An Encryption System Based On Virtual Optical And Spatiotemporal Chaos

With the rapid development of computer networ, more and more information is now beingtransmitted through the Internet, include sensitive information such as personal privacy,commercial secrets and even state secrets. Therefore, information security has become a hotresearch topic with more and more people working on it. As to ensuring information security，encryption is a common and effective choice.Combining modern optical technology with encryption technology, Optical encryption hasreceived widespread attention and presents some advantages, such as multidimensional property,high degree freedom, large capacity, high robustness and inherent fast parallel processing propertyof optical element. Optical encryption system uses2-D random phase plate as secret key, in whichthe key space of two-dimensional random phase plate is very large and system security is good.In recent years, virtual optical encryption has been proposed, which makes use of computer tosimulate optical encryption and simplifies the implementation process of encryption system. Thesecret key of random mask in virtual optical encryption system is a2-D matrix, taking too muchmemory space and costs of storing, management and transmitting. In allusion to the fact thatspatiotemporal chaotic system produces a large number of uncorrelated pseudo-random sequencesand is very sensitive to the chaotic initial value and control parameters, we propose a novelencryption scheme combining spatiotemporal chaotic system with virtual optical lens imagingencryption technique. In this scheme, some spatiotemporal chaotic sequences are generated toencrypt important information safely. Three parameters of spatiotemporal chaotic system took theplace of random mask and reduce memory space. The simulation result revealed that the secretkey of this encryption scheme has high precision and this encryption scheme can resist exhaustiveattack in certain key space. Moreover, this thesis verifies the security of the system in terms ofencryption algorithm complexity, nonlinear property and resistance to attack, etc. But theresistance to choice plaintext attack of this new scheme is weak, therefore a improved scheme isproposed. The improved scheme cascades the original scheme and another encryption system, itincreases the complexity of the encryption model, so that it can resist choose plaintext attack, butit’s algorithm complexity is not high, and key space is more than twice of the original scheme, soit can resist exhaustive attack. For those reasons, the improved scheme is safe on the algorithm.