204 lines
8.5 KiB
Nim
204 lines
8.5 KiB
Nim
# beacon_chain
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# Copyright (c) 2018-2020 Status Research & Development GmbH
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# Licensed and distributed under either of
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# * MIT license (license terms in the root directory or at https://opensource.org/licenses/MIT).
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# * Apache v2 license (license terms in the root directory or at https://www.apache.org/licenses/LICENSE-2.0).
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# at your option. This file may not be copied, modified, or distributed except according to those terms.
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import
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std/[algorithm, sequtils, sets],
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chronicles,
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../spec/[
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crypto, datatypes, digest, helpers, presets, signatures,
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validator],
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../extras,
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./block_pools_types, ./chain_dag
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# Spec functions implemented based on cached values instead of the full state
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func count_active_validators*(epochInfo: EpochRef): uint64 =
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epochInfo.shuffled_active_validator_indices.lenu64
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# https://github.com/ethereum/eth2.0-specs/blob/v1.0.0-rc.0/specs/phase0/beacon-chain.md#get_committee_count_per_slot
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func get_committee_count_per_slot*(epochInfo: EpochRef): uint64 =
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get_committee_count_per_slot(count_active_validators(epochInfo))
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# https://github.com/ethereum/eth2.0-specs/blob/v1.0.0-rc.0/specs/phase0/beacon-chain.md#get_beacon_committee
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iterator get_beacon_committee*(
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epochRef: EpochRef, slot: Slot, index: CommitteeIndex): ValidatorIndex =
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# Return the beacon committee at ``slot`` for ``index``.
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let
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committees_per_slot = get_committee_count_per_slot(epochRef)
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for idx in compute_committee(
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epochRef.shuffled_active_validator_indices,
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(slot mod SLOTS_PER_EPOCH) * committees_per_slot +
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index.uint64,
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committees_per_slot * SLOTS_PER_EPOCH
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): yield idx
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# https://github.com/ethereum/eth2.0-specs/blob/v1.0.0-rc.0/specs/phase0/beacon-chain.md#get_beacon_committee
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func get_beacon_committee*(
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epochRef: EpochRef, slot: Slot, index: CommitteeIndex): seq[ValidatorIndex] =
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# Return the beacon committee at ``slot`` for ``index``.
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let
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committees_per_slot = get_committee_count_per_slot(epochRef)
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compute_committee(
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epochRef.shuffled_active_validator_indices,
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(slot mod SLOTS_PER_EPOCH) * committees_per_slot +
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index.uint64,
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committees_per_slot * SLOTS_PER_EPOCH
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)
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# https://github.com/ethereum/eth2.0-specs/blob/v1.0.0-rc.0/specs/phase0/beacon-chain.md#get_beacon_committee
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func get_beacon_committee_len*(
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epochRef: EpochRef, slot: Slot, index: CommitteeIndex): uint64 =
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# Return the number of members in the beacon committee at ``slot`` for ``index``.
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let
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committees_per_slot = get_committee_count_per_slot(epochRef)
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compute_committee_len(
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count_active_validators(epochRef),
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(slot mod SLOTS_PER_EPOCH) * committees_per_slot +
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index.uint64,
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committees_per_slot * SLOTS_PER_EPOCH
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)
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# https://github.com/ethereum/eth2.0-specs/blob/v1.0.0-rc.0/specs/phase0/beacon-chain.md#get_attesting_indices
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iterator get_attesting_indices*(epochRef: EpochRef,
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data: AttestationData,
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bits: CommitteeValidatorsBits):
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ValidatorIndex =
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if bits.lenu64 != get_beacon_committee_len(epochRef, data.slot, data.index.CommitteeIndex):
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trace "get_attesting_indices: inconsistent aggregation and committee length"
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else:
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var i = 0
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for index in get_beacon_committee(epochRef, data.slot, data.index.CommitteeIndex):
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if bits[i]:
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yield index
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inc i
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# https://github.com/ethereum/eth2.0-specs/blob/v1.0.0-rc.0/specs/phase0/beacon-chain.md#get_attesting_indices
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func get_attesting_indices*(epochRef: EpochRef,
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data: AttestationData,
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bits: CommitteeValidatorsBits):
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HashSet[ValidatorIndex] =
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for idx in get_attesting_indices(epochRef, data, bits):
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result.incl(idx)
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# https://github.com/ethereum/eth2.0-specs/blob/v1.0.0-rc.0/specs/phase0/beacon-chain.md#get_indexed_attestation
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func get_indexed_attestation*(epochRef: EpochRef, attestation: Attestation): IndexedAttestation =
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# Return the indexed attestation corresponding to ``attestation``.
