BLS threshold m-of-n signatures

noble-curves

Audited & minimal JS implementation of elliptic curve cryptography.

🔒 Audited by independent security firms
🔻 Tree-shaking-friendly: use only what's necessary, other code won't be included
🏎 Ultra-fast, hand-optimized for caveats of JS engines
🔍 Unique tests ensure correctness: property-based, cross-library and Wycheproof vectors, fuzzing
➰ Short Weierstrass, Edwards, Montgomery curves
✍️ ECDSA, EdDSA, Schnorr, BLS signature schemes, ECDH key agreement, hashing to curves
🔖 SUF-CMA, SBS (non-repudiation), ZIP215 (consensus friendliness) features for ed25519
🧜‍♂️ Poseidon ZK-friendly hash
🪶 178KB for everything, 25KB for single-curve build

For discussions, questions and support, visit GitHub Discussions section of the repository.

This library belongs to noble cryptography

noble cryptography — high-security, easily auditable set of contained cryptographic libraries and tools.

Zero or minimal dependencies
Highly readable TypeScript / JS code
PGP-signed releases and transparent NPM builds
All libraries: ciphers, curves, hashes, post-quantum, 4kb secp256k1 / ed25519
Check out homepage for reading resources, documentation and apps built with noble

Usage

npm install @noble/curves

We support all major platforms and runtimes. For Deno, ensure to use npm specifier. For React Native, you may need a polyfill for getRandomValues. A standalone file noble-curves.js is also available.

// import * from '@noble/curves'; // Error: use sub-imports, to ensure small app size
import { secp256k1 } from '@noble/curves/secp256k1'; // ESM and Common.js
// import { secp256k1 } from 'npm:@noble/[email protected]/secp256k1'; // Deno

Implementations
Abstract API
Security
Speed
Upgrading
Contributing & testing
Resources

Implementations

Implementations use noble-hashes. If you want to use a different hashing library, abstract API doesn't depend on them.

ECDSA signature scheme

Generic example that works for all curves, shown for secp256k1:

import { secp256k1 } from '@noble/curves/secp256k1';
const priv = secp256k1.utils.randomPrivateKey();
const pub = secp256k1.getPublicKey(priv);
const msg = new Uint8Array(32).fill(1); // message hash (not message) in ecdsa
const sig = secp256k1.sign(msg, priv); // `{prehash: true}` option is available
const isValid = secp256k1.verify(sig, msg, pub) === true;

// hex strings are also supported besides Uint8Arrays:
const privHex = '46c930bc7bb4db7f55da20798697421b98c4175a52c630294d75a84b9c126236';
const pub2 = secp256k1.getPublicKey(privHex);

We support P256 (secp256r1), P384 (secp384r1), P521 (secp521r1).

ECDSA public key recovery & extra entropy

// let sig = secp256k1.Signature.fromCompact(sigHex); // or .fromDER(sigDERHex)
// sig = sig.addRecoveryBit(bit); // bit is not serialized into compact / der format
sig.recoverPublicKey(msg).toRawBytes(); // === pub; // public key recovery

// extraEntropy https://moderncrypto.org/mail-archive/curves/2017/000925.html
const sigImprovedSecurity = secp256k1.sign(msg, priv, { extraEntropy: true });

ECDH: Elliptic Curve Diffie-Hellman

// 1. The output includes parity byte. Strip it using shared.slice(1)
// 2. The output is not hashed. More secure way is sha256(shared) or hkdf(shared)
const someonesPub = secp256k1.getPublicKey(secp256k1.utils.randomPrivateKey());
const shared = secp256k1.getSharedSecret(priv, someonesPub);

Schnorr signatures over secp256k1 (BIP340)

import { schnorr } from '@noble/curves/secp256k1';
const priv = schnorr.utils.randomPrivateKey();
const pub = schnorr.getPublicKey(priv);
const msg = new TextEncoder().encode('hello');
const sig = schnorr.sign(msg, priv);
const isValid = schnorr.verify(sig, msg, pub);

ed25519, X25519, ristretto255

import { ed25519 } from '@noble/curves/ed25519';
const priv = ed25519.utils.randomPrivateKey();
const pub = ed25519.getPublicKey(priv);
const msg = new TextEncoder().encode('hello');
const sig = ed25519.sign(msg, priv);
ed25519.verify(sig, msg, pub); // Default mode: follows ZIP215
ed25519.verify(sig, msg, pub, { zip215: false }); // RFC8032 / FIPS 186-5

Default verify behavior follows ZIP215 and can be used in consensus-critical applications. It has SUF-CMA (strong unforgeability under chosen message attacks). zip215: false option switches verification criteria to strict RFC8032 / FIPS 186-5 and additionally provides non-repudiation with SBS.

X25519 follows RFC7748.

// Variants from RFC8032: with context, prehashed
import { ed25519ctx, ed25519ph } from '@noble/curves/ed25519';

// ECDH using curve25519 aka x25519
import { x25519 } from '@noble/curves/ed25519';
const priv = 'a546e36bf0527c9d3b16154b82465edd62144c0ac1fc5a18506a2244ba449ac4';
const pub = 'e6db6867583030db3594c1a424b15f7c726624ec26b3353b10a903a6d0ab1c4c';
x25519.getSharedSecret(priv, pub) === x25519.scalarMult(priv, pub); // aliases
x25519.getPublicKey(priv) === x25519.scalarMultBase(priv);
x25519.getPublicKey(x25519.utils.randomPrivateKey());

// ed25519 => x25519 conversion
import { edwardsToMontgomeryPub, edwardsToMontgomeryPriv } from '@noble/curves/ed25519';
edwardsToMontgomeryPub(ed25519.getPublicKey(ed25519.utils.randomPrivateKey()));
edwardsToMontgomeryPriv(ed25519.utils.randomPrivateKey());

ristretto255 follows irtf draft.

