Construction of dynamic S-boxes with improved strict avalanche criteria

The advanced encryption standard (AES) is a prevalent encryption method used to secure digital information from unauthorized access. The Substitution Box (S-box) implemented in AES is specifically engineered to withstand various known cryptanalytic techniques. However, we studied about the various attacks and concluded that there is a need for Dynamic S-box. The S-box in AES is structured to introduce non-linearity and ensure a strong avalanche effect, meaning that altering an individual bit in the secure key or plaintext should result in nearly half of the bits in the generated ciphertext being altered. We have implemented and generated the Dynamic S-box using a string key. By making the S-box Dynamic, we intend to find the S-boxes with best possible avalanche criteria. This paper deals with designing the S-boxes which can give very high avalanche effect to improve the robustness and security of AES. We have generated a set of polynomial combinations which can give S-box with much improved SAC. Thus, improving the avalanche criteria of S-box will make AES more robust and secure.