Navigation Message Authentication Research Articles

An Enhanced FGI-GSRx Software-Defined Receiver for the Execution of Long Datasets.

The Global Navigation Satellite System (GNSS) software-defined receivers offer greater flexibility, cost-effectiveness, customization, and integration capabilities compared to traditional hardware-based receivers, making them essential for a wide range of applications. The continuous evolution of GNSS research and the availability of new features require these software-defined receivers to upgrade continuously to facilitate the latest requirements. The Finnish Geospatial Research Institute (FGI) has been supporting the GNSS research community with its open-source implementations, such as a MATLAB-based GNSS software-defined receiver `FGI-GSRx' and a Python-based implementation `FGI-OSNMA' for utilizing Galileo's Open Service Navigation Message Authentication (OSNMA). In this context, longer datasets are crucial for GNSS software-defined receivers to support adaptation, optimization, and facilitate testing to investigate and develop future-proof receiver capabilities. In this paper, we present an updated version of FGI-GSRx, namely, FGI-GSRx-v2.0.0, which is also available as an open-source resource for the research community. FGI-GSRx-v2.0.0 offers improved performance as compared to its previous version, especially for the execution of long datasets. This is carried out by optimizing the receiver's functionality and offering a newly added parallel processing feature to ensure faster capabilities to process the raw GNSS data. This paper also presents an analysis of some key design aspects of previous and current versions of FGI-GSRx for a better insight into the receiver's functionalities. The results show that FGI-GSRx-v2.0.0 offers about a 40% run time execution improvement over FGI-GSRx-v1.0.0 in the case of the sequential processing mode and about a 59% improvement in the case of the parallel processing mode, with 17 GNSS satellites from GPS and Galileo. In addition, an attempt is made to execute v2.0.0 with MATLAB's own parallel computing toolbox. A detailed performance comparison reveals an improvement of about 43% in execution time over the v2.0.0 parallel processing mode for the same GNSS scenario.

RTK+OSNMA Positioning for Road Applications: An Experimental Performance Analysis in Finland.

We compare the performance of dual-band (GPS L1/L2 and Galileo E1/E5a) real-time kinematic (RTK) positioning in an open sky and urban scenarios in southern Finland using two different authentication schemes: one using only satellites authenticated by Galileo's open service navigation message authentication (OSNMA) service (which at the moment of our tests led to using only authenticated Galileo satellites) and the other with no authentication. The results show the actual trade-off between accuracy and availability vs. authenticity associated with using only OSNMA-authenticated satellites, while the authentication of only Galileo satellites is possible (e.g., a drop of RTK positioning availability from 96.67 to 86.01% in our open sky and from 73.55 to 18.65% in our urban scenarios, respectively), and an upper bound of the potential performance that could be reached in similar experimental conditions had the authentication of GPS satellites been supported (e.g., an overall 14 cm and 10.20 m 95% horizontal accuracy in our open sky and urban scenarios, with below 30, 20 and 10 cm during 97.39, 96.03 and 92.43% of the time in the open sky and 49.12, 45.96 and 39.63% in the urban scenarios, respectively).

An Experimental Performance Assessment of Galileo OSNMA.

We present Galileo Open Service Navigation Message Authentication (OSNMA) observed operational information and key performance indicators (KPIs) from the analysis of a ten-day-long dataset collected in static open-sky conditions in southern Finland and using our in-house-developed OSNMA implementation. In particular, we present a timeline with authentication-related events, such as authentication status and type, dropped navigation pages, and failed cyclic redundancy checks. We also report other KPIs, such as the number of simultaneously authenticated satellites over time, time to first authenticated fix, and percentage of authenticated fixes, and we evaluate the accuracy of the authenticated position solution. We also study how satellite visibility affects these figures. Finally, we analyze situations where it was not possible to reach an authenticated fix, and offer our findings on the observed patterns.

Satellite Navigation Message Authentication in GNSS: Research on Message Scheduler for SBAS L1.

SBAS is mainly used in civil aviation and navigation, and will be applied to autonomous driving in the future. Given the open signal format of the Satellite Based Augmentation System (SBAS), which exposes security threats such as spoofing attacks, the utilization of SBAS navigation message authentication technology can improve the SBAS anti-spoofing ability from the system side. SBAS message authentication technology has become the future direction of SBAS system development. However, during the initial design of SBAS on L1, message authentication technology was not considered, and the addition of authentication messages will lead to further strain on existing message bandwidth resources. Therefore, in response to the issue of insufficient bandwidth resources after adding authentication messages to SBAS L1, a study on message scheduler for SBAS L1 authentication was conducted. A fixed time sequence dynamic message scheduler for incorporating authentication messages was proposed. This scheduler reduces the frequency of broadcasting clock error parameters to mitigate the impact of adding authentication messages. Furthermore, an optimized fixed time sequence dynamic message scheduler based on SBAS clock error messages was introduced. The results show that the message scheduler can not only improve the flexibility of SBAS message broadcasting, but also shorten the update interval of various types of messages under the premise of meeting the maximum update interval requirement. With minimal impact on the maximum message update interval, it improves the integrity, authenticity, and availability of messages. This approach can increase the effective message ratio in SBAS to over 91%, and the optimal solution reduces the initial user positioning time to 26 s.

