A Fundamental Evaluation of EM Information Leakage Induced by IEMI for a Device with Differential Signaling

The threat of electromagnetic (EM) information leakage induced by intentional electromagnetic interference (IEMI) for single-ended signals has been reported. The intensity of the leaked EM waves can be controlled by the intensity of the induced disturbance waves. If the EM information leakage method can be applied to other signaling schemes, more devices would be threatened. As a result, countermeasures need to be taken. This study shows that the threat of EM information leakage induced by IEMI exists in other signaling schemes, using universal serial bus (USB) 2.0 devices, one of the differential signaling standards. Specifically, using a USB keyboard as an evaluation target, we demonstrate that the output impedance of the IC changes according to its output states, causing fluctuations in the amplitude of the reflected waves. As a result, we confirm that the differential signal is leaked by demodulating the amplitude of the reflected waves.