Appendix    C

Introduction to Cryptography

The word cryptography is derived from the Greek words kryptos, meaning “hidden,” and grafein, meaning “to write.” Throughout history, cryptography has been used to hide messages inside tradional means of communication that might otherwise be intercepted. Doing so is accomplished by concealing the contents of the message from all except who has the key to unlock it. In modern times, cryptographic techniques are used to protect e-mail messages, information transmitted over the internet, credit card information, and data on corporate networks.

A wide variety of cryptographic techniques are used with computers. They are typically provided for one of two reasons: to protect data while at rest on a computer ...

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