Research On Optical Information Security Technique Based On Compressive Two-Step Phase-Shifting Interferometry And Computational Ghost Imaging

Optical information security technique relies on the properties of diffraction,interference and polarization of physical optics.By purposefully modulating the distribution of information such as the amplitude,phase or polarization of the optical field,it can encrypt the plaintext image.It has the advantages of high-speed encoding and multi-encrypted dimension.It is a beneficial complement to modern cryptography and an integral part of it.Based on the existing optical cryptography foundation,such as double random phase coding theory,two-step phase-shifting interference theory,computational ghost imaging theory and so on,with combining with compressive sensing technique,hierarchical identity authentication technique,cascaded interference technique,singular value decomposition technique and so on,this thesis proposes a series of new meaningful optical image encryption schemes:(1)A two-level image authentication method is proposed;the method is based on two-step phase-shifting interferometry,dou'ble random phase encoding,and compressive sensing theory,by which the certification image can be encoded into two interferograms.Through discrete wavelet transform(DWT),sparseness processing,Arnold transform,and data compression,two compressed signals can be generated and delivered to two different participants of the authentication system.Only the participant who possesses the first compressed signal attempts to pass the low-level authentication.The application of Orthogonal Match Pursuit algorithm,inverse Arnold transform,inverse DWT,two-step phase-shifting wavefront reconstruction,and inverse Fresnel transform can result in the output of a remarkable peak in the central location of the nonlinear correlation coefficient distributions between the recovered image and the standard certification image.Then,another participant with the second compressed signal is authorized to carry out the high-level authentication.Therefore,both compressed signals are collected to reconstruct the original meaningful certification image with a high correlation coefficient.(2)A multiple-image encryption method based on two-step phase-shifting interferometry(PSI)and spatial multiplexing of a smooth compressed signal is proposed.In the encryption process,with the help of four index matrices storing original pixel positions,all the pixels of four secret images are firstly reordered in an ascending order;then,the four reordered images are transformed by five-order Haar wavelet transform and performed sparseness operation.After Arnold transform and pixels sampling operation,one combined image can be grouped with the aid of compressive sensing and spatial multiplexing techniques.Finally,put the combined image at the input plane of the PSI encryption scheme,only two interferograms ciphertexts can be obtained.During the decryption,with all the secret key groups and index matrices keys,all the original secret images can be successfully decrypted by a wave-front retrieval algorithm of two-step PSI,spatial de-multiplexing,inverse Arnold transform,inverse DWT,and pixels reordering operation.(3)A new kind of hierarchical multiple-image encryption method based on the cascaded interference structure and vector stochastic decomposition algorithm is proposed.In this method,by using the unequal modulus decomposition and vector stochastic decomposition algorithm,the Kth-level secret image modulated by a random phase distribution is analytically encoded into a Kth-level phase-only mask(POM)key and the(K-1)th-level complex amplitude field whose real amplitude is the(K-1)th-level secret image.Then,served as the input condition,the generated complex amplitude field is further encoded into a(K-1)th-level POM key and the(K-2)th-level complex amplitude,and so on,until the 1st-level complex amplitude field is decomposed into two POMs:one is the 1 st-level key,and the other is the ciphertext.When decrypting,only when the high-level users simultaneously obtain all the correct keys and ciphertext,the secret images can be retrieved successfully.(4)An optical image encryption scheme based on singular value decomposition ghost imaging(SVDGI)is proposed.Firstly,the singular value of random matrix is set to 1.0 by using singular value decomposition(SVD)transformation,and a new measurement matrix key with partial orthogonality is constructed by inverse SVD transformation.Secondly,the encryption of plaintext image is completed by multiplying new measurement matrix by plaintext image,and the ciphertext without spatial resolution is collected by a bucket detector;then,the measurement matrix key is secretly shared by both the sender and the receiver,and the ciphertext is transmitted in the public channel;finally,the receiver who intends to obtain the plaintext image can complete the decryption quickly according to the SVDGI decryption reconstruction algorithm with only one step of matrix multiplication operation.Because the shared measurement matrix key has no relationship with the plaintext image,and the ciphertext,a one-dimensional light intensity sequence,which has relationship with the plaintext image,has no spatial resolution,so an individual with only the ciphertext or the key can't successfully decrypt,which guarantees the security of the cryptosystem.Compared with traditional computational ghost imaging,differential ghost imaging and pseudo-inverse ghost imaging,SVDGI has distinguished advantages in fidelity of decrypted plaintext,decryption speed and systematic robustness.