JSON Web Tokens Node.js generate and verify

jwt.js

const {TokenVerifier} = require('jsontokens');
const {randomBytes, createHash} = require('crypto');
const secp256k1 = require('secp256k1');

function signer(privateKey, data) {
  const hash = createHash(`sha256`).update(data).digest();
  const signature = secp256k1.sign(hash, privateKey).signature.toString('base64');
  return signature;
}

function base64(data) {
  return new Buffer(data, 'utf8').toString('base64');
}

const privateKey = randomBytes(32);

const header = {
  "alg": "HS256",
  "typ": "JWT"
};

const b64Header = base64(JSON.stringify(header));

const body = {
  "sub": "1234567890",
  "name": "John Doe",
  "admin": true
};

const b64Body = base64(JSON.stringify(body));

const data = new Buffer(`${b64Header}.${b64Body}`);

const signature = signer(privateKey, data);

const token = `${data}.${signature}`;

const publicKey = secp256k1.publicKeyCreate(privateKey).toString('hex');

const verified = new TokenVerifier('ES256k', publicKey).verify(token);

console.log(verified);