We introduce the use, monitoring, and enforcement of integrity constraints in trust management-style authorization systems. We consider what portions of the policy state must be monitored to detect violations of integrity constraints. Then we address the fact that not all participants in a trust management system can be trusted to assist in such monitoring, and show how many integrity constraints can be monitored in a conservative manner so that trusted participants detect and report if the system enters a policy state from which evolution in unmonitored portions of the policy could lead to a constraint violation.
In , we listed several papers presenting various trust management systems. None of these incorporates a notion of integrity constrains. The work in trust management that is most closely related is @cite_13 . As we discussed at the beginning of , that work is complimentary to ours. It studies the problem of determining, given a state , a role monitor , and a constraint @math , whether there is a reachable state in which @math is violated. By contrast, we analyze the problem of which roles must have their definitions monitored to detect when such a is entered.
@cite_13
2170496240 202035697 2043144080 2000368422
We identify the trust management problem as a distinct and important component of security in network services. Aspects of the trust management problem include formulating security policies and security credentials, determining whether particular sets of credentials satisfy the relevant policies, and deferring trust to third parties. Existing systems that support security in networked applications, including X.509 and PGP, address only narrow subsets of the overall trust management problem and often do so in a manner that is appropriate to only one application. This paper presents a comprehensive approach to trust management, based on a simple language for specifying trusted actions and trust relationships. It also describes a prototype implementation of a new trust management system, called PolicyMaker, that will facilitate the development of security features in a wide range of network services. The ubiquity of the Internet has led to increased resource sharing between large numbers of users in widely-disparate administrative domains. Unfortunately, traditional identity-based solutions to the authorization problem do not allow for the dynamic establishment of trust, and thus cannot be used to facilitate interactions between previously-unacquainted parties. Furthermore, the management of identity-based systems becomes burdensome as the number of users in the system increases. To address this gap between the needs of open computing systems and existing authorization infrastructures, researchers have begun to investigate novel attribute-based access control (ABAC) systems based on techniques such as trust negotiation and other forms of distributed proving. To date, research in these areas has been largely theoretical and has produced many important foundational results. However, if these techniques are to be safely deployed in practice, the systems-level barriers hindering their adoption must be overcome. In this thesis, we show that safely and securely adopting decentralized ABAC approaches to authorization is not simply a matter of implementation and deployment, but requires careful consideration of both formal properties and practical issues. To this end, we investigate a progression of important questions regarding the safety analysis, deployment, implementation, and optimization of these types of systems. We first show that existing ABAC theory does not properly account for the asynchronous nature of open systems, which allows attackers to subvert these systems by forcing decisions to be made using inconsistent system states. To address this, we develop provably-secure and lightweight consistency enforcement mechanisms suitable for use in trust negotiation and distributed proof systems. We next focus on deployment issues, and investigate how user interactions can be audited in the absence of concrete user identities. We develop the technique of virtual fingerprinting, which can be used to accomplish this task without adversely affecting the scalability of audit systems. Lastly, we present TrustBuilder2, which is the first fully-configurable framework for trust negotiation. Within this framework, we examine availability problems associated with the trust negotiation process and develop a novel approach to policy compliance checking that leverages an efficient pattern-matching approach to outperform existing techniques by orders of magnitude. Trust management is a form of distributed access control that allows one principal to delegate some access decisions to other principals. While the use of delegation greatly enhances flexibility and scalability, it may also reduce the control that a principal has over the resources it owns. Security analysis asks whether safety, availability, and other properties can be maintained while delegating to partially trusted principals. We show that in contrast to the undecidability of classical Harrison--Ruzzo--Ullman safety properties, our primary security properties are decidable. In particular, most security properties we study are decidable in polynomial time. The computational complexity of containment analysis, the most complicated security property we study, varies according to the expressive power of the trust management language. Managing trust is a problem of particular importance in peer-to-peer environments where one frequently encounters unknown agents. Existing methods for trust management, that are based on reputation, focus on the semantic properties of the trust model. They do not scale as they either rely on a central database or require to maintain global knowledge at each agent to provide data on earlier interactions. In this paper we present an approach that addresses the problem of reputation-based trust management at both the data management and the semantic level. We employ at both levels scalable data structures and algorithms that require no central control and allow to assess trust by computing an agents reputation from its former interactions with other agents. Thus the meethod can be implemented in a peer-to-peer environment and scales well for very large numbers of participants. We expect that scalable methods for trust management are an important factor, if fully decentralized peer-to-peer systems should become the platform for more serious applications than simple file exchange.