Double Random Phase Encryption Technique-An Optical Realization Of Affine Cryptography

The development of the double random phase encryption technique has been reviewed in this doctoral dissertation. Based on the summary of the existing schemes of double random phase encryption, a new research for the cryptology explanation of its ability to realize maintaining secrecy of optical information has been implemented. Some detailed analysis and discussion have been made for the problems such as security of this technique. Operable schemes have been proposed for some practical applications. The main contents and results have been summarized as follows:It is put forward that the encryption mechanism of optical images by the double random phase encryption technique can be categorized to the affine cipher on the cryptology and this technique can be regarded as an optical realization of the affine cipher. The secrecy comes from making best of diffusion and confusion techniques. The relationships between the plaintext and the ciphertext, the plaintext and the key have been complicated for the purpose of disordering the plaintext. Five main factors of the cryptosystem based on the double random phase encryption have been analyzed systematically as well as the theoretical security and practical security of that cryptosystem. According to the equation of imaging, the affine map relationship between the original image and encrypted image has been illustrated in the technique based on the optical 4f system and Fresnel diffraction domain. The statistical property of the encrypted image has been discussed by utilizing the model of affine cipher and the related theory of stochastic process. It has been verified by numerical simulations that the encrypted image may be regarded as stochastic white Gaussian noise. The characteristics on cryptology of the cryptosystem based on the double random phase encryption have been summarized.