Reversible Circuits: IC/IP Piracy Attacks and Countermeasures

Reversible circuits employ a computing paradigm that is useful in a broad variety of applications. With increasing interest, security concerns for those circuits also will rise in the near future. At first glance, reversible circuits seem to be more secure to integrated circuit (IC)/intellectual property (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 article, we perform an analysis of the IC/IP piracy attacks on reversible circuits. We focus on the reversible circuits generated by the quantum multivalued decision diagram (QMDD)- and binary decision diagram (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.