Opacity Of Discrete Event Systems: Analysis And Control

<p>The exchange of sensitive information in many systems over a network can be manipulated</p> <p>by unauthorized access. Opacity is a property to investigate security and</p> <p>privacy problems in such systems. Opacity characterizes whether a secret information</p> <p>of a system can be inferred by an unauthorized user. One approach to verify security</p> <p>and privacy properties using opacity problem is to model the system that may leak confidential</p> <p>information as a discrete event system. The problem that has not investigated</p> <p>intensively is the enforcement of opacity properties by supervisory control. In other</p> <p>words, constructing a minimally restrictive supervisor to limit the system's behavior so</p> <p>an unauthorized user cannot discover or infer the secret information.</p> <p>We describe and analyze the complexity of opacity in systems that are modeled as</p> <p>a discrete event system with partial observation mapping. We define three types of</p> <p>opacity: strong opacity, weak opacity, and no opacity. Strong Opacity describes the</p> <p>inability for the system's observer to know what happened in a system. On the other</p> <p>hand, No-opacity refers to the condition where there is no ambiguity in the system</p> <p>behavior. The definitions introduce properties of opacity and its effects on the system</p> <p>behavior. Strong opacity can be used to study security related problems while no opacity</p> <p>can be used to study fault, detection and diagnosis, among many other applications. In</p> <p>this dissertation, we investigate the largest opaque sublanguages and smallest opaque</p> <p>superlanguages of a language if the language is not opaque. We studied how to ensure</p> <p>strong opacity, weak opacity and no opacity by supervisory control. If strong opacity,</p> <p>weak opacity or no opacity is not satisfied, then we can restrict the system's behavior by a</p> <p>supervisor so that strong opacity, weak opacity or no opacity is satisfied. We investigate</p> <p>the strong opacity control problem (SOCP), the weak opacity control problem (WOCP),</p> <p>and no opacity control problem (NOCP).</p> <p>As illustrated by examples in the dissertation, the above properties of opacity can</p> <p>be used to characterize the security requirements in many applications, as anonymity</p> <p>requirements in protocols for web browsing. Solutions to SOCP in terms of the largest</p> <p>sublanguage that is controllable, observable (or normal), and strongly opaque were characterized.</p> <p>Similar characterization is available for solutions to NOCP.</p>

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Open Access Dissertation

Discipline thesis:degree_discipline

Electrical and Computer Engineering

Year dc:date.available

2013

Author dc:creator

• Ben Kalefa, Majed Mohamed

Contributors dc:contributor

• Feng Lin

• discrete event system
• opacity
• security
• Computer Sciences
• Electrical and Computer Engineering

Repository record dc:identifier

https://digitalcommons.wayne.edu/oa_dissertations/830

OAI identifier oai:identifier

oai:digitalcommons.wayne.edu:oa_dissertations-1829