BBS Signatures (@digitalbazaar/bbs-signatures)

A JavaScript BBS Signatures Implementation

Table of Contents

• Background
• Security
• Install
• Usage
• Contribute
• Commercial Support
• License

Background

See also (related specs):

• BBS Signatures RFC

Security

As with most security- and cryptography-related tools, the overall security of your system will largely depend on your design decisions.

Install

• Node.js 18+ is required.

To install locally (for development):

git clone https://github.com/digitalbazaar/bbs-signatures.git
cd bbs-signatures
npm install

Usage

Generating a new public/secret key pair

To generate a new public/secret BLS12-381 key pair for use with BBS signatures:

import * as bbs from '@digitalbazaar/bbs-signatures';

const {secretKey, publicKey} = await bbs.generateKeyPair({
  ciphersuite: 'BLS12-381-SHA-256'
  // same as using the constant: bbs.CIPHERSUITES.BLS12381_SHA256
});
// includes `secretKey` and `publicKey` keys, each is a `Uint8Array`
// `secretKey` is big-endian-encoded scalar
// `publicKey` is compressed (x, y) coordinates of a BLS12-381 G2 point
// other ciphersuite choice is: 'BLS12-381-SHAKE-256'

Creating a BBS signature

Sign an optional header and an array of messages using BBS.

import * as bbs from '@digitalbazaar/bbs-signatures';

const {secretKey, publicKey} = await bbs.generateKeyPair({
  ciphersuite: 'BLS12-381-SHA-256'
});
// `header`
const header = new Uint8Array();
// N-many `messages`, each is a `Uint8Array`, use `TextEncoder` to
// express strings as UTF-8 bytes
const messages = [new TextEncoder().encode('some message')];
// `signature` is a `Uint8Array`
const signature = await bbs.sign({secretKey, publicKey, header, messages});

Verifying a BBS signature

Verify a full BBS signature. This verification method is less likely to be used than verifyProof() as holders of signatures are expected to derive proofs for verification by verifiers.

import * as bbs from '@digitalbazaar/bbs-signatures';

// pass original signer's `publicKey`, `signature`, `header`, and `messages`
const verified = await bbs.verifySignature({
  publicKey, signature, header, messages,
  ciphersuite: 'BLS12-381-SHA-256'
});
// `verified` is a boolean

Creating a BBS proof

Derive a proof from a BBS signature as a holder / prover.

import * as bbs from '@digitalbazaar/bbs-signatures';

// pass original signer's `publicKey`, `signature`, `header`, and `messages`
// as well as a custom `presentationHeader` and any `disclosedMessageIndexes`
const proof = await bbs.deriveProof({
  publicKey, signature, header, messages,
  presentationHeader, disclosedMessageIndexes,
  ciphersuite: 'BLS12-381-SHA-256'
});
// `proof` is a `Uint8Array` containing a BBS proof

Verifying a BBS proof

Verify a proof from a holder / prover.

import * as bbs from '@digitalbazaar/bbs-signatures';

// pass `proof`, original signer's `publicKey` and`header`
// as well as holder's custom `presentationHeader`, `disclosedMessages`, and
// `disclosedMessageIndexes`
const verified = await bbs.verifyProof({
  publicKey, proof, header,
  presentationHeader, disclosedMessages, disclosedMessageIndexes,
  ciphersuite: 'BLS12-381-SHA-256'
});
// `verified` is a boolean

Contribute

See the contribute file!

PRs accepted.

If editing the Readme, please conform to the standard-readme specification.

Commercial Support

Commercial support for this library is available upon request from Digital Bazaar: [email protected]

License

New BSD License (3-clause) © 2024 Digital Bazaar