Impact of Triggering-Probe-Connection on Evaluating Side-Channel Information Leakage from Cables

Side-channel information leakage on cables connected to cryptographic modules is a threat to cryptographic security because it increases the attack surface. Evaluation of side-channel leakage on cables can be difficult to reproduce because of the probe connection for triggering. When the trigger signal is output via GPIO and synchronized with the cryptographic process during encryption, side-channel leakage modulates the trigger signal, superimposes on it, and propagates to the power cable through the probe. However, since the trigger signal is not used during an actual attack, the results obtained with the evaluation environment may differ from those of actual attacks. The authors conducted a side-channel attack resistance evaluation through the common-mode current using ArmFrogs-ALICE, a general-purpose embedded board for industrial use, to investigate the effect of the triggering probe connection. As a result, it was confirmed that the probe connection induced the side-channel leakage in the common mode. We also demonstrated that the impact of the probe connection can be removed by sufficiently shifting the trigger pulse out of the duration of the cryptographic process.