Research On Optical Encryption And Authentication Technique Based On Phase Retrieval Algorithm

In nowadays, with the continuous updating and development of internet technology, internet algorithm such as electronic trading, information transmission and identification is becoming more and more common, furthermore, people can trade and communicate without the traditional face to face style communication. The quick and cheap character of the digital transmission method provides a great convenience to our daily life and working. However, the internet system is facing all kinds of potential risk owing to the total transparency and easy operation feature of the internet information. How to authenticate the identity of both parts in communication precisely and insure the security of communication channel to avoid intruders from stealing, tampering even forging the information has already been the hot topic in information security field.Since the double random phase encoding (Double Random Phase Encoding, DRPE) technique in Fourier domain was proposed in 1995, more and more researchers turned their attention to the brand new area of optical image encryption and authentication. Many optical information processing technologies were developed to respond to various of security issues. Phase retrieval algorithm, acted as one of the more representative security algorithm, has been widely accepted by specialists in and abroad in digital information security field, and with the constant innovation of theoretical technology, the double random phase encoding technology combined with other classic optical information processing technology or transformation successfully, and extended the encryption and authentication algorithm from the Fourier domain to the Fresnel domain, Wavelet transform domain, Gyrator domain and some other domains. Besides, some new cryptology derived from the double random phase encoding technology such as phase retrieval algorithm and phase truncation was popularized and used in practical application.The thesis gives a concise explanation of some basic concepts in optical information security field and a detailed introduction of some common optical image encryption and authentication technologies. The lecture combined with some other relevant technology in optical information processing field on the basis of phase retrieval algorithm, and designed some new encryption and authentication systems with higher security factor.The main research work of this thesis is arranged as follows:(1) Combined with the (t,n) threshold secret sharing method and iterative phase retrieval algorithm in Fresnel domain, we proposed a kind of multiple level authentication scheme for multiple images. Encode the certified image into two phase masks based on the iterative phase retrieval algorithm in Fresnel domain, and divide one of the phase masks into n parts based on the (t, n) threshold secret sharing method and dispatch them to n participants via secure channel, any t participants can retrieve the information of the original phase mask and pass the high-level authentication process with a higher authority, while less than t participants with their keys can’t acquire any useful information of the phase mask, thus can’t pass the authentication system, but with one pair of correct authentication keys, one can pass the low-level authentication process with a lower authority. The system designed overcomes the one to one principle of the traditional authentication system and the introduction of the low-level authentication part and multiple-participant authentication process improves the security of the system.(2) We proposed a kind of authentication system for multiple images based on the multiplexing of complex amplitude and RSA algorithm. Generate the corresponding complex amplitude information of each image in the input plane, respectively, based on iterative phase retrieval algorithm. Rotate the original binary amplitude mask with each pair of column and row vector random numbers to obtain the sampling mask for every image. Sample and multiplex all the complex amplitude information and have the column and row vector numbers encoded into ciphers with the public keys of RSA. Authenticators with their private keys can decrypt the correct vector numbers and with which the system can rotate the original binary amplitude mask into the corresponding sampling mask. When all the authenticated information are placed at the right place, by computing and displaying the nonlinear correlation coefficient of the output image with the standard authentication image, the system can easily decide whether the authentication process is successful or not. The multiple-image authentication system spares the storage capacity of the sampling mask and improves the security and transmission efficiency of the system.(3) A multilevel authentication system for multiple images is promoted in which the low-level authentication image acted as the amplitude restricted condition at the transform plane is encoded into two phase masks placed at the input and transform plane, respectively, based on phase retrieval algorithm. Extract the real part out of the complex amplitude information in the input plane and have them modulated by the corresponding mask and multiplexed as the low-level authenticated image delivered to the certification center and the modulation masks after sampling are served as the authentication keys for the low-level authentication part. The low-level authentication image is served as the restricted condition, iteratively encode the high-level authentication image into two phase masks in the input and transform plane, respectively, and multiplex all the phase information in the transform plane and design the demultiplex keys as the high-level authentication keys for authenticators. The system realized multiple-level authentication process for multiple images which helps increase the capacity for authentication. During the authentication, only those who have passed the low-level authentication process have the authority for the high-level part which improves the security of the scheme to some extent.(4) We proposed a cryptosystem for three images based on phase-truncated Fresnel transform, basic vector decomposition and XOR algorithm. Encode any two of the three encrypted images into two phase masks, respectively, based on basic vector decomposition in which one of the phase masks is shared by the two images. Put XOR result of the third plaintext image and the shared mask in the input plane and the two unshared masks in the input and transform plane, respectively, an amplitude type ciphertext is obtained in the output plane via phase-truncated Fresnel transform. Deliver the shared mask and the two truncated masks to the user as the decryption keys via a secure channel. We tested the robustness of the cryptosystem which turns out that the cryptosystem we design here has a good ability for brute attack compared with the traditional schemes.