mirror of
https://source.quilibrium.com/quilibrium/ceremonyclient.git
synced 2024-11-14 04:05:17 +00:00
283 lines
12 KiB
Go
283 lines
12 KiB
Go
//
|
|
// Copyright Coinbase, Inc. All Rights Reserved.
|
|
//
|
|
// SPDX-License-Identifier: Apache-2.0
|
|
//
|
|
|
|
// Package dkg implements the Distributed Key Generation (DKG) protocol of [DKLs18](https://eprint.iacr.org/2018/499.pdf).
|
|
// The DKG protocol is defined in "Protocol 2" page 7, of the paper. The Zero Knowledge Proof ideal functionalities are
|
|
// realized using schnorr proofs. Moreover, the seed OT is realized using the Verified Simplest OT protocol.
|
|
package dkg
|
|
|
|
import (
|
|
"crypto/rand"
|
|
|
|
"github.com/gtank/merlin"
|
|
"github.com/pkg/errors"
|
|
"golang.org/x/crypto/sha3"
|
|
|
|
"source.quilibrium.com/quilibrium/monorepo/nekryptology/pkg/core/curves"
|
|
"source.quilibrium.com/quilibrium/monorepo/nekryptology/pkg/ot/base/simplest"
|
|
"source.quilibrium.com/quilibrium/monorepo/nekryptology/pkg/zkp/schnorr"
|
|
)
|
|
|
|
// AliceOutput is the result of running DKG for Alice. It contains both the public and secret values that are needed
|
|
// for signing.
|
|
type AliceOutput struct {
|
|
// PublicKey is the joint public key of Alice and Bob.
|
|
// This value is public.
|
|
PublicKey curves.Point
|
|
|
|
// SecretKeyShare is Alice's secret key for the joint public key.
|
|
// This output must be kept secret. If it is lost, the users will lose access and cannot create signatures.
|
|
SecretKeyShare curves.Scalar
|
|
|
|
// SeedOtResult are the outputs that the receiver will obtain as a result of running the "random" OT protocol.
|
|
// This output must be kept secret. Although, if it is lost the users can run another OT protocol and obtain
|
|
// new values to replace it.
|
|
SeedOtResult *simplest.ReceiverOutput
|
|
}
|
|
|
|
// BobOutput is the result of running DKG for Bob. It contains both the public and secret values that are needed
|
|
// for signing.
|
|
type BobOutput struct {
|
|
// PublicKey is the joint public key of Alice and Bob.
|
|
// This value is public.
|
|
PublicKey curves.Point
|
|
|
|
// SecretKeyShare is Bob's secret key for the joint public key.
|
|
// This output must be kept secret. If it is lost, the users will lose access and cannot create signatures.
|
|
SecretKeyShare curves.Scalar
|
|
|
|
// SeedOtResult are the outputs that the sender will obtain as a result of running the "random" OT protocol.
|
|
// This output must be kept secret. Although, if it is lost the users can run another OT protocol and obtain
|
|
// new values to replace it.
|
|
SeedOtResult *simplest.SenderOutput
|
|
}
|
|
|
|
// Alice struct encoding Alice's state during one execution of the overall signing algorithm.
|
|
// At the end of the joint computation, Alice will NOT obtain the signature.
|
|
type Alice struct {
|
|
kappa int
|
|
s int
|
|
|
|
// prover is a schnorr prover for Alice's portion of public key.
|
|
prover *schnorr.Prover
|
|
|
|
// proof is alice's proof to her portion of the public key. It is stored as an intermediate value, during commitment phase.
|
|
proof *schnorr.Proof
|
|
|
|
// receiver is the base OT receiver.
|
|
receiver *simplest.Receiver
|
|
|
|
// secretKeyShare is Alice's secret key for the joint public key.
|
|
secretKeyShare curves.Scalar
|
|
|
|
// publicKey is the joint public key of Alice and Bob.
|
|
publicKey curves.Point
|
|
|
|
curve *curves.Curve
|
|
|
|
transcript *merlin.Transcript
|
|
}
|
|
|
|
// Bob struct encoding Bob's state during one execution of the overall signing algorithm.
