Judging Condition Of Opacity Of Synchronous System Based On DES

With the development of society,information technology has been developed rapidly.Mean-while,the resulting information security has become an issue that needs to be solved urgent-ly since society has become highly informational.Either language-based or state-based research is to verify the opacity of a single system,based on the existing opacity verifi-cation algorithms under the Automaton and Petri net models.System opacity verification for the synchronous systems becomes necessary since the simultaneous operation in multi-ple systems is very popular.The first problem is the computationally complex judgement of the opacity in multi-system synchronization when performing opacity verification under multi-system synchronization.There are many algorithms to judge the opacity of a system,and these algorithms often need to traverse the entire system behavior.The computational complexity increases exponentially with the states of a system,so we may face the problem of state explosion using the constructed judgment model.Secondly,the multi-system syn-chronization operation must be performed at first,once the opacity of a multi-synchronous system is judged.However,it is difficult to synchronize these two or more independent systems together in many cases due to various reasons on funding and geography.Consid-vring these two shortcomings,this paper proposes a new synchronization system opacity verification method,only for the case that the unobservable event sets of each system are the same and belong to the common event set or relevant event set.If information securi-ty is classified according to the object of protection,it is mainly divided into the security of information content and the security of information dissemination mechanism.This pa-per studies the latter and abstracts the information dissemination mechanism to obtain the corresponding discrete event system model.After we use the automaton for mathematical modeling,the opacity of the system is analyzed and judged through the established model.The main work of this paper includes:Firstly,the thesis proposes a language-based synchronization system opacity verification algorithm.This algorithm can obtain system opacity results through language calculation.For the determination of whether the system secret information can be kept secret after synchronization,it is not necessary to synchronize multiple systems.This paper classifies the secret states of the system according to the secret states of the source system.The partial secret states and the complete secret states are defined in this paper.We propose three opacity verification algorithms for the synchronization system,according to the definitions of the secret state of the synchronization system.Secondly,an opacity verification algorithm for state-based synchronization systems is de-veloped.This algorithm not only decreases the computational complexity of the traditional method but also eliminates the synchronous product.The paper gives definitions of relevant state set,relevant event set,relevant state relationship set and relevant system.In order to judge if the synchronization system is opaque,we only need to judge the opacity of the rel-evant system.Computational complexity is greatly decreased by the reduction of the state of the relevant system,since the computational complexity of the opacity of the judgment system increases exponentially with its state.