Strengthening AES Security through Key-Dependent ShiftRow and AddRoundKey Transformations Utilizing Permutation

Abstract

AES (Advanced Encryption Standard) is a widely applied block cipher standard in the United States, used in various security applications today. Currently, there are numerous research endeavors aimed at making AES block ciphers dynamic to improve their security against contemporary strong attacks. The most common dynamic approach involves the dynamization of AES block transformations, including SubByte, ShiftRow, AddRoundKey, and MixColumn operations. The combination of these transformations has also been explored and proposed. However, to the best of our knowledge, the dynamic combination of AddRoundKey and ShiftRow transformations remains unexplored. Therefore, in this paper we introduce algorithms for generating key-dependent AddRoundKey and ShiftRow transformations based on permutations. Subsequently, these key-dependent transformations are applied to AES to create dynamic AES block ciphers. Security analysis and evaluation of NIST's statistical criteria are performed, and the entropy of AES and dynamic AES is assessed. From our findings, it is evident that dynamic AES block ciphers can significantly enhance AES security and meet stringent randomness criteria, similar to AES.