bls.ts•14.1 kB
/*! noble-curves - MIT License (c) 2022 Paul Miller (paulmillr.com) */
/**
* BLS (Barreto-Lynn-Scott) family of pairing-friendly curves.
* Implements BLS (Boneh-Lynn-Shacham) signatures.
* Consists of two curves: G1 and G2:
* - G1 is a subgroup of (x, y) E(Fq) over y² = x³ + 4.
* - G2 is a subgroup of ((x₁, x₂+i), (y₁, y₂+i)) E(Fq²) over y² = x³ + 4(1 + i) where i is √-1
* - Gt, created by bilinear (ate) pairing e(G1, G2), consists of p-th roots of unity in
* Fq^k where k is embedding degree. Only degree 12 is currently supported, 24 is not.
* Pairing is used to aggregate and verify signatures.
* We are using Fp for private keys (shorter) and Fp₂ for signatures (longer).
* Some projects may prefer to swap this relation, it is not supported for now.
*/
import { AffinePoint } from './curve.js';
import { IField, getMinHashLength, mapHashToField } from './modular.js';
import { Hex, PrivKey, CHash, bitLen, bitGet, ensureBytes } from './utils.js';
import * as htf from './hash-to-curve.js';
import {
CurvePointsType,
ProjPointType as ProjPointType,
CurvePointsRes,
weierstrassPoints,
} from './weierstrass.js';
type Fp = bigint; // Can be different field?
// prettier-ignore
const _2n = BigInt(2), _3n = BigInt(3);
export type SignatureCoder<Fp2> = {
fromHex(hex: Hex): ProjPointType<Fp2>;
toRawBytes(point: ProjPointType<Fp2>): Uint8Array;
toHex(point: ProjPointType<Fp2>): string;
};
export type CurveType<Fp, Fp2, Fp6, Fp12> = {
G1: Omit<CurvePointsType<Fp>, 'n'> & {
mapToCurve: htf.MapToCurve<Fp>;
htfDefaults: htf.Opts;
};
G2: Omit<CurvePointsType<Fp2>, 'n'> & {
Signature: SignatureCoder<Fp2>;
mapToCurve: htf.MapToCurve<Fp2>;
htfDefaults: htf.Opts;
};
fields: {
Fp: IField<Fp>;
Fr: IField<bigint>;
Fp2: IField<Fp2> & {
reim: (num: Fp2) => { re: bigint; im: bigint };
multiplyByB: (num: Fp2) => Fp2;
frobeniusMap(num: Fp2, power: number): Fp2;
};
Fp6: IField<Fp6>;
Fp12: IField<Fp12> & {
frobeniusMap(num: Fp12, power: number): Fp12;
multiplyBy014(num: Fp12, o0: Fp2, o1: Fp2, o4: Fp2): Fp12;
conjugate(num: Fp12): Fp12;
finalExponentiate(num: Fp12): Fp12;
};
};
params: {
x: bigint;
r: bigint;
};
htfDefaults: htf.Opts;
hash: CHash; // Because we need outputLen for DRBG
randomBytes: (bytesLength?: number) => Uint8Array;
};
export type CurveFn<Fp, Fp2, Fp6, Fp12> = {
getPublicKey: (privateKey: PrivKey) => Uint8Array;
sign: {
(message: Hex, privateKey: PrivKey): Uint8Array;
(message: ProjPointType<Fp2>, privateKey: PrivKey): ProjPointType<Fp2>;
};
verify: (
signature: Hex | ProjPointType<Fp2>,
message: Hex | ProjPointType<Fp2>,
publicKey: Hex | ProjPointType<Fp>
) => boolean;
verifyBatch: (
signature: Hex | ProjPointType<Fp2>,
messages: (Hex | ProjPointType<Fp2>)[],
publicKeys: (Hex | ProjPointType<Fp>)[]
) => boolean;
aggregatePublicKeys: {
(publicKeys: Hex[]): Uint8Array;
(publicKeys: ProjPointType<Fp>[]): ProjPointType<Fp>;
};
aggregateSignatures: {
(signatures: Hex[]): Uint8Array;
(signatures: ProjPointType<Fp2>[]): ProjPointType<Fp2>;
};
millerLoop: (ell: [Fp2, Fp2, Fp2][], g1: [Fp, Fp]) => Fp12;
pairing: (P: ProjPointType<Fp>, Q: ProjPointType<Fp2>, withFinalExponent?: boolean) => Fp12;
G1: CurvePointsRes<Fp> & ReturnType<typeof htf.createHasher<Fp>>;
G2: CurvePointsRes<Fp2> & ReturnType<typeof htf.createHasher<Fp2>>;
