Mitigating Disparate Impact of Differentially Private Learning through Bounded Adaptive Clipping

Linzh Zhao, Aki Rehn, Mikko A. Heikkilä, Razane Tajeddine, Antti Honkela

Keywords: Differential Privacy, Machine Learning, Fairness, Adaptive Clipping

TL;DR: We propose bounded adaptive clipping to address fairness issues in differentially private deep learning.

Abstract: Differential privacy (DP) has become an essential framework for privacy-preserving machine learning. Existing DP learning methods, however, often have disparate impacts on model predictions, e.g., for minority groups. Gradient clipping, which is often used in DP learning, can suppress larger gradients from challenging samples. We show that this problem is amplified by adaptive clipping, which will often shrink the clipping bound to tiny values to match a well-fitting majority, while significantly reducing the accuracy for others. We propose bounded adaptive clipping, which introduces a tunable lower bound to prevent excessive gradient suppression. Our method improves worst-class accuracy by over 10 percentage points on Skewed and Fashion MNIST compared to unbounded adaptive clipping, 7 points compared to Automatic clipping, and 5 points compared to constant clipping.

Primary Area: alignment, fairness, safety, privacy, and societal considerations

Submission Number: 12262