SimMark: A Robust Sentence-Level Similarity-Based Watermarking Algorithm for Large Language Models

• URL: http://arxiv.org/abs/2502.02787v2
• Date: Thu, 11 Sep 2025 04:36:56 GMT
• Title: SimMark: A Robust Sentence-Level Similarity-Based Watermarking Algorithm for Large Language Models
• Authors: Amirhossein Dabiriaghdam, Lele Wang,
• Abstract summary: SimMark is a robust sentence-level watermarking algorithm for large language models (LLMs)<n>It embeds detectable statistical patterns imperceptible to humans, and employs a soft counting mechanism.<n>We show that SimMark sets a new benchmark for robust watermarking of LLM-generated content.
• Score: 4.069844339028727
• License: http://creativecommons.org/licenses/by-sa/4.0/
• Abstract: The widespread adoption of large language models (LLMs) necessitates reliable methods to detect LLM-generated text. We introduce SimMark, a robust sentence-level watermarking algorithm that makes LLMs' outputs traceable without requiring access to model internals, making it compatible with both open and API-based LLMs. By leveraging the similarity of semantic sentence embeddings combined with rejection sampling to embed detectable statistical patterns imperceptible to humans, and employing a soft counting mechanism, SimMark achieves robustness against paraphrasing attacks. Experimental results demonstrate that SimMark sets a new benchmark for robust watermarking of LLM-generated content, surpassing prior sentence-level watermarking techniques in robustness, sampling efficiency, and applicability across diverse domains, all while maintaining the text quality and fluency.

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