Rails 2.0 WP 2.3 = Auto Users Parallel Authentication

Hello
I am interested in integrating WP 2.3.3 with a Rails 2.0.2 app that am currently working on. I would like to do the following things with it –
1. user signs up on the core site (rails app)
2. the same username (with user details) are passed onto the wordpress system to create a new user (how could i do this?)
3. the user can then log in into the rails app and use it
4. in the core site, wordpress is integrated for commenting etc which the user can transparently use as he is authenticated in parallel.

Any idea how I could go about it? Thank you.