code: function randomHexString(size) {
    if (size === 0) {
      throw new Error('Zero-length randomHexString is useless.');
    }
    if (size % 2 !== 0) {
      throw new Error('randomHexString size must be divisible by 2.');
    }
    return crypto.randomBytes(size / 2).toString('hex');
  }
docs: Returns a new random hex string of the given even size.