Research On Privacy Analysis Of Discrete Event Systems Based On State Opacity

With the rapid development of Internet technology,the interaction between control system and communication network infrastructure is frequent,which makes confidential information vulnerable to intruders and other malicious entities.As an important confidential attribute in discrete event system,opacity can describe the ability of information system to hide its confidential information from any external observer.Therefore,the analysis and control of opacity is an important topic in the related fields of discrete event systems.Most of the existing research on opacity is based on formal method,which mainly adopts formal language to formally standardize and describe systems' attributes,and gives many profound and important theories.In the framework of semi tensor product of matrices,the verification of opacity can be extended to the algebraic mechanism with advantages in problem description and solution.In addition,the existing research on opacity mainly focuses on the logical system,and the time consumption or cost of state transition is not specified by default.However,under different engineering application backgrounds,the transition path of the system is given corresponding weight.Therefore,the study of opacity is extended to more complex weighting systems.The main research contents and innovative results of the paper are summarized as follows:1)For the verification of current state opacity of discrete event system,the state and input variables are expressed as logical vectors in the framework of semi tensor product of matrices,and the algebraic expression of discrete event system dynamics is proposed.Through iterative operation and Boolean logic operation,the necessary and sufficient algebraic condition for verifying current state opacity of the system is proposed.2)For the problem of K-step opacity verification of discrete event systems,this paper studies how to transform K-step opacity verification of discrete event systems modeled by nondeterministic finite automata into the construction of polynomial matrix.The matrix describes the state estimation of eavesdropping within the K-step observation of malicious intruders.Finally,the necessary and sufficient conditions for K-step opacity of the system are given.3)For the limitation that the traditional logic system can't quantitatively describe the system transition information,K-step(infinite step)opacity of the weighted discrete event system modeled by weighted automata is studied.By constructing Kstep(infinite step)weighted observation state set of the system,the weighted state estimation and weighted bidirectional observer with K-step(infinite step)delay are established,and the necessary and sufficient conditions for verifying K-step(infinite step)weighted opacity are proposed.