|
|
// At the end of the joint computation, Bob will obtain the signature.
|
|
type Bob struct {
|
|
kappa int
|
|
s int
|
|
|
|
// prover is a schnorr prover for Bob's portion of public key.
|
|
prover *schnorr.Prover // this is a "schnorr statement" for pkB.
|
|
|
|
// sender is the base OT sender.
|
|
sender *simplest.Sender
|
|
|
|
// secretKeyShare is Bob's secret key for the joint public key.
|
|
secretKeyShare curves.Scalar
|
|
|
|
// publicKey is the joint public key of Alice and Bob.
|
|
publicKey curves.Point
|
|
|
|
// schnorr proof commitment to Alice's schnorr proof.
|
|
aliceCommitment schnorr.Commitment
|
|
// 32-byte transcript salt which will be used for Alice's schnorr proof
|
|
aliceSalt [simplest.DigestSize]byte
|
|
|
|
curve *curves.Curve
|
|
|
|
transcript *merlin.Transcript
|
|
}
|
|
|
|
// Round2Output contains the output of the 2nd round of DKG.
|
|
type Round2Output struct {
|
|
// Seed is the random value used to derive the joint unique session id.
|
|
Seed [simplest.DigestSize]byte
|
|
|
|
// Commitment is the commitment to the ZKP to Alice's secret key share.
|
|
Commitment schnorr.Commitment
|
|
}
|
|
|
|
// NewAlice creates a party that can participate in 2-of-2 DKG and threshold signature.
|
|
func NewAlice(kappa int, s int, curve *curves.Curve) *Alice {
|
|
return &Alice{
|
|
kappa: kappa,
|
|
s: s,
|
|
curve: curve,
|
|
transcript: merlin.NewTranscript("Coinbase_DKLs_DKG"),
|
|
}
|
|
}
|
|
|
|
// NewBob creates a party that can participate in 2-of-2 DKG and threshold signature. This party
|
|
// is the receiver of the signature at the end.
|
|
func NewBob(kappa int, s int, curve *curves.Curve) *Bob {
|
|
return &Bob{
|
|
kappa: kappa,
|
|
s: s,
|
|
curve: curve,
|
|
transcript: merlin.NewTranscript("Coinbase_DKLs_DKG"),
|
|
}
|
|
}
|
|
|
|
// Round1GenerateRandomSeed Bob flips random coins, and sends these to Alice
|
|
// in this round, Bob flips 32 random bytes and sends them to Alice.
|
|
// note that this is not _explicitly_ given as part of the protocol in https://eprint.iacr.org/2018/499.pdf, Protocol 1).
|
|
// rather, it is part of our generation of a unique session identifier, for use in subsequent schnorr proofs / seed OT / etc.
|
|
// we do it by having each party sample 32 bytes, then by appending _both_ as salts. secure if either party is honest
|
|
func (bob *Bob) Round1GenerateRandomSeed() ([simplest.DigestSize]byte, error) {
|
|
bobSeed := [simplest.DigestSize]byte{}
|
|
if _, err := rand.Read(bobSeed[:]); err != nil {
|
|
return [simplest.DigestSize]byte{}, errors.Wrap(err, "generating random bytes in bob DKG round 1 generate")
|
|
}
|
|
bob.transcript.AppendMessage([]byte("session_id_bob"), bobSeed[:]) // note: bob appends first here
|
|
return bobSeed, nil
|
|
}
|
|
|
|
// Round2CommitToProof steps 1) and 2) of protocol 2 on page 7.
|
|
func (alice *Alice) Round2CommitToProof(bobSeed [simplest.DigestSize]byte) (*Round2Output, error) {
|
|
aliceSeed := [simplest.DigestSize]byte{}
|
|
if _, err := rand.Read(aliceSeed[:]); err != nil {
|
|
return nil, errors.Wrap(err, "generating random bytes in bob DKG round 1 generate")
|
|
}
|
|
alice.transcript.AppendMessage([]byte("session_id_bob"), bobSeed[:])
|
|
alice.transcript.AppendMessage([]byte("session_id_alice"), aliceSeed[:])
|
|
|
|
var err error
|
|
uniqueSessionId := [simplest.DigestSize]byte{} // note: will use and re-use this below for sub-session IDs.
