Emerging trust and risk management systems provide a framework for principals to determine whether they will exchange resources, without requiring a complete definition of their credentials and intentions. Most distributed access control architectures have far more rigid policy rules, yet in many respects aim to solve a similar problem. This paper elucidates the similarities between trust management and distributed access control systems by demonstrating how the OASIS access control system and its role-based policy language can be extended to make decisions on the basis of trust and risk analyses rather than on the basis of credentials alone. We apply our new model to the prototypical example of a file storage and publication service for the Grid, and test it using our Prolog-based OASIS implementation.

Trust-based recommendations control the exchange of personal information between handheld computers. Combined with explicit risk analysis, this enables unobtrusive information exchange, while limiting access to confidential information. This is illustrated with applications such as personal address books and electronic diaries. Recommendations associate categories with data and with each other with degrees of trust belief and disbelief. Since categories also in turn confer privileges and restrict actions, they are analogous to roles in a role-based access control system, while principals represent their trust policies in recommendations. Participants first compute their trust in information, by combining their own trust assumptions with others' policies. Actions are then moderated by a risk assessment, which weighs up costs and benefits, including the cost of the user's time, before deciding whether to allow or forbid the information exchange, or ask for help. By unifying trust assessments and access control, participants can take calculated risks to automatically yet safely share their personal information.