arXiv:2509.16088cs.LG2025-09EMNLP被引 1

将随机平滑用于视觉语言模型,实现生成结果的可证明鲁棒性

Randomized Smoothing Meets Vision-Language Models

  • 通过构建分类器将生成输出映射为离散动作或语义类别,使随机平滑适用于生成任务
  • 在弱假设下仍保持2~3个数量级采样量减少而精度损失极小
  • 适合关注大模型安全性、对抗攻击防御的研究者和应用开发者

随机平滑(RS)是确保机器学习模型正确性的主流技术,可在点对点层面解析地生成鲁棒性证书。尽管其在分类任务中已有良好理解,但应用于生成模型时仍不明确,因为生成模型输出为序列而非标签。本文通过将生成输出关联至一个预言机分类任务,解决了这一问题:最终响应可被分类为离散动作(如视觉-语言代理中的服务机器人指令)、有害/无害(如内容审核或毒性检测),或通过预言机将答案聚类为语义等价组。在预言机分类误差率受限的前提下,我们建立了样本数与对应鲁棒半径之间的理论关系。进一步通过分析推导出改进的缩放定律,表明即使在较弱假设下,仍可维持早期研究中2至3个数量级更少采样量即可满足鲁棒性且精度损失最小的结论。这些进展使得当前最先进的视觉语言模型的鲁棒性认证既定义清晰又计算可行,经受住了近期越狱式对抗攻击的验证。

原文摘要 · Abstract (English)

Randomized smoothing (RS) is one of the prominent techniques to ensure the correctness of machine learning models, where point-wise robustness certificates can be derived analytically. While RS is well understood for classification, its application to generative models is unclear, since their outputs are sequences rather than labels. We resolve this by connecting generative outputs to an oracle classification task and showing that RS can still be enabled: the final response can be classified as a discrete action (e.g., service-robot commands in VLAs), as harmful vs. harmless (content moderation or toxicity detection in VLMs), or even applying oracles to cluster answers into semantically equivalent ones. Provided that the error rate for the oracle classifier comparison is bounded, we develop the theory that associates the number of samples with the corresponding robustness radius. We further derive improved scaling laws analytically relating the certified radius and accuracy to the number of samples, showing that the earlier result of 2 to 3 orders of magnitude fewer samples sufficing with minimal loss remains valid even under weaker assumptions. Together, these advances make robustness certification both well-defined and computationally feasible for state-of-the-art VLMs, as validated against recent jailbreak-style adversarial attacks.

视觉语言模型随机平滑鲁棒性认证对抗攻击

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