| Encryption technology is a very important application in the field of information security,while encryption algorithm and its implementation methods are the key of encryption technology.Encryption technology requires not only a superior encryption algorithm,but also a secure and reliable implementation platform.Especially for the digital image information with large amount of datas,it is very important to the platform used to realize the real-time processing of the image data.Based on the study of chaotic system,this paper designed an image encryption algorithm based on a 4D chaotic system.and combineing with the widely used FPGA hardware system to complete the design and implementation of this paper.The widely used hardware system of FPGA was designed to implementate the encryption algorithm.Chaotic systems generally have highly complex dynamic characteristics and are very suitable for the design of encryption systems.FPGA(Field Programmable Gate Array)is a high integrated circuit which can be programmed repeatedly.It has abundant hardware resources and is helpful to improve the operation speed of encryption algorithm and the real-time processing of datas.Based on the study of a four-dimensional chaotic system,this paper designed an encryption algorithm which is consist of the chaotic system and the improved generalized Arnold map,and designed a FPGA hardware encryption system to complete the hardware implementation of the encryption algorithm.The main work of this thesis is as follows:(1)In this paper,a four-dimensional chaotic system which is a four-wing autonomous system was chosen as the subject investigated,and it was also the core of the encryption algorithm designed in this paper.In the third part of the paper,the characteristics of the chaotic system were analyzed in detail.(2)Image encryption algorithm is the core of this paper.In this paper,the improved generalized Arnold map and a four-dimensional chaotic system were used to design the encryption algorithm.It was done as follows:The improved generalized Arnold map was used to scramble the image and change the position of the image pixels;Then the image pixels size was changed by the XOR operation bettwen chaotic sequence and pixels.In the latter process,the images were divided into four parts,and two ciphertext feedback items were added to the XOR operation to enhance the diffusion effect.(3)According to the designed encryption algorithm,the FPGA code design of the encryption system was completed,mainly including image storage,image scrambling,image diffusion and the VGA displaying of the image.Completing FPGA code simulation and board level debugging.(4)The result of FPGA hardware implementation was analyzed and verified,and the analysis results of encryption algorithm was given.The experimental results show that the digital image encryption algorithm designed in this paper based on a four-dimensional chaotic system has high security and the effect of FPGA hardware implementation is very good. |
