Improved RST-attacks resilient image watermarking based on joint SVD-DCT

The risk of copyright violation of multimedia data has increased due to the enormous growth of computer networks that provides fast and error free transmission of any unauthorized duplicate and possibly manipulated copy of multimedia information. In order to be effective for copyright protection, digital watermark must be robust which are difficult to remove from the object in which they are embedded despite a variety of possible attacks. Several types of watermarking algorithms have been developed so far each of which has its own advantages and limitations. Among this recently Singular Value Decomposition (SVD) based watermarking has attracted researchers due to its simplicity and some attractive mathematical properties of SVD. SVD-DCT based watermarking given by Sverdlov has limitation to high angle rotation, large degree scaling. Also translation attack is not done. In proposed improved RST attacks invariant image watermarking based on joint SVD-DCT, a preprocessing step before the watermark extraction is proposed which makes the algorithm resilient to geometric attack i.e. RST attack. Performance of this watermarking scheme has been analyzed by evaluating the robustness of the algorithm against RST attacks and some other attacks. Experimental results have been compared with existing algorithm which seems to be promising.