  Logic locking and hardware Trojans are two fields in hardware security that
have been mostly developed independently from each other. In this paper, we
identify the relationship between these two fields. We find that a common
structure that exists in many logic locking techniques has desirable properties
of hardware Trojans (HWT). We then construct a novel type of HWT, called
Trojans based on Logic Locking (TroLL), in a way that can evade
state-of-the-art ATPG-based HWT detection techniques. In an effort to detect
TroLL, we propose customization of existing state-of-the-art ATPG-based HWT
detection approaches as well as adapting the SAT-based attacks on logic locking
to HWT detection. In our experiments, we use random sampling as reference. It
is shown that the customized ATPG-based approaches are the best performing but
only offer limited improvement over random sampling. Moreover, their efficacy
also diminishes as TroLL's triggers become longer, i.e., have more bits
specified). We thereby highlight the need to find a scalable HWT detection
approach for TroLL.
