XACML Policies Research Articles

Introduction to the Special Issue on Reliability and Security of e-Health Information Systems

With the increasing population and aging society in several countries, healthcare providers aim to enhance the quality of the healthcare services while balancing the risk mitigation and service cost. Therefore, several new information technologies and innovative communication methodologies have evolved to improve the healthcare sector. ICT-based technologies help in decreasing the healthcare system overhead and increasing the quality of healthcare services. These technologies may include biosensors, computer aided diagnosis, Wireless Body Sensor Network (WBSN), mobile health, Radio Frequency Identification (RFID), cloud computing, communication protocols, electronic medical records, big data, and internet of things (IoT). Therefore, the complexity of healthcare systems has increased dramatically during the last two decades. Despite having several approaches developed for testing and verification of healthcare systems, ICT related medical incidents that led into losses of money, time, reputation, and in certain cases, lives, still happen frequently. It is believed that healthcare systems do not get enough testing and verification before being put into use, even though they are considered safety critical systems. This is due to the high cost of testing, short time to marker, and the lack of proper testing and verification techniques in the literature. Design errors, system usage problems, design reliability issues, compliance Issues, system failure and vulnerabilities in eHealth care system can lead to critical conditions or even death. The special issue publishes three papers that extended from papers presented at IEEE Healthcom 2015, in addition to two new submitted papers. The first paper in this issue by Pervez et al. titled Improvement Strategies for Device Interoperability Middleware (DIM) using Formal Reliability analysis, where the authors used probabilistic model checker PRISM for analyzing Device Interoperability Middleware (DIM).The second paper by Bhardwaj and Prasad is titled PRAVAH: Parameterised Information Flow Control in e-Health.The authors addressed the problem of enforcing information flow control (IFC) in hospital domains in eHealth systems using a parameterised lattice-based IFC framework called PRAVAH. The third paper by Ayache et al. is titled Analysis and verification of XACML policies in a medical cloud environment. The authors presented a Cloud Policy Verification Service (CPVS) for the analysis and the verification of access control policies specified using XACML. The fourth paper by Sadki and Bakkali is titled Resolving conflicting privacy policies in m-health based on prioritization. The authors presented resent an approach to resolve the problem of conflicting privacy policies in mobile health environments using AHP (Analytic Hierarchy Process) prioritization technique and reputation mechanism. The fifth paper by Gawanmeh et al. is titled Formal Analysis of a Microfluidic Device for Blood Cell Separation. The authors used formal analysis in order to formalize and validate the movement of blood cells in a microdevice under different forces for the purpose of cell separation. We would like to thank the editorial board of SCPE for the efforts they made to make this special issue, and all the reviewers for their efforts and feedback.

Unifying the Access Control Mechanism for the Enterprises Using XACML Policy Levels

Unifying the Access Control Mechanism for the Enterprises Using XACML Policy Levels

Proposing hierarchy-similarity based access control framework: A multilevel Electronic Health Record data sharing approach for interoperable environment

Interoperability in healthcare environment deals with sharing of patient’s Electronic Health Records (EHR) with fellow professionals in inter as well as intra departments or organizations. Healthcare environment experiences frequent shifting of doctors, paramedical staff in inter as well as intra departments or hospitals. The system exhibits dynamic attributes of users and resources managed through access control policies defined for that environment. Rules obtained on merging of such policies often generate policy-conflicts thereby resulting in undue data leakages to unintended users. This paper proposes an access control framework that applies a Hierarchy Similarity Analyzer (HSA) on the policies need to be merged. It calculates a Security_Level (SL) and assigns it to the users sharing data. The SL determines the authorized amount of data that can be shared on successful collaboration of two policies. The proposed framework allows integration of independent policies and identifies the possible policy-conflicts arising due to attribute disparities in defined rules. The framework is implemented on XACML policies and compared with other access models designed using centralized and decentralized approaches. Conditional constraints and properties are defined that generate policy-conflicts as prevalent in the policies.

Detecting Incorrect Uses of Combining Algorithms in XACML 3.0 Policies

With the increasing complexity of software, new access control methods have emerged to deal with attribute-based authorization. As a standard language for specifying attribute-based access control policies, XACML offers a number of rule and policy combining algorithms to meet different needs of policy composition. Due to their variety and complexity, however, it is not uncommon to apply combining algorithms incorrectly, which can lead to unauthorized access or denial of service. To solve this problem, this paper presents a fault-based testing approach for revealing incorrect combining algorithms in XACML 3.0 policies. The theoretical foundation of this approach relies on the formalization of semantic differences between rule combining algorithms and between policy combining algorithms. It allows the use of a constraint solver for generating queries to which a given policy produces different responses than its combining algorithm-based mutants. Such queries can determine whether or not the given combining algorithm is used correctly. Our empirical studies using various XACML policies have demonstrated that our approach is effective.