// hash-to-curve, ristretto255
import { utf8ToBytes } from '@noble/hashes/utils';
import { sha512 } from '@noble/hashes/sha512';
import {
  hashToCurve,
  encodeToCurve,
  RistrettoPoint,
  hashToRistretto255,
} from '@noble/curves/ed25519';

const msg = utf8ToBytes('Ristretto is traditionally a short shot of espresso coffee');
hashToCurve(msg);

const rp = RistrettoPoint.fromHex(
  '6a493210f7499cd17fecb510ae0cea23a110e8d5b901f8acadd3095c73a3b919'
);
RistrettoPoint.BASE.multiply(2n).add(rp).subtract(RistrettoPoint.BASE).toRawBytes();
RistrettoPoint.ZERO.equals(dp) === false;
// pre-hashed hash-to-curve
RistrettoPoint.hashToCurve(sha512(msg));
// full hash-to-curve including domain separation tag
hashToRistretto255(msg, { DST: 'ristretto255_XMD:SHA-512_R255MAP_RO_' });

ed448, X448, decaf448

import { ed448 } from '@noble/curves/ed448';
const priv = ed448.utils.randomPrivateKey();
const pub = ed448.getPublicKey(priv);
const msg = new TextEncoder().encode('whatsup');
const sig = ed448.sign(msg, priv);
ed448.verify(sig, msg, pub);

// Variants from RFC8032: prehashed
import { ed448ph } from '@noble/curves/ed448';

ECDH using Curve448 aka X448, follows RFC7748.

import { x448 } from '@noble/curves/ed448';
x448.getSharedSecret(priv, pub) === x448.scalarMult(priv, pub); // aliases
x448.getPublicKey(priv) === x448.scalarMultBase(priv);

// ed448 => x448 conversion
import { edwardsToMontgomeryPub } from '@noble/curves/ed448';
edwardsToMontgomeryPub(ed448.getPublicKey(ed448.utils.randomPrivateKey()));

decaf448 follows irtf draft.

import { utf8ToBytes } from '@noble/hashes/utils';
import { shake256 } from '@noble/hashes/sha3';
import { hashToCurve, encodeToCurve, DecafPoint, hashToDecaf448 } from '@noble/curves/ed448';

const msg = utf8ToBytes('Ristretto is traditionally a short shot of espresso coffee');
hashToCurve(msg);

const dp = DecafPoint.fromHex(
  'c898eb4f87f97c564c6fd61fc7e49689314a1f818ec85eeb3bd5514ac816d38778f69ef347a89fca817e66defdedce178c7cc709b2116e75'
);
DecafPoint.BASE.multiply(2n).add(dp).subtract(DecafPoint.BASE).toRawBytes();
DecafPoint.ZERO.equals(dp) === false;
// pre-hashed hash-to-curve
DecafPoint.hashToCurve(shake256(msg, { dkLen: 112 }));
// full hash-to-curve including domain separation tag
hashToDecaf448(msg, { DST: 'decaf448_XOF:SHAKE256_D448MAP_RO_' });

Same RFC7748 / RFC8032 / IRTF draft are followed.

bls12-381

See abstract/bls.

All available imports

import { secp256k1, schnorr } from '@noble/curves/secp256k1';
import { ed25519, ed25519ph, ed25519ctx, x25519, RistrettoPoint } from '@noble/curves/ed25519';
import { ed448, ed448ph, ed448ctx, x448 } from '@noble/curves/ed448';
import { p256 } from '@noble/curves/p256';
import { p384 } from '@noble/curves/p384';
import { p521 } from '@noble/curves/p521';
import { pallas, vesta } from '@noble/curves/pasta';
import { bls12_381 } from '@noble/curves/bls12-381';
import { bn254 } from '@noble/curves/bn254'; // also known as alt_bn128
import { jubjub } from '@noble/curves/jubjub';
import { bytesToHex, hexToBytes, concatBytes, utf8ToBytes } from '@noble/curves/abstract/utils';

Accessing a curve's variables

import { secp256k1 } from '@noble/curves/secp256k1';
// Every curve has `CURVE` object that contains its parameters, field, and others
console.log(secp256k1.CURVE.p); // field modulus
console.log(secp256k1.CURVE.n); // curve order
console.log(secp256k1.CURVE.a, secp256k1.CURVE.b); // equation params
console.log(secp256k1.CURVE.Gx, secp256k1.CURVE.Gy); // base point coordinates

Abstract API

Abstract API allows to define custom curves. All arithmetics is done with JS bigints over finite fields, which is defined from modular sub-module. For scalar multiplication, we use precomputed tables with w-ary non-adjacent form (wNAF). Precomputes are enabled for weierstrass and edwards BASE points of a curve. You could precompute any other point (e.g. for ECDH) using utils.precompute() method: check out examples.

