Towards robust image watermarking: combining content-dependent key, moment normalization, and side-informed embedding

In digital watermarking, robustness is still a challenging problem if different sets of attacks need to be tolerated simultaneously. In this paper, we deal with this problem by using an integrated solution involving side-informed embedding, moment normalization, and content-dependent watermarks. First, a new image watermarking method based on the concept of communications with side information is proposed. We investigate the characteristics of mean filtering in formulating new watermark embedding and extraction processes. Second, regarding resistance to geometrical attacks, we do not rely on the concept of pilot signals because they are vulnerable to synchronization removal attacks. We instead use block-based watermarking and moment normalization mechanisms to recover geometrical distortions. Third, regarding resistance to the copy attack, the content-dependent watermark is employed to avoid treating an un-watermarked image as one that has been watermarked. The robustness of our approach has been verified using both the StirMark and the copy attack.