SGAN-RA: Reconstruction Attack for Big Model in Asynchronous Federated Learning

Federated learning (FL) is a distributed learning framework designed for large-scale applications. The core advantage of FL is that each participant is not required to share the local data with a central server. This inherent privacy-preserving capability is well suited to the increasingly popular large-scale generative AI models. However, some studies have shown that FL is susceptible to reconstruction attacks, in which an attacker leverages the acquired gradients or model parameters to reconstruct a victim's data. In this article, we propose a novel reconstruction attack scheme based on generative adversarial networks (GANs) in an asynchronous FL scenario that can reconstruct a victim's dataset without an auxiliary dataset. This adversarial scheme demonstrates a significant ability to reconstruct a dataset of victims accurately, thereby posing a substantial threat to user privacy, particularly in the context of large-scale models. Furthermore, we explore various defense mechanisms based on the characteristics of asynchronous FL and ultimately establish a viable defense scheme based on homomorphic encryption and an intermediate server. The proposed defense framework successfully and flawlessly defends against reconstruction attacks from the server side in an asynchronous setting without degradation of the model performance.