Anonymous access is an effective method for preserving privacy in access control. This study assumes that anonymous access control requires both frameworks and policies. Numerous solutions have been proposed for anonymous access at the framework level. In this study, these solutions are analyzed and quantified using a unified attribute-based access control (ABAC) anonymous access reference framework. Anonymous access at the framework level is the first line of defense, and inappropriate policies may undermine subject anonymity. An anonymity metric is proposed at the policy level to prevent authorization authority from re-identification using specific attributes and policies. The anonymity metric evaluates the risk of re-identifying a subject due to inappropriate access requests, as well as subject attribute assignment schemes and policies. This study is the first to focus on anonymity at the policy level in ABAC. Furthermore, a formal definition of anonymity suitable for ABAC is proposed. The feasibility of the proposed anonymity metric is verified through simulations.

Rapid development of smart homes in recent years has led to the production of an increasing number of smart devices that meet people’s daily needs. However, these smart devices may belong to different vendors and provide different functions and services, making it difficult to apply a centralized solution to a smart home system. Although blockchain has the potential to address the potential problems of smart homes because of its features such as nontampering, decentralization, and security, scalability remains a key challenge when integrating blockchain and smart homes, which is mainly reflected in the horizontal expansion, throughput and latency of the system. To address this challenge, Communitychain–a new scalable blockchain architecture suitable for smart home systems composing heterogeneous devices–is proposed in this study. A community model based on sharding that enables the architecture to adapt to an increase in the number of nodes is designed, which includes new miner nodes and leader node selection algorithms. Efficient cross-shard routing and sideBlock schemes are adopted to improve the throughput and latency and enhance the scalability of the system. Furthermore, lightweight authorization and authentication processes running in each community ensure secure access to device resources. The experimental results indicate that the proposed blockchain architecture can effectively improve the scalability of blockchain-based smart homes and adapt well to the system dynamics.

The Bell-LaPadula (BLP) model is a widely used access control model for the multilevel security system. The researchers proposed many modified BLP models to express privileges that cannot be expressed by the BLP model. However, these models are not compatible with the BLP model, leading to the transportation cost-prohibitive and difficult to be practically applied. In this article, an improved BLP model incorporated the break the glass (BTG) mechanism is proposed to overcome the limitations of the standard BLP and other modified BLP models. The improved model inherits some of the advantages of BTG, such as policy dynamic modification and fine-grained access control, which gives it wide availability. Additionally, in the implementation, BTG is used as an independent function attached to the original BLP; the proposed BLP model can be easily implemented in systems where BLP models have been implemented. The results of the analysis and simulations showed that the proposed BLP model improves the ability of expressing policy of BLP and achieves fine-grained access control without compromise in security. Compared with other modified BLP models, the proposed BLP model could express policy more effectively and is compatible with the original BLP model.

As a widely recognized policy language of access control, the eXtensible Access Control Markup Language (XACML) is widely used with its fine-grained and easy-to-read. With the application of XACML, researchers find that the XACML based policy evaluation and policy management methods can no longer meet the current large-scale requests for efficient access and dynamic management requirements. To improve the performance of policy evaluation based on XACML, we propose a policy evaluation method based on the matching tree to search policy efficiently and avoid the extra consumption of invalid policy participation. Furthermore, we propose a policy dynamic management method based on the matching tree to reduce the scale of the policy to be disabled for management, by adding locks in the tree node and the information mapping table. Through theoretical derivation and the factors that may affect its evaluation performance, we verify the improvement of evaluation efficiency. The simulation also shows the improvement of the evaluation engine based on the matching tree compared with OuenAz.