2025/12/23 by Mohammadreza Rostami, Rostami, Mohammadreza, Solmaz S. Kia +1
Computer Science · #Privacy-Preserving Technologies in Data #Stochastic Gradient Optimization Techniques #Cryptography and Data Security
paper · doi:10.48550/arxiv.2512.20814
This paper introduces FedMPDD (Federated Learning via Multi-Projected Directional Derivatives), a novel algorithm that simultaneously optimizes bandwidth utilization and enhances privacy in Federated Learning. The core idea of FedMPDD is to encode each client's high-dimensional gradient by computing its directional derivatives along multiple random vectors. This compresses the gradient into a much smaller message, significantly reducing uplink communication costs from O(d) to O(m), where m ≪ d. The server then decodes the aggregated information by projecting it back onto the same random vectors. Our key insight is that averaging multiple projections overcomes the dimension-dependent convergence limitations of a single projection. We provide a rigorous theoretical analysis, establishing that FedMPDD converges at a rate of O(1/√(K)), matching the performance of FedSGD. Furthermore, we demonstrate that our method provides some inherent privacy against gradient inversion attacks due to the geometric properties of low-rank projections, offering a tunable privacy-utility trade-off controlled by the number of projections. Extensive experiments on benchmark datasets validate our theory and demonstrates our results.