DES

Abstract

In Chapter 3, we defined cryptosystems and described some historical examples. All of the cryptosystems in Chapter 3 could be broken because they are affine linear. A cryptosystem with perfect secrecy, the Vernam one-time pad, was presented in Chapter 4, but it turned out to be very inefficient. In this chapter, we describe the Data Encryption Standard (DES). For many years, this cryptosystem was the encryption standard in the U.S. and was used worldwide. Today, DES is no longer secure. In October 2000 the US Secretary of Commerce announced the nation’s proposed new Advanced Enryption Standard. He named the Rijndael data encryption formula as the winner of a three-year competition (see [28]). Nevertheless, there are secure variants of DES (see Section 3.7), and most of the suggested successors to DES are similar to DES. Therefore, DES is still an important cryptosystem and we describe it here.