advice on private blog?

What I’d like to do is keep my current blog, but post private posts to a parcticular category (private). I’d like to password protect or otherwise secure all posts in this category so that even post titles don’t appear unless your logged in or belong to a particular user group. I don’t want unregistered users seeing posts or post titles, and I don’t want posts in that category to be viewable via RSS. Any suggestions on how to accomplish this?