Steps Adaptive Decay DPSGD: Enhancing Performance on Imbalanced Datasets with Differential Privacy with HAM10000
Differential privacy (DP) degrades performance on medical image datasets with few-shot and class-imbalanced settings (e.g., HAM10000), primarily due to excessive gradient clipping suppressing minority-class signals and majority-class dominance leading to suboptimal convergence. To address this, we propose Adaptive-Decay DP-SGD, a method that jointly optimizes the noise scale and gradient clipping threshold via a linear decay schedule—preserving informative minority-class gradients early in training and alleviating the tension between privacy preservation and model convergence. Additionally, we introduce a dynamic privacy budget allocation strategy tailored to class imbalance. Under ε = 3.0 and δ = 10⁻³, our method achieves a 2.15% absolute accuracy gain over Auto-DPSGD on HAM10000, significantly improving the privacy–utility trade-off in imbalanced learning scenarios.