Enhancing the Performance of the Advanced Encryption Standard (AES) Algorithm Using Multiple Substitution Boxes

Abstract

This paper proposes for a modified version of the AES algorithm using multiple substitution boxes (S-Boxes).  While many studies have been conducted specifically on modifying the S-Box, these studies were made to replace the Rijndael S-boxes in the AES cipher.  We propose to implement two substitution boxes, where the first S-Box is the Rijndael S-box and will be used as is.  The second S-Box was constructed through an XOR operation and affine transformation and will replace the MixColumns operation within the internal rounds in the cipher.  Based on simulation testing conducted, it was found out that there is a significant difference in the speed performance between the two versions favouring the proposed AES algorithm using multiple S-Box.  The findings also revealed that in both encryption and decryption processes, the AES-2SBox performed more efficiently at 27.638% and 108.369% respectively as compared to the original AES algorithm.  However, when tested using the avalanche effect, the changes in the output bits were below the minimum expected rate.