High utility and rigorous data privacy are of the main goals of a federated learning (FL) system, which learns a model from the data distributed among some clients. The latter has been tried to achieve by using differential privacy in FL (DPFL). There is often heterogeneity in clients privacy requirements, and existing DPFL works either assume uniform privacy requirements for clients or are not applicable when server is not fully trusted (our setting). Furthermore, there is often heterogeneity in batch and/or dataset size of clients, which as shown, results in extra variation in the DP noise level across clients model updates. With these sources of heterogeneity, straightforward aggregation strategies, e.g., assigning clients aggregation weights proportional to their privacy parameters will lead to lower utility. We propose Robust-HDP, which efficiently estimates the true noise level in clients model updates and reduces the noise-level in the aggregated model updates considerably. Robust-HDP improves utility and convergence speed, while being safe to the clients that may maliciously send falsified privacy parameter to server. Extensive experimental results on multiple datasets and our theoretical analysis confirm the effectiveness of Robust-HDP. Our code can be found here.

在联邦学习中，差分隐私被用于保护数据隐私和提高模型效用，然而，在具有异质性要求和客户端批次/数据集大小差异的情况下，传统的聚合策略会降低效用。本文提出了一种名为Robust-HDP的方法，通过有效估计客户端模型更新中的噪声水平并显著减少聚合模型更新中的噪声水平，来提高效用和收敛速度，并对客户端的恶意行为进行安全处理。实验结果和理论分析验证了Robust-HDP的有效性。

异构差分隐私联邦学习的噪音感知算法