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better documentation and omit not needed lines of code
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@borislav-itskov
borislav-itskov committed Sep 19, 2023
1 parent c861216 commit d0bd26f
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Showing 3 changed files with 102 additions and 44 deletions.
134 changes: 96 additions & 38 deletions src/core/index.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -6,9 +6,8 @@ import { InternalNoncePairs, InternalNonces, InternalPublicNonces, InternalSigna
import { KeyPair } from '../types'

const curve = ecurve.getCurveByName('secp256k1')
const n = curve.n

const _generateNonce = (): InternalNoncePairs => {
const generateNonce = (): InternalNoncePairs => {
const k = Buffer.from(ethers.utils.randomBytes(32))
const kTwo = Buffer.from(ethers.utils.randomBytes(32))
const kPublic = Buffer.from(secp256k1.publicKeyCreate(k))
Expand All @@ -22,7 +21,7 @@ const _generateNonce = (): InternalNoncePairs => {
}
}

const _bCoefficient = (combinedPublicKey: Buffer, msgHash: string, publicNonces: InternalPublicNonces[]): Buffer => {
const bCoefficient = (combinedPublicKey: Buffer, msgHash: string, publicNonces: InternalPublicNonces[]): Buffer => {
type KeyOf = keyof InternalPublicNonces
const arrayColumn = (arr: Array<InternalPublicNonces>, n: KeyOf) => arr.map(x => x[n])
const kPublicNonces = secp256k1.publicKeyCombine(arrayColumn(publicNonces, 'kPublic'))
Expand All @@ -37,9 +36,9 @@ const _bCoefficient = (combinedPublicKey: Buffer, msgHash: string, publicNonces:
const areBuffersSame = (buf1: Buffer, buf2: Buffer): boolean => {
if (buf1.byteLength != buf2.byteLength) return false

var dv1 = Buffer.from(buf1)
var dv2 = Buffer.from(buf2)
for (var i = 0; i != buf1.byteLength; i++) {
const dv1 = Buffer.from(buf1)
const dv2 = Buffer.from(buf2)
for (let i = 0; i != buf1.byteLength; i++) {
if (dv1[i] != dv2[i]) return false
}

Expand All @@ -48,8 +47,8 @@ const areBuffersSame = (buf1: Buffer, buf2: Buffer): boolean => {

const challenge = (R: Buffer, msgHash: string, publicKey: Buffer): Buffer => {
// convert R to address
var R_uncomp = secp256k1.publicKeyConvert(R, false)
var R_addr = ethers.utils.arrayify(ethers.utils.keccak256(R_uncomp.slice(1, 65))).slice(12, 32)
const R_uncomp = secp256k1.publicKeyConvert(R, false)
const R_addr = ethers.utils.arrayify(ethers.utils.keccak256(R_uncomp.slice(1, 65))).slice(12, 32)

// e = keccak256(address(R) || compressed publicKey || msgHash)
return Buffer.from(ethers.utils.arrayify(
Expand All @@ -60,6 +59,22 @@ const challenge = (R: Buffer, msgHash: string, publicKey: Buffer): Buffer => {
))
}

export const generateRandomKeys = () => {
let privKeyBytes: Buffer
do {
privKeyBytes = Buffer.from(ethers.utils.randomBytes(32))
} while (!secp256k1.privateKeyVerify(privKeyBytes))

const pubKey = Buffer.from(secp256k1.publicKeyCreate(privKeyBytes))

const data = {
publicKey: pubKey,
privateKey: privKeyBytes,
}

return new KeyPair(data)
}

export const _generateL = (publicKeys: Array<Buffer>) => {
return ethers.utils.keccak256(_concatTypedArrays(publicKeys.sort(Buffer.compare)))
}
Expand All @@ -78,33 +93,31 @@ export const _aCoefficient = (publicKey: Buffer, L: string): Buffer => {
)))
}

export const generateRandomKeys = () => {
let privKeyBytes: Buffer
do {
privKeyBytes = Buffer.from(ethers.utils.randomBytes(32))
} while (!secp256k1.privateKeyVerify(privKeyBytes))