Authenticated Timing Protocol Based on Galileo ACAS.

Global navigation satellite systems (GNSSs) provide accurate positioning and timing services in a large gamut of sectors, including financial institutions, Industry 4.0, and Internet of things (IoT). Any industrial system involving multiple devices interacting and/or coordinating their functionalities needs accurate, dependable, and trustworthy time synchronization, which can be obtained by using authenticated GNSS signals. However, GNSS vulnerabilities to time-spoofing attacks may cause security issues for their applications. Galileo is currently developing new services aimed at providing increased security and robustness against attacks, such as the open service navigation message authentication (OS-NMA) and commercial authentication service (CAS). In this paper, we propose a robust and secure timing protocol that is independent of external time sources, and solely relies on assisted commercial authentication service (ACAS) and OS-NMA features. We analyze the performance of the proposed timing protocol and discuss its security level in relation to malicious attacks. Lastly, experimental tests were conducted to validate the proposed protocol.

Protecting GNSS Open Service Navigation Message Authentication Against Distance-Decreasing Attacks

As the security of global navigation satellite systems (GNSSs) for civilian usage is increasingly important, navigation message authentication (NMA) significantly improves resilience to spoofing attacks. However, not all attacks can be effectively countered: a strong variant of replay/relay attacks, distance-decreasing (DD) attacks, can shorten pseudorange measurements, without manipulating the cryptographically protected navigation message, thus manipulating the position, velocity, and time solution undetected. First, we discuss how DD attacks can tamper with GNSS signals, demonstrating the attack effectiveness on a recorded Galileo signal. DD attacks might introduce bit errors to the forged signals, but the adversary can keep this error rate very low with proper attack parameter settings. Then, based on our mathematical model of the prompt correlator output of the tracking phase at the victim receiver, we find that the correlator output distribution changes in the presence of DD attacks. This leads us to apply hypothesis testing to detect DD attacks, notably a goodness-of-fit (GoF) test and a generalized likelihood ratio test (GLRT), depending on the victim’s knowledge on the DD attacks. Monte Carlo simulations are used to evaluate the detection probability and the receiver operating characteristic curves for two tests, for different adversary configuration and noise settings. Then, we evaluate the effectiveness of the GoF test and the GLRT with a synthesized DD signal. Both tests can detect DD attacks with similar performance in high-signal-to-noise-ratio (SNR) environments. The GLRT detection probability is approximately 20% higher than that of the GoF test in low-SNR environments.

Mapping Bit to Symbol Unpredictability with Application to Galileo Open Service Navigation Message Authentication

<h3>Abstract</h3> This paper investigates the distribution of unpredictable symbols in the open service navigation message authentication (OSNMA) scheme, which introduces cryptographic elements into the Galileo I/NAV message. Prior work has described the forward estimation attack (FEA; Curran &amp; O’Driscoll, 2016), that takes advantage of the forward error correction (FEC) employed by the Galileo E1 OS to ensure that a spoofed receiver correctly decodes the I/NAV message, even if it has been generated with errors in some symbols. In order to defend against such an attack, the receiver can re-encode the navigation message into symbols and compare the symbol error rates for those symbols that are predictable and those that are not. In order to perform this, it is first necessary to know which symbols are unpredictable. This paper presents in detail how this can be achieved, including the impact of the cyclic redundancy check (CRC) on symbol unpredictability.

Galileo OSNMA Public Observation Phase: Signal Testing and Validation

The Public Observation (PO) test phase of the Galileo Open Service Navigation Message Authentication (OSNMA) signal is officially opened since November <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$15^{\text {th}}~2021$ </tex-math></inline-formula> , by the European Union Agency for the Space Programme (EUSPA). During this phase, any interested users is allowed to access the Signal in Space (SIS) for testing purposes, while the crypto material needed to process the message and verify its authenticity is made available on the European GNSS Service Centre (GSC) web portal. This paper describes the processing of the Galileo E1-B navigation message, as observed during the first days of PO. The purpose is to analyze the crypto and authenticated data carried by the SIS and apply the OSNMA protocol to authenticate the navigation message. The SIS has been processed with the NGene real time software receiver which verifies the authenticity of the navigation data, before evaluating the position fix. The work is completed by an assessment of OSNMA-ready receiver performance, mainly in terms of position accuracy.

