Security Aware Ad Hoc Routing for Wireless Networks
Wireless ad hoc networks have been proposed to support dynamic scenarios where no wired infrastructure exist. Ad hoc environments introduce two main problems not commonly faced by traditional fixed-network routing protocols. These are the lack of xed infrastructure support and the frequent changes to network topology. At the physical level, wireless channels o er p o or protection to protocol packets and are susceptible to signal interference, jamming, eavesdropping, and distortion. Adding additional processing (e.g., for reliability), and intelligence (error-correcting codes, frequency hopping, etc.) at the physical and MAC layers, overcomes some of these limitations. At the network layer, most ad hoc routing protocols are cooperative by nature [6], and rely on implicit trust-your-neighb or relationships to route packets among participating nodes. This naive trust model allows malicious nodes to paralyze an ad hoc network by inserting erroneous routing updates, replaying old routing information, changing routing updates, or advertising incorrect routing information . While these attacks are possible in xed networks as well, the nature of the ad hoc environment magni es their e ects, and makes their detection difficult . The characteristics of an ad hoc network demand new metrics for routing. Traditionally, distance (measured in hops) is used as the metric in most ad hoc route-discovery algorithms (e.g., AODV, DSR, ZRP, TORA etc.). The use of other metrics (e.g., geographic location, signal stability, p ower, load on nodes etc. can improve the quality and the relevance of the routes discovered for particular applications and con gurations. Along these lines, we explore the use of di erent security attributes to improve the quality of the security of an ad-hoc route. In this pap er, we present Security-Aware ad-hoc routing (SAR)”, an approach to routing that incorporates security levels of nodes into traditional routing metrics. Our goal is to characterize and explicitly represent the trust values and trust relationships associated with ad hoc nodes and use these values to make routing decisions. We quantify the notion of trust and represent the trust relationships explicitly by de ning a suitable hierarchy of trust values. Ensuring that data is routed through a secure route composed of trusted nodes is only one half of the problem. The second issue is the security of the information in the routing protocol messages. Since b oth data and control messages use the same wireless transmission medium, routing protocol messages can b e altered to change routing b ehavior. For example, if a routing protocol update can b e subverted, and the message altered in transit, no amount of security on data packets can mitigate routing misbehavior. In this paper, we also analyze the security of ad hoc routing algorithms with respect to the protection associated with the transmission of routing messages. One of the reasons for exposing security attributes at the routing level is to prevent attacks on the routing protocol itself, and thereby secure a fundamental building block of the ad hoc network infrastructure. We identify the attributes of a secure route and de ne appropriate metrics to quantify the “level of security” associated with the protocol messages. These metrics are adapted from their equivalents in security of wired routing protocols
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