This plugin allows you to require a secret key that is passed via the URL: http://example.com/post-title/?key=[string]
Fixes for default permalinks.
Reworked so the key could be set using a widget in the post/page. Also added a way to generate a random key from withing the widget. Better die page that helps tell the user what is missing.
Initial creation of the plugin for use in one of our own projects. This includes the feature to specify a key in the WordPress post's custom field "key" and passing that key via the GET method in the URL, like http://example.com/?key=string