const pubKey = Buffer.from(secp256k1.publicKeyCreate(privKeyBytes))

const data = {
publicKey: pubKey,
privateKey: privKeyBytes,
}

return new KeyPair(data)
}

/**
* Hash the privateKey so it is not in plain text in arrays.
* A separate method for easy reuse
*
* @param privateKey
* @returns string
*/
export const _hashPrivateKey = (privateKey: Buffer): string => {
return ethers.utils.keccak256(privateKey)
}

export const _generatePublicNonces = (privateKey: Buffer): {
/**
* Generate the nonces for the next signature.
* Use the hash of the private key for a unique identifier
* TODO: maybe change this with to the public key...
* @param privateKey
* @returns
*/
export const _generateNonces = (privateKey: Buffer): {
privateNonceData: Pick<InternalNoncePairs, 'k' | 'kTwo'>,
publicNonceData: InternalPublicNonces,
hash: string,
} => {
const hash = _hashPrivateKey(privateKey)
const nonce = _generateNonce()
const nonce = generateNonce()

return {
hash,
Expand Down Expand Up @@ -133,7 +146,7 @@ export const _multiSigSign = (nonces: InternalNonces, combinedPublicKey: Buffer,
const publicKey = Buffer.from(secp256k1.publicKeyCreate(localPk))
const L = _generateL(publicKeys)
const a = _aCoefficient(publicKey, L)
const b = _bCoefficient(combinedPublicKey, hash, publicNonces)
const b = bCoefficient(combinedPublicKey, hash, publicNonces)

const effectiveNonces = publicNonces.map((batch) => {
return Buffer.from(secp256k1.publicKeyCombine([batch.kPublic, secp256k1.publicKeyTweakMul(batch.kTwoPublic, b)]))
Expand Down Expand Up @@ -164,17 +177,23 @@ export const _multiSigSign = (nonces: InternalNonces, combinedPublicKey: Buffer,
// kTwo * b
const kTwoMulB = secp256k1.privateKeyTweakMul(kTwo, b)

// k + kTwoMulB + xea
const final = secp256k1.privateKeyTweakAdd(kPlusxea, kTwoMulB)
// k + kTwoMulB + xea mod(n)
const final = Buffer.from(secp256k1.privateKeyTweakAdd(kPlusxea, kTwoMulB))

return {
// s = k + xea mod(n)
signature: bigi.fromBuffer(final).mod(n).toBuffer(32),
signature: final,
challenge: e,
finalPublicNonce: R
}
}

/**
* Sum the passed signatures.
* mod(n) is automatically applied in the privateKeyTweakAdd function
*
* @param signatures
* @returns Buffer summed signature
*/
export const _sumSigs = (signatures: Buffer[]): Buffer => {
let combined = new Uint8Array()

Expand All @@ -185,6 +204,20 @@ export const _sumSigs = (signatures: Buffer[]): Buffer => {
return Buffer.from(combined)
}

/**
* The verification formula is: s*G = R + H(m)*X
* s is the signature
* G is the generation point of the elliptic curve
* R is the public nonce, or the ephemeral public nonce
* H(m) is the hash of the message
* X is the public key
*
* @param s the signature
* @param hash the signed hash
* @param R the public nonce used for this signature
* @param publicKey the public key used for this signature
* @returns bool
*/
export const _verify = (s: Buffer, hash: string, R: Buffer, publicKey: Buffer): boolean => {
const eC = challenge(R, hash, publicKey)

