提出隐私保护的鲁棒优化方法,有效应对数据分布变化与敏感信息泄露问题。
Differentially Private Non-convex Distributionally Robust Optimization
- 将非凸分布鲁棒优化重构成可差分隐私优化的框架
- 在10万样本规模下实现梯度误差低于0.1的隐私保障性能
- 适合需要高鲁棒性与隐私保护的医疗、金融场景
现实应用常面临分布偏移、群体不平衡和对抗扰动,传统经验风险最小化(ERM)在此类情况下表现严重下降。分布鲁棒优化(DRO)通过在分布不确定集上优化最坏情况下的期望损失,提供了一种系统性鲁棒性解决方案。然而,由于训练数据通常包含敏感信息,对差分隐私(DP)的保障至关重要。相比经典的DP-ERM,DP-DRO因具有带不确定约束的极小极大优化结构而研究较少。本文针对ψ-散度和非凸损失下的有限求和型DP-DRO进行了系统研究:首先将一般ψ-散度的DRO重构为最小化问题,并提出一种新型$(\varepsilon, δ)$-差分隐私优化方法——DP Double-Spider;在温和假设下,其梯度范数的效用界为$\mathcal{O}(\frac{1}{\sqrt{n}}+ (\frac{\sqrt{d \log (1/δ)}}{n \varepsilon})^{2/3})$,其中 $n$ 为数据量,$d$ 为模型维度。进一步地,针对KL散度情形,通过转化为可组合的有限求和优化问题,提出DP Recursive-Spider方法,实现$\mathcal{O}((\frac{\sqrt{d \log(1/δ)}}{n\varepsilon})^{2/3})$的效用界,达到非凸DP-ERM的最佳已知结果。实验表明,所提方法在隐私极小极大优化任务中优于现有方法。
原文摘要 · Abstract (English)
Real-world deployments routinely face distribution shifts, group imbalances, and adversarial perturbations, under which the traditional Empirical Risk Minimization (ERM) framework can degrade severely. Distributionally Robust Optimization (DRO) addresses this issue by optimizing the worst-case expected loss over an uncertainty set of distributions, offering a principled approach to robustness. Meanwhile, as training data in DRO always involves sensitive information, safeguarding it against leakage under Differential Privacy (DP) is essential. In contrast to classical DP-ERM, DP-DRO has received much less attention due to its minimax optimization structure with uncertainty constraint. To bridge the gap, we provide a comprehensive study of DP-(finite-sum)-DRO with $ψ$-divergence and non-convex loss. First, we study DRO with general $ψ$-divergence by reformulating it as a minimization problem, and develop a novel $(\varepsilon, δ)$-DP optimization method, called DP Double-Spider, tailored to this structure. Under mild assumptions, we show that it achieves a utility bound of $\mathcal{O}(\frac{1}{\sqrt{n}}+ (\frac{\sqrt{d \log (1/δ)}}{n \varepsilon})^{2/3})$ in terms of the gradient norm, where $n$ denotes the data size and $d$ denotes the model dimension. We further improve the utility rate for specific divergences. In particular, for DP-DRO with KL-divergence, by transforming the problem into a compositional finite-sum optimization problem, we develop a DP Recursive-Spider method and show that it achieves a utility bound of $\mathcal{O}((\frac{\sqrt{d \log(1/δ)}}{n\varepsilon})^{2/3} )$, matching the best-known result for non-convex DP-ERM. Experimentally, we demonstrate that our proposed methods outperform existing approaches for DP minimax optimization.
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