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.     

Management of access control policies for XML document sources

The development of suitable mechanisms for securing XML documents is becoming an urgent need since XML is evolving into a standard for data representation and exchange over the Web. To answer this need, we have designed Author-X [1, 3], a Java-based system specifically conceived for the protection of XML documents. Distinguishing features of the access control model of Author-X are the support for a wide range of protection granularity levels and for subject credentials. Another key characteristic of Author-X is the enforcement of different access control strategies for document release: besides the traditional, on user demand, mode of access control, Author-X also supports push distribution, for document dissemination. Managing an access control system based on such a flexible and expressive model requires the design and implementation of suitable administration tools to help the Security Administrator in efficiently performing administrative operations related to access control policies management. In this paper, we present the strategies and related algorithms we have devised for policy management in Author-X , with particular emphasis on information push support. In the paper, besides presenting the algorithms and the related data structures, we provide a complexity study of the proposed algorithms. Additionally, we describe the implementation of the proposed algorithms in the framework of Author-X .     

XML-based specification for Web services document security

The Internet and related technologies have seen tremendous growth in distributed applications such as medicine, education, e-commerce, and digital libraries. As demand increases for online content and integrated, automated services, various applications employ Web services technology for document exchange among data repositories. Web services provide a mechanism to expose data and functionality using standard protocols, and hence to integrate many features that enhance Web applications. XML, a well-established text format, is playing an increasingly important role in supporting Web services. XML separates data from style and format definition and allows uniform representation, interchange, sharing, and dissemination of information content over the Internet. XML and Web services provide a simplified application integration framework that drives demand for models that support secure information interchange. Providing document security in XML-based Web services requires access control models that offer specific capabilities. Our XML-based access control specification language addresses a new set of challenges that traditional security models do not address.     

基于XML安全技术的电子公文交换系统

在跨越企业边界的电子公文交换系统中,如何提高信息的安全性、开放性和互操作性是一个重要的研究课题。文中针对目前Internet/Intranet环境中跨系统边界交换数据存在的关键数据的传送与储存不安全、各系统身份验证不统一、安全技术标准不统一等问题,提出了一个基于XML安全技术的电子公文交换系统模型。该系统采用基于SAML的单点登录和认证授权,基于XACML的集成访问控制,以及基于XML加密和签名的关键数据加密保护。并在此基础上分析系统面临的威胁,提出可以应对的措施。     

XML privacy protection model based on cloud storage

When eXtensible Markup Language (XML) becomes a widespread data representation and exchange format for Web applications, safeguarding the privacy of data represented in XML documents can be indispensable. In this paper, we propose an XML privacy protection model by separating the structure and content, and with cloud storage to save content information and Trusted Third Party (TTP) to help manage structure information. To protect data privacy more effectively, we will create different Document Type Definition (DTD) views for different users according to users' privacy practice and the provider's privacy preferences. To further speed up the process of gaining access to data we will adopt the start–end region encoding scheme to encode the nodes in XML document and DTD views. The experiment result shows that this mechanism has a good performance in space and time.     

基于XML的网络安全技术

随着电子商务的普及,网络传输中越来越多地涉及到各种私密性的信息,作为网络传输资源载体的XML文档应确保其应用的安全性。该文从XML加密、XML数字签名、XML访问控制和密钥管理4个方面介绍一个XML服务平台。它将作为保证其安全应用的前提和基础。     

基于XPath的XML数据提取的C#实现

简要介绍了XPath技术,分析了使用XPath路径表示式选择XML文档节点的方式,分析了.NET对XML文档的访问支持,探讨了在.NET环境下,基于XPath技术使用C#语言实现XML文档数据提取的解决方案,为Web信息抽取软件的开发打下基础。     

On the efficiency of secure XML broadcasting

Secure broadcasting of web documents is becoming a crucial requirement for many web-based applications. Under the broadcast document dissemination strategy, a web document source periodically broadcasts (portions of) its documents to a potentially large community of users, without the need for explicit requests. By secure broadcasting, we mean that the delivery of information to users must obey the access control policies of the document source. Traditional access control mechanisms that have been adapted for XML documents, however, do not address the performance issues inherent in access control. In this paper, a labeling scheme is proposed to support rapid reconstruction of XML documents in the context of a well-known method, called XML pool encryption. The proposed labeling scheme supports the speedy inference of structure information in all portions of the document. The binary representation of the proposed labeling scheme is also investigated. In the experimental results, the proposed labeling scheme is efficient in searching for the location of decrypted information.     

