Research On The Key Technologies Of Image Encryption Based On FPGA

With the wide application of multimedia technology, image is used as an important loading form of multimedia information which is actual, intuitive and can be interpreted, etc., so it has been increasingly used in education, health, railways, civil aviation, social, military and other fields. However, when people communicate with each other by image information, image itself will carry the information concerned by both sides, meanwhile, there will be a large number of environmental information and private information, such as: personal biometric information in medical image, implicit geographic characteristics in military images and so on. So the information system used for image interaction should not only exchange information easily, but also attach great importance to safety when image information is in transmission process, and finally resist being stolen and doctored by any attacks.Unlike the texts, sounds and other finite symbol set information, image information has strong real-time interactivity and huge data amount characteristics in actual applications which requires that the interactive information system carrying image must have a high-speed information system throughput and efficient information encryption and decryption capabilities. How to achieve these objectives, many researchers suggest that the way to design and use high-speed, parallel dedicated hardware for image information conversion is an effective way to realize wide applications of image.FPGA can meet the needs of high-speed image encryption system with its parallelism of internal circuitry, integrated PLL efficiency, customized pin functions, as well as its ease of maintenance, flexibility in upgrading and scalability. Due to the flexibility of FPGA, flexible designs can be achieved according to special application requirements, and then the restrictions on specialized chips can be reduced. The internal procedures in FPGA can be carried out in parallel way with simultaneous execution of multiple tasks, improve efficiency and reduce latency, meanwhile, there are a large number of IP cores in FPGA, which can meet with the requirements of image encryption approaches and flexibility of application requirements.In this paper, the image encryption algorithms based on SMS4 block cipher, ZUC stream cipher and composite chaos are proposed, then image encryption system is designed and developed by using the algorithms above. The main contents and innovations are shown as follows:According to the feature of large amount of image data and FPGA parallel processing, image encryption algorithm based on SMS4 block cipher is proposed, internal FPGA-based pipeline structure is designed and optimized which can improve the throughput of encryption algorithm. In order to enhance the security of image encryption, FPGA-based rapid scrambling address conversion method is proposed according to the characteristics of SMS4 block cipher which can simplify the circuit structure and improve the efficiency of image replacement. In order to meet the needs of image encryption system, functional modules are designed and developed based on SMS4 block cipher image encryption algorithm.Due to simple hardware circuit of stream cipher and its easy implement, image encryption algorithm based on ZUC stream cipher is proposed, which can take up less FPGA resources and complete the encryption and decryption functions of images. In order to improve the security and resist differential attacks of the encrypted image, suitable FPGA password link mode and improved image replacement Baker scrambling algorithm are put forward, then image encryption module based on ZUC stream cipher is proposed.Encryption strength for conventional encryption algorithm depends on fix circuit architecture. Image encryption algorithm based on compound Logistic chaotic system is proposed with the large amount of information, redundancy and strong correlation between pixels of image information and sensitivity to initial conditions and pseudo-randomness of chaotic system, then Lyapunov exponents of compound chaotic equations are analyzed. The encryption strength of composite chaotic system will change as the correlation of pixels change, and achieve better image encryption effect. Chaotic image encryption system based on FPGA is designed and developed according to composite chaotic image encryption algorithm, in order to improve the complexity of the chaotic system, 128-bit multiplier is used for the design.Here, image encryption systems based on FPGA and embedded platform are designed by using the image encryption algorithms above. Embedded development platform is based on ARM processor, then SMS4 block cipher encryption algorithm and ZUC stream cipher image encryption algorithms are used. FPGA-based development platform and the three image encryption algorithms above are used here, PCIe bus interface is used for data communication with the computer by DMA technology, which can complete data exchange between computer memory and internal memory of FPGA, FPGA is responsible for the encryption and decryption of the image and the control of the entire system, then the efficiency of the system is improved.