Construction of Cryptographically Strong 8x8 S-boxes

Abstract: The Advanced Encryption Standard (AES) has been lately accepted as the symmetric cryptography standard for confidential data transmission. However, the natural and malicious injected faults reduce its reliability and may cause confidential information leakage. S-box is the pivotal part of AES and many researchers are paying attention to improve the quality of S-box design. In this paper, a method for obtaining cryptographically strong 8 x 8 S-boxes is presented. To know the strength of our box we analyze it against different criterions such as Strict Avalanche Criterion (SAC), Bit Independent Criterion (BIC), differential approximation probability (DP), linear approximation probability (LP), nonlinearity and majority logic criterion are very close to some well known S -boxes from literature. Key words: S-box • SAC • LP • DP • BIC INTRODUCTION The National Institute of Standards and Technology initiated a process to select a symmetric-key encryption/decryption algorithm in 1997. Finally, Rijndael algorithm was accepted among other finalists as the Advanced Encryption Standard (AES) in 2001 [1]. The fast hardware and software implementations and the high level of security of the AES ha ve led to its widespread usage in different critical applications needing reliable systems and architectures [1, 2]. As an example, the AES has been lately utilized for the bitstream security mechanisms in the FPGAs for increasing the reliability of the FPGA-based designs [3], used in the recent Xilinx R VirtexTM FPGA families [4]. In this letter, we proposed a new S-box using a particular type of fractional linear transformation (17z+13)/(29z+41) and analyze proposed Substitution box with some well-known analyses which have discussed earlier. These analyses include nonlinearity, BIC, SAC, LP, DP etc, these criterions are necessary for a good S -box. Proposed S-box does not satisfy all criterions entirely but close to the optimal value. So we can make use of it in encryption for secure communication. This paper is structured as follows; section 2 present analysis of S-box which includes nonlinearity analysis, bit independent criterion analysis, linear approximation probability analysis,differential approximation probability analysis, analytical strict avalanche criterion analysis, graphical strict avalanche analysis and section 3 presents conclusion.