Secure Neuroimaging Analysis using Federated Learning with Homomorphic Encryption
This work addresses privacy concerns in neuroimaging analysis for researchers and institutions using federated learning, though it is incremental as it applies existing encryption methods to enhance security.
The paper tackled the problem of data leakage in federated learning by proposing a framework that uses fully-homomorphic encryption, specifically CKKS, to secure model training without transferring individual data. The result showed no degradation in performance when training a deep learning model on brain MRI datasets to predict age, with encrypted and non-encrypted models achieving comparable results.
Federated learning (FL) enables distributed computation of machine learning models over various disparate, remote data sources, without requiring to transfer any individual data to a centralized location. This results in an improved generalizability of models and efficient scaling of computation as more sources and larger datasets are added to the federation. Nevertheless, recent membership attacks show that private or sensitive personal data can sometimes be leaked or inferred when model parameters or summary statistics are shared with a central site, requiring improved security solutions. In this work, we propose a framework for secure FL using fully-homomorphic encryption (FHE). Specifically, we use the CKKS construction, an approximate, floating point compatible scheme that benefits from ciphertext packing and rescaling. In our evaluation on large-scale brain MRI datasets, we use our proposed secure FL framework to train a deep learning model to predict a person's age from distributed MRI scans, a common benchmarking task, and demonstrate that there is no degradation in the learning performance between the encrypted and non-encrypted federated models.