In this paper, we propose a robust aggregation method for federated learning (FL) that can effectively tackle malicious Byzantine attacks. At each user, model parameter is firstly updated by multiple steps, which is adjustable over iterations, and then pushed to the aggregation center directly. This decreases the number of interactions between the aggregation center and users, allows each user to set training parameter in a flexible way, and reduces computation burden compared with existing works that need to combine multiple historical model parameters. At the aggregation center, geometric median is leveraged to combine the received model parameters from each user. Rigorous proof shows that zero optimality gap is achieved by our proposed method with linear convergence, as long as the fraction of Byzantine attackers is below half. Numerical results verify the effectiveness of our proposed method.

本文提出了一种强大的聚合方法，用于联邦学习，可以有效地应对恶意拜占庭攻击，每个用户可以通过多个步骤来更新模型参数，然后将其直接推送到聚合中心，聚合中心利用几何中位数将用户的模型参数进行组合，并通过严格的证明表明，只要恶意攻击者的比例低于一半，我们提出的方法可以达到零最优间隔，并呈线性收敛性。数值结果验证了我们提出方法的有效性。

拜占庭攻击鲁棒的联邦学习：实现零最优间隙