Federated Learning (FL) is designed to protect the data privacy of each client during the training process by transmitting only models instead of the original data. However, the trained model may memorize certain information about the training data. With the recent legislation on right to be forgotten, it is crucially essential for the FL model to possess the ability to forget what it has learned from each client. We propose a novel federated unlearning method to eliminate a client's contribution by subtracting the accumulated historical updates from the model and leveraging the knowledge distillation method to restore the model's performance without using any data from the clients. This method does not have any restrictions on the type of neural networks and does not rely on clients' participation, so it is practical and efficient in the FL system. We further introduce backdoor attacks in the training process to help evaluate the unlearning effect. Experiments on three canonical datasets demonstrate the effectiveness and efficiency of our method.

在联邦学习中，提出了一种新颖的联邦遗忘方法，通过从模型中减去历史累积更新来消除客户端的贡献，并利用知识蒸馏方法恢复模型的性能，而不使用来自客户端的任何数据。该方法不依赖于客户端的参与，不对神经网络的类型有任何限制，并引入后门攻击来评估遗忘效果。实验结果表明了本文方法的有效性和效率。

使用知识蒸馏进行联邦遗忘