Secure Incentives to Cooperate for Wireless Networks

The operating principle of certain wireless networks makes essential the cooperation between the mobile nodes. However, if each node is an autonomous selfish entity, cooperation is not guaranteed and therefore we need to use incentive techniques. In this thesis, we study cooperation in three different types of networks: WiFi networks, Wireless Mesh Networks (WMNs), and Hybrid Ad-hoc networks. Cooperation has a different goal for each of these networks, we thus propose incentive mechanisms adapted to each case. In the first chapter of this thesis, we consider WiFi networks whose wide-scale adoption is impeded by two major hurdles: the lack of a seamless roaming scheme and the variable QoS experienced by the users. We devise a reputation-based solution that (i) allows a mobile node to connect to a foreign Wireless ISP in a secure way while preserving his anonymity and (ii) encourages the WISPs to cooperate, i.e., to provide the mobile clients with a good QoS. Cooperation appears here twofold: First, the mobile clients have to collaborate in order to build and maintain the reputation system and second, the use of this reputation system encourages the WISPs to cooperate. We show, by means of simulations, that our reputation model indeed encourages the WISPs to behave correctly and we analyze the robustness of our solution against various attacks. In the second chapter of the thesis, we consider Wireless Mesh Networks (WMNs), a new and promising paradigm that uses multi-hop communications to extend WiFi networks. Indeed, by connecting only one hot spot to the Internet and by deploying several Transit Access Points (TAPs), a WISP can extend its coverage and serve a large number of clients at a very low cost. We analyze the characteristics of WMNs and deduce three fundamental network operations that need to be secured: (i) the routing protocol, (ii) the detection of corrupt TAPs and (iii) the enforcement of a proper fairness metric in WMNs. We focus on the fairness problem and propose FAME, an adaptive max-min fair resource allocation mechanism for WMNs. FAME provides a fair, collision-free capacity use of the WMN and automatically adjusts to the traffic demand fluctuations of the mobile clients. We develop the foundations of the mechanism and demonstrate its efficiency by means of simulations. We also experimentally assess the utility of our solution when TAPs are equipped with directional antennas and distinct sending and receiving interfaces in the Magnets testbed deployed in Berlin. In the third and last chapter of this thesis, we consider Hybrid Ad-hoc networks, i.e., infrastructured networks that are extended using multi-hop communications. We propose a secure set of protocols to encourage the most fundamental operation in these networks, namely packet forwarding. This solution is based on a charging and rewarding system. 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 the use of our solution makes cooperation rational for selfish nodes. We also show that our protocols thwart rational attacks and detect malicious attacks

Reputation-based Wi-Fi Deployment - Protocols and Security Analysis

In recent years, wireless Internet service providers (WISPs) have established thousands of WiFi hot spots in cafes, hotels and airports in order to offer to travelling Internet users access to email, web or other Internet service. However, two major problems still slow down the deployment of this kind of networks: the lack of a seamless roaming scheme and the variable quality of service experienced by the users. This paper provides a response to these two problems: We present a solution that, on the one hand, allows a mobile node to connect to a foreign WISP in a secure way while preserving its anonymity and, on the other hand, encourages the WISPs to provide the users with good QoS. We analyse the robustness of our solution against various attacks and we prove by means of simulations that our reputation model indeed encourages the WISPs to behave correctly

Securing Wireless Mesh Networks

Using wireless mesh networks to offer Internet connectivity is becoming a popular choice for wireless Internet service providers as it allows fast, easy, and inexpensive network deployment. However, security in WMNs is still in its infancy as very little attention has been devoted thus far to this topic by the research community. In this article we describe the specifics of WMNs and identify three fundamental network operations that need to be secured

A Fair Scheduling for Wireless Mesh Networks

Wireless Mesh Networks (WMNs) represent a new and promising paradigm that uses multi-hop communications to extend WiFi networks: By deploying only one hot spot (directly connected to the Internet) and several transient access points (TAPs), an Internet Service Provider (ISP) can extend its coverage and serve a large number of clients using a single broadband connection. Unfortunately, if the medium access protocol is poorly designed or inadequate, it can lead to severe unfairness and low bandwidth utilization. In this paper, we propose a fair scheduling mechanism that optimizes the bandwidth utilization in the mesh network. Our solution assigns transmission rights to the links in the WMN and maximizes the spatial reuse (i.e., the possibility for links that do not contend to be activated at the same time). We show that our solution is fair and collision-free, and we evaluate its efficiency by means of simulations

A Charging and Rewarding Scheme for Packet Forwarding

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

Node Cooperation in Hybrid Ad hoc Networks

A hybrid ad hoc network is a structure-based network that is extended using multi-hop 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

Reputation-based Wi-Fi Deployment

Wi-Fi networks have a very strong potential: They are easy to deploy, they use unlicensed frequencies and they provide Internet connectivity that is several times faster than by cable modem. However, two major problems still need to be solved: the lack of a seamless roaming scheme and the variable quality of service experienced by the users. The reputation-based solution presented in this paper solves both problems: It allows a mobile node to connect to a foreign Wireless Internet Service Provider (WISP) in a secure way while preserving its anonymity and it encourages the WISPs to provide the users with good QoS. We analyze the robustness of our solution against various attacks and we prove by means of simulations that our reputation model indeed encourages the WISPs to behave correctly. We also propose a simple mechanism that allows the WISPs to predict the QoS they are able to offer to the (mobile) clients

Cooperation in Multi-hop Cellular Networks

Naouel Ben Salem, Levente Buttyan, Jean-Pierre Hubaux and Markus Jakobsson abstract: In multi-hop cellular networks, 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) cellular networks, this new generation can lead to a better usage 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 analyse the robustness of our protocols against rational and malicious attacks. We show that our protocols thwart rational attacks and detect malicious attacks. We also show that our solution makes collaboration rational for selfish nodes

A Payment Scheme for Broadcast Multimedia Streams

Streaming multimedia data on the Internet is developing as a mainstream technology, which attracts many users by providing a new and convenient form of access to online multimedia information. While its strong business potential is obvious, many problems related to charging, copyright protection, and privacy can delay or even hinder its extensive deployment. In this paper, we are concerned with the charging problem, and propose an electronic payment scheme to use for purchasing broadcast multimedia streams. Our design respects the pay-per-use principle, makes cheating uninteresting for both the user and the service provider, resists against forgery and over-spending, protects sensitive payment information and user privacy, and allows the identification of misbehaving users