  Various side-channel attacks (SCAs) on ICs have been successfully
demonstrated and also mitigated to some degree. In the context of 3D ICs,
however, prior art has mainly focused on efficient implementations of classical
SCA countermeasures. That is, SCAs tailored for up-and-coming 3D ICs have been
overlooked so far. In this paper, we conduct such a novel study and focus on
one of the most accessible and critical side channels: thermal leakage of
activity and power patterns. We address the thermal leakage in 3D ICs early on
during floorplanning, along with tailored extensions for power and thermal
management. Our key idea is to carefully exploit the specifics of material and
structural properties in 3D ICs, thereby decorrelating the thermal behaviour
from underlying power and activity patterns. Most importantly, we discuss
powerful SCAs and demonstrate how our open-source tool helps to mitigate them.