Fine-Grained Access Control via XACML Policy Optimization in Cloud Computing

One primary challenge of enforcing access control in cloud computing is how to ensure access with high efficiency while preserving data security. This paper proposes a fine-grained access control method for cloud resources. The basic idea is to use XACML as access control language and to optimize policies by data fragmentation and policy refinement algorithms. Through data fragmentation, the accessible resources are divided into disjoint data blocks, and each of them will be combined with a set of policy rules. This helps to refine the policy and to avoid data leakage caused by rule conflicting on the resource intersections. Finally, the disjoint data blocks and the optimized policy are distributed in the three-layered cloud, and the decision to a request is made by rule matching on a specific resource rather than traversing the whole policy rules. Experiments show that our proposal enjoys higher efficiency in cloud-based access control.

From model-driven specification to design-level set-based analysis of XACML policies

With lot of hype surrounding policy-based computing, XACML (eXtensible Access Control Markup Language) has become the widely used de facto standard for managing access to open and distributed service-based environments like Web services. However, like any other policy language, XACML has complex syntax, which makes the policies specification process both time consuming and error prone, especially with large size policies that govern complex systems. Moreover, with the diversity of rules and conditions, hidden conflicts, redundancies and access flaws are more likely to arise, which expose Web services to security breaches at runtime. This paper proposes a UML profile that allows systematic model-driven specification of XACML policies to resolve the complexity of policies designation. Based on mathematical sets that explore the rules meanings, the paper provides also a design-level analysis to detect anomalies in the specified policies, prior to their enforcement in the system. A real life case study demonstrates the feasibility and efficiency of the proposition.

XACML Policy Evaluation with Dynamic Context Handling

Some fairly recent research has focused on providing XACML-based solutions for dynamic privacy policy management. In this regard, a number of works have provided enhancements to the performance of XACML policy enforcement point (PEP) component, but very few have focused on enhancing the accuracy of that component. This paper improves the accuracy of an XACML PEP by filling some gaps in the existing works. In particular, dynamically incorporating user access context into the privacy policy decision, and its enforcement. We provide an XACML-based implementation of a dynamic privacy policy management framework and an evaluation of the applicability of our system in comparison to some of the existing approaches.

Building an Islamic financial information system based on policy managements

For many banks and customers in the Middle East and Islamic world, the availability and the ability to apply Islamic Shariah rules on financial activities is very important. In some cases, business and technical barriers can limit the ability to apply and offer financial services that are implemented according to Shariah rules.In this paper, we discuss enforcing Shariah rules from information technology viewpoint and show how such rules can be implemented and enforced in a financial establishment. Security authorization standard XACML is extended to consider Shariah rules. In this research XACML architecture, that is used and applied in many tools and system architectures, is used to enforce Shariah rules in the banking sector rather than its original goal of enforcing security rules where policy management systems such as XACML are usually used.We developed a model based on XACML policy management to show how an Islamic financial information system can be used to make decisions for day to day bank activities. Such a system is required by all Islamic banks around the world. Currently, most Islamic banks use advisory boards to provide opinions on general activities. The gap between those high level general rules and decision for each customer business process is to be filled by Islamic financial information systems.The flexible design of the architecture can also be effective where rules can be screened and revisited often without the need to restructure the authorization system implemented. Authorization rules described here are not necessarily the perfect reflection of Shariah opinions. They are only shown as a proof of concept and a demonstration of how such rules can be written and implemented.

Semantics-based approach for detecting flaws, conflicts and redundancies in XACML policies

XACML (eXtensible Access Control Markup Language) policies, which are widely adopted for defining and controlling dynamic access among Web/cloud services, are becoming more complex in order to handle the significant growth in communication and cooperation between individuals and composed services. However, the large size and complexity of these policies raise many concerns related to their correctness in terms of flaws, conflicts and redundancies presence. This paper addresses this problem through introducing a novel set and semantics based scheme that provides accurate and efficient analysis of XACML policies. First, our approach resolves the complexity of policies by elaborating an intermediate set-based representation to which the elements of XACML are automatically converted. Second, it allows to detect flaws, conflicts and redundancies between rules by offering new mechanisms to analyze the meaning of policy rules through semantics verification by inference rule structure and deductive logic. All the approach components and algorithms realizing the proposed analysis semantics have been implemented in one development framework. Experiments carried out on synthetic and real-life XACML policies explore the relevance of our analysis algorithms with acceptable overhead. Please visit http://www.azzammourad.org/#projects to download the framework.

