## 1 Introduction  
With the Global Navigation Satellite System (GNSS) being widely used in power grids, finance, transportation and communication networks, and other livelihoods and key infrastructures, human life is becoming increasingly dependent on the navigation, positioning, and timing (PNT) services provided by satellite navigation [1]. However, the structure of satellite navigation signals is open, and there is a security risk of spoofing attacks, which makes the credibility of GNSS services increasingly prominent [2]. In recent years, GNSS spoofing incidents have occurred frequently [3, 4]. How to solve the problem of the anti-spoofing of GNSS services and improve the credibility of user PNT services will be an important developmental direction in the future. For the GNSS anti-spoofing problem, the common method is to add more sensors [5, 6], more antennas, and more complex algorithms [7, 8] into the user terminal to improve the user's anti-spoofing ability. Satellite navigation signal authentication technology is an anti-spoofing technology on the GNSS system side [9]. By adding cryptographic markers to satellite navigation signals, the receiver can verify whether the satellite navigation signals are from real satellites and whether the signals/messages have been tampered with [10]. At present, the construction of four major global navigation satellite systems has been completed. The addition of navigation signal authentication services requires appropriate modifications to the existing satellite navigation systems. On the one hand, it involves the existing system architecture, Interface Control Document (ICD), and cryptographic standards of various countries, and it is necessary to take into account the existing system design. On the other hand, GNSS has been applied on a large scale, and the navigation signal authentication service cannot affect the existing navigation and positioning service. The Galileo System announced the navigation authentication service plan in 2016, providing Open Service Navigation Message Authentication (OSNMA) [11; 12] at the Galileo-E1B. The test signals are now available, and formal services will be provided in 2023 [13]. The Japanese Quasi-Zenith Satellite System (QZSS) [14] and the Navigation with Indian Constellation (NavIC) [15] have both performed the on-orbit testing and verification of navigation message authentication technology. In addition, the United States has proposed the concept of Chips Message Robust Authentication (CHIMERA), and plans to carry out technology tests in 2023 on Navigation Technology Satellite-3 (NTS-3) [16]. In view of anti-spoofing, EU scholars summarized the technical methods of signal authentication in 2017, evaluated different authentication protocols, and looked forward to the authentication services of the GNSS system in the future [17]. In 2021, The Resilience Technical Subgroup of the U.S.-EU Working Group C (WGC-RESSG) summarized the existing the Satellite-Based Augmentation System (SBAS) authentication protocol, in order to add SBAS message authentication in the next version of the Dual Frequency Multi Constellation (DFMC) standard [18]. China's Beidou navigation satellite system (BDS) has completed the system construction in 2020 [19], and plans to conduct the design and development of the next-generation Beidou navigation system in 2022. One of its core goals is to provide more secure and credible PNT services [20]. The main contribution of this article is to design a service architecture for next-generation BDS authentication and analyze the corresponding technical challenges. The paper is organized as follows: Section 2 expounds the principles and technical architecture of satellite navigation signal authentication and focuses on the analysis of the satellite navigation signal authentication technology and navigation message authentication protocol, as well as the new capabilities brought by the navigation signal authentication service.