## 1 Introduction  
Due to the broadcast nature of wireless communications, they are particularly susceptible to unauthorized attacks, such as third-party eavesdropping. Traditional wireless security schemes typically operate at the upper layers of the protocol stack and rely on trusted third parties for key distribution and authentication. However, these schemes generally require reliable network connections for credential exchange. In maritime communications, when a ship is near the coast, it can leverage terrestrial wireless access systems such as WiMAX, LTE, or GSM/GPRS, benefiting from the broadband communication services protected by internet security protocols commonly used on land. However, when a ship is far from the coast, it must rely on radio frequency bands (such as HF, MF, VHF, and UHF) for low-speed, long-distance communication or use satellite communications [1]. Satellites provide global communication and network access, and with advancements in low Earth orbit (LEO) technology and decreasing costs, systems like Starlink have emerged as viable options for maritime communication. However, in close-range scenarios, satellite communication is often unnecessary, and ship communication remains primarily reliant on radio-based interaction. In this context, ensuring secure communications between ships,especially when they encounter each other without prior knowledge, becomes a critical challenge that must be addressed. Existing solutions primarily focus on securing ship communications via AISs, which transmit the ship's GPS coordinates, course, and identification information through the VHF band (161.975 and 162.025 MHz) [1]. They are widely used for identity recognition, route adjustment, accident prevention, search and rescue, and remote tracking. Since 2002, passenger and commercial ships over 300 tons must be equipped with an AIS [2], and, since 2014, the European Union has mandated AISs on all fishing vessels over 15 m [3]. Today, over 650,000 ships globally use AISs, exchanging over 18 million messages monthly [4]. However, the AIS was implemented without security features, meaning all messages are transmitted in plaintext, making communications vulnerable. Malicious nodes can easily intercept AIS messages, exposing ships to significant risks. Despite these vulnerabilities, research on AIS security remains relatively scarce, with most existing studies focusing on public key cryptography schemes. The application of public key cryptography can ensure the security of AIS unicast and broadcast communications while also offering effective identity authentication, thereby providing comprehensive security services. However, it is important to note that in the unique context of AIS communication, the implementation of public key cryptography may encounter the following challenges:  
* Due to the limited computational power of embedded AIS equipment, AISs are unsuitable for resource-intensive asymmetric algorithms [5]. Moreover, because ocean-going ships may belong to different countries, the use of different certificate authorities (CAs) to issue digital certificates requires managing certificate chains, further increasing computational overhead. * Public key cryptography requires the involvement of CAs, which in turn necessitates consensus among maritime authorities regarding key generation. Some countries or regions may encounter difficulties in participating due to technical limitations or policy constraints. * The ship may be located in a distant ocean, making it challenging to update or revoke its keys and certificates in real time. Therefore, we aimed to explore a more lightweight solution to address the security challenges of AISs. In recent years, with the rapid development of Internet of Things (IoT) technology, there is increasing attention on physical-layer security. Since most IoT nodes are embedded systems with limited resources, many studies have applied physical-layer key generation (PLKG) to enhance wireless communication security.