code: function(config) {
        config = config || {};
        config.mode = config.mode || mode1;
        this.setSecret(config.secret);
        this.setToken(config.token);
        Header.call(this, config);
      }
docs: The constructor
  
  @param {Object} config The config options
  @param {Boolean} [config.reply = false] True if the header if of a server reply
  @param {String} [config.mode = 'auth'] The mode of the header.
  
  Values:
  - 'auth': encrypt body if present
  - 'auth-plain': the body (if present) is in plaintext
  @param {String} config.sid The session identifier
  @param {Date} config.date The date
  @param {String} config.key The private RSA key
  @param {String} config.cert The public X.509 cert
  @param {String} config.encoderCert The public X.509 cert of the encoder and signer of the header
  @param {String} config.secret The secret AES shared key in Base64 format
  @param {String} config.token The authentication token
  @constructor