A general theory of trust in networks of humans and computers must be built on both a theory of behavioral trust and a theory of computational trust.1 This argument is motivated by increased participation of people in online social networking, crowdsourcing, human computation, and socio-economic protocols, e.g., protocols modeled by trust and gift-exchange games, norms-establishing contracts, and scams/deception. We illustrate a class of interactive social protocols that relies both on trustworthy properties of commodity systems2 (e.g., verifiable end-to-end trusted path) and participant trust, since on-line verification of protocol compliance is often impractical; e.g., it can lead to undecidable problems, co-NP complete test procedures, and user inconvenience. Trust is captured by participant preferences (i.e., risk and betrayal aversion) and beliefs in the trustworthiness of other protocol participants. Both preferences and beliefs can be enhanced whenever protocol non-compliance leads to punishment of untrustworthy participants; i.e., it seems natural that betrayal aversion can be decreased and belief in trustworthiness increased by properly defined punishment. Similarly, it seems natural that risk aversion can be decreased and trustworthiness increased by feasible recovery from participant non-compliance.
A general theory of trust which focuses on the establishment of new trust relations where none were possible before would help create new economic opportunities. New trust relations would increase the pool of services available to users, remove cooperation barriers, and enable the “network effect” where it really matters; i.e., at the application level. Hence, it seems important that security research should enable and promote trust-enhancement infrastructures in human and computer networks; e.g., trust networks. Finally, we argue that a general theory of trust should mirror human expectations and mental models of trust without relying on false metaphors and analogies with the physical world.
Virgil D. Gligor received his B.Sc., M.Sc., and Ph.D. degrees from the University of California at Berkeley. He taught at the University of Maryland between 1976 and 2007, and is currently a Professor of Electrical and Computer Engineering at Carnegie Mellon University and co-Director of CyLab. Over the past thirty-five years, his research interests ranged from access control mechanisms, penetration analysis, and denial-of-service protection to cryptographic protocols and applied cryptography. Gligor was an editorial board member of several IEEE and ACM journals, and the Editor in Chief of the IEEE Transactions on Dependable and Secure Computing. He received the 2006 National Information Systems Security Award jointly given by NIST and NSA in the US, and the 2011 Outstanding Innovation Award given by the ACM Special Interest Group on Security, Audit and Control.