Image Encryption Algorithm Based On Chaotic System And DNA Sequence

With the rapid development and popularization of network and multimedia technology,a large amount of digital information is transmitted and shared through the network.Due to the openness and complexity of the network environment,information security is seriously threatened.The image's vividness and simplicity make it an important means of information transmission.Whether in military,commercial,medical or life,images have an irreplaceable importance and are widely used.Therefore,how to ensure that image information is not stolen by attackers is of great significance.Image encryption is one of the important ways to ensure the security of image information.Traditional encryption methods(such as AES,DES)are not suitable for image encryption,because image information has a high degree of redundancy between adjacent pixels,a large amount of data,and low encryption efficiency.Chaotic systems are highly sensitive to initial and parameter values,as well as their unpredictability.At the same time,the high parallelism of DNA calculations,mass storage,and ultra-low power consumption make them very suitable for image encryption.However,many existing encryption algorithms have problems such as sensitivity to plaintext and inability to resist noise attacks.Therefore,this thesis conducts the following research:Firstly,aiming at the problem that some current image encryption algorithms cannot resist selected plaintext attacks,a new block image encryption algorithm based on chaotic mapping and DNA dynamic encoding and operation is proposed.The first is to divide the image into rows and encode the image using DNA dynamic coding rules.The global scrambling process is performed at the DNA level,and the initial value of chaos is changed according to the constant number of DNA bases before and after scrambling,thereby increasing the ability to resist the choice of plaintext attacks,while the decryption end can automatically retrieve.After scrambling,the extended Hamming distance of the image is used to generate a row of random numbers as the initial ciphertext value of the diffusion operation.The sequence will be discarded after participating in the diffusion,so the decryption end does not need to generate the sequence,which improves the security of the algorithm without increasing the generality of the algorithm.The diffusion process is divided into pixel-level and DNA-level diffusion,so that the diffusion of one pixel value can quickly affect the entire image,increasing the security of the algorithm.Experimental results simulation and theoretical analysis show that the algorithm can resist various typical attacks,has high security and is easy to implement.Secondly,an image encryption algorithm based on the combination of genetic algorithm and dynamic encoding and decoding of DNA was studied.The use of genetic algorithms allows the algorithm to achieve more ideal information entropy and lower correlation between neighboring pixels.First,the image is encrypted in blocks using dynamic encoding and operations of DNA to generate an initial population,and each individual's key is related to the plaintext,thereby improving the algorithm's ability to resist plaintext attacks.Secondly,combined with the selection and crossover operation of the genetic algorithm,the optimal solution is selected to obtain the ciphertext image with the best encryption effect.Simulation experiments show that the algorithm has high security.To sum up,this thesis studies two image encryption algorithms.According to simulation verification and theoretical analysis,the algorithm can effectively resist the selection of plaintext attacks.It has high information entropy,ultra-low correlation coefficient values of adjacent pixels,and large Key space,high key sensitivity,can resist noise attacks,can be easily implemented in parallel operations,etc.Therefore,the algorithm has great theoretical value and application prospect.