Research On Image Encryption Algorithm Based On Chaos And DNA Coding

Digital image is an important carrier of multimedia communication which plays an important role in communication,medical treatment and military affairs.As the images may involve national security,commercial interests and personal privacy,the image information needs to be encrypted and protected.Therefore,digital image encryption technology has become an important research topic in related fields.The research of this thesis is mainly aimed at the problems of low security,low robustness,low encryption efficiency and low key sensitivity of existing image encryption algorithms.Image hashing,chaotic system,DNA encryption,bit-plane decomposition and other theories and methods are used to study the key image encryption technologies of grayscale images,color images,and multiple grayscale images.The main research work is as follows:1.In order to improve the security and robustness of the existing gray image encryption algorithm and reduce the potential security of the encryption algorithm against various conventional attacks,a gray image encryption algorithm based on image hash,improved chaotic mapping and DNA coding is proposed.First,the plaintext image is preprocessed.Then the binary hash sequence is generated by the image hash algorithm as the initial key of the encryption algorithm.Finally,the random sequence generated by Chen's chaotic system is used to calculate and encode the clear text image and chaotic sequence and the ciphertext image is obtained.Experimental results show that the algorithm has good security,large key space(10¹²⁵),high key sensitivity and good robustness against various attacks.2.In order to improve the key space of color image encryption algorithm,the sensitivity of plaintext image,the robustness against conventional attacks and the tamper location analysis,a color image encryption algorithm based on image hash,six-dimensional hyperchaos and dynamic DNA coding is proposed.Firstly,the color image is preprocessed and the initial value and control parameters of the chaotic system are generated by the image hash algorithm.Then,the three color channels of color image RGB are transformed.Finally,a six-dimensional hyperchaotic system is used to generate random sequences which can be used for DNA dynamic coding and operation of color images to obtain the ciphertext images.Experimental results show that the algorithm has a sufficiently large key space(10¹⁶¹),strong key sensitivity,better statistical and differential characteristics,and can perform tampering analysis on tampered images.It has good security and strong robustness.3.In order to solve the problems of large data volume,slow transmission rate and low security of digital image in the internet transmission environment,a multi-image encryption algorithm based on image hash,bit plane decomposition and dynamic DNA coding was proposed for gray image.First,multiple images are merged to generate the initial key through the image hash algorithm.Then the image decomposed by bit plane is transformed by chaotic mapping.Finally,the random sequence generated by the four-dimensional hyperchaotic system is used to encode and calculate the dynamic DNA of multiple images to generate the ciphertext image.Experimental results show that the algorithm has a large key space(10¹⁴¹),high transmission efficiency and security,and can resist conventional attacks such as statistical analysis,differential attack,exhaustive attack,cropping and noise attack.