code: function Strategy(options, verify) {
    if (typeof options == 'function') {
      verify = options;
      options = {};
    }
    if (!verify) throw new Error('hash authentication strategy requires a verify function');
  
    this._hashParam = options.hashParam || 'hash';
  
    passport.Strategy.call(this);
    this.name = 'hash';
    this._verify = verify;
    this._passReqToCallback = options.passReqToCallback;
    this._headerField = options.headerField || 'X-Auth-Hash';
  }
docs: `Strategy` constructor.
  
  The hash authentication strategy authenticates requests based on the
  hash link.
  
  Applications must supply a `verify` callback which accepts `hash`, and then
  calls the `done` callback supplying a
  `user`, which should be set to `false` if the hash is not valid.
  If an exception occured, `err` should be set.
  
  Optionally, `options` can be used to change the parameter in which the
  hash is found.
  
  Options:
  - `hashParam`  parameter name where the hash is found, defaults to _hash_
  - `passReqToCallback`  when `true`, `req` is the first argument to the verify callback (default: `false`)
  
  Examples:
  
  passport.use(new HashStrategy(
  function(hash, done) {
  User.findOne({ hash: hash }, function (err, user) {
  done(err, user);
  });
  }
  ));
  
  @param {Object} options
  @param {Function} verify
  @api public