SimpleMark: Fast Multi-Bit Text Watermarking under f -Divergence Constraints

Abstract:We introduce a framework for multi-bit text watermarking with security defined directly through $f$-divergence from the base language model distribution. Unlike prior approaches that focus on average-key distortion-freeness or a particular statistical distance, our formulation supports general $f$-divergences, including total variation and KL divergence, and enforces the guarantee for each realized key and embedded message. We develop a coding-based watermarking scheme that optimally biases next-token distributions subject to a prescribed divergence budget, and characterize the resulting tradeoff between embedding rate, decoding reliability, and statistical security. Experimentally, we compare our method against prior multi-bit watermarking schemes across modern language models and payload regimes. Our approach achieves substantially lower watermark detectability while maintaining competitive message-recovery performance and generation quality. Our results provide a unified view of secure multi-bit watermarking and recover several commonly used security notions as special cases.

Cryptography and Security (cs.CR); Artificial Intelligence (cs.AI); Information Theory (cs.IT)

arXiv:2610.05712 [cs.CR]

(or arXiv:2610.05712v1 [cs.CR] for this version)

https://doi.org/10.48550/arXiv.2610.05712 Focus to learn more arXiv-issued DOI via DataCite (pending registration)

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