cmp-ecdsa

A Go implementation of the "CMP" protocol by Canetti et al. for threshold ECDSA signing, with some additions to improve its practical reliability, including the "echo broadcast" from Goldwasser and Lindell. We documented these in threshold_protocol.pdf. A list of proposed improvements is in TODO.md. Our implementation supports ECDSA with secp256k1.

Usage

Sessions

Protocol data is stored in a session.Session struct.

Keygen

baseSession, err := session.NewKeygenSession([]party.ID{"a","b","c"}, 2, "a") (*Keygen, error) 
if err != nil {
	//handle err
}
p, err := protocols.NewProtocol(baseSession, refresh.Create)
if err != nil {
    //handle err
}
inChan, outChan, errChan := p.Start()
// TODO handle message passing 
refreshedSession, err := p.GetSession()
if err != nil {
    //handle err
}

Refresh

var oldSession session.Session
if err != nil {
	//handle err
}
p, err := protocols.NewProtocol(baseSession, refresh.Create)
if err != nil {
    //handle err
}
inChan, outChan, errChan := p.Start()
// TODO handle message passing 
refreshedSession, err := p.GetSession()
if err != nil {
    //handle err
}

Sign

For now, we only implement the 4 round interactive signing protocol.

var (
	refreshedSession session.Session
	message []byte
	signers = []party.ID
)
signSession, err :=  NewSignSession(refreshedSession, signerIDs, message)
if err != nil {
	//handle err
}
p, err := protocols.NewProtocol(signSession, sign.Create)
if err != nil {
    //handle err
}
inChan, outChan, errChan := p.Start()
// TODO handle message passing 
sig, err := p.GetSignature()
if err != nil {
    //handle err
}

Network

The messages returned by the protocol can be transmitted through an authenticated point-to-point network.

Build

cmp-ecdsa requires a custom version of gogo which enables the use of *big.Int in protobufs. This version can be compiled by applying the path from trasc/casttypewith It can be installed using the following shell commands:

git clone https://github.com/gogo/protobuf $GOPATH/src/github.com/gogo/protobuf
cd $GOPATH/src/github.com/gogo/protobuf
git remote add trasc https://github.com/trasc/protobuf.git
git fetch trasc
git merge trasc/casttypewith
cd protoc-gen-gogofaster
go build
cp protoc-gen-gogofaster $GOPATH/bin

Once installed, running make in the root will regenerate all .proto files.

Intellectual property

This code is copyright (c) Adrian Hamelink and Taurus SA, 2021, and under Apache 2.0 license.