Challenges of implementing cyber-physical security solutions in body area networks

Cyber-physical approach to securing Body Area Networks (BANs) provides solutions that are plug-n-play and transparent to its users. These Cyber-Physical Security Solutions (CPSS) actively involve characteristics from the physical environment. As a result they require a combination of signal processing (to extract features from the physical environment) and security primitives to function. In this paper we outline some of our experiences while implementing Plethysmogram based Key Agreement (PKA) a CPSS that uses Photoplethysmogram (PPG) based features for key agreement. Given the limited capabilities (computation, memory, power) of individual sensor nodes in a BAN, implementing CPSS for them is challenging. We therefore design Field Programmable Gate Array (FPGA) based hardware add-on for sensor nodes in a BAN, dedicated to execute PKA. The main contributions of this work are: 1) description of our experiences in implementation of PKA on FPGA platform; 2) identification of the design goals and trade-offs for validating implementation of CPSS; and 3) a discussion on the feasibility of a software implementation of PKA based on our experience gained from the FPGA prototyping.