Verifiable Delay Function (VDF) implementation compiled from Rust to WebAssembly

This repository is a port of VDFs by POA Network to WebAssemnbly, so that it runs in any modern browser or Node.js environment.

TypeScript support is also present.

NOTE: Performance is very bad right now, more than an order of magnitude slower than native code.

How to install

npm install @subspace/vdf

How to use

Node.js:

import createVdf from '@subspace/vdf';

createVdf()
    .then((vdfInstance) => {
        const iterations = 3;
        const challenge = Buffer.from('aa', 'hex');
        const intSizeBits = 2048;
        const isPietrzak = false;
        const res = vdfInstance.generate(iterations, challenge, intSizeBits, isPietrzak);
        console.log(Buffer.from(res).toString('hex'));
        console.log(vdfInstance.verify(3, challenge, res, intSizeBits, isPietrzak));
    });

Browser:

requirejs(['@subspace/vdf'], function (createVdf) {
    createVdf()
        .then((vdfInstance) => {
            const iterations = 3;
            const challenge = Uint8Array.of(170);
            const intSizeBits = 2048;
            const isPietrzak = false;
            const res = vdfInstance.generate(iterations, challenge, intSizeBits, isPietrzak);
            console.log(
                res.reduce(
                    (str, byte) => {
                        return str + byte.toString(16).padStart(2, '0');
                    },
                    ''
                )
            );
            console.log(vdfInstance.verify(3, challenge, res, intSizeBits, isPietrzak));
        });
});

API

createVdf(options): Promise

Creates a new instance of Noise library

• options - Options object that will be passed to underlying Emscripten module (optional)

ILibrary.generate(iterations: number, challenge: Uint8Array, intSizeBits: number, isPietrzak: boolean) => Uint8Array

Generates VDF proof for a given challenge and number of iterations

• iterations - number of VDF iterations
• challenge - VDF challenge
• intSizeBits - the length of the prime numbers generated
• isPietrzak - if Pietrzak VDF is used when true and Wesolowski VDF is used when false

Returns binary proof, may throw Error exception when failed to generate proof.

ILibrary.verify(iterations: number, challenge: Uint8Array, proof: Uint8Array, intSizeBits: number, isPietrzak: boolean) => boolean

Generates VDF proof for a given challenge and number of iterations

• iterations - number of VDF iterations
• challenge - VDF challenge
• proof - previously generated proof that needs to be verified
• intSizeBits - the length of the prime numbers generated
• isPietrzak - if Pietrzak VDF is used when true and Wesolowski VDF is used when false

Returns true if proof is correct, may throw Error exception on incorrect input.

Building source code

Even though this repo contains vdf.js and vdf.wasm, you may still want to build it from source yourself for testing purposes or for publishing updates to NPM.

Instructions below work on Linux (and maybe on macOS, but not tested).

Dependencies

You'll need at least following:

• curl
• git
• gcc
• emmc, emconfigure (use https://emscripten.org/docs/getting_started/downloads.html)
• rustup (use https://rustup.rs/)

Prepare

First, make sure you have Rust, Cargo and wasm32-unknown-emscripten target installed:

rustup target add wasm32-unknown-emscripten

Build Rust to WebAssembly

This will compile GMP dependency and Rust code to vdf.js and vdf.wasm files under src.

./build.sh

Build artifacts for NPM

Before publishing to NPM it is necessary to build TypeScript to JavaScript and create minified version of the JavaScript output:

npm run build

Tests

To run tests use:

npm test

NOTE: We can't run tests against upstream repo's vectors yet because of performance issues, so instead we have a very basic test case to make sure it behaves as expected.

Contribution

Feel free to create issues and send pull requests (for big changes create an issue first and link it from the PR), they are highly appreciated!

License

MIT, see license.txt