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A Privacy-Friendly Approach to Data Valuation
Jiachen Wang · Yuqing Zhu · Yu-Xiang Wang · Ruoxi Jia · Prateek Mittal

Data valuation aims to quantify the usefulness of individual data sources in training machine learning (ML) models, and is a critical aspect of data-centric ML research. However, data valuation faces significant yet frequently overlooked privacy challenges despite its importance. This paper studies these privacy challenges with a focus on KNN-Shapley, one of the most practical data valuation methods nowadays. We first emphasize the inherent privacy risks of KNN-Shapley, and demonstrate the significant technical difficulties in adapting KNN-Shapley to accommodate differential privacy (DP). To overcome these challenges, we introduce \emph{TKNN-Shapley}, a refined variant of KNN-Shapley that is privacy-friendly, allowing for straightforward modifications to incorporate DP guarantee (\emph{DP-}TKNN-Shapley). We show that DP-TKNN-Shapley has several advantages and offers a superior privacy-utility tradeoff compared to naively privatized KNN-Shapley in discerning data quality. Moreover, even non-private TKNN-Shapley achieves comparable performance as KNN-Shapley. Overall, our findings suggest that TKNN-Shapley is a promising alternative to KNN-Shapley, particularly for real-world applications involving sensitive data. Full version of the paper is attached in Appendix.

Author Information

Jiachen Wang (Princeton University)
Yuqing Zhu (UC Santa Barbara)
Yu-Xiang Wang (UC Santa Barbara / Amazon)
Ruoxi Jia (Virginia Tech)
Prateek Mittal (Princeton University)

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