Chapter 9. Basic Cryptography


YORK: Then, York, be still awhile, till time do serve:Watch thou and wake when others be asleep,To pry into the secrets of the state;

 --The Second Part of King Henry the Sixth, I, i, 249–260.

Cryptography is a deep mathematical subject. Because this book focuses on system security, we view cryptography as a supporting tool. Viewed in this context, the reader needs only a brief overview of the major points of cryptography relevant to that use. This chapter provides such an overview.

Cryptographic protocols provide a cornerstone for secure communication. These protocols are built on ideas presented in this chapter and are discussed at length later on.

What Is Cryptography?

The word cryptography comes from two Greek words ...

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