Optical Image Security Research Based On Complex-amplitude Ptychographic Encoding And Visual Cryptography

The development of The Times drives the progress of science and technology,which makes information technology more and more popular in our life.While people enjoy the convenience of life brought by information technology,the problem of information security arises spontaneously.Therefore,the research of information security is very necessary.The core of information security technology is cryptography,which is mainly composed of information encoding and decoding.Information coding is to encode secret information with high security encoding method.Decoding means that the receiver decodes the encoded information and obtains the secret information by knowing the encoding mode and key.Information encoding and decoding complement each other and constantly promote the development and progress of cryptography in opposition.In this thesis,an optical information hiding system based on complex-amplitude ptychographic encoding and visual cryptography is designed.Ptychography is a research hotspot in recent years,which is the latest development of lens-less coherent diffraction imaging(CDI)technology.It is a non-holographic interference coherent diffraction phase solution technique,the core of which is the overlap of diffraction patterns.These diffraction patterns,as the support constraints of each other,can not only recover the complex amplitude information of the object,alleviate the convergence difficulties of traditional CDI.In 2013,traditional ptychography was applied to optical information security for the first time,using it to encrypt optical images and improve the security of the system.Compared with the previous optical information hiding system,the system is expanded from phase-only key to complex-amplitude key,the encoded information is very resistant to GS algorithm extraction,and the security of the system is greatly improved.At the same time,a scheme of arbitrary complex amplitude optical field is designed by using two phase-only spatial light modulators(SLMS)and its mathematical analysis is given.In addition,the system combines the traditional visual cryptography scheme,it does not need to carry out complex encryption calculation,using the visual system of the human eye to realize the recognition of secret information directly.Because of its high security,simple and convenient operation,it has a wide range of applications.The introduction of visual cryptography converts the secret information into two unrelated visual keys,and the combination of the two reduces the probability of the ciphertext being intercepted during transmission.A series of ptychography parameters and the visual cryptography also ensure the security of the system.Finally,the feasibility,security and robustness of the system are verified by simulation.