Research On Applications Of Chaos In Digital Image Watermarking Algorithms

Digital watermarking technology is a hotspot in academic fields. The thesis focuses on the applications of chaos in digital watermarking algorithms. Firstly, the basic concepts, algorithmic block diagram and application areas are introduced; then the chaos idea, typical features and the present situation of its applications in fragile digital watermarking are described; lastly, a novel image scrambling matrix and two kinds of new fragile watermarking algorithms based on chaos are proposed.The novel image scrambling matrix T has the same characteristics of easy coding and decoding with Arnold matrix. This thesis presents the T conformation method, proves that the T-based transform possesses periodicity. Extensive computations are made and the results show that: When the matrix order is bigger than or equal to 3 and the module parameter is integral power of 2, the period of T-matrix-based transform is two times of Arnold's. Image scrambling approach by T matrix can be used in watermarking pre-processing and image encryption.Since chaotic systems are sensitive to its initials, a novel fragile watermarking algorithm based on chaotic characteristic is proposed. The watermark image is pre-processed by chaos means, then the watermark is embedded into the host image in space domain. This algorithm is transparent to human eyes and sensitive to minor tampers. No original image is needed in extraction process. Computer simulations show that: This algorithm is very secure and can authenticate image integrity effectively. This method can be used in the situation when the high integrity requirement is needed.The second proposed algorithm embeds a chaotic watermark to the host image in the wavelet domain. This blind algorithm is sensitive to minor tamper, and can get exact tampering locations. Simulation results show that: This method is very secure, it can survive JPEG compression of 73% remaining quality and resist some noise. This method can be used to authenticate the transformed images and the images in databases. ...