Abstract
Ad hoc networks are a new wireless networking paradigm for mobile hosts. Unlike traditional mobilewireless networks, ad hoc networks do not rely on any fixed infrastructure. Instead, hosts rely on eachother to keep the network connected. The military tactical and other security-sensitive operations arestill the main applications of ad hoc networks, although there is a trend to adopt ad hoc networksfor commercial uses due to their unique properties. One main challenge in design of these networks istheir vulnerability to security attacks. In this paper, we study the threats an ad hoc network faces andthe security goals to be achieved. We identify the new challenges and opportunities posed by this newnetworking environment and explore new approaches to secure its communication. In particular, we takeadvantage of the inherent redundancy in ad hoc networks — multiple routes between nodes — to defendrouting against denial of service attacks. We also use replication and new cryptographic schemes, suchas threshold cryptography, to build a highly secure and highly available key management service, whichforms the core of our security framework.
1 Introduction
Ad hoc networks are a new paradigm of wireless communication for mobile hosts (which we call nodes). Inan ad hoc network, there is no fixed infrastructure such as base stations or mobile switching centers. Mobilenodes that are within each other’s radio range communicate directly via wireless links, while those thatare far apart rely on other nodes to relay messages as routers. Node mobility in an ad hoc network causesfrequent changes of the network topology. Figure 1 shows such an example: initially, nodes A and D have adirect page link between them. When D moves out of A’s radio range, the page link is broken. However, the networkis still connected, because A can reach D through C, E, and F.Military tactical operations are still the main application of ad hoc networks today. For example, militaryunits (e.g., soldiers, tanks, or planes), equipped with wireless communication devices, could form an ad hocnetwork when they roam in a battlefield. Ad hoc networks can also be used for emergency, law enforcement,and rescue missions. Since an ad hoc network can be deployed rapidly with relatively low cost, it becomesan attractive option for commercial uses such as sensor networks or virtual classrooms.
1.1 Security goals
Security is an important issue for ad hoc networks, especially for those security-sensitive applications. Tosecure an ad hoc network, we consider the following attributes: availability, confidentiality, integrity, authentication,and non-repudiation._To be published in IEEE network, special issue on network security, November/December, 1999. This work is supported inpart by ARPA/RADC grant F30602-96-1-0317, AFOSR grant F49620-94-1-0198, Defense Advanced Research Projects Agency(DARPA) and Air Force Research Laboratory, Air Force Material Command, USAF, under agreement number F30602-99-1-0533, and National Science Foundation Grants 9703470, ANI-9805094, and NCR-9704404. The views and conclusions containedherein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements,either expressed or implied, of these organizations or the U.S. Government. The U.S. Government is authorized to reproduceand distribute reprints for Government purposes notwithstanding any copyright annotation thereon.


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