Hardware Obfuscation of Digital FIR Filters
This addresses IP protection for designers of digital signal processing hardware, but it is incremental as it builds on existing obfuscation methods.
The paper tackles the problem of protecting intellectual property in digital FIR filters from reverse engineering by hiding coefficients among decoys, requiring a secret key for correct operation, and shows that the technique achieves competitive hardware complexity and higher attack resiliency compared to prior methods.
A finite impulse response (FIR) filter is a ubiquitous block in digital signal processing applications. Its characteristics are determined by its coefficients, which are the intellectual property (IP) for its designer. However, in a hardware efficient realization, its coefficients become vulnerable to reverse engineering. This paper presents a filter design technique that can protect this IP, taking into account hardware complexity and ensuring that the filter behaves as specified only when a secret key is provided. To do so, coefficients are hidden among decoys, which are selected beyond possible values of coefficients using three alternative methods. As an attack scenario, an adversary at an untrusted foundry is considered. A reverse engineering technique is developed to find the chosen decoy selection method and explore the potential leakage of coefficients through decoys. An oracle-less attack is also used to find the secret key. Experimental results show that the proposed technique can lead to filter designs with competitive hardware complexity and higher resiliency to attacks with respect to previously proposed methods.