Although Codeigniter 2.1 was released few days ago, it still does not has a native authentication library (or maybe never). Are you searching for an authentication library for Codeigniter? Here, I would like to suggest several libraries which can make your life easier. Why do you want to create a new library or code the authentication system by yourself if there is a superb one? On top of that, it is free!
Below are 5 best authentication libraries for CodeIgniter (from my observation). You can give them a try! Most of them are compatible with CodeIgniter 2.1 (I guess, hehehe 
). However, please keep in mind that each library maybe offers different features. Hence, the security features can be varies.
