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Cryptography isn't all there is to security. But rendering information unintelligible to those without the proper key usually plays a big role in any networked data-sharing system. Java Cryptography shows the Java programmer (with or without crypto experience) how to implement ciphers, keys, and other data-obscuring techniques in Java.

The Java language includes lots of classes that are designed to facilitate cryptography, and this book explores them in depth. Key management classes, random-number generators, signed applets, and other parts of the Java security mechanism get attention in these pages. But most interesting are the author's examples. He has written a complete implementation of the ElGamal cipher as a provider in the framework of the Java Security API. If you want to understand how the Provider Architecture works, this is what you need to examine. Don't look here for an explanation of the mathematics, however.

In addition to his discussions and examples for individual pieces of the cryptography infrastructure and his implementation of the ElGamal system, Knudsen includes two nifty crypto-enabled programs: a chat system and an e-mail system.