Beyond their impressive sampling capabilities, score-based diffusion models offer a powerful analysis tool in the form of unbiased density estimation of a query sample under the training data distribution. In this work, we investigate the robustness of density estimation using the probability flow (PF) neural ordinary differential equation (ODE) model against gradient-based likelihood maximization attacks and the relation to sample complexity, where the compressed size of a sample is used as a measure of its complexity. We introduce and evaluate six gradient-based log-likelihood maximization attacks, including a novel reverse integration attack. Our experimental evaluations on CIFAR-10 show that density estimation using the PF ODE is robust against high-complexity, high-likelihood attacks, and that in some cases adversarial samples are semantically meaningful, as expected from a robust estimator.
@article{arxiv.2310.07084,
title = {Investigating the Adversarial Robustness of Density Estimation Using the Probability Flow ODE},
author = {Marius Arvinte and Cory Cornelius and Jason Martin and Nageen Himayat},
journal= {arXiv preprint arXiv:2310.07084},
year = {2023}
}