The Generation And Application Of True Random Number In Digital Image Encryption

In recent years, Random number is more and more widely applied in the field of information security, especially in network security. It has became more important. Therefore the researchers put forward strict requirements on the properties of random number. The random number with high quality will be widely used in the near future. Because of true random number has better randomness compared with the pseudo-random number, such as excellent independence, uniform distribution, irrefragable, etc., so the study of it become more and more important and urgent. Various design methods of true random number generator which put forward by many colleges and research institutions have promoted the development of true random number with high quality in more different fields.This article analyzes generation principle of the true random number in the first two chapters, and introduces the current research status of true random number generator. The third chapter takes research on the hardware platform of true random number generator, and puts forward a realization method of true random number generator based on Xilinx Spartan3XC3S400platform.The sequences produced by TRNG with post-processing module can pass the NIST test. The true random number generator consists of common logic unites only, it can be quickly transplanted into ASIC design and shorten the development cycle. The fourth chapter puts forward an encryption algorithm which yields XOR on digital image pixel sequence. This algorithm does image block scrambling based on Arnold transformation on the original picture before encryption. The receiver can get the original picture by doing XOR decryption and Arnold transformation. The encryption process of this algorithm is easy, what’s more, image scrambling improves the confidentiality. Experiments proved that correlation among the pixels of the encrypted picture according to this algorithm is small, and this algorithm does well against scaling attack and has good anti-noise property.The research effort can be divided into the following sections:1. Analysing the conditions and methods of producing random numbers-pseudo random number and true random number. Describe the mature structure and generating principle of true random number generator based on hardware platform. Put forward a new kind of design of true random number generator, taking the output of metastable-trigger as random source.(1) Studying and researching the design method and flow of the programmable logic devices, design RS flip-flop with Verilog-HDL language, adjust the timing to make a trigger under metastable, the above two operations have provided an entropy of the true random number generator, take xor operation for the outputs of multi-triggers to preliminary improve randomness of the final sequence.(2) Adding post-processing module to enhance the quality of the random sequences and to increase entropy per bit, the module adopts the structure of xor’ing the level4xor-chain with little m-sequence generator, simple to structure, easy to implement.2. Testing the randomness of true random number by the testing-software and standards provided by NIST(national institute of standards and technology), carry on the performance testing with15randomness indicators for each group of10M-bit sequence.3. Proposing an encryption method of digital image based on the true random number, xor the true random number with the pixel sequence of gray image to complete encryption, easy processing end achieving. Proved by experiment, the pixel correlation of encrypted image is much smaller than before, with good anti-shearing and anti-noise performance.