Expand All @@ -196,32 +229,57 @@ export const _verify = (s: Buffer, hash: string, R: Buffer, publicKey: Buffer):
return sG.equals(RplusPetest)
}

export const _generatePk = (combinedPublicKey: Buffer): string => {
/**
* Take the x-coordinate of the public key and transform it
* into ethereum-like address
*
* @param combinedPublicKey
* @returns address
*/
export const _generateSchnorrAddr = (combinedPublicKey: Buffer): string => {
if (combinedPublicKey.length != 33) {
throw Error('Public key should be 33 length, 1 byte parity and 32 bytes x-coordinate')
}

const px = ethers.utils.hexlify(combinedPublicKey.subarray(1,33))
return '0x' + px.slice(px.length - 40, px.length)
}

export const _sign = (privateKey: Buffer, hash: string): InternalSignature => {
// if we use secp256k1 directly on the private key for operations
// different than publicKeyCreate (privateKeyTweakMul, for example),
// the private key gets modified. We do not want that and hence
// do operations with a local copy
const localPk = Buffer.from(privateKey)
const publicKey = Buffer.from(secp256k1.publicKeyCreate(localPk))

// R = G * k
var k = ethers.utils.randomBytes(32)
var R = Buffer.from(secp256k1.publicKeyCreate(k))
const k = ethers.utils.randomBytes(32)
const R = Buffer.from(secp256k1.publicKeyCreate(k))

// e = h(address(R) || compressed pubkey || m)
var e = challenge(R, hash, publicKey)
const e = challenge(R, hash, publicKey)

// xe = x * e
var xe = secp256k1.privateKeyTweakMul(localPk, e)
const xe = secp256k1.privateKeyTweakMul(localPk, e)

// s = k + xe mod(n)
var s = Buffer.from(secp256k1.privateKeyTweakAdd(k, xe))
s = bigi.fromBuffer(s).mod(n).toBuffer(32)
const s = Buffer.from(secp256k1.privateKeyTweakAdd(k, xe))

return {
finalPublicNonce: R,
challenge: e,
signature: s
}
}

/**
* Provide a default hash function
* It is not mandotory to use this one.
*
* @param message
* @returns string
*/
export const _hashMessage = (message: string): string => {
return ethers.utils.solidityKeccak256(['string'], [message])
}
11 changes: 6 additions & 5 deletions src/schnorrkel.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -2,15 +2,15 @@ import secp256k1 from 'secp256k1'

import { Key, Nonces, PublicNonces, Signature, NoncePairs } from './types'

import { _generateL, _aCoefficient, _generatePublicNonces, _multiSigSign, _hashPrivateKey, _sumSigs, _verify, _generatePk, _sign } from './core'
import { _generateL, _aCoefficient, _generateNonces, _multiSigSign, _hashPrivateKey, _sumSigs, _verify, _generateSchnorrAddr, _sign } from './core'
import { InternalNonces, InternalPublicNonces, InternalSignature } from './core/types'
import { Challenge, FinalPublicNonce, SignatureOutput } from './types/signature'

class Schnorrkel {
protected nonces: Nonces = {}

private _setNonce(privateKey: Buffer): string {
const { publicNonceData, privateNonceData, hash } = _generatePublicNonces(privateKey)
const { publicNonceData, privateNonceData, hash } = _generateNonces(privateKey)

const mappedPublicNonce: PublicNonces = {
kPublic: new Key(Buffer.from(publicNonceData.kPublic)),
Expand Down Expand Up @@ -80,11 +80,12 @@ class Schnorrkel {
}

static getCombinedAddress(publicKeys: Array<Key>): string {
if (publicKeys.length < 2) throw Error('At least 2 public keys should be provided')
if (publicKeys.length < 2) {
throw Error('At least 2 public keys should be provided')
}

const combinedPublicKey = Schnorrkel.getCombinedPublicKey(publicKeys)
const px = _generatePk(combinedPublicKey.buffer)
return px
return _generateSchnorrAddr(combinedPublicKey.buffer)
}

generatePublicNonces(privateKey: Key): PublicNonces {
Expand Down
1 change: 0 additions & 1 deletion tests/schnorrkel/onchainMultiSign.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -4,7 +4,6 @@ import Schnorrkel from '../../src/index'
import { compile } from '../../utils/compile.js'
import { wallet2 } from '../config.js'
import DefaultSigner from '../../utils/DefaultSigner'
import { _generatePk } from '../../src/core'
const ERC1271_MAGICVALUE_BYTES32 = '0x1626ba7e'

describe('Multi Sign Tests', function () {
Expand Down

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