Decision Diagrams for XACML Policy Evaluation and Management

One of the primary challenges to apply the XACML access control policy language in applications is the performance problem of policy evaluation engines, particularly when they experience a great number of policies. Some existing works attempted to solve this problem, but only for some particular use-cases: either supporting simple policies with equality comparisons or predefined attribute values. Due to the lack of carefully checking the XACML model, they did not have original policy evaluation semantics. Therefore, they cannot handle errors containing indeterminate decisions, or ignore the critical attribute setting that leads to potential missing attribute attacks. In this paper, we build up the XACML logical model and propose a decision diagram approach using the data interval partition aggregation. It can parse and transform complex logical expressions in policies into decision tree structures, which efficiently improve the policy evaluation performance. Our approach can also be applied to solve other policy management problems such as policy redundancy detection, policy testings and comparisons, or authorization reverse queries.

SBA-XACML: Set-based approach providing efficient policy decision process for accessing Web services

Policy-based computing is taking an increasing role in providing real-time decisions and governing the systematic interaction among distributed Web services. XACML (eXtensible Access Control Markup Language) has been known as the de facto standard widely used by many vendors for specifying access and context-aware policies. Accordingly, the size and complexity of XACML policies are significantly growing to cope with the evolution of web-based applications and services. This growth raised many concerns related to the efficiency of real-time decision process (i.e. policy evaluation) and the correctness of complex policies. This paper is addressing these concerns through the elaboration of SBA-XACML, a novel Set-Based Algebra (i.e. SBA) scheme that provides efficient evaluation of XACML policies. Our approach constitutes of elaborating (1) a set-based language that covers all the XACML components and establish an intermediate layer to which policies are automatically converted, and (2) a semantics-based policy evaluation that provides better performance compared to the industrial standard Sun Policy Decision Point (PDP) and its corresponding ameliorations. Experiments have been conducted on real-life and synthetic XACML policies in order to demonstrate the efficiency, relevance and scalability of our proposition. The experimental results explore that SBA-XACML evaluation of large and small sizes policies offers better performance than the current approaches, by a factor ranging between 2.4 and 15 times faster depending on policy size.

Approaches for testing and evaluation of XACML Policies

Security services are provided through: The applications, operating systems, databases, and the network. There are many proposals to use policies to define, implement and evaluate security services. We discussed a full test automation framework to test XACML based policies. Using policies as input the developed tool can generate test cases based on the policy and the general XACML model. We evaluated a large dataset of policy implementations. The collection includes more than 200 test cases that represent instances of policies. Policies are executed and verified, using requests and responses generated for each instance of policies. WSO2 platform is used to perform different testing activities on evaluated policies.

SECURE DATA STORAGE AND RETRIEVAL IN THE CLOUD

With the advent of the World Wide Web and the emergence of e-commerce applications and social networks, organizations across the world generate a large amount of data daily. This data would be more useful to cooperating organizations if they were able to share their data. Two major obstacles to this process of data sharing are providing a common storage space and secure access to the shared data. In this paper we address these issues by combining cloud computing technologies such as Hive and Hadoop with XACML policy based security mechanisms that provide fine-grained access to resources. HIVE supports queries expressed in SQL-like language called HiveQL which are compiled into MR jobs that are executed on Hadoop. We further present a web-based application that uses this combination and allows collaborating organizations to securely store and retrieve large amounts of data.

Semantic-Based Access Control for Data Resources in Open Grid Services Architecture

This paper proposes a semantic-based access control system for the data resources in the Open Grid Services Architecture - Data Access and Integration (OGSA-DAI). OGSA-DAI is a widely used middleware for integrating data resources in Grids. However, the identity-based access control in OGSA-DAI causes substantial overhead for the resource providers in virtual organizations (VOs), because the access control information of individual users has to be maintained by each resource provider. To solve these problems, the authors propose a semantic-based access control system using Shibboleth and ontology. Shibboleth, an attribute authorization service, is used to manage the user attributes, and the Web Ontology Language (OWL) is used to represent the ontology of the data resources and users. By using ontology, VOs can resolve the differences in their terminologies and specify access control policies based on concepts and user roles, instead of individual resources and user identities. As a result, the administration overhead of the resource providers is reduced considerably. In addition, the eXtensible Access Control Markup Language (XACML) is used to specify the access control policies uniformly across multiple VOs. The authors also developed an XACML policy administration tool that allows the administrators to create, update, and manage XACML policies. The performance analysis shows that our proposed system adds only a small overhead to the existing security mechanism of OGSA-DAI.

