prysm-pulse/beacon-chain/core/helpers/randao.go
Ivan Martinez b30a7d1e19 Fix typos and inconsistencies (#4453)
* Fix typos and inconsistencies

* igoimports

* Gazelle
2020-01-07 20:36:55 -06:00

50 lines
1.8 KiB
Go

package helpers
import (
pb "github.com/prysmaticlabs/prysm/proto/beacon/p2p/v1"
"github.com/prysmaticlabs/prysm/shared/bytesutil"
"github.com/prysmaticlabs/prysm/shared/hashutil"
"github.com/prysmaticlabs/prysm/shared/params"
)
// 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) -> Hash:
// """
// 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 + int_to_bytes(epoch, length=8) + mix)
func Seed(state *pb.BeaconState, epoch uint64, domain []byte) ([32]byte, error) {
// See https://github.com/ethereum/eth2.0-specs/pull/1296 for
// rationale on why offset has to look down by 1.
lookAheadEpoch := epoch + params.BeaconConfig().EpochsPerHistoricalVector -
params.BeaconConfig().MinSeedLookahead - 1
randaoMix := RandaoMix(state, lookAheadEpoch)
seed := append(domain, bytesutil.Bytes8(epoch)...)
seed = append(seed, randaoMix...)
seed32 := hashutil.Hash(seed)
return seed32, nil
}
// 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) -> Hash:
// """
// Return the randao mix at a recent ``epoch``.
// """
// return state.randao_mixes[epoch % EPOCHS_PER_HISTORICAL_VECTOR]
func RandaoMix(state *pb.BeaconState, epoch uint64) []byte {
newMixLength := len(state.RandaoMixes[epoch%params.BeaconConfig().EpochsPerHistoricalVector])
newMix := make([]byte, newMixLength)
copy(newMix, state.RandaoMixes[epoch%params.BeaconConfig().EpochsPerHistoricalVector])
return newMix
}