Digital Watermarking Technique Based On Chaos And Its Application In Military Communication

In this thesis some studies of digital image watermarking algorithms based on discrete cosine transform (DCT) and the corresponding applications in military concealed communication system are presented.Based on the research on the existing Digital Watermarking schemes, the methods of image information hiding are analyzed by using discrete cosine transform (DCT). It is found that the hidden information amount of the existing algorithms is not large enough, lack of safe, not satisfied at the military concealed communications. In order to increase the amount of hidden information, this thesis presents a new blind watermarking algorithm based on DCT (Discrete Cosine Transform) and focuses on analyzing the embedding method and chaotic encryption. The proposed embedding and extraction algorithms use modular operation and image processing operations for the marked image, the experiments results show that the scheme is robust against JPEG compression, cropping and noise disturbance. At the same time, the larger the modular is, the poorer the transparence of the scheme is, but, clearer the extracted watermark from the marked image is. To enhance the security and random of the proposed scheme the chaotic map is employed. Chaotic sequence is of simple and hypersensitive to the original value, and the orbit is uncertain. Those characters are very suitable for the encryption of the watermarking. Chaotic sequence is used in the following ways: the original mark is first disordered and then the modified DCT blocks are selected. Simulation results illustrated that the correlation between the disordered and the original mark is largely reduced. The experiment results and the corresponding data are given.The military concealment communication system is designed based on the proposed digital watermarking technique. The corresponding design principle and framework structure and main functions of the communication system, the development tools and the running environment are given in this thesis.