Know What You Trust

In Decentralized Trust Management (DTM) authorization decisions are made by multiple principals who can also delegate decisions to each other. Therefore, a policy change of one principal will often affect who gets authorized by another principal. In such a system of influenceable authorization a number of principals may want to coordinate their policies to achieve long time guarantees on a set of safety goals. The problem we tackle in this paper is to find minimal restrictions to the policies of a set of principals that achieve their safety goals. This will enable building useful DTM systems that are safe by design, simply by relying on the policy restrictions of the collaborating principals. To this end we will model DTM safety problems in Scoll [1], an approach that proved useful to model confinement in object capability systems [2].