Exploiting Heterogeneity for Sensor Network Security

Many sensor network deployments are heterogeneous: a large number of regular nodes perform sensing, while some nodes have better energy resources and/or more computational capacity. Whereas the effect of heterogeneous nodes on network reliability and lifetime has been studied [3], we here focus on exploiting heterogeneity for security. For security and privacy, the identity of nodes must be authenticated and keys have to be distributed. In our lightweight end-middle-end security framework, every node has a public/private key pair, but only resource-rich gateway nodes use public key cryptography to compute digital signatures. Since gateway nodes vouch for regular nodes, regular nodes can use symmetric cryptography until a gateway is reached. On regular nodes, this reduces energy consumption and processing delays by more than a factor of 3000. Re-encryption on the gateways is typically not the bottleneck, since gateways are often line-powered and typically more than 100 times faster than regular nodes (e.g. Stargate vs. Mica). An additional advantage of our end-middle-end architecture is that only gateways are affected by changes in user privileges.