Hybrid medical image self-embedding watermarking encryption scheme based on strong S-box

As a newly emerging pillar industry in the medical field, telemedicine relies on the Internet and other transmission networks to complete the transmission of patient information and obtain the consultation results of telemedicine experts, which greatly improves the guarantee of patients' lives. At the same time, the secure transmission of medical data is also one of the important standards of telemedicine, because any attack or theft caused by the loss of small details, changes, or information leakage will affect the direction of treatment, resulting in serious consequences. Therefore, a new digital watermarking scheme for medical images is proposed in this paper, which combines image encryption and watermarking protection techniques. In the watermarking aspect, the Canny operator is used to obtain the self-embedding watermark image that is highly related to the plaintext, and the watermark embedding is realized by non-subsampled contourlet transform, discrete wavelet transform, Fourier transform, and other operations. An efficient S-box is constructed by using the generated chaotic sequence and the improved Z-transform, which fully disrupts the arrangement position of image pixels, and uses two-way diffusion to complete the distribution of plaintext information in ciphertext to realize image encryption. Simulation results and related tests show that the algorithm can successfully encrypt color and grayscale medical images and has good robustness and ability to resist various external attacks.