Functional obfuscation of digital circuits using observability don't care conditions

Abstract

Contemporary integrated circuits are designed and manufactured in a globalized environment leading to concerns of piracy, overproduction and counterfeiting. Obfuscation has emerged as a promising approach to ensure supply chain security by countering the reverse engineering (RE) based attacks on integrated circuits. However, the state-of-the-art obfuscation methods use key gates or camouflage existing gates which incur large design overhead and high cost of RE. In this paper, we propose a new obfuscation method based on don't care primitives that not only modifies the sub-circuit functionality but also can be implemented during design process at the cost of little area and delay overhead. Most of the existing obfuscation techniques focus on hiding layout information from circuit attackers, our approach not only obfuscates but alters sub-circuit level functionality in an attempt to make IP piracy difficult and to increase the RE complexity while fulfilling overall circuit specifications. An analysis of RE complexity is provided by functionally obfuscating ISCAS-85 Benchmarks. Our experimental results clearly indicate that significant RE complexity can be achieved at minimal design overhead (average area overhead is 5.436% and average delay overhead is about 7.473%).