处理敏感表格数据的团队终于有了实用的差分隐私方案——Lumberjack 在隐私预算下显著提升随机森林效用，做隐私保护机器学习的开发者可以直接参考其方法。
Lumberjack 是一种新的差分隐私随机森林算法，通过构建大型随机决策树并应用激进的隐私保护剪枝，显著提升了模型效用。其核心创新是一种针对层次数据的重击检测算法，误差随树高对数增长，支持使用更深的树。在基准数据集上的实验表明，Lumberjack 在隐私预算实用时大幅优于现有方法，建立了新的最优水平。这项工作表明精心设计的差分隐私随机森林可以缩小效用差距，为隐私保护机器学习提供了有前景的新方向。
Lumberjack: Better Differentially Private Random Forests through Heavy Hitter Detection in Trees
Random forests are widely used in fields involving sensitive tabular data, but existing approaches to enforcing differential privacy (DP) typically degrade performance to the point of impracticality. In this paper, we introduce Lumberjack, a differentially private random forest algorithm that achieves substantially higher utility by constructing large random decision trees and then applying aggressive, privacy-preserving pruning to retain only sufficiently populated nodes. A key component of our approach is a novel $(\varepsilon,δ)$-DP heavy hitter detection algorithm for hierarchical data, whose error is $O_{\varepsilon,δ}(\sqrt{\log h})$ for trees of height $h$ and may be of independent interest. This favorable scaling enables the use of significantly deeper trees than in prior work, leading to improved expressiveness under privacy constraints. Our empirical evaluation on benchmark datasets shows that Lumberjack consistently outperforms prior DP random forest methods, establishing a new state of the art. In particular, our approach yields substantial improvements in the privacy-utility trade-off for practical privacy budgets. Our findings suggest that carefully designed DP random forests can close much of the utility gap, highlighting a promising and underexplored direction for future research.