This chapter explains the issues related to the security of a home healthcare system, from assurance and administration to authorization, accountability and availability. It provides a brief introduction to each of the security countermeasures. The chapter describes the general architecture and service platforms used for healthcare sensor systems. An efficient key establishment mechanism specifically for body sensors was created using physiological data. The first category of key establishment protocol is called the pairwise scheme. Random key predistribution schemes are the second category of key establishment protocols. Communication is the most expensive operation in sensor networks, where the received power drops off as the fourth power of distance mainly due to multipath propagation. Security and privacy concerns are impediments to health systems. The security mechanisms should enable real-time communication. Viruses, Trojan horses, root kits and software update failures are only several methods to modify the software in a home healthcare system.