GRILL: Restoring Gradient Signal in Ill-Conditioned Layers for More Effective Adversarial Attacks on Autoencoders

Fuente: arXiv
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Autores principales: Ramanaik, Chethan Krishnamurthy, Roy, Arjun, Callies, Tobias, Ntoutsi, Eirini
Formato: Preprint
Publicado: 2025
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author Ramanaik, Chethan Krishnamurthy
Roy, Arjun
Callies, Tobias
Ntoutsi, Eirini
author_facet Ramanaik, Chethan Krishnamurthy
Roy, Arjun
Callies, Tobias
Ntoutsi, Eirini
contents Adversarial robustness of deep autoencoders (AEs) has received less attention than that of discriminative models, although their compressed latent representations induce ill-conditioned mappings that can amplify small input perturbations and destabilize reconstructions. Existing white-box attacks for AEs, which optimize norm-bounded adversarial perturbations to maximize output damage, often stop at suboptimal attacks. We observe that this limitation stems from vanishing adversarial loss gradients during backpropagation through ill-conditioned layers, caused by near-zero singular values in their Jacobians. To address this issue, we introduce GRILL, a technique that locally restores gradient signals in ill-conditioned layers, enabling more effective norm-bounded attacks. Through extensive experiments across multiple AE architectures, considering both sample-specific and universal attacks under both standard and adaptive attack settings, we show that GRILL significantly increases attack effectiveness, leading to a more rigorous evaluation of AE robustness. Beyond AEs, we provide empirical evidence that modern multimodal architectures with encoder-decoder structures exhibit similar vulnerabilities under GRILL.
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spellingShingle GRILL: Restoring Gradient Signal in Ill-Conditioned Layers for More Effective Adversarial Attacks on Autoencoders
Ramanaik, Chethan Krishnamurthy
Roy, Arjun
Callies, Tobias
Ntoutsi, Eirini
Machine Learning
Artificial Intelligence
Computer Vision and Pattern Recognition
Adversarial robustness of deep autoencoders (AEs) has received less attention than that of discriminative models, although their compressed latent representations induce ill-conditioned mappings that can amplify small input perturbations and destabilize reconstructions. Existing white-box attacks for AEs, which optimize norm-bounded adversarial perturbations to maximize output damage, often stop at suboptimal attacks. We observe that this limitation stems from vanishing adversarial loss gradients during backpropagation through ill-conditioned layers, caused by near-zero singular values in their Jacobians. To address this issue, we introduce GRILL, a technique that locally restores gradient signals in ill-conditioned layers, enabling more effective norm-bounded attacks. Through extensive experiments across multiple AE architectures, considering both sample-specific and universal attacks under both standard and adaptive attack settings, we show that GRILL significantly increases attack effectiveness, leading to a more rigorous evaluation of AE robustness. Beyond AEs, we provide empirical evidence that modern multimodal architectures with encoder-decoder structures exhibit similar vulnerabilities under GRILL.
title GRILL: Restoring Gradient Signal in Ill-Conditioned Layers for More Effective Adversarial Attacks on Autoencoders
topic Machine Learning
Artificial Intelligence
Computer Vision and Pattern Recognition
url https://arxiv.org/abs/2505.03646