HeavyWater and SimplexWater: Distortion-Free LLM Watermarks for Low-Entropy Next-Token Predictions

Fuente: arXiv
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Autori principali: Tsur, Dor, Long, Carol Xuan, Verdun, Claudio Mayrink, Hsu, Hsiang, Chen, Chen-Fu, Permuter, Haim, Vithana, Sajani, Calmon, Flavio P.
Natura: Preprint
Pubblicazione: 2025
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author Tsur, Dor
Long, Carol Xuan
Verdun, Claudio Mayrink
Hsu, Hsiang
Chen, Chen-Fu
Permuter, Haim
Vithana, Sajani
Calmon, Flavio P.
author_facet Tsur, Dor
Long, Carol Xuan
Verdun, Claudio Mayrink
Hsu, Hsiang
Chen, Chen-Fu
Permuter, Haim
Vithana, Sajani
Calmon, Flavio P.
contents Large language model (LLM) watermarks enable authentication of text provenance, curb misuse of machine-generated text, and promote trust in AI systems. Current watermarks operate by changing the next-token predictions output by an LLM. The updated (i.e., watermarked) predictions depend on random side information produced, for example, by hashing previously generated tokens. LLM watermarking is particularly challenging in low-entropy generation tasks -- such as coding -- where next-token predictions are near-deterministic. In this paper, we propose an optimization framework for watermark design. Our goal is to understand how to most effectively use random side information in order to maximize the likelihood of watermark detection and minimize the distortion of generated text. Our analysis informs the design of two new watermarks: HeavyWater and SimplexWater. Both watermarks are tunable, gracefully trading-off between detection accuracy and text distortion. They can also be applied to any LLM and are agnostic to side information generation. We examine the performance of HeavyWater and SimplexWater through several benchmarks, demonstrating that they can achieve high watermark detection accuracy with minimal compromise of text generation quality, particularly in the low-entropy regime. Our theoretical analysis also reveals surprising new connections between LLM watermarking and coding theory. The code implementation can be found in https://github.com/DorTsur/HeavyWater_SimplexWater
format Preprint
id arxiv_https___arxiv_org_abs_2506_06409
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle HeavyWater and SimplexWater: Distortion-Free LLM Watermarks for Low-Entropy Next-Token Predictions
Tsur, Dor
Long, Carol Xuan
Verdun, Claudio Mayrink
Hsu, Hsiang
Chen, Chen-Fu
Permuter, Haim
Vithana, Sajani
Calmon, Flavio P.
Cryptography and Security
Artificial Intelligence
Computation and Language
Computers and Society
Information Theory
Machine Learning
Large language model (LLM) watermarks enable authentication of text provenance, curb misuse of machine-generated text, and promote trust in AI systems. Current watermarks operate by changing the next-token predictions output by an LLM. The updated (i.e., watermarked) predictions depend on random side information produced, for example, by hashing previously generated tokens. LLM watermarking is particularly challenging in low-entropy generation tasks -- such as coding -- where next-token predictions are near-deterministic. In this paper, we propose an optimization framework for watermark design. Our goal is to understand how to most effectively use random side information in order to maximize the likelihood of watermark detection and minimize the distortion of generated text. Our analysis informs the design of two new watermarks: HeavyWater and SimplexWater. Both watermarks are tunable, gracefully trading-off between detection accuracy and text distortion. They can also be applied to any LLM and are agnostic to side information generation. We examine the performance of HeavyWater and SimplexWater through several benchmarks, demonstrating that they can achieve high watermark detection accuracy with minimal compromise of text generation quality, particularly in the low-entropy regime. Our theoretical analysis also reveals surprising new connections between LLM watermarking and coding theory. The code implementation can be found in https://github.com/DorTsur/HeavyWater_SimplexWater
title HeavyWater and SimplexWater: Distortion-Free LLM Watermarks for Low-Entropy Next-Token Predictions
topic Cryptography and Security
Artificial Intelligence
Computation and Language
Computers and Society
Information Theory
Machine Learning
url https://arxiv.org/abs/2506.06409