This chapter covers cryptography, a topic and body of knowl-
edge that you will encounter over and over again during your
career as a pen tester, IT person, or security manager. Having
a firm grip of the technology and science is indispensable because cryptography is critical in
so many areas. This chapter covers the following aspects of cryptography:
■ Applications of cryptography
■ Symmetric and asymmetric cryptography
■ Working with hashing
■ Purposes of keys
■ Types of algorithms
■ Key management issues
Cryptography is the body of knowledge that relates to the protection of information in
all its forms. Through the application of cryptography, you can safeguard the confidentiality
and integrity of information. Cryptography provides you with a means of keeping informa-
tion away from prying eyes and gives you a way to keep the same information intact. This
chapter focuses on cryptography and its application in the modern world, but first it delves
into some of the rich history of the science to give you a firm foundation on which you can
build your knowledge.
The science of cryptography provides a unique set of abilities that have been around as
long as humans have wanted to share information with some but not with others. Although
technology, science, and computers have improved on the older methods, what has
remained a constant is the underlying goal of protecting information.
You may have opened this book with little or no knowledge of the technology, or maybe
you have a basic understanding. In either case, this chapter will get you where you need to be
for the CEH exam and will move cryptography out of the realm of secret agents, spies, and
puzzles and into the realm of practical applications and usage. You’ll learn about something
that is woven into the fabric of your everyday life—from the phone in your pocket, to the
computer on your lap, and even to that card you stick in the ATM or use to charge dinner.
Cryptography: Early Applications and Examples
So what is cryptography? Why should you even care? Well, let’s see if I can answer these
questions by looking at the body of knowledge and exploring its depths. Cryptography
deals with protection and preservation of information in all its forms. This science has