Hybrid Protection of Digital FIR Filters

TL;DR

This paper introduces a hybrid hardware obfuscation and logic locking technique to enhance the security of digital FIR filters, making them resilient against advanced attacks while maintaining hardware efficiency.

Contribution

It presents the first hybrid protection method combining hardware obfuscation and logic locking specifically for FIR filters, improving security against query attacks.

Findings

Hybrid protection increases FIR filter security.

Protected filters resist existing attacks.

Parallel direct form FIR filters show promising security potential.

Abstract

A digital Finite Impulse Response (FIR) filter is a ubiquitous block in digital signal processing applications and its behavior is determined by its coefficients. To protect filter coefficients from an adversary, efficient obfuscation techniques have been proposed, either by hiding them behind decoys or replacing them by key bits. In this article, we initially introduce a query attack that can discover the secret key of such obfuscated FIR filters, which could not be broken by existing prominent attacks. Then, we propose a first of its kind hybrid technique, including both hardware obfuscation and logic locking using a point function for the protection of parallel direct and transposed forms of digital FIR filters. Experimental results show that the hybrid protection technique can lead to FIR filters with higher security while maintaining the hardware complexity competitive or superior to those locked by prominent logic locking methods. It is also shown that the protected multiplier blocks and FIR filters are resilient to existing attacks. The results on different forms and realizations of FIR filters show that the parallel direct form FIR filter has a promising potential for a secure design.