Galileo Signal Authentication Service - Revision history

Ignacio.Fernandez: added category tags

2026-09-16T12:34:26Z

added category tags

← Older revision		Revision as of 12:34, 16 September 2026
Line 51:		Line 51:
	==References==		==References==
	<references/>		<references/>

			[[Category:GALILEO\|SAS]]
			[[Category:GALILEO Services\|SAS]]

Ignacio.Fernandez: Images added

2026-09-16T12:22:53Z

Images added

← Older revision		Revision as of 12:22, 16 September 2026
Line 20:		Line 20:

	The core concept of SAS is that, although the RECS can be downloaded in advance, the ECS are only disclosed after their transmission (i.e. after the receiver has already recorded the snapshot). Thus, it is not possible for a spoofer to generate the authentic ECS in advance. As the delayed disclosure of the key vs. the RECS is part of the core concept, sufficiently accurate time synchronisation in the receiver is required, as is the case for OSNMA.<ref>[https://www.gsc-europa.eu/electronic-library/programme-reference-documents/galileo-in-force/osnma Galileo OSNMA Receiver Guidelines]</ref>		The core concept of SAS is that, although the RECS can be downloaded in advance, the ECS are only disclosed after their transmission (i.e. after the receiver has already recorded the snapshot). Thus, it is not possible for a spoofer to generate the authentic ECS in advance. As the delayed disclosure of the key vs. the RECS is part of the core concept, sufficiently accurate time synchronisation in the receiver is required, as is the case for OSNMA.<ref>[https://www.gsc-europa.eu/electronic-library/programme-reference-documents/galileo-in-force/osnma Galileo OSNMA Receiver Guidelines]</ref>

			[[File:SAS_Processing_Steps.png\|800px\|center\|thumb\|Galileo SAS operation. Left: Download RECS from the server. Center: Capture an E6-C snapshot. Right: Decrypt RECS with OSNMA and perform a-posteriori correlation with E6-C snapshot.]]

	==System Level Implementation==		==System Level Implementation==
Line 31:		Line 33:

	Receivers can connect to the SAS server over HTTPS to request RECS, BGD and SLOG files using a query with the desired configuration parameters. The files can be requested for up to one week in advance, so the autonomy period for the user can be up to one week. The files are signed using official Galileo key material and receivers must verify these signatures. The SAS server also acts as an NTS (Network Time Security) server, offering authenticated time synchronisation.		Receivers can connect to the SAS server over HTTPS to request RECS, BGD and SLOG files using a query with the desired configuration parameters. The files can be requested for up to one week in advance, so the autonomy period for the user can be up to one week. The files are signed using official Galileo key material and receivers must verify these signatures. The SAS server also acts as an NTS (Network Time Security) server, offering authenticated time synchronisation.

			[[File:SAS_RECS_Period.png\|450px\|center\|thumb\|Structure of a RECS period]]

	==Receiver Implementation Aspects==		==Receiver Implementation Aspects==

Ignacio.Fernandez: Internal link added, minor updates

2026-09-15T14:25:41Z

Internal link added, minor updates

← Older revision		Revision as of 14:25, 15 September 2026
Line 17:		Line 17:
	The SAS service offers ranging authentication based on the Galileo encrypted E6-C pilot signal component. Before operation, users can download so-called Re-Encrypted Code Sequences (RECS) from the SAS server. These RECS are subsequences of the E6-C encrypted signal, and re-encrypted using an OSNMA key that is only transmitted after the RECS.		The SAS service offers ranging authentication based on the Galileo encrypted E6-C pilot signal component. Before operation, users can download so-called Re-Encrypted Code Sequences (RECS) from the SAS server. These RECS are subsequences of the E6-C encrypted signal, and re-encrypted using an OSNMA key that is only transmitted after the RECS.