weierstrass: Short Weierstrass curve

import { weierstrass } from '@noble/curves/abstract/weierstrass';
import { Field } from '@noble/curves/abstract/modular'; // finite field for mod arithmetics
import { sha256 } from '@noble/hashes/sha256'; // 3rd-party sha256() of type utils.CHash
import { hmac } from '@noble/hashes/hmac'; // 3rd-party hmac() that will accept sha256()
import { concatBytes, randomBytes } from '@noble/hashes/utils'; // 3rd-party utilities
const secq256k1 = weierstrass({
  // secq256k1: cycle of secp256k1 with Fp/N flipped.
  // https://personaelabs.org/posts/spartan-ecdsa
  // https://zcash.github.io/halo2/background/curves.html#cycles-of-curves
  a: 0n,
  b: 7n,
  Fp: Field(2n ** 256n - 432420386565659656852420866394968145599n),
  n: 2n ** 256n - 2n ** 32n - 2n ** 9n - 2n ** 8n - 2n ** 7n - 2n ** 6n - 2n ** 4n - 1n,
  Gx: 55066263022277343669578718895168534326250603453777594175500187360389116729240n,
  Gy: 32670510020758816978083085130507043184471273380659243275938904335757337482424n,
  hash: sha256,
  hmac: (key: Uint8Array, ...msgs: Uint8Array[]) => hmac(sha256, key, concatBytes(...msgs)),
  randomBytes,
});

// Replace weierstrass() with weierstrassPoints() if you don't need ECDSA, hash, hmac, randomBytes

Short Weierstrass curve's formula is y² = x³ + ax + b. weierstrass expects arguments a, b, field Fp, curve order n, cofactor h and coordinates Gx, Gy of generator point.

k generation is done deterministically, following RFC6979. For this you will need hmac & hash, which in our implementations is provided by noble-hashes. If you're using different hashing library, make sure to wrap it in the following interface:

type CHash = {
  (message: Uint8Array): Uint8Array;
  blockLen: number;
  outputLen: number;
  create(): any;
};

// example
function sha256(message: Uint8Array) { return _internal_lowlvl(message) }
sha256.outputLen = 32; // 32 bytes of output for sha2-256

Message hash is expected instead of message itself:

sign(msgHash, privKey) is default behavior, assuming you pre-hash msg with sha2, or other hash
sign(msg, privKey, {prehash: true}) option can be used if you want to pass the message itself

Weierstrass points:

Exported as ProjectivePoint
Represented in projective (homogeneous) coordinates: (x, y, z) ∋ (x=x/z, y=y/z)
Use complete exception-free formulas for addition and doubling
Can be decoded/encoded from/to Uint8Array / hex strings using ProjectivePoint.fromHex and ProjectivePoint#toRawBytes()
Have assertValidity() which checks for being on-curve
Have toAffine() and x / y getters which convert to 2d xy affine coordinates

// `weierstrassPoints()` returns `CURVE` and `ProjectivePoint`
// `weierstrass()` returns `CurveFn`
type SignOpts = { lowS?: boolean; prehash?: boolean; extraEntropy: boolean | Uint8Array };
type CurveFn = {
  CURVE: ReturnType<typeof validateOpts>;
  getPublicKey: (privateKey: PrivKey, isCompressed?: boolean) => Uint8Array;
  getSharedSecret: (privateA: PrivKey, publicB: Hex, isCompressed?: boolean) => Uint8Array;
  sign: (msgHash: Hex, privKey: PrivKey, opts?: SignOpts) => SignatureType;
  verify: (
    signature: Hex | SignatureType,
    msgHash: Hex,
    publicKey: Hex,
    opts?: { lowS?: boolean; prehash?: boolean }
  ) => boolean;
  ProjectivePoint: ProjectivePointConstructor;
  Signature: SignatureConstructor;
  utils: {
    normPrivateKeyToScalar: (key: PrivKey) => bigint;
    isValidPrivateKey(key: PrivKey): boolean;
    randomPrivateKey: () => Uint8Array;
    precompute: (windowSize?: number, point?: ProjPointType<bigint>) => ProjPointType<bigint>;
  };
};

// T is usually bigint, but can be something else like complex numbers in BLS curves
interface ProjPointType<T> extends Group<ProjPointType<T>> {
  readonly px: T;
  readonly py: T;
  readonly pz: T;
  get x(): bigint;
  get y(): bigint;
  multiply(scalar: bigint): ProjPointType<T>;
  multiplyUnsafe(scalar: bigint): ProjPointType<T>;
  multiplyAndAddUnsafe(Q: ProjPointType<T>, a: bigint, b: bigint): ProjPointType<T> | undefined;
  toAffine(iz?: T): AffinePoint<T>;
  isTorsionFree(): boolean;
  clearCofactor(): ProjPointType<T>;
  assertValidity(): void;
  hasEvenY(): boolean;
  toRawBytes(isCompressed?: boolean): Uint8Array;
  toHex(isCompressed?: boolean): string;
}
// Static methods for 3d XYZ points
interface ProjConstructor<T> extends GroupConstructor<ProjPointType<T>> {
  new (x: T, y: T, z: T): ProjPointType<T>;
  fromAffine(p: AffinePoint<T>): ProjPointType<T>;
  fromHex(hex: Hex): ProjPointType<T>;
  fromPrivateKey(privateKey: PrivKey): ProjPointType<T>;
}

