Building access control policy model for privacy preserving and testing policy conflicting problems

This paper proposes a purpose-based access control model in distributed computing environment for privacy preserving policies and mechanisms, and describes algorithms for policy conflicting problems. The mechanism enforces access policy to data containing personally identifiable information. The key component is purpose involved access control models for expressing highly complex privacy-related policies with various features. A policy refers to an access right that a subject can have on an object, based on attribute predicates, obligation actions, and system conditions. Policy conflicting problems may arise when new access policies are generated that are possible to be conflicted to existing policies. As a result of the policy conflicts, private information cannot be well protected. The structure of purpose involved access control policy is studied, and efficient conflict-checking algorithms are developed and implemented. Finally a discussion of our work in comparison with other related work such as EPAL is presented.     

A model for secure multimedia document database system in a distributed environment

The Internet provides a universal platform for large-scale distribution of information and supports inter-organizational services, system integration, and collaboration. Use of multimedia documents for dissemination and sharing of massive amounts of information is becoming a common practice for Internet-based applications and enterprises. With the rapid proliferation of multimedia data management technologies over the Internet, there is growing concern about security and privacy of information. Composing multimedia documents in a distributed heterogeneous environment involves integrating media objects from multiple security domains that may employ different access control policies for media objects. In this paper, we present a security model for distributed document management system that allows creation, storage, indexing, and presentation of secure multimedia documents. The model is based on a time augmented Petri-net and provides a flexible, multilevel access control mechanism that allows clearance-based access to different levels of information in a document. In addition, the model provides detailed multimedia synchronization requirements including deterministic and non-deterministic temporal relations and incomplete timing information among media objects.     

多域环境下安全互操作研究进展

多域安全互操作是通过认证机制、访问控制机制和审计机制来实现多个分布、异构、自治区域间安全的资源共享和信息交互的过程.系统介绍了这一新型研究领域的理论基础和应用现状,从解决访问控制安全和域间策略冲突的角度,对域间角色转换技术、基于信任管理、基于PKI和基于时间限制等方向的多项研究成果和关键技术进行分析和点评,重点探讨了多域环境下各自治域间策略集成算法的建模和实现,最后针对目前研究工作中存在的问题,对该领域未来的发展方向和趋势做出展望.     

时间约束的角色访问控制系统的设计与实现*

设计并实现了一种基于时间约束的角色访问控制系统,描述了系统中的时间约束,分析了在引入时间后系统中存在的冲突,给出了解决冲突的策略以及各功能模块的实现.     

Model-driven specification and enforcement of RBAC break-glass policies for process-aware information systems

ContextIn many organizational environments critical tasks exist which – in exceptional cases such as an emergency – must be performed by a subject although he/she is usually not authorized to perform these tasks. Break-glass policies have been introduced as a sophisticated exception handling mechanism to resolve such situations. They enable certain subjects to break or override the standard access control policies of an information system in a controlled manner.ObjectiveIn the context of business process modeling a number of approaches exist that allow for the formal specification and modeling of process-related access control concepts. However, corresponding support for break-glass policies is still missing. In this paper, we aim at specifying a break-glass extension for process-related role-based access control (RBAC) models.MethodWe use model-driven development (MDD) techniques to provide an integrated, tool-supported approach for the definition and enforcement of break-glass policies in process-aware information systems. In particular, we provide modeling support on the computation independent model (CIM) layer as well as on the platform independent model (PIM) and platform specific model (PSM) layers.ResultsOur approach is generic in the sense that it can be used to extend process-aware information systems or process modeling languages with support for process-related RBAC and corresponding break-glass policies. Based on the formal CIM layer metamodel, we present a UML extension on the PIM layer that allows for the integrated modeling of processes and process-related break-glass policies via extended UML Activity diagrams. We evaluated our approach in a case study on real-world processes. Moreover, we implemented our approach at the PSM layer as an extension to the BusinessActivity library and runtime engine.ConclusionOur integrated modeling approach for process-related break-glass policies allows for specifying break-glass rules in process-aware information systems.     

