Research About Complementary Algorithm And Watermark Robustness

With the development of information network technology,especially the Internet,the security and copyright protection of digital media have been more and more important around the world.Digital watermarking can solve the problem by embedding the secrete information in the original data.It's a novel and effective technology,and it is widely used in the security and copyright protection of digital media.This thesis researches the digital watermark robust- ness and complementary algorithm.Firstly,we analysis and improve an image watermark algorithm based on chaos.Because chaos is sensitive to first value,we use the first value as a private key,and not need the original image to extract the watermark,then the security and robustness are improved.Secondly,we analysis robustious watermark structure from the point of view of entropy,and put forward an algorithm to resist the collusion auack.We use the theory of compages to create DBBD code as digital fingerprint,which make different collusion user group have different set.The code put right,then the watermark will have good robustness.Finally,this article proposes complementary watermark algorithm based on the chaos and wavelet transform.For keeping the watermark's security and random,we use bipolar watermark and confuse it by chaos sequence.We select those wavelet coefficients more than the JND in the host image to embed watermark.Therefore the watermark is undetectable.Furthermore,two modu- lation rules are used:positive modulaion and negative modulation,which simultaneously hide two complementary watermarks in the same host image so that at least one watermark survives under different aRacks.Experimental results confirm that the complementary watermark scheme can be robust todifferent kinds of attacks.