An Applied Research In The Technology Of Digital Watermarking Based On DCT Domain

Information security protection technology is now attracting more and more attention in this Information Age. The demand of copyright protection, secure transmission and confidential communication is increasing dramatically as the multimedia technology widely spreaded. Most of conventional information security techniques are based on the theory of Cryptology. It is obvious that with the calculating ability of modern computers rapidly improved, there is less possibility to keep security. Digital watermark is a security technique which used to protect some information such as privacy, authority through embedding watermark into target mediators.In this thesis we applied digital watermark technique and fingerprint identification technique in ownership verification of certificates. The image of owner's fingerprint was embedded as watermark into the photo which is to be used in certificate making. After that we compare the watermark with the fingerprint we got.A novel algorithm was proposed in our work by discrete cosine transformation (DCT), still image compression coding technique, and human visual system (HVS) to calculate the position embedded. The DCT is applied in blocks of 8×8 pixels in this approach. Texture blocks of the host image are selected as target positions, and then the watermark was inserted in the DCT high and middle frequency of those parts with scrambling technique. The extraction and detection of the watermark does not need the original image. The experiment results show that the algorithm we use meets the demand of transparency and robustness effectively: the watermark can be detected even the watermarked image was compressed, clipped or filtered greatly.