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.