Content area

Full text

Headnote

Abstract

Block ciphers are very important in communication systems as they provide confidentiality through encryption. The popular block ciphers are Advanced Encryption Standard (AES) and MARS algorithms. Each cipher uses several rounds of fixed operations to achieve desired security level. The security level is measured in terms of diffusion and confusion. The diffusion level should be at least equal to strict avalanche criterion (SAC) value. Therefore, the number of rounds are chosen such that the algorithm provides the SAC value. This paper presents measured diffusion value of AES and MARS algorithms. Diffusion values are compared for both the algorithms: AES and MARS. Similarly, speed of each algorithm is compared.

Keywords: AES, MARS, SAC, block ciphers.

1. Introduction

The principal goal in the design of any encryption algorithm must be security. It is required to achieve the desired security level at minimal cost or expenditure. In block ciphers, the cost can be reduced if the algorithm uses less number of rounds. Therefore, it is required to do a trade-off between the security level and cost of the algorithm. This paper addresses these issues and makes comparative study of AES and MARS for diffusion analysis.

In the remaining section, it discusses symmetric algorithms, stream and block ciphers, cryptanalysis, key schedule and SAC. In section 2, it discusses AES and MARS algorithms. Diffusion analysis results are presented in section 3. Speed of each algorithm is also presented.

1.1 Symmetric Algorithms

There are two general types of key based algorithms: Symmetric and Public Key. In Symmetric algorithms encryption key can be same as the decryption key and vice versa. These are also called as secret key algorithms. Symmetric algorithms can be divided into two categories: i) some operate on the plaintext a single bit at a time which are called Stream ciphers, and ii) others operate on the plaintext in groups of bits, such groups of bits are called blocks and such algorithms are called Block ciphers.

1.2 Stream Ciphers and Block Ciphers

Stream ciphers are generally faster than block ciphers in hardware, and have less complex hardware circuitry. Stream ciphers are more suitable for situations where transmission errors are highly probable.

Symmetric key block ciphers are the most prominent and important elements in many cryptographic systems. Individually,...

Show less