Research On Image Encryption Based On LDPC Code And Chaos

Information digitization and high-speed development of Internet technology not only bring us convenient and colorful way of life communication,but also bring us more and more information security problems.Digital image encryption technology has also become a more and more important frontier in the field of information security,with great potential and research application value.In this thesis,LDPC(low density parity check)is used to solve the problems of one-dimensional single chaos image encryption algorithm,such as simple structure,small key space,low anti decipher strength,and the invisibility and robustness of traditional information hiding technology Code)has the characteristics of simple decoding,wide range of applicable channels,strong anti-interference ability,extremely sensitive initial value of chaotic system,good random characteristics,etc.an improved encryption algorithm based on LDPC code and dual Logistic chaotic system is proposed,which can expand the key space,reduce the bit error rate,enhance the security and anti-interference ability of the system.The main research contents of this thesis are as follows:First of all,the improved algorithm is studied and divided into two parts.The first part is to process the watermark information,that is,to generate a random sequence through two logistic maps and to implement value substitution encryption for the original watermark.Then,LDPC code is used for encoding and BPSK modulation to obtain the encoded watermark sequence,and the processed watermark information will be embedded in the original carrier image for copyright protection.The second part is to process the carrier image,that is,to layer RGB of the carrier image,and to realize the double encryption of the carrier image by using the double chaos system to process and recombine layer by layer.In the actual image transmission application,if the encryption of the carrier image is cracked or stolen illegally,the watermark can still be extracted for copyright protection,which is the same as double insurance of the carrier image.Then,through MATLAB simulation,the improved algorithm is compared with the single chaos encryption algorithm and the traditional watermarking algorithm in histogram,correlation between adjacent pixels,key space and rate,embedding capacity,anti differential attack test and other aspects,which shows that the improved algorithm can enhance stability,anti-interference and security,and well balance the problem of robustness and watermark invisibility Question.Finally,a digital image encryption integrated test system based on FPGA programmable logic resources and Nios II soft core is designed,including the overall design of hardware / software,Nios II soft core design,VGA module design,etc.the algorithm is applied to practice,and the test results are displayed by VGA to verify the feasibility,reliability and practicability of the algorithm.The simulation and hardware experiment results show that the improved algorithm has a good application value for the confidentiality and copyright protection of digital image information.