Application Research On Image Encryption And Watermarking Based On Optical Information Transform Technology

With the rapid development of information technology,multimedia has become an important way of information communication due to its features such as comprehensiveness,interactivity and intuition.But the security problems in the transmission process are becoming more and more serious.As an effective carrier of information,images are also faced with the problems of illegal theft,listening and spreading maliciously.So,how to encrypt images efficiently has become a hot issue in the field of information security.In recent years,because the optical information transformation technology has many advantages,such as large capacity,high dimensionality,high degree of freedom,high robustness,suitable for parallel data processing and high-speed computing,and multi-parameter control ability,it has been applied in the field of image information security.According to current research status and shortcomings of optical information transformation technology,the corresponding schemes of image encryption and digital watermarking have been proposed in this paper,and the main works are summarized as follows:First,a novel multiple-image encryption scheme using the nonlinear iterative phase retrieval algorithm in the gyrator transform domain under the illumination of an optical vortex beam has been proposed.With the help of two chaotic phase masks,each plain image is encoded into two phase-only masks using the iterative phase retrieval process in the gyrator domain,which are considered as the private keys.All second keys of plain images are modulated into the ciphertext that has the stationary white noise distribution.Due to the use of the chaotic structured phase masks,the problem of axis alignment in the optical setup can easily be solved.Two private keys are directly relative to the plain image,which makes that the scheme has high resistance against various potential attacks.Simulation results are given to verify the feasibility and robustness of the proposed encryption scheme.Second,a novel optical color image watermarking scheme considering human visual characteristics has been presented in gyrator transform domain.Initially,an appropriate reference image is constructed of significant blocks chosen from the grayscale host image by evaluating visual characteristics.Three components of the color watermark image are compressed based on compressive sensing,and the corresponding results are combined to form the grayscale watermark.The frequency coefficients of the gyrator-transformed grayscale watermark image are fused into the frequency data of the gyrator-transformed reference image.The fused result is inversely transformed and partitioned,and eventually the watermarked image is obtained by mapping the resultant blocks into their original positions.The scheme can reconstruct the watermark with high perceptual quality and has the enhanced security due to high sensitivity of the secret keys.Simulation results have verified the feasibility and the robustness against attacks such as noise and occlusion attack.Third,an optical image watermark scheme using ghost imaging technique has been improved in the gyrator(GT)domain.In this scheme,the watermark algorithm has been implemented under the framework of two-layer configuration.In the first layer,the watermark is encoded into a series of measured intensities by using computational ghost imaging,which is used to form an interim image with the same size of the host image.In the second layer,the GT transform is applied to host image and interim image,respectively.The transformed interim image is embedded into the transformed host image with a weighted factor,and then the watermarked host image can be obtained by using the inverse GT transform.The feasibility,effectiveness and robustness against different attacks of the proposed scheme have been verified with simulation results.