ECDSA signatures are represented by Signature instances and can be described by the interface:

interface SignatureType {
  readonly r: bigint;
  readonly s: bigint;
  readonly recovery?: number;
  assertValidity(): void;
  addRecoveryBit(recovery: number): SignatureType;
  hasHighS(): boolean;
  normalizeS(): SignatureType;
  recoverPublicKey(msgHash: Hex): ProjPointType<bigint>;
  toCompactRawBytes(): Uint8Array;
  toCompactHex(): string;
  // DER-encoded
  toDERRawBytes(): Uint8Array;
  toDERHex(): string;
}
type SignatureConstructor = {
  new (r: bigint, s: bigint): SignatureType;
  fromCompact(hex: Hex): SignatureType;
  fromDER(hex: Hex): SignatureType;
};

More examples:

// All curves expose same generic interface.
const priv = secq256k1.utils.randomPrivateKey();
secq256k1.getPublicKey(priv); // Convert private key to public.
const sig = secq256k1.sign(msg, priv); // Sign msg with private key.
const sig2 = secq256k1.sign(msg, priv, { prehash: true }); // hash(msg)
secq256k1.verify(sig, msg, priv); // Verify if sig is correct.

const Point = secq256k1.ProjectivePoint;
const point = Point.BASE; // Elliptic curve Point class and BASE point static var.
point.add(point).equals(point.double()); // add(), equals(), double() methods
point.subtract(point).equals(Point.ZERO); // subtract() method, ZERO static var
point.negate(); // Flips point over x/y coordinate.
point.multiply(31415n); // Multiplication of Point by scalar.

point.assertValidity(); // Checks for being on-curve
point.toAffine(); // Converts to 2d affine xy coordinates

secq256k1.CURVE.n;
secq256k1.CURVE.p;
secq256k1.CURVE.Fp.mod();
secq256k1.CURVE.hash();

// precomputes
const fast = secq256k1.utils.precompute(8, Point.fromHex(someonesPubKey));
fast.multiply(privKey); // much faster ECDH now

edwards: Twisted Edwards curve

import { twistedEdwards } from '@noble/curves/abstract/edwards';
import { Field } from '@noble/curves/abstract/modular';
import { sha512 } from '@noble/hashes/sha512';
import { randomBytes } from '@noble/hashes/utils';

const Fp = Field(2n ** 255n - 19n);
const ed25519 = twistedEdwards({
  a: Fp.create(-1n),
  d: Fp.div(-121665n, 121666n), // -121665n/121666n mod p
  Fp: Fp,
  n: 2n ** 252n + 27742317777372353535851937790883648493n,
  h: 8n,
  Gx: 15112221349535400772501151409588531511454012693041857206046113283949847762202n,
  Gy: 46316835694926478169428394003475163141307993866256225615783033603165251855960n,
  hash: sha512,
  randomBytes,
  adjustScalarBytes(bytes) {
    // optional; but mandatory in ed25519
    bytes[0] &= 248;
    bytes[31] &= 127;
    bytes[31] |= 64;
    return bytes;
  },
} as const);

Twisted Edwards curve's formula is ax² + y² = 1 + dx²y². You must specify a, d, field Fp, order n, cofactor h and coordinates Gx, Gy of generator point.

For EdDSA signatures, hash param required. adjustScalarBytes which instructs how to change private scalars could be specified.

We support non-repudiation, which help in following scenarios:

Contract Signing: if A signed an agreement with B using key that allows repudiation, it can later claim that it signed a different contract
E-voting: malicious voters may pick keys that allow repudiation in order to deny results
Blockchains: transaction of amount X might also be valid for a different amount Y

Edwards points:

Exported as ExtendedPoint
Represented in extended coordinates: (x, y, z, t) ∋ (x=x/z, y=y/z)
Use complete exception-free formulas for addition and doubling
Can be decoded/encoded from/to Uint8Array / hex strings using ExtendedPoint.fromHex and ExtendedPoint#toRawBytes()
Have assertValidity() which checks for being on-curve
Have toAffine() and x / y getters which convert to 2d xy affine coordinates
Have isTorsionFree(), clearCofactor() and isSmallOrder() utilities to handle torsions

// `twistedEdwards()` returns `CurveFn` of following type:
type CurveFn = {
  CURVE: ReturnType<typeof validateOpts>;
  getPublicKey: (privateKey: Hex) => Uint8Array;
  sign: (message: Hex, privateKey: Hex, context?: Hex) => Uint8Array;
  verify: (sig: SigType, message: Hex, publicKey: Hex, context?: Hex) => boolean;
  ExtendedPoint: ExtPointConstructor;
  utils: {
    randomPrivateKey: () => Uint8Array;
    getExtendedPublicKey: (key: PrivKey) => {
      head: Uint8Array;
      prefix: Uint8Array;
      scalar: bigint;
      point: PointType;
      pointBytes: Uint8Array;
    };
  };
};

interface ExtPointType extends Group<ExtPointType> {
  readonly ex: bigint;
  readonly ey: bigint;
  readonly ez: bigint;
  readonly et: bigint;
  get x(): bigint;
  get y(): bigint;
  assertValidity(): void;
  multiply(scalar: bigint): ExtPointType;
  multiplyUnsafe(scalar: bigint): ExtPointType;
  isSmallOrder(): boolean;
  isTorsionFree(): boolean;
  clearCofactor(): ExtPointType;
  toAffine(iz?: bigint): AffinePoint<bigint>;
  toRawBytes(isCompressed?: boolean): Uint8Array;
  toHex(isCompressed?: boolean): string;
}
// Static methods of Extended Point with coordinates in X, Y, Z, T
interface ExtPointConstructor extends GroupConstructor<ExtPointType> {
  new (x: bigint, y: bigint, z: bigint, t: bigint): ExtPointType;
  fromAffine(p: AffinePoint<bigint>): ExtPointType;
  fromHex(hex: Hex): ExtPointType;
  fromPrivateKey(privateKey: Hex): ExtPointType;
}

