A Novel Hybrid Chaotic Map and Cryptographic Hash Whitening for Optimized S-Box Design: Construction, Cryptanalysis,...

In this work, a novel method was introduced for the construction of the S-box based on delayed nonlinear chaotic systems coupled with a hybrid hash whitening mechanism. The evidence for strong nonlinear dynamical behavior is the strongly positive Lyapunov exponent with uniform statistical distribution of the generated binary sequence. Optimized 8-bit → 8-bit S-boxes, displayed in 16 × 16 hexadecimal format, were achieved by applying Fisher-Yates permutation to the chaotic sequences and further enhancing them with affine transformations over GF(2). Nonlinearity, differential uniformity, avalanche effect, strict avalanche criterion, linear approximation table, difference distribution table, and algebraic degree are cryptographic metrics that reveal very strong resistance against linear and differential attacks. Image encryption with the generated S-box further validates the confusion properties. The results confirm that the hybrid approach achieves high-quality S-boxes suitable for symmetric cryptography.