Federated analysis can help perform large-scale analyses using neuroimaging datasets across various research groups overcoming the limitations of institutional data-sharing policies, privacy or regulatory concerns as it requires no data sharing. In this work, we employ a federated neuromark algorithm to generate independent component analysis (ICA) time courses data from functional magnetic resonance imaging (fMRI) data and feed it to a federated deep neural network (DNN) model to perform classification of schizophrenia patients versus controls.

Federated learning (FL) for distributed data has gained significant attention by enabling model training on local data without transferring it to a central system. While this approach protects sensitive information, risks of data leakage still persist, necessitating the integration of privacy-preserving techniques such as differential privacy. In many FL applications, tasks like exploratory data analysis or tracking and monitoring data that change over time are essential. For these purposes, analysts rely on data visualizations to make decisions or draw conclusions. This vision paper emphasizes the importance of federated privacy-preserving visualization and outlines a general pipeline for its implementation. We discuss the challenges of integrating federated visualizations with differential privacy and demonstrate the feasibility of this approach through examples, such as federated privacy-preserving boxplots, scatterplots, and correlation visualizations in neuroimaging. This highlights the need for further research in this promising field.

The presence of correlation is known to make privacy protection more difficult. We investigate the privacy of socially contagious attributes on a network of individuals, where each individual possessing that attribute may influence a number of others into adopting it. We show that for contagions following the Independent Cascade model there exists a giant connected component of infected nodes, containing a constant fraction of all the nodes who all receive the contagion from the same set of sources. We further show that it is extremely hard to hide the existence of this giant connected component if we want to obtain an estimate of the activated users at an acceptable level. Moreover, an adversary possessing this knowledge can predict the real status (“active” or “inactive”) with decent probability for many of the individuals regardless of the privacy (perturbation) mechanism used. As a case study, we show that the Wasserstein mechanism, a state-of-the-art privacy mechanism designed specifically for correlated data, introduces a noise with magnitude of order Ω(n) in the count estimation in our setting. We provide theoretical guarantees for two classes of random networks: Erdős-Rényi graphs and Chung-Lu power-law graphs under the Independent Cascade model. Experiments demonstrate that a giant connected component of infected nodes can indeed appear in real-world networks and a simple inference attack can reveal the status of a good fraction of nodes.