Chapter 23 - Policies, Access Control, and Formal Methods

Abstract

Access control is a key component of any security solution supporting fine-grained articulated protection for shared data and resources. It is today more crucial than ever, as organizations need to share data with many different parties, and yet make sure that business-critical and privacy-sensitive data are not leaked to unauthorized parties. Access control determines which subjects can access which resources under which circumstances. This chapter provides an overview of access control models and mechanisms. The chapter begins with a discussion of security policies, which also covers regulatory acts and laws such as the ones concerning the disclosure of privacy-sensitive data. It also presents an organizational framework which includes all components that are needed for a comprehensive access control solution. It then introduces an overview of basic notions, such as the notion of access control matrix, and access control models; the covered models include: the mandatory access control model, initially proposed for military applications, and today implemented by several products, also for commercial usages; the discretionary access control model; the role-based access control (RBAC) model with some of its well-known extensions, like T-RBAC and GEO-RBAC; privacy-aware RBAC (P-RBAC) specifically addressing access control for privacy-sensitive data; the recent attribute-based access control (ABAC) model, which has been implemented by the well-known XACML standard. The chapter will also look into recent research trends, such as risk-based access control, and recent proposals for implementing fine-grained access control through encryption. The discussion on access control models is complemented by a presentation of tools for analyzing access control policies, to determine conflicts and redundancies, and for integrating access control policies. The chapter then presents an overview of main formal methods used in access control models and mechanisms. Notions that are discussed include: propositional logic, model checking, program verification, and binary decision diagrams. The overview is complemented by examples of applications of these techniques to access control and also security more in general. The chapter concludes with a discussion of about access control for the protection of critical infrastructures, and current trends in access control research.