提出自适应水印窃取方法,提升对大模型文本水印的攻击效率。
Beyond A Fixed Seal: Adaptive Stealing Watermark in Large Language Models

- 通过位置感知的封印构造与自适应选择模块,动态调整攻击视角。
- 在相同条件下,窃取效率显著高于传统固定策略方法。
- 适用于研究水印安全性的研究人员,推动更鲁棒水印设计。
水印技术为大型语言模型(LLM)服务提供关键保护,可检测生成文本来源。然而,水印窃取算法(SWA)能从目标模型生成的带水印文本中提取水印信息,实施针对性攻击,削弱水印可靠性。现有SWA采用固定策略,忽视水印信息分布不均及真实生成过程的动态性。为此,我们提出自适应窃取(AS),通过位置相关的封印构建和自适应选择模块,实现更高设计灵活性。AS基于上下文有序标记的不同激活状态定义多种攻击视角,并在执行时根据水印兼容性、生成优先级和动态相关性动态选择最优视角。实验表明,在相同条件下,AS显著提升了对目标水印的窃取效率。结果强调了需开发更鲁棒的LLM水印以抵御潜在攻击。代码已开源:https://github.com/DrankXs/AdaptiveStealingWatermark。
原文摘要 · Abstract (English)
Watermarking provides a critical safeguard for large language model (LLM) services by facilitating the detection of LLM-generated text. Correspondingly, stealing watermark algorithms (SWAs) derive watermark information from watermarked texts generated by victim LLMs to craft highly targeted adversarial attacks, which compromise the reliability of watermarks. Existing SWAs rely on fixed strategies, overlooking the non-uniform distribution of stolen watermark information and the dynamic nature of real-world LLM generation processes. To address these limitations, we propose Adaptive Stealing (AS), a novel SWA featuring enhanced design flexibility through Position-Based Seal Construction and Adaptive Selection modules. AS operates by defining multiple attack perspectives derived from distinct activation states of contextually ordered tokens. During attack execution, AS dynamically selects the optimal perspective based on watermark compatibility, generation priority, and dynamic generation relevance. Our experiments demonstrate that AS significantly increases steal efficiency against target watermarks under identical experimental conditions. These findings highlight the need for more robust LLM watermarks to withstand potential attacks. We release our code to the community for future research\footnote{https://github.com/DrankXs/AdaptiveStealingWatermark}.
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