Research On Image Encryption Based On Joint Transform Correlator And Fractional Fourier Transform

With the rapid development of information technology,information security has been aroused extensive attention.How to store and transfer information effectively and safely,has become the focus of researchers.Recently,with the development of optical technology,optical image encryption technology is widely used in military,commercial and medical and other departments,due to its high processing capacity and high parallel ability based on the transmission of information at the same time to encrypt information,greatly improving the efficiency of encryption.As a multidimensional carrier,light has greatly improved the degree of freedom of information encryption,and the encryption technology based on optical technology is gradually developing.This paper mainly studies the double random phase encoding technique,discusses the optical image encryption based on joint transform correlator structure,from Fourier transform domain to the fractional Fourier domain,combined scrambling technology,chaos theory,effective improvement of encryption the algorithm,the main contents are as follows:Image encryption technology based on joint transform correlator and fractional Fourier transform is proposed in this paper.First of all,we introduced the encryption method based on joint transform corelator in Fourier domain.The original image masked with random phase mask and random phase keys are put together in the input plane behind a Fourier lens.With parallel illumination,the ciphertext can be obtained by a CCD detector in the output plane.In decryption system,the key is put at the input plane individually behind a Fourier lens,and put the ciphertext at the focused plane,passed another Fourier lens,we will retrieve the decryped image.In this method,the ciphertext contains not only the cross-correlation,and strength is higher than the autocorrelation times autocorrelation,seriously affecting the image quality.In order to improve the imaging quality of the decoded image,the cross-correlation must be removed.The original image and key resolution is put at the input plane of the encryption system,respectively.We can obtained their autocorrelation after subtraction of nonlinear processing.Second,because of the encryption system can be easily attacked,a method based on the fractional Fourier transform is proposed.The fractional order parameter with its controllableand high sensibility,is a key technology of encryption and decryption.With the image scrambling in our system,greatly improves the security of the encryption system.Lastly,we introduce the chaotic maps and phase encoding method into our system.With the two method,the encryption system can not only improve the safety of the system,but also greatly improves the system's anti-attack capability.Simulation results verify the feasibility,security and reliability of the proposed encryption algorithm.