Research On Image Encryption Technology Based On The Computer-Generated Holography

The rapid development of modern network technology and communication technology has made information exchange increasingly close.As an important part of information transmission,the security issues of image information has become the focus of people's attention.The generation of encryption technology ensures the security of information in communication and transmission,and how to improve the security and information capacity of encrypted information has become an important research topic of information encryption.With the rapid development of computer technology,the computer generated holography(CGH)technology also comes into being,which combines optical holography with computer technology to realize the functions that optical holography cannot accomplish.The CGH replaces the field recording of optical equipment,and at the same time it can realize the production of virtual object information hologram,which makes the CGH surpass optical hologram in digital image processing,and brings a new leap for the development of holographic display and image encryption technology.The wide application of information network technology makes the increase of the image information capacity,how to achieve large capacity,multidimensional and efficient image encryption is one of the main directions of current research.As an important branch of image encryption technology,the information encryption technology based on CGH provides an effective way for the encryption of big data due to its characteristics of high speed,parallelism,multi-dimensional and large capacity,and has become a research hotspot in the field of image information encryption.Aiming at the problem of big date information encryption,this paper carried out the research on the image encryption technology of CGH.The main contents of this paper are as follows:1.This paper briefly introduces the basic principle of holography and encryption technology.Firstly,the basic principles of optical holography and computational holography are introduced,and the fabrication principle and numerical simulation results of Fresnel holography are given.In the introduction of image encryption technology,the classic image encryption algorithms(such as phase recovery algorithm(GSA)and double random phase encoding(DPRE)algorithm)are briefly introduced,and the improved classical algorithm is briefly described.The CGH encryption technology and its development are introduced.The flow chart of the principle of Fourier transform CGH encryption and decryption is given.The application of multi-image and three-dimensional object en cry ption technology in the encryption of big data information is expounded.Among them,the multi-images encryption scheme and 3d object encryption scheme are introduced in detail in the Chapter 3 and Chapter 4.2.A multi-images encryption scheme based on pure phase holography is proposed.In this encryption scheme,multiple images to be encrypted are transformed into pure phase images by iterative algorithm,and then encrypted with different random phases.The encrypted phase-only images are performed by inverse Fourier transform,respectively,thus new object functions are generated.The new function is propagated to specific areas of different distances by angular spectrum diffraction and superimposed to form a single image.A single image is multiplied by a random phase in the frequency domain,and then the phase portion of the spectrum is truncated and the amplitude in formation is reserved.The random phase,propagation distances,truncated phase information in frequency domain are employed as multiple dimensional keys.Among them,the iteration processing and sparse distribution greatly reduce the crosstalk among the multiple encryption images.The superposition of image sequences greatly improves the capacity of encrypted information.Several numerical experiments based on a designed optical system demonstrate that the proposed scheme can enhance encrypted information capacity and make image transmission at a highly desired security level.3.Aiming at the problem of reducing the loss of the encrypted information and increasing the information capacity,a 3d object encryption algorithm based on the phase iteration algorithm in angular spectrum domain is proposed.The algorithm uses the layered angular spectrum method to encode the 3D objects to generate a CGH,and then CGH is encoded into three phase plates by phase iteration algorithm to realize the encryp tion of the 3D object images.The numerical simulation analysis shows that the algorithm realizes the encryption and decryption of three-dimensional objects,guarantees the security of encrypted information,and increases the capacity of encrypted information.