A. James Clark School of Engineering

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Author: search.filters.author.Theodorakopoulos, Georgios EfthymiosSubject: search.filters.subject.Engineering, Electronics and Electrical

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    Robust Network Trust Establishment for Collaborative Applications and Protocols
    (2007-05-07) Theodorakopoulos, Georgios Efthymios; Baras, John S; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    In networks without centralized control (e.g. ad-hoc or peer-to-peer networks) the users cannot always be assumed to follow the protocol that they are supposed to. They will cooperate in the operation of the network to the extent that they achieve their own personal objectives. The decision to cooperate depends on the trust relations that users develop for each other through repeated interactions. Users who have not interacted directly with each other can use direct trust relations, generated by others, in a transitive way as a type of recommendation. Network operation and trust generation can be affected by malicious users, who have different objectives, and against whom any proposed solution needs to be robust. We model the generation of trust relations using repeated games of incomplete information to capture the repetitive operation of the network, as well as the lack of information of each user about the others' objectives. We find equilibria that provide solutions for the legitimate users against which the malicious users cannot improve their gains. The transitive computation of trust is modeled using semiring operators. This algebraic model allows us to generalize various trust computation algorithms. More importantly, we find the maximum distortion that a malicious user can cause to the trust computation by changing the reported trust value of a trust relation.
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    DISTRIBUTED TRUST EVALUATION IN AD-HOC NETWORKS
    (2004-05-04) Theodorakopoulos, Georgios Efthymios; Baras, John S; Electrical Engineering
    An important concept in network security is trust, interpreted as a relation among entities that participate in various protocols. Trust relations are based on evidence related to the previous interactions of entities within a protocol. In this work, we are focusing on the evaluation process of trust evidence in Ad Hoc Networks. Because of the dynamic nature of Ad Hoc Networks, trust evidence may be uncertain and incomplete. Also, no pre-established infrastructure can be assumed. The process is formulated as a path problem on a directed graph, where nodes represent entities, and edges represent trust relations. We show that two nodes can establish an indirect trust relation without previous direct interaction. The results are robust in the presence of attackers. We give intuitive requirements for any trust evaluation algorithm. The performance of the scheme is evaluated on various topologies.