Research On Digital Watermarking Techonology For Image Copyright And Content Protection

With the penetration of information technology, digital media is playing an increasinglyimportant role in the exchange of information. However, digital media can be easily copied ortampered with. Security is seriously threatened. The digital watermarking technology providesan effective way to protect copyright and content of digital media, becoming a hot research fieldof information security.With the object of the digital image, this paper makes a study of the robust watermarkingfor copyright protection and the fragile watermarking for content protection. Firstly, the basictheory and classification of digital watermarking are briefly introuduced. The research status andexisting problems of digital watermarking for copyright protection and content protection areanalyzed. On this basis, the work of the following aspects is mainly completed.(1) Copyright protection. A zero-watermarking algorithm based on local affine invariantfeature region is put forward. Affine invariant regions are extracted in the low-frequency domainof Lifting wavelet transform, and the watermarking is constructed by DCT coefficients withlarge absolute value in every characteristic region. The algorithm combines the advantages of thesecond generation of digital watermarking and the zero-watermarking algorithm, which obtains astrong ability to resist geometric attacks, without causing any distortion to image content.(2) Content protection. A recoverable fragile watermarking algorithm, which can positionthe image content tampering accurately, is put forward. The algorithm accurates the tamperingauthentication unit to2×2image block. The authentication watermark is generated by chaoticsequences based on the content of the image block, the only index of the image and the imageblock number, which is with higher security. The watermark is embedded in its own blockimage,and authenticates tamper with the neighborhood-block-based optimization proposal,improving the reliability of tampering authentication. Recovery watermark is formed bynon-uniform quantization method and embedded into the block of offset. With the selection ofthe offset value, a program based on chaotic map and linear function is proposed, whichimproves the security of recovery watermarking and the quality of image restoration.(3) Based on the proposed robust watermarking and fragile watermarking algorithm, thefeasibility of a combination is analyzed. Then a digital watermarking prototype system for imagecopyright and content protection is designed and implemented. The system can protect thecopyright and the content of the same image, while the two functions doesn’t affect each otherand are not necessarily in sequence.