Please click here if you would like to purchase Applied Cryptography or any of Schneier's other books. To get notifications when new reviews are posted, please enter your e-mail below. More than any other field in computer science, cryptography is associated with computer warfare. Recent international treaties define cryptographic algorithms as weapons, and the laws of many countries prohibit either the development, the usage, or the export of cryptographic algorithms. The whole point of cryptography is to solve problems.
Cryptography solves problems that involve secrecy, authentication, integrity, and dishonest people.
You can learn all about cryptographic algorithms and techniques, but these are academic unless they can solve a problem. Bruce Schneier's Applied Cryptography , in its second edition, is probably the best introduction to the field. But unlike many works by other researchers, Schneier's work does not read like a dry paper for a scientific journal. Breaking a plate is a good example of a one-way function. It is easy to smash a plate into a thousand tiny pieces.