The Study Of The Fragile And Semi-fragile Digital Watermarking Technique

As an effective means of a protection of the intelligent property right for the digital products, the digital watermarking technique got the extensive concern, and has become the international research focus in the academic circles. Based on the research with the digital watermarking technique particularly the authentication watermarking technique, the thesis put forward two kinds of digital watermarking projects of the integrated authentication of digital image: fragile and semi-fragile digital watermarking and pointed out its limits through analysis of current typical model calculation ways home and abroad from different angles. On this foundation, we attempted to built up a fragile watermarking algorithm according to the chaos system and a semi-fragile watermarking algorithm according to the invariant property to JPEG lossy compression, carried out the analysis to its experiment and proved the rationality of this algorithm. This research will play an effective role in the promotion and application of the digital watermarking technique. The thesis mainly includes the following parts:1. The research contents of information hiding were presented, considering the complementary role of the digital watermarking and information hiding technique. We summarized the general model of information hiding, investigated the digital watermarking theories systematically, summarized the general theory and general models of the digital watermarking, pointed out its main foreground of application and analyzed typical algorithm of various kinds and main attack method of the digital watermarking.2. Fragile and semi-fragile digital watermarking techniques were analyzed in detail. In addition, we summarized the basic frame of it and related requirements of the two algorithms and discussed the recent development of the two kinds of watermarking techniques systematically in the last few years and analyzed the attack behavior to the watermarking at integrated authentication that the authentication watermarking be subjected to.3. We put forward a fragile digital watermarking algorithm of still image according to the chaos system. The watermarking signal was made according to the image contentsbased on the characteristics of being non-periodic, non-constringency and sensitivity to the initial value of the model of Logistic. And based on the nature of reproduction and sensitivity to the initial value of Logistic chaos sequence, Logistic chaos initial value is the key of the customer according to the systemic choice; hence making the algorithm public.4. We put forward an algorithm for semi-fragile watermarking of still image according to the invariant property to JPEG lossy compression and based on the invariant property to JPEG of the coefficient of DCT, which enables the real blind examination and provides good guarantee for the safety of the system to the control of the key at the same time; Moreover this algorithm obtains the good balance in the robustness and fragility-the algorithm has the very strong robustness to the non- malicious attacks and the good ability in the identification and position to the malicious attacks.Last, the thesis carried out a summary of the possible research direction of digital watermarking technique and pointed out further academic direction. The fragile and semi-fragile watermarking algorithm of the thesis has already been applied in the VC++6.0 platform, which was validated by experimental results and proved to be satisfactory.