## 3 Development History of Navigation Signal Authentication Technology
### Technical Research  
Research on satellite navigation signal authentication technology focuses on the GNSS, SBAS, and the high-precision augmentation system.  
* GNSS  
In 2003, [PERSON] of the United States first proposed the concept of civil GPS and Wide Area Augmentation System (WAAS) signal authentication by adding encrypted content to the message and spreading code of the GPS/WAAS signal to protect it from spoofing attacks. Three authentication methods are further defined: navigation message authentication, public spreading code authentication, and private spreading code authentication [43]. Along with the design and demonstration of the Galileo system, European scholar [PERSON] put forward the concept of providing navigation authentication services in the Galileo system and the potential market for Galileo navigation authentication in 2004 [44]. In 2005, [PERSON] further proposed the DS and TESLA protocol of NMA, and conducted the simulation experiment of message authentication [45]. At the same time, [PERSON] proposed a navigation authentication design that hides the encrypted signal in the thermal noise signal [46], and the receiver caches the pending authentication to verify after receiving the key. Since 2012, [PERSON] of the University of Texas has used GPS L2C and L5 signals to carry out NMA message design and has proposed a hybrid scheme based on ECDSA and TESLA [47]. Since 2019, relevant Chinese scholars have also carried out technical research on message authentication protocols [48; 49] and spreading code authentication protocols for BDS-2 and BDS-3 [50; 51].  
* SBAS  
In 2016, the European Union launched the EAST (EGNOS Authentication Security Test-bed) project, which aims to evaluate the SBAS authentication scheme and its impact on SBAS performance [52]. In 2019, the Elasticity Technology Group of US-EU Joint Working team jointly promoted the European Geostationary Navigation Overlay Service (EGNOS), WAAS, and other SBAS systems to provide navigation message authentication services [26], carried out ECDSA-I, ECDSA-Q, TESLA-I, and TESLA-Q simulation, and plans to add the message authentication service to the future DFMC standard [53]. In 2021, the United States, Europe, and Japan jointly launched the standardization of SBAS message authentication, and Stanford University in the United States designed the authentication message and Over the Air Rekeying (OTAR) parameters [54; 55]. In 2021, China launched the Beidou Satellite-Based Augmentation System (BDSBAS) navigation message authentication design based on the Chinese commercial cryptographic standard [56; 57]. In 2022, Europe and the United States submitted the first draft of the Standards and Recommended Practices (SARP) for SBAS authentication to promote SBAS authentication services, which involves the SBAS-L1 and SBAS-L5 frequencies.  
* High-Precision Augmentation System  
For GNSS high-precision authentication services, Japanese scholars demonstrated the Precise Point Positioning-Real Time Kinematic (PPP-RTK) authentication service design of the QZSS Centimeter Level Augmentation Service (CLAS) at the Institute of Navigation, in 2019 [58]. The CLAS adopts the message authentication method based on the TESLA protocol. Subsequently, in 2021, the ESA proposed a framework for providing authentication services in Galileo High Accuracy Service (HAS) [59], and evaluated the performances of two authentication protocols, digital signature and TESLA.