Investigation on the Electromagnetic Radiated Emissions of a Single- Photon Avalanche Diode

The security provided by Quantum Key Distribution (QKD) can be strongly compromised by interception of the raw and sifted key through side channels, such as the practical characteristics of electronic components used in the transmitter and receiver modules. Some out-of-band electromagnetic attacks have already been identified and tested in components used in QKD, such as quantum random number generators. In this presentation, we explore out-of-band electromagnetic attacks of other components used in a quantum receiver, such as single photon avalanche diodes (SPADs), and the time-correlated single-photon counting module. We measured the electromagnetic (EM) radiated emissions of the components to quantify the emanation levels and evaluate the vulnerability that this QKD side channel may present. The test was conducted in an anechoic chamber up to 1 GHz, at 3 m distance, and rotating the SPAD to provide radiation from 4 azimuth angles. Results show that measurable radiated pulses are generated by the SPAD in this frequency range due to dark count pulses and due to incoming Single-Photon level pulses. Dark counts of few kHz and Single-Photon level counts of hundreds of kHz were considered in the tests. EM radiation frequency bands with main emissions and electric field strengths are identified for both operation conditions.