9 - Secure Systems

Abstract

This chapter explores the two standard block ciphers: Data Encryption Standard (DES) and Advanced Encryption Standard (AES). It shows how two standard block ciphers can be implemented in VHSIC hardware description language (VHDL), where VHSIC stands for very high speed integrated circuit.. The data encryption standard (DES) is a symmetric “block cipher.” A block cipher operates on complete blocks of data at any one time and produces a ciphertext block of equal size. DES is a block cipher that operates on data blocks of 64 bits in size. DES, in common with other block ciphers, is based around a structure called a “Feistel Lattice.” The key parameters for the implementation of a Feistel network are block size, key size, number of rounds, subkey generation, and round function. The chapter describes the coarse and fine structure of DES. The fine structure of DES consists of several important functional blocks: initial permutation, key transformations, compression permutation, and expansion permutation. The chapter also describes the process of implementing advanced encryption standard (AES) in VHDL.