code: function chacha20(data, key, iv) {
      return Promise.resolve().then(function() {
          var algo = new ChaCha20(new Uint8Array(key), new Uint8Array(iv));
          return ByteUtils.arrayToBuffer(algo.encrypt(new Uint8Array(data)));
      });
  }
docs: Encrypts with ChaCha20
  @param {ArrayBuffer} data
  @param {ArrayBuffer} key
  @param {ArrayBuffer} iv
  @returns {Promise.<ArrayBuffer>}