Algorithm Of Color Image Encryption And Its Software Implementation Based On Complex Chaotic Systems

With the rapid development of computer and internet technology, the security of data transmission and storage is increasingly drawing public attention. Image, as a commonly seen types of data storage, has been widely used in different fields. Therefore, how to encrypt images also has become the focus of the study in the field of information security.Color image itself has features of high correlation and high information between adjacent pixels. However, traditional encryption method originally is not specifically designed for image encryption, thereby not taking the characteristics of the image into account, so that when applied to an image it often cannot reach good effects. Fortunately, researchers has found that chaotic system is highly sensitive to initial values and possesses pseudo-random selection characteristics, and that its improved version named hyper-chaotic system, is more prominent when used in these areas. Thus, it is very suitable for being using in image encryption.This thesis based on early studies on the hyper-chaotic system developed two kinds of encryption algorithms exclusively targeting color images, by adopting several classical hyper-chaotic systems such as complex Chen system, complex Lorenz system and so on. These two algorithms have been simulated and verified in the platform of MATLAB, and also been implemented using C# as a practical software.The research results are listed as follows:(1) A novel color image encryption algorithm based on two hyper-chaotic systems.The algorithm is based on complex Chen system and complex Lorenz system, whose combination has made the algorithm have larger key space.In addition, the use of a two-dimensional approach has adjusted and optimized the pixel scrambling link, and finally by using hyper-chaotic system generated the RGB three channels of a pseudo-random sequence mixed image. The main advantage of this algorithm lies in multi-layered mixing and large key space. Experimental results have demonstrated that this algorithm could achieve better encryption effect than traditional one.(2) A new DNA-transformation and complex super-order Lorenz system based color image encryption algorithm.The algorithm employed biological DNA encoding rules, and adopted complex super-order Lorenz system to generate pseudo-random sequence required for encryption, after which it introduced a wavelet function and mixing rules to control the blending. Again, Experimental analysis showed the superiority of the algorithm in term of safety.(3) Implement of a hyper-chaotic based color image encryption software using C language.Due to the insufficient capacity of MATLAB in the realization of a general purpose and practical image encryption software, instead, by utilizing the open-source Microsoft OLSO library and based on two proposed algorithms, a user-oriented hyper-chaotic color image encryption software using C# language was designed.