Towards Anytime-Valid Statistical Watermarking

Fuente: arXiv
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Hauptverfasser: Huang, Baihe, Xu, Eric, Ramchandran, Kannan, Jiao, Jiantao, Jordan, Michael I.
Format: Preprint
Veröffentlicht: 2026
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author Huang, Baihe
Xu, Eric
Ramchandran, Kannan
Jiao, Jiantao
Jordan, Michael I.
author_facet Huang, Baihe
Xu, Eric
Ramchandran, Kannan
Jiao, Jiantao
Jordan, Michael I.
contents The proliferation of Large Language Models (LLMs) necessitates efficient mechanisms to distinguish machine-generated content from human text. While statistical watermarking has emerged as a promising solution, existing methods suffer from two critical limitations: the lack of a principled approach for selecting sampling distributions and the reliance on fixed-horizon hypothesis testing, which precludes valid early stopping. In this paper, we bridge this gap by developing the first e-value-based watermarking framework, Anchored E-Watermarking, that unifies optimal sampling with anytime-valid inference. Unlike traditional approaches where optional stopping invalidates Type-I error guarantees, our framework enables valid, anytime-inference by constructing a test supermartingale for the detection process. By leveraging an anchor distribution to approximate the target model, we characterize the optimal e-value with respect to the worst-case log-growth rate and derive the optimal expected stopping time. Our theoretical claims are substantiated by simulations and evaluations on established benchmarks, showing that our framework can significantly enhance sample efficiency, reducing the average token budget required for detection by 13-15% relative to state-of-the-art baselines.
format Preprint
id arxiv_https___arxiv_org_abs_2602_17608
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Towards Anytime-Valid Statistical Watermarking
Huang, Baihe
Xu, Eric
Ramchandran, Kannan
Jiao, Jiantao
Jordan, Michael I.
Machine Learning
Artificial Intelligence
The proliferation of Large Language Models (LLMs) necessitates efficient mechanisms to distinguish machine-generated content from human text. While statistical watermarking has emerged as a promising solution, existing methods suffer from two critical limitations: the lack of a principled approach for selecting sampling distributions and the reliance on fixed-horizon hypothesis testing, which precludes valid early stopping. In this paper, we bridge this gap by developing the first e-value-based watermarking framework, Anchored E-Watermarking, that unifies optimal sampling with anytime-valid inference. Unlike traditional approaches where optional stopping invalidates Type-I error guarantees, our framework enables valid, anytime-inference by constructing a test supermartingale for the detection process. By leveraging an anchor distribution to approximate the target model, we characterize the optimal e-value with respect to the worst-case log-growth rate and derive the optimal expected stopping time. Our theoretical claims are substantiated by simulations and evaluations on established benchmarks, showing that our framework can significantly enhance sample efficiency, reducing the average token budget required for detection by 13-15% relative to state-of-the-art baselines.
title Towards Anytime-Valid Statistical Watermarking
topic Machine Learning
Artificial Intelligence
url https://arxiv.org/abs/2602.17608