Advanced Key Expansion Algorithm Using a High-Performance Four-Dimensional Chaotic Map and a Strong S-Box for Enhanced Sensitivity and Independence

Abstract The round key is pivotal to the integrity of block encryption algorithms, derived from the initial key via the key expansion process to enhance security measures. This study introduces an innovative key expansion algorithm, underpinned by a high-performance four-dimensional chaotic map and a durable S-box, distinguishing itself through key sensitivity and independence, thereby enhancing defense against diverse cryptographic attacks. We debut a four-dimensional chaotic map, lauded for its exceptional dynamic qualities as evidenced through rigorous behavior analysis. Furthermore, we develop an S-box generation method utilizing operations in the finite field GF(2⁸), producing an S-box characterized by its high nonlinearity and fortified security. This S-box is meticulously designed to avoid common vulnerabilities such as fixed points, reverse fixed points, and brief periods, rendering it ideal for key expansion purposes. Leveraging the strengths of the chaotic map and S-box, we detail our key expansion algorithm and validate its security efficacy through comprehensive analysis, highlighting its potential as a robust tool in cryptographic security.