Access control management for ubiquitous computing

The purpose of ubiquitous computing is anywhere and anytime access to information within computing infrastructures that is blended into a background and no longer be reminded. This ubiquitous computing poses new security challenges while the information can be accessed at anywhere and anytime because it may be applied by criminal users. Additionally, the information may contain private information that cannot be shared by all user communities. Several approaches are developed to protect information for pervasive environments against malicious users. However, ad hoc mechanisms or protocols are typically added in the approaches by compromising disorganized policies or additional components to protect from unauthorized access.In this paper, we present a usage control model to protect services and devices in ubiquitous computing environments, which allows the access restrictions directly on services and object documents. The model not only supports complex constraints for pervasive computing, such as services, devices and data types but also provides a mechanism to build rich reuse relationships between models and objects. Finally, comparisons with related works are analysed.     

Role-Based Access Control in a Data Grid Using the Storage Resource Broker and Shibboleth

In this paper, we propose a role-based access control (RBAC) system for data resources in the Storage Resource Broker (SRB). The SRB is a Data Grid management system, which can integrate heterogeneous data resources of virtual organizations (VOs). The SRB stores the access control information of individual users in the Metadata Catalog (MCAT) database. However, because of the specific MCAT schema structure, this information can only be used by the SRB applications. If VOs also have many non-SRB applications, each with its own storage format for user access control information, it creates a scalability problem with regard to administration. To solve this problem, we developed a RBAC system with Shibboleth, which is an attribute authorization service currently being used in many Grid environments. Thus, the administration overhead is reduced because the role privileges of individual users are now managed by Shibboleth, not by MCAT or applications. In addition, access control policies need to be specified and managed across multiple VOs. For the specification of access control policies, we used the Core and Hierarchical RBAC profile of the eXtensible Access Control Markup Language (XACML); and for distributed administration of those policies, we used the Object, Metadata and Artifacts Registry (OMAR). OMAR is based on the e-business eXtensible Markup Language (ebXML) registry specifications developed to achieve interoperable registries and repositories. Our RBAC system provides scalable and fine-grain access control and allows privacy protection. Performance analysis shows that our system adds only a small overhead to the existing security infrastructure of the SRB.     

网络安全策略冲突分类及自动检测与恢复

在分析网络安全策略冲突研究现状的基础上,针对策略冲突分类不完善及现在安全策略冲突检测方法的不足,指出由于网络策略之间的规则依赖语义和规则相互作用,一个成功的网络安全系统配置需要全面分析所有网络安全设备的策略配置以避免策略冲突和矛盾.本文首先描述了过滤规则之间所有可能的关系,然后对基于过滤的网络安全策略中的冲突进行全面分类,接着通过实验指出即使是专家系统管理员,产生这种冲突的可能性也很高,并提出了内部和外部访问列表策略冲突的自动检测与恢复模型来识别和矫正这些冲突,最后讨论了今后研究的方向.     

An analysis of expressiveness and design issues for the generalized temporal role-based access control model

The generalized temporal role-based access control (GTRBAC) model provides a comprehensive set of temporal constraint expressions which can facilitate the specification of fine-grained time-based access control policies. However, the issue of the expressiveness and usability of this model has not been previously investigated. In this paper, we present an analysis of the expressiveness of the constructs provided by this model and illustrate that its constraints-set is not minimal. We show that there is a subset of GTRBAC constraints that is sufficient to express all the access constraints that can be expressed using the full set. We also illustrate that a nonminimal GTRBAC constraint set can provide better flexibility and lower complexity of constraint representation. Based on our analysis, a set of design guidelines for the development of GTRBAC-based security administration is presented.     

