FedGT: Identification of Malicious Clients in Federated Learning with Secure Aggregation
This addresses security and privacy issues in federated learning for applications like healthcare or finance, but it is incremental as it builds on existing group testing and secure aggregation techniques.
FedGT tackles the problem of identifying malicious clients in federated learning with secure aggregation by using group testing, and it demonstrates high model utility and outperforms a recent robust aggregation method in experiments on datasets like MNIST and CIFAR-10.
We propose FedGT, a novel framework for identifying malicious clients in federated learning with secure aggregation. Inspired by group testing, the framework leverages overlapping groups of clients to identify the presence of malicious clients in the groups via a decoding operation. The clients identified as malicious are then removed from the model training, which is performed over the remaining clients. By choosing the size, number, and overlap between groups, FedGT strikes a balance between privacy and security. Specifically, the server learns the aggregated model of the clients in each group - vanilla federated learning and secure aggregation correspond to the extreme cases of FedGT with group size equal to one and the total number of clients, respectively. The effectiveness of FedGT is demonstrated through extensive experiments on the MNIST, CIFAR-10, and ISIC2019 datasets in a cross-silo setting under different data-poisoning attacks. These experiments showcase FedGT's ability to identify malicious clients, resulting in high model utility. We further show that FedGT significantly outperforms the private robust aggregation approach based on the geometric median recently proposed by Pillutla et al. in multiple settings.