DK Lock: Dual Key Logic Locking Against Oracle-Guided Attacks

The semiconductor industry must deal with different hardware threats like piracy and overproduction as a result of outsourcing manufacturing. While there are many proposals to lock the circuit using a global protected key only known to the designer, there exist numerous oracle-guided attacks that can examine the locked netlist with the assistance of an activated IC and extract the correct key. In this paper, by adopting a low-overhead structural method, we propose DK Lock, a novel Dual Key locking method that securely protects sequential circuits with two different keys that are applied to one set of key inputs at different times. DK Lock structurally adds an activation phase to the sequential circuit, and a correct key must be applied for several cycles to exit this phase. Once the circuit has been successfully activated, a new functional key must be applied to the same set of inputs to resume normal operation. DK Lock opens up new avenues for hardware IP protection by simultaneously refuting the single static key assumption of the existing attacks and overcoming the state explosion problem of state-of-the-art sequential logic locking methods. Our experiments confirm that DK Lock maintains a high degree of security with reasonable power and area overheads.