montgomery: Montgomery curve

import { montgomery } from '@noble/curves/abstract/montgomery';
import { Field } from '@noble/curves/abstract/modular';

const x25519 = montgomery({
  a: 486662n,
  Gu: 9n,
  P: 2n ** 255n - 19n,
  montgomeryBits: 255,
  nByteLength: 32,
  // Optional param
  adjustScalarBytes(bytes) {
    bytes[0] &= 248;
    bytes[31] &= 127;
    bytes[31] |= 64;
    return bytes;
  },
});

The module contains methods for x-only ECDH on Curve25519 / Curve448 from RFC7748. Proper Elliptic Curve Points are not implemented yet.

You must specify curve params Fp, a, Gu coordinate of u, montgomeryBits and nByteLength.

bls: Barreto-Lynn-Scott curves

The module abstracts BLS (Barreto-Lynn-Scott) pairing-friendly elliptic curve construction. They allow to construct zk-SNARKs and use aggregated, batch-verifiable threshold signatures, using Boneh-Lynn-Shacham signature scheme.

The module doesn't expose CURVE property: use G1.CURVE, G2.CURVE instead. Only BLS12-381 is implemented currently. Defining BLS12-377 and BLS24 should be straightforward.

Main methods and properties are:

getPublicKey(privateKey)
sign(message, privateKey)
verify(signature, message, publicKey)
aggregatePublicKeys(publicKeys)
aggregateSignatures(signatures)
G1 and G2 curves containing CURVE and ProjectivePoint
Signature property with fromHex, toHex methods
fields containing Fp, Fp2, Fp6, Fp12, Fr

The default BLS uses short public keys (with public keys in G1 and signatures in G2). Short signatures (public keys in G2 and signatures in G1) is also supported, using:

getPublicKeyForShortSignatures(privateKey)
signShortSignature(message, privateKey)
verifyShortSignature(signature, message, publicKey)
aggregateShortSignatures(signatures)

import { bls12_381 as bls } from '@noble/curves/bls12-381';
const privateKey = '67d53f170b908cabb9eb326c3c337762d59289a8fec79f7bc9254b584b73265c';
const message = '64726e3da8';
const publicKey = bls.getPublicKey(privateKey);
const signature = bls.sign(message, privateKey);
const isValid = bls.verify(signature, message, publicKey);
console.log({ publicKey, signature, isValid });

// Use custom DST, e.g. for Ethereum consensus layer
const htfEthereum = {DST: 'BLS_SIG_BLS12381G2_XMD:SHA-256_SSWU_RO_POP_'};
const signatureEth = bls.sign(message, privateKey, htfEthereum);
const isValidEth = bls.verify(signature, message, publicKey, htfEthereum);
console.log({ signatureEth, isValidEth });

// Sign 1 msg with 3 keys
const privateKeys = [
  '18f020b98eb798752a50ed0563b079c125b0db5dd0b1060d1c1b47d4a193e1e4',
  'ed69a8c50cf8c9836be3b67c7eeff416612d45ba39a5c099d48fa668bf558c9c',
  '16ae669f3be7a2121e17d0c68c05a8f3d6bef21ec0f2315f1d7aec12484e4cf5',
];
const messages = ['d2', '0d98', '05caf3'];
const publicKeys = privateKeys.map(bls.getPublicKey);
const signatures2 = privateKeys.map((p) => bls.sign(message, p));
const aggPubKey2 = bls.aggregatePublicKeys(publicKeys);
const aggSignature2 = bls.aggregateSignatures(signatures2);
const isValid2 = bls.verify(aggSignature2, message, aggPubKey2);
console.log({ signatures2, aggSignature2, isValid2 });

// Sign 3 msgs with 3 keys
const signatures3 = privateKeys.map((p, i) => bls.sign(messages[i], p));
const aggSignature3 = bls.aggregateSignatures(signatures3);
const isValid3 = bls.verifyBatch(aggSignature3, messages, publicKeys);
console.log({ publicKeys, signatures3, aggSignature3, isValid3 });

// Pairings, with and without final exponentiation
bls.pairing(PointG1, PointG2);
bls.pairing(PointG1, PointG2, false);
bls.fields.Fp12.finalExponentiate(bls.fields.Fp12.mul(PointG1, PointG2));

// Others
bls.G1.ProjectivePoint.BASE, bls.G2.ProjectivePoint.BASE
bls.fields.Fp, bls.fields.Fp2, bls.fields.Fp12, bls.fields.Fr
bls.params.x, bls.params.r, bls.params.G1b, bls.params.G2b

// hash-to-curve examples can be seen below

hash-to-curve: Hashing strings to curve points

The module allows to hash arbitrary strings to elliptic curve points. Implements RFC 9380.

