Keywords Ad hoc networks, Byzantine faults, fault-tracing. Introduction

Ad hoc networks, Byzantine faults, fault-tracing.

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   Introduction
   

Ad hoc networks are dynamic collections of self-organizing mobile nodes with links that are changing in an unpredictable way. They are characterized by a dynamic topology and the lack of any fixed infrastructure. The communication medium is broadcast. The nodes can be regarded as wireless mobile hosts with limited power, range and bandwidth. The recent rise in popularity of mobile wireless devices and technological developments has made possible the deployment of such networks for several applications. Indeed, because ad hoc networks do not have any fixed infrastructure such as stations or routers, they are highly applicable to emergency deployments, disasters, search and rescue missions and military operations. So far, most of the research has focused on functionality issues and efficiency (see e.g., [2,5,8,10,9,14,16,17,18,19,21], with security given a lower priority, and in many cases, regarded as an add-on

* This material is based on work supported in part by the U.S. Army Research Laboratory and the U.S. Research Office under grant number DAAD19-02-1-0235.

afterthought technology rather than design feature (e.g. [12,15]).

Our goal in this paper is to show that tracing malicious (insider) faults of ad hoc networks is not as simple as it may appear at first. More specifically, that a Bayesian approach that exploits past statistical behavior (history) cannot be used to trace a malicious user (an insider) from his/her behavior, because such a user can avoid detection by behaving non-maliciously whenever an Intrusion Detection mechanism is triggered. In particular we show (Section 2) that the adaptive probing technique used in Auerbuch et al. [1] is flawed and that it will fail to trace a truly Byzantine malicious fault. We then propose our own tracing algorithm that combines cryptographic mechanisms with broadcast channels and ping channels.

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