Biblio

The concept of Internet of Things (IoT) has received considerable attention and development in recent years. There have been significant studies on access control models for IoT in academia, while companies have already deployed several cloud-enabled IoT platforms. However, there is no consensus on a formal access control model for cloud-enabled IoT. The access-control oriented (ACO) architecture was recently proposed for cloud-enabled IoT, with virtual objects (VOs) and cloud services in the middle layers. Building upon ACO, operational and administrative access control models have been published for virtual object communication in cloud-enabled IoT illustrated by a use case of sensing speeding cars as a running example. In this paper, we study AWS IoT as a major commercial cloud-IoT platform and investigate its suitability for implementing the afore-mentioned academic models of ACO and VO communication control. While AWS IoT has a notion of digital shadows closely analogous to VOs, it lacks explicit capability for VO communication and thereby for VO communication control. Thus there is a significant mismatch between AWS IoT and these academic models. The principal contribution of this paper is to reconcile this mismatch by showing how to use the mechanisms of AWS IoT to effectively implement VO communication models. To this end, we develop an access control model for virtual objects (shadows) communication in AWS IoT called AWS-IoT-ACMVO. We develop a proof-of-concept implementation of the speeding cars use case in AWS IoT under guidance of this model, and provide selected performance measurements. We conclude with a discussion of possible alternate implementations of this use case in AWS IoT.

Attribute-based access control (ABAC) expresses authorization policy via attributes while relationship-based access control (ReBAC) does so via relationships. While ABAC concepts have been around for a long time, ReBAC is relatively recent emerging with its essential application in online social networks. Even as ABAC and ReBAC continue to evolve, there are conflicting claims in the literature regarding their comparison. It has been argued that ABAC can subsume ReBAC since attributes can encode relationships. Conversely there are claims that the multilevel (or indirect) relations of ReBAC bring fundamentally new capabilities. So far there is no rigorous comparative study of ABAC vis a vis ReBAC. This paper presents a comparative analysis of ABAC and ReBAC, and shows how various ReBAC features can be realized with different types of ABAC. We first identify several attribute types such as entity/non-entity and structured attributes that significantly influence ABAC or ReBAC expressiveness. We then develop a family of ReBAC models and a separate family of ABAC models based on the identified attribute types, with the goal of comparing the expressive power of these two model families. Further, we identify different dynamics of the models that are crucial for model comparison. We also consider different solutions for representing multilevel relationships with attributes. Finally, the ABAC and ReBAC model families are compared in terms of relative expressiveness and performance implications.

Attribute-Based Access Control (ABAC) has received significant attention in recent years, although the concept has been around for over two decades now. Many ABAC models, with different variations, have been proposed and formalized. Besides basic ABAC models, there are models designed with additional capabilities such as group attributes, group and attribute hierarchies and so on. Hierarchical relationship among groups and attributes enhances access control flexibility and facilitates attribute management and administration. However, implementation and demonstration of ABAC models in real-world applications is still lacking. In this paper, we present a restricted HGABAC (rHGABAC) model with user and object groups and group hierarchy. We then introduce attribute hierarchies in this model. We also present an authorization architecture for implementing rHGABAC utilizing the NIST Policy Machine (PM). PM allows to define attribute-based access control policies, however, the attributes in PM are different in nature than attributes in typical ABAC models as name-value pairs. We identify a policy configuration mechanism for our proposed model employing PM capabilities, and demonstrate use cases and their configuration and implementation in PM using our authorization architecture.

In this paper, we introduce the concept of transforming attribute-value assignments from one set to another set. We specify two types of transformations–-attribute reduction and attribute expansion. We distinguish policy attributes from non-policy attributes in that policy attributes are used in authorization policies whereas the latter are not. Attribute reduction is a process of contracting a large set of assignments of non-policy attributes into a possibly smaller set of policy attribute-value assignments. This process is useful for abstracting attributes that are too specific for particular types of objects or users, designing modular authorization policies, and modeling hierarchical policies. On the other hand, attribute expansion is a process of performing a large set of attribute-value assignments to users or objects from a possibly smaller set of assignments. We define a language for specifying mapping for the transformation process. We also identify and discuss various issues that stem from the transformation process.