[maemilius]

I would disagree on the grounds that authentication is, generally speaking, a well-solved problem for the level most applications require. It's a better use of your time to use a library that's well-used and well-understood rather than rolling Yet Another (Probably Bad) Authentication Framework.

I will concede, however, that the most basic forms of authentication that I've used are so close to the metal that they're usually already built into whatever you're using to do communication.