don’t let the down votes get ya down.
check out Ion Auth
https://github.com/benedmunds/CodeIgniter-Ion-Auth
take a look at the read me, you will have to rename two files for codeigniter 3. otherwise you can see that there are recent changes to the lib. the author Ben Edmunds is one of the four developers on the new codeigniter council. http://www.codeigniter.com/help/about