Key generation based on fast reciprocal channel estimation for body-worn sensor nodes

With the advent of the Internet of Things, body-worn sensor nodes are continuously becoming more important. In case of bio-medical, rescue-worker or military applications sensitive data are often transmitted, requiring the need for encryption. The distribution of symmetric encryption keys is often an issue leading to security risks. Body-worn sensor nodes are generally employed in quickly varying channel conditions due to body movement. The radio-communication channel between such nodes is however reciprocal, allowing the extraction of an array of similar channel measurements at both ends of the link. These data can be used to build equal encryption keys at both link ends without the need for actual over-the-air key distribution. This paper studies the practical performance of an enhanced channel-based key generation system with a very short round-trip delay, allowing reciprocal channel assessment with increased accuracy. Measurements were performed using the new system and the results of the enhanced key generation are evaluated. Although the performance is slightly increased thanks to the shorter round-trip delay, the accuracy of the signal level detector still imposes limits.