Making agents secure on the semantic Web

Agents were designed to collaborate and share information. While highly desirable for interoperability, this feature is scary from the security perspective. Illegal inferences, supported by semantic Web technology and ontologies, might enable users to access unauthorized information. In addition to semantic associations and replicated data with different sensitivity, malicious agents could also exploit statistical inferences. Although each agent in a system might behave in a desired and secure way, their combined knowledge could be used to disclose sensitive data. The research community must therefore develop and implement techniques that allow control over released data. To answer the questions related to information availability (scalability), data correctness (integrity), and access control in the presence of illegal inferences and undesired collaborations (confidentiality), researchers in semantic Web technologies (XML, RDF, DAML, and multiagent systems) and information system security need to collaborate. Indeed, given the Web's openness, dynamic nature, and diverse user population, developing secure Web services will require the collaboration of experts in different fields from both industry and academia. In turn, the intelligent Web of the future will facilitate unheard of support for collaborations and information management.     

基于XML Schema技术网页安全防护机制的研究

提出了一种基于XML Schema 技术的网页安全防护机制,可解决网页中用户输入数据缺乏验证机制而导致应用层级的安全攻击.该防护机制通过描述网页输入数据的特性,将输入数据转换为XML Document,判断有无应用层级的安全攻击并采取防护措施,为网站开发提供有效而又方便的安全保障.     

面向XML文档的细粒度强制访问控制模型

XML文档存放的信息需要受到访问控制策略的保护.现有的一些面向XML文档的访问控制模型都是基于自主访问控制策略或基于角色的访问控制.高安全等级系统需要强制访问控制来保证系统内信息的安全.首先扩展了XML文档模型使其包含标签信息,并给出了扩展后的文档模型需要满足的规则.然后通过讨论XML文档上的4种操作,描述了面向XML文档的细粒度强制访问控制模型的详细内容.该模型基于XML模式技术,它的控制粒度可以达到文档中的元素或者属性.最后讨论了该模型的体系结构和一些实现机制.     

一个XML数据库强制访问控制模型

目前关于XML数据库安全性的研究大多是基于自主访问控制或者基于角色的访问控制,然而高安全等级的系统要求支持强制访问控制策略。本文建立了一个XML对象的分解与合成规则,在此基础上提出了一个支持多实例的多级安全XML数据库模型,给出了其体系结构和安全策略,并且对其安全性进行了分析。本文的研究结果可以为信息敏感部门处理半结构化信息提供理论模型上的支持。     

一种基于证书的XML访问控制模型

XML的广泛应用对其访问控制提出了需求,同时Web中大量存在的异质用户群也为授权管理增加了难度。在分析XML文档安全特性的基础上,提出了一种基于证书的XML访问控制模型,并给出了基于XML的策略描述,最后讨论了该模型的实现。     

Schema-based Web wrapping

An effective solution to automate information extraction from Web pages is represented by wrappers. A wrapper associates a Web page with an XML document that represents part of the information in that page in a machine-readable format. Most existing wrapping approaches have traditionally focused on how to generate extraction rules, while they have ignored potential benefits deriving from the use of the schema of the information being extracted in the wrapper evaluation. In this paper, we investigate how the schema of extracted information can be effectively used in both the design and evaluation of a Web wrapper. We define a clean declarative semantics for schema-based wrappers by introducing the notion of (preferred) extraction model, which is essential to compute a valid XML document containing the information extracted from a Web page. We developed the SCRAP (SChema-based wRAPper for web data) system for the proposed schema-based wrapping approach, which also provides visual support tools to the wrapper designer. Moreover, we present a wrapper generalization framework to profitably speed up the design of schema-based wrappers. Experimental evaluation has shown that SCRAP wrappers are not only able to successfully extract the required data, but also they are robust to changes that may occur in the source Web pages.     

