A temporal-logic extension of role-based access control covering dynamic separation of duties

Security policies play an important role in today´s computer systems. We show some severe limitations of the wide-spread standard role-based access control (RBAC) model, namely that object-based dynamic separation of duty as introduced by Nash and Poland cannot be expressed with it. We suggest to overcome these limitations by extending the RBAC model with an execution history. The natural next step is then to add temporal logic for the specification of execution orders. We show that with this, object-based dynamic separation of duty, as well as other policies, can be adequately specified.