Enforcing RBAC Policies over Data Stored on Untrusted Server (Extended Version)

One of the security issues in data outsourcing is the enforcement of the data owner’s access control policies. This includes some challenges. The first challenge is preserving confidentiality of data and policies. One of the existing solutions is encrypting data before outsourcing which brings new challenges; namely, the number of keys required to access authorized resources, efficient policy updating, write access control enforcement, overhead of accessing/processing data at the user/owner side. Most of the existing solutions address only some of the challenges, while imposing high overhead on both owner and users. Though, policy management in the Role-Based Access Control (RBAC) model is easier and more efficient due to the existence of role hierarchical structure and role inheritance; most of the existing solutions address only enforcement of policies in the form of access control matrix. In this paper, we propose an approach to enforce RBAC policies on encrypted data outsourced to a service provider. We utilize Chinese Remainder Theorem for key management and role/permission assignment. Efficient user revocation, efficient role hierarchical structure updating, availability of authorized resources for users of new roles, and enforcement of write access control policies as well as static separation of duties, are of advantages of the proposed solution.