Low-cost key management for hierarchical wireless vehicle networks

We have analyzed a hypothetical scenario for hierarchical wireless vehicle networks consisting of a central portal and a large number of vehicles. Vehicles join the network, establish connections to the portal, transfer data, and then leave the network. An efficient approach to provide authentication between a vehicle and the portal is to use the same pre-established symmetric link key for multiple occasions instead of performing a rigorous key agreement for every new occasion. However, since the same key is used for extended periods of time, the risk of cryptanalysis and offline bruteforcing of the link key increases. Therefore, there is a need to establish new keys between the portal and the vehicles (rekeying) in a secure and efficient manner. Moreover, to provide authenticity of the portal, the portal has a public and private key pair, and the public key is preinstalled in the vehicles. To reduce the risk of cryptanalysis of the private key of the portal, the public and private key pair of the portal must also be rekeyed. In this paper, we propose low-cost key management protocols for rekeying of the link keys and the public/private key pair of the portal.