基于XML的多Agent系统的研究与实现

作为构建开放和分布式应用系统的一种主流模式,多Agent系统有着广阔的研究前帚和应用价值。在统一建模语言（UML）的支持下,面向Agent的软件工程研究开始走向成熟。一些面向Agent的方法学提供了开发多A—gent系统的工具、应用方法或技术。随着Web服务技术的发展,XML成为Internet上数据组织和交换的标准。现有研究工作所提出的多Agent系统对XML文档提供很少的支持。针对上述问题,设计了一个基于XML的多Agent系统——XMAS。该系统采用带根连通有向图来表示XML文档数据模型,并给出相应的文档模式提取算法,XML文档数据的解析以及对Web服务的相关支持。在数据存储过程中的索引优化使得XMAS在数据查询上具有良好的性能。     

XML网络服务安全策略应用

由于互联网的开放性,使得信息安全成为日趋严重的首要问题。作为目前使用最广泛的网络数据传输技术XML网络服务,如何保证其安全性已成为人们研究的重点课题。通过对XML网络服务安全性的分析,结合XML安全服务标准,实现了XML数据本身的安全表示,通过加密和数字签名,保证数据的完整性和机密性;建立了安全的数据传输方式,保证数据传输中的安全;设计了基于策略的访问控制模型,实现了在服务器端对XML数据实施安全的访问控制,防止非法访问,从而创建一个安全的网络服务环境。     

Authorization Translation for XML Document Transformation

XML access control models proposed in the literature enforce access restrictions directly on the structure and content of an XML document. Therefore access authorization rules (authorizations, for short), which specify access rights of users on information within an XML document, must be revised if they do not match with changed structure of the XML document. In this paper, we present two authorization translation problems. The first is a problem of translating instance-level authorizations for an XML document. The second is a problem of translating schema-level authorizations for a collection of XML documents conforming to a DTD. For the first problem, we propose an algorithm that translates instance-level authorizations of a source XML document into those for a transformed XML document by using instance-tree mapping from the transformed document instance to the source document instance. For the second problem, we propose an algorithm that translates value-independent schema-level authorizations of non-recursive source DTD into those for a non-recursive target DTD by using schema-tree mapping from the target DTD to the source DTD. The goal of authorization translation is to preserve authorization equivalence at instance node level of the source document. The XML access control models use path expressions of XPath to locate data in XML documents. We define property of the path expressions (called node-reducible path expressions) that we can transform schema-level authorizations of value-independent type by schema-tree mapping. To compute authorizations on instances of schema elements of the target DTD, we need to identify the schema elements whose instances are located by a node-reducible path expression of a value-independent schema-level authorization. We give an algorithm that carries out path fragment containment test to identify the schema elements whose instances are located by a node-reducible path expression.     

XML数据库的安全查询处理

当今XML数据库查询系统必须处理快速增长的数据量和大量的用户,如果使用细粒度级别的访问控制保护敏感XML数据,则查询效率会较低,因为当用户视图需要计算得出时,很难对XML文档的每个节点实施访问控制。提出一个安全的XML查询方案,它使用缓存存储查询结果和安全信息。用户查询重写为安全的系统查询,依据缓存是否命中,决定在缓存还是源XML文档上执行得到查询结果;提出一个新的缓存替换策略LSL,它基于安全级别对缓存更新。实验结果表明,该方案能显著地改进查询系统性能。     

云环境下组合电子健康记录访问控制框架

针对云环境下电子健康记录信息安全共享的需求提出云环境下组合电子健康记录访问控制框架.在该框架中基于多个CDA文档的逻辑关系,提出并构建组合电子健康记录结构,应用基于属性的多级安全访问控制策略实现组合电子健康记录的安全管理,应用基于XLINK技术的XML Web服务实现组合电子健康记录的下载和查看.通过对比分析可说明,与已有方案相比,本方案提出的框架更加适合云环境下的电子健康信息安全共享.