Secure interoperation in a multidomain environment employing RBAC policies

Multidomain application environments where distributed multiple organizations interoperate with each other are becoming a reality as witnessed by emerging Internet-based enterprise applications. Composition of a global coherent security policy that governs information and resource accesses in such environments is a challenging problem. In this paper, we propose a policy integration framework for merging heterogeneous role-based access control (RBAC) policies of multiple domains into a global access control policy. A key challenge in composition of this policy is the resolution of conflicts that may arise among the RBAC policies of individual domains. We propose an integer programming (IP)-based approach for optimal resolution of such conflicts. The optimality criterion is to maximize interdomain role accesses without exceeding the autonomy losses beyond the acceptable limit.     

Cryptographically-enforced hierarchical access control with multiple keys

Hierarchical access control policies, in which users and objects are associated with nodes in a hierarchy, can be enforced using cryptographic mechanisms. Protected data is encrypted and authorized users are given the appropriate keys. Lazy re-encryption techniques and temporal hierarchical access control policies require that multiple keys may be associated with a node in the hierarchy. In this paper, we introduce the notion of a multi-key assignment scheme to address this requirement. We define bounded, unbounded, synchronous, and asynchronous schemes. We demonstrate that bounded, synchronous schemes provide an alternative to temporal key assignment schemes in the literature, and that unbounded asynchronous schemes provide the desired support for lazy re-encryption.     

A conditional purpose-based access control model with dynamic roles

This paper presents a model for privacy preserving access control which is based on variety of purposes. Conditional purpose is applied along with allowed purpose and prohibited purpose in the model. It allows users using some data for certain purpose with conditions. The structure of conditional purpose-based access control model is defined and investigated through dynamic roles. Access purpose is verified in a dynamic behavior, based on subject attributes, context attributes and authorization policies. Intended purposes are dynamically associated with the requested data object during the access decision. An algorithm is developed to achieve the compliance computation between access purposes and intended purposes and is illustrated with Role-based access control (RBAC) in a dynamic manner to support conditional purpose-based access control. According to this model, more information from data providers can be extracted while at the same time assuring privacy that maximizes the usability of consumers’ data. It extends traditional access control models to a further coverage of privacy preserving in data mining atmosphere. The structure helps enterprises to circulate clear privacy promise, to collect and manage user preferences and consent.     

Verification and enforcement of access control policies

Access control mechanisms protect critical resources of systems from unauthorized access. In a policy-based management approach, administrators define user privileges as rules that determine the conditions and the extent of users’ access rights. As rules become more complex, analytical skills are required to identify conflicts and interactions within the rules that comprise a system policy—especially when rules are stateful and depend on event histories. Without adequate tool support such an analysis is error-prone and expensive. In consequence, many policy specifications are inconsistent or conflicting that render the system insecure. The security of the system, however, does not only depend on the correct specification of the security policy, but in a large part also on the correct interpretation of those rules by the system’s enforcement mechanism. In this paper, we show how policy rules can be formalized in Fusion Logic, a temporal logic for the specification of behavior of systems. A symbolic decision procedure for Fusion Logic based on Binary Decision Diagrams (BDDs) is provided and we introduce a novel technique for the construction of enforcement mechanisms of access control policy rules that uses a BDD encoded enforcement automaton based on input traces which reflect state changes in the system. We provide examples of verification of policy rules, such as absence of conflicts, and dynamic separation of duty and of the enforcement of policies using our prototype implementation (FLCheck) for which we detail the underlying theory.     

A practical mandatory access control model for XML databases

A practical mandatory access control (MAC) model for XML databases is presented in this paper. The label type and label access policy can be defined according to the requirements of different applications. In order to preserve the integrity of data in XML databases, a constraint between a read-access rule and a write-access rule in label access policy is introduced. Rules for label assignment and propagation are presented to alleviate the workload of label assignments. Furthermore, a solution for resolving conflicts in label assignments is proposed. Rules for update-related operations, rules for exceptional privileges of ordinary users and the administrator are also proposed to preserve the security of operations in XML databases. The MAC model, we proposed in this study, has been implemented in an XML database. Test results demonstrated that our approach provides rational and scalable performance.     

