iOS Authentication(Username & Password) Saving and Retrieving

I want to create a login screen for a native app which will store the username and password in the iPhone itself. I need a layer of security for the app so that the username and password is stored in encrypted form.

Which is the best method to implement my need ? I'm reluctant to use .plist because of the lack of security and SQLite etc because my app don't need to store/retrieve bulk of data.

In addition to that I would like to have a settings screen to change the username and password later.

Please guide me since I'm a newbie to world of iPhone programming.

Thanks for the reply.

Mine is a very simple app which just needs to store the username and password in non-text form.

Which is the method to store it in binary format in the Apps folder itself ?