Integrity-OrBAC: a new model to preserve Critical Infrastructures integrity

Abstract

Nations development depends heavily on the proper functioning of their Critical Infrastructures (CIs). Their security requirements are very important since small dysfunctions can deeply affect nation stability. We focus on their integrity need because Critical Information Infrastructures (CIIs) manipulate data that must be correct. The differentiation of their various elements security needs is essential to their protection. Unfortunately, existent access control models do not completely meet the CIIs requirements for many reasons. The Organization-Based Access Control (OrBAC) model, however, presents several strengths but it does neither consider the differentiation concept nor cope with integrity issues. In this paper, we work to enrich OrBAC with integrity mechanisms and means of differentiation. Integrity-OrBAC (I-OrBAC) is our extension and it is a proactive model. I-OrBAC is a multi-integrity level model that enables quantifying the integrity needs of each CII element, in term of credibility or criticality, to take optimal access control decisions. Given a triple (context, view and activity), we propose a way to determine the best subjects of the role selected to perform the activity through the calculation of integrity level thresholds. This idea is illustrated by a security policy example. We also propose a role priority concept and an algorithm that make security policies more flexible. The algorithm is described by an inference system. Regarding the implementation, we extend XACML to reflect the properties of our entities. Steps for access decision-making are detailed and scenarios used to test the implementation are presented.