With the growing use of underwater acoustic communications and the recent adoption of standards in this field, it is becoming increasingly important to secure messages against eavesdroppers. In this paper, we focus on a physical-layer security solution to generate sequences of random bits (keys) between two devices (Alice and Bob) belonging to an underwater acoustic network (UWAN); the key must remain secret to a passive eavesdropper (Eve) not belonging to the UWAN. Our method is based on measuring the propagation delay of the underwater acoustic channel over multiple hops of the UWAN: this harvests the randomness in the UWAN topology and turns the slow sound propagation in water into an advantage against eavesdropping. Our key generation protocol includes a route discovery handshake, whereby all UWAN devices at intermediate hops accumulate their message processing delays. This enables Alice and Bob to compute the actual propagation delays along each route and to map such information to a sequence of bits. Finally, from these bit sequences, Alice and Bob obtain a secret key. We analyze the performance of the protocol theoretically and assess it via extensive simulations and field experiments.

中文翻译：

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水下声学网络的路由传播延迟生成密钥


随着水声通信的日益普及以及该领域最近采用的标准，保护消息免遭窃听者变得越来越重要。在本文中，我们重点关注物理层安全解决方案，用于在属于水声网络 (UWAN) 的两个设备（Alice 和 Bob）之间生成随机位（密钥）序列；密钥必须对不属于 UWAN 的被动窃听者 (Eve) 保密。我们的方法基于测量 UWAN 多跳上的水声通道的传播延迟：这收获了 UWAN 拓扑中的随机性，并将水中缓慢的声音传播转化为对抗窃听的优势。我们的密钥生成协议包括路由发现握手，中间跃点的所有 UWAN 设备都会累积其消息处理延迟。这使得 Alice 和 Bob 能够计算沿每条路线的实际传播延迟，并将此类信息映射到比特序列。最后，Alice 和 Bob 从这些比特序列中获得密钥。我们从理论上分析该协议的性能，并通过广泛的模拟和现场实验对其进行评估。