Binary phase hopping based spreading code authentication technique

Civil receivers of Global Navigation Satellite System (GNSS) are vulnerable to spoofing and jamming attacks due to their signal structures. The Spreading Code Authentication (SCA) technique is one of the GNSS message encryption identity authentication techniques. Its robustness and complexity are in between Navigation Message Authentication (NMA) and Navigation Message Encryption (NME)/Spreading Code Encryption (SCE). A commonly used spreading code authentication technique inserts unpredictable chips into the public spreading code. This method changes the signal structure, degrades the correlation of the spreading code, and causes performance loss. This paper proposes a binary phase hopping based spreading code authentication technique, which can achieve identity authentication without changing the existing signal structure. Analysis shows that this method can reduce the performance loss of the original signal and has good compatibility with the existing receiver architecture.

Detection of replay attacks to GNSS based on partial correlations and authentication data unpredictability

Intentional interference, and in particular GNSS spoofing, is currently one of the most significant concerns of the Positioning, Navigation and Timing (PNT) community. With the adoption of Open Service Navigation Message Authentication (OSNMA) in Galileo, the E1B signal component will continuously broadcast unpredictable cryptographic data. This allows GNSS receivers not only to ensure the authenticity of data origin but also to detect replay spoofing attacks for receivers already tracking real signals with relatively good visibility conditions. Since the spoofer needs to estimate the unpredictable bits introduced by OSNMA with almost zero delay in order to perform a Security Code Estimation and Replay (SCER) attack, the spoofer unavoidably introduces a slight distortion into the signal, which can be the basis of a spoofing detector. In this work, we propose five detectors based on partial correlations of GNSS signals obtained over predictable and unpredictable parts of the signals. We evaluate them in a wide set of test cases, including different types of receiver and spoofing conditions. The results show that one of the detectors is consistently superior to the others, and it is able to detect SCER attacks with a high probability even in favorable conditions for the spoofer. Finally, we discuss some practical considerations for implementing the proposed detector in receivers, in particular when the Galileo OSNMA message structure is used.

Computational Load Analysis of a Galileo OSNMA-Ready Receiver for ARM-Based Embedded Platforms.

Many GNSS applications have been experiencing some constantly growing needs in terms of security and reliability. To address some of them, both GPS and Galileo are proposing evolutions of their legacy civil signals, embedding features of authentication. This paper focuses on the Galileo Open Signal Navigation Message Authentication (OSNMA) and describes its implementation within a real-time software receiver for ARM-based embedded platforms. The innovative contributions of the paper include the software profiling analysis for the OSNMA add on, along with the comparison among performances obtained with different platforms. In addition, specific evaluations on the computational load of the whole receiver complete the analysis. The receiver used for the implementation belongs to the NGene receivers family—real-time fully-software GPS and Galileo receivers, tailored for different platforms and sharing the same core processing. In detail, the paper deals with the introduction of the OSNMA support inside the eNGene, the version of the receiver executable by ARM-based embedded platforms.

Enhanced GNSS Authentication Based on the Joint CHIMERA/OSNMA Scheme

The authentication of the navigation signals can be considered as the contribution of the system to the robustness against spoofing attacks and it is becoming an important requirement for a growing number of user communities. GPS and Galileo systems are proposing evolutions of their civil signals to embed features of authentication. For Galileo, the Open Service Navigation Message Authentication (OSNMA) is integrated in the Galileo E1 OS signal. For the GPS, the Chips-Message Robust Authentication (Chimera) solution, designed for the GPS L1C signal, is foreseen to be tested soon. On the other hand, suitable signal processing techniques can be implemented inside the receiver to monitor the quality of the received signals and protect against spoofing attacks. Such techniques shall work as a complement to the authentication strategies, to further increase the signals’ robustness. Within this context, the paper presents the Joint Chimera/OSNMA scheme , designed to be adopted by a multi-constellation receiver that already exploits both OSNMA and Chimera enhancements. The idea is to further strengthen the robustness with respect to the individual use of the two solutions, to tackle sophisticated spoofing attacks, which are able to avoid detection from navigation message authentication (NMA) techniques. The manuscript proves the high performance of the joint scheme, presenting the results of a wide bench of tests, under different scenarios of spoofing, and user conditions.

