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
• 🪶 4.86KB (gzipped, elliptic.js is 10x larger, tiny-secp256k1 is 25x larger)

The module is a sister project of noble-curves, focusing on smaller attack surface & better auditability. Curves are drop-in replacement and have more features: MSM, DER encoding, endomorphism, prehashing, custom point precomputes, hash-to-curve, oprf. To upgrade from earlier version, see Upgrading.

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 with provenance
• Check out homepage & all libraries: ciphers, curves, hashes, post-quantum, 5kb secp256k1 / ed25519

Usage

npm install @noble/secp256k1

deno add jsr:@noble/secp256k1

deno doc jsr:@noble/secp256k1 # command-line documentation

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);

  const bobsKeys = secp.keygen();
  const shared = secp.getSharedSecret(secretKey, bobsKeys.publicKey); // Diffie-Hellman
  const sigr = await secp.signAsync(msg, secretKey, { format: 'recovered' });
  const publicKey2 = secp.recoverPublicKey(sigr, msg);
})();

Enabling synchronous methods

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

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

import 'react-native-get-random-values';
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';
const { secretKey } = secp.keygen();
const msg = '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' });
// custom hash
import { keccak256 } from '@noble/hashes/sha3.js';
const sigH = secp.sign(keccak256(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';
const { secretKey, publicKey } = secp.keygen();
const msg = 'hello noble';
const sig = secp.sign(msg, secretKey);
const isValid = secp.verify(sig, msg, publicKey);

// custom hash
import { keccak256 } from '@noble/hashes/sha3.js';
const sigH = secp.sign(keccak256(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';

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

// custom hash
import { keccak256 } from '@noble/hashes/sha3.js';
const sigR = secp.sign(keccak256(msg), secretKey, { format: 'recovered', prehash: false });
const publicKey2 = secp.recoverPublicKey(sigR, keccak256(msg), { prehash: false });

Recover public key from Signature instance with recovery bit set.

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. Make sure to verify commit signatures
• Releases are transparent and built on GitHub CI. Check out attested checksums of single-file builds and provenance logs
• Rare releasing is followed to ensure less re-audit need for end-users
• Dependencies are minimized and locked-down: any dependency could get hacked and users will be downloading malware with every install.
  • We make sure to use as few dependencies as possible
  • Automatic dep updates are prevented by locking-down version ranges; diffs are checked with npm-diff
• Dev Dependencies are disabled for end-users; they are only used to develop / build the source code

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

• noble-hashes provides cryptographic hashing functionality
• micro-bmark, micro-should and jsbt are 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. It's hard to audit their source code thoroughly and fully because of their size

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.

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.

Speed

npm run bench

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

keygen x 7,643 ops/sec @ 130μs/op
sign x 7,620 ops/sec @ 131μs/op
verify x 823 ops/sec @ 1ms/op
getSharedSecret x 707 ops/sec @ 1ms/op
recoverPublicKey x 790 ops/sec @ 1ms/op

signAsync x 4,874 ops/sec @ 205μs/op
verifyAsync x 811 ops/sec @ 1ms/op

Point.fromBytes x 13,656 ops/sec @ 73μs/op

Upgrading

v1 to v2

noble-secp256k1 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)

Contributing & testing

• npm install && npm run build && npm test will build the code and run tests.
• npm run bench will run benchmarks, which may need their deps first (npm run bench:install)
• npm run build:release will build single non-module file

Check out github.com/paulmillr/guidelines for general coding practices and rules.

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

License

MIT (c) Paul Miller (https://paulmillr.com), see LICENSE file.