A dynamically typed access control model

Abstract

This paper presents the Dynamically Typed Access Control (DTAC) model for achieving secure access control in a highly dynamic environment. It simplifies the access control matrix model of Harrison, Ruzzo and Ullman by dropping the distinction between subjects and objects. It adds dynamic typing to cater for environments in which both rights and types can change. Its resulting flexibility means that it can be used to construct other security models, such as role-based access control or lattice based hierarchical models. The paper presents a formal definition of the DTAC model. A novel feature is that, instead of attempting to prove safety per se, we outline a technique to dynamically maintain a safety invariant. This is important because the run-time checks for the invariant are tractable, whereas equivalent static proofs would be intractable.