Every curve has exported hashToCurve and encodeToCurve methods. You should always prefer hashToCurve for security:

import { hashToCurve, encodeToCurve } from '@noble/curves/secp256k1';
import { randomBytes } from '@noble/hashes/utils';
hashToCurve('0102abcd');
console.log(hashToCurve(randomBytes()));
console.log(encodeToCurve(randomBytes()));

import { bls12_381 } from '@noble/curves/bls12-381';
bls12_381.G1.hashToCurve(randomBytes(), { DST: 'another' });
bls12_381.G2.hashToCurve(randomBytes(), { DST: 'custom' });

Low-level methods from the spec:

// produces a uniformly random byte string using a cryptographic hash function H that outputs b bits.
function expand_message_xmd(
  msg: Uint8Array,
  DST: Uint8Array,
  lenInBytes: number,
  H: CHash // For CHash see abstract/weierstrass docs section
): Uint8Array;
// produces a uniformly random byte string using an extendable-output function (XOF) H.
function expand_message_xof(
  msg: Uint8Array,
  DST: Uint8Array,
  lenInBytes: number,
  k: number,
  H: CHash
): Uint8Array;
// Hashes arbitrary-length byte strings to a list of one or more elements of a finite field F
function hash_to_field(msg: Uint8Array, count: number, options: Opts): bigint[][];

/**
 * * `DST` is a domain separation tag, defined in section 2.2.5
 * * `p` characteristic of F, where F is a finite field of characteristic p and order q = p^m
 * * `m` is extension degree (1 for prime fields)
 * * `k` is the target security target in bits (e.g. 128), from section 5.1
 * * `expand` is `xmd` (SHA2, SHA3, BLAKE) or `xof` (SHAKE, BLAKE-XOF)
 * * `hash` conforming to `utils.CHash` interface, with `outputLen` / `blockLen` props
 */
type UnicodeOrBytes = string | Uint8Array;
type Opts = {
  DST: UnicodeOrBytes;
  p: bigint;
  m: number;
  k: number;
  expand?: 'xmd' | 'xof';
  hash: CHash;
};

poseidon: Poseidon hash

Implements Poseidon ZK-friendly hash.

There are many poseidon variants with different constants. We don't provide them: you should construct them manually. Check out micro-starknet package for a proper example.

import { poseidon } from '@noble/curves/abstract/poseidon';

type PoseidonOpts = {
  Fp: Field<bigint>;
  t: number;
  roundsFull: number;
  roundsPartial: number;
  sboxPower?: number;
  reversePartialPowIdx?: boolean;
  mds: bigint[][];
  roundConstants: bigint[][];
};
const instance = poseidon(opts: PoseidonOpts);

modular: Modular arithmetics utilities

import * as mod from '@noble/curves/abstract/modular';
const fp = mod.Field(2n ** 255n - 19n); // Finite field over 2^255-19
fp.mul(591n, 932n); // multiplication
fp.pow(481n, 11024858120n); // exponentiation
fp.div(5n, 17n); // division: 5/17 mod 2^255-19 == 5 * invert(17)
fp.sqrt(21n); // square root

// Generic non-FP utils are also available
mod.mod(21n, 10n); // 21 mod 10 == 1n; fixed version of 21 % 10
mod.invert(17n, 10n); // invert(17) mod 10; modular multiplicative inverse
mod.invertBatch([1n, 2n, 4n], 21n); // => [1n, 11n, 16n] in one inversion

Field operations are not constant-time: they are using JS bigints, see security. The fact is mostly irrelevant, but the important method to keep in mind is pow, which may leak exponent bits, when used naïvely.

mod.Field is always field over prime. Non-prime fields aren't supported for now. We don't test for prime-ness for speed and because algorithms are probabilistic anyway. Initializing a non-prime field could make your app suspectible to DoS (infilite loop) on Tonelli-Shanks square root calculation.

Unlike mod.invert, mod.invertBatch won't throw on 0: make sure to throw an error yourself.

Creating private keys from hashes

You can't simply make a 32-byte private key from a 32-byte hash. Doing so will make the key biased.

To make the bias negligible, we follow FIPS 186-5 A.2 and RFC 9380. This means, for 32-byte key, we would need 48-byte hash to get 2^-128 bias, which matches curve security level.

hashToPrivateScalar() that hashes to private key was created for this purpose. Use abstract/hash-to-curve if you need to hash to public key.

import { p256 } from '@noble/curves/p256';
import { sha256 } from '@noble/hashes/sha256';
import { hkdf } from '@noble/hashes/hkdf';
import * as mod from '@noble/curves/abstract/modular';
const someKey = new Uint8Array(32).fill(2); // Needs to actually be random, not .fill(2)
const derived = hkdf(sha256, someKey, undefined, 'application', 48); // 48 bytes for 32-byte priv
const validPrivateKey = mod.hashToPrivateScalar(derived, p256.CURVE.n);

utils: Useful utilities

import * as utils from '@noble/curves/abstract/utils';

utils.bytesToHex(Uint8Array.from([0xde, 0xad, 0xbe, 0xef]));
utils.hexToBytes('deadbeef');
utils.numberToHexUnpadded(123n);
utils.hexToNumber();

utils.bytesToNumberBE(Uint8Array.from([0xde, 0xad, 0xbe, 0xef]));
utils.bytesToNumberLE(Uint8Array.from([0xde, 0xad, 0xbe, 0xef]));
utils.numberToBytesBE(123n, 32);
utils.numberToBytesLE(123n, 64);

utils.concatBytes(Uint8Array.from([0xde, 0xad]), Uint8Array.from([0xbe, 0xef]));
utils.nLength(255n);
utils.equalBytes(Uint8Array.from([0xde]), Uint8Array.from([0xde]));

