New method for improving add round key in the advanced encryption standard algorithm

ABSTRACT This paper proposes a new modification to the AES in order to ensure a high-level security. This is accomplished by replacing the binary Exclusive OR (XOR) operation in each add-round-key stage of the AES with a new (#) operation. The (#) operation requires an additional and randomly generated control key to determine the state table (among 256 optional state tables) needed to apply the (#) operation. The 256 states tables are formed based on the addition operation in the Galois Field GF (28) to increase the randomness of the algorithm. The modified AES algorithm has been evaluated based on several security metrics. In our proposed algorithm, an attacker needs, at minimum, up to (2431)10 probabilities of keys to decrypt an encrypted message; thus, the proposed AES algorithm increases the complexity of the original AES against the differential cryptanalysis. Moreover, compared to the original AES, applying the (#) operation in our modified algorithm also improves the performance in other security metrics, such as NIST and histogram. Consequently, this replacement by using two keys in both the encryption and decryption process adds a new level of “protection and a greater degree of robustness against breaking methods.