MobiDyC: Private Mobile-based Health Data Sharing through Dynamic Context Handling

With the adoption of mobile healthcare applications and the success of cloud service models, we propose a privacy management framework for mobile health care applications with support for dynamic privacy management of health data sharing. Our solution extends the XACML policy language by incorporating user access context into the privacy policy rule enforcement. We provide an implementation of our approach that builds on top of the Google App Engine cloud platform. We also provide a preliminary evaluation that indicates that the overhead incurred by our approach is minimal.

A Similarity Measure for Comparing XACML Policies

Assessing similarity of policies is crucial in a variety of scenarios, such as finding the cloud service providers which satisfy users' privacy concerns, or finding collaborators which have matching security and privacy settings. Existing approaches to policy similarity analysis are mainly based on logical reasoning and Boolean function comparison. Such approaches are computationally expensive and do not scale well for large heterogeneous distributed environments (like the cloud). In this paper, we propose a policy similarity measure as a lightweight ranking approach to help one party quickly locate parties with potentially similar policies. In particular, given a policy P, the similarity measure assigns a ranking (similarity score) to each policy compared with P. We formally define the measure by taking into account various factors and prove several important properties of the measure. Our extensive experimental study demonstrates the efficiency and practical value of our approach.

Automated testing of eXtensible Access Control Markup Language‐based access control systems

The trustworthiness of sensitive data needs to be guaranteed and testing is a common activity among privacy protection solutions, even if quite expensive. Accesses to data and resources are ruled by the policy decision point (PDP), which relies on the eXtensible Access Control Markup Language (XACML) standard language for specifying access rights. In this study, the authors propose a testing strategy for automatically deriving test requests from a XACML policy and describe their pilot experience in test automation using this strategy. Considering a real two-level PDP implemented for health data security, the authors compare the effectiveness of the test plan automatically derived with the one derived by a standard manual testing process.

The logic of XACML

We study the international standard XACML 3.0 for describing security access control policies in a compositional way. Our main contributions are (i) to derive a logic that precisely captures the intentions of the standard, (ii) to formally define a semantics for the XACML 3.0 component evaluation, and (iii) to define a semantics for the XACML 3.0 standard combining operators. To guard against modeling artefacts we provide an alternative lattice based way of characterizing the policy combining operators and we formally prove the equivalence of these approaches thereby increasing our faith in either one. We then discuss several ways of extending XACML: one direction is to extend XACML with new combining operators, and another direction is to incorporate the notion of conflict into XACML. We conclude by discussing the possibility of analysing XACML policies for gaps and conflicts.

Using AOP-based enforcement of prioritised XACML policies for location privacy

Location-based services have become more and more popular over the last years and allow the tracking of persons and goods. Users of these services often have little control over their private data as it is accessed, processed and stored. This paper presents a privacy enforcement concept that combines a sticky-policy approach with an aspect-oriented programming-based reference monitor. Furthermore, we introduce prioritised policies which allow users to define their own access rules without accidentally generating inconsistent rule sets. For the implementation of this concept, we propose a new XACML combining algorithm, the priority policy combining algorithm. We demonstrate the feasibility and ease-of-use of our concept with the example of a theme-park location service.

New XACML-AspectBPEL approach for composite web services security

Web services technology is the latest evolution in distributed computing. With all of the advantages of web services, one of the main hurdles remains security in composite web services. In this paper, we tackle this problem through a new approach towards the integration of security into the BPEL Business Process Execution Language process of composite web services. Our approach allows specifying the XACML eXtensible Access Control Markup Language policies that determine join points in a BPEL process where security is needed. Subsequently, BPEL flows with the needed security are generated into AspectBPEL security aspects to be weaved in the aforementioned process. The main contributions of our approach are: a describing dynamic security policies using a standard language XACML, b generating automatically the AspectBPEL aspects of the XACML policies and c separating the business and security concerns of composite web services, hence developing and updating them separately at the BPEL side.