Thwarting analog IC piracy via combinational locking

With a relatively small number of components, analog ICs are much more vulnerable to piracy, and especially reverse engineering, than many digital ICs. However, analog IC security has received much less research attention than digital ICs. We introduce a combinational locking technique using configurable current mirror for analog IC protection. The locking circuit is designed by applying Satisfiability Modulo Theories. With the locking system, only a single key value can make analog IC operate properly while the other key values result in significant performance degradation or malfunction. Moreover, circuit output is not monotone function with respect to key values and thus systematic attack is difficult to be effective. Experimental results demonstrate that this technique can largely thwart analog IC piracy with limited overhead.