Public Data Assisted Differentially Private In-Context Learning

Seongho Joo, Hyukhun Koh, Kyomin Jung


Abstract
In-context learning (ICL) in Large Language Models (LLMs) has shown remarkable performance across various tasks without requiring fine-tuning. However, recent studies have highlighted the risk of private data leakage through the prompt in ICL, especially when LLMs are exposed to malicious attacks. While differential privacy (DP) provides strong privacy guarantees, it often significantly reduces the utility of in-context learning (ICL). To address this challenge, we incorporate task-related public data into the ICL framework while maintaining the DP guarantee. Based on this approach, we propose a private in-context learning algorithm that effectively balances privacy protection and model utility. Through experiments, we demonstrate that our approach significantly improves the utility of private ICL with the assistance of public data. Additionally, we show that our method is robust against membership inference attacks, demonstrating empirical privacy protection.
Anthology ID:
2025.findings-emnlp.875
Volume:
Findings of the Association for Computational Linguistics: EMNLP 2025
Month:
November
Year:
2025
Address:
Suzhou, China
Editors:
Christos Christodoulopoulos, Tanmoy Chakraborty, Carolyn Rose, Violet Peng
Venue:
Findings
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
16129–16152
Language:
URL:
https://aclanthology.org/2025.findings-emnlp.875/
DOI:
Bibkey:
Cite (ACL):
Seongho Joo, Hyukhun Koh, and Kyomin Jung. 2025. Public Data Assisted Differentially Private In-Context Learning. In Findings of the Association for Computational Linguistics: EMNLP 2025, pages 16129–16152, Suzhou, China. Association for Computational Linguistics.
Cite (Informal):
Public Data Assisted Differentially Private In-Context Learning (Joo et al., Findings 2025)
Copy Citation:
PDF:
https://aclanthology.org/2025.findings-emnlp.875.pdf
Checklist:
 2025.findings-emnlp.875.checklist.pdf