Robustness of Practical Perceptual Hashing Algorithms to Hash-Evasion and Hash-Inversion Attacks
Jordan Madden, Moxanki Bhavsar, Lhamo Dorje, Xiaohua Li
TL;DR
This paper evaluates the robustness of three practical perceptual hashing algorithms—PhotoDNA, PDQ, and NeuralHash—against hash-evasion and hash-inversion under realistic constraints. It introduces a query-efficient blackbox hash-evasion method, JSHA, and a data-efficient hash-inversion GAN, along with a defense based on random hash perturbation. Experiments across ImageNet, MNIST, CelebA, and STL-10 show substantial practical robustness, with targeted hash-evasion yielding near-zero success and inversion largely ineffective on diverse data; robustness is partly due to random hash variations. The random-hash-perturbation defense further reduces attack success and degrades inversion quality, offering a practical augmentation to PHAs in sensitive deployments.
Abstract
Perceptual hashing algorithms (PHAs) are widely used for identifying illegal online content and are thus integral to various sensitive applications. However, due to their hasty deployment in real-world scenarios, their adversarial security has not been thoroughly evaluated. This paper assesses the security of three widely utilized PHAs - PhotoDNA, PDQ, and NeuralHash - against hash-evasion and hash-inversion attacks. Contrary to existing literature, our findings indicate that these PHAs demonstrate significant robustness against such attacks. We provide an explanation for these differing results, highlighting that the inherent robustness is partially due to the random hash variations characteristic of PHAs. Additionally, we propose a defense method that enhances security by intentionally introducing perturbations into the hashes.
