Signal Authentication for Anti-Spoofing based on L1S
Dinesh Manandhar, Ryosuke Shibasaki · Proceedings of the ION ... Pacific PNT Meeting/Proceedings of the Institute of Navigation Pacific PNT · 2017
In this paper, we will present how civilian GPS/QZSS signals can be protected against spoofing by authenticating QZSS signal. The signal authentication is based on QZSS L1S (or L1SAIF) signal. QZSS L1S signal is an augmentation signal for sub-meter level accuracy. L1S has the same signal structure as SBAS signal. Signal authentication can be achieved by broadcasting digital signature data using one of the message types in L1S navigation message. The digital signature data are created from certain portions of L1C/A navigation message (GPS or QZSS). These navigation data bits are hashed and encrypted with a private key. The encrypted data are then broadcasted from L1S signal. At the receiver, hashed data are generated from broadcasted L1C/A navigation data bits. This hashed data is then compared with digital signature broadcasted from L1S signal after decryption. If these two hashed data sets are the same, it is decided that L1C/A navigation data are authentic or not spoofed. In order to prove this concept, Proof-of-Concept (POC) tests have been conducted to demonstrate the successfulness of the methodology for anti-spoofing capabilities for QZSS and GPS signals. We propose this signal authentication method for anti-spoofing capability to be implemented in QZSS to provide secured and reliable GNSS based applications.