ceremonyclient/nekryptology/pkg/ted25519/frost/participant.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 frost is an implementation of t-of-n threshold signature of https://eprint.iacr.org/2020/852.pdf
package frost
import (
"fmt"
"source.quilibrium.com/quilibrium/monorepo/nekryptology/internal"
"source.quilibrium.com/quilibrium/monorepo/nekryptology/pkg/core/curves"
"source.quilibrium.com/quilibrium/monorepo/nekryptology/pkg/dkg/frost"
)
// Signer is a tSchnorr player performing the signing operation.
type Signer struct {
skShare curves.Scalar // secret signing share for this signer
vkShare curves.Point // store verification key share
verificationKey curves.Point // verification key
id uint32 // The ID assigned to this signer's shamir share
threshold uint32
curve *curves.Curve
round uint
lCoeffs map[uint32]curves.Scalar // lCoeffs are Lagrange coefficients of each cosigner.
cosigners []uint32
state *state // Accumulated intermediate values associated with signing
challengeDeriver ChallengeDerive
}
type state struct {
// Round 1
capD, capE curves.Point // capD, capE are commitments this signer generates in signing round 1
smallD, smallE curves.Scalar // smallD, smallE are scalars this signer generates in signing round 1
// Round 2
commitments map[uint32]*Round1Bcast // Store commitments broadcast after signing round 1
msg []byte
c curves.Scalar
capRs map[uint32]curves.Point
sumR curves.Point
}
// NewSigner create a signer from a dkg participant
// Note that we can pre-assign Lagrange coefficients lcoeffs of each cosigner. This optimizes performance.
// See paragraph 3 of section 3 in the draft - https://tools.ietf.org/pdf/draft-komlo-frost-00.pdf
func NewSigner(info *frost.DkgParticipant, id, thresh uint32, lcoeffs map[uint32]curves.Scalar, cosigners []uint32, challengeDeriver ChallengeDerive) (*Signer, error) {
if info == nil || len(cosigners) == 0 || len(lcoeffs) == 0 {
return nil, internal.ErrNilArguments
}
if thresh > uint32(len(cosigners)) {
return nil, fmt.Errorf("threshold is higher than number of signers")
}
if len(lcoeffs) != len(cosigners) {
return nil, fmt.Errorf("expected coefficients to be equal to number of cosigners")
}
// Check if cosigners and lcoeffs contain the same IDs
for i := 0; i < len(cosigners); i++ {
id := cosigners[i]
if _, ok := lcoeffs[id]; !ok {
return nil, fmt.Errorf("lcoeffs and cosigners have inconsistent ID")
}
}
return &Signer{
skShare: info.SkShare,
vkShare: info.VkShare,
verificationKey: info.VerificationKey,
id: id,
threshold: thresh,
curve: info.Curve,
round: 1,
lCoeffs: lcoeffs,
cosigners: cosigners,
state: &state{},
challengeDeriver: challengeDeriver,
}, nil
}