Secure key loss recovery for network broadcast in single-hop wireless sensor networks

Symmetric encryption of data at the base-station using time-varying keys has been proposed as an attractive method for securing broadcasts in wireless sensor networks: symmetric decryption keeps computational costs at sensor nodes low, while time-varying group keys protect the network against key compromise at any of the receivers. However, a significant problem is that interference or disconnections may cause a receiver to miss broadcast packets and the dynamic keys contained therein, rendering it unable to participate in subsequent broadcasts. In this paper, we develop a scheme which allows receivers to recover from key loss in a secure, efficient, and scalable manner. Our scheme appends recovery information to each broadcast message to help out-of-sync receivers reattach probabilistically using an older key. We analyze our scheme to quantify the recovery probability as a function of system parameters, and deduce fundamental asymptotic bounds on recovery. We further prototype our scheme on the MicaZ mote platform and show that it is lightweight and efficient. Our solution offers a highly configurable, efficient and scalable method for key recovery in large sensor networks that require secure broadcasts.