Galileo’s OSNMA: out-of-the-box spoofing mitigation for secure and trustworthy public transport navigation

Public transport systems today rely heavily on Global Navigation Satellite Systems (GNSS) for various critical functions, from real-time tracking of buses and trains to providing accurate location information for passengers. However, the vulnerability of GNSS signals to spoofing — where malicious actors transmit false signals to deceive receivers — poses a serious threat. Imagine the chaos if a spoofing attack were to disrupt the timing of trains or misdirect autonomous buses. The consequences could range from operational inefficiencies to severe safety hazards. This is where Galileo's key differentiator, the Open Service Navigation Message Authentication (OSNMA), comes in.

What is OSNMA and why it matters for public transport

OSNMA is a free data authentication function for Galileo Open Service (OS) users available worldwide. It assures GNSS receivers that the Galileo navigation message is genuine and has not been tampered with, acting like a “digital signature”.

OSNMA authenticates geolocation data from the Galileo Open Service via the I/NAV navigation message on the E1-B signal component, which is transmitted alongside the data used by GNSS receivers to compute Position, Velocity, and Time (PVT) solutions. By integrating OSNMA, receivers can detect spoofed signals and respond accordingly.

The introduction of OSNMA has minimal impact on GNSS receivers, as the additional computational load required for cryptographic processing remains well within the capabilities of low-cost receivers – a crucial factor to consider, given that cost is a critical factor in public transport procurements. Furthermore, and just as importantly, OSNMA does not impact navigation performance, which is essential for managing public transport fleets efficiently. OSNMA is compatible with all types of receivers decoding the E1-B signal component. This approach ensures full backward compatibility, meaning that standard OS receivers can continue ignoring the OSNMA dedicated fields of I/NAV and keep functioning with the same performance level. Only OSNMA ready receivers will decode these fields and be able to authenticate Galileo navigation data. In fact, OSNMA is becoming a readily available feature in many GNSS receivers already deployed through simple firmware updates.

By enabling GNSS receivers onboard buses and trains to verify the authenticity of Galileo signals, OSNMA can ensure that the navigation data being used is genuine and untampered. For public transport operators, this means enhanced trust in the systems they rely on daily, leading to more resilient and reliable operations.

JULIA: advancing the uptake of EU space data and services in public transport

JULIA — short for Joint developments for Urban resiLIence connecting users to public transport through spAce technology — is a project funded by the European Union Agency for the Space Programme (EUSPA) under the Horizon Europe programme and coordinated by Factual, seeks to integrate EU Space services and data into the global public transport sector by utilising Galileo, the European Global Navigation Satellite System (EGNSS), and by leveraging Earth Observation data from Copernicus.

JULIA assesses the benefits of using multi-constellation, multi-frequency GNSS receivers integrated into INIT’s COPILOT last generation on-board computer, deployed on both regular as well as Demand Responsive Transit (DRT) bus services, in cooperation with the project partners NEMI (DRT tech provider), Arriva (bus operator) and OASA Transport for Athens (bus and train operator), as well as trains, with FGC and Hellenic Train (train operators). JULIA demonstrates how Galileo differentiators, such as OSNMA (and also HAS – High Accuracy Service), reduce friction in location accuracy while enhancing the security and efficiency of public transport operations. By exploring their benefits across the public transport value chain, JULIA raises awareness and fosters understanding of their potential. Ultimately, this will encourage the adoption of Galileo technology in the public transport sector.

OSNMA Public Observation phase started in November 2021 and concluded in early June 2024 with the last testing activities led by the EUSPA, which is now preparing for the forthcoming OSNMA Initial Service declaration. This timing aligns very well with JULIA, which began in January 2024 and has since explored relevant use cases and conducted preliminary tests with its partners across Spain, Slovenia, and Greece.

As OSNMA reaches maturity, providers of positioning and wireless communication technologies and services like u-blox are releasing firmware updates for OSNMA support, starting with the u-blox ZED-F9P high-precision GNSS module used in INIT’s COPILOT in JULIA. By incorporating OSNMA support, the industry is setting a new standard for GNSS security and reliability.

JULIA will provide evidence of OSNMA effectiveness in public transport through the following applications:

• Trustworthy distance-based fare systems calculate fares based on the distance travelled by a passenger, offering a fair and flexible pricing model that can adapt to varying trip lengths. However, the accuracy and reliability of these systems depend largely on precise and trustworthy positioning data. Imagine a bus system in a bustling urban area that uses distance-based fares. Without OSNMA, a spoofing attack could make it appear as though the bus is traveling a shorter distance than it actually is, leading to undercharging. Over time, this could result in significant financial losses for the operator. With OSNMA, the system can detect and reject spoofed signals, ensuring that fares are calculated accurately and fairly.
• ?Reliable vehicle tracking with Galileo: buses, trams and trains transmit their position in near real-time, which allows the operator to track them. The GNSS position can be used to display its live geographical position through an app and provide users a better Estimated Time of Arrival (ETA). Real-time positioning of vehicles allows fleet operators to detect incidents such as significant delays, detours, and breakdowns as soon as they occur. This enables them to proactively inform passengers and take necessary actions, minimising disruptions and improving the overall passenger experience. Historical aggregated positioning data can help the operator to identify if any segments of the route or the schedules must be modified to optimise the speed of the service. GNSS can also improve low-demand railway lines by providing an accurate and cost-effective way to track trains and manage their movements. In contrast to traditional signalling systems that require physical infrastructure, GNSS can provide position information to trains in real-time, allowing for efficient and safe train control. Furthermore, enhanced vehicle tracking will contribute to operational safety such as bridge warnings (bus), and speed warnings (bus, tram, train) for the driver and at the control centre (through INIT’s MOBILE-ITCS). In addition, active speed adaptation measures (for buses, trams, and trains) will be possible that require precise and authenticated GNSS position data that interacts with the OBUs embarked on the vehicles. By ensuring the authenticity and integrity of GNSS signals, OSNMA will safeguard these critical functionalities, protecting against spoofing attacks that could disrupt operations, misinform passengers, or even compromise safety.

?GNSS data authentication is also crucial for mission-critical applications, such as advanced driver assistance systems (ADAS) and autonomous driving, where the integrity of positioning data is paramount. By ensuring this integrity, OSNMA will help build public trust in modern transport systems. Passengers are more likely to embrace innovations like on-demand shuttles or driverless buses when they are confident in the security of these systems.