paulmillr/noble-secp256k1

noble-secp256k1

Fastest 5KB JS implementation of secp256k1 signatures & ECDH.

• ✍️ ECDSA signatures compliant with RFC6979
• ➰ Schnorr signatures compliant with BIP340
• 🤝 Elliptic Curve Diffie-Hellman ECDH
• 🔒 Supports hedged signatures guarding against fault attacks
• 🪶 4.94KB (gzipped) - 10-25x smaller than similar libraries

The module is a sister project of noble-curves. Use noble-secp256k1 if you need smaller attack surface & better auditability. Switch to noble-curves (drop-in) if you need features like MSM, DER encoding, custom point precomputes.

898-byte version of the library is available for learning purposes in test/misc/1kb.min.js, it was created for the article Learning fast elliptic-curve cryptography.

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, 5kb secp256k1 / ed25519
• WASM version: awasm-noble
• Check out the homepage for reading resources, documentation, and apps built with noble

Usage

npm install @noble/secp256k1

deno add jsr:@noble/secp256k1

We support all major platforms and runtimes. For React Native, additional polyfills are needed: see below.

import * as secp from '@noble/secp256k1';
(async () => {
  const { secretKey, publicKey } = secp.keygen();
  // const publicKey = secp.getPublicKey(secretKey);
  const msg = new TextEncoder().encode('hello noble');
  const sig = await secp.signAsync(msg, secretKey);
  const isValid = await secp.verifyAsync(sig, msg, publicKey);
})();

// ECDH, key recovery
(async () => {
  const alice = secp.keygen();
  const bob = secp.keygen();
  const shared = secp.getSharedSecret(alice.secretKey, bob.publicKey);
  const msg = new TextEncoder().encode('hello noble');

  // recovery
  const sigr = await secp.signAsync(msg, alice.secretKey, { format: 'recovered' });
  const publicKey2 = await secp.recoverPublicKeyAsync(sigr, msg);
})();

// Schnorr signatures from BIP340
(async () => {
  const schnorr = secp.schnorr;
  const { secretKey, publicKey } = schnorr.keygen();
  const msg = new TextEncoder().encode('hello noble');
  const sig = await schnorr.signAsync(msg, secretKey);
  const isValid = await schnorr.verifyAsync(sig, msg, publicKey);
})();

Enabling synchronous methods

Only async methods are available by default, to keep the library dependency-free. To enable sync methods:

npm install @noble/hashes

import * as secp from '@noble/secp256k1';
import { hmac } from '@noble/hashes/hmac.js';
import { sha256 } from '@noble/hashes/sha2.js';
secp.hashes.hmacSha256 = (key, msg) => hmac(sha256, key, msg);
secp.hashes.sha256 = sha256;

React Native: polyfill getRandomValues and sha256

React Native does not provide secure getRandomValues by default. This can't be securely polyfilled from our end, so one will need a RN-specific compile-time dep.

import 'react-native-get-random-values';
import * as secp from '@noble/secp256k1';
import { hmac } from '@noble/hashes/hmac.js';
import { sha256 } from '@noble/hashes/sha2.js';
secp.hashes.hmacSha256 = (key, msg) => hmac(sha256, key, msg);
secp.hashes.sha256 = sha256;
secp.hashes.hmacSha256Async = async (key, msg) => hmac(sha256, key, msg);
secp.hashes.sha256Async = async (msg) => sha256(msg);

API

There are 4 main methods, which accept Uint8Array-s:

• keygen()
• getPublicKey(secretKey)
• sign(messageHash, secretKey) and signAsync(messageHash, secretKey)
• verify(signature, messageHash, publicKey) and verifyAsync(signature, messageHash, publicKey)

keygen

import * as secp from '@noble/secp256k1';
(async () => {
  const keys = secp.keygen();
  const { secretKey, publicKey } = keys;
})();

getPublicKey

import * as secp from '@noble/secp256k1';
const secretKey = secp.utils.randomSecretKey();
const pubKey33b = secp.getPublicKey(secretKey);

// Variants
const pubKey65b = secp.getPublicKey(secretKey, false);
const pubKeyPoint = secp.Point.fromBytes(pubKey65b);
const samePoint = pubKeyPoint.toBytes();

Generates 33-byte compressed (default) or 65-byte public key from 32-byte private key.

sign

import * as secp from '@noble/secp256k1';
import { hmac } from '@noble/hashes/hmac.js';
import { sha256 } from '@noble/hashes/sha2.js';
import { keccak_256 } from '@noble/hashes/sha3.js';
secp.hashes.hmacSha256 = (key, msg) => hmac(sha256, key, msg);
secp.hashes.sha256 = sha256;
const { secretKey } = secp.keygen();
const msg = new TextEncoder().encode('hello noble');
const sig = secp.sign(msg, secretKey);

// async
const sigB = await secp.signAsync(msg, secretKey);

// recovered, allows `recoverPublicKey(sigR, msg)`
const sigR = secp.sign(msg, secretKey, { format: 'recovered' });
const sigH = secp.sign(keccak_256(msg), secretKey, { prehash: false });
// hedged sig
const sigC = secp.sign(msg, secretKey, { extraEntropy: true });
const sigC2 = secp.sign(msg, secretKey, { extraEntropy: Uint8Array.from([0xca, 0xfe]) });
// malleable sig
const sigD = secp.sign(msg, secretKey, { lowS: false });

Generates low-s deterministic-k RFC6979 ECDSA signature.

