DNA: DC Nodal Analysis Attack for Analog Circuits

Algorithms have been proposed to evaluate the resiliency of analog obfuscation techniques. Each analog deobfuscation algorithm considers different threat models, applies to only a small set of obfuscation techniques, and suffers adversely under real world scenarios, where one or more pieces of information on the circuit and obfuscation technique or techniques is unavailable to the attacker. In this paper, a novel DC nodal analysis (DNA) attack algorithm is proposed that requires only the circuit netlist and the DC input-output response of the oracle IC to perform the attack. The DNA attack utilizes Kirchhoff’s voltage law (KVL) and Kirchhoff’s current law (KCL) to efficiently characterize an obfuscated analog circuit with the objective of determining the correct locked parameters. A preliminary evaluation of the proposed attack is performed on three distinct analog circuits secured using both key-based parameter obfuscation and non-key-based multi-threshold obfuscation. The results from executing the attack on a secured single-stage analog circuit with key-based obfuscation indicate the successful elimination of, on average, 96% of keys from the search space. The results from executing the attack on two-stage circuits secured with multi-threshold obfuscation indicate that 99.58% of the keys are eliminated in less than 7 hours. With the limited information necessary to perform the attack, the efficiency in pruning the key-space when considering real attack scenarios, and the application of the attack to all current analog obfuscation techniques, the DNA attack provides the de-facto standard in the characterization of the resiliency of an analog obfuscated circuit.