|
|
copy(uniqueSessionId[:], alice.transcript.ExtractBytes([]byte("salt for simplest OT"), simplest.DigestSize))
|
|
alice.receiver, err = simplest.NewReceiver(alice.curve, alice.kappa, uniqueSessionId)
|
|
if err != nil {
|
|
return nil, errors.Wrap(err, "alice constructing new seed OT receiver in Alice DKG round 1")
|
|
}
|
|
|
|
alice.secretKeyShare = alice.curve.Scalar.Random(rand.Reader)
|
|
copy(uniqueSessionId[:], alice.transcript.ExtractBytes([]byte("salt for alice schnorr"), simplest.DigestSize))
|
|
alice.prover = schnorr.NewProver(alice.curve, nil, sha3.New256(), uniqueSessionId[:])
|
|
var commitment schnorr.Commitment
|
|
alice.proof, commitment, err = alice.prover.ProveCommit(alice.secretKeyShare) // will mutate `pkA`
|
|
if err != nil {
|
|
return nil, errors.Wrap(err, "prove + commit in alice DKG Commit round 1")
|
|
}
|
|
return &Round2Output{
|
|
Commitment: commitment,
|
|
Seed: aliceSeed,
|
|
}, nil
|
|
}
|
|
|
|
// Round3SchnorrProve receives Bob's Commitment and returns schnorr statment + proof.
|
|
// Steps 1 and 3 of protocol 2 on page 7.
|
|
func (bob *Bob) Round3SchnorrProve(round2Output *Round2Output) (*schnorr.Proof, error) {
|
|
bob.transcript.AppendMessage([]byte("session_id_alice"), round2Output.Seed[:])
|
|
|
|
bob.aliceCommitment = round2Output.Commitment // store it, so that we can check when alice decommits
|
|
|
|
var err error
|
|
uniqueSessionId := [simplest.DigestSize]byte{} // note: will use and re-use this below for sub-session IDs.
|
|
copy(uniqueSessionId[:], bob.transcript.ExtractBytes([]byte("salt for simplest OT"), simplest.DigestSize))
|
|
bob.sender, err = simplest.NewSender(bob.curve, bob.kappa, uniqueSessionId)
|
|
if err != nil {
|
|
return nil, errors.Wrap(err, "bob constructing new OT sender in DKG round 2")
|
|
}
|
|
// extract alice's salt in the right order; we won't use this until she reveals her proof and we verify it below
|
|
copy(bob.aliceSalt[:], bob.transcript.ExtractBytes([]byte("salt for alice schnorr"), simplest.DigestSize))
|
|
bob.secretKeyShare = bob.curve.Scalar.Random(rand.Reader)
|
|
copy(uniqueSessionId[:], bob.transcript.ExtractBytes([]byte("salt for bob schnorr"), simplest.DigestSize))
|
|
bob.prover = schnorr.NewProver(bob.curve, nil, sha3.New256(), uniqueSessionId[:])
|
|
proof, err := bob.prover.Prove(bob.secretKeyShare)
|
|
if err != nil {
|
|
return nil, errors.Wrap(err, "bob schnorr proving in DKG round 2")
|
|
}
|
|
return proof, err
|
|
}
|
|
|
|
// Round4VerifyAndReveal step 4 of protocol 2 on page 7.
