A Review of Privacy Preserving Federated Learning for Private IoT Analytics

The Internet-of-Things generates vast quantities of data, much of it attributable to an individual's activity and behaviour. Holding and processing such personal data in a central location presents a significant privacy risk to individuals (of being identified or of their sensitive data being leaked). However, analytics based on machine learning and in particular deep learning benefit greatly from large amounts of data to develop high performance predictive models. Traditionally, data and models are stored and processed in a data centre environment where models are trained in a single location. This work reviews research around an alternative approach to machine learning known as federated learning which seeks to train machine learning models in a distributed fashion on devices in the user's domain, rather than by a centralised entity. Furthermore, we review additional privacy preserving methods applied to federated learning used to protect individuals from being identified during training and once a model is trained. Throughout this review, we identify the strengths and weaknesses of different methods applied to federated learning and finally, we outline future directions for privacy preserving federated learning research, particularly focusing on Internet-of-Things applications.