The Design And Implementation Of Digital Watermarking Algorithm Robust To Geometric Attacks

With the rapid development of information technology, digital media has been been playing an increasingly important role in people’s daily lives.However, due to the fact that digital media products are very easy to be modified, reproduced and disseminated illegally, so they provide convenience and cause tough information security problems at the meantime. In order to solve these problems, digital watermarking technology has been studied extensively in recent years.In the public watermarking scheme, the loss of the synchronization, between watermark embedding and detection stages, easily causes watermark detection error. Geometric distortions, such as rotation, scaling, translation and any other affine transformation, are principal factors of this problem, however, this type of distortion is common in practice.Two watermarking schemes against geometric distortions and several attacks of signal processing are proposed. In the first proposed watermarking approach, image normalization theory is used to get geometric invariant region and watermark embedding and detection are carried out in the Discrete Cosine Transform (DCT) domain. Texture based image block classification in DCT domain is also used to get major watermark imperceptibility. And this scheme is a blind watermarking, where the original image is not available in the watermark detection stage. The second approach proposed a method to estimate watermarked image’s geometric distortion factors and corrected it by using SIFT features matching, achieving the synchronization between watermark detection and embedding phaseThe experimental results show both of the scheme’s watermark imperceptibility and robustness against geometric distortion such as rotation, scaling and various other Affine Transformation,and common signal processing attacks, such as JPEG compression, noise contamination and print-scan.