In multi-hop cellular networks, data packets have to be relayed hop by hop from a given mobile station to a base station and vice-versa. This means that the mobile stations must accept to forward information for the benefit of other stations. In this paper, we propose an incentive mechanism that is based on a charging/rewarding scheme and that makes collaboration rational for selfish nodes. We base our solution on symmetric cryptography to cope with the limited resources of the mobile stations. We provide a set of protocols and study their robustness with respect to various attacks. By leveraging on the relative stability of the routes, our solution leads to a very moderate overhead.

Without sufficient nodes cooperating to provide relaying functions, a mobile ad hoc network cannot function properly. Consequently various proposals have been made which provide incentives for individual users of an ad hoc mobile network to cooperate with each other. In this paper we examine this problem and analyse the drawbacks of currently proposed incentive systems. We then argue that there may not be a need for incentive systems at all, especially in the early stages of adoption, where excessive complexity can only hurt the deployment of ad hoc networks. We look at the needs of different customer segments at each stage of the technological adoption cycle and propose that incentive systems should not be used until ad hoc networks enter mainstream markets. Even then, incentive systems should be tailored to the needs of each individual application rather than adopting a generalised approach that may be flawed or too technically demanding to be implemented in reality.

Ad-hoc networks and even more intrinsic pervasive networks face huge security lacks. In the most general case entities need to build up a well-defined security association without any pre-established secret or common security infrastructure. Under these circumstances it turns out that without unrealistic assumptions authentication of previously unknown parties is not achievable. However, for a wide spectrum of scenarios much weaker authentication forms are reasonable, e.g., for routing protocols and other protocols aiming to intensify cooperation.

Abstract—A hybrid ad hoc network is a structure-based network that is extended using multihop communications. Indeed, in this kind of network, the existence of a communication link between the mobile station and the base station is not required: A mobile station that has no direct connection with a base station can use other mobile stations as relays. Compared with conventional (single-hop) structure-based networks, this new generation can lead to a better use of the available spectrum and to a reduction of infrastructure costs. However, these benefits would vanish if the mobile nodes did not properly cooperate and forward packets for other nodes. In this paper, we propose a charging and rewarding scheme to encourage the most fundamental operation, namely packet forwarding. We use “MAC layering ” to reduce the space overhead in the packets and a stream cipher encryption mechanism to provide “implicit authentication ” of the nodes involved in the communication. We analyze the robustness of our protocols against rational and malicious attacks. We show that—using our solution—collaboration is rational for selfish nodes. We also show that our protocols thwart rational attacks and detect malicious attacks. Index Terms—Network-level security and protection, wireless communication, authentication security, payment schemes. 1

Introduction Multi-hop cellular networks (also called hybrid networks) appear to be a promising combination of the dynamics of mobile ad hoc networks and the reliability of infrastructured wireless networks. These hybrid networks o#er several advantages for users as well as operators. The network topology can be dynamically adapted to the respective needs reducing installation costs for the provider, the overall coverage area can be extended and nodes can reduce their energy consumption for transmitting packets due to shorter distances. However, several weaknesses known from mobile ad hoc networks persist. In the context of hybrid networks new possibilities to deal with these weaknesses become available. Besides the security and routing issues the cooperation among nodes is of great importance. We propose a cooperation and accounting strategy for hybrid networks called CASHnet, which stimulates cooperation among nodes by making it a rewarding alternative to selfishness. Our scheme in

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Abstract—In multi-hop wireless networks, the mobile nodes usually act as routers to relay other nodes ’ packets for enabling new applications and enhancing the network performance and deployment. However, selfish nodes may not cooperate and make use of the cooperative nodes to relay their packets, which has negative effect on the network fairness, security, and performance. Incentive systems implement micropayment in the network to stimulate the selfish nodes to cooperate. However, micropayment schemes have been originally proposed for webbased applications, so a practical incentive system should consider the differences between web-based applications and cooperation stimulation. In this paper, first, these differences are investigated and a payment model is developed for efficient implementation of micropayment in multi-hop wireless networks. Second, based on the developed payment model, an incentive system is proposed to stimulate the nodes ’ cooperation in multi-hop wireless networks. Third, reactive receipt submission mechanism is proposed to reduce the number of submitted receipts and protect against collusion attacks. Extensive analysis and simulations demonstrate that our incentive system can secure the payment, and reduce the overhead of storing, submitting, and processing the payment receipts significantly, which can improve the system’s practicality due to the high frequency of low-value payment transactions.

Abstract — We propose a concept for realizing access control in mobile ad-hoc networks to exclude nodes that do not contribute to the provision of network services from using them. Each node observes the behavior of its neighbors in order to build up opinions about their willingness to take part in different network activities. In turn, service is provided only to nodes that have positive opinions about them. A precondition for assigning opinions to nodes is having a means for authentication; we rely on a web-of-trust structure for this, where all nodes can issue certificates for others after they have verified their identities. A proactive certificate management system makes it possible – as the evaluation results presented in this paper show – to find optimal certificate chains between given keys and to quickly retrieve the needed certificates. I.

Es wird vielfach angenommen, dass die nächste Revolution in der IT-Landschaft durch die Vernetzung von eingebetteten Systemen erfolgen wird. In solche pervasiven Computeranwendungen wird IT-Sicherheit eine extrem wichtige Rolle spielen. Obwohl es starke Indikatoren gibt, dass die eingebettete Sicherheit von grosser Bedeutung sein wird, ist sie als eigenständiges Gebiet bisher kaum betrachtet worden. Ziel des vorliegenden Beitrags ist es, verschiedene Aspekt der eingebetteten Sicherheit in einer Gesamtdarstellung näher zu beleuchten. Insbesondere werden die spezifischen Probleme der eingebetteten Sicherheit näher betrachtet. Anhand von Fallbeispielen im Automobil und in ad-hoc Netzen werden zukünftige Probleme und Möglichkeiten von IT-Sicherheit in eingebetteten Anwendungen verdeutlicht. Zwei wichtige Realisierungsaspekte von sicheren eingebetteten Systemen in der Praxis, nämlich effiziente asymmetrische Verfahren in rechenbeschränkten Umgebungen und Seitenkanalattacken, werden ebenfalls diskutiert. 1 Einleitung In den letzten Jahrzehnten hat das Internet zunehmend Computer vernetzt und hat mit Anwendungen wie dem World Wide Web und Email den Informationsfluss und die Kommunikation in vielen Lebensbereichen dramatisch beeinflusst. Geschäftsabläufe, private Kommunikation, Interaktion zwischen Bürgern

INTRODUCTION Although the need for protocol extensions dealing with cooperation issues for ad hoc routing protocols is undoubtedly accepted, it is still a question of belief whether such protocol extensions really intensify participation within the ad hoc network and benefit the community. This statement is applicable to both detection-based (e.g. [3], [4]) and motivationbased approaches (e.g. [1], [2]). It is our intention to give a quantitative estimation of the added value of such cooperation based approaches. We present results based on two assumptions: First, the co-operation approach uses an underlying on-demand routing protocol (DSR, AODV, etc.) and in particular tries to combat malicious behavior of nodes in the forwarding phase. More precisely, although a node behaves well in the routing phase, it simply drops packets in the forwarding phase. Second, the network topology is low-densely filled with nodes, meaning that each node's transmission range does not reach more than a f