ceremonyclient/nekryptology/pkg/dkg/gennaro/round3.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"
)
// Round3Bcast contains values that will be broadcast to other participants.
type Round3Bcast = v1.ShareVerifier
// Round3 computes the third round for Gennaro DKG
// Algorithm 4 - Gennaro DKG Round 3
// bcast contains all Round2 broadcast from other participants to this participant.
func (dp *Participant) Round3(bcast map[uint32]Round2Bcast) (*Round3Bcast, *v1.ShamirShare, error) {
// Check participant is not empty
if dp == nil || dp.curve == nil {
return nil, nil, internal.ErrNilArguments
}
// Check participant has the correct dkg round number
if dp.round != 3 {
return nil, nil, internal.ErrInvalidRound
}
// Check the input is valid
if len(bcast) == 0 {
return nil, nil, internal.ErrNilArguments
}
// 1. SetBigInt Pk = R_i1
Pk := dp.pedersenResult.Verifiers[0]
// 2. for j in 1,...,n
for id := range bcast {
// 3. if i = j continue
if id == dp.id {
continue
}
// 4. If FeldmanVerify(E, xji, {R_j1,...,R_jt}) = false; abort
xji := dp.otherParticipantShares[id].Share
vs := bcast[id]
if ok, err := dp.feldman.Verify(xji, vs); !ok {
if err != nil {
return nil, nil, err
} else {
return nil, nil, fmt.Errorf("invalid share for participant #{id}")
}
}
// Store the feldman verifiers for round 4
dp.otherParticipantShares[id].Verifiers = vs
// 5. Pk = Pk+R_j1
temp, err := Pk.Add(bcast[id][0])
if err != nil {
return nil, nil, fmt.Errorf("error in computing Pk+R_j1")
} //nolint:errcheck
Pk = temp
}
// This is a sanity check to make sure nothing went wrong
// when computing the public key
if !Pk.IsOnCurve() || Pk.IsIdentity() {
return nil, nil, fmt.Errorf("invalid public key")
}
// 6. Store Pk as the public verification key
dp.verificationKey = Pk
// Update internal state
dp.round = 4
skShare := v1.ShamirShare{
Identifier: dp.id,
Value: dp.skShare,
}
// Output Pk as the public verification key
return Pk, &skShare, nil
}