Ad hoc networks rely on the cooperation of the nodes participating in the network to forward packets for each other. A node may decide not to cooperate to save its resources while still using the network to relay its traffic. If too many nodes exhibit this behavior, network performance degrades and cooperating nodes may find themselves unfairly loaded. Most previous efforts to counter this behavior have relied on further cooperation between nodes to exchange reputation information about other nodes. If a node observes another node not participating correctly, it reports this observation to other nodes who then take action to avoid being affected and potentially punish the bad node by refusing to forward its traffic. Unfortunately, such second-hand reputation information is subject to false accusations and requires maintaining trust relationships with other nodes. The objective of OCEAN is to avoid this trust-management machinery and see how far we can get simply by using direct first-hand observations of other nodes' behavior. We find that, in many scenarios, OCEAN can do as well as, or even better than, schemes requiring second-hand reputation exchanges. This encouraging result could possibly help obviate solutions requiring trust-management for some contexts.
The problem of securing the routing layer using cryptographically secure messages is addressed by @cite_13 @cite_5 , Papadimitratos and Haas @cite_3 , and @cite_1 . Schemes to handle authentication in ad hoc networks assuming trusted Certificate Authorities have been proposed by Zhou and Haas @cite_7 , and @cite_6 . @cite_15 employ a self-organized PGP-based scheme to authenticate nodes using chains of certificates and transitivity of trust. Stajano and Anderson @cite_17 authenticate users by imprinting,' in analogy to ducklings acknowledging the first moving subject they see as their mother. In OCEAN, we do not attempt to secure the routing layer, although our techniques may be used in conjunction with many secure routing protocols to increase performance and robustness.
@cite_7 @cite_1 @cite_3 @cite_6 @cite_5 @cite_15 @cite_13 @cite_17
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Today's Internet routing protocols are built upon the basic incorrect assumption that routers propagate truthful routing information. As a result, the entire Internet infrastructure is vulnerable to security attacks from routers that propagate incorrect routing information. In fact, a single router is capable of hijacking a significant fraction of routes by launching such an attack. This issue is not just restricted to Internet routing protocols but is widely prevalent in several routing protocols that have been proposed in the research literature. Many existing approaches for addressing the security problems of routing protocols typically assume the existence of a Public-Key Infrastructure (PKI) or some form of prior key distribution mechanism along with a central authority. While a PKI does enable addressing this security threat, building one such key-distribution infrastructure may not always be feasible. One faces serious deployment barriers in building an Internet-wide PKI with a central authority especially given that deploying one such architecture requires approval across political and economic boundaries. Previous efforts for securing Internet routing and the Domain Name System using a PKI have not moved towards adoption. In this dissertation, we address the following question: Using purely decentralized mechanisms (void of a PKI and a central authority), what is the best level of security achievable for a routing protocol in the presence of adversaries? One of the key conclusions that we arrive at is the direct relationship between decentralized security and the reliable communication problem. The reliable communication problem relates to determining the constraints under which a set of good nodes in a network can reliably communicate messages between themselves in the face of adversarial nodes in the network. We show theoretical results on the constraints under which the reliable communication problem is solvable. Based on these results, we describe the design of a reliable communication toolkit that implements our algorithms and provides a suite of generic security primitives that can be used to secure a variety of routing protocols. These security mechanisms supported by the toolkit are well suited for Internet routing since they are both easy to deploy as well as offer good security guarantees. We also show that the toolkit has broader applicability beyond routing protocols to: (a) achieve decentralized key distribution; (b) address the data integrity threat to the Domain Name System (DNS) in a decentralized manner. Authentication using a path of trusted intermediaries, each able to authenticate the next in the path, is a well-known technique for authenticating channels in a large distributed system. In this paper, we explore the use of multiple paths to redundantly authenticate a channel and focus on two notions of path independence-disjoint paths and connective paths-that seem to increase assurance in the authentication. We give evidence that there are no efficient algorithms for locating maximum sets of paths with these independence properties and propose several approximation algorithms for these problems. We also describe a service we have deployed, called PathServer, that makes use of our algorithms to find such sets of paths to support authentication in PGP applications. The emergence of the Mobile Ad Hoc Networking (MANET) technology advocates self-organized wireless interconnection of communication devices that would either extend or operate in concert with the wired networking infrastructure or, possibly, evolve to autonomous networks. In either case, the proliferation of MANET-based applications depends on a multitude of factors, with trustworthiness being one of the primary challenges to be met. Despite the existence of well-known security mechanisms, additional vulnerabilities and features pertinent to this new networking paradigm might render such traditional solutions inapplicable. In particular, the absence of a central authorization facility in an open and distributed communication environment is a major challenge, especially due to the need for cooperative network operation. In particular, in MANET, any node may compromise the routing protocol functionality by disrupting the route discovery process. In this paper, we present a route discovery protocol that mitigates the detrimental effects of such malicious behavior, as to provide correct connectivity information. Our protocol guarantees that fabricated, compromised, or replayed route replies would either be rejected or never reach back the querying node. Furthermore, the protocol responsiveness is safeguarded under different types of attacks that exploit the routing protocol itself. The sole requirement of the proposed scheme is the existence of a security association between the node initiating the query and the sought destination. Specifically, no assumption is made regarding the intermediate nodes, which may exhibit arbitrary and malicious behavior. The scheme is robust in the presence of a number of non-colluding nodes, and provides accurate routing information in a timely manner. A mobile ad hoc network consists of mobile nodes that can move freely in an open environment. Communicating nodes in a wireless and mobile ad hoc network usually seek the help of other intermediate nodes to establish communication channels. In such an open environment, malicious intermediate nodes can be a threat to the security and or anonymity of the exchanged data between the mobile nodes. While data encryption can protect the content exchanged between nodes, routing information may reveal valuable information about end users and their relationships. The main purposes of this paper are to study the possibility of achieving anonymity in ad hoc networks, and propose an anonymous routing protocol, similar to onion routing concept used in wired networks. Our protocol includes a mechanism to establish a trust among mobile nodes while avoiding untrustworthy nodes during the route discovery process. The major objective of our protocol is to allow only trustworthy intermediate nodes to participate in the routing protocol without jeopardizing the anonymity of the communicating nodes. We present our scheme, and report on its performance using an extensive set of simulation set of experiments using ns-2 simulator. Our results indicate clearly that anonymity can be achieved in mobile ad hoc networks, and the additional overhead of our scheme to DSR is reasonably low when compared to a non-secure DSR ad hoc routing protocol.