Study On The Chaos-based Algorithms Applied To Image Security

For the properties of large volumes and real-time requirement, the data of multimedia are difficult to be encrypted by traditional cryptographies directly, which results in that image contents security and image copyright protection becomes a key and attractive problem. An efficient solution to implement image copyright protection is to use invisible digital watermarking scheme, while chaotic cipher has great superiority over the traditional cryptography of image information. Chaos, as a kind of nonlinear phenomenon, has many remarkable characteristics, such as pseudo-random, unpredictability of evolution of its orbits, properties of mixing and sensitivity to initial conditions and system parameters. These characteristicses are in accordance with the requirements of cryptography. Research shows that there are some relation between traditonal cipher and chaos. The main research contents and originality of this paper can be summarized as following:1.Research on the theory of chaos and its application to image security.In this paper, it is made clear that what features of chaotic phenomenon are the basic and what features are the measurement features. The chaotic maps of 1D, 2D and 3D applied to image security, and their charactoristicses are studied deeply, and the objective requirements, which the image security demands from the chaotic system, are also discussed. All the fruits provide theoretical grounds of argument for the design, selection and judgement of chaotic system used for image information security.2.The chaos-based cryptography employed in the identity mark encryption is developed.Aiming at solving the problem of identity mark encryption used in image protection, the author develops a chaos-based Hash function. For the purpose of converting the recognizable plain text to recognizable cipher text defined in a special character set, a many-to-one cipher map is further more dessigned based on sorting and the previous Hash function. Due to the requirement that the plain text needs to be transformed into certificate with definite length in the process of common encryption, a certificate construction function is presented, which is self-correlated and sensitively depends on the plain text and cipher text, and by which the generated certificate is secure and unbreakable. Experimental results show that the cipher text generated by any of the three functions is unique and definite, but the encryption process shows...