code: function AEAD() {
    if (!(this instanceof AEAD))
      return new AEAD();
  
    this.chacha20 = new ChaCha20();
    this.poly1305 = new Poly1305();
    this.aadLen = 0;
    this.cipherLen = 0;
    this.polyKey = null;
  }
docs: AEAD (used for bip151)
  @alias module:crypto.AEAD
  @constructor
  @see https://github.com/openssh/openssh-portable
  @see https://tools.ietf.org/html/rfc7539#section-2.8