In recent years, workflow management systems (WFMSs) have gained popularity in both research and commercial sectors. WFMSs are used to coordinate and streamline business processes. Very large WFMSs are often used in organizations with users in the range of several thousands and process instances in the range of tens and thousands. To simplify the complexity of security administration, it is common practice in many businesses to allocate a role for each activity in the process and then assign one or more users to each role—granting an authorization to roles rather than to users. Typically, security policies are expressed as constraints (or rules) on users and roles; separation of duties is a well-known constraint. Unfortunately, current role-based access control models are not adequate to model such constraints. To address this issue we (1) present a language to express both static and dynamic authorization constraints as clauses in a logic program; (2) provide formal notions of constraint consistency; and (3) propose algorithms to check the consistency of constraints and assign users and roles to tasks that constitute the workflow in such a way that no constraints are violated.

A temporal RBAC (TRBAC) model has recently been proposed that addresses

XML (eXtensible Markup Language) has emerged as a prevalent standard for document representation and exchange on the Web. It is often the case that XML documents contain information of different sensitivity degrees that must be selectively shared by (possibly large) user communities. There is thus the need for models and mechanisms enabling the specification and enforcement of access control policies for XML documents. Mechanisms are also required enabling a secure and selective dissemination of documents to users, according to the authorizations that these users have. In this article, we make several contributions to the problem of secure and selective dissemination of XML documents. First, we define a formal model of access control policies for XML documents. Policies that can be defined in our model take into account both user profiles, and document contents and structures. We also propose an approach, based on an extension of the Cryptolope TM approach [Gladney and Lotspiech 1997], which essentially allows one to send the same document to all users, and yet to enforce the stated access control policies. Our approach consists of encrypting different portions of the same document according to different encryption keys, and selectively distributing these keys to the various users according to the access control policies. We show that the number of encryption keys that have to be generated under our approach is minimal and we present an architecture to support document distribution.

In this article, we propose an access control mechanism for Web-based social networks, which adopts a rule-based approach for specifying access policies on the resources owned by network participants, and where authorized users are denoted in terms of the type, depth, and trust level of the relationships existing between nodes in the network. Different from traditional access control systems, our mechanism makes use of a semidecentralized architecture, where access control enforcement is carried out client-side. Access to a resource is granted when the requestor is able to demonstrate being authorized to do that by providing a proof. In the article, besides illustrating the main notions on which our access control model relies, we present all the protocols underlying our system and a performance study of the implemented prototype.

Access control models, such as the ones supported by commercial DBMSs, are not yet able to fully meet many application needs. An important requirement derives from the temporal dimension that permissions have in many real-world situations. Permissions are often limited in time or may hold only for specific periods of time. In this article, we present an access control model in which periodic temporal intervals are associated with authorizations. An authorization is automatically granted in the specified intervals and revoked when such intervals expire. Deductive temporal rules with periodicity and order constraints are provided to derive new authorizations based on the presence or absence of other authorizations in specific periods of time. We provide a solution to the problem of ensuring the uniqueness of the global set of valid authorizations derivable at each instant, and we propose an algorithm to compute this set. Moreover, we address issues related to the efficiency of access control by adopting a materialization approach. The resulting model provides a high degree of flexibility and supports the specification of several protection requirements that cannot be expressed in traditional access control models.

No abstract

Abstract-In this paper, we present Trust-X , a comprehensive XML-based [12] framework for trust negotiations, specifically conceived for a peer-to-peer environment. Trust negotiation is a promising approach for establishing trust in open systems like the Internet, where sensitive interactions may often occur between entities at first contact, with no prior knowledge of each other. The framework we propose takes into account all aspects related to negotiations, from the specification of the profiles and policies of the involved parties to the selection of the best strategy to succeed in the negotiation. Trust-X presents a number of innovative features, such as the support for protection of sensitive policies, the use of trust tickets to speed up the negotiation, and the support of different strategies to carry on a negotiation. In this paper, besides presenting the language to encode security information, we present the system architecture and algorithms according to which negotiations can take place.

This Java-based access-control system supports secure XML document administration at varying levels of granularity.