Hash Function-Based Multi-Layer AES Key Expansion Framework

Abstract

The advanced encryption standard (AES) is one of the most commonly used encryption algorithms because of its effective encrypted capabilities and strong crypto-security. Due to the growing demand for stronger cryptographic protection, researchers have been finding alternative enhanced key management and key expansion methods that will improve randomness, nonlinearities, and statistical security properties within the framework of AES.In this paper, we proposed a hybrid SHA3−AES framework that utilizes three complementary techniques for strengthening AES. SHA3 is utilized to preprocess the master key to produce a hardened key with higher entropy; dynamic external key evolution employs iterative hashing with SHA3 to produce round dependent keys, thus reducing the number of deterministic relationships that exist between round keys; and SHA3 is also incorporated into AES's internal key expansion process to provide increased non-linearity and complexity for generating round keys. The objective of the proposed framework is to enhance diffusion characteristics of the process and increase randomness of the encryption process while preserving the original AES structure. Security analysis indicates that integrating SHA3 improves key unpredictability and strengthens random behavior through dynamic key dependency and continuous key evolution. Furthermore, experimental observations show that the proposed framework provides substantial improvements to the statistical and security metrics (i.e., entropy, avalanche effect, and randomness distribution) when compared to the traditional implementations of AES. Results indicate that the proposed SHA3-AES model provides a second layer of security for applications with the need for a higher level of security against advanced analytical attacks.