A Robust Watermarking Algorithm for Encrypted Medical Images Based on DFT Encrypted Domain

Most of the existing robust watermarking schemes were designed to embed the watermark information into the plaintext images, which leads to a latent risk of exposing information and are vulnerable to unauthorized access. In addition, the robustness of watermarking in the encrypted domain is another issue that should be taken into account. Based on Discrete Fourier Transform (DFT) and Logistic chaotic map, we proposed a robust zero-watermarking algorithm in the DFT encrypted domain, which achieves good safety in the protection of both watermark information and the original image itself. Firstly, we encrypt the watermark and the original medical image in DFT encrypted domain. Then, the DFT is performed on the encrypted medical image to acquire the feature vector. In watermark embedding and extraction phase, zero-watermarking technique is utilized to ensure integrity of medical image. Experimental results demonstrate good robustness against both common attacks and geometric distortions.