xv
PREFACE
“The tie, if I might suggest it, sir, a shade more tightly knotted. One aims at the
perfect butterfly effect. If you will permit me —”
“What does it matter, Jeeves, at a time like this? Do you realize that
Mr. Little’s domestic happiness is hanging in the scale?”
“There is no time, sir, at which ties do not matter.”
—Very Good, Jeeves! P. G.Wodehouse
In this age of universal electronic connectivity, of viruses and hackers, of electronic eaves-
dropping and electronic fraud, there is indeed no time at which security does not matter.Two
trends have come together to make the topic of this book of vital interest. First, the explosive
growth in computer systems and their interconnections via networks has increased the
dependence of both organizations and individuals on the information stored and communi-
cated using these systems. This, in turn, has led to a heightened awareness of the need to
protect data and resources from disclosure, to guarantee the authenticity of data and
messages, and to protect systems from network-based attacks. Second, the disciplines of
cryptography and network security have matured, leading to the development of practical,
readily available applications to enforce network security.
OBJECTIVES
It is the purpose of this book to provide a practical survey of both the principles and practice
of cryptography and network security. In the first part of the book, the basic issues to be
addressed by a network security capability are explored by providing a tutorial and survey of
cryptography and network security technology. The latter part of the book deals with the
practice of network security: practical applications that have been implemented and are in
use to provide network security.
The subject, and therefore this book, draws on a variety of disciplines. In particular, it is
impossible to appreciate the significance of some of the techniques discussed in this book
without a basic understanding of number theory and some results from probability theory.
Nevertheless, an attempt has been made to make the book self-contained.The book presents
not only the basic mathematical results that are needed but provides the reader with an
intuitive understanding of those results. Such background material is introduced as needed.
This approach helps to motivate the material that is introduced, and the author considers
this preferable to simply presenting all of the mathematical material in a lump at the begin-
ning of the book.
INTENDED AUDIENCE
The book is intended for both academic and a professional audiences. As a textbook, it is
intended as a one-semester undergraduate course in cryptography and network security for
computer science, computer engineering, and electrical engineering majors. It covers the