A Novel Interconnect Camouflaging Technique using Transistor Threshold Voltage

Semiconductor supply chain is increasingly getting exposed to variety of security attacks such as Trojan insertion, cloning, counterfeiting, reverse engineering (RE) and piracy of Intellectual Property (IP) due to involvement of untrusted parties. Camouflaging of gates has been proposed to hide the functionality of gates. However, gate camouflaging is associated with significant area, power and delay overhead. In this paper, we propose camouflaging of interconnects using multiplexers (muxes) to protect the IP. A transistor threshold voltage-defined pass transistor mux is proposed to prevent its reverse engineering since transistor threshold voltage is opaque to the adversary. The proposed mux with more than one input, hides the original connectivity of the net. The camouflaged design operates at nominal voltage and obeys conventional reliability limits. A small fraction of nets can be camouflaged to increase the RE effort extremely high while keeping the overhead low. We propose controllability, observability and random net selection strategy for camouflaging. Simulation results indicate 15-33% area, 25-44% delay and 14-29% power overhead when 5-15% nets are camouflaged using the proposed 2:1 mux. By increasing the mux size to 4:1, 8:1, and 16:1, the RE effort can be further improved with small area, delay, and power penalty.