SeAK: Secure Authentication and Key Generation Protocol Based on Dual Antennas for Wireless Body Area Networks

The increasing interest in the usage of wireless body area networks (WBAN) in healthcare and other critical applications underscores the importance of secure communication among the body sensor devices. Associating an unknown device with an existing network without prior knowledge of a secret key poses a major challenge. Existing authentication schemes in WBAN are typically based on received signal strength (RSS). However, RSS techniques using a single antenna are susceptible to environmental factors and are vulnerable to attacks that use variable transmission power. We present SeAK, the first secure light-weight device pairing protocol for WBAN based on 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 exploits this effect to accomplish authentication and shared secret key generation simultaneously. We have implemented a prototype of SeAK on the Opal sensor platform with a 2.4GHz compatible RF231 radio. 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 s in other recent RSS-based schemes (e.g. ASK-BAN).