Mutual distance bounding (DB) protocols enable two distrusting parties to establish an upper-bound on the distance between them. DB has been so far mainly considered in classical settings and for classical applications, especially in wireless settings, e.g., to prevent relay attacks in wireless authentication and access control systems, and for secure localization. While recent research has started exploring DB in quantum settings, all current quantum DB (QDB) protocols employ quantum-bits (qubits) in the rapid-bit exchange phase and only perform one-way DB. Specifically, the latest QDB proposals improve the initial ones by adding resistance to photon number splitting attacks, and improving round complexity by avoiding communication from the prover to the verifier in the last authentication phase. This paper presents two new QDB protocols that differ from previously proposed protocols in several aspects: (1) to the best of our knowledge, our protocols are the first to utilize entangled qubits in the rapid-bit exchange phase, previous protocols relied on sending individual qubits, not those from a pair of entangled ones; (2) our second protocol can perform mutual QDB between two parties in one execution, previous QDB protocols had to be executed twice with the prover and verifier roles reversed in each execution; (3) the use of entangled qubits in our protocols thwarts attacks that previous QDB protocols were prone to; (4) and finally, our protocols also eliminate the need for communication from the prover to the verifier in the last authentication phase, which was necessary in some previous QDB protocols. Our work paves the way for several interesting research directions which we briefly discuss in detail in the appendix.

翻译：互距离界定协议使两个不信任方能够建立彼此间距离的上限。距离界定迄今主要被考虑用于经典设定和经典应用，尤其在无线环境中，例如防止无线认证与访问控制系统中的中继攻击，以及实现安全定位。尽管近期研究已开始探索量子环境中的距离界定，但当前所有量子距离界定协议均在快速比特交换阶段采用量子比特，且仅执行单向距离界定。具体而言，最新的量子距离界定方案通过增加对光子数分裂攻击的抵抗性、以及避免在最后认证阶段从证明方到验证方的通信来提升轮复杂度，从而改进了初始方案。本文提出两种新的量子距离界定协议，它们在多个方面不同于先前提出的协议：(1) 据我们所知，本协议是首个在快速比特交换阶段利用纠缠量子比特的，先前协议依赖发送单个量子比特而非来自一对纠缠量子比特的单个量子比特；(2) 我们的第二个协议可在单次执行中实现两方之间的互量子距离界定，而先前量子距离界定协议需执行两次，并在每次执行中互换证明方与验证方角色；(3) 本协议对纠缠量子比特的使用能够抵御先前量子距离界定协议易受的攻击；(4) 最后，本协议还消除了在最后认证阶段从证明方到验证方的通信需求，而这在先前一些量子距离界定协议中是必需的。我们的工作为若干有趣的研究方向铺平了道路，这些方向已在附录中简要详细讨论。