Hardware Implementation of Dynamic S-BOX to Use in AES Cryptosystem

One of the major cipher symmetric algorithms is AES. Its main feature is to use S-BOX step, which is the only nonlinear part of this standard possessing fixed structure. During the previous studies, it was shown that AES standard security was increased by changing the design concepts of S-BOX and production of dynamic S-BOX. In this paper, a change of AES standard security is studied by production of dynamic and key-dependent S-BOX. Also the LFSR random number generation hardware algorithm is applied in order to produce the dynamic S-BOX. In order to produce a dynamic and keydependent S-BOX, the field bits of key are divided into separated bits at first and then a byte is selected by LFSR algorithm randomly. The number of selected bit is considered as the repeating number of LFSR algorithm and is applied in order to produce dynamic S-BOX. In the evaluation step, we compared the proposed model with fixed S-BOX model in the original AES algorithm. It was shown that the proposed implementation could increase the security as about 0.2%, 0.017% and 0.19%, 0.04 in the case of avalanche effect, output bits dependence criteria, compared with the strict avalanche criteria and in the case of linear criteria, respectively.

کلیدواژه ها:

Advanced Encryption Standard ، Changeable ، Feedback Shift Register ، Moving Boxes ، Simultaneous Encryption