Federated Learning (FL) is a distributed learning framework, in which the local data never leaves clients devices to preserve privacy, and the server trains models on the data via accessing only the gradients of those local data. Without further privacy mechanisms such as differential privacy, this leaves the system vulnerable against an attacker who inverts those gradients to reveal clients sensitive data. However, a gradient is often insufficient to reconstruct the user data without any prior knowledge. By exploiting a generative model pretrained on the data distribution, we demonstrate that data privacy can be easily breached. Further, when such prior knowledge is unavailable, we investigate the possibility of learning the prior from a sequence of gradients seen in the process of FL training. We experimentally show that the prior in a form of generative model is learnable from iterative interactions in FL. Our findings strongly suggest that additional mechanisms are necessary to prevent privacy leakage in FL.

通过利用预先训练的生成模型，本文探究了在缺乏先前知识的情况下可以从 Federated Learning 训练过程中看到的一系列梯度中学习先验知识的可能性。实验证明这种先验知识可以被轻易违反隐私，从而强烈建议在FL中需要采用额外的机制来防止隐私泄露。

带有生成式图像 prior 的梯度反演