code: function SymEncryptedIntegrityProtected() {
    this.tag = enums.packet.symEncryptedIntegrityProtected;
    this.version = VERSION;
    /** The encrypted payload. */
    this.encrypted = null; // string
    /**
     * If after decrypting the packet this is set to true,
     * a modification has been detected and thus the contents
     * should be discarded.
     * @type {Boolean}
     */
    this.modification = false;
    this.packets = null;
  }
docs: A one-octet version number of the data packet. 
  Implementation of the Sym. Encrypted Integrity Protected Data Packet (Tag 18)
  
  {@link https://tools.ietf.org/html/rfc4880#section-5.13|RFC4880 5.13}:
  The Symmetrically Encrypted Integrity Protected Data packet is
  a variant of the Symmetrically Encrypted Data packet. It is a new feature
  created for OpenPGP that addresses the problem of detecting a modification to
  encrypted data. It is used in combination with a Modification Detection Code
  packet.
  @memberof module:packet
  @constructor