Privacy-Preserving and Poisoning-Defending Federated Learning in Fog Computing

Federated learning (FL) has been widely applied in Internet of Things (IoT). However, two security problems hinder the proliferation of FL in practical IoT, i.e., privacy leakage and poisoning attacks. To address these problems, various approaches have been proposed from different perspectives. Nevertheless, there remain two critical challenges: 1) how to establish a unified framework for protecting privacy and defending against poisoning attacks and 2) how to implement such methods in the flexible computing architecture of fog computing. In this article, we propose CROSSBEAM, a comprehensive scheme that provides both defense against poisoning attacks and privacy protection for FL in fog computing. Specifically, we construct frameworks to defend against poisoning attacks under both independent and identically distributed (IID) and non-IID settings. Meanwhile, we establish an actively secure framework to protect users' privacy, building a bridge between privacy protection and poisoning defense. Our CROSSBEAM allows multiple fog nodes and users to collaboratively achieve the FL training. Besides, it can effectively alleviate the negative impact caused by poisoning attacks, meanwhile, users' data confidentiality can still be guaranteed, even if multiple active fog nodes collude with each other to infer users' privacy. Additionally, our scheme is of robustness to participants (fog nodes and users) being off-line during the training process. Moreover, benefited from the superiorities of our hierarchical mechanism and secure framework, our scheme can perform with high efficiency. We present rigorous security proof and extensive performance analysis for our CROSSBEAM.