Formal Verification of Usage Control Models: A Case Study of UseCON Using TLA+

TL;DR

This paper demonstrates how formal verification using TLA+ can rigorously analyze and ensure the correctness of complex usage control models like UseCON, which integrate access control, digital rights, and trust management.

Contribution

It provides a formal specification and verification of the UseCON usage control model in TLA+, highlighting its correctness for up to 12 uses.

Findings

Formal specification of UseCON in TLA+

Verification confirms correctness for <=12 uses

Highlights complexity and importance of formal methods in usage control

Abstract

Usage control models provide an integration of access control, digital rights, and trust management. To achieve this integration, usage control models support additional concepts such as attribute mutability and continuity of decision. However, these concepts may introduce an additional level of complexity to the underlying model, rendering its definition a cumbersome and prone to errors process. Applying a formal verification technique allows for a rigorous analysis of the interactions amongst the components, and thus for formal guarantees in respect of the correctness of a model. In this paper, we elaborate on a case study, where we express the high-level functional model of the UseCON usage control model in the TLA+ formal specification language, and verify its correctness for <=12 uses in both of its supporting authorisation models.