Recovery of Watermark Using Differential Affine Motion Estimation

Digital watermarking techniques have been proposed to protect the copyright of multimedia data. Robustness against geometric distortion is one of the most important issues to be solved to increase the robustness of digital image watermarking systems. Such attacks are very simple to implement, so they can defeat most existing watermarking algorithms without causing serious perceptual distortion. In this paper, a method for the recovery of watermarks based on differential affine motion estimation is presented. This method models the geometric distortion between images as locally affine but globally smooth. This approach is built upon a differential multiscale framework, allowing us to capture both large-scale and small-scale transformations. Experimental results show that the described method can estimate the distortions quite accurately and allow correct watermark detection.