lbarman/drand-web

A web interface for drand, the distributed randomness beacon

Drand-web

A TS/JS wrapper and a web interface for the drand project.

DrandJS

The main component is a Typescript library that provides the following methods:

class Drand {
    constructor(private serverUrl: string): void

    // Fetches and return the public key of the server provided in the constructor
    public async fetchAndVerifyRandomness(): Promise<IVerifiedRandomness>

    //Fetches and return the randomness from the server provided in the constructor
    public async fetchRandomness(): Promise<IRandomnessMessage>

    // Fetches the public key of the server provided in the constructor, and stores it
    public async fetchPublicKey(): Promise<IPublicKey>

    // Verifies a randomness message with a public key
    public verifyRandomness(msg: IRandomnessMessage, publicKey: IPublicKey): boolean

    //Returns the server URL provided in the constructor
    public getServerUrl(): string

    // (potentially fetches) and returs the public key of the server provided in the constructor
    public async getServerPublicKey(): Promise<IPublicKey>
}

Typically, the library is used like this:

const d = new Drand('https://WEBSITE'); // will try to get https://WEBSITE/public for the randomness
d.fetchAndVerifyRandomness().then((data) => console.log(data));

// data is a IVerifiedRandomness struct as follows
interface IVerifiedRandomness {
    randomness: IRandomnessMessage;
    publicKey: IPublicKey;
    valid: boolean;
}

// ... and could be
{
  publicKey: {
    gid: 22,
    point: "017f225..."
  },
  randomness: {
    round: 2,
    previous: "2dbb77ae...",
    randomness: {
      gid: 21,
      point: "6a3557e04..."
    }
  },
  valid: true
}

Internally, drand.ts calls a JS lib created from Go with GopherJS, and manually typed (drandjs/drand-go-to-js/api.d.ts). Ideally, at some point this should be replaced with a pure typescript code for verifying the signature.

Web

This is a minimal web UI that uses DrandJS to contact a server and periodically show the output.

How to run

Simply open web/index.html, as a recent drand.js is already built in web.

How to build

Prerequisites: gopherjs, yarn

The top-level Makefile exposes all and test, they do all the things.

Internally, all runs the commands test and build in the drandjs folder. The details follow. In the drandjs, this:

1. installs the npm packages
2. calls gopherjs to create drand-go-to-js/api.js
3. tests the go and the TS code with go test and jest
4. compiles and packs the main typescript file src/drand.ts
5. outputs a JS binary in dist/drand.js
6. in the root folder, copies drandjs/dist/drand.js into web