Typescript Musig

Introduction

The project is based on schnorr signatures to implement the multi-signature part of BIP-0340, using the specific algorithm musig.The implementation of the algorithm refers to the implementation of Musig in this repository.You can also read this blog or paper to get more content about musig.

In order to improve the speed and reduce the size of the code, I used a lot of functions and classes from noble-secp256k1 in the implementation of musig.You can find these code in src\@noble\secp256k1 path.

Warn: The underlying functions and classes from noble-secp256k1 of this repository are cryptographically secure and audited, but the code implementation process is unaudited by my personal code writing, which may have vulnerabilities such as timing attacks so it is not recommended for production environments.

Usage

You need to compile this code yourself, you can tsc command.

The sample code is as follows:

import { utils, schnorr } from "./@noble/secp256k1/index.js"
import { SessionData, aggregateTranserData, partialSigCombine, partialSign } from "./index.js"

const pubKeys= [
    utils.hexToBytes('846f34fdb2345f4bf932cb4b7d278fb3af24f44224fb52ae551781c3a3cad68a'),
    utils.hexToBytes('50cebaa0efcb443f366240beb66504e14df69dc66aae829af80aa03ea25e1802'),
];

const privateKey1 = BigInt('0xadd2b25e2d356bec3770305391cbc80cab3a40057ad836bcb49ef3eed74a3fee')
const privateKey2 = BigInt('0xc5487234745cebddf6c6588995c16cebc029beed9f7affbb13d5cbe6c7a9e129')

const message = await utils.sha256('muSig is awesome!');

const session1 = new SessionData(0, privateKey1, pubKeys, message);
const session2 = new SessionData(1, privateKey2, pubKeys, message);

let sessions = [
    await session1.exportSession(),
    await session2.exportSession()
]

let aggregationTranser = aggregateTranserData(sessions);

let partialSignature1 = await partialSign(aggregationTranser, session1);
let partialSignature2 = await partialSign(aggregationTranser, session2);

let signature = await partialSigCombine(aggregationTranser, [partialSignature1, partialSignature2]);

let isValid = await schnorr.verify(signature, session1.message, utils.numTo32bStr(await session1.pubKeyCombined))

console.log(isValid)

To use this code under application, you need to complete 3 rounds of message exchange. In the first round of message exchange, each signer shoud exchange publickey and generate pubKeys. In the second round of message exchange, signer should exchange session.exportSession() and finish partialSign method. In the third round of message exchange, each signer should exchange partialSignature. After completing three rounds of information exchange, each signer can run the function partialSigCombine locally to obtain the final complete signature after obtaining partial signature information and each signer can run schnorr.verify to verify the signature.

During the use of this code, you may encounter this error:

Error: hexToBytes: received invalid unpadded hex63

This error occurs because the generated value of the random number does not satisfy certain conditions, I have not handled this error in the code, if you encounter this error, you can rerun the code to get a random number that meets the criteria.

If you can fix this error, please send a PR.