Reversible Circuits: IC/IP Piracy Attacks and Countermeasures

Reversible circuits employ a computing paradigm which is useful in a broad variety of applications. With increasing interest, also security concerns for those circuits will raise in the near future. At first glance, reversible circuits seem to be more secure to IC/IP piracy than conventional circuits since the target function is usually embedded in the reversible backbone circuit. This embedding adds ancillary inputs and garbage outputs that may appear to hide the target function. However, recent work showed that target function embedding and reversible synthesis methods leave telltale signs in the reversible circuits which allow for an easy extraction of the synthesis approach and the embedded circuit. In this paper, we perform an analysis of the IC/IP piracy attacks on reversible circuits. We focus on reversible circuits generated using QMDD- and BDD-based synthesis approaches as case studies. We show that most of the target function can be identified using the telltale signs of the synthesis approach. We then propose a cost-effective input/output scrambling scheme that wipes out these telltale signs, and thus, thwarts the considered attacks by adding reversible gates. Those additional gates yield efficient yet secure reversible circuits.