Safety analysis is a fundamental problem in authorization models. Safety decidable models provide theoretical foundations for decentralized security administration. Attributes of objects are central to usage control authorization models. It has previously been shown that inclusion of a single infinite attribute leads to undecidable safety, even without any creation of objects. Therefore unrestricted inclusion of infinite attributes is not possible in a safety decidable model. On the other hand, it has recently been shown that the safety problem for the pre-authorization usage control sub-model with finite attribute domains, called PreUCONAfinite, is decidable even with unbounded object creation. A major limitation of finite attributes is the inability to link objects through attribute values in presence of unbounded object creation (since attributes that reference other objects must be infinite in this case). It would be desirable to have safety-decidable attribute-based models which include both finite and infinite attributes (necessarily with some restrictions). This paper develops a pre-authorization usage control sub-model, called PreUCONAid, with attribute domains solely comprised of infinite object identifiers with considerable restrictions on how these attributes can be updated. Safety decidability for PreUCONAidis proved by defining the notion of ω-equivalent usage configurations, and showing that the reachable set of v-equivalent usage configurations is computable and can be used to answer safety questions. The utility of such models in practice is illustrated by means of an example. The paper further shows that addition of even a single finite domain attribute to PreUCONAidresults in undecidable safety. These results indicate that combining finite and infinite attributes in a safety decidable model is a challenging task, which will likely require carefully crafted restrictions on updates to these attributes. The formulation of such a model remains an important open question.

Administrative rights are more powerful permissions and checking accountability of execution of admin rights is an important security measure. Most of the administrative RBAC models distribute rights to multiple administrators. Though such decentralized security management has difficulties in checking admin accountability, it is more efficient compared to centralized approach, particularly in large organizations. We introduced administrative obligations in ARBAC as a way to improve the accountability of admin users in the decentralized systems. The proposed approach would reduce the potential of security risk and improve accountability of security administrators. As the cloud and mobile applications are becoming integral part of business information systems, ensuring the accountability of admins play a vital role in system security. Obligations are well studied feature in the security literature and adding them into security administration would open up many possibilities for future developments in this direction.

This paper considers the safety problem for the pre-authorization sub-model of the well-known$UCON_{ABC}$usage control model, that is,$Pre\_UCON_A$. It is shown that$Pre\_UCON_A$with finite attribute domains has decidable safety even if arbitrary object creation is allowed. This result eliminates the previously known restrictions for obtaining safety decidability in this context, which only allow a finite bounded number of objects to be created. Our result specifically permits unbounded object creation, so the set of objects is potentially infinite. In the proof, we show that the set of reachable protection tuples in infinite state$Pre\_UCON_A$models is finite and computable. We also provide a construction for decision procedure which answers the safety question by examining the reachable protection tuples.