A nonmonotonic modal authorization logic for pervasive computing

• Published in: Security and communication networks 2015-04, Vol.8 (6), p.1077-1091
• Main Authors: Noorollahi, Ali, Fallah, Mehran S.
• Format: Article
• Language: English
• Subjects: Communication networks; Computer networks; Decisions; Dynamical systems; Logic; Mathematical models; modal authorization logic; nonmonotonicity; pervasive computing; Policies; Semantics; Ubiquitous computing
• ISSN: 1939-0114; 1939-0122
• DOI: 10.1002/sec.1063

Modal logics have proven invaluable for authorization in distributed systems. The logics devised so far, however, are inadequate to meet the requirements of pervasive environments. Such environments are, in general, characterized as open systems in which computing and communication facilities are provided to human users in a dynamic manner. These features suggest the need for the modification of existing logics in two directions. First, users’ capabilities being intrinsic to pervasive computing should be incorporated into the underlying modal logic. Second, the logic should be equipped with appropriate machinery so that it can deal with the imperfection in the information required for authorization. This paper has contributions in both directions. We present a logic that reflects how the capabilities of users change in different contexts. Nonmonotonicity is then added to the logic so that earlier decisions based on imperfect information can be retracted. The usefulness of our formulation is demonstrated through the added capacity it provides for specifying and enforcing access control policies in real‐life environments. We also present a minimal model semantics that reflects nonmonotonicity through the way it gives meaning to the formulas of the logic. Finally, we propose a sound and complete decision procedure based on semantic tableaux. Copyright © 2014 John Wiley & Sons, Ltd. Modal logics have been employed for authorization in distributed systems. New computing environments, however, pose new challenges in devising appropriate logics. This paper concentrates on the aspects of an effective authorization logic for pervasive computing and develops a nonmonotonic modal logic to this end. In particular, the logic proposed can handle uncertain and imperfect information about the principals and the contexts in which they make their requests.