Key-Dependent S-Box Generation in AES Block Cipher System

Article type: Research Article

Authors: Kazlauskas, Kazys | Kazlauskas, Jaunius

Affiliations: Institute of Mathematics and Informatics, Akademijos 4, 08663 Vilnius, Lithuania, e-mail: kazlausk@ktl.mii.lt

Abstract: Advanced Encryption Standard (AES) block cipher system is widely used in cryptographic applications. A nonlinear substitution operation is the main factor of the AES cipher system strength. The purpose of the proposed approach is to generate the random S-boxes changing for every change of the secret key. The fact that the S-boxes are randomly key-dependent and unknown is the main strength of the new approach, since both linear and differential cryptanalysis require known S-boxes. In the paper, we briefly analyze the AES algorithm, substitution S-boxes, linear and differential cryptanalysis, and describe a randomly key-dependent S-box and inverse S-box generation algorithm. After that, we introduce the independency measure of the S-box elements, and experimentally investigate the quality of the generated S-boxes.

Keywords: advanced encryption standard, key-dependent S-boxes, generation algorithm

Journal: Informatica, vol. 20, no. 1, pp. 23-34, 2009