Assessing the Impact of Increased MixColumns on AES Encryption Security and Performance

This work focuses on the influence of design changes in the 192-bit AES, specifically in the MixColumns step, aiming to enhance security metrics. We evaluated key parameters such as entropy, avalanche effect, Key Input Variation Analysis, and execution time. Our results suggest that entropy due to the proposed change in the AES ranges approximately from 4.0535 to 4.4183, compared to the standard AES range of approximately 3.9183 to 4.3349. The average avalanche effect ratio improved to approximately 0.5094 from 0.4844 in the standard AES. Additionally, the Hamming distance increased to approximately 75.4 from 71.6, indicating higher sensitivity to input changes and better resistance to differential cryptanalysis. These enhancements in security, however, come with an approximate increase in execution time of 10%, which is significant. Despite this, the performance trade-offs may be justified for the improved security observed in this study. Nonetheless, the increase in execution time remains a crucial consideration when selecting the modified AES for specific applications. These findings provide valuable insights for decision-makers balancing the choice between highly secure cryptographic techniques and optimal performance.