code: function(config) {
        config = config || {};
        this._reply = config.reply || false;
        this.setMode(config.mode || 'auth');
        this.setSid(config.sid);
        this.setDate(config.date || new Date());
        this.keychain = new Crypter({
          key : config.key,
          cert: config.cert
        });
        this.encoder = new Crypter({
          cert: config.encoderCert
        });
      }
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. See {@link node_modules.authorify_client.mixin.WithPayload#MODES allowed modes}.
  @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
  @constructor