Reserach On Multi-image Encryption And Hiding Algorithm

With the rapid development of computer and multimedia technology,the security of information transmission becomes more and more important.As an information carrier,Image is the most important form of information expression in the multimedia information,it overcomes the problems of low efficiency in the process of data transmission,therefore,it is widely used in many fields.Since some image transmission involve national security and personal privacy,images need to be transmitted in an encrypted way.Therefore image encryption technology has important practical significance.At present,the researchers use optical information processing systems to encrypt images in various ways such as phases,amplitudes,wavelengths,etc.,and the encrypted image has the property of high parallel and high-speed processing capabilities,which makes the image encryption favored by researchers at home and abroad in the field of optical information processing.Since the phase recovery algorithm is applied in optical image encryption technology,it has developed rapidly and has become an effective method of image encryption,which has received great attention from researchers.In addition,in order to make the image has real-time conditions in the process of transmission.In recent years,multi-image encryption algorithm has become the focus of attention.The key issue of multiple image encryption algorithm for researchers is to ensure its capacity of parallel transmission and high efficiency of encrytion and to ensure there is no cross interference phenomenon in the process of decrypting the image.The phase recovery algorithm of image encryption is one of the current mainstream algorithms.Through the use of computer technology,it is faster and easier to use iterations in the phase recovery algorithm.Therefore,there will be more space for extended research on the basis of phase recovery algorithm.Based on the current trend of multi-image encryption,this thesis uses phase recovery algorithm theory combined with some new algorithms to develop work and research.The main work of this thesis is divided into the following parts:(1)The thesis introduces the background,importance and research status of multi-image encryption algorithm and further illustrates double random phase encryption system basic theory,basic theory of optical image encryption based on interference and GS phase recovery algorithm encryption principle,and describes advantages and disadvantages of this encryption algorithm,their promotion algorithm.(2)Based on the phase recovery algorithm,an encryption scheme is proposed.By using Fractional Fourier GS iterative algorithm of image encryption,multiple images are successfully encrypted into a single image;on this basis,the introduction of the Fourier phase truncation image encryption algorithm further enhanced the security of the system by generating two phase functions in the encryption process as private keys for decryption.(3)After successfully encrypting multiple images into a single image,this thesis proposes a fractional Fourier interference image encryption,digital watermark image,the combination of chaotic image encryption single image encryption scheme.Firstly,the information of image to be encrypted can be encoded into two phase-only masks(POMS)for initial encryption by fractional Fourier interference.Secondly,using the wavelet digital watermarking theory,the phase masks as a watermark are embedded in the host images for re-encryption.Finally,the encrypted host images were performed pixel replacement operation to complete the entire encryption process by chaotic sequence.The encryption scheme in this thesis can hide the two POMS obtained by encoding,illegal user can not obtain the original image silhouette information by using one or two POMS.The encryption process is simple,high efficient.The last two encryption is random,which further improve the security and robustness of the entire encryption system.The simulation results show that the method is feasible and the decrypted image has high quality and security.