• Message will be hashed with sha256. If you want to use a different hash function, make sure to use { prehash: false }.
• extraEntropy: true enables hedged signatures. They incorporate extra randomness into RFC6979 (described in section 3.6), to provide additional protection against fault attacks. Check out blog post Deterministic signatures are not your friends. Even if their RNG is broken, they will fall back to determinism.
• Default behavior lowS: true prohibits signatures which have (sig.s >= CURVE.n/2n) and is compatible with BTC/ETH. Setting lowS: false allows to create malleable signatures, which is default openssl behavior. Non-malleable signatures can still be successfully verified in openssl.

verify

import * as secp from '@noble/secp256k1';
import { hmac } from '@noble/hashes/hmac.js';
import { sha256 } from '@noble/hashes/sha2.js';
import { keccak_256 } from '@noble/hashes/sha3.js';
secp.hashes.hmacSha256 = (key, msg) => hmac(sha256, key, msg);
secp.hashes.sha256 = sha256;
const { secretKey, publicKey } = secp.keygen();
const msg = new TextEncoder().encode('hello noble');
const sig = secp.sign(msg, secretKey);
const isValid = secp.verify(sig, msg, publicKey);

const sigH = secp.sign(keccak_256(msg), secretKey, { prehash: false });

Verifies ECDSA signature.

• Message will be hashed with sha256. If you want to use a different hash function, make sure to use { prehash: false }.
• Default behavior lowS: true prohibits malleable signatures which have (sig.s >= CURVE.n/2n) and is compatible with BTC / ETH. Setting lowS: false allows to create signatures, which is default openssl behavior.

getSharedSecret

import * as secp from '@noble/secp256k1';
const alice = secp.keygen();
const bob = secp.keygen();
const shared33b = secp.getSharedSecret(alice.secretKey, bob.publicKey);
const shared65b = secp.getSharedSecret(bob.secretKey, alice.publicKey, false);
const sharedPoint = secp.Point.fromBytes(bob.publicKey).multiply(
  secp.etc.secretKeyToScalar(alice.secretKey)
);

Computes ECDH (Elliptic Curve Diffie-Hellman) shared secret between key A and different key B.

recoverPublicKey

import * as secp from '@noble/secp256k1';
import { hmac } from '@noble/hashes/hmac.js';
import { sha256 } from '@noble/hashes/sha2.js';
import { keccak_256 } from '@noble/hashes/sha3.js';
secp.hashes.hmacSha256 = (key, msg) => hmac(sha256, key, msg);
secp.hashes.sha256 = sha256;

const { secretKey, publicKey } = secp.keygen();
const msg = new TextEncoder().encode('hello noble');
const sigR = secp.sign(msg, secretKey, { format: 'recovered' });
const publicKey2 = secp.recoverPublicKey(sigR, msg);

const sigRH = secp.sign(keccak_256(msg), secretKey, { format: 'recovered', prehash: false });
const publicKeyH = secp.recoverPublicKey(sigRH, keccak_256(msg), { prehash: false });

Recover public key from Signature instance with recovery bit set.

schnorr

import * as secp from '@noble/secp256k1';
import { schnorr } from '@noble/secp256k1';
import { hmac } from '@noble/hashes/hmac.js';
import { sha256 } from '@noble/hashes/sha2.js';
secp.hashes.hmacSha256 = (key, msg) => hmac(sha256, key, msg);
secp.hashes.sha256 = sha256;
const { secretKey, publicKey } = schnorr.keygen();
const msg = new TextEncoder().encode('hello noble');
const sig = schnorr.sign(msg, secretKey);
const isValid = schnorr.verify(sig, msg, publicKey);

Async methods work without extra setup:

import { schnorr } from '@noble/secp256k1';
const { secretKey, publicKey } = schnorr.keygen();
const msg = new TextEncoder().encode('hello noble');
const sigA = await schnorr.signAsync(msg, secretKey);
const isValidA = await schnorr.verifyAsync(sigA, msg, publicKey);

Schnorr signatures compliant with BIP340 are supported.

utils

A bunch of useful utilities are also exposed:

import * as secp from '@noble/secp256k1';

const { bytesToHex, hexToBytes, concatBytes, mod, invert, randomBytes } = secp.etc;
const { isValidSecretKey, isValidPublicKey, randomSecretKey } = secp.utils;
const { Point } = secp;
console.log(Point.CURVE(), Point.BASE);
/*
class Point {
  static BASE: Point;
  static ZERO: Point;
  readonly X: bigint;
  readonly Y: bigint;
  readonly Z: bigint;
  constructor(X: bigint, Y: bigint, Z: bigint);
  static CURVE(): WeierstrassOpts<bigint>;
  static fromAffine(ap: AffinePoint): Point;
  static fromBytes(bytes: Bytes): Point;
  static fromHex(hex: string): Point;
  get x(): bigint;
  get y(): bigint;
  equals(other: Point): boolean;
  is0(): boolean;
  negate(): Point;
  double(): Point;
  add(other: Point): Point;
  subtract(other: Point): Point;
  multiply(n: bigint): Point;
  multiplyUnsafe(scalar: bigint): Point;
  toAffine(): AffinePoint;
  assertValidity(): Point;
  toBytes(isCompressed?: boolean): Bytes;
  toHex(isCompressed?: boolean): string;
}
*/

Security

The module is production-ready.