Signature: SignatureCoder<Fp2>;
params: {
x: bigint;
r: bigint;
G1b: bigint;
G2b: Fp2;
};
fields: {
Fp: IField<Fp>;
Fp2: IField<Fp2>;
Fp6: IField<Fp6>;
Fp12: IField<Fp12>;
Fr: IField<bigint>;
};
utils: {
randomPrivateKey: () => Uint8Array;
calcPairingPrecomputes: (p: AffinePoint<Fp2>) => [Fp2, Fp2, Fp2][];
};
};
export function bls<Fp2, Fp6, Fp12>(
CURVE: CurveType<Fp, Fp2, Fp6, Fp12>
): CurveFn<Fp, Fp2, Fp6, Fp12> {
// Fields are specific for curve, so for now we'll need to pass them with opts
const { Fp, Fr, Fp2, Fp6, Fp12 } = CURVE.fields;
const BLS_X_LEN = bitLen(CURVE.params.x);
// Pre-compute coefficients for sparse multiplication
// Point addition and point double calculations is reused for coefficients
function calcPairingPrecomputes(p: AffinePoint<Fp2>) {
const { x, y } = p;
// prettier-ignore
const Qx = x, Qy = y, Qz = Fp2.ONE;
// prettier-ignore
let Rx = Qx, Ry = Qy, Rz = Qz;
let ell_coeff: [Fp2, Fp2, Fp2][] = [];
for (let i = BLS_X_LEN - 2; i >= 0; i--) {
// Double
let t0 = Fp2.sqr(Ry); // Ry²
let t1 = Fp2.sqr(Rz); // Rz²
let t2 = Fp2.multiplyByB(Fp2.mul(t1, _3n)); // 3 * T1 * B
let t3 = Fp2.mul(t2, _3n); // 3 * T2
let t4 = Fp2.sub(Fp2.sub(Fp2.sqr(Fp2.add(Ry, Rz)), t1), t0); // (Ry + Rz)² - T1 - T0
ell_coeff.push([
Fp2.sub(t2, t0), // T2 - T0
Fp2.mul(Fp2.sqr(Rx), _3n), // 3 * Rx²
Fp2.neg(t4), // -T4
]);
Rx = Fp2.div(Fp2.mul(Fp2.mul(Fp2.sub(t0, t3), Rx), Ry), _2n); // ((T0 - T3) * Rx * Ry) / 2
Ry = Fp2.sub(Fp2.sqr(Fp2.div(Fp2.add(t0, t3), _2n)), Fp2.mul(Fp2.sqr(t2), _3n)); // ((T0 + T3) / 2)² - 3 * T2²
Rz = Fp2.mul(t0, t4); // T0 * T4
if (bitGet(CURVE.params.x, i)) {
// Addition
let t0 = Fp2.sub(Ry, Fp2.mul(Qy, Rz)); // Ry - Qy * Rz
let t1 = Fp2.sub(Rx, Fp2.mul(Qx, Rz)); // Rx - Qx * Rz
ell_coeff.push([
Fp2.sub(Fp2.mul(t0, Qx), Fp2.mul(t1, Qy)), // T0 * Qx - T1 * Qy
Fp2.neg(t0), // -T0
t1, // T1
]);
let t2 = Fp2.sqr(t1); // T1²
let t3 = Fp2.mul(t2, t1); // T2 * T1
let t4 = Fp2.mul(t2, Rx); // T2 * Rx
let t5 = Fp2.add(Fp2.sub(t3, Fp2.mul(t4, _2n)), Fp2.mul(Fp2.sqr(t0), Rz)); // T3 - 2 * T4 + T0² * Rz
Rx = Fp2.mul(t1, t5); // T1 * T5
Ry = Fp2.sub(Fp2.mul(Fp2.sub(t4, t5), t0), Fp2.mul(t3, Ry)); // (T4 - T5) * T0 - T3 * Ry
Rz = Fp2.mul(Rz, t3); // Rz * T3
}
}
return ell_coeff;
}
function millerLoop(ell: [Fp2, Fp2, Fp2][], g1: [Fp, Fp]): Fp12 {
const { x } = CURVE.params;
const Px = g1[0];
const Py = g1[1];
let f12 = Fp12.ONE;
for (let j = 0, i = BLS_X_LEN - 2; i >= 0; i--, j++) {
const E = ell[j];
f12 = Fp12.multiplyBy014(f12, E[0], Fp2.mul(E[1], Px), Fp2.mul(E[2], Py));
if (bitGet(x, i)) {
j += 1;
const F = ell[j];
f12 = Fp12.multiplyBy014(f12, F[0], Fp2.mul(F[1], Px), Fp2.mul(F[2], Py));
}
if (i !== 0) f12 = Fp12.sqr(f12);
}
return Fp12.conjugate(f12);
}
const utils = {
randomPrivateKey: (): Uint8Array => {
const length = getMinHashLength(Fr.ORDER);
return mapHashToField(CURVE.randomBytes(length), Fr.ORDER);
},
calcPairingPrecomputes,
};
// Point on G1 curve: (x, y)
const G1_ = weierstrassPoints({ n: Fr.ORDER, ...CURVE.G1 });
const G1 = Object.assign(
G1_,
htf.createHasher(G1_.ProjectivePoint, CURVE.G1.mapToCurve, {
...CURVE.htfDefaults,
...CURVE.G1.htfDefaults,
})
);
// Sparse multiplication against precomputed coefficients
// TODO: replace with weakmap?
