A ROI-based medical image encryption scheme using improved Lorenz chaotic system, hybrid pixel-bit permutation, and SHA-256 hashing

  • Huiqing Wu Shandong University of Engineering and Vocational Technology, Jinan 250200, China
  • Xiaohong Wang Shandong University of Engineering and Vocational Technology, Jinan 250200, China
Article ID: 3511
DOI: https://doi.org/10.59400/adecp3511
Keywords: medical image encryption; region of interest (ROI); improved Lorenz chaotic system; hybrid pixel-bit permutation; SHA-256 hashing; bit-wise diffusion; differential attack resistance

Abstract

Medical images contain highly sensitive diagnostic and personal information that requires robust protection during storage and transmission. To address this, we propose a region-of-interest (ROI)-based hybrid encryption algorithm that combines pixel-level and bit-level permutation with bit-wise diffusion driven by an improved Lorenz chaotic system. The scheme first employs a robust ROI perception mechanism to accurately identify diagnostically important areas while avoiding unnecessary processing of non-critical regions, thereby enhancing computational efficiency and security. Image-dependent SHA-256 hashing is integrated to generate keystreams tightly bound to image content, improving key sensitivity and resisting plaintext attacks. Dual-layer chaotic scrambling ensures both global confusion and local diffusion, while a dedicated bit-wise diffusion stage further randomizes the ciphertext, strengthening resistance against differential, statistical, and noise-based attacks. Experimental evaluations demonstrate that the proposed method achieves high security and robustness: the average information entropy of encrypted images reaches 7.9992, and NPCR and UACI values are 99.63% and 33.47%, respectively. Compared with existing encryption techniques, the proposed algorithm exhibits higher randomness, stronger differential attack resistance, and better protection of sensitive medical data, without embedding ROI location metadata into non-interest regions. The results indicate that this approach provides an efficient and secure framework for safeguarding medical images in telemedicine, healthcare information systems, and other critical applications.

Published
2025-10-13
How to Cite
Wu, H., & Wang, X. (2025). A ROI-based medical image encryption scheme using improved Lorenz chaotic system, hybrid pixel-bit permutation, and SHA-256 hashing. Advances in Differential Equations and Control Processes, 32(4). https://doi.org/10.59400/adecp3511
Issue
Vol. 32 No. 4 (2025)
Section
Article

Copyright (c) 2025 Huiqing Wu, Xiaohong Wang

Creative Commons License

This work is licensed under a Creative Commons Attribution 4.0 International License.

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