Joint Encryption/Multiple Access for Body Area Sensor Networks

This paper addresses the security of the radio link in body area sensor networks (BASNs). Given that the well be- ing of a person or its privacy can be compromised, secu- rity in a BASN is of utmost importance. In this work, we take a joint encryption/multiple access approach. We use a direct-sequence spread spectrum (DSSS) multiple access technique to share a radio channel between multiple sensor nodes. Unlike standard DSSS techniques, in this work, the pseudo-noise (PN) code employed to spread the transmitted signal is changed on a bit-by-bit basis. This new PN code is generated by a non-linear feedback register. The register is initialized with a secret key. Not two radio links may use the same key at any given moment. The nodes begin communi- cation with each other by employing a publicly known PN code assignment. They exchange keys using the public PN codes and then switch into the non-linear, non-repeating PN code generation. The proposed method has the advantage of simultaneously securing the radio link and providing a means for different sensors to share the same radio channel. This joint approach results in circuit complexity and power savings.