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 ofien 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 Policy Maker, that will facilitate the development of security features in a wide range of network services. 1.

of information into account. Based on a realistic model of a german city with up to 10000 vehicles, our results show that a decentralized parking place information system works efficiently even with 5 % of vehicles equipped with Wireless-LAN and without the help of any message relaying infrastructure. This fact

In this paper, we describe three key problems for trust management in federated systems and present a layered architecture for addressing them. The three problems we address include how to express and verify trust in a flexible and scalable manner, how to monitor the use of trust relationships over time, and how to manage and reevaluate trust relationships based on historical traces of past behavior. While previous work provides the basis for expressing and verifying trust, it does not address the concurrent problems of how to continuously monitor and manage trust relationships over time. These problems close the loop on trust management and are especially relevant in the context of federated systems where remote resources can be acquired across multiple administrative domains and used in potentially undesirable ways (e.g., to launch denial-ofservice attacks).

Abstract Decentralized and unstructured peer-to-peer networks such as Gnutella are attractive for certain applicationsbecause they require no centralized directories and no precise control over network topologies and data placement. However, the flooding-based query algorithm used in Gnutella does

Abstract We consider the problem of cooperation among a collection of vehicles performing a shared task using intervehicle communication to coordinate their actions. We apply tools from graph theory to relate the topology of the communication network to formation stability. We prove a Nyquist

Abstract A distributed system can be characterized by the fact that the global state is distributed and that a common time base does not exist. However, the notion of time is an important concept in every day life of our decentralized \ r eal world" and helps to solve problems like getting a

Abstract A promising technique for protecting privacy and integrity of sensitive data is to statically check information flow within programs that manipulate the data. While previous work has proposed programming language extensions to allow this static checking, the resulting languages are too

Abstract. GLS is a new distributed location service which tracks mobile node locations. GLS combined with geographic forwarding allows the construction of ad hoc mobile networks that scale to a larger number of nodes than possible with previous work. GLS is decentralized and runs on the mobile

justice problems as decentralized global distributive justice problems. This permits global distributive justice analysis, mainly done by philosophers, to inform policymakers on what the local distributive justice goal should be, and also allows us to understand what the global distributive justice

groups) and decentralized user-group assignment (where administrators are selectively delegated authority to assign certain users to certain groups) can be implemented by means of Microsoft remote procedure call (RPC) programs. In both respects the experimental goal is to implement previously published