Providing secrecy in key management protocols for large wireless sensors networks

This paper defines a new protocol KeEs for the key establishment that meets the security requirements of the threat model proposed. The KeEs protocol assures forward and backward secrecy of the session key, so that if any set of the session keys is compromised, even including the current session key, these compromised keys do not undermine neither the security of future session keys, nor the security of past session keys. We illustrate the protocol in two different scenarios, one in which a Base Station acts as a synchronizer for re-keying the sensors, and a second scenario based on a completely distributed approach where the sensors rely only on themselves to achieve synchronization in the re-keying process. For both scenarios the KeEs protocol requires minimal overhead in terms of computations and transmissions. Finally, in KeES none of the resources needed by a generic sensor is bounded to the size of the WSN.