Introduction

Cryptography is everywhere these days, from hashed passwords to encrypted mail, to Internet Protocol Security (IPSec) virtual private networks (VPNs) and even encrypted filesystems. Security is the reason why people opt to encrypt data, and if you want your data to remain secure you'd best know a bit about how cryptography works. This chapter certainly can't teach you how to become a professional cryptographer that takes years of study and practice but you will learn how most of the cryptography you will come in contact with functions (without all the complicated math, of course).

We'll examine some of the history of cryptography and then look closely at a few of the most common algorithms, including Advanced Encryption Standard (AES), the recently announced new cryptography standard for the U.S. government. We'll learn how key exchanges and public key cryptography came into play, and how to use them. I'll show you how almost all cryptography is at least theoretically vulnerable to brute force attacks.

Naturally, once we've covered the background we'll look at how cryptography can be broken, from cracking passwords to man-in-the-middle-type attacks. We'll also look at how other attacks based on poor implementation of strong cryptography can reduce your security level to zero. Finally, we'll examine how weak attempts to hide information using outdated cryptography can easily be broken.

Understanding Cryptography Concepts

What does the word crypto mean? It has its origins in the Greek word kruptos, which means hidden. Thus, the objective of cryptography is to...