You can probably turn up a lot of information on this topic if you use Super Search. You can take a look here to get a nice tutorial of how to use encryption. That link came from this node and there are lots of others around here such as How do I decode encrypted password files? and A very simple userid/password check. Hopefully, some of these will have what you're looking for.

If you still can't find what you're looking for or are having trouble with a specific portion of the encryption, post what you're having trouble with and maybe I can be of more help. Hopefully, this will at least get you started.

Good luck,
- Sherlock

Skepticism is the source of knowledge as much as knowledge is the source of skepticism.