Securing inductively-coupled communication

Communication over inductively-coupled links is becoming prevalent in service delivery for medical, financial, and physical security applications and so there is a growing need to prevent eavesdropping. This paper presents circuit-theoretic and communication-theoretic models of inductively-coupled communication systems. Due to coupling, the presence of an eavesdropper detunes the transfer function between the legitimate users. It is shown this detuning can be detected to reveal the presence of the eavesdropper. Further, if capacity-approaching codes are employed, neither the eavesdropper nor the legitimate receiver are able to reconstruct the transmitted message with low error probability, effectively destroying the message. Building on this insight, a coding-based secure communication protocol for inductively-coupled communication, inspired by quantum key distribution, is developed. The notion of security is defined operationally in terms of probabilities rather than through traditional notions of equivocation.