Handling Reboots and Mobility in 802.15.4 Security

Abstract

To survive reboots, 802.15.4 security normally requires an 802.15.4 node to store both its anti-replay data and its frame counter in non-volatile memory. However, the only non-volatile memory on most 802.15.4 nodes is flash memory, which is energy consuming, slow, as well as prone to wear. Establishing session keys frees 802.15.4 nodes from storing anti-replay data and frame counters in non-volatile memory. For establishing pairwise session keys for use in 802.15.4 security in particular, Krentz et al. proposed the Adaptable Pairwise Key Establishment Scheme (APKES). Yet, APKES neither supports reboots nor mobile nodes. In this paper, we propose the Adaptive Key Establishment Scheme (AKES) to overcome these limitations of APKES. Above all, AKES makes 802.15.4 security survive reboots without storing data in non-volatile memory. Also, we implemented AKES for Contiki and demonstrate its memory and energy efficiency. Of independent interest, we resolve the issue that 802.15.4 security stops to work if a node's frame counter reaches its maximum value, as well as propose a technique for reducing the security-related per frame overhead.