The topic of computer security involves the history and techniques of cryptography. The field of cryptography predates written history. Mathematicians working for Caesar, in his drive to conquer the known world, discovered techniques that are still in use today. Brett Tjaden successfully blends motivating examples with contemporary techniques to address the needs of senior- level undergraduate or graduate-level computer science courses on security. The topics covered in the book are increasingly making front-page news. Viruses have shut down the worldwide networks of major global corporations. Controversy rages over the FBI's Carnivore project which identifies potential threats to national security and to uncover criminal activity. The technical and conceptual issues that are the underpinnings of these unfolding events are covered.