Secure long-distance communication in quantum key distribution (QKD) networks depends on trusted repeater nodes along the entire transmission path. Consequently, these nodes will be subject to strict auditing and certification in future large-scale QKD deployments. However, trust must also extend to the network operator, who is responsible for fulfilling contractual obligations -- such as ensuring certified devices are used and transmission paths remain disjoint where required. In this work, we present a path validation protocol specifically designed for QKD networks. It enables the receiver to verify compliance with agreed-upon policies. At the same time, the protocol preserves the operator's confidentiality by ensuring that no sensitive information about the network topology is revealed to users. We provide a formal model and a provably secure generic construction of the protocol, along with a concrete instantiation. For long-distance communication involving 100 nodes, the protocol has a computational cost of 1-2.5s depending on the machine, and a communication overhead of less than 70kB - demonstrating the efficiency of our approach.

翻译：量子密钥分发（QKD）网络中的远距离安全通信依赖于整条传输路径上的可信中继节点。因此，在未来大规模QKD部署中，这些节点将受到严格的审计与认证。然而，信任还必须延伸至网络运营商——其须履行合同义务，例如确保使用经认证的设备，并保证传输路径在必要情况下保持不相交。本文提出了一种专为QKD网络设计的路径验证协议。该协议使接收方能够验证是否遵守约定的策略，同时通过确保不向用户泄露任何关于网络拓扑的敏感信息来保护运营商的机密性。我们提供了协议的形式化模型、可证明安全性的通用构造方案及具体实例化。实验表明，在涉及100个节点的远距离通信中，本协议的计算开销为1-2.5秒（取决于机器性能），通信开销低于70kB——充分展示了该方法的效率。