When Robust Reversible Watermarking Meets Cropping Attacks

A robust reversible watermarking (RRW) algorithm enables the extraction of the watermark and the restoration of the cover image without attacks while ensuring the watermark’s extraction when the image is under attack. Existing RRW methods mainly focused on achieving robustness against geometric attacks such as rotation and scaling by embedding watermarks within the global inscribed circle of an image. However, the geometric transformations targeted by the existing methods cannot cope with combined attacks that include cropping, which is a real application scenario for geometric attacks. To extend the robustness of the watermarking algorithm, this paper proposes a local Zernike moments (ZMs) embedding strategy based on feature point extraction and selection. For each local circular domain, the same watermark is embedded in the magnitude of the ZMs. After embedding, all the compensation information used to recover the robust embedded regions is embedded outside these local circular domains in a reversible way. When attacks occur, especially combined attacks involving cropping, by using side information, the local watermarked regions in the image can be localized to extract the robust watermark. Experimental results show the superiority of the proposed method under various combined attacks that include cropping operations.