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Main Authors: Oh, Myeong Seok, Kim, Dong-Yun, Oh, Hanseok, Kang, Chaean, Kang, Joeun, Wang, Xiaonan, Park, Hyunjung, Jung, Young Cheol, Kim, Hansaem
Format: Preprint
Published: 2026
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Online Access:https://arxiv.org/abs/2604.21211
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author Oh, Myeong Seok
Kim, Dong-Yun
Oh, Hanseok
Kang, Chaean
Kang, Joeun
Wang, Xiaonan
Park, Hyunjung
Jung, Young Cheol
Kim, Hansaem
author_facet Oh, Myeong Seok
Kim, Dong-Yun
Oh, Hanseok
Kang, Chaean
Kang, Joeun
Wang, Xiaonan
Park, Hyunjung
Jung, Young Cheol
Kim, Hansaem
contents Current text anonymization evaluation relies on span-based metrics that fail to capture what an adversary could actually infer, and assumes a single data subject, ignoring multi-subject scenarios. To address these limitations, we present SPIA (Subject-level PII Inference Assessment), the first benchmark that shifts the unit of evaluation from text spans to individuals, comprising 675 documents across legal and online domains with novel subject-level protection metrics. Extensive experiments show that even when over 90% of PII spans are masked, subject-level inference protection drops as low as 33%, leaving the majority of personal information recoverable through contextual inference. Furthermore, target-subject-focused anonymization leaves non-target subjects substantially more exposed than the target subject. We show that subject-level inference-based evaluation is essential for ensuring safe text anonymization in real-world settings.
format Preprint
id arxiv_https___arxiv_org_abs_2604_21211
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Subject-level Inference for Realistic Text Anonymization Evaluation
Oh, Myeong Seok
Kim, Dong-Yun
Oh, Hanseok
Kang, Chaean
Kang, Joeun
Wang, Xiaonan
Park, Hyunjung
Jung, Young Cheol
Kim, Hansaem
Computation and Language
Current text anonymization evaluation relies on span-based metrics that fail to capture what an adversary could actually infer, and assumes a single data subject, ignoring multi-subject scenarios. To address these limitations, we present SPIA (Subject-level PII Inference Assessment), the first benchmark that shifts the unit of evaluation from text spans to individuals, comprising 675 documents across legal and online domains with novel subject-level protection metrics. Extensive experiments show that even when over 90% of PII spans are masked, subject-level inference protection drops as low as 33%, leaving the majority of personal information recoverable through contextual inference. Furthermore, target-subject-focused anonymization leaves non-target subjects substantially more exposed than the target subject. We show that subject-level inference-based evaluation is essential for ensuring safe text anonymization in real-world settings.
title Subject-level Inference for Realistic Text Anonymization Evaluation
topic Computation and Language
url https://arxiv.org/abs/2604.21211