Log users in against their accounts in a Ruby on Rails application.
To change encryption methods you will need to edit the plugin code. Override the function WP_Rails_Authentication#apply_encryption with your preferred encryption method.
Due to ruby and PHP using different serialisation approaches we've not (yet) got an easy way to share sessions.
Providing your blog server can access the database, you simply need an appropriate database.yml file.
= Are there other approaches to this problem?
Since this plugin was developed, the Rails Integration API plugin has been released. That requires you to add some API code to your rails app, but may be easier if you want to keep all the encryption logic solely in rails or can't add an extra module to PHP.