So far, research on mobile ad hoc networks has been focused primarily on routing issues. Security, on the other hand, has been given a lower priority. This paper provides an overview of security problems for mobile ad hoc networks, distinguishing the threats on basic mechanisms and on security mechanisms. It then describes our solution to protect the security mechanisms. The original features of this solution include that (i) it is fully decentralized and (ii) all nodes are assigned equivalent roles.

Lack of cooperation (free riding) is one of the key problems that confronts today's P2P systems. What makes this problem particularly difficult is the unique set of challenges that P2P systems pose: large populations, high turnover, asymmetry of interest, collusion, zero-cost identities, and traitors. To tackle these challenges we model the P2P system using the Generalized Prisoner's Dilemma (GPD), and propose the Reciprocative decision function as the basis of a family of incentives techniques. These techniques are fully distributed and include: discriminating server selection, maxflowbased subjective reputation, and adaptive stranger policies. Through simulation, we show that these techniques can drive a system of strategic users to nearly optimal levels of cooperation.

In contrast with conventional networks, mobile ad hoc networks usually do not provide online access to trusted authorities or to centralized servers, and they exhibit frequent partitioning due to link and node failures and to node mobility. For these reasons, traditional security solutions that require online trusted authorities or certificate repositories are not well-suited for securing ad hoc networks. In this paper, we propose a fully self-organized public-key management system that allows users to generate their publicprivate key pairs, to issue certificates, and to perform authentication regardless of the network partitions and without any centralized services. Furthermore, our approach does not require any trusted authority, not even in the system initialization phase.

this paper, our contributions are to generalize from the traditional symmetric EPD to the asymmetric transactions of P2P applications, map out the design space of EPD-based incentive techniques, and simulate a subset of these techniques. Our findings are as follows: Incentive techniques relying on private history (where entites only use their private histories of entities' actions) fail as the population size increases

The proliferation of web-based social networks has lead to new innovations in social networking, particularly by allowing users to describe their relationships beyond a basic connection. In this dissertation, I look specifically at trust in web-based social networks, how it can be computed, and how it can be used in applications. I begin with a definition of trust and a description of several properties that affect how it is used in algorithms. This is complemented by a survey of web-based social networks to gain an understanding of their scope, the types of relationship information available, and the current state of trust. The computational problem of trust is to determine how much one person in the network should trust another person to whom they are not connected. I present two sets of algorithms for calculating these trust inferences: one for networks with binary trust ratings, and one for continuous ratings. For each rating scheme, the algorithms are built upon the defined notions of trust. Each is then analyzed theoretically and with respect to simulated and actual trust networks to determine how accurately they calculate the opinions of people in the system. I show that in both rating schemes the algorithms

Abstract—Within the realm of network security, we interpret the concept of trust as a relation among entities that participate in various protocols. Trust relations are based on evidence created by the previous interactions of entities within a protocol. In this work, we are focusing on the evaluation of trust evidence in ad hoc networks. Because of the dynamic nature of ad hoc networks, trust evidence may be uncertain and incomplete. Also, no preestablished infrastructure can be assumed. The evaluation process is modeled as a path problem on a directed graph, where nodes represent entities, and edges represent trust relations. We give intuitive requirements and discuss design issues for any trust evaluation algorithm. Using the theory of semirings, we show how two nodes can establish an indirect trust relation without previous direct interaction. We show that our semiring framework is flexible enough to express other trust models, most notably PGP’s Web of Trust. Our scheme is shown to be robust in the presence of attackers. Index Terms—Trust evaluation, trust metric, trust model, semiring. I.

Abstract—Wireless Community Networks (WCNs) are wide-area wireless networks whose nodes are owned and managed by volunteers. We focus on the provision of free Internet access to mobile users through WCN-controlled wireless LAN access points (APs). We rely on reciprocity: a person participates in the WCN and provides free Internet access to mobile users in order to enjoy the same benefit when mobile. Our reciprocity scheme is compatible with the distinctive structure of WCNs: it does not require registration with authorities, relying only on uncertified free identities (public-private key pairs). Users sign digital receipts when they consume service. The receipts form a receipt graph, which is used as input to a reciprocity algorithm that identifies contributing users using network flow techniques. Simulations show that this algorithm can sustain reciprocal cooperation. We have implemented our algorithm to run on common WCN equipment, namely the Linksys WRT54GS AP. I.

Due to the limited number of available IP addresses most computers on the Internet use dynamic IP addresses which causes problems for applications that have to maintain routing tables, for example, peer-to-peer systems. To overcome this we propose unique peer identifiers in the routing tables and apply the peer-to-peer system itself to maintain consistent id-to-IP mappings to be used in the routing process. While this may sound like a recursive hen-egg problem we show that it is in fact possible to devise such a mapping service for realistic scenarios. Our approach is completely decentralized, self-maintaining, and light-weight. It takes into account security to provide sufficient security guarantees for the mappings. We also assume that the service operates in an environment with low online probability of the peers constituting the service.

Identification is an essential building block for many services in distributed information systems. The quality and purpose of identification may differ, but the basic underlying problem is always to bind a set of attributes to an identifier in a unique and deterministic way.

The huge success of eBay has proven the demand for customer-to-customer (C2C) electronic commerce. eBay is a centralized infi'astructure with all its scalability problems (network bandwidth, server load, availability, etc.). In this paper we m'gue that C2C e-commerce is an application domain that maps naturally onto the emergent field of P2P systems simply by its underlying interaction model of customers, i.e., peers. This offers the opportunity to take P2P systems beyond mere file sharing systems into interesting new application domains.