npm package: @mattrglobal/node-bbs-signatures
Description: An implementation of BBS+ signatures using rust and typescript for node.js
Latest version: 0.20.0

[![MATTR](./docs/assets/mattr-logo-square.svg)](https://github.com/mattrglobal)

# Node BBS Signatures

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This repository is the home to a performant multi-message digital signature algorithm implementation which supports
deriving zero knowledge proofs that enable selective disclosure from the originally signed message set.

[BBS+ Signatures](https://github.com/mattrglobal/bbs-signatures) are a digital signature algorithm originally born from
the work on [Short group signatures](https://crypto.stanford.edu/~xb/crypto04a/groupsigs.pdf) by Boneh, Boyen, and
Shachum which was later improved on in
[Constant-Size Dynamic k-TAA](http://web.cs.iastate.edu/~wzhang/teach-552/ReadingList/552-14.pdf) as BBS+ and touched on
again in section 4.3 in
[Anonymous Attestation Using the Strong Diffie Hellman Assumption Revisited ](https://www.researchgate.net/publication/306347781_Anonymous_Attestation_Using_the_Strong_Diffie_Hellman_Assumption_Revisited).

[BBS+ Signatures](https://github.com/mattrglobal/bbs-signatures) require a
[pairing-friendly curve](https://tools.ietf.org/html/draft-irtf-cfrg-pairing-friendly-curves-03), this library includes
support for [BLS12-381](https://tools.ietf.org/html/draft-irtf-cfrg-pairing-friendly-curves-03#section-2.4).

[BBS+ Signatures](https://github.com/mattrglobal/bbs-signatures) allow for multi-message signing whilst producing a
single output signature. With a BBS signature, a [proof of knowledge](https://en.wikipedia.org/wiki/Proof_of_knowledge)
based proof can be produced where only some of the originally signed messages are revealed at the discretion of the
prover.

## Getting started

To use this package within your project simply run

```
npm install @mattrglobal/node-bbs-signatures
```

Or with [Yarn](https://yarnpkg.com/)

```
yarn add @mattrglobal/node-bbs-signatures
```

## Usage

See the [sample](./sample) directory for a runnable demo.

The following is a short sample on how to use the API

```typescript
import {
  generateBls12381G2KeyPair,
  blsSign,
  blsVerify,
  blsCreateProof,
  blsVerifyProof,
} from "@mattrglobal/node-bbs-signatures";

//Generate a new key pair
const keyPair = await generateBls12381G2KeyPair();

//Set of messages we wish to sign
const messages = [Uint8Array.from(Buffer.from("message1", "utf-8")), Uint8Array.from(Buffer.from("message2", "utf-8"))];

//Create the signature
const signature = await blsSign({
  keyPair,
  messages: messages,
});

//Verify the signature
const isVerified = await blsVerify({
  publicKey: keyPair.publicKey,
  messages: messages,
  signature,
});

//Derive a proof from the signature revealing the first message
const proof = await blsCreateProof({
  signature,
  publicKey: keyPair.publicKey,
  messages,
  nonce: Uint8Array.from(Buffer.from("nonce", "utf8")),
  revealed: [0],
});

//Verify the created proof
const isProofVerified = await blsVerifyProof({
  proof,
  publicKey: keyPair.publicKey,
  messages: messages.slice(0, 1),
  nonce: Uint8Array.from(Buffer.from("nonce", "utf8")),
});
```

## Element Size

Within a digital signature there are several elements for which it is useful to know the size, the following table
outlines the general equation for calculating element sizes in relation to BBS+ signatures as it is dependent on the
pairing friendly curve used.

| Element     | Size Equation                        |
| ----------- | ------------------------------------ |
| Private Key | F                                    |
| Public Key  | G2                                   |
| Signature   | G1 + 2\*F                            |
| Proof       | 5*G1 + (4 + no_of_hidden_messages)*F |

- `F` A field element
- `G1` A point in the field of G1
- `G2` A point in the field of G2
- `no_of_hidden_messages` The number of the hidden messages

This library includes specific support for BLS12-381 keys with BBS+ signatures and hence gives rise to the following
concrete sizes

| Element     | Size with BLS12-381                     |
| ----------- | --------------------------------------- |
| Private Key | 32 Bytes                                |
| Public Key  | 96 Bytes                                |
| Signature   | 112 Bytes                               |
| Proof       | 368 + (no_of_hidden_messages)\*32 Bytes |

## Getting started as a contributor

The following describes how to get started as a contributor to this project

### Prerequisites

The following is a list of dependencies you must install to build and contribute to this project

- [Yarn](https://yarnpkg.com/)
- [Rust](https://www.rust-lang.org/)

For more details see our [contribution guidelines](./docs/CONTRIBUTING.md)

#### Install

To install the package dependencies run:

```
yarn install --frozen-lockfile
```

#### Build

To build the project run:

```
yarn build
```

#### Test

To run the test in the project run:

```
yarn test
```

#### Benchmark

To benchmark the implementation locally run:

```
yarn benchmark
```

## Dependencies

This library uses the [bbs](https://crates.io/crates/bbs) rust crate for the implementation of BBS+ signatures and
BLS12-381 which is then wrapped and exposed in javascript/typescript using
[neon-bindings](https://github.com/neon-bindings/neon).

## Security Policy

Please see our [security policy](./SECURITY.md) for additional details about responsible disclosure of security related
issues.

---

<p align="center"><a href="https://mattr.global" target="_blank"><img height="40px" src ="./docs/assets/mattr-logo-tm.svg"></a></p><p align="center">Copyright © MATTR Limited. <a href="./LICENSE">Some rights reserved.</a><br/>“MATTR” is a trademark of MATTR Limited, registered in New Zealand and other countries.</p>