Towards Well-trained Model Robustness in Federated Learning: An Adversarial- Example-Generation- Efficiency Perspective

Federated Learning (FL), as a privacy-oriented distributed machine learning paradigm, can obtain a well-trained global model without private dataset transferring. Nevertheless, FL is subject to severe security threats of adversarial examples (AEs) with unnoticeable perturbations, generated by white-box attacks in honest-but-curious FL participants. Adversarial training is an effective solution to enhance the robustness of the model by identifying AEs as correct samples. However, the AE training efficiency is crucial in realistic scenarios of adversarial training, such as autonomous driving. Researchers have proposed the Fast Gradient Sign Method (FGSM) and its improvement to generate AEs rapidly. In this paper, we propose a novel optimizer-based FGSM, FastAdaBelief-based FGSM (FAB-FGSM), in order to generate AEs more efficiently and effectively. Benefitting from time-vary coefficients and a vanishing factor, FAB-FGSM realizes a more adaptive iteration step size than AdaBelief-based FGSM (AB-FGSM) and Adam-based FGSM (AI-FGSM). We explore the probable causes by recalling the theoretical analysis of three optimizers. Extensive experiment results demonstrate that compared to AB-FGSM and AI-FGSM, our FAB-FGSM achieves the fastest convergence and the best attack success rate in four target models, including Inception v3, Inception v4, Inception ResNet v2, ResNet-101.