Enhancing the security of AES through small scale confusion operations for data communication

Abstract

With the advent of computers, networks, distributed systems and wireless data transfer technologies, data communication is subjected to potential threats and hence needs to be protected. Advanced Encryption Standard (AES) is an efficient encryption algorithm used for secure wireless communication, but its security is under threat due to different forms of theoretical and practical attacks such as linear cryptanalysis, differential cryptanalysis, boomerang attack, truncated differentials, hybrid attacks, related-key distinguishing attack, and side channel attacks. This work is focused on reducing the attacks by increasing the complexity of cryptanalysis through small scale variations in the shift row transformation and key expansion unit of the AES algorithm. The proposed small scale variations in the linear layer of the cipher unit and in the word column of key expansion unit enhances confusion during encryption. The inherent diffusion property of the algorithm along with the proposed confusion characteristics allows us to increase the overall security of the algorithm. The confusion and diffusion characteristics of the modified algorithm are found to be higher in terms of balance, Strict Avalanche Criterion and bit independence criteria. The AES variants are also tested using NIST-800-22 statistical test suite for random number generators, the small scale variations made in the architecture provides a higher degree of randomness in the ciphertext thus increasing cryptanalysis complexity. This paper also proposes an obfuscation control unit that allows on-demand selection of the three AES variants resulting in a variable encrypting pattern for a plaintext-key pair thus adding more bottlenecks to the adversaries.