Federated Unlearning With Reinforcement Learning: Adaptive Privacy Preservation for Clients

With growing attention to data privacy in federated learning, federated unlearning has become an important solution to meet increasing demands for privacy compliance. However, unlearning may bring in new security concerns, such as dangers of adversarial manipulation, where the adversary may launch malicious updates or inputs to hurt the model performance or prediction, privacy-attacks, as the sensitive data can be possibly deduced from the process of unlearning, and performance degradation, because the unlearning process may break the consistency or performance of the model. In this paper, to address such issues and acquire a good and adaptive unlearning policy without causing much negative effect to the federated system, we present a reinforcement learning based method to facilitate the data unlearning method in federated learning. Our approach iteratively disposes of clients through partial unlearning, complete unlearning, or no unlearning using a DQN combined with clients’ properties like contribution, privacy cost, and computational overhead. We show that by utilizing the reinforcement learning technique, the performance decay can be defended effectively, and adversarial behaviors are indeed a common concern for the federated unlearning scenario. Our analysis can inform the development of federated unlearning frameworks that defend against performance and security threats.