arXiv Computation and Language By Zewei Deng, Mohamed Seif, Liyan Xie

Watermarkability: Measuring and Improving Language-Model Compatibility with Logit-Based Watermarks

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The paper introduces "watermarkability," a metric that quantifies how compatible a language model is with a logit‑based watermark that boosts the probability of a specified token set during decoding. By measuring the expected minimum KL divergence needed to achieve a target probability mass, the authors can assess and compare models and watermark rules. They propose a two‑stage approach—first training a low‑rank adapter conditioned on the target set, then applying a minimal uniform logit bias—to reduce this cost, achieving significant perplexity reductions across multiple watermark schedules on OPT‑125M and Qwen3‑8B.

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arXiv Machine Learning
2d ago

MarkTune: Improving the Quality-Detectability Trade-off in Model-Embedded LLM Watermarking

MarkTune is a model‑embedded watermarking framework that improves the trade‑off between generation quality and detectability. By regularizing toward a high‑quality reference distribution, it decouples quality preservation from proximity to the base model and uses the GaussMark detection statistic as a reward during on‑policy fine‑tuning. Empirical results show that MarkTune enhances the quality‑detectability frontier, maintains downstream task performance, and remains robust against text‑editing and open‑weight attacks across diverse datasets.

By Yizhou Zhao, Zhiwei Steven Wu, Adam Block