PrivateBoost: Privacy-Preserving Federated Gradient Boosting for Cross-Device Medical Data
Specht, B.; Garbaya, S.; Ermis, O.; Schneider, R.; Chavarriaga, R.; Khadraoui, D.; Tayeb, Z.
Show abstract
Cross-device medical federated learning where individual patients participate directly rather than institutions poses a unique challenge: each client holds only a few samples, often just one (e.g., a single diagnostic record), leaving insufficient local data for gradient computation. Existing approaches, such as Secure Aggregation, require client-to-client coordination impractical for intermittently available mobile devices, while homomorphic encryption-based alternatives introduce sophisticated key management and coordination requirements ill-suited to dynamic cross-device deployments. We present privateboost, a federated XGBoost system that addresses this setting through m-of-n Shamir secret sharing with commitment-based anonymous aggregation. Clients distribute shares to a fixed set of shareholders requiring no client-to-client communication and the aggregator reconstructs only aggregate gradient sums via Lagrange interpolation, never observing individual values or client identities. We evaluate on UCI medical datasets, demonstrating 98% split gain retention relative to centralized XGBoost and accuracy resilient to up to 80% client dropout.
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