A refined sine-derived chaotic map for securing medical image encryption in telemedicine.

Telemedicine has revolutionized healthcare by enabling remote diagnostics and treatment; however, it also raises significant concerns regarding the security of transmitted medical data. In response, this paper introduces a novel encryption framework specifically designed to safeguard medical images during transmission and storage within telemedicine platforms. At the core of this framework lies a newly developed one-dimensional chaotic map, referred to as the IS map, which combines two sine functions with a Chebyshev polynomial to achieve enhanced chaotic behavior. Compared to existing chaotic maps, the IS map demonstrates superior unpredictability, greater ergodicity, an expanded chaotic range, more intricate dynamics, and competitive computational complexity. The IS map is employed in the initial phase of encryption for pixel-level permutation, ensuring robust diffusion. This is followed by a bitwise XOR operation controlled by a random matrix generated from a pseudorandom number generator (PRNG), along with pixel-level substitution to further strengthen confusion and enhance security. Moreover, the SHA-256 hash function is utilized to generate one-time keystreams tailored to each image, thereby ensuring a highly individualized encryption process and strong resistance to differential attacks. Extensive performance evaluations confirm that the proposed scheme achieves an optimal balance between security and computational efficiency, outperforming state-of-the-art algorithms and making it particularly well-suited for real-time telemedicine applications.