SeFER: Secure, flexible and efficient routing protocol for distributed sensor networks

In this paper, we present a secure, flexible, and efficient routing protocol for sensor networks based on random key pre-distribution. Random key pre-distribution provides an easy way to manage the keys in a large-scale network without using public key cryptography, which is considered to be expensive. Our protocol aims to establish secure paths in a sensor network between a controller and a set of nodes where each node has been assigned a set of randomly chosen keys out of a key pool. A common model for sensor networks assumes a tree of sensor nodes delivering information to the controller according to an inquiry sent into the network. However, if we require the communication to be secure among the sensor nodes, such a tree cannot always be built efficiently. For example, when the nodes are assigned randomly chosen keys, many of them may not communicate directly since they do not often share a common key. However, these two nodes may communicate indirectly but securely over a multiple hop path where each pair of nodes on this path shares a common key. Our protocol bridges the gap between these two cases by providing the methods for nodes to securely share their keys and communicate directly so that the efficiency of communications is increased without jeopardizing the security. In this way, our protocol generates secure and efficient routes. We also provide simulation results for our protocol demonstrating that, for a small number of keys stored at each node, the average path length is smaller. However, the gains due to our protocol diminish as the number of available keys at each node increases since two nodes within communication range of each other are more likely to have a key in common.