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Enhancing Federated Learning Privacy Through Encrypted Computation

Anfas K. K., A. Manoj, Anuja Kunjumon, J. J. Nair

Procedia Computer Science, 2026

Abstract

Ensuring patient privacy while leveraging artificial intelligence in healthcare is a critical challenge. This work presents a privacy-preserving federated learning framework for classifying brain tumors from MRI scans. Without disclosing private patient information, the proposed system enables collaborative model training across multiple healthcare institutions. To prevent long-term key compromise and ensure secure transmission of intermediate CNN features, we employ homomorphic encryption using the CKKS scheme with periodic key rotation. Each institution locally trains a lightweight MobileNetV3-Small model and encrypts the extracted features with TenSEAL before transmitting them to a central server for aggregation. Our approach presents a novel encrypted feature sharing mechanism that improves privacy without sacrificing model performance, in contrast to traditional methods that encrypt gradients or model updates. Experimental evaluations on a brain MRI dataset demonstrate that the proposed framework increases the accuracy of models from 84.5% (traditional FL) and 87.1% (LEAF) to 94.1%. It safeguards sensitive healthcare data using full CKKS encryption with key rotation and achieves a 5× compression ratio, reducing communication overhead compared to LEAF’s 3×. These results highlight its potential for scalable, secure, and high-performance federated AI in real-world clinical settings

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