A secure and privacy-preserving technique based on coupled chaotic system and plaintext encryption for multimodal medical images

In medical diagnosis, colored and gray medical images contain different pathological features, and the fusion of the two images can help doctors make a more intuitive diagnosis. Fusion medical images contain a large amount of private information, and ensuring their security during transmission is critical. This paper proposes a multi-modal medical image security protection scheme based on coupled chaotic mapping. Firstly, a sequentially coupled chaotic map is proposed using Logistic mapping and Cubic mapping as seed chaotic maps, and its chaotic performance is verified by Lyapunov index analysis, phase diagram attractor distribution analysis, and NIST randomness test. Secondly, combining the process of image encryption with the process of image fusion, a plaintext-associated multimodal medical image hierarchical encryption algorithm is proposed. Finally, a blind watermarking algorithm based on forward Meyer wavelet transform and singular value decomposition is proposed to embed the EMR report into the encrypted channel to realize the mutual authentication of the EMR report and medical image. The experimental results show that compared with the related algorithms, the proposed algorithm has better encryption authentication performance, histogram, and scatter plot are nearly uniform distribution, and the NPCR and UACI of plaintext sensitivity and key sensitivity are close to 99.6094% and 33.4635%, respectively, and has strong robustness to noise attacks and clipping attacks.