-
Notifications
You must be signed in to change notification settings - Fork 954
/
randao.go
49 lines (43 loc) · 1.78 KB
/
randao.go
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
package helpers
import (
stateTrie "github.com/prysmaticlabs/prysm/beacon-chain/state"
"github.com/prysmaticlabs/prysm/shared/bls"
"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 *stateTrie.BeaconState, epoch uint64, domain [bls.DomainByteLength]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, err := RandaoMix(state, lookAheadEpoch)
if err != nil {
return [32]byte{}, err
}
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 *stateTrie.BeaconState, epoch uint64) ([]byte, error) {
return state.RandaoMixAtIndex(epoch % params.BeaconConfig().EpochsPerHistoricalVector)
}