On the substitution method of the AES algorithm

Abstract

This paper is focused on the weakness of the Advanced Encryption Standard (AES) provided by the substitution step of the algorithm, which replaces each input data byte with a fix value provided by a static substitution box (S-box) [1]. Efficiently attacks on software programs secured by AES, are concentrated on whitening the S-box, in order to compromise the encryption key and the private information [2]. We propose an algebraic substitution method which dynamically modifies the “S-box”, based on a key sequence and a mathematic function operating on the Galois Field with 8-bit elements. The algorithm will be more robust under cryptographic attacks and the security of the system will be considerably improved.