_registry[it].pubkey))
if skipValidation notin flags:
# Verify that aggregate_signature verifies using the group pubkey.
let msg = hash_tree_root_final(attestation.data)
if not bls_verify(
group_public_key, @(msg.data) & @[0'u8], attestation.aggregate_signature,
get_domain(state.fork_data, attestation.data.slot, DOMAIN_ATTESTATION)
):
warn("Invalid attestation group signature")
return
# To be removed in Phase1:
if attestation.data.shard_block_root != ZERO_HASH:
warn("Invalid shard block root")
return
true
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