Security

The library has been independently audited:

at version 1.2.0, in Sep 2023, by Kudelski Security
- PDFs: offline
- Changes since audit
- Scope: scure-starknet and its related abstract modules of noble-curves: curve, modular, poseidon, weierstrass
- The audit has been funded by Starkware
at version 0.7.3, in Feb 2023, by Trail of Bits
- PDFs: online, offline
- Changes since audit
- Scope: abstract modules curve, hash-to-curve, modular, poseidon, utils, weierstrass and top-level modules _shortw_utils and secp256k1
- The audit has been funded by Ryan Shea

It is tested against property-based, cross-library and Wycheproof vectors, and has fuzzing by Guido Vranken's cryptofuzz.

If you see anything unusual: investigate and report.

Constant-timeness

JIT-compiler and Garbage Collector make "constant time" extremely hard to achieve timing attack resistance in a scripting language. Which means any other JS library can't have constant-timeness. Even statically typed Rust, a language without GC, makes it harder to achieve constant-time for some cases. If your goal is absolute security, don't use any JS lib — including bindings to native ones. Use low-level libraries & languages. Nonetheless we're targetting algorithmic constant time.

Supply chain security

Commits are signed with PGP keys, to prevent forgery. Make sure to verify commit signatures.
Releases are transparent and built on GitHub CI. Make sure to verify provenance logs
Rare releasing is followed to ensure less re-audit need for end-users
Dependencies are minimized and locked-down:
- If your app has 500 dependencies, any dep could get hacked and you'll be downloading malware with every install. We make sure to use as few dependencies as possible
- We prevent automatic dependency updates by locking-down version ranges. Every update is checked with npm-diff
- One dependency noble-hashes is used, by the same author, to provide hashing functionality
Dev Dependencies are only used if you want to contribute to the repo. They are disabled for end-users:
- scure-base, scure-bip32, scure-bip39, micro-bmark and micro-should are developed by the same author and follow identical security practices
- prettier (linter), fast-check (property-based testing) and typescript are used for code quality, vector generation and ts compilation. The packages are big, which makes it hard to audit their source code thoroughly and fully

Randomness

We're deferring to built-in crypto.getRandomValues which is considered cryptographically secure (CSPRNG).

In the past, browsers had bugs that made it weak: it may happen again. Implementing a userspace CSPRNG to get resilient to the weakness is even worse: there is no reliable userspace source of quality entropy.

Speed

Benchmark results on Apple M2 with node v20:

secp256k1
init x 68 ops/sec @ 14ms/op
getPublicKey x 6,750 ops/sec @ 148μs/op
sign x 5,206 ops/sec @ 192μs/op
verify x 880 ops/sec @ 1ms/op
getSharedSecret x 536 ops/sec @ 1ms/op
recoverPublicKey x 852 ops/sec @ 1ms/op
schnorr.sign x 685 ops/sec @ 1ms/op
schnorr.verify x 908 ops/sec @ 1ms/op

p256
init x 38 ops/sec @ 26ms/op
getPublicKey x 6,530 ops/sec @ 153μs/op
sign x 5,074 ops/sec @ 197μs/op
verify x 626 ops/sec @ 1ms/op

p384
init x 17 ops/sec @ 57ms/op
getPublicKey x 2,883 ops/sec @ 346μs/op
sign x 2,358 ops/sec @ 424μs/op
verify x 245 ops/sec @ 4ms/op

p521
init x 9 ops/sec @ 109ms/op
getPublicKey x 1,516 ops/sec @ 659μs/op
sign x 1,271 ops/sec @ 786μs/op
verify x 123 ops/sec @ 8ms/op

ed25519
init x 54 ops/sec @ 18ms/op
getPublicKey x 10,269 ops/sec @ 97μs/op
sign x 5,110 ops/sec @ 195μs/op
verify x 1,049 ops/sec @ 952μs/op

ed448
init x 19 ops/sec @ 51ms/op
getPublicKey x 3,775 ops/sec @ 264μs/op
sign x 1,771 ops/sec @ 564μs/op
verify x 351 ops/sec @ 2ms/op

ecdh
├─x25519 x 1,466 ops/sec @ 682μs/op
├─secp256k1 x 539 ops/sec @ 1ms/op
├─p256 x 511 ops/sec @ 1ms/op
├─p384 x 199 ops/sec @ 5ms/op
├─p521 x 103 ops/sec @ 9ms/op
└─x448 x 548 ops/sec @ 1ms/op

bls12-381
init x 36 ops/sec @ 27ms/op
getPublicKey 1-bit x 973 ops/sec @ 1ms/op
getPublicKey x 970 ops/sec @ 1ms/op
sign x 55 ops/sec @ 17ms/op
verify x 39 ops/sec @ 25ms/op
pairing x 106 ops/sec @ 9ms/op
aggregatePublicKeys/8 x 129 ops/sec @ 7ms/op
aggregatePublicKeys/32 x 34 ops/sec @ 28ms/op
aggregatePublicKeys/128 x 8 ops/sec @ 112ms/op
aggregatePublicKeys/512 x 2 ops/sec @ 446ms/op
aggregatePublicKeys/2048 x 0 ops/sec @ 1778ms/op
aggregateSignatures/8 x 50 ops/sec @ 19ms/op
aggregateSignatures/32 x 13 ops/sec @ 74ms/op
aggregateSignatures/128 x 3 ops/sec @ 296ms/op
aggregateSignatures/512 x 0 ops/sec @ 1180ms/op
aggregateSignatures/2048 x 0 ops/sec @ 4715ms/op

hash-to-curve
hash_to_field x 91,600 ops/sec @ 10μs/op
secp256k1 x 2,373 ops/sec @ 421μs/op
p256 x 4,310 ops/sec @ 231μs/op
p384 x 1,664 ops/sec @ 600μs/op
p521 x 807 ops/sec @ 1ms/op
ed25519 x 3,088 ops/sec @ 323μs/op
ed448 x 1,247 ops/sec @ 801μs/op

