Applied Cryptography: Protocols, Algorithms, and Source Code in C

What a wonderful book! I studied some crypto in college (public key and zero knowledge proofs) and found the field almost incomprehensible: lots of very specific number theories, very little overview information. Applied Cryptography fills this vital gap very successfully, going from completely introductory information to some fairly specific details on particular systems. The 2000 or so references in the back are great when you need to follow up on particular details. It's good this book was published when it was, right at the time that the US government is trying to censor net traffic and stop people from using strong cryptosystems.