Research On Digital Image Encryption Algorithm Based On One-Dimensional Compound Chaotic Map

With the rapid development of communication and computer network technology, the security of information transmission is a concern. Encryption is an effective way to ensure the security of information transmission. As the image itself is featured with huge amount of data, strong data correlation and high redundancy, and the traditional encryption method is not suitable for image encryption, therefore a new way is needed to solve the problem. The birth and development of chaos theory has brought hope to the research of image encryption. The high sensitivity to initial conditions, the ergodicity and pseudorandomness are typical characteristics of the chaotic phenomenon, which are consistent with the basic requirements of the cryptography: confusion and diffusion. So since chaos theory was introduced into image encryption in the 1990’s, chaotic image encryption has got the booming development.Chaotic systems used in the image encryption are classified into continuous and discrete ones, as well high and low dimensional ones. Compared with high dimensional chaotic system, one-dimensional discrete chaotic map has some inherent defects, but it has the advantages, such as simple structures,easy implementation by hardware and software and the fast running. Thus the research of one-dimensional chaotic map and its application has important value and broad realistic significance. Based on one-dimensional chaotic map implementation and improvement, and aiming at its application in the field of image encryption, the implementation and improvement of the existing one-dimensional chaotic map are made and some improved methods of chaotic image encryption are put forward in this paper. The main works of the dissertation are as follows:1. Chaotic pulse sequence generator based on the tent map.In view of the difficulty of paprameter adjustment and the need of external control signal in the existing chaotic pulse sequence generation circuits, a chaotic sequence generator is constructed based on the voltage pattern implementation of the tent map. The circuit with fewer electronic components can be used to realize the function of tent map, and the time interval of pulse sequence can be controlled by changing the variable electronic components in the circuit. The tent map and pulse time interval map generated in the circuit are used in image encryption. The simulation results demonstrate the feasibility and effectiveness of one-dimensional chaotic map in image encryption.2. Image encryption algorithm based on 1DSPCM and two-level total permutation.According to the hybrid mode with series-connection then parallel-connection of three simple one-dimensional maps, a class of one-dimensional compound chaotic system 1DSPCM is designed. A kind of one-dimensional chaotic map is produced through choosing the tent map, Logistic mapping and sine map as seeds. On the basis of the compound map, image encryption algorithm based on the two-level total permutation is proposed. In consideration of performance and efficiency, the strategy of two-level confusion with bit level and pixel level is adopted in the process of confusion. First the most significant bit of each pixel in bit plane is selected, and the total permutation is made in the sequence composed of them. Then the second total permutation is operated on all the pixels of the image. In order to resist the chosen plain attack, the diffusion keys dependent on plain image are adopted in the process of diffusion. In terms of security and efficiency, the algorithm has made a good compromise.3. Image encryption algorithm based on Fibonacci-Lucas transform and bidirectional diffusion.According to the hybrid mode with series-connection then parallel-connection of three simple one-dimensional maps, one-dimensional compound chaotic system 1DPSCM is designed. In view of the same operation mode in each round of the existing confusion, the transformation set formed by Fibonacci-Lucas transform is used to achieve the image confusion. The transformation kernel of each round in confusion is determined according to chaotic map, which can avoid the attack on the encryption algorithm due to the periodicity of transformation. In the diffusion phase, bidirectional diffusion strategy is adopted. When obtaining the equal NPCR and UACI, the bifirectional diffusion structure is featured with the shorter time. The proposed method has large key space and can be used to effectively resist differential attack, statistical attack, chosen plaintext attack, noise attack and cropping attack, at the same time, shorten the computing time.4. Joint image compression and encryption algorithm based on one-dimensional compound chaotic map and compressed sensing.Through the reasonable choice of three chaos maps in 1DPSCM, a novel one-dimensional compound chaotic map with a large key space and comparatively uniform distribution has been achieved. Joint image compression and encryption algorithm is introduced on the basis of compressed sensing. The circulant matrix constructed by the chaotic map serves as the measure matrix in the CS. Fibonacci-Lucas transform can be adopted to carry out the confusion operation on the measurement image and transformation kernel in each round is determined by chaotic maps. Meanwhile, in order to resist differential attack, the linear scaling is applied to finish the diffusion operation. Experimental simulation results demonstrate the feasibility of one-dimensional compound chaotic map in a joint of image compression encryption. In addition, the proposed algorithm has the large key space and shows excellent ablity of resistance of differential attack and robustness against data loss to some extent.