The increasing interest in the usage of wireless body area networks (WBAN) in healthcare and other critical applications underscores the importance of secure communications among the body sensor devices. One of the major challenges in
WBAN is the association of an unkown device with an existing network without prior knowledge of a secret key. The state-of-the-art authentication mechanisms for WBAN typically rely on the received signal strength (RSS). However, RSS-based methods
employing a single antenna are susceptible to environmental factors and an adversary can easily mount an attack by varying the transmission power. We present SeAK, the first secure lightweight device pairing protocol for WBAN based on the RSS
obtained by dual-antenna transceivers utilizing spatial diversity. With spatially separated antennas, the RSS values from a nearby device are large and distinct, as opposed to those from a far-away device. SeAK authenticates a legitimate device and generates
shared secret key simultaneously. We implement our SeAK prototype on the Opal sensor platform having RF231 radio that is compatible for communication in 2.4 GHz. We demonstrate that our protocol is able to achieve a 100% success acceptance
rate, securely authenticate a nearby device and generate a 128-bit secret key in 640ms, as opposed to 15.9 seconds in other recent RSS-based schemes (e.g. ASK-BAN).
This work is partially supported by Australian Research Council Discovery grant DP150100564.