Figure 1

Inter-body coupling in Electro-quasistatic region: (a) Interference in received EQS-HBC signal due to inter-body coupling with other users. For multiple EQS-HBC users in close proximity, the received signal is usable only if the interference signal is a few dB lower than the signal. (b) While EQS-HBC devices restrict EM leakage within 10 cm of the user’s body, inter-body capacitive coupling can give rise to a new attack modality, where the attacker’s body is used to capacitively couple to the user’s body, and the coupled signal is picked up using an EQS-HBC receiver. (c) For devices that do not restrict EM leakage, such as Bluetooth or other WBAN devices, the signal can be picked up by an attacking device with an antenna within 5–10 m of the user. The human figures were created using the open-source software ‘MakeHuman’¹².