GNSS Anti-Spoofing with Galileo OSNMA Signal Authentication
Cryptographic protection against GNSS spoofing attacks. Eview receivers powered by Septentrio verify every navigation message against the Galileo satellite signal — so your position data can be trusted, not just assumed.
Why GNSS Position Data Cannot Be Trusted Without Authentication
GNSS spoofing is the deliberate transmission of counterfeit satellite signals to deceive a receiver into computing a false position. Unlike jamming — which blocks signals — spoofing silently replaces legitimate data with fabricated coordinates. The receiver appears to function normally while reporting entirely wrong information.
Galileo E1-B coverage — all satellites transmit OSNMA data
No subscription, no license — embedded in Galileo Open Service
Time-Efficient Stream Loss-Tolerant Authentication protocol
Officially operational — EUSPA OSNMA Service Definition published
How OSNMA Verifies Your Position Data
A three-step cryptographic chain from the Galileo constellation to your GNSS receiver — with no impact on positioning performance.
Galileo Broadcasts Signed Navigation Data
Each satellite transmits authentication data — TESLA chain keys and digital signatures — in reserved fields of the E1-B I/NAV message. No performance overhead.
Receiver Extracts Cryptographic Keys
The Septentrio mosaic receiver decodes the OSNMA data stream, accumulates delayed TESLA keys, and synchronises to Galileo System Time within 30–300 s.
Navigation Messages Cryptographically Verified
Using the public root key stored on-device, the OSNMA engine verifies every navigation message. Spoofed signals are flagged before they influence your position.
OSNMA + AIM+: Complete Signal Security
OSNMA authenticates navigation messages. AIM+ detects signal anomalies. Together they cover both spoofing and jamming — including meaconing attacks that bypass cryptographic checks.
OSNMA: Galileo Navigation Message Authentication
Cryptographic verification that satellite signals originate from genuine Galileo infrastructure. Protects against signal fabrication, replay attacks, and navigation data tampering.
- Cryptographic proof on every navigation message
- TESLA lightweight authentication protocol
- E1-B signal — no extra hardware required
- Free, operational — no subscription
AIM+: Advanced Interference Mitigation Plus
Septentrio’s signal-processing engine detects spoofing through power anomaly detection, cross-satellite range validation, and RAIM+ integrity monitoring — catching attacks OSNMA alone cannot (e.g. meaconing).
- Up to 40 dB jamming suppression
- Signal power anomaly detection
- RAIM+ cross-constellation range validation
- Detects meaconing (delayed genuine-signal replay)
- <1 s reacquisition after interference
OSNMA-Enabled Receiver Specifications
All Eview receivers on Septentrio mosaic chipsets support full OSNMA authentication. No firmware upgrade required.
| Parameter | Specification |
|---|---|
| Authentication Signal | Galileo E1-B I/NAV (reserved fields) |
| Authentication Protocol | TESLA (Timed-Efficient Stream Loss-Tolerant Authentication) |
| Root Key | ECDSA P-256 — stored on-device, verified against Galileo Public Key Service |
| Time to First Auth Fix | 30–300 s (depending on operating mode and GST sync) |
| Auth Reacquisition | <1 s after lock re-established |
| OSNMA Service Status | Operational (since July 2025 — EUSPA) |
| Constellations Tracked | GPS, GLONASS, Galileo, BeiDou, NavIC, QZSS (6 systems) |
| RTK Accuracy (H) | 0.6 cm + 0.5 ppm (with OSNMA active) |
| RTK Accuracy (V) | 1 cm + 1 ppm |
| Heading Accuracy (HB51) | 0.15° RMS at 1 m baseline |
| Channels | Up to 789 (mosaic-G5 P3H) / 448 (mosaic-X5) |
| Update Rate | Up to 100 Hz PVT / 20 Hz RTK |
| Interface | UART, USB, Ethernet, CAN (model dependent) |
| Anti-Jamming | AIM+ (up to 40 dB suppression) |
| Operating Temperature | -40°C to +85°C |
Specifications apply to HB51 (mosaic-G5 P3H) and HB52H (mosaic-G5). Contact us for datasheet downloads.
Who Needs GNSS Signal Authentication
Any operation where a false position fix causes financial loss, safety risk, or mission failure.
UAVs & Drones
Spoofed GNSS can redirect a drone mid-flight. OSNMA authentication ensures flight path integrity for inspection, delivery, and survey missions.
Surveying & Mapping
Tampered reference station data propagates errors into every rover measurement. OSNMA secures base station position integrity for cm-accurate surveys.