Specifying and enforcing access control policies for XML document sources

The Web is becoming the main information dissemination means in private and public organizations. As a consequence, several applications at both internet and intranet level need mechanisms to support a selective access to data available over the Web. In this context, developing an access control model, and related mechanisms, in terms of XML (eXtensible Markup Language) is an important step, because XML is increasingly used as the language for representing information exchanged over the Web. In this paper, we propose access control policies and an associated model for XML documents, addressing peculiar protection requirements posed by XML. A first requirement is that varying protection granularity levels should be supported to guarantee a differentiated protection of document contents. A second requirement arises from the fact that XML documents do not always conform to a predefined document type. To cope with these requirements, the proposed model supports varying protection granularity levels, ranging from a set of documents, to a single document or specific document portion(s). Moreover, it allows the Security Administrator to choose different policies for documents not covered or only partially covered by the existing access control policies for document types. An access control mechanism for the enforcement of the proposed model is finally described. This revised version was published online in August 2006 with corrections to the Cover Date.     

Selective and authentic third-party distribution of XML documents

Third-party architectures for data publishing over the Internet today are receiving growing attention, due to their scalability properties and to the ability of efficiently managing large number of subjects and great amount of data. In a third-party architecture, there is a distinction between the Owner and the Publisher of information. The Owner is the producer of information, whereas Publishers are responsible for managing (a portion of) the Owner information and for answering subject queries. A relevant issue in this architecture is how the Owner can ensure a secure and selective publishing of its data, even if the data are managed by a third-party, which can prune some of the nodes of the original document on the basis of subject queries and access control policies. An approach can be that of requiring the Publisher to be trusted with regard to the considered security properties. However, the serious drawback of this solution is that large Web-based systems cannot be easily verified to be secure and can be easily penetrated. For these reasons, we propose an alternative approach, based on the use of digital signature techniques, which does not require the Publisher to be trusted. The security properties we consider are authenticity and completeness of a query response, where completeness is intended with regard to the access control policies stated by the information Owner. In particular, we show that, by embedding in the query response one digital signature generated by the Owner and some hash values, a subject is able to locally verify the authenticity of a query response. Moreover, we present an approach that, for a wide range of queries, allows a subject to verify the completeness of query results.     

Reasoning about fuzzy temporal information from the web: towards retrieval of historical events

When searching for information about historical events, queries are naturally formulated using temporal constraints. However, the structured temporal information needed to support such constraints is usually not available to information retrieval systems. Furthermore, the temporal boundaries of most historical events are inherently ill-defined, calling for suitable extensions of classical temporal reasoning frameworks. In this paper, we propose a framework based on a fuzzification of Allen’s Interval Algebra to cope with these issues. By using simple heuristic techniques to extract temporal information from web documents, we initially focus more on recall than on precision, relying on the subsequent application of a fuzzy temporal reasoner to improve the reliability of the extracted information, and to deal with conflicts that arise because of the vagueness of events. Experimental results indicate that a consistent and reliable knowledge base of fuzzy temporal relations can thus be obtained, which effectively allows us to target temporally constrained retrieval tasks.     

Security analysis of GTRBAC and its variants using model checking

Security analysis is a formal verification technique to ascertain certain desirable guarantees on the access control policy specification. Given a set of access control policies, a general safety requirement in such a system is to determine whether a desirable property is satisfied in all the reachable states. Such an analysis calls for the use of formal verification techniques. While formal analysis on traditional Role Based Access Control (RBAC) has been done to some extent, recent extensions to RBAC lack such an analysis. In this paper, we consider the temporal RBAC extensions and propose a formal technique using timed automata to perform security analysis by analyzing both safety and liveness properties. Using safety properties one ensures that something bad never happens while liveness properties show that some good state is also achieved. GTRBAC is a well accepted generalized temporal RBAC model which can handle a wide range of temporal constraints while specifying different access control policies. Analysis of such a model involves a process of mapping a GTRBAC based system into a state transition system. Different reduction rules are proposed to simplify the modeling process depending upon the constraints supported by the system. The effect of different constraints on the modeling process is also studied.