## 1 Introduction  
Low-Earth-Orbit (LEO) satellite networks have attracted considerable attention in recent years. LEO satellite networks are useful in a variety of scenarios. In some remote areas with small populations and the ocean, it is difficult to provide internet services from the ground due to the high construction cost of the network. In addition, when traveling in fast-moving vehicles, such as airplanes, communication frequently switches between different ground base stations, resulting in high packet loss rates and poor service quality [1, 2, 3]. At this point, LEO satellite networks can provide broadband communication where there is no ground equipment, and provide high-quality services to anyone, anytime and anywhere [4, 5, 6]. The LEO satellite networks have a low delay, high bandwidth, high transmission rate, and low link loss, and bring global coverage and efficient frequency reuse [7, 8, 9, 10]. As 5G communication standards mature, satellite communications play an important role in expanding and completing ground networks [11, 12]. With the increasing demand for seamless broadband communication, the global LEO satellite communication system has become an important part of connecting space and ground. The goal is to provide high-quality access for all users at any time and in any space [13, 14, 15]. In LEO satellite networks, traditional access authentication needs satellites to send authentication information back to the ground control center to confirm user identity. There are so many hops of transmission that the overhead of the certificate management using a public key infrastructure is not negligible. In addition, due to the high-speed movement of LEO satellites in space, users on the ground can only be served by one satellite within approximately ten minutes in the Iridium system. Communication requires frequent switching of authentication, and traditional authentication protocols are greatly affected by onboard routing protocols. Because the authentication process is greatly affected by the centralized certificate authority. In the authentication process, satellites need to obtain the certificate revocation list which is used to notify the satellite that the certificate has been cancelled by the certificate authority. Such communication is implemented by transmitting control data through the inter-satellite links. The inter-satellite links may be congested or disconnected, so it is particularly important to choose a proper routing protocol. Improper routing will not only increase the delay, but also lead to data loss. Researchers have proposed using an identity-based encryption algorithm to replace certificate authority institutions [16]. However, the system stores a large number of user parameters, making the efficiency low. Concerning switching authentication, researchers transmitted data through broadcast according to the distributed characteristics of blockchain, which reduced the dependence on routing protocols [17]. However, these studies limit the prerequisite conditions of authentication. Not all types of switched authentication can achieve high efficiency. To tackle these challenges, this paper proposes a blockchain-based authentication protocol using cryptocurrency technology (BAPC) that not only solves the problem of difficult certificate management by using blockchain and cryptocurrency technology, but also enables the satellite to independently access authentication without being affected by routing protocols. It is suitable for various types of switching authentication. The main contribution of this paper is summarized as follows. 1. The registration stage, initial authentication stage and switching authentication stage of access authentication are designed, and the cryptocurrency technology is introduced. It not only improves the security of authentication, but also improves the efficiency of switching authentication. Therefore, cryptocurrency plays an important role in these three stages.