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StealthInk: A Multi-bit and Stealthy Watermark for Large Language Models

Published: June 5, 2025 | arXiv ID: 2506.05502v1

By: Ya Jiang , Chuxiong Wu , Massieh Kordi Boroujeny and more

Potential Business Impact:

Marks AI writing so you know who wrote it.

Business Areas:
Text Analytics Data and Analytics, Software

Watermarking for large language models (LLMs) offers a promising approach to identifying AI-generated text. Existing approaches, however, either compromise the distribution of original generated text by LLMs or are limited to embedding zero-bit information that only allows for watermark detection but ignores identification. We present StealthInk, a stealthy multi-bit watermarking scheme that preserves the original text distribution while enabling the embedding of provenance data, such as userID, TimeStamp, and modelID, within LLM-generated text. This enhances fast traceability without requiring access to the language model's API or prompts. We derive a lower bound on the number of tokens necessary for watermark detection at a fixed equal error rate, which provides insights on how to enhance the capacity. Comprehensive empirical evaluations across diverse tasks highlight the stealthiness, detectability, and resilience of StealthInk, establishing it as an effective solution for LLM watermarking applications.

Country of Origin
🇺🇸 United States

Page Count
25 pages

Category
Computer Science:
Cryptography and Security