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arXiv 2607.08400cs.CRcs.AIcs.LG
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TRACE:一种通过互补嵌入实现的用于大语言模型智能体轨迹的双通道鲁棒归属水印

TRACE: A Two-Channel Robust Attribution Watermark via Complementary Embeddings for LLM-Agent Trajectories

University of New South Wales(新南威尔士大学);Griffith University(格里菲斯大学);CSIRO’s Data61(澳大利亚联邦科学与工业研究组织(CSIRO)的数据61)

Zheng Gao, Xiaoyu Li, Xiaoyan Feng, Jiaojiao Jiang, Yang Song, Yulei Sui, Zhenchang Xing, Liming Zhu

AI总结:

研究针对大语言模型智能体轨迹归属水印易被经销商攻击的问题,提出TRACE方法,通过互补嵌入构建双通道水印,包括基于局部内容的选择通道和基于日志框架的计数通道,实验表明该方法能保证水印鲁棒性,保持智能体成功率且检测分数高。

摘要:

大语言模型智能体通过经销商接触用户,经销商可能会重新命名开发者的智能体或替换为更便宜的模型。当出处存在争议时,归属依赖于轨迹日志(工具调用、观察和执行动作的记录,而非模型推理),经销商存储并处理该日志以计量使用情况。因此,水印必须能在对其检测所依据的证据具有完全读/写访问权限的对手攻击下存活;现有的智能体水印做不到,因为它们的归属直接从该日志中读取。我们提出了TRACE,据我们所知,这是首个在动作选择上无失真、在删除情况下自同步且在重写下无条件不变的智能体水印。删除会使基于位置的密钥不同步,重写会改变内容,所以抗删除的密钥必须来自内容,抗重写的密钥来自位置,没有单个密钥能兼顾两者。然而,一条轨迹有容纳两个水印的空间。TRACE叠加了一个选择通道,该通道基于局部内容通过无失真采样器确定选择哪个动作,从而证明智能体的分布不变且删除后检测能重新同步;还有一个计数通道,基于日志的框架确定每个决策组持有多少记录,重写无法触及该框架。我们证明这种行为水印的信号是以决策熵为代价获得的,每个决策至少付出其熵的一半,确定性决策则无需付出,并且擦除两个通道会迫使经销商破坏其转售的轨迹。在ToolBench和ALFWorld上,TRACE与未加水印的智能体成功率相当,其选择通道在长时轨迹上检测分数接近z = 100,在70%的步长删除下仍可检测,并且在任何强度的大语言模型重写下计数通道完全不变。

英文摘要:

LLM agents reach users through resellers, who may rebrand a developer's agent or substitute a cheaper model. When provenance is disputed, attribution rests on the trajectory log (the record of tool calls, observations, and executed actions, not the model's reasoning), which the reseller stores and processes to meter usage. A watermark must therefore survive an adversary with full read/write access to the very evidence it is detected from; existing agent watermarks do not, as their attribution is read straight off that log. We present TRACE, to our knowledge the first agent watermark that is distortion-free in its action choices, self-synchronizing under deletion, and unconditionally invariant under rewriting. Deletion desynchronizes a position-derived key and rewriting alters content, so a deletion-robust key must come from content and a rewrite-robust key from position, and no single key serves both. A trajectory, however, has room for two watermarks. TRACE superposes a selection channel that sets which action is chosen, keyed on local content with a distortion-free sampler, so the agent's distribution is provably unchanged and detection resynchronizes after deletions, and a tally channel that sets how many records each decision group holds, keyed on the log's skeleton alone, which no rewriting can touch. We prove this behavioral watermark's signal is bought with decision entropy, each decision paying at least half its entropy and deterministic decisions nothing, and that erasing both channels forces the reseller to corrupt the trajectories it resells. On ToolBench and ALFWorld, TRACE matches the unwatermarked agent's success rate while its selection channel reaches detection scores near z = 100 on long-horizon trajectories, stays detectable under 70% step deletion, and keeps a tally channel exactly unchanged under LLM rewriting of any strength.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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