Modifying Advanced Encryption Standard (AES) Algorithm

Abstract

This paper presents modifications on AES algorithm to improve the security of Standard AES, the improving has been done by three modifications. The first modification use key-dependent dynamic S-box (10 S-box) instead of static S-box (1 S-box), that used by Standard AES in order to improve "confusion" properties represented by Byte Substitution layer. The second modification use key-dependent variable values for shifting "state-matrix" rows process instead of fixed values that used by Standard AES in order to improve "diffusion" properties represented by ShiftRows layer. The third modification is by using two keys instead of one key that used by Standard AES, both of them used for encryption and decryption process instead of one key that used by Standard AES in order to improve the general structure and key generation algorithm of AES. The Modified AES tested and evaluated by five scales (Basic Five Statistical Tests, NIST Tests Suite, Encryption Run Time, Brute-Force Attack and Cryptanalytic Attack) to prove the functionality of modifying.