Trust in Self-organized Mobile Ad Hoc Networks
|Ομιλητής||John S. Baras, Martin Marietta chair Professor, Electrical and Computer Eng. Dept, University of Maryland, Director NASA Center for Satellite and Hybrid Communications networks|
|Τίτλος||Trust in Self-organized Mobile Ad Hoc Networks|
|Ημερομηνία||Τετάρτη 30/03/2005, ώρα 13:00|
|Χώρος||Αίθουσα Σ, Παραλιακό Συγκρότημα Παπαστράτου|
|Διεύθυνση||Αργοναυτών και Φιλελλήνων, Βόλος|
As an important concept in network security, trust is interpreted as a set of relations among agents participating in the network activities. Trust relations are based on previous behaviors of agents. Trust management in distributed and resource-constraint networks, such as mobile ad hoc networks (MANETs) and sensor networks, is much more difficult but more crucial than in traditional hierarchical architectures, such as the Internet and base station- or access point-centered wireless LANs. Generally, this type of distributed networks have neither pre-established infrastructure, nor centralized control servers or trusted third parties (TTPs). The trust information or evidence used to evaluate trustworthiness is provided by peers, i.e. the agents that form the network. Trust management is a multifunctional control mechanism, in which the most important aspect is to establish trust from a small set of agents who are known to be trustworthy. The whole network evolves as the local interaction iterates from isolated trust islands to a connected trust graph. Our interest is to discover rules and policies that establish trust-connected networks using only local interactions, to understand the impact of local interactions on the whole network and also to find the conditions under which trust spreads to a maximum set, as well as the parameters (e.g. topology type) that speed up or slow down this transition. Another important aspect in trust management is trust revocation. Trust revocation is especially essential in mobile ad hoc environment because of the inherent properties of self-organized wireless communications. We analyze our local interaction rule using graph theory and percolation theory, and provide a theoretical justification for network management that facilitates trust propagation. We model the interactions among agents as cooperative games and provide rules that encourage agents to collaborate. This circle of ideas has a lot in common with randomized optimization methods from statistical physics, and especially from the theory of spin-glass materials. Phase transition is a common phenomenon that takes place in any combinatorial structure. As the number of nodes in the network becomes large, phase transition is inevitable in both trust establishment and revocation. In our trust establishment model, if the threshold is set just above the critical value, the network is separated into small groups of trusted nodes, while if the threshold is right below the critical value, the whole network emerges as a trusted giant component. We explain this rather surprising observation based on percolation theory and random graph theory.