Research On The Watermarking Scheme In The Encrypted Domain

The rapid development of Internet and multimedia technology provides free access to digital contents in delivery and usage. Meanwhile, it makes the digital contents easy to be duplicated and tampered. The copyright protection problem of the digital contents is paid more and more attention, and digital watermarking technology is one of the important methods to solve this problem. At present, the research on digital watermarking focuses mainly on the conventional watermarking algorithms. However, according to watermarking protocols, the research on the watermarking scheme in the encrypted domain is comparatively less. A good digital watermarking protocol needs the support of the watermarking scheme in the encrypted domain in order to be applied to the practical digital contents trade. In this thesis, firstly an in-depth study of the existing watermarking protocols is provided, and then some principles in designing watermarking protocols are generalized, based on the analysis of three watermarking protocols presented by Memon and Wong, Lei et al., and Zhang et al. respectively. Secondly, an existing watermarking scheme, Solanki et al.'s SEC scheme, is enhanced in terms of reducing computing overload and increasing effective watermarking capacity. Thirdly, according to some important properties of the public key cryptosystems used in watermarking protocols and based on the enhanced scheme, a new watermarking scheme in the encrypted domain is proposed. With flexible watermarking capacity, the new watermarking scheme in the encrypted domain improves the robustness of watermarked image against JPEG compression after decryption, and it enables image tampering detection with blind watermark extraction. Experimental results demonstrate that the new watermarking scheme in the encrypted domain outperforms a previous scheme presented by Kuribayashi and Tanaka. Therefore, the proposed watermarking scheme in the encrypted domain is a suitable solution to applying existing watermarking protocols to the practical trade.