Access control models have traditionally included mandatory access control (or lattice-based access control) and discretionary access control. Subsequently, role-based access control has been introduced, along with claims that its mechanisms are general enough to simulate the traditional methods. In this paper we provide systematic constructions for various common forms of both of the traditional access control paradigms using the role-based access control (RBAC) models of Sandhu et al., commonly called RBAC96. We see that all of the features of the RBAC96 model are required, and that although for the manatory access control simulation, only one administrative role needs to be assumed, for the discretionary access control simulations, a complex set of administrative roles is required.

We describe in more detail than before the reference model for role-based access control introduced by Nyanchama and Osborn, and the role-graph model with its accompanying algorithms, which is one way of implementing role-role relationships. An alternative role insertion algorithm is added, and it is shown how the role creation policies of Fernandez et al. correspond to role addition algorithms in our model. We then use our reference model to provide a taxonomy for kinds of conflict. We then go on to consider in some detail privilegeprivilege and role-role conflicts in conjunction with the role graph model. We show how role-role conflicts lead to a partitioning of the role graph into nonconflicting collections that can together be safely authorized to a given user. Finally, in an appendix, we present the role graph algorithms with additional logic to disallow roles that contain conflicting privileges.

Attribute-based access control (ABAC) is a promising alternative to traditional models of access control (i.e., discretionary access control (DAC), mandatory access control (MAC), and role-based access control (RBAC)) that is drawing attention in both recent academic literature and industry application. However, formalization of a foundational model of ABAC and large scale adoption is still in its infancy. The relatively recent emergence of ABAC still leaves a number of problems unexplored. Issues like delegation, administration, auditability, scalability, hierarchical representations, and the like, have been largely ignored or left to future work. This article provides a basic introduction to ABAC and a comprehensive review of recent research efforts toward developing formal models of ABAC. A taxonomy of ABAC research is presented and used to categorize and evaluate surveyed articles. Open problems are identified based on the shortcomings of the reviewed works and potential solutions discussed.

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