Abstract:With the vigorous development of areas such as big data and cloud computing, it has become a worldwide trend for the public to attach importance to data security and privacy. Different groups are reluctant to share data in order to protect their own interests and privacy, which leads to data silos. Federated learning enables multiple parties to build a common, robust model without exchanging their data samples, thus addressing critical issues such as data fragmentation and data isolation. However, more and more studies have shown that the federated learning algorithm first proposed by Google can not resist sophisticated privacy attacks. Therefore, how to strengthen privacy protection and protect users’ data privacy in the federated learning scenario is an important issue. This paper offers a systematic survey of existing research achievements of privacy attacks and protection in federated learning in recent years. First, the definition, characteristics and classification of federated learning are introduced. Then the adversarial model of privacy threats in federated learning is analyzed, and typical works of privacy attacks are classified with respect to the adversary’s objectives. Next, several mainstream privacy-preserving technologies are introduced and their advantages and disadvantages in practical applications are pointed out. Furthermore, the existing achievements on protection against privacy attacks are summarized and six privacy-preserving schemes are elaborated. Finally, future challenges of privacy preserving in federated learning are concluded and promising future research directions are discussed.