Based On Wavelet Transform Robustness And Fragility Of Digital Watermarking Algorithm

Along with the development of computer network, multimedia and information science, problems brought by copyright protection of digital media have become more and more serious. Traditional security system of information can only safeguard information transmitting process, so they can't be fit for requirements of new condition. As a key to solve copyright problems, watermarking technologies attract more and more attention.First, this paper introduces background of research in digital watermarking technologies; include types of digital watermarking and their principle, as well as application fields.This paper approves two kinds of wavelet-based schemes of digital watermarking. They belong to fragile watermarking and robust watermarking. The paper research these on system based on DWT in the fields of HVS, energy of image watermarking, coding and cryptography etc, which can aplly in practice.By the background of ShangHai Maritime University Digital Library Project, 1 completely study existed watermark arithmetic, approve two significative arithmetic. First, I develop a robust watermark arithmetic "Arithmetic of Adaptive Public Watermarking Based on Watermark-energy and HVS". Second, develop a semi-fragile watermark "Content Authenticate and Blind Reconstruct Based Semi-Fragile Watermark System".With regards to robust arithmetic, an embedded-coding watermark algorism based on HVS and watermarking energy is presented. This algorism embeds watermark in key coefficients of wavelet domain of images, and it provides the mechanism of embedding the optimal intensity of watermark for users according to the PNSR and visual-masking eigenvalue given by users. The paper also employs and improves the idea of quantitive subsection embedding in the implementation of embedding watermark. Experiments results show that the method offers fine invisibility and robustness in image processing.Regarding to semi-fragile arithmetic. We introduces the technique of noise separation to deal with the wavelet coefficients, and uses the morphological theory to screen and select the characteristic coefficients, which ensure the robustness of the above mentioned coefficients. On the base of the method, we encode the selected characteristic coefficients with the error correction code, in the meantime embeds into images the error correction bits that are subject to the processing of dispersal. Authentication of image content using PKI can locate actual places of the tampering and rehab the image, but also fortify the security and integrity of the system.This paper's watermarking arithmetics are all run in Matlab environment. All the experimentation result show that this paper's static image watermark based on wavelet potential application promises well.