ceremonyclient/nekryptology/pkg/dkg/gennaro/round2.go

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2023-07-05 05:32:28 +00:00
//
// Copyright Coinbase, Inc. All Rights Reserved.
//
// SPDX-License-Identifier: Apache-2.0
//
package gennaro
import (
"fmt"
"source.quilibrium.com/quilibrium/monorepo/nekryptology/internal"
v1 "source.quilibrium.com/quilibrium/monorepo/nekryptology/pkg/sharing/v1"
)
type Round2Bcast = []*v1.ShareVerifier
// Round2 computes the second round for Gennaro DKG
// Algorithm 3 - Gennaro DKG Round 2
// bcast contains all Round1 broadcast from other participants to this participant
// p2p contains all Round1 P2P send message from other participants to this participant
func (dp *Participant) Round2(bcast map[uint32]Round1Bcast, p2p map[uint32]*Round1P2PSendPacket) (Round2Bcast, error) {
// Check participant is not empty
if dp == nil || dp.curve == nil {
return nil, internal.ErrNilArguments
}
// Check participant has the correct dkg round number
if dp.round != 2 {
return nil, internal.ErrInvalidRound
}
// Check the input is valid
if bcast == nil || p2p == nil || len(bcast) == 0 || len(p2p) == 0 {
return nil, internal.ErrNilArguments
}
// 1. set sk = x_{ii}
sk := dp.pedersenResult.SecretShares[dp.id-1].Value
// 2. for j in 1,...,n
for id := range bcast {
// 3. if i = j continue
if id == dp.id {
continue
}
// Ensure a valid p2p entry exists
if p2p[id] == nil {
return nil, fmt.Errorf("missing p2p packet for id=%v", id)
}
// 4. If PedersenVerify(E, Q, x_ji, r_ji, {X_ji,...,X_jt}) = false, abort
xji := p2p[id].SecretShare
rji := p2p[id].BlindingShare
bvs := bcast[id]
if ok, err := dp.pedersen.Verify(xji, rji, bvs); !ok {
if err != nil {
return nil, err
} else {
return nil, fmt.Errorf("invalid share for participant id=%v", id)
}
}
// Store other participants' shares xji for usage in round 3
dp.otherParticipantShares[id].Share = p2p[id].SecretShare
// 5. sk = (sk+xji) mod q
// NOTE: we use the EcScalar class to add instead of
// just using big.Int Add and Mod
// because Ed25519 will fail with the big.Int Add and Mod
// and Ed25519 uses different little endian vs big endian
// in big.Int
t1 := sk.BigInt()
t2 := xji.Value.BigInt()
r := dp.scalar.Add(t1, t2)
sk = sk.Field().NewElement(r)
}
// Update internal state
dp.round = 3
// 7. Store ski as participant i's secret key share
dp.skShare = sk
// 6. EchoBroadcast {R_1,...,R_t} to all other participants.
return dp.pedersenResult.Verifiers, nil
}