HYBRID AUDIO ENCRYPTION USING WALSH–HADAMARD TRANSFORM, HÉNON MAP, AND ADAPTIVE 3D LOGISTIC–SINE MAP

This paper presents a hybrid audio encryption algorithm that combines transform-domain processing with chaotic dynamics and adaptive key evolution. The proposed method integrates the discrete cosine transform (DCT) and the Walsh–Hadamard transform (WHT) to achieve efficient signal decorrelation, while permutation and diffusion are provided by chaotic maps. Chaotic permutation is performed using the Hénon map, and diffusion is achieved through an adaptive keystream generated by a three-dimensional logistic chaotic system enhanced with nonlinear logistic–sine modulation and CBC-based inter-frame diffusion. The algorithm was evaluated on speech signals from the VCTK corpus (16 kHz, 16-bit). Comparative experiments were conducted with several audio encryption schemes, including DCT+Hénon+logistic, WHT+Hénon+logistic, Hénon+LWT, EMD with a 2D cosine logistic map, and a hyperchaotic Rabinovich-based system. The proposed hybrid scheme achieves NPCR of 99.9977% and UACI of 33.2975%, indicating strong resistance to differential attacks. For 16-bit audio samples, the encrypted signals reach a Shannon entropy of 15.84 bits, demonstrating high statistical randomness. Additional tests show near-zero correlation between original and encrypted signals and successful passing of basic NIST randomness tests. These results demonstrate that combining transform-domain processing with adaptive chaotic key generation improves the security and robustness of audio encryption while maintaining practical computational performance.