e228266e3c816ec0f7b713b9e5d9ebca engproc-88-00046.pdf bb87e204fa40e9e417b40997f01bc3b01e108fc5 engproc-88-00046.pdf 427fe070e0fee1b807c4a3f0fd2f20bd7fff1b83269cd903f604b40bae821dd4 engproc-88-00046.pdf Title: Efficient Detection of Galileo SAS Sequences Using E6-B Aiding "2279 Subject: Galileo Signal Authentication Service (SAS) is an assisted signal authentication capability under development by Galileo, designed to enhance the robustness of the European Global Navigation Satellite System (GNSS) against malicious attacks like spoofing. It operates by providing information about some fragments of the unknown spreading codes in the E6-C signal. Unlike other approaches, Galileo SAS uniquely employs Timed Efficient Stream Loss-tolerant Authentication (TESLA) keys provided by Open Service Navigation Message Authentication (OSNMA) in the E1-B signal for decryption, avoiding the need for key storage in potentially compromised receivers. The encrypted fragments are made available to the receivers before the broadcast of the E6-C signal, along with their broadcast time. However, if the receiver lacks an accurate time reference, searching for these fragments—which typically last for milliseconds and have periodicities extending to several seconds—can become impractical. In such cases, the probability of detection is severely diminished due to the excessively large search space that results. To mitigate this, initial estimates for the code phase delay and Doppler frequency can be obtained from the E1-B signal. Nevertheless, the alignment between E1-B and E6-C is not perfect, largely due to the intrinsic inter-frequency biases they exhibit. To mitigate this issue, we can leverage auxiliary signals like E6-B, processed by High Accuracy Service (HAS)-compatible receivers. This is a logical choice as E6-B shares the same carrier frequency as E6-C. This could help in obtaining more precise estimates of the location of the encrypted fragments and improving the probability of detection, resulting in enhanced robustness for the SAS authentication process. This paper presents a comparison of uncertainties associated with the use of the E1-B and E6-B signals, based on real data samples obtained with a custom-built Galileo SAS evaluation platform based on Software Defined Radio (SDR) boards. The results show the benefits of including E6-B in SAS processing, with minimalimplementation cost. Keywords: GNSS; Galileo; SAS; ACAS; authentication; acquisition; snapshot; SDR; bladeRF; E6-B; E6-C Author: Rafael Terris-Gallego, Ignacio Fernandez-Hernandez, José A. López-Salcedo and Gonzalo Seco-Granados Creator: LaTeX with hyperref Producer: pdfTeX-1.40.25 CreationDate: Fri May 16 09:37:24 2025 CEST ModDate: Fri May 16 09:43:14 2025 CEST Custom Metadata: no Metadata Stream: no Tagged: no UserProperties: no Suspects: no Form: none JavaScript: no Pages: 10 Encrypted: no Page size: 595.276 x 841.89 pts (A4) Page rot: 0 File size: 1754883 bytes Optimized: no PDF version: 1.7 name type encoding emb sub uni object ID ------------------------------------ ----------------- ---------------- --- --- --- --------- JINMPK+VnURWPalladioL Type 1 Custom yes yes yes 10 0 LAPMUF+URWPalladioL-Roma Type 1 Custom yes yes yes 16 0 SGWRHE+URWPalladioL-Bold Type 1 Custom yes yes yes 22 0 UGHQIS+URWPalladioL-Ital Type 1 Custom yes yes yes 27 0 CKDDLA+PalatinoLinotype-Bold CID TrueType Identity-H yes yes yes 60 0 CKDDMB+PalatinoLinotype-Roman CID TrueType Identity-H yes yes yes 66 0 CKDDMC+PalatinoLinotype-Italic CID TrueType Identity-H yes yes yes 72 0 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TrueType Identity-H yes yes yes 323 0 CKDFFO+Cambria TrueType WinAnsi yes yes no 329 0 Jhove (Rel. 1.28.0, 2023-05-18) Date: 2025-09-24 03:08:56 CEST RepresentationInformation: engproc-88-00046.pdf ReportingModule: PDF-hul, Rel. 1.12.4 (2023-03-16) LastModified: 2025-09-23 12:54:29 CEST Size: 1754883 Format: PDF Version: 1.7 Status: Well-Formed and valid SignatureMatches: PDF-hul MIMEtype: application/pdf PDFMetadata: Objects: 414 FreeObjects: 1 IncrementalUpdates: 0 DocumentCatalog: PageLayout: SinglePage PageMode: UseNone Outlines: Item: Title: Introduction Destination: section.1 Item: Title: Detecting Galileo SAS Sequences Using Handover from E6-B Destination: section.2 Item: Title: Snapshot Positioning Using E6-B Destination: section.3 Children: Item: Title: E6 Snapshot Size Destination: subsection.3.1 Item: Title: Comparison of E1-B Tracking with E6-B Snapshot Acquisition Accuracy Destination: subsection.3.2 Item: Title: Results Destination: section.4 Children: Item: Title: Evaluation Platform and Test Samples Destination: subsection.4.1 Item: Title: E6-C vs. E6-B Code Phase Delay Comparison Destination: subsection.4.2 Item: Title: E6-B Snapshot Code Phase Delay Estimation Destination: subsection.4.3 Item: Title: Conclusions Destination: section.5 Item: Title: References Destination: section.6 Info: Title: Efficient Detection of Galileo SAS Sequences Using E6-B Aiding "2279 Author: Rafael Terris-Gallego, Ignacio Fernandez-Hernandez, José A. López-Salcedo and Gonzalo Seco-Granados Subject: Galileo Signal Authentication Service (SAS) is an assisted signal authentication capability under development by Galileo, designed to enhance the robustness of the European Global Navigation Satellite System (GNSS) against malicious attacks like spoofing. It operates by providing information about some fragments of the unknown spreading codes in the E6-C signal. Unlike other approaches, Galileo SAS uniquely employs Timed Efficient Stream Loss-tolerant Authentication (TESLA) keys provided by Open Service Navigation Message Authentication (OSNMA) in the E1-B signal for decryption, avoiding the need for key storage in potentially compromised receivers. The encrypted fragments are made available to the receivers before the broadcast of the E6-C signal, along with their broadcast time. However, if the receiver lacks an accurate time reference, searching for these fragments which typically last for milliseconds and have periodicities extending to several seconds can become impractical. In such cases, the probability of detection is severely diminished due to the excessively large search space that results. To mitigate this, initial estimates for the code phase delay and Doppler frequency can be obtained from the E1-B signal. Nevertheless, the alignment between E1-B and E6-C is not perfect, largely due to the intrinsic inter-frequency biases they exhibit. To mitigate this issue, we can leverage auxiliary signals like E6-B, processed by High Accuracy Service (HAS)-compatible receivers. This is a logical choice as E6-B shares the same carrier frequency as E6-C. This could help in obtaining more precise estimates of the location of the encrypted fragments and improving the probability of detection, resulting in enhanced robustness for the SAS authentication process. This paper presents a comparison of uncertainties associated with the use of the E1-B and E6-B signals, based on real data samples obtained with a custom-built Galileo SAS evaluation platform based on Software Defined Radio (SDR) boards. The results show the benefits of including E6-B in SAS processing, with minimalimplementation cost. 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