High-level Intellectual Property Obfuscation via Decoy Constants

TL;DR

This paper introduces a circuit obfuscation method that uses decoy constants and key schemes to protect intellectual property in circuits relying on constant multiplications, making reverse engineering more difficult with minimal hardware overhead.

Contribution

It proposes a novel high-level obfuscation technique focusing on constants in circuits, enhancing IP protection against reverse engineering at minimal overhead.

Findings

Obfuscation effectively prevents IP theft in constant multiplication circuits.

The method incurs small area, power, and delay overheads.

Vulnerabilities to SAT and ATPG attacks are analyzed and mitigated.

Abstract

This paper presents a high-level circuit obfuscation technique to prevent the theft of intellectual property (IP) of integrated circuits. In particular, our technique protects a class of circuits that relies on constant multiplications, such as filters and neural networks, where the constants themselves are the IP to be protected. By making use of decoy constants and a key-based scheme, a reverse engineer adversary at an untrusted foundry is rendered incapable of discerning true constants from decoy constants. The time-multiplexed constant multiplication (TMCM) block of such circuits, which realizes the multiplication of an input variable by a constant at a time, is considered as our case study for obfuscation. Furthermore, two TMCM design architectures are taken into account; an implementation using a multiplier and a multiplierless shift-adds implementation. Optimization methods are also applied to reduce the hardware complexity of these architectures. The well-known satisfiability (SAT) and automatic test pattern generation (ATPG) attacks are used to determine the vulnerability of the obfuscated designs. It is observed that the proposed technique incurs small overheads in area, power, and delay that are comparable to the hardware complexity of prominent logic locking methods. Yet, the advantage of our approach is in the insight that constants -- instead of arbitrary circuit nodes -- become key-protected.