Appendix 1: Data Encryption Standard (DES)
Christina Boura · 2023
The goal of this chapter is to provide the specifications of some of the most well-known symmetric primitives.The four algorithms presented here, three block ciphers (DES, AES, PRESENT) and one hash function (KECCAK/SHA-3), are mentioned in different chapters of this book and their specifications are thus given here for completeness.We start by describing the block cipher DES.This algorithm is now deprecated and should not be used any more, but its design influenced many succeeding ciphers and inspired what should soon become some of the most important attacks against block ciphers.The other three algorithms to be described next are all actual standards.DES was first published in 1975.This algorithm, developed internally at IBM during the period 1973-1974, was based on an initial design by Horst Feistel that was called Lucifer.After modifications made to this first version (notably by the NSA), DES became a federal standard in August 1976 and was published as FIPS PUB 46 in January 1977 (National Institute of Standards and Technology 1977).DES encrypts and decrypts blocks of 64 bits by using a 56-bit key.The cipher follows a classical Feistel structure (see Chapter 3) and iterates a round function 16 times.The bits are labeled from 1 (leftmost bit) to 64 (rightmost bit).Even if today we tend to label bits starting from 0, we will follow here, for historical reasons, the original specification of DES, as given in the original FIPS documentation (National Institute of Standards and Technology 1977).