The nearly definitive beginning book for cryptological topics is Bruce Schneier's Applied Cryptography (Wiley). I could not have written this tutorial without my copy of Schneier on my lap to make sure I got everything just right.

Online, a good place to start in cryptology is the Cryptography FAQ.

To keep up on current issues and discussions, I recommend subscribing to the Usenet group sci.crypt.

A nice Web page with both good explanations and links to a variety of cryptological topics is provided by John Savard.

For topics related to compression, the author is particularly fond of his own A Data Compression Primer. For background on the several topics in this tutorial that touch on compression, this is a good starting point.