Image Encryption In Chaotic System And Transform Domain

In recent years,the use of multimedia tools to transmit information on the public network has become more and more popular,with the emergence of a variety of ways of information transmission,which has brought great convenience to today’s life.Image information is widely used in politics,military affairs,medicine and people’s daily life because of its visual and intuitive characteristics among various information transmission methods.The security issue of how to protect the image information from being stolen and destroyed by malicious attacks in the process of image transmission is also more worthy of our attention.Therefore,the research on image encryption has become the focus and hot spots of current research.Nowadays,with the increasing requirements for information transmission efficiency in various fields,the efficiency of encrypted transmission of a single image can no longer meet the needs of people.Therefore,many scholars began to study the encryption of multi-image.This paper proposes two image encryption algorithms based on the Fractional Fourier transform domain and the wavelet transform domain,and conducts simulation experiments on the two methods.Verify the feasibility of its implementation.The research work of this paper are as follows:First of all,a multi-chaotic Arnold image encryption method based on fractional Fourier transform is proposed.In this algorithm,firstly,using the fractional Fourier transform to convert the image from the spatial domain to the frequency domain as the initial transformation.Then the improved Arnold transform is used to realize the scrambling encryption of the image.The improvement process of Arnold transformation is as follows: Using hyperchaotic Lorenz and one-dimensional chaotic system Logistic to generate random sequence to generate Arnold transform transformation matrix parameters.Among them,the hyperchaotic Lorenz system has four initial values,and the image selected in this paper can be regarded as composed of eight different bit planes,and each initial value of the chaotic system can be determined by two different bit planes.One-dimensional chaotic system logistic has an initial value,which can be determined by the sum of all pixels in the image.Finally,the second fractional Fourier transform is performed on the scrambled image to complete the image encryption operation.Experiments prove that the algorithm has good encryption effect and can effectively resist various attacks.Secondly,this paper proposes a multi-image encryption based on integer lifting wavelet transform and DNA encoding.In this algorithm,firstly,the integer lifting wavelet transform is performed on multiple images to extract their low-frequency components and recombined in a new image.Then the image is cyclically shifted using the three-dimensional logistic chaotic system to realize the scrambling and encryption of the image.In order to change the pixel value of the image,using the hyperchaotic lorenz system to diffuse the image forward and backward.Then use dynamic DNA coding to achieve the second diffusion of the image.The specific process of DNA encryption is as fllows: Firstly,preprocess the introduced chaotic system to generate a chaotic matrix is the same size as the encryption images.Then the encryption image and the matrix generated by chaos are uniformly partitioned and dynamic DNA coding.And performing DNA addition,subtraction,XOR and XNOR operations between the image and the chaotic matrix.Finally,DNA decryption can complete the encryption of the image.Among them,four sets of random chaotic sequences are generated by a four-dimensional hyperchaotic system to control the encoding method of the image,the encoding method of the chaotic matrix,the operation method of the image and the chaotic matrix,and the final decoding method respectively.Aiming at the problem that there are many key parameters in the encryption system and it is easy to leak during the propagation process.So we propose to use the RSA of asymmetric algorithm to encrypt the key,which improves the security of the encryption system.The simulation experiments show that this algorithm has the characteristics of a large number of encrypted images,good quality of restored images and can effectively resist various attacks.