Authenticated Key Establishment Protocols for a Home Health Care System

Wireless sensor networks provide solutions to a range of monitoring problems. However, they also introduce a new set of problems mainly due to small memories, weak processors, limited energy and small packet size. Thus only a very few conventional protocols can readily be used in sensor networks. Sensor networks can exist in many different environments, and each environment has its own unique characteristics and requirements. As an example application, a home health care system is proposed and examined in detail in this paper. We show how cryptographically weak physiological data can be used to establish keys between body sensors, where the sensors have no other prior secret. This paper also proposes a protocol where a hand held device, such as a PDA, can establish a key with the majority of sensors found in our home health care system. This is achieved without the necessity of using traditional encryption. Detailed analysis of each of the protocols is provided. The protocols were implemented in TinyOS and simulated using TOSSIM and ATEMU. Energy consumption and memory requirements are analysed and it was found that an RSA implementation of our protocols has some advantages over an ECC implementation.