The ability to exchange data while maintaining sovereignty is fundamental to emerging decentralized data-driven ecosystems. Data sovereignty refers to the entity's capability to be self-determined concerning data usage. As such, a data usage control system (UCON) is critical for sovereignty. UCON, a generalization of attribute-based access control, enforces continuous authorization, allowing attribute mutability after access is granted. In theory, UCON comprises a policy language to express constraints and obligations of data usage, and a technology to evaluate and enforce them. In practice, realizing the above is challenging and poses trust concerns. Partly, this is due to the complexity of UCON (continuous authorization, obligations) and the advanced usage constraints (stemming from, e.g., regulations or business contracts) combined with the decentralized nature of data ecosystems that allow different actors (e.g., data provider, security engineers) to author policies, and operate UCON. To that end, we propose to aid actors with automated policy analysis and verification methods. We present a new policy analysis method based on the combination of symbolic execution for policy evaluation and SMT solving to compute concrete scenarios answering queries on the policies. Our approach supports symbolic queries, where attribute values may be concrete values, a range of values, or symbolic variables. We also propose a monitoring approach using RTLola tool to verify the correctness of UCON's behavior in terms of decisions, obligations, and user-specified properties. To monitor obligations, we define their essential parameters and show how to monitor their fulfillment based on the configuration. We also present eight templates that allow users to generate the most important properties for monitoring UCON.

Modern system architectures require sophisticated access and usage control mechanisms. The need stems from demanding requirements for security, data sovereignty and privacy regulations, as well as the challenges presented by architectural approaches like zero trust networking. Usage control systems provide one approach to encapsulate and manage the complexities related to access and usage control. In order to trust a usage control system, it is essential to ensure that usage control policies express the intended properties and are enforced correctly. To achieve this, we need a precise specification of the intended behavior of a usage control system. For attribute-based access control, the XACML standard is a sufficient specification of the behavior of policies. Usage control models, such as UCON, extend access control with features for continuous authorization based on mutability of attribute values. This adds significant complexity to the problem of specifying the intended behavior. In this paper, we identify challenges with specifying a practical usage control system regarding continuous control, obligations, and concurrency aspects. We describe an approach to specifying the UCON+ model of Dimitrakos et al. and outline an implementation of the specification with Answer Set Programming.

Access control has been traditionally used to protect data and privacy. Traditional access control models (e.g., ABAC, RBAC) cannot meet modern security requirements as technologies spread over heterogeneous and dynamic environments that need continuous monitoring. Modern models such as Usage Control (UCON) introduced the concept of continuous authorisation that has a lifecycle consisting of a series of phases through which the authorisation passes during its lifetime. However, such models assume a fixed lifecycle for all authorisations, so they cannot satisfy emerging technologies (e.g., smart vehicles, zero-trust, data flow), which require various and fine-grained lifecycles. Researchers have extended existing models to meet such requirements, but all solutions remain restrictive, as they are specially tailored for specific use-cases. In this paper, we propose an extensible model for continuous authorisations and usage control. The model enables its users to customise and dynamically configure the authorisation lifecycle as required by the use-case. This adds a layer of abstraction, forming a metamodel that can be instantiated into different flavours of continuous authorisation models, each addressing specific requirements. We also show that the authorisation lifecycle can be modelled as Deterministic Finite Automaton (DFA) and expressed in a structured language used by an evaluation engine to dynamically enact and manage the lifecycle. We layout the building blocks of the proposed metamodel and devise future research directions.

The rapid deployment of digital systems into all aspects of daily life requires embedding social constructs into the digital world. Because of the complexity of these systems, there is a need for technical support to understand their actions. Social concepts, such as explainability, accountability, and responsibility rely on a notion of actual causality. Encapsulated in the Halpern and Pearl's (HP) definition, actual causality conveniently integrates into the socio-technical world if operationalized in concrete applications. To the best of our knowledge, theories of actual causality such as the HP definition are either applied in correspondence with domain-specific concepts (e.g., a lineage of a database query) or demonstrated using straightforward philosophical examples. On the other hand, there is a lack of explicit automated actual causality theories and operationalizations for helping understand the actions of systems. Therefore, this paper proposes a unifying framework and an interactive platform (Actual Causality Canvas) to address the problem of operationalizing actual causality for different domains and purposes. We apply this framework in such areas as aircraft accidents, unmanned aerial vehicles, and artificial intelligence (AI) systems for purposes of forensic investigation, fault diagnosis, and explainable AI. We show that with minimal effort, using our general-purpose interactive platform, actual causality reasoning can be integrated into these domains.