Research On The Digital Watermarking Theory And Algorithms

With the widespread distribution of digital media contents, the protection of the intellectual property rights has become increasingly important. Digital media offers several distinct advantages over analog media, such as high quality, easy editing, high fidelity copying. Digital information can be duplicated and distributed easily has led to the need for effective copyright protection tools. Cryptography can do nothing in resolving above problems, but digital watermarking which is one of the research focus in the academic world presents a candidate key to those questions.What digital watermarking technique mainly research on is still images, video and audio signals. The study object this file is still images which are most researchers discussed on because of its convenience. The focus of this dissertation is the theories and algorithms of digital image watermarking based on many research works of a lot of academicians and experts. The key points of research addressed in this proposal are as following:1. Double stochastic matrix can map every watermark image points to the corresponding point of the host image. In this way, watermarks can be distributed all over the original image and it's difficult for attackers to remove or change watermarks even if he has the full knowledge of the verification algorithm owing to the deficiency of the secrete key. An asymmetrical watermarking algorithm is also proposed in this file that combines this kind of matrix with modulations.2. A public digital watermarking scheme based on multi-signature is presented. The main idea of this scheme is that secrete keys used to embedding are kept secrete by different person, while anybody holding the public key can pick-up watermarking information from watermarked images.3. Give out a digital watermarking embedding and detection scheme with several arbitrators. The key used to detecting watermarks is divided into several key segments, and kept by different users or arbitrators. This scheme realizes secrete sharing and guarantees the detection process can be done only when there are several different persons.4. Put forward a digital watermarking combined Merkle-Hellman knapsack system with modular arithematic. If an attacker want to destroy thewatermarks he will face to dual NP: the knapsack problem and the discrete logarithm problem.5. Bring forward a new digital watermarking scheme in which the embedding position is determined by the different value of the gray of the images blockwise. And compute the DCT transformation to those selected blocks, and then embed watermarks into the middle coefficients. It can give little degrade to the original image, and can effectively resist non- geometric attack and lossy compression.6. Introduce the image confusion techniques into digital watermarking system, and obtains an embedding algorithm which is adapt to colored images.