PALLET: Protecting Analog Devices Using a Last-Level Edit Technique

For the past decade, hardware obfuscation has been a popular approach for protecting integrated circuits (ICs) against supply chain threats such as intellectual property (IP) piracy and overproduction. Despite this, the design of these techniques was originally for the digital domain and is not appropriate for analog circuits due to their intrinsic features, such as their small size. In this paper, we propose PALLET, a last-level edit (LLE) relying on a unique keyless obfuscation technique for pure analog and mixed-signal circuits to protect the design against untrusted foundries. In PALLET, design functionality is obfuscated by adding misleading (false) elements to the circuit layout based on design specifications and area overhead constraints. In PALLET, after fabrication of the LLEed (obfuscated) IC, the design house with a trusted focused-ion beam (FIB) facility performs the circuits edit at the top metal layers to de-obfuscate (remove LLE from) the IC with minimal effort. We also focus on a mathematical representation to show adversarial computation complexity based on the LLE framework. Finally, to validate the efficacy of LLE, we perform a security assessment against prominent attacks and compare post-layout performance parameters for a bandgap reference (BGR) design to demonstrate compliance with design specifications.