Research On Digital Image Encryption Based On Chaotic System And DNA In Cloud Storage Environment

With the development of computer network and multimedia technology,the amount of multimedia data presents an explosive growth.However,due to the openness of the cloud platform,the digital images are vulnerable to attacks by means of monitoring,stealing,interception,tampering and forgery.Therefore,the security of digital image in the cloud transmission and storage process is extremely important.The fundamental measure to protect digital image is to encrypt the information.At present,how to ensure the security of digital image in the cloud platform has become an important research topic in the field of cryptography.Chaotic system is a kind of deterministic system which is highly sensitive to the initial value and control parameters,and the generated chaotic sequence shows pseudo randomness.The internal randomness,the sensitivity of initial value and parameter,and the good ergodicity of chaotic system are naturally related to cryptography.DNA(Deoxyribonucleic Acid)sequence has huge data storage and computing power,which can be combined with chaos system to improve encryption efficiency and security.In this paper,we focus on image security protection in cloud storage environment.Two digital image encryption algorithms are proposed based on chaotic system and DNA computing,and the performance of the algorithm is analyzed from two aspects of availability and security.The main work and research contents are as follows:(1)A color image encryption scheme based on NCA(New Nonlinear Chaotic Algorithm)coupled map lattice and a four-wings hyperchaotic system was proposed.Firstly,the initial values of CML system and hyperchaotic system are updated by using SHA-256 hash function and color plaintext image.The keystreams are generated by iterating the chaos system.Then,the red,green and blue color components of the image are scrambled according to the index in the keystreams,and the components are evenly divided into sub-blocks of the same size.Next,according to the keystreams,the sub blocks of DNA sequence are obtained by DNA encoding and multi-round diffusion.Finally,according to the rules of DNA decoding,the sub blocks are decoded to obtain the encrypted image.Experimental results and security analysis show that the algorithm has good encryption effect,high speed,high security,and can resist noise attack and cropping attack.(2)A multi-image encryption algorithm based on DNA sequence and four-dimensional Chen hyperchaotic system was proposed.Firstly,the hash values of four images are combined with the initial key to generate the initial values and parameters of the four-dimensional Chen hyperchaotic system,and then the keystream are generated by substituting them into the chaotic system.Then,the bit-planes of all the images are superposed into a three-dimensional matrix,and the matrix is scrambled.Next,the scrambled three-dimensional matrix is transformed into two-dimensional matrix and divided into four matrices of the same size.Then,we use the pseudo-random sequence in the keystream to do DNA dynamic encoding and DNA operation on the matrix.Finally,a group of encrypted images are obtained by dynamic decoding.Simulation results and security analysis show that the designed multi-image encryption algorithm encrypts four gray-scale images at one time,which has good encryption efficiency and security.(3)Based on the image encryption algorithms and the Matlab were used to design and develop a digital image encryption and storage platform in the cloud environment.The platform realizes digital image encryption,decryption,storage and other functions in the form of graphical interaction,so that users can easily and intuitively use the platform to encrypt and decrypt images.