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let
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attesting_indices =
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get_attesting_indices(
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epochRef, attestation.data, attestation.aggregation_bits)
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IndexedAttestation(
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attesting_indices:
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List[uint64, Limit MAX_VALIDATORS_PER_COMMITTEE].init(
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sorted(mapIt(attesting_indices, it.uint64), system.cmp)),
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data: attestation.data,
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signature: attestation.signature
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)
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# https://github.com/ethereum/eth2.0-specs/blob/v1.0.0-rc.0/specs/phase0/validator.md#aggregation-selection
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func is_aggregator*(epochRef: EpochRef, slot: Slot, index: CommitteeIndex,
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slot_signature: ValidatorSig): bool =
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let
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committee_len = get_beacon_committee_len(epochRef, slot, index)
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modulo = max(1'u64, committee_len div TARGET_AGGREGATORS_PER_COMMITTEE)
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bytes_to_uint64(eth2digest(
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slot_signature.toRaw()).data.toOpenArray(0, 7)) mod modulo == 0
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# https://github.com/ethereum/eth2.0-specs/blob/v1.0.0-rc.0/specs/phase0/beacon-chain.md#is_valid_indexed_attestation
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proc is_valid_indexed_attestation*(
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fork: Fork, genesis_validators_root: Eth2Digest,
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epochRef: EpochRef, indexed_attestation: SomeIndexedAttestation,
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flags: UpdateFlags): Result[void, cstring] =
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# Check if ``indexed_attestation`` is not empty, has sorted and unique
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# indices and has a valid aggregate signature.
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template is_sorted_and_unique(s: untyped): bool =
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var res = true
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for i in 1 ..< s.len:
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if s[i - 1].uint64 >= s[i].uint64:
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res = false
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break
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res
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if len(indexed_attestation.attesting_indices) == 0:
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return err("indexed_attestation: no attesting indices")
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# Not from spec, but this function gets used in front-line roles, not just
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# behind firewall.
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let num_validators = epochRef.validator_keys.lenu64
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if anyIt(indexed_attestation.attesting_indices, it >= num_validators):
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return err("indexed attestation: not all indices valid validators")
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if not is_sorted_and_unique(indexed_attestation.attesting_indices):
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return err("indexed attestation: indices not sorted and unique")
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# Verify aggregate signature
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if skipBLSValidation notin flags:
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# TODO: fuse loops with blsFastAggregateVerify
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let pubkeys = mapIt(
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indexed_attestation.attesting_indices, epochRef.validator_keys[it])
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if not verify_attestation_signature(
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fork, genesis_validators_root, indexed_attestation.data,
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pubkeys, indexed_attestation.signature):
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return err("indexed attestation: signature verification failure")
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ok()
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# https://github.com/ethereum/eth2.0-specs/blob/v1.0.0-rc.0/specs/phase0/beacon-chain.md#is_valid_indexed_attestation
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proc is_valid_indexed_attestation*(
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fork: Fork, genesis_validators_root: Eth2Digest,
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epochRef: EpochRef, attesting_indices: HashSet[ValidatorIndex],
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attestation: SomeAttestation, flags: UpdateFlags): Result[void, cstring] =
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# This is a variation on `is_valid_indexed_attestation` that works directly
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# with an attestation instead of first constructing an `IndexedAttestation`
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# and then validating it - for the purpose of validating the signature, the
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# order doesn't matter and we can proceed straight to validating the
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# signature instead
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if attesting_indices.len == 0:
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return err("indexed_attestation: no attesting indices")
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# Verify aggregate signature
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if skipBLSValidation notin flags:
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# TODO: fuse loops with blsFastAggregateVerify
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let pubkeys = mapIt(
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attesting_indices, epochRef.validator_keys[it])
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if not verify_attestation_signature(
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fork, genesis_validators_root, attestation.data,
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pubkeys, attestation.signature):
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return err("indexed attestation: signature verification failure")
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ok()
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func makeAttestationData*(
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epochRef: EpochRef, bs: BlockSlot,
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committee_index: CommitteeIndex): AttestationData =
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## Create an attestation / vote for the block `bs` using the
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## data in `epochRef` to fill in the rest of the fields.
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## `epochRef` is the epoch information corresponding to the `bs` advanced to
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## the slot we're attesting to.
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let
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slot = bs.slot
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current_epoch = slot.compute_epoch_at_slot()
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epoch_boundary_slot = compute_start_slot_at_epoch(current_epoch)
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epoch_boundary_block = bs.blck.atSlot(epoch_boundary_slot)
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doAssert current_epoch == epochRef.epoch
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# https://github.com/ethereum/eth2.0-specs/blob/v1.0.0-rc.0/specs/phase0/validator.md#attestation-data
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AttestationData(
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slot: slot,
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index: committee_index.uint64,
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beacon_block_root: bs.blck.root,
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source: epochRef.current_justified_checkpoint,
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target: Checkpoint(
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epoch: current_epoch,
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root: epoch_boundary_block.blck.root
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)
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)
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