Aging Effects on Template Attacks Launched on Dual-Rail Protected Chips

Profiling side-channel attacks in which an adversary creates a "profile" of a sensitive device and uses such a profile to model a target device with similar implementation has received the lion's share of attention in the recent years. In particular, template attacks are known to be the most powerful profiling side-channel attacks from an information theoretic point of view. When launching such an attack, the adversary first builds a model based on the leakage of the profiling (training) device in his disposal, which is then exploited in the second phase of the attack (i.e., matching) to extract the key from the target device. Discrepancies between the device used for modeling and the target device affect the attack success. The effect of process variation and temperature misalignment between the profiling and target devices in the template attack's success has been studied extensively in the literature, while the impact of device aging on the template attack's success is yet to be investigated thoroughly. This article moves one step forward and studies the impact of device aging, mainly bias temperature instability (BTI) and hot carrier injection (HCI), in the devices that have been protected against power analysis attacks via dual rail logics. In particular, we focus on the wave dynamic differential logic (WDDL) circuits, and via extensive transistor-level simulations, we will show how device aging misalignments between the profiling and target devices can hinder template attacks for both unprotected and WDDL protected counterparts. We mounted several attacks on the PRESENT cipher, with and without WDDL protection, at different temperatures and aging times. Our results show that the attack is more difficult if there is an aging-duration mismatch between the training and target devices, and the attack-efficiency decrease is especially significant for mismatches of few weeks.