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Alexander Levine

12 accepted papers

2025

Learning a Fast Mixing Exogenous Block MDP using a Single Trajectory

ICLR 2025poster

In order to train agents that can quickly adapt to new objectives or reward functions, efficient unsupervised representation learning in sequential decision-making environments can be important. Frameworks such as the Exogenous Block Markov Decision Process (Ex-BMDP) have been proposed to formalize…

2023

Provable Robustness against Wasserstein Distribution Shifts via Input Randomization

ICLR 2023poster

Certified robustness in machine learning has primarily focused on adversarial perturbations with a fixed attack budget for each sample in the input distribution. In this work, we present provable robustness guarantees on the accuracy of a model under bounded Wasserstein shifts of the data distributi…

Cited by 7SourcePDFScholar
2022

Segment and Complete: Defending Object Detectors Against Adversarial Patch Attacks With Robust Patch Detection

CVPR 2022poster

Object detection plays a key role in many security-critical systems. Adversarial patch attacks, which are easy to implement in the physical world, pose a serious threat to state-of-the-art object detectors. Developing reliable defenses for object detectors against patch attacks is critical but sever…

Cited by 111PDFcodeScholar
2021

Deep Partition Aggregation: Provable Defenses against General Poisoning Attacks

ICLR 2021poster

Adversarial poisoning attacks distort training data in order to corrupt the test-time behavior of a classifier. A provable defense provides a certificate for each test sample, which is a lower bound on the magnitude of any adversarial distortion of the training set that can corrupt the test sample's…

2020

(De)Randomized Smoothing for Certifiable Defense against Patch Attacks

NeurIPS 2020poster

Patch adversarial attacks on images, in which the attacker can distort pixels within a region of bounded size, are an important threat model since they provide a quantitative model for physical adversarial attacks. In this paper, we introduce a certifiable defense against patch attacks that guarante…

2020

Certifying Confidence via Randomized Smoothing

NeurIPS 2020poster

Randomized smoothing has been shown to provide good certified-robustness guarantees for high-dimensional classification problems. It uses the probabilities of predicting the top two most-likely classes around an input point under a smoothing distribution to generate a certified radius for a classifi…

2020

Curse of Dimensionality on Randomized Smoothing for Certifiable Robustness

ICML 2020poster

Randomized smoothing, using just a simple isotropic Gaussian distribution, has been shown to produce good robustness guarantees against $\ell_2$-norm bounded adversaries. In this work, we show that extending the smoothing technique to defend against other attack models can be challenging, especially…

2020

Dual Manifold Adversarial Robustness: Defense against Lp and non-Lp Adversarial Attacks

NeurIPS 2020poster

Adversarial training is a popular defense strategy against attack threat models with bounded Lp norms. However, it often degrades the model performance on normal images and more importantly, the defense does not generalize well to novel attacks. Given the success of deep generative models such as GA…

Cited by 70SourcePDFScholar
2020

Wasserstein Smoothing: Certified Robustness against Wasserstein Adversarial Attacks

AISTATS 2020poster

In the last couple of years, several adversarial attack methods based on different threat models have been proposed for the image classification problem. Most existing defenses consider additive threat models in which sample perturbations have bounded L_p norms. These defenses, however, can be vulne…

Cited by 66SourcePDFScholar