Information Theoretic Analysis for Securing Next Generation Leadless Cardiac Pacemaker

Next generation of cardiac pacemakers are anticipated to be wireless that could lead to new security threats. This paper analyzes problem of secure data transmissions for future leadless cardiac pacemaker in terms of information theoretic security. Based on information theoretic approach for Gaussian broadcast channel, a communication channel can be secured if the legitimate receiver has better SNR than eavesdropper. By using attenuation as a key parameter this condition can be fulfilled for leadless cardiac pacemaker, assuming that legitimate receiver is always closer to leadless capsule than eavesdropper. In this work, capacity region for leadless cardiac pacemaker with and without secrecy constraints is characterized. Numerical results are obtained by setting different eavesdropping distance and finding corresponding secrecy transmission rates for legitimate receiver and eavesdropper by utilizing in-body channel model. Results also provide threat distance within which the eavesdropper must be to eavesdrop the communication which in turn depends on total power, information rates, and power distribution factor between legitimate receiver and eavesdropper. It has also been shown that by reducing total power, twofold advantages can be achieved, first it saves energy for low power implanted devices and second it helps increasing the secure zone but it comes with a cost of reduction in information rate. Numerical results are provided by using medical implant communication systems (MICS) band for communication between implanted devices. Similarly, it has also been shown that for certain fixed total power, power distribution factor, and transmission rate of 3.5 bps/channel, the threat zone can be reduced to as low as 400 mm.