Toward a Formal Model of Fair Exchange - a Game Theoretic Approach

A fair exchange protocol is a protocol, in which two (or more) mutually suspicious parties exchange their digital items in a way that neither party can gain an advantage over the other by misbehaving. Many fair exchange protocols have been proposed in the academic literature, but they provide rather different types of fairness. The formal comparison of these proposals remained difficult, mainly, because of the lack of a common formal framework, in which each can be modelled and formal fairness definitions can be given. In this paper, we propose to use game theory for this purpose. We show how to represent fair exchange protocols with game trees and give three definitions of fairness using standard game theoretic notions. We are not aware of any other work that uses the apparatus of game theory for modelling fair exchange protocols

Report on a Working Session on Security in Wireless Ad Hoc Networks

No abstrac

Enforcing Service Availability in Mobile Ad-Hoc WANs

In this paper, we address the problem of service availability in mobile ad-hoc WANs. We present a secure mechanism to stimulate end users to keep their devices turned on, to refrain from overloading the network, and to thwart tampering aimed at converting the device into a ``selfish`` one. Our solution is based on the application of a tamper resistant security module in each device and cryptographic protection of messages

A Pessimistic Approach to Trust in Mobile Agent Platforms

To be provided later

A Survey of Interdependent Information Security Games

Risks faced by information system operators and users are not only determined by their own security posture, but are also heavily affected by the security-related decisions of others. This interdependence between information system operators and users is a fundamental property that shapes the efficiency of security defense solutions. Game theory is the most appropriate method to model the strategic interactions between these participants. In this survey, we summarize game-theoretic interdependence models, characterize the emerging security inefficiencies, and present mechanisms to improve the security decisions of the participants. We focus our attention on games with interdependent defenders and do not discuss two-player attackerdefender games. Our goal is to distill the main insights from the state-of-the-art and to identify the areas that need more attention from the research community

A Formal Analysis of Syverson`s Rational Exchange Protocol

In this paper, we provide a formal analysis of a rational exchange protocol proposed by Syverson. A rational exchange protocol guarantees that misbehavior cannot generate benefits, and is therefore discouraged. The analysis is performed using our formal model, which is based on game theory. In this model, rational exchange is defined in terms of a Nash equilibrium

Nash Equilibria of Packet Forwarding Strategies in Wireless Ad Hoc Networks

In self-organizing ad hoc networks, all the networking functions rely on the contribution of the participants. As a basic example, nodes have to forward packets for each other in order to enable multi-hop communication. In recent years, incentive mechanisms have been proposed to give nodes incentive to cooperate, especially in packet forwarding. However, the need for these mechanisms was not formally justified. In this paper, we address the problem of whether cooperation can exist without incentive mechanisms. We propose a model based on game theory and graph theory to investigate equilibrium conditions of packet forwarding strategies. We prove theorems about the equilibrium conditions for both cooperative and non-cooperative strategies. We perform simulations to estimate the probability that the conditions for a cooperative equilibrium hold in randomly generated network scenarios. As the problem is involved, we deliberately restrict ourselves to a static configuration. We conclude that in static ad hoc networks - where the relationships between the nodes are likely to be stable - cooperation needs to be encouraged. forwarding. However, the need for these mechanisms was not formally justified. In this paper, we address the problem of whether cooperation can exist \emph{without} incentive mechanisms. We propose a model based on game theory and graph theory to investigate equilibrium conditions of packet forwarding strategies. We prove theorems about the equilibrium conditions for both cooperative and non-cooperative strategies. We perform simulations to estimate the probability that the conditions for a cooperative equilibrium hold in randomly generated network scenarios. As the problem is involved, we deliberately restrict ourselves to a static configuration. We conclude that in static ad hoc networks -- where the relationships between the nodes are likely to be stable -- cooperation needs to be encouraged

Mobility Helps Peer-to-Peer Security

We propose a straightforward technique to provide peer-to-peer security in mobile networks. We show that far from being a hurdle, mobility can be exploited to set up security associations among users. We leverage on the temporary vicinity of users, during which appropriate cryptographic protocols are run. We illustrate the operation of the solution in two scenarios, both in the framework of mobile ad hoc networks. In the first scenario, we consider fully self-organized security: users authenticate each other by visual contact and by the activation of an appropriate secure side channel of their personal device; we show that the process can be fuelled by taking advantage of trusted acquaintances In the second scenario, we assume the presence of an off-line certification authority and we show how mobility helps to solve the security-routing interdependency cycle; in this case, the security protocol runs over one-hop radio links. We then show that the proposed solution is generic: it can be deployed on any mobile network and it can be implemented either with symmetric or with asymmetric cryptography. We provide a detailed performance analysis by studying the behavior of the solution on various mobility models

A Micro-Payment Scheme Encouraging Collaboration in Multi-Hop Cellular Networks

We propose a micro-payment scheme for multi-hop cellular networks that encourages collaboration in packet forwarding by letting users benefit from relaying others` packets. At the same time as proposing mechanisms for detecting and rewarding collaboration, we introduce appropriate mechanisms for detecting and punishing various forms of abuse. We show that the resulting scheme -- which is exceptionally light-weight -- makes collaboration rational and cheating undesirable

Equilibrium Analysis of Packet Forwarding Strategies in Wireless Ad Hoc Networks - the Static Case (extended version)

In multi-hop wireless networks, every node is expected to forward packets for the benefit of other nodes. Yet, if each node is its own authority, then it may selfishly deny packet forwarding in order to save its own resources. Some researchers have proposed to introduce an incentive mechanism in the network that motivates the nodes to cooperate. In this paper, we address the question of whether such an incentive mechanism is necessary or cooperation between the nodes exists in the absence of it. We define a model in a game theoretic framework and identify the conditions under which cooperative strategies can form an equilibrium. As theproblem is somewhat involved, we deliberately restrict ourselves to a static configuration