Hiding Information Based On Gray System Theory

Information hiding technology is an important study direction of information security field, and furthermore this technology based on image is also one of the hotspots being researched at present. Since this kind of technology is mainly used in secret communication, copyright protection and authentication, it is of great theory significance and high practical value. In this thesis we primarily discuss the characteristics, sorts, and research methods of grey relational analysis theory, and also the characteristics of information hiding of image in DWT domain, and thereby successfully apply the grey model to the information hiding technology. The main work and innovations are as follows:1. Mainly study the methods of the grey relational analysis. The thesis is about the research on the information hiding algorithm, using images as the cover signal, primarily based on the grey relational analysis theory. Therefore, firstly introduce and explain some relative theory about grey relational analysis, putting emphasis upon the concrete approaches. Meanwhile analyze the feasibility of applying grey relational analysis in the image processing field, and also give some simple discussion on some key problems, making some preparations for the research work in the theoretical aspect.2. Considering the characteristics of human visual system, the information hiding algorithm is presented based on grey relation and locally wavelet transform. It has three points: First, in carrier image, we choose parts of relatively non-smooth areas to hide information on the basis of grey relational grade. Second, some high frequency coefficients, whose absolute values are as large as possible, are chose as the embedding positions in the sub-images' DWT domain. Third, based on visual masking character in DWT domain, the intensity of embedded information is made sure. The experiment results show that the algorithm is not only invisible, but also robust against various signal processing such as noise adding, cropping, JPEG compression, and filtering.3. The thesis demonstrates the information-hiding blind-extraction algorithm of color image in DWT domain based on grey relation. Based on grey relational theory and the characteristic of information hiding, a new definition of grey relational coefficient is presented. Based on this definition, the hiding algorithm in this thesis hides the secret data though changing the HL and LH frequency band coefficients of original carrier...