PROM: Protection against Reverse Engineering Attacks through Programmable Logic Macros

The modern supply chain ecosystem exposes hardware intellectual property (IP) blocks to diverse confidentiality attacks aimed at reverse engineering (RE), piracy, or the extraction of design secrets. An emerging and potent design solution for IP protection against these attacks, particularly against RE, is the fine-grained redaction of security-critical logic and replacing the redacted logic with lookup tables (LUTs). The LUTs are then programmed in-field, similar to FPGAs, using protected bitstreams, thereby preventing untrusted foundries or test/assembly facilities from mounting RE attacks. The LUT-based redaction paradigm incurs a substantial hardware cost, with area overhead ranging from 70x to 100x and delay overhead from 2x to 5x, while also often necessitating significant alterations to the commercial tool flow for design, verification, and testing. In this work, we propose PROM, a robust fine-grain redaction technique inspired by structured ASIC, that aims to address the limitations of LUT-based redaction with novel overhead optimizations. The redacted security-critical logic is implemented using a library of custom-design PROM cells that are optimized to minimize overheads compared to state-of-the-art redaction techniques while providing strong protection against various RE attacks. We evaluated the proposed redaction technique across a range of open-source benchmarks, achieving robust security with average overheads of 1.42x in area and 1.09x in delay, demonstrating its efficiency and practicality.