Application Research Of Optical Processing Technology In Multiple-image Encryption Algorithm

With the development of computer technology,images are widely used in people's study,work and life with their intuitive and vivid features.However,as an important carrier of information in the process of storage and transmission,images are facing increasingly serious security problems.In recent years,due to its multi-dimensional,high robustness,multi-parameter control capability and high-speed parallel processing capability,optical information technology has been applied in the filed of image encryption by the researchers at home and abroad.In this thesis,three multiple-image encryption algorithms have been proposed according to application research of optical information processing technology in the multiple-image encryption schemes.The main work is summarized as follows:First,a multiple-image encryption algorithm based on cascaded free-space wave propagation transform has been proposed.Initially,each plaintext image is encoded into the corresponding phase mask with the help of a structured phase mask by using the phase retrieval process.Then,all generated phase mask images are integrated into the ciphertext using phase mask multiplexing techniques.At the same time,the corresponding decryption key of each plain image is generated.The encrypted capacity can be expanded considerably,and the affection of cross-talk noise can be avoided to some degree.Meanwhile,the number of phase mask keys considered as secret keys is reduced greatly.The simulation results verify the feasibility and security of the proposed method.Second,a multiple-image encryption algorithm based on cascaded fractional Fourier transform has been proposed.In order to enhance the security,two layers are used in the encryption process of multiple images.In the first layer,a series of plaintext images are encoded into an amplitude distribution using the cascaded fractional Fourier transform,referred to as an intermediate image.In the second layer,the intermediate image is encrypted into two noisy ciphertext images using the interference method.The inherent silhouette problem existed in the interference-based encryption methods can be Eliminated.The hierarchical decryption process is implemented,where the user with high authority has more security keys and accesses more decrypted information.Simulation results demonstrate the effectiveness of the proposed method and the robustness against various attacks.Third,a novel double-image encryption method has been proposed based on optical interference and logistic map.Initially,the original images are rearranged into two scrambled components using a random sequence generated with logical map.One component is used as the input image to the framework of double random phase encoding,and then encrypted into the ciphertext.Another component is decomposed into two phase masks,which are placed in the input plane and the transform plane of double random phase encoding,respectively.Parameters such as wavelength,axial distance,and conditions of logical map can be considered additional keys,which can further increase the level of security.Most importantly,the annoying silhouette problem existed in the interference-based encryption methods can be effectively avoided.The effectiveness and feasibility of the proposed algorithm are proved with a set of simulations.