The protocols we reviewed in Section 16.2.2 were designed for nonadversarial environments, where the node within a network are nonmalicious, unselfish, and well-behaving. The reality, however, is that in any network, there are likely to be malicious or selfish, miss-behaving nodes that have intentions of disrupting the routing protocol. Security mechanisms are therefore necessary to mitigate against these eventualities. This section reviews some of the routing security schemes that have been proposed to address the security shortcomings of these protocols. For the purpose of the review, we categorized the existing secure MANET routing proposals into the following categories: basic routing security schemes, trust-based routing schemes, incentive-based schemes, and schemes that employ detection and isolation mechanisms. Below, we briefly describe a selection of schemes that fall in these categories.
The routing schemes that fall in this category provide authentication services that guard against modification and replaying of routing control messages, but they do not attempt to provide solutions for issues such as the dropping of packets by selfish or malicious nodes. We commence the review with one of the earlier proposals.