type withPairingPrecomputes = { _PPRECOMPUTES: [Fp2, Fp2, Fp2][] | undefined };
function pairingPrecomputes(point: G2): [Fp2, Fp2, Fp2][] {
const p = point as G2 & withPairingPrecomputes;
if (p._PPRECOMPUTES) return p._PPRECOMPUTES;
p._PPRECOMPUTES = calcPairingPrecomputes(point.toAffine());
return p._PPRECOMPUTES;
}
// TODO: export
// function clearPairingPrecomputes(point: G2) {
// const p = point as G2 & withPairingPrecomputes;
// p._PPRECOMPUTES = undefined;
// }
// Point on G2 curve (complex numbers): (x₁, x₂+i), (y₁, y₂+i)
const G2_ = weierstrassPoints({ n: Fr.ORDER, ...CURVE.G2 });
const G2 = Object.assign(
G2_,
htf.createHasher(G2_.ProjectivePoint as htf.H2CPointConstructor<Fp2>, CURVE.G2.mapToCurve, {
...CURVE.htfDefaults,
...CURVE.G2.htfDefaults,
})
);
const { Signature } = CURVE.G2;
// Calculates bilinear pairing
function pairing(Q: G1, P: G2, withFinalExponent: boolean = true): Fp12 {
if (Q.equals(G1.ProjectivePoint.ZERO) || P.equals(G2.ProjectivePoint.ZERO))
throw new Error('pairing is not available for ZERO point');
Q.assertValidity();
P.assertValidity();
// Performance: 9ms for millerLoop and ~14ms for exp.
const Qa = Q.toAffine();
const looped = millerLoop(pairingPrecomputes(P), [Qa.x, Qa.y]);
return withFinalExponent ? Fp12.finalExponentiate(looped) : looped;
}
type G1 = typeof G1.ProjectivePoint.BASE;
type G2 = typeof G2.ProjectivePoint.BASE;
type G1Hex = Hex | G1;
type G2Hex = Hex | G2;
function normP1(point: G1Hex): G1 {
return point instanceof G1.ProjectivePoint ? (point as G1) : G1.ProjectivePoint.fromHex(point);
}
function normP2(point: G2Hex): G2 {
return point instanceof G2.ProjectivePoint ? point : Signature.fromHex(point);
}
function normP2Hash(point: G2Hex, htfOpts?: htf.htfBasicOpts): G2 {
return point instanceof G2.ProjectivePoint
? point
: (G2.hashToCurve(ensureBytes('point', point), htfOpts) as G2);
}
// Multiplies generator by private key.
// P = pk x G
function getPublicKey(privateKey: PrivKey): Uint8Array {
return G1.ProjectivePoint.fromPrivateKey(privateKey).toRawBytes(true);
}
// Executes `hashToCurve` on the message and then multiplies the result by private key.
// S = pk x H(m)
function sign(message: Hex, privateKey: PrivKey, htfOpts?: htf.htfBasicOpts): Uint8Array;
function sign(message: G2, privateKey: PrivKey, htfOpts?: htf.htfBasicOpts): G2;
function sign(message: G2Hex, privateKey: PrivKey, htfOpts?: htf.htfBasicOpts): Uint8Array | G2 {
const msgPoint = normP2Hash(message, htfOpts);
msgPoint.assertValidity();
const sigPoint = msgPoint.multiply(G1.normPrivateKeyToScalar(privateKey));
if (message instanceof G2.ProjectivePoint) return sigPoint;
return Signature.toRawBytes(sigPoint);
}
// Checks if pairing of public key & hash is equal to pairing of generator & signature.
