Known-Plaintext Attack On Optical Encryption Based On Double Random Phase Encoding

With the rapid development of networked multimedia techniques, the information security is facing more and more challenges nowadays. Optical systems are of growing interests for image encryption because of their distinct advantages of processing two-dimensional complex data in parallel and at high speed. The research area in optical cryptography has been enlightened and various optical encryption schemes have been proposed during the past decades. These methods convert the plaintext to stationary white noise by use of two random phase keys. However, the characteristics of ciphertext may expose the existence of secret information in the data transmission and attract attention of eavesdroppers. The security of optical cryptographic system has become a great concern in recent years. According to cryptanalysis, any optical security system could not be claimed secure unless it was able to endure various attacks. Chosen-ciphertext attack, known-plaintext attack and chosen-plaintext attack were proposed to explore the security strength of DRPE. Those attacks have demonstrated that the security flaws originate from the linearity of the DRPE.This article briefly discusses the concepts of cryptography and the basic theory of optical cryptography, recalling the development profiles and Research of double random phase encoding in the past period of time.We focus on three optical encryption based on 4f system. Double random phase encryption system is the most classic one. Fresnel transform optical encryption system shows a higher security because of multiplicity of its key. POCS algorithm-based optical encryption system is a new encryption emerged only in recent years. For the encryption effect of three systems, numerical simulations of the experimental results are showed in this paper.We contrast the advantages and disadvantages of GS algorithm, error reduction algorithm and hybrid input-output algorithm by Numerical simulations. Analyze their convergence using the curve of the NMSE versus number of iterations. And thus discuss the factors that affect their convergence. The theoretical derivation is given by a known plaintext attack to decrypt the double random phase encoding optical encryption system.We theoretically derive the method of breaking the two systems by known plaintext attack through analyzing the encryption equation and system architecture of Fresnel field double random phase encryption system and the constraint set projection algorithm based on double random phase encryption system. Then give the simulation results of known plaintext attack on double random phase encryption system based on constraint set projection algorithm.