We cross-test against sister project noble-curves, which was audited and provides improved security.

• The current version has not been independently audited. It is a rewrite of v1, which has been audited by cure53 in Apr 2021: PDF (funded by Umbra.cash & community).
• It's being fuzzed in a separate repository

Constant-timeness

We're targetting algorithmic constant time. 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.

Supply chain security

• Commits are signed with PGP keys to prevent forgery. Be sure to verify the commit signatures
• Releases are made transparently through token-less GitHub CI and Trusted Publishing. Be sure to verify the provenance logs for authenticity.
• Rare releasing is practiced to minimize the need for re-audits by end-users.
• Dependencies are minimized and strictly pinned to reduce supply-chain risk.
  • We use as few dependencies as possible.
  • Version ranges are locked, and changes are checked with npm-diff.
• Dev dependencies are excluded from end-user installs; they’re only used for development and build steps.

For this package, there are 0 dependencies; and a few dev dependencies:

• noble-hashes provides cryptographic hashing functionality
• jsbt is used for benchmarking / testing / build tooling and developed by the same author
• prettier, fast-check and typescript are used for code quality / test generation / ts compilation

Randomness

We rely on the built-in crypto.getRandomValues, which is considered a cryptographically secure PRNG.

Browsers have had weaknesses in the past - and could again - but implementing a userspace CSPRNG is even worse, as there’s no reliable userspace source of high-quality entropy.

Quantum computers

Cryptographically relevant quantum computer, if built, will allow to break elliptic curve cryptography (both ECDSA / EdDSA & ECDH) using Shor's algorithm.

Consider switching to newer / hybrid algorithms, such as SPHINCS+. They are available in noble-post-quantum.

NIST prohibits classical cryptography (RSA, DSA, ECDSA, ECDH) after 2035. Australian ASD prohibits it after 2030.

Upgrading

v2 to v3

v3 brings the package closer to noble-curves v2.

• Add Schnorr signatures
• Most methods now expect Uint8Array, string hex inputs are prohibited
• Add keygen, keygenAsync method
• sign, verify: Switch to prehashed messages. Instead of messageHash, the methods now expect unhashed message. To bring back old behavior, use option {prehash: false}
• sign, verify: Switch to Uint8Array signatures (format: 'compact') by default.
• verify: der format must be explicitly specified in {format: 'der'}. This reduces malleability
• verify: prohibit Signature-instance signature. User must now always do signature.toBytes()
• Node v20.19 is now the minimum required version
• Various small changes for types
• etc: hashes are now set in hashes object. Also sha256 needs to be set now for prehash: true:

import { etc, hashes } from '@noble/secp256k1';
import { hmac } from '@noble/hashes/hmac.js';
import { sha256 } from '@noble/hashes/sha2.js';
// before
etc.hmacSha256Sync = (key, ...messages) => hmac(sha256, key, etc.concatBytes(...messages));
etc.hmacSha256Async = (key, ...messages) => Promise.resolve(etc.hmacSha256Sync(key, ...messages));
// after
hashes.hmacSha256 = (key, msg) => hmac(sha256, key, msg);
hashes.sha256 = sha256;
hashes.hmacSha256Async = async (key, msg) => hmac(sha256, key, msg);
hashes.sha256Async = async (msg) => sha256(msg);

v1 to v2

v2 improves security and reduces attack surface. The goal of v2 is to provide minimum possible JS library which is safe and fast.

• Disable some features to ensure 4x smaller than v1, 5KB bundle size:
  • The features are now a part of noble-curves, switch to curves if you need them. Curves is drop-in replacement.
  • DER encoding: toDERHex, toDERRawBytes, signing / verification of DER sigs
  • Schnorr signatures
  • Support for environments which don't support bigint literals
  • Common.js support
  • Support for node.js 18 and older without shim
  • Using utils.precompute() for non-base point
• 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; use signAsync for async version
  • 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, toBytes, 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
  • 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)

Speed

npm run bench

Benchmarks measured with Apple M4. noble-curves enable faster performance.

keygen x 7,267 ops/sec @ 137μs/op
sign x 6,888 ops/sec @ 145μs/op
verify x 788 ops/sec @ 1ms/op
getSharedSecret x 654 ops/sec @ 1ms/op
recoverPublicKey x 766 ops/sec @ 1ms/op

signAsync x 4,353 ops/sec @ 229μs/op
verifyAsync x 773 ops/sec @ 1ms/op

Point.fromBytes x 13,322 ops/sec @ 75μs/op

License

The MIT License (MIT)

Copyright (c) 2019 Paul Miller (https://paulmillr.com)

See LICENSE file.