Extending My_Controller with an Auth layer.

[eluser]gh0st[/eluser]
I know you can use MY_Controller to extend CI's base functionality; but when it comes to an Auth layer what is the best way to do this?

Code:

class MY_Controller extends Controller
{
...
}

I am using Tank_Auth, but I guess it could work with any Auth layer -- is there a right way to add an auth layer so that I do not need to continually add the auth stuff in every controller.

Then comes the problem of how do you make the Public side not pick up the auth layer (unless they need it).

Thanks.