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https://gitlab.com/pulsechaincom/prysm-pulse.git
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51 lines
1.9 KiB
Go
51 lines
1.9 KiB
Go
package helpers
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import (
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types "github.com/prysmaticlabs/eth2-types"
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iface "github.com/prysmaticlabs/prysm/beacon-chain/state/interface"
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"github.com/prysmaticlabs/prysm/shared/bls"
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"github.com/prysmaticlabs/prysm/shared/bytesutil"
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"github.com/prysmaticlabs/prysm/shared/hashutil"
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"github.com/prysmaticlabs/prysm/shared/params"
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)
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// Seed returns the randao seed used for shuffling of a given epoch.
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//
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// Spec pseudocode definition:
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// def get_seed(state: BeaconState, epoch: Epoch, domain_type: DomainType) -> Hash:
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// """
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// Return the seed at ``epoch``.
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// """
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// mix = get_randao_mix(state, Epoch(epoch + EPOCHS_PER_HISTORICAL_VECTOR - MIN_SEED_LOOKAHEAD - 1)) # Avoid underflow
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// return hash(domain_type + int_to_bytes(epoch, length=8) + mix)
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func Seed(state iface.ReadOnlyBeaconState, epoch types.Epoch, domain [bls.DomainByteLength]byte) ([32]byte, error) {
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// See https://github.com/ethereum/eth2.0-specs/pull/1296 for
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// rationale on why offset has to look down by 1.
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lookAheadEpoch := epoch + params.BeaconConfig().EpochsPerHistoricalVector -
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params.BeaconConfig().MinSeedLookahead - 1
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randaoMix, err := RandaoMix(state, lookAheadEpoch)
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if err != nil {
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return [32]byte{}, err
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}
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seed := append(domain[:], bytesutil.Bytes8(uint64(epoch))...)
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seed = append(seed, randaoMix...)
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seed32 := hashutil.Hash(seed)
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return seed32, nil
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}
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// RandaoMix returns the randao mix (xor'ed seed)
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// of a given slot. It is used to shuffle validators.
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//
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// Spec pseudocode definition:
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// def get_randao_mix(state: BeaconState, epoch: Epoch) -> Hash:
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// """
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// Return the randao mix at a recent ``epoch``.
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// """
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// return state.randao_mixes[epoch % EPOCHS_PER_HISTORICAL_VECTOR]
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func RandaoMix(state iface.ReadOnlyBeaconState, epoch types.Epoch) ([]byte, error) {
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return state.RandaoMixAtIndex(uint64(epoch % params.BeaconConfig().EpochsPerHistoricalVector))
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}
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