scure-bip32

Audited & minimal implementation of BIP32 hierarchical deterministic (HD) wallets over secp256k1.

- 🔒 Audited by an independent security firm
- 🔻 Tree-shakeable: unused code is excluded from your builds
- 📦 ESM
- ➰ Only 3 audited dependencies by the same author:
noble-curves,
noble-hashes,
and scure-base
- 🪶 18KB gzipped with all dependencies bundled

Check out scure-bip39 if you need mnemonic phrases.
See key-producer if you need SLIP-0010/BIP32 ed25519 hdkey implementation.
Notice Warnings about BIP32.

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> scure — audited micro-libraries.

- Zero or minimal dependencies
- Highly readable TypeScript / JS code
- PGP-signed releases and transparent NPM builds
- Check out homepage & all libraries:
base,
bip32,
bip39,
btc-signer,
sr25519,
starknet

Usage

> npm install @scure/bip32

> deno add jsr:@scure/bip32

This module exports a single class HDKey, which should be used like this:

``ts
import { HDKey } from '@scure/bip32';
const hdkey1 = HDKey.fromMasterSeed(seed);
const hdkey2 = HDKey.fromExtendedKey(base58key);
const hdkey3 = HDKey.fromJSON({ xpriv: string });

// props
[hdkey1.depth, hdkey1.index, hdkey1.chainCode];
console.log(hdkey2.privateKey, hdkey2.publicKey);
console.log(hdkey3.derive("m/0/2147483647'/1"));
const sig = hdkey3.sign(hash);
hdkey3.verify(hash, sig);
`

Note: chainCode property is essentially a private part
of a secret "master" key, it should be guarded from unauthorized access.

The full API is:

`ts
class HDKey {
public static HARDENED_OFFSET: number;
public static fromMasterSeed(seed: Uint8Array, versions: Versions): HDKey;
public static fromExtendedKey(base58key: string, versions: Versions): HDKey;
public static fromJSON(json: { xpriv: string }): HDKey;

readonly versions: Versions;
readonly depth: number = 0;
readonly index: number = 0;
readonly chainCode: Uint8Array | null = null;
readonly parentFingerprint: number = 0;

get fingerprint(): number;
get identifier(): Uint8Array | undefined;
get pubKeyHash(): Uint8Array | undefined;
get privateKey(): Uint8Array | null;
get publicKey(): Uint8Array | null;
get privateExtendedKey(): string;
get publicExtendedKey(): string;

derive(path: string): HDKey;
deriveChild(index: number): HDKey;
sign(hash: Uint8Array): Uint8Array;
verify(hash: Uint8Array, signature: Uint8Array): boolean;
wipePrivateData(): this;
}

interface Versions {
private: number;
public: number;
}
`

The module implements bip32 standard:
check it out for additional documentation.

The implementation is loosely based on cryptocoinjs/hdkey, which has MIT License.

Warnings about BIP32

BIP32 is a bad standard. It would be great if we've had something better.

- Network IDs (different currencies) are taken from a single GitHub document
called SLIP-0044
- There were new projects, which did not yet have SLIP. Exchanges added support of
those projects to their cold wallets. Then after the projects were added to SLIP,
the exchanges were required to re-generate their cold wallets - a complicated task
- BIP32 is unusable for many different elliptic curves. For example, ETH2 uses bls12-381
curve, and with bip32 54% of generated keys would be invalid. So, they’re using much better
BLS-only EIP-2333 as a replacement.
- It’s easy to shoot yourself in foot with non-hardened keys, which
could allow simple de-anonimization of all addresses

Security

The library has been independently audited:

- at version 1.0.1, in Jan 2022, by cure53
- PDFs: online, offline
- Changes since audit.
- The audit has been funded by Ethereum Foundation with help of Nomic Labs

The library was initially developed for js-ethereum-cryptography.
At commit ae00e6d7,
it was extracted to a separate package called micro-bip32.
After the audit we've decided to use @scure NPM namespace for security.

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- 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
- Use GitHub CLI to verify single-file builds:
gh attestation verify --owner paulmillr scure-bip32.js
- 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 3 dependencies; and a few dev dependencies:

- noble-hashes provides cryptographic hashing functionality
- noble-curves provides ECDSA
- scure-base provides base58
- 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

Contributing & testing

- npm install && npm run build && npm test will build the code and run tests.
- npm run lint / npm run format will run linter / fix linter issues.
- npm run build:release` will build single file

License

MIT License

Copyright (c) 2022 Patricio Palladino, Paul Miller (paulmillr.com)