// e(P, H(m)) == e(G, S)
function verify(
signature: G2Hex,
message: G2Hex,
publicKey: G1Hex,
htfOpts?: htf.htfBasicOpts
): boolean {
const P = normP1(publicKey);
const Hm = normP2Hash(message, htfOpts);
const G = G1.ProjectivePoint.BASE;
const S = normP2(signature);
// Instead of doing 2 exponentiations, we use property of billinear maps
// and do one exp after multiplying 2 points.
const ePHm = pairing(P.negate(), Hm, false);
const eGS = pairing(G, S, false);
const exp = Fp12.finalExponentiate(Fp12.mul(eGS, ePHm));
return Fp12.eql(exp, Fp12.ONE);
}
// Adds a bunch of public key points together.
// pk1 + pk2 + pk3 = pkA
function aggregatePublicKeys(publicKeys: Hex[]): Uint8Array;
function aggregatePublicKeys(publicKeys: G1[]): G1;
function aggregatePublicKeys(publicKeys: G1Hex[]): Uint8Array | G1 {
if (!publicKeys.length) throw new Error('Expected non-empty array');
const agg = publicKeys.map(normP1).reduce((sum, p) => sum.add(p), G1.ProjectivePoint.ZERO);
const aggAffine = agg; //.toAffine();
if (publicKeys[0] instanceof G1.ProjectivePoint) {
aggAffine.assertValidity();
return aggAffine;
}
// toRawBytes ensures point validity
return aggAffine.toRawBytes(true);
}
// Adds a bunch of signature points together.
function aggregateSignatures(signatures: Hex[]): Uint8Array;
function aggregateSignatures(signatures: G2[]): G2;
function aggregateSignatures(signatures: G2Hex[]): Uint8Array | G2 {
if (!signatures.length) throw new Error('Expected non-empty array');
const agg = signatures.map(normP2).reduce((sum, s) => sum.add(s), G2.ProjectivePoint.ZERO);
const aggAffine = agg; //.toAffine();
if (signatures[0] instanceof G2.ProjectivePoint) {
aggAffine.assertValidity();
return aggAffine;
}
return Signature.toRawBytes(aggAffine);
}
// https://ethresear.ch/t/fast-verification-of-multiple-bls-signatures/5407
// e(G, S) = e(G, SUM(n)(Si)) = MUL(n)(e(G, Si))
function verifyBatch(
signature: G2Hex,
messages: G2Hex[],
publicKeys: G1Hex[],
htfOpts?: htf.htfBasicOpts
): boolean {
// @ts-ignore
// console.log('verifyBatch', bytesToHex(signature as any), messages, publicKeys.map(bytesToHex));
if (!messages.length) throw new Error('Expected non-empty messages array');
if (publicKeys.length !== messages.length)
throw new Error('Pubkey count should equal msg count');
const sig = normP2(signature);
const nMessages = messages.map((i) => normP2Hash(i, htfOpts));
const nPublicKeys = publicKeys.map(normP1);
try {
const paired = [];
for (const message of new Set(nMessages)) {
const groupPublicKey = nMessages.reduce(
(groupPublicKey, subMessage, i) =>
subMessage === message ? groupPublicKey.add(nPublicKeys[i]) : groupPublicKey,
G1.ProjectivePoint.ZERO
);
// const msg = message instanceof PointG2 ? message : await PointG2.hashToCurve(message);
// Possible to batch pairing for same msg with different groupPublicKey here
paired.push(pairing(groupPublicKey, message, false));
}
paired.push(pairing(G1.ProjectivePoint.BASE.negate(), sig, false));
const product = paired.reduce((a, b) => Fp12.mul(a, b), Fp12.ONE);
const exp = Fp12.finalExponentiate(product);
return Fp12.eql(exp, Fp12.ONE);
} catch {
return false;
}
}
G1.ProjectivePoint.BASE._setWindowSize(4);
return {
getPublicKey,
sign,
verify,
verifyBatch,
aggregatePublicKeys,
aggregateSignatures,
millerLoop,
pairing,
G1,
G2,
Signature,
fields: {
Fr,
Fp,
Fp2,
Fp6,
Fp12,
},
params: {
x: CURVE.params.x,
r: CURVE.params.r,
G1b: CURVE.G1.b,
G2b: CURVE.G2.b,
},
utils,
};
}