|
|
func (alice *Alice) Round4VerifyAndReveal(proof *schnorr.Proof) (*schnorr.Proof, error) {
|
|
var err error
|
|
uniqueSessionId := [simplest.DigestSize]byte{}
|
|
copy(uniqueSessionId[:], alice.transcript.ExtractBytes([]byte("salt for bob schnorr"), simplest.DigestSize))
|
|
if err = schnorr.Verify(proof, alice.curve, nil, sha3.New256(), uniqueSessionId[:]); err != nil {
|
|
return nil, errors.Wrap(err, "alice's verification of Bob's schnorr proof failed in DKG round 3")
|
|
}
|
|
alice.publicKey = proof.Statement.Mul(alice.secretKeyShare)
|
|
return alice.proof, nil
|
|
}
|
|
|
|
// Round5DecommitmentAndStartOt step 5 of protocol 2 on page 7.
|
|
func (bob *Bob) Round5DecommitmentAndStartOt(proof *schnorr.Proof) (*schnorr.Proof, error) {
|
|
var err error
|
|
if err = schnorr.DecommitVerify(proof, bob.aliceCommitment, bob.curve, sha3.New256(), nil, bob.aliceSalt[:]); err != nil {
|
|
return nil, errors.Wrap(err, "decommit + verify failed in bob's DKG round 4")
|
|
}
|
|
bob.publicKey = proof.Statement.Mul(bob.secretKeyShare)
|
|
seedOTRound1Output, err := bob.sender.Round1ComputeAndZkpToPublicKey()
|
|
if err != nil {
|
|
return nil, errors.Wrap(err, "bob computing round 1 of seed OT within DKG round 4")
|
|
}
|
|
return seedOTRound1Output, nil
|
|
}
|
|
|
|
// Round6DkgRound2Ot is a thin wrapper around the 2nd round of seed OT protocol.
|
|
func (alice *Alice) Round6DkgRound2Ot(proof *schnorr.Proof) ([]simplest.ReceiversMaskedChoices, error) {
|
|
return alice.receiver.Round2VerifySchnorrAndPadTransfer(proof)
|
|
}
|
|
|
|
// Round7DkgRound3Ot is a thin wrapper around the 3rd round of seed OT protocol.
|
|
func (bob *Bob) Round7DkgRound3Ot(compressedReceiversMaskedChoice []simplest.ReceiversMaskedChoices) ([]simplest.OtChallenge, error) {
|
|
return bob.sender.Round3PadTransfer(compressedReceiversMaskedChoice)
|
|
}
|
|
|
|
// Round8DkgRound4Ot is a thin wrapper around the 4th round of seed OT protocol.
|
|
func (alice *Alice) Round8DkgRound4Ot(challenge []simplest.OtChallenge) ([]simplest.OtChallengeResponse, error) {
|
|
return alice.receiver.Round4RespondToChallenge(challenge)
|
|
}
|
|
|
|
// Round9DkgRound5Ot is a thin wrapper around the 5th round of seed OT protocol.
|
|
func (bob *Bob) Round9DkgRound5Ot(challengeResponses []simplest.OtChallengeResponse) ([]simplest.ChallengeOpening, error) {
|
|
return bob.sender.Round5Verify(challengeResponses)
|
|
}
|
|
|
|
// Round10DkgRound6Ot is a thin wrapper around the 6th round of seed OT protocol.
|
|
func (alice *Alice) Round10DkgRound6Ot(challengeOpenings []simplest.ChallengeOpening) error {
|
|
return alice.receiver.Round6Verify(challengeOpenings)
|
|
}
|
|
|
|
// Output returns the output of the DKG operation. Must be called after step 9. Calling it before that step
|
|
// has undefined behaviour.
|
|
func (alice *Alice) Output() *AliceOutput {
|
|
return &AliceOutput{
|
|
PublicKey: alice.publicKey,
|
|
SecretKeyShare: alice.secretKeyShare,
|
|
SeedOtResult: alice.receiver.Output,
|
|
}
|
|
}
|
|
|
|
// Output returns the output of the DKG operation. Must be called after step 9. Calling it before that step
|
|
// has undefined behaviour.
|
|
func (bob *Bob) Output() *BobOutput {
|
|
return &BobOutput{
|
|
PublicKey: bob.publicKey,
|
|
SecretKeyShare: bob.secretKeyShare,
|
|
SeedOtResult: bob.sender.Output,
|
|
}
|
|
}
|