First introduced in 1995, Cryptography: Theory and Practice is the most widely used and referenced textbook for introductory cryptography courses taught throughout the world. Through three editions this textbook has been embraced by instructors and students alike. The fourth edition provides mathematical background in a "e;just-in-time"e; fashion, informal descriptions of cryptosystems along with more precise pseudocode, and a host of numerical examples and exercises. The authors offer comprehensive, in-depth treatment of the methods and protocols that are vital to safeguarding the seemingly infinite and increasing amount of information circulating around the world.