Research On Digital Image Encryption Based On Hyperchaos And Radon Transform

With the rapid development of computer network and communication media,people's communication mode is changing.More and more digital information such as image,video and voice are transmitted through the network.Because the information expressed by digital image is very rich and the content is intuitive,it has become an important means to express information in multimedia,and has become the main way of communication.Therefore,the problem of information confidentiality is emerging.If not protected,it will lead to the leakage of personal information and even state secrets.At this time,image information needs to be protected,that is,image encryption.To solve the problem that the key space of traditional encryption method is small and easy to be cracked,it is very important to use chaotic system with large key space and high security for image encryption.At present,hyperchaos with more complex dynamic characteristics and high sensitivity of system control parameters and initial key gradually enter people's field of vision.Therefore,the application of hyperchaos system in encrypting digital image can not only enhance the image encryption effect,but also increase the key space,improve the encryption security and anti attack.On the basis of chaos theory,this paper gives full play to the advantages of hyperchaos system,designs two digital image encryption algorithms based on hyperchaos system,and introduces Radon transform,Hilbert curve and image bit plane to realize encryption,and verifies the security of the two algorithms through experimental simulation.The first encryption algorithm is based on Hilbert curve scrambling and hyperchaotic system.In this scheme,the space filling characteristic of Hilbert curve and the projection spectrum characteristic of Radon transform are used,and it is combined with hyperchaos system with strong pseudo-random and high initial value sensitivity.In the scrambling stage,Hilbert curve is used to realize the local scrambling of pixel value,and hyperchaotic system sequence is used to realize the global scrambling of pixel value,which makes the distribution law of pixel position disturbed.In the diffusion stage,the hyperchaos sequence is used to realize the forward diffusion and the reverse diffusion of the pixel value,which can fully change the size of the pixel value.Finally,the ciphertext image is output by bitwise exclusive or operation with chaotic sequence.After experimental simulation,through correlation,histogram,information entropy,differential analysis and other security analysis,we can see that the encrypted image has strong anti attack and high security.The second encryption algorithm is based on Radon transform and hyperchaotic Rossler system.In this scheme,the pixel value of the plaintext image is selected as the initial value of the Kawakami hyperchaotic system.The initial value of the hyperchaotic Rossler system is determined by the pixel value of the plaintext image and the chaotic sequence value generated by the Kawakami hyperchaotic system,which enhances the dependence of the hyperchaotic system on the plaintext image.The security of the key can be effectively improved.In the process of scrambling,two sets of chaotic sequences generated by the hyperchaotic Rossler system are set as two images of the same size as the plaintext image,which are bitplane decomposed and combined with the plaintext image,and then the image is encrypted by Radon transform;In the diffusion process,the remaining two chaotic sequences of the hyperchaotic Rossler system are bitwise XOR and the sequence after sequential shift of the scrambled image are bitwise XOR;finally,the three images are regarded as the red,green and blue components of the color image,then the three channels are combined,and finally the color image is output as the ciphertext image.Through the test of security performance,the encryption algorithm has strong key sensitivity,better ability to resist differential attack,and higher security of encrypted image.