Computer Security and Cryptography

FOREWORD

It's not easy being a writer on cryptology. Actually, it's not easy being a writer. You have to think about what subjects you want to cover. Then you have to decide in what order you want to put them—not so simple, because the most logical progression isn't always the best for teaching. Then comes the worst part: You actually have to cover a blank screen or sheet of paper with letters and figures that make sense.

Alan Konheim has sweated through it many times. He has written a number of technical articles, which demonstrates that he has mastered the technicalities of his subject. And he has passed through the fire of book authorship once before, in his acclaimed Cryptography: A Primer. In the years that followed, he has learned what worked in that book and what didn't, and has applied those lessons in the present work. The result is a fine amalgam of scholarship and pedagogy.

But if the elements of writing—clarity and concision—have remained the same, cryptology has not. For centuries, it was axiomatic that both en- and decipherer had to have the same key, though used inversely. The invention of public-key cryptography abolished that axiom. It has transformed and energized the practical applications of cryptography. Many of these remain grounded in the classical, or symmetric, systems of cryptography. And the enormous expansion of communications has driven its child, secret communications, into vast new fields. Once the exclusive domain of soldiers and diplomats and spies, ...