Wireless Body Area Network (WBAN) uses Cryptographic Security for the protection of sensitive information stored and transmitted between body-worn devices (i.e. medical devices). Although Cryptographic Security is important, the WBAN needs to provide a reliable method of communicating and an efficient method of consuming energy in order to provide next-generation healthcare and wearable technologies, especially within the Medical/Nursing Industry, as well as assistive technology, such as sports monitoring solutions. Recently, continued advancements within the area of Energy Harvesting Technologies have enabled the WBAN to provide sustainable operation through the use of Energy Harvesting from Body Motion, Heat, and/or Ambient Sources, thereby extending the lifetime of a WBAN Network. Due to the random availability of harvested energy, however, IEEE 802.15.6 MAC protocol performance is impacted due to its emphasis on using a back-off strategy when “saturated.” This paper presents Discrete-Time Markov Chain (DTMC) Analytical Model for performance assessment of cryptographically protected IEEE 802.15.6 MAC protocols operating in Energy Harvesting WBANs. The Analytical Model was developed to include MAC Back-off behavior and the cryptographic processing overhead of the MAC protocol.