Upgrading

Previously, the library was split into single-feature packages noble-secp256k1, noble-ed25519 and noble-bls12-381.

Curves continue their original work. The single-feature packages changed their direction towards providing minimal 4kb implementations of cryptography, which means they have less features.

Upgrading from noble-secp256k1 2.0 or noble-ed25519 2.0: no changes, libraries are compatible.

Upgrading from noble-secp256k1 1.7:

getPublicKey
- now produce 33-byte compressed signatures by default
- to use old behavior, which produced 65-byte uncompressed keys, set argument isCompressed to false: getPublicKey(priv, false)
sign
- is now sync
- now returns Signature instance with { r, s, recovery } properties
- canonical option was renamed to lowS
- recovered option has been removed because recovery bit is always returned now
- der option has been removed. There are 2 options:
  1. Use compact encoding: fromCompact, toCompactRawBytes, toCompactHex. Compact encoding is simply a concatenation of 32-byte r and 32-byte s.
  2. If you must use DER encoding, switch to noble-curves (see above).
verify
- is now sync
- strict option was renamed to lowS
getSharedSecret
- now produce 33-byte compressed signatures by default
- to use old behavior, which produced 65-byte uncompressed keys, set argument isCompressed to false: getSharedSecret(a, b, false)
recoverPublicKey(msg, sig, rec) was changed to sig.recoverPublicKey(msg)
number type for private keys have been removed: use bigint instead
Point (2d xy) has been changed to ProjectivePoint (3d xyz)
utils were split into utils (same api as in noble-curves) and etc (hmacSha256Sync and others)

Upgrading from @noble/ed25519 1.7:

Methods are now sync by default
bigint is no longer allowed in getPublicKey, sign, verify. Reason: ed25519 is LE, can lead to bugs
Point (2d xy) has been changed to ExtendedPoint (xyzt)
Signature was removed: just use raw bytes or hex now
utils were split into utils (same api as in noble-curves) and etc (sha512Sync and others)
getSharedSecret was moved to x25519 module
toX25519 has been moved to edwardsToMontgomeryPub and edwardsToMontgomeryPriv methods

Upgrading from @noble/bls12-381:

Methods and classes were renamed:
- PointG1 -> G1.Point, PointG2 -> G2.Point
- PointG2.fromSignature -> Signature.decode, PointG2.toSignature -> Signature.encode
Fp2 ORDER was corrected

Contributing & testing

Clone the repository
npm install to install build dependencies like TypeScript
npm run build to compile TypeScript code
npm run test will execute all main tests

Resources

Check out paulmillr.com/noble for useful resources, articles, documentation and demos related to the library.

License

The MIT License (MIT)

See LICENSE file.

	should(`produce correct scalars (${SCALAR_VECTORS.length} vectors)`, () => {
	const options = {
	p: bls.CURVE.r,
	m: 1,
	expand: undefined,
	};
	for (let vector of SCALAR_VECTORS) {
	const [okmAscii, expectedHex] = vector;
	const expected = BigInt('0x' + expectedHex);
	const okm = utf8ToBytes(okmAscii);
	const scalars = hash_to_field(okm, 1, Object.assign({}, bls.CURVE.htfDefaults, options));
	deepStrictEqual(scalars[0][0], expected);

	* @param msg a byte string containing the message to hash
	* @param count the number of elements of F to output
	* @param options `{DST: string, p: bigint, m: number, k: number, expand: 'xmd' \| 'xof', hash: H}`
	* @returns [u_0, ..., u_(count - 1)], a list of field elements.
	*/
	export function hash_to_field(msg: Uint8Array, count: number, options: Opts): bigint[][] {
	const { p, k, m, hash, expand, DST: _DST } = options;
	isBytes(msg);
	isNum(count);
	if (typeof _DST !== 'string') throw new Error('DST must be valid');
	const log2p = p.toString(2).length;
	const L = Math.ceil((log2p + k) / 8); // section 5.1 of ietf draft link above
	const len_in_bytes = count * m * L;
	const DST = utf8ToBytes(_DST);
	const pseudo_random_bytes =
	expand === 'xmd'
	? expand_message_xmd(msg, DST, len_in_bytes, hash)
	: expand === 'xof'
	? expand_message_xof(msg, DST, len_in_bytes, k, hash)
	: msg;

	if (ent != null) {
	// K = HMAC_K(V \|\| 0x00 \|\| int2octets(x) \|\| bits2octets(h1) \|\| k')
	const e = ent === true ? randomBytes(Fp.BYTES) : ent; // generate random bytes OR pass as-is
	seedArgs.push(ensureBytes('extraEntropy', e, Fp.BYTES)); // check for being of size BYTES
	}

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