Topic-Based Watermarks for Large Language Models
To address the risks of misuse and data contamination arising from the difficulty of tracing LLM-generated text, existing watermarking methods struggle to balance robustness, generation quality, and deployment overhead. This paper proposes a lightweight, topic-guided watermarking scheme: it dynamically constructs a semantically aligned “green list” vocabulary via topic modeling and embeds detectable signatures solely through probability-biased sampling during standard autoregressive decoding—requiring no model architecture modification or dedicated framework. Its core innovation is the first-ever topic-aware dynamic green list mechanism. Experiments across multiple LLMs show that the method achieves perplexity on par with SynthID-Text, improves watermark detection accuracy by 12.7%, significantly enhances resilience against paraphrasing attacks (failure rate <8%), and incurs negligible inference overhead.