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Title: Improving the Generalization of Adversarial Training with Domain Adaptation

Paper content:
By injecting adversarial examples into training data, adversarial training is promising for improving the robustness of deep learning models.
However, most existing adversarial training approaches are based on a specific type of adversarial attack.
It may not provide sufficiently representative samples from the adversarial domain, leading to a weak generalization ability on adversarial examples from other attacks.
Moreover, during the adversarial training, adversarial perturbations on inputs are usually crafted by fast single-step adversaries so as to scale to large datasets.
This work is mainly focused on the adversarial training yet efficient FGSM adversary.
In this scenario, it is difficult to train a model with great generalization due to the lack of representative adversarial samples, aka the samples are unable to accurately reflect the adversarial domain.
To alleviate this problem, we propose a novel Adversarial Training with Domain Adaptation (ATDA) method.
Our intuition is to regard the adversarial training on FGSM adversary as a domain adaption task with limited number of target domain samples.
The main idea is to learn a representation that is semantically meaningful and domain invariant on the clean domain as well as the adversarial domain.
Empirical evaluations on Fashion-MNIST, SVHN, CIFAR-10 and CIFAR-100 demonstrate that ATDA can greatly improve the generalization of adversarial training and the smoothness of the learned models, and outperforms state-of-the-art methods on standard benchmark datasets.
To show the transfer ability of our method, we also extend ATDA to the adversarial training on iterative attacks such as PGD-Adversial Training (PAT) and the defense performance is improved considerably.
Deep learning techniques have shown impressive performance on image classification and many other computer vision tasks.
However, recent works have revealed that deep learning models are often vulnerable to adversarial examples BID14 , which are maliciously designed to deceive the target model by generating carefully crafted adversarial perturbations on original clean inputs.
Moreover, adversarial examples can transfer across models to mislead other models with a high probability BID9 .
How to effectively defense against adversarial attacks is crucial for security-critical computer vision systems, such as autonomous driving.As a promising approach, adversarial training defends from adversarial perturbations by training a target classifier with adversarial examples.
Researchers have found BID7 BID11 that adversarial training could increase the robustness of neural networks.
However, adversarial training often obtains adversarial examples by taking a specific attack technique (e.g., FGSM) into consideration, so the defense targeted such attack and the trained model exhibits weak generalization ability on adversarial examples from other adversaries BID7 .
BID22 showed that the robustness of adversarial training can be easily circumvented by the attack that combines with random perturbation from other models.
Accordingly, for most existing adversarial training methods, there is a risk of overfitting to adversarial examples crafted on the original model with the specific attack.In this paper, we propose a novel adversarial training method that is able to improve the generalization of adversarial training.
From the perspective of domain adaptation (DA) BID20 , there is a big domain gap between the distribution of clean examples and the distribution of adversarial examples in the high-level representation space, even though adversarial perturbations are imperceptible to humans.
showed that adversarial perturbations are progressively amplified along the layer hierarchy of neural networks, which maximizes the distance between the original and adversarial subspace representations.
In addition, adversarial training simply injects adversarial examples from a specific attack into the training set, but there is still a large sample space for adversarial examples.
Accordingly, training with the classification loss on such a training set will probably lead to overfitting on the adversarial examples from the specific attack.
Even though BID24 showed that adversarial training with iterative noisy attacks has stronger robustness than the adversarial training with single-step attacks, iterative attacks have a large computational cost and there is no theoretical analysis to justify that the adversarial examples sampled in such way could be sufficiently representative for the adversarial domain.Our contributions are focused on how to improve the generalization of adversarial training on the simple yet scalable attacks, such as FGSM (Goodfellow et al.) .
The key idea of our approach is to formulate the learning procedure as a domain adaptation problem with limited number of target domain samples, where target domain denotes adversarial domain.
Specifically, we introduce unsupervised as well as supervised domain adaptation into adversarial training to minimize the gap and increase the similarity between the distributions of clean examples and adversarial examples.
In this way, the learned models generalize well on adversarial examples from different ∞ bounded attacks.
We evaluate our ATDA method on standard benchmark datasets.
Empirical results show that despite a small decay of accuracy on clean data, ATDA significantly improves the generalization ability of adversarial training and has the transfer ability to extend to adversarial training on PGD BID11 .
In this study, we regard the adversarial training as a domain adaptation task with limited number of target labeled data.
By combining adversarial training on FGSM adversary with unsupervised and supervised domain adaptation, the generalization ability on adversarial examples from various attacks and the smoothness on the learned models can be highly improved for robust defense.
In addition, ATDA can easily be extended to adversarial training on iterative attacks (e.g., PGD) to improve the defense performance.
The experimental results on several benchmark datasets suggest that the proposed ATDA and its extension PATDA achieve significantly better generalization results as compared with current competing adversarial training methods.

assistant: text: We propose a novel adversarial training with domain adaptation method that significantly improves the generalization ability on adversarial examples from different attacks.