Agricultural Robots
Autonomous tractors and sprayers operate on GPS guidance across large fields. Spoofed coordinates can cause crop damage or boundary violations.
Marine & Maritime
Vessel positioning in ports and coastal waters are high-value spoofing targets. OSNMA provides authenticated positioning for AIS and navigation.
Precision Timing & 5G
5G base stations and power grids rely on GNSS timing. A spoofed timestamp can desynchronise entire networks. OSNMA verifies timing source authenticity.
eVTOL & Aerospace
Urban air mobility vehicles operating in GNSS-dependent corridors require verifiable position data for safety-critical airspace operations.
OSNMA-Ready GNSS Receivers
Both receivers support full OSNMA authentication, AIM+ anti-jamming, and RTK precision. OSNMA is active out of the box — no firmware upgrade required.
HB51 Multi-Frequency GNSS — RTK, Dual-Antenna Heading & OSNMA
- ChipsetSeptentrio mosaic-G5 P3H
- RTK Accuracy0.6 cm horizontal
- Heading0.15° RMS (1 m baseline)
- Channels789
- OSNMA✓ Native
- AIM+✓ Up to 40 dB
HB52H Ultralight Compact RTK — OSNMA Anti-Spoofing
- ChipsetSeptentrio mosaic-G5
- Form Factor43.8 × 34 mm
- RTK Accuracy0.6 cm horizontal
- Latency<10 ms
- OSNMA✓ Native
- AIM+✓ Active
OSNMA Anti-Spoofing — Common Questions
Everything engineers and integrators ask before specifying an OSNMA-capable GNSS receiver.
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OSNMA (Open Service Navigation Message Authentication) is a cryptographic service broadcast by the Galileo GNSS constellation on the E1-B signal. It uses the TESLA lightweight broadcast authentication protocol with an ECDSA P-256 root key to verify that every navigation message originates from a genuine Galileo satellite and has not been fabricated or modified. A spoofer cannot generate convincing counterfeit signals without access to Galileo’s private cryptographic keys.
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No. OSNMA uses reserved fields in the existing Galileo E1-B I/NAV message structure, so no additional bandwidth is consumed and no changes are made to the navigation payload. RTK accuracy (0.6 cm), update rate (up to 100 Hz), and time-to-first-fix are all unchanged when OSNMA is active.
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No. OSNMA is part of Galileo’s Open Service and is entirely free to use. There is no subscription, no licensing fee, and no registration requirement. Any receiver with hardware and firmware support for OSNMA can access the service the moment it is in view of Galileo satellites.
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OSNMA alone does not protect against meaconing — where genuine Galileo signals are recorded and retransmitted with a time delay. Retransmitted signals pass cryptographic verification because they are authentic. Eview receivers combine OSNMA with Septentrio AIM+, which detects meaconing through signal power analysis and RAIM+ range validation.
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In warm start conditions with retained Galileo System Time (GST), authentication can be established in approximately 30 seconds. In cold start conditions, the OSNMA specification defines a window of 30–300 seconds for full authentication chain synchronisation.
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All Eview receivers based on Septentrio mosaic chipsets support OSNMA natively — including the HB51 (dual-antenna RTK/heading, mosaic-G5 P3H) and HB52H (ultracompact RTK, mosaic-G5). OSNMA is enabled by default and requires no firmware upgrade.
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Yes. UAVs rely exclusively on satellite navigation for autonomous operation. A spoofed position fix can redirect a drone to an unintended location. OSNMA-enabled receivers verify that navigation data originates from genuine Galileo satellites, providing cryptographic assurance for BVLOS operations, delivery drones, and mapping UAVs.
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Galileo OSNMA reached full operational status on 24 July 2025. The OSNMA Service Definition Document (Issue 1.0) was published by EUSPA simultaneously, making Galileo the world’s first GNSS constellation to offer signal authentication as part of its civilian Open Service.
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OSNMA is a constellation-level service providing cryptographic proof that signals originate from genuine Galileo satellites. AIM+ is Septentrio’s proprietary signal-processing technology that detects power anomalies and validates cross-satellite ranges. They are complementary: OSNMA authenticates at the data level, AIM+ detects anomalies at the RF/signal-processing level.
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No. OSNMA uses the same Galileo E1-B signal that any multi-frequency GNSS antenna already receives. Standard GNSS patch or survey antennas with L1/E1 band coverage are sufficient. What is required is a receiver with OSNMA processing — all Septentrio mosaic-family chips include this by default.
Specify OSNMA-Authenticated GNSS in Your Next Design
Talk to our team about the right receiver for your application. Free samples available for qualifying OEM and integration projects.