Research Of Image Encryption And Secure Sharing Based On Optical Chaos

In recent years,digital information is growing and developing rapidly,and is widely used in all fields of society.Because digital color images have special color,texture and shape characteristics,it has become one of most important information expression items in digital multimedia information,and has wide applications in politics,economy,education and so on.However,in some special fields,such as military,commercial and medical treatment,as an important carrier of rapid interaction of information,digital images need greater security.Therefore,how to ensure the security of digital image has attracted people's attention.Meanwhile,image encryption is the common technology to solve image security problem.In fact,some good characteristics of chaos,such as the ergodicity of chaos,the sensitive dependence on initial conditions and parameters,and the complex dynamic behavior,make it have natural advantages in the research of image encryption.However,compared to the traditional chaotic electrical,optical chaos generated by semiconductor lasers(such as vertical cavity surface emitting laser(VCSEL))has more advantages,such as high bandwidth,high randomness,and communication system with good compatibility,these advantages make optical chaos have great application foreground in image encryption.Meanwhile,with the rapid development of cloud computing technology,some advantages of the cloud memory,for example,large-scale virtualization,low cost and convenient sharing ability,make it has a wide range of applications in the field of medicine,industrial areas,commercial areas,academic field and national military and other fields.Thus,multimedia information can achieve convenient information exchange by cloud memory,especially the interaction of image informations.Therefore,based on optical chaos generated by VCSELs,this thesis propose a color image encryption algorithm,and implement secure sharing of encrypted images on cloud memory.The main contents are as follows:Firstly,based on two coupled VCSELs,this thesis builds a system of optical chaos generation and secure communication.In the proposed system,under proper external disturbance situations,the two VCSELs can achieve chaos synchronization by adjusting injection strengths and injection time,and output the optical signal in chaotic state which can be exploited to produce the key of image encryption and decryption and achieve its secure transmission.In addition,based on some parameters,including time series,power spectrum,phase diagram,correlation function,Q factor,bit error rate(BER),eye diagram,the thesis makes simulation analysis about nonlinear characteristic,synchronization and communication characteristic of the two VCSELs.Secondly,based on resource sharing of cloud memory,an image encryption and security sharing system is proposed in this thesis.In this system,the thesis uses optical chaos generated by the above chaotic communication system and the user's key to generate the key space of image encryption and decryption,then transmit it safely through the chaotic secure communication system,so as to ensure the security of encryption and decryption key space.At the same time,before image encryption,due to image identification and authentication,this thesis introduces an watermarking technology based on discrete wavelet transform(DWT).then.Lastly,the thesis exploits the Joseph mapping and Logistic mapping to encrypt color image,and analyzes the performance of image watermarking and encryption by some common parameters,including mean square error(MSE),peak signalto-noise ratio(PSNR),information entropy,histogram,cross-correlation,pixel change rate(NPCR)and the average change intensity(UACI).The research of this thesis is constructive and meaningful for application of optical chaos in image encryption and security sharing.