FedV: Privacy-Preserving Federated Learning over Vertically Partitioned Data

Federated learning (FL) has been proposed to allow collaborative training of machine learning (ML) models among multiple parties to keep their data private and only model updates are shared. Most existing approaches have focused on horizontal FL, while many real scenarios follow a vertically-partitioned FL setup, where a complete feature set is formed only when all the datasets from the parties are combined, and the labels are only available to a single party. Privacy-preserving vertical FL is challenging because complete sets of labels and features are not owned by one entity. Existing approaches for vertical FL require multiple peer-to-peer communications among parties, leading to lengthy training times, and are restricted to (approximated) linear models and just two parties. To close this gap, we propose FedV, a framework for secure gradient computation in vertical settings for several widely used ML models such as linear models, logistic regression, and support vector machines. FedV removes the need for peer-to-peer communication among parties by using functional encryption schemes and works for larger and changing sets of parties. We empirically demonstrate the applicability for multiple ML models and show a reduction of 10%-70% of training time and 80% to 90% in data transfer to the comparable state-of-the-art approaches.