RL-Finetuned LLMs for Privacy-Preserving Synthetic Rewriting

Fuente: arXiv
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Hauptverfasser: Shi, Zhan, Yuan, Yefeng, Liu, Yuhong, Cheng, Liang, Fang, Yi
Format: Preprint
Veröffentlicht: 2025
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author Shi, Zhan
Yuan, Yefeng
Liu, Yuhong
Cheng, Liang
Fang, Yi
author_facet Shi, Zhan
Yuan, Yefeng
Liu, Yuhong
Cheng, Liang
Fang, Yi
contents The performance of modern machine learning systems depends on access to large, high-quality datasets, often sourced from user-generated content or proprietary, domain-specific corpora. However, these rich datasets inherently contain sensitive personal information, raising significant concerns about privacy, data security, and compliance with regulatory frameworks. While conventional anonymization techniques can remove explicit identifiers, such removal may result in performance drop in downstream machine learning tasks. More importantly, simple anonymization may not be effective against inference attacks that exploit implicit signals such as writing style, topical focus, or demographic cues, highlighting the need for more robust privacy safeguards during model training. To address the challenging issue of balancing user privacy and data utility, we propose a reinforcement learning framework that fine-tunes a large language model (LLM) using a composite reward function that jointly optimizes for explicit and implicit privacy, semantic fidelity, and output diversity. To effectively capture population level regularities, the privacy reward combines semantic cues with structural patterns derived from a minimum spanning tree (MST) over latent representations. By modeling these privacy-sensitive signals in their distributional context, the proposed approach guides the model to generate synthetic rewrites that preserve utility while mitigating privacy risks. Empirical results show that the proposed method significantly enhances author obfuscation and privacy metrics without degrading semantic quality, providing a scalable and model-agnostic solution for privacy preserving data generation in the era of large language models.
format Preprint
id arxiv_https___arxiv_org_abs_2508_19286
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle RL-Finetuned LLMs for Privacy-Preserving Synthetic Rewriting
Shi, Zhan
Yuan, Yefeng
Liu, Yuhong
Cheng, Liang
Fang, Yi
Cryptography and Security
Artificial Intelligence
Machine Learning
The performance of modern machine learning systems depends on access to large, high-quality datasets, often sourced from user-generated content or proprietary, domain-specific corpora. However, these rich datasets inherently contain sensitive personal information, raising significant concerns about privacy, data security, and compliance with regulatory frameworks. While conventional anonymization techniques can remove explicit identifiers, such removal may result in performance drop in downstream machine learning tasks. More importantly, simple anonymization may not be effective against inference attacks that exploit implicit signals such as writing style, topical focus, or demographic cues, highlighting the need for more robust privacy safeguards during model training. To address the challenging issue of balancing user privacy and data utility, we propose a reinforcement learning framework that fine-tunes a large language model (LLM) using a composite reward function that jointly optimizes for explicit and implicit privacy, semantic fidelity, and output diversity. To effectively capture population level regularities, the privacy reward combines semantic cues with structural patterns derived from a minimum spanning tree (MST) over latent representations. By modeling these privacy-sensitive signals in their distributional context, the proposed approach guides the model to generate synthetic rewrites that preserve utility while mitigating privacy risks. Empirical results show that the proposed method significantly enhances author obfuscation and privacy metrics without degrading semantic quality, providing a scalable and model-agnostic solution for privacy preserving data generation in the era of large language models.
title RL-Finetuned LLMs for Privacy-Preserving Synthetic Rewriting
topic Cryptography and Security
Artificial Intelligence
Machine Learning
url https://arxiv.org/abs/2508.19286