Survey of Trust

1. Trust by certification

• X.509
• PGP User Guide
• SPKI/SDSI Certificates

  SPKI/SDSI certificates use credentials to support authorizations.

2. Social Trust

(a) Reputation/Recommendation

We decide whether to trust someone based on their reputations. Reputations are established through some interaction. An example of reputation based system is the user ratings of eBay. To a certain extend, PGP web of trust is also a form of reputation systems since a user is able to express how much he trusts a public key. The trust values can be propagated through the web of trust.

• A. Abdul-Rahman and S. Hailes, "Supporting Trust in Virtual Communities". Hawaii Int'l. Conf. System Sciences 33, 2000, Maui, Hawaii (PDF)

  This paper provides a model that is based on reputation or word-of-mouth to allow agents to decide which other agents' opinions they trust more.

• E. Damiani, D. Vimercati, S. Paraboschi, P. Samarati, F. Violante, "A reputation-based approach for choosing reliable resources in peer-to-peer networks". Proceedings of the 9th ACM conference on Computer and communications security, pp. 207 - 216, Washington, DC, USA. (PDF)

  An example of application of reputation-based trust in P2P scenario. To access a P2P resource, the resource requestor first establish the reputation of the resource by a distributed polling algorithm.

• S. Marti, T. J. Giuli, K. Lai and M. Baker, "Mitigating routing misbehavior in mobile ad hoc networks". In Proceedings of the Sixth annual ACM/IEEE International Conference on Mobile Computing and Networking, pages 255--265, 2000. (PDF)

  An application of reputation-based trust for routing in mobile ad hoc networks. This work consists of a watchdog that identifies malicious nodes and a pathrater that evaluates a route.

(b) Incentive-based

Trust is established by assuming that each individual is rational and seeks to maximise his utility. The goal is to design a protocol such that the only way an individual can maximise his utility is by following the protocol faithfully.

• J. Shneidman and D. Parkes. "Rationality and self-interest in peer to peer networks". International Workshop on Peer-to-Peer Systems (IPTPS), 2003. (PDF)

  The authors argues that rationality is the real issue in P2P networks and introduce the fields of Algorithmic Mechanism Design (AMD) and Distributed Algorithmic Mechanism Design (DAMD) to design networks with rational nodes. AMD and DAMD introduce game theoretic ideas into a computational system. However, the authors did not give a specific implementation in this paper.

• R. Morselli, J. Katz, B. Bhattacharjee. "A Game-Theoretic Framework for Analyzing Trust-Inference Protocols" In P2Pecon 2004. (PDF)

  This describes a game-theoretic framework for analyzing the robustness of trust-inference protocols in the presence of adversarial (but rational) users.

• S. Buchegger and J. Le Boudec. "Performance Analysis of the CONFIDANT Protocol: Cooperation Of Nodes --- Fairness In Dynamic Ad-hoc NeTworks". In Proceedings of IEEE/ACM Symposium on Mobile Ad Hoc Networking and Computing (MobiHOC), Lausanne, CH, June 2002.

  The protocol discourages misbehavior by isolating misbehaving nodes. Assuming nodes are rational, they are encouraged to cooperate.

3. Trust Management

• M. Blaze, J. Feigenbaum, and J. Lacy, "Decentralized Trust Management". In Proceedings of IEEE Conf. Security and Privacy, 1996, Oakland, California, USA. (PDF)
• M. Blaze, J. Feigenbaum, J. Ioannidis and A. Keromytis, "The Role of Trust Management in Distributed Systems Security," Secure Internet Programming: Security Issues for Mobile and Distributed Objects, Vitek and Jensen, Eds., 1999, Springer-Verlag. (PDF)
• M. Blaze, J. Feigenbaum, J. Ioannidis and A. Keromytis, "RFC2704 - The KeyNote Trust Management System Version 2", 1999. (TXT)

  Trust management is defined as "a unified approach to specifying and interpreting security policies, credentials and relationships that allow direct authorization of security critical actions".

  The authors introduced PolicyMaker and Keynote as tools for automated trust management systems. PolicyMaker specifies what a public key is authorized to do. It binds the access rights to the public key, unlike X.509 which only binds identity to a public key. PolicyMaker also evaluates whether an intended action is allowed by the local policy. KeyNote is an extension of PolicyMaker.

• N. Li, J. Mitchell, and W. Winsborough, "Design of a role-based trust management framework". In Proceedings of the IEEE Symposium on Security and Privacy, Oakland. (PDF)

  This trust model addresses the distributed nature of authority. It introduces localized authority over roles and delegation. It also introduces the separation of duty policy concept, where two or more different people are responsible for completion of critical tasks.

4. Trust Model

• S. Marsh, "Formalising Trust as a Computational Concept". Ph.D. Thesis. Department of Mathematics and Computer Science, University of Stirling, 1994. (PDF)

  A formal model for trust is built based on observations from fields such as psychology, sociology and economics. It consider many factors that determine trust and the behavior of agent (cooperate or defect). For example, the utility and importance of the situation, competency of the trustee and the situational risks.

• A. Jøsang, "The Right Type of Trust for Distributed Systems". ACM New Security Paradigms Wksp., 1996. (PDF)

  This paper examines the types of trust and trust relationships which are relevant for information security. It makes a distinction between passionate entities (human-like) and rational entities which are system entities. Trust is then the belief that a rational entity will resist malicious manipulation or that a passionate entity will behave without malicious intent. The paper also introduces different types of trust relationships between different types of entities.

• R. Yahalom, B. Klein and T. Beth, "Trust relationships in secure systems---A distributed authentication perspective". In Proceedings of the 1993 IEEE Symposium on Research in Security and Privacy, pages 150--164, May 1993.

  This work introduces a Trust Classification. An entity being trusted for a particular class means that the entity is trusted to perform specific tasks without necessarily being trusted for other tasks. Examples of classifications: key generation, keeping secrets, identifying entities, providing recommendations etc.

• T. Beth, M. Borcherding and B. Klein. "Valuation of Trust in Open Networks". In Proceedings of the Third European Symposium on Research in Computer Security, pp. 3--18, Springer-Verlag, 1994.

  This presents a method for valuation of trustworthiness. The method is based on reputations from several mediators.

5. Survey

• T. Grandison and M.Sloman, "A survey of trust in Internet application". In IEEE Communications Surveys, Fourth Quarter, 2000. (PDF)

  A comprehensive survey of the literature. Most of the above works are mentioned in this survey as well.