Improved AES algorithm based on dynamic row displacement and SHA-256 key extension

This paper aims to enhance the security of the Advanced Encryption Standard (AES) by introducing two key improvements to the traditional fixed row shifting and key expansion methods. First, a dynamic row shifting technique is adopted, which determines the row shift amount based on the sum of each row's data modulo 4, thereby increasing randomness and making attacks more complex. Second, the Secure Hash Algorithm (SHA-256) is introduced into the key expansion process, selecting different bits of the hash value based on the expansion round to form the next round key, thus improving key unpredictability. Theoretical analysis and experimental validation demonstrate that the improved AES algorithm significantly enhances resistance to brute force attacks and increases encryption strength. Although there is a slight decrease in computational efficiency, the enhanced security is notable. This research provides a new approach for the field of cryptography, contributing to further improvements in the security and practicality of encryption algorithms