Research And Design On Optical Multiple-image Authentication System Based On Phase Retrieval Algorithm

With the rapidly booming of Internet technology,multimedia communicating technique,cryptography,computer and modern communication systems,now we are entering a time when information safety and authentication are paid increasing attention.Since the technique of DRPE(double random phase encoding)method in the Fourier domain was proposed by B.Javidi and P.Refregier in 1995 to encrypt and watermark digital information,optical information security and authentication has become more challenging and attracted more and more researchers from all over the world to this new research field.Security system based on optical information processing generally adopts the techniques of optical information processing such as Fresnel transform,fractional Fourier transform and other related techniques such as compressive sensing and computational ghost imaging to encrypt information,hide and authenticate a watermark.Compared to other systems based on traditional techniques,the advantages of security systems based on optical information processing is that optical waveforms have high degrees of freedom such as amplitude,phase,nonlinear transforms and quantum properties of photons.Combined with multiplexing ability of optical systems,optical security systems are more secure and difficult to hack.This thesis firstly introduces the most recently-developed techniques of optical information security system also with some briefly introductions of some basic techniques of optical information encryption and/or digital watermarking.This thesis proposes some original optical security systems based on common optical information processing techniques such as iterative phase retrieval algorithm and multiplexing technique,combined with other related techniques(sparse representation).The main results and literatures of this thesis include three parts as following:(1)A multiple-image encryption scheme is proposed based on iterative phase retrieval algorithm and phase multiplexing technique.First the initial image to be encrypted is encoded into multiple phase masks,which are then multiplied into one image using phase multiplexing technique.This scheme can realize image encryption for multiple images at the same time in one set of ciphertexts and can considerably increase the efficiency of data transmission.(2)A study of image retrieval from the synthetic encoded image based on iterative phase retrieval algorithm and sparse represent,in which the phase part is constructed with random sampling and space multiplexing,has been made.Numerical simulations validate the feasibility of both studies and can remarkably increase the efficiency of information transmission and enhance the system security.(3)A multiple-image authentication method with a cascaded multilevel architecture in the Fresnel domain is proposed,in which a synthetic encoded complex amplitude is first fabricated,and its real amplitude component is generated by iterative amplitude encoding,random sampling,and space multiplexing for the low-level certification images,while the phase component of the synthetic encoded complex amplitude is constructed by iterative phase information encoding and multiplexing for the high-level certification images.Then the synthetic encoded complex amplitude is iteratively encoded into two phase-type ciphertexts located in two different transform planes.During high-level authentication,when the two phase-type ciphertexts and the high-level decryption key are presented to the system and then the Fresnel transform is carried out,a meaningful image with good quality and a high correlation coefficient with the original certification image can be recovered in the output plane.Similar to the procedure of high-level authentication,in the case of low-level authentication with the aid of a low-level decryption key,no significant or meaningful information is retrieved,but it can result in a remarkable peak output in the nonlinear correlation coefficient of the output image and the corresponding original certification image.Therefore,the method realizes different levels of accessibility to the original certification image for different authority levels with the same cascaded multilevel architecture.