Research On Image Digital Watermarking Based On Copyright Protection

Digital watermarking is an important branch of information hiding.It is an effective method for protecting copyright and tracing piracy.Essentially,watermarking is defined as the process of embedding secret information directly into digital multimedias(such as stationary image,audio,or video signal.) and the secret information can not be perceptual by human perception system.Moreover,it is difficult to remove or spoil the digital watermarking.In copyright protection application field,there are three requirements to digital watermarking system: imperceptibility of the watermark within the host signal,the security of the watermark against attacks and robustness to signal processing.On the premise of those,the watermarking capacity should be as high as possible.In this thesis,the research on image digital watermarking based on copyright protection and its zero-knowledge proofs are performed.The main contributions are summarized as follows.1.To do researches on the basic theory of digital watermarking system, including digital watermarking generating,embedding and extracting techniques.To maximize the detection probability or to minimize the probability of detection errors,a further research on multiplicative embedding rule,the corresponding robust optimum detections and the method for obtaining a thresholds under a given false alarm rate based on the distribution models of the coefficients of transform domains are performed.2.Combining pseudorandom scramble techniques,a digital watermarking scheme based on error control code is proposed.In fact,digital watermarking system can be looked as a communication system.In order to decrease the watermarking transmission errors and to improve its security and transparence,it is necessary to adopt error control code techniques,The original watermarking image can be firstly scrambled by using pseudorandom sequence.Thus,the performances of the security, the transparency and the resistance to cropping of the watermarking are improved greatly.3.A spread spectrum digital watermarking scheme based on chaotic scramble and hybrid transform domains is presented.The spread spectrum technique has many advantages,such as the resistance to interference,signal attenuation and the multiple access interference.The chaotic scramble techniques can improve the security and the robustness against cropping.DWT has multi-resolution characteristics and DCT has the capability of compressing energy and de-correlation.It is shown from the experimental results that by using the proposed scheme,the security and the transparency of the digital watermarking are improved greatly.And the robust to geometric distortion(cropping,translation,rotation) and the common signal operations (adding noise,JPEG compression and filters) is enhanced largely.Even the quality of the watermarked image is degraded severely the watermarking can be extracted very well.4.Turbo code and CDMA basis digital watermarking scheme is presented. CDMA is an efficient communication means,which has the merits such as resistance to noise and interference,the good transparence,multiple access,high capacity and so on.When it is applied to watermarking system,the performance of the security,robust and capacity of the watermarking is enhanced greatly.At the same time,for the purpose of decreasing the multiple access interference,a good encoding method(such as Turbo code) is adopted to lower the detection threshold.Moreover,the improvement on the encoding performance enhances the capacity of the CDMA system directly.5.For a CDMA digital watermarking system,if you want to embed a large number of digital watermarking data into a certain amount of coefficients selected from transform domains,some problems will occur.Here three effective measures are adopted.Firstly,the watermarking groups are constructed by using descending sort or ascending sort.In the process of extracting watermarking,the interference signals can strengthen the being extracted signal.As a result,the quality of the extracted watermarking can be improved greatly.Secondly,the CDMA encoding sequence is added or subtracted an integer before it is embedded into the initial host image.So,the PSNR of the watermarked image can be increased.Thirdly,the influence of the MAI can be decreased by using linear minimum mean square error estimation.The experimental results show that the watermarking system do has a high watermarking capacity.And the watermarked image has too little distortion to find by human visual system.At the same time,the watermarking has a good robust performance against various attacks.6.Under the foundation of secure commitment and RSA public key mechanism, zero-knowledge watermarking verification protocols are proposed.The first two protocols adopt multiplicative watermark embedding rule and the corresponding robust optimum detection based on the distribution models of the transform coefficients.On the other hand,a CDMA basis zero-knowledge digital watermarking verification protocol is presented.All the proposed protocols ensure that a prover soundly convinces a verifier of the existence of a watermarking in a certain stego-data without revealing any knowledge(including the watermarking information,watermarking embedding position and watermarking extracting keys) that a malicious attacker can use to modify,spoil or remove the watermarking.It is shown from the security analysis that the proposed protocols do have the qualities:completeness,soundness, zero-knowledge,robustness and applicability.