提出可抵抗句子重组的语义水印,提升内容修改下的检测鲁棒性。
Semantic Watermarking with Order-Robust Detection over Sub-sentence Units
- 通过子句单元检测,降低对句子顺序的敏感性。
- 在90%内容保真度下,攻击成功率降至10.8%(原方案达65.5%)。
- 适用于需防篡改的生成文本认证场景,如AI内容溯源。
语义水印将标记绑定于句子语义而非词元选择,有望抵御保持内容的编辑攻击。然而,检测器仅能观察攻击者提供的文本,攻击者可通过重述、重排或重新分段实现免检测规避,这些操作均引发嵌入位移:检测时的嵌入与水印生成时不同,导致标记丢失。本文提出的自适应嵌入位移攻击(EDA)统一优化三种编辑,使用公开同义改写器与代理编码器,无需访问提供方生成器或密钥。在5%误报率(FPR)和90%内容保真度阈值下,EDA成功移除4种方案中32.6%至47.9%文档的水印,优于现有攻击。为应对该漏洞,提出(k)-SwordStamp:基于子句单元的语义水印,实现顺序无关检测,在小幅质量损失下显著降低对结构选择的敏感性。针对k-SwordStamp,最强无箱攻击的攻击成功率为10.8%;若获检测器与密钥,攻击成功率升至39.7%,仍低于k-SemStamp的65.5%。代码开源:https://github.com/D-Diaa/SwordStamp。
原文摘要 · Abstract (English)
Semantic watermarks tie the mark to sentence meaning rather than token choices, promising robustness to content-preserving edits. However, the detector only observes attacker-supplied text, which can be reworded, reordered, or resegmented to evade detection without content loss. Rewording, reordering, and resegmentation all cause embedding displacement: detection tests embeddings different from those selected during watermarking and can therefore lose the mark. Our adaptive embedding displacement attack (EDA) admits all three edits under a single objective that maximizes this displacement. It uses a public paraphraser and surrogate encoder without access to the provider's generator or secret key. At a 5% false-positive rate (FPR) and content-preservation threshold $\bar{q}=90\%$, EDA successfully removes the mark on between 32.6% and 47.9% of documents across four schemes, the highest among the tested attacks. Therefore, EDA evaluates the schemes' robustness more thoroughly than passive paraphrasing. To address these vulnerabilities, we design (k)-SwordStamp: semantic watermarks with order-robust detection over sub-sentence units, reducing sensitivity to attacker-chosen structure at a small quality cost. Against k-SwordStamp, the strongest no-box attack we test is an EDA variant adapted to its design, with a 10.8% attack-success rate. A stronger EDA with access to the provider's detector and secret key reaches a 39.7% attack-success rate, compared with 65.5% on k-SemStamp. Our code is available at https://github.com/D-Diaa/SwordStamp.
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