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Advancements in location technologies reliability and precision are fostering the development of location-based services that make use of the location information of users. An increasingly important category of such services is represented by Location-based Access Control (LBAC) systems that integrate traditional access control mechanisms with access conditions based on the physical position of users and other attributes related to the users location. Since privacy is extremely important for users, protection of their location information is paramount to the success of such emerging location-based services. In this chapter, we first present an overview of Location-based Access Control systems and then characterize the location privacy protection problem. We then discuss the main techniques that have been proposed to protect location information, focusing on the obfuscation-based techniques. We conclude the chapter by showing a privacy-aware LBAC architecture and describing how a location-based access control policy can be evaluated. [ABSTRACT FROM AUTHOR]

XML has become a crucial tool for data storage and exchange. In this chapter, after a brief introduction on the basic structure of XML, we illustrate the most important characteristics of access control models. We then discuss two models for XML documents, pointing out their main characteristics. We finally present other proposals, describing their main features and their innovation compared to the previous two models. [ABSTRACT FROM AUTHOR]

Access control is the process of mediating every request to resources and data maintained by a system and determining whether the request should be granted or denied. Traditional access control models and languages result limiting for emerging scenarios, whose open and dynamic nature requires the development of new ways of enforcing access control. Access control is then evolving with the complex open environments that it supports, where the decision to grant an access may depend on the properties (attributes) of the requestor rather than her dentity and where the access control restrictions to be enforced may come from different authorities. These issues pose several new challenges to the design and implementation of access control systems. In this chapter, we present the emerging trends in the access control field to address the new needs and desiderata of today's systems. [ABSTRACT FROM AUTHOR]

Access control is the process of mediating every request to resources and data maintained by a system and determining whether the request should be granted or denied. Access control plays an important role in overall system security. The development of an access control system requires the definition of the regulations (policies) according to which access is to be controlled and their implementation as functions executable by a computer system. The access control policies are usually formalized through a security model, stated through an appropriate specification language, and then enforced by the access control mechanism enforcing the access control service. The separation between policies and mechanisms introduces an independence between protection requirements to be enforced on the one side, and mechanisms enforcing them on the other. It is then possible to: i) discuss protection requirements independently of their implementation, ii) compare different access control policies as well as different mechanisms that enforce the same policy, and iii) design mechanisms able to enforce multiple policies. This latter aspect is particularly important: if a mechanism is tied to a specific policy, a change in the policy would require changing the whole access control system; mechanisms able to enforce multiple policies avoid this drawback. The formalization phase between the policy definition and its implementation as a mechanism allows the definition of a formal model representing the policy and its working, making it possible to define and prove security properties that systems enforcing the model will enjoy [30]. [ABSTRACT FROM AUTHOR]

Data outsourcing is emerging today as a successful solution for organizations looking for a cost-effective way to make their data available for on-line querying. To protect outsourced data from unauthorized accesses, even from the (honest but curious) host server, data are encrypted and indexes associated with them enable the server to execute queries without the need of accessing cleartext. Current solutions consider the whole database as encrypted with a single key known only to the data owner, which therefore has to be kept involved in the query execution process. In this paper, we propose different multi-key data encryption strategies for enforcing access privileges. Our strategies exploit different keys, which are distributed to the users, corresponding to the different authorizations. We then present some experiments evaluating the quality of the proposed strategies with respect to the amount of cryptographic information to be produced and maintained. [ABSTRACT FROM AUTHOR]

The protection of privacy is an increasing concern in today's global infrastructure. One of the most important privacy protection principles states that personal information collected for one purpose may not be used for any other purpose without the specific informed consent of the person it concerns. Although users provide personal information for use in one specific context, they often have no idea on how such a personal information may be used subsequently. In this paper, we introduce a new type of privacy policy, called data handling policy, which defines how the personal information release will be (or should be) dealt with at the receiving party. A data handling policy allows users to define simple and appropriate levels of control over who sees what information about them and under which circumstances. [ABSTRACT FROM AUTHOR]

Security is a crucial concern for commercial and mission critical applications in Web-based environments. In our model, context information associated with Access Control management policies is defined according to basic operators that can be represented using the Web Ontology Language. Standard inference procedures of Description Logics are being used to check the consistency of context information referred to by policy conditions and, more interestingly, to pre-process context information for grounding policy propagation and enabling conflict resolution. In this paper, we extend the model to encompass part-of relations between entities in context descriptions and, consequently, revise the policy propagation criteria being applied to the model to take into account the newly introduced relations. Finally, we exemplify modality conflicts arising from part-of relations, a category of extensional conflicts (i.e., inconsistencies related to individuals) that cannot be foreseen by looking at the terminology underlying context information. [ABSTRACT FROM AUTHOR]

The protection of privacy in today's global infrastructure requires the combined application solution from technology (technical measures), legislation (law and public policy), and organizational and individual policies and practices. Emerging scenarios of user-service interactions in the digital world are also pushing toward the development of powerful and flexible privacy-enhanced models and languages. This paper aims at introducing concepts and features that should be investigated to fulfill this demand. In particular, the content of this paper is a result of our ongoing activity in the framework of the PRIME project (Privacy and Identity Management for Europe), funded by the European Commission, whose objective is the development of privacy-aware solutions for enforcing security. [ABSTRACT FROM AUTHOR]

Database outsourcing is becoming increasingly popular introducing a new paradigm, called database-as-a-service, where a client's database is stored at an external service provider. Outsourcing databases to external providers promises higher availability and more effective disaster protection than in-house operations. This scenario presents new research challenges on which the usability of the system is based. In particular, one important aspect is the metadata that must be provided to support the proper working of the system. In this paper, we illustrate the metadata that are needed, at the client and server, to store and retrieve mapping information for processing a query issued by a client application to the server storing the outsourced database. We also present an approach to develop an efficient access control technique and the corresponding metadata needed for its enforcement. [ABSTRACT FROM AUTHOR]