TripPattern: A Pattern-based Text Watermarking Method for Large Language Models

Sangjun Moon, Dasom Choi, Jingun Kwon, Hidetaka Kamigaito, Taro Watanabe, Manabu Okumura


Abstract
Text watermarking techniques have gained significant attention for identifying machine-generated text and mitigating risks from large language models (LLMs). Existing methods typically divide an LLM’s vocabulary into green and red tokens, but encouraging generation toward green tokens can reduce text quality and naturalness. To address this, we propose TripPattern, a watermarking framework that formulates text watermarking as a pattern-based matching task using three vocabulary partitions. TripPattern divides the vocabulary into one neutral group and two pattern groups. During generation, the model alternates token selection between the two pattern groups to embed detectable patterns, while neutral tokens are selected independently to improve flexibility and preserve naturalness. For detection, TripPattern uses pattern-based statistical tests that provide interpretable p-values by measuring how often adjacent tokens alternate between the pattern groups. Theoretical analysis and empirical evaluations on four multilingual datasets show that TripPattern maintains LLM generation quality while achieving robust watermark detectability.
Anthology ID:
2026.findings-aacl.177
Volume:
Findings of the Association for Computational Linguistics: IJCNLP-AACL 2026
Month:
November
Year:
2026
Address:
Hengqin, China
Editors:
Yue Zhang, Ruifeng Xu, Ayu Purwarianti, Tong Rong, Jun Suzuki
Venue:
Findings
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
3523–3538
Language:
URL:
https://aclanthology.org/2026.findings-aacl.177/
DOI:
Bibkey:
Cite (ACL):
Sangjun Moon, Dasom Choi, Jingun Kwon, Hidetaka Kamigaito, Taro Watanabe, and Manabu Okumura. 2026. TripPattern: A Pattern-based Text Watermarking Method for Large Language Models. In Findings of the Association for Computational Linguistics: IJCNLP-AACL 2026, pages 3523–3538, Hengqin, China. Association for Computational Linguistics.
Cite (Informal):
TripPattern: A Pattern-based Text Watermarking Method for Large Language Models (Moon et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-aacl.177.pdf