A novel approach for designing the s-box of advanced encryption standard algorithm (AES) using chaotic map

The substitution boxes (S-boxes) are found in many block cipher algorithms. The concepts of completeness and the avalanche effect were combined to define a property which was called the strict avalanche criterion. In this paper a couple chaotic system based pseudo random bit generator (CCS-PRBG) has been presented and the output sequences of the CCS-PRBG were tested using the NIST statistical tests for randomness to ensure the cryptographic properties of the generated sequences. Two CCS-PRBG were used to design a chaotic key-dependent S-box for the AES encryption algorithm. The proposed S-box satisfies the strict avalanche criterion and the avalanche variable independence requirement. Large number of sequences that represent encrypted data using the AES encryption algorithm with chaotic key-dependent S-box have been tested using the NIST statistical tests. The proposed algorithm has been used to encrypt and decrypt an image. The encrypted image has been subjected to statistical analysis to demonstrate the confusion and diffusion properties by analyzing the histogram and correlations of pixels of the plain and ciphered image. The results indicate that the encrypted sequences have passed all NIST statistical tests. Also, the diffusion and confusion properties have been demonstrated for the ciphered image