Authorization in distributed systems: a formal approach

In most systems, authorization is speciied using some low-level system-speciic mechanisms, e.g. protection bits, capabilities and access control lists. We argue that authorization is an independent semantic concept that must be separated from implementation mechanisms and given a precise semantics. We propose a logical approach to representing and evaluating authorization. Speciically, we introduce a language for specifying policy bases. A policy base encodes a set of authorization requirements and is given a precise semantics based upon a formal notion of authorization policy. The semantics is computable , thus providing a basis for authorization evaluation. We also introduce two composition operators for policy bases, which are appropriate for modeling distributed systems with multiple administrative domains.