Securing Windows Server 2003

Key-Based Cryptography

Cryptography is perhaps one of the most important fundamental concepts in computer security today. Cryptography has played a role in every version of Windows to date, and it plays an even larger role in Windows Server 2003 than ever before. Many of the technologies and techniques I discuss in this book rely heavily on cryptography, including smart cards, data encryption, digital signatures, and email security. For that reason, it’s important that you understand what cryptography is and how it works.

At its heart, cryptography is about scrambling data so that only the sender and the recipient can read it. Modern cryptography serves the same purpose as the secret decoder ring you had as a kid, although it’s vastly more complex and powerful than that ring. Modern cryptography uses complicated mathematical processes called algorithms to scramble and unscramble data. And I mean complicated. In fact, some of the world’s most popular cryptography algorithms are so complex and unique that they’ve received worldwide patents.

There are three basic kinds of cryptography: keyed hashing, shared secret keys, and public keys. Each provides a slightly different technique for encrypting data, and each is used for a specific set of purposes.

Hashing

A hash is a form of encryption in which a computer uses a well-known algorithm to scramble data and return a fixed-length result that is reasonably unique to the data. Theoretically, hashes aren’t really that secure, because the ...