Navigation Message Authentication Based on One-Way Hash Chain to Mitigate Spoofing Attacks for GPS L1

Global Navigation Satellite Systems (GNSS) is vulnerable to significant threats such as spoofing attacks. Data and signal authentication can be used as an effective approach to mitigate such security threats. This paper proposes a Navigation Message Authentication (NMA) method based on Timed Efficient Stream Loss-tolerant Authentication (TESLA), which is using one-way encryption chains. The contributions of this paper are two techniques for implementing TESLA using reserved bits for GPS L1 data. The TESLA algorithm is applied to the extracted navigation message of the GPS L1C/A. Due to the flexibility of the GPS L1C message structure, the protocol is also implemented on Civil Navigation signals (CNAV-2) of GPS L1C. In comparison with Elliptic Curve Digital Signature Algorithm (ECDSA), the Authentication Rate (AR) increases to two minutes for each authentication and performance in term of the Authentication Error Rate (AER) is optimized, by using the TESLA method.

SCER Spoofing Attacks on the Galileo Open Service and Machine Learning Techniques for End-User Protection

Spoofing attacks pose a clear cybersecurity risk for all systems relying on Global Navigation Satellite Systems (GNSS) for time synchronization or positioning. Secure Code Estimation and Replay (SCER) spoofing attacks are the most challenging type of spoofing attacks, as these may be problematic even for future GNSS protection systems, like Navigation Message Authentication (NMA) or Spreading Code Authentication (SCA). This is one of the reasons that make the development of complementary protection techniques, like the one proposed in this work, necessary. In the first part of the paper, the spoofing SCER attacks are analyzed in detail for GPS and, particularly, for Galileo. The role of the Galileo Pseudorandom Noise (PRN) intra-satellite non-orthogonality distortion term in hindering the attacks is discussed and a detailed comparison between GPS and Galileo expected quality curves for the SCER attack is provided. A complementary detection method for end-user receivers (assuming NMA is used) against SCER attacks is proposed, based on the application of machine learning and a proposed set of features extracted from the receiver search space, assuming the attacker was not able to null the satellite signal.

BD-II NMA&amp;SSI: An Scheme of Anti-Spoofing and Open BeiDou II D2 Navigation Message Authentication

Due to openness and lack of authentication, like other members of the Global Navigation Satellite System (GNSS) Club, BeiDou-II civilian navigation signals are vulnerable to all kinds of spoofing attacks. As a result, both the positioning and timing functions of BeiDou-II civil satellite navigation are likely to be controlled by the spoofer. In this paper, an anti-spoofing scheme of BeiDou-II Navigation Message Authentication & Spread Spectrum Information (BD-II NMA&SSI) is proposed by using SM cryptographic algorithms and spread spectrum information to resist spoofing attacks. The SM cryptographic algorithms are used for generating authentication information to detect spoofing attacks. The spread spectrum information is to protect the authentication information in the D2 navigation messages from modification. Experimental results show that the scheme guarantees the authenticity of BD-II satellite navigation messages, meets the requirement of anti-spoofing and takes a rather less effect on the satellite navigation system.

ECDSA-Based Message Authentication Scheme for BeiDou-II Navigation Satellite System

This paper proposes a BeiDou-II navigation message authentication scheme to defend against the generating spoofing attacks. In this scheme, a digital signature is generated by the elliptic curve digital signature algorithm and is inserted into the reserved bits of the BeiDou-II navigation message. This signature will verify the integrity and authenticity of the navigation data to avoid entity masquerade and data tampering. Furthermore, the key exchange process is also designed through the short message service or digital certificate. The effectiveness and security of the scheme is evaluated in the simulation. The results indicate that the authentication of BeiDou-II navigation message can be realized in the harsh environment, and the resistance ability of civil BeiDou-II against a spoofing attack could be enhanced by this scheme.

A Navigation Message Authentication Proposal for the Galileo Open Service

GNSS vulnerabilities have become evident in the last decade. Authentication of the GNSS signals and data can be an important building block contributing to mitigating these vulnerabilities. This paper presents a Navigation Message Authentication (NMA) scheme based on the Timed Efficient Stream Loss-tolerant Authentication (TESLA) protocol and a novel concept based on a single one-way chain for all senders and cross-authentication. The paper presents an NMA implementation in the Galileo Open Service (OS) navigation message that should provide similar navigation performance to data-authenticated users and standard non-authenticated users in terms of time to first fix, accuracy, and availability even in difficult reception conditions. The proposal also maintains a high level of signal unpredictability to help receivers protect against replay attacks. The scheme and implementation proposed yield significant improvements compared to the state of the art, offering the opportunity for Galileo to become the reference GNSS in civil navigation authentication. Copyright © 2016 Institute of Navigation