Street-Level Trust Semantics for Attribute Authentication

The problem of determining whether a receiver may safely

accept attributes

(e.g., identity, credentials, location) of

unknown senders

in various online social protocols is a special instance of a more general problem of establishing trust in interactive protocols. We introduce the notion of

interactive trust protocols

to illustrate the usefulness of

social collateral

in reducing the inherent trust asymmetry in large classes of online user interactions. We define a social collateral model that allows receivers to accept attributes from unknown senders based on explicit recommendations received from social relations. We use social collateral as a measure of both social relations and “tie strength” among individuals to provide different degrees of accountability when accepting attribute information from unknown senders. Our model is robust in the face of several specific attacks, such as impersonation and tie-strength-amplification attacks. Preliminary experiments with visualization of measured tie strength among users of a social network indicate that the model is usable by ordinary protocol participants.