Galileo satellites provide first authenticated civil GNSS timing solution
First Galileo SAS Authenticated Time Solution
Cryptography and Security
Summary
Civil GPS signals are vulnerable to fake signals that can trick devices into wrong time or position. Galileo uses cryptographic methods to verify some parts of the signal, but the timing codes were not protected. The authors show for the first time how timing information from Galileo’s new authenticated Signal Authentication Service can be used to get a verified time reading from civil signals. They tested this method with real radio signals and confirmed it can produce trustworthy timing even before full deployment of the service.
What this means in practice
- •For aviation navigation teams: Use authenticated timing from Galileo SAS signals to improve the security of civil aviation timing systems where position is unavailable.
- •For maritime communication providers: Implement verified time synchronization in maritime systems relying on civil GNSS signals vulnerable to spoofing near conflict zones.
Authors
Aleix Galan-Figueras, Ignacio Fernandez-Hernandez, Wim De Wilde, Rafael Terris-Gallego, Gonzalo Seco-Granados, Cillian O'Driscoll, Sibren De Bast, Sofie Pollin
Abstract
Spoofing attacks against civilian GNSS receivers have grown more common, especially near conflict zones where they now disrupt civil aviation, maritime operations, and critical infrastructure on a daily basis. Spoofing is possible because legacy civil GNSS signals are largely predictable in both their navigation data and ranging codes, allowing an attacker to forge a signal that imposes a false position and time on an unsuspecting receiver. Cryptographic authentication schemes such as Galileo's Open Service Navigation Message Authentication (OSNMA) mitigate this threat by verifying the authenticity of the navigation data. The ranging code itself, however, remains unprotected. To close this gap, Galileo is introducing a Signal Authentication Service (SAS) in the E6-C signal, which directly authenticates ranging measurements. SAS is currently transmitted by only two satellites in an elliptical orbital plane, of which at most one is visible at a time, meaning a full position solution is not yet possible; however, a georeferenced receiver can still obtain an authenticated time solution. This paper presents, to the authors' knowledge, for the first time, a timing solution computed from an authenticated civil GNSS signal. We develop a snapshot software receiver implementing a simplified version of the Galileo SAS protocol to compute the receiver clock bias from an authenticated pseudorange, using radio-frequency data recorded with an engineering prototype software-defined radio receiver from Septentrio. We evaluate the resulting timing solution using recordings from both SAS-capable satellites collected at different locations, demonstrating the feasibility of authenticated timing ahead of full SAS operational deployment.