Inter-body coupling in electro-quasistatic human body communication: theory and analysis of security and interference properties

Abstract

Radiative communication using electromagnetic fields is the backbone of today’s wirelessly connected world, which implies that the physical signals are available for malicious interceptors to snoop within a 5–10 m distance, also increasing interference and reducing channel capacity. Recently, Electro-quasistatic Human Body Communication (EQS-HBC) was demonstrated which utilizes the human body’s conductive properties to communicate without radiating the signals outside the body. Previous experiments showed that an attack with an antenna was unsuccessful at a distance more than 1 cm from the body surface and 15 cm from an EQS-HBC device. However, since this is a new communication modality, it calls for an investigation of new attack modalities—that can potentially exploit the physics utilized in EQS-HBC to break the system. In this study, we present a novel attack method for EQS-HBC devices, using the body of the attacker itself as a coupling surface and capacitive inter-body coupling between the user and the attacker. We develop theoretical understanding backed by experimental results for inter-body coupling, as a function of distance between the subjects. We utilize this newly developed understanding to design EQS-HBC transmitters that minimizes the attack distance through inter-body coupling, as well as the interference among multiple EQS-HBC users due to inter-body coupling. This understanding will allow us to develop more secure and robust EQS-HBC based body area networks in the future.

Human Body–Electrode Interfaces for Wide-Frequency Sensing and Communication: A Review

“…Nevertheless, capacitive HBC is highly prone to external interferences as follows. In capacitive HBC, the SNR of the received signal depends on the strength of the parasitic capacitive coupling between the floating grounds of the transmitter and the receiver with the earth’s ground, i.e., the SNR of the received signal depends on and [ 98 , 99 ]. The higher their values, the higher the SNR of the received signal.…”

“…Further, since the signal return path in capacitive HBC is through the parasitic capacitances , , and , any source that can vary these capacitances can also act as a likely source for interference. Possible such sources include the presence of nearby wall wires, conductive objects, water, or humans [ 99 ]. The presence of grounded metallic objects in contact with the body is a strong source of interference.…”

On the Interaction of Biopotential Sensing and Right Leg Drive System with Electro-Quasistatic Human Body Communication

“…The transmitter uses these electrodes to generate fields inside the body and modulate their strengths to communicate data bits. The configuration results in electric field lines concentrating near the proximity of the transmitting node, reducing the signal strength to deteriorate with distance from the transmitter, limiting the transmission range [16]- [18].…”

A Quantitative Analysis of Physical Security and Path Loss With Frequency for IBOB Channel

“…Smart devices in and around the body are rapidly becoming an integral part of our lifestyle, with applications such as wearable and implantable remote health monitoring devices redefining the healthcare sector. Unfortunately these developments also imply an abundantly present communication of sensitive data around ourselves [1], [2]. Implantable Medical Devices like pacemakers and insulin pumps have been shown to be vulnerable to attacks resulting in fatal consequences (Fig.…”