Research On The Technology Of The Multimedia Security Based On Digital Watermarking

The rapid growth of digital information, the increasingly easy access to digital media, and the increasingly powerful tools available for manipulating digital media have made multimedia security a very important issue. Digital watermarks have been proposed recently as the means for intellectual property right protection of multimedia data. Digital watermarking is a process of embedding information (or signature) directly into the media data by making small modifications to them. With the detection/extraction of the signature from the watermarked media data, it has been claimed that digital watermarks can be used to identify the rightful owner, the intended recipients,as well as the authenticity of a media data. The watermarks can be perceptually visible or invisible. We focus on invisible watermarks in this paper. In general, there are three most common requirements of invisible watermarks.1.Robustness: They should not interfere with the media being protected.They should also be robust to common signal processing and intentional attacks. Particularly, the watermark should still be detectable/extractable even after common signal processing operations have been applied to the watermarked image. These include filtering, compression, geometric transformation, cropping, etc. In addition, the watermark should be resistant to intentional attacks that attempt to remove the watermarks.2.Imperception: The watermarks should be perceptually invisible,i.e., there is no difference between the original image and the watermarked image in the vision.3.Security:The information embedded into the original data can't be destroyed under some human attacks,i.e.,the algorithm with a good attack-proof characteristic.The data hided in the multimedia should not be lost for the format transition of the documentation and detected without the authority.In this paper the new digital watermarking scheme is proposed based on the three facets above.The image data was scrambled and then embedded into the original dispersedly in the wavelet domain. We focus our attention on these topics:1.The general model, characteristic, class of the digital watermark are firstly discussed,and then the method for embedding and extracting is studied,the appraisal benchmark of DWS(digital watermark system) is picked up.2. Mathematics foundation. Because the watermarking algorithm is indeed a mathematical problem. On the other hand we mainly use wavelet transform in this domain we insert watermark. Besides it is applied in the JPEG2000, so this watermark scheme is immune to compression. So we review some mathematical foundation, then we can deal the problem easily in the consequence parts.3.Human Visual System(HVS).The characteristic of HVS is studied based on human eyes in order to do the more excellent DWS.Then we get the JND by Waston's Visual Meodel,at last it is proved that DWT is the most fit to HVS and the watermark embed in the wavelet domain has a better effect.4.The coefficient of DWT is carefully analyzed,and then which region for embedding the data into is choosed.At last we put forward the watermarking algorithm in wavelet domain.5.In this part the watermark scheme is carried out.It is resistant to the geometric attacks,noise-adding,compression,filtering,etc and has good performances.In the end of this thesis, I summarize my work in the period of postgraduate and have a look on the future work.