	During operation, a receiver records an E6-C signal snapshot of some tens of milliseconds. Then, after a delay, the OSNMA key is received that can be used to decrypt the RECS and to obtain the so called ECS (Encrypted Code Sequence). The receiver can then correlate the ECS with the recorded snapshot for each satellite. Only in case of an authentic E6-C signal, a correlation peak can be found. The process is illustrated in the figure below. By making use of authenticated E6-C pseudoranges and authenticated E1B data, under some assumptions, a signal- and data-authenticated PVT can be obtained. Implementation aspects are discussed ~~further~~ below.		During operation, a receiver records an E6-C signal snapshot of some tens of milliseconds. Then, after a delay, the OSNMA key is received that can be used to decrypt the RECS and to obtain the so-called ECS (Encrypted Code Sequence). The receiver can then correlate the ECS with the recorded snapshot for each satellite. Only in case of an authentic E6-C signal, a correlation peak can be found. The process is illustrated in the figure below. By making use of authenticated E6-C pseudoranges and authenticated E1B data, under some assumptions, a signal- and data-authenticated PVT can be obtained. Implementation aspects are discussed [[#Receiver Implementation Aspects\|below]].

	The core concept of SAS is that, although the RECS can be downloaded in advance, the ECS are only disclosed after their transmission (i.e., after the receiver has already recorded the snapshot). Thus, it is not possible for a spoofer to generate the authentic ECS in advance. As the delayed disclosure of the key vs. the RECS is part of the core concept, sufficiently accurate time synchronisation in the receiver is required, as is the case for OSNMA.<ref>[https://www.gsc-europa.eu/electronic-library/programme-reference-documents/galileo-in-force/osnma Galileo OSNMA Receiver Guidelines]</ref>		The core concept of SAS is that, although the RECS can be downloaded in advance, the ECS are only disclosed after their transmission (i.e. after the receiver has already recorded the snapshot). Thus, it is not possible for a spoofer to generate the authentic ECS in advance. As the delayed disclosure of the key vs. the RECS is part of the core concept, sufficiently accurate time synchronisation in the receiver is required, as is the case for OSNMA.<ref>[https://www.gsc-europa.eu/electronic-library/programme-reference-documents/galileo-in-force/osnma Galileo OSNMA Receiver Guidelines]</ref>

	==System Level Implementation==		==System Level Implementation==
Line 30:		Line 30:
	* The SLOG (SAS Status and Log) files provide SAS status information and related events.		* The SLOG (SAS Status and Log) files provide SAS status information and related events.

	Receivers can connect to the SAS server over HTTPS to request RECS, BGD and SLOG files using a query with the desired configuration parameters. The files can be requested for up to one week in advance, so the autonomy period for the user can be up to one week. The files are signed using official Galileo key material and receivers must verify these signatures. The SAS server also acts as a NTS (Network Time Security) server, offering authenticated time synchronisation.		Receivers can connect to the SAS server over HTTPS to request RECS, BGD and SLOG files using a query with the desired configuration parameters. The files can be requested for up to one week in advance, so the autonomy period for the user can be up to one week. The files are signed using official Galileo key material and receivers must verify these signatures. The SAS server also acts as an NTS (Network Time Security) server, offering authenticated time synchronisation.

	==Receiver Implementation Aspects==		==Receiver Implementation Aspects==

Ignacio.Fernandez: New content

2026-09-15T14:04:08Z

New content

@@ Line 1: / Line 1: @@
 {{Article Infobox2
 |Category=GALILEO
-|Editors=Ignacio Fernández Hernández (European Commission), Tom Willems (CGI, Advisor to the European Commission)
+|Editors=European Commission
 |YearOfPublication=2026
 |Level=Intermediate
@@ Line 7: / Line 7: @@
 }}
-Lorem ipsum...
+The [[GALILEO General Introduction|GALILEO]] System is an independent, global, European-controlled, satellite-based navigation system and provides a number of services to users equipped with Galileo-compatible receivers.<ref>[https://www.gsc-europa.eu/galileo/services Galileo Services on GSC website]</ref>

Natalia.Castrillo: Created page with "{{Article Infobox2 |Category=GALILEO |Editors=Ignacio Fernández Hernández (European Commission), Tom Willems (CGI, Advisor to the European Commission) |YearOfPublication=2026 |Level=Intermediate |Title={{Galileo Signal Authentication Service}} }} Lorem ipsum..."

2026-09-15T08:51:43Z

Created page with "{{Article Infobox2 |Category=GALILEO |Editors=Ignacio Fernández Hernández (European Commission), Tom Willems (CGI, Advisor to the European Commission) |YearOfPublication=2026 |Level=Intermediate |Title={{Galileo Signal Authentication Service}} }} Lorem ipsum..."

New page

{{Article Infobox2
|Category=GALILEO
|Editors=Ignacio Fernández Hernández (European Commission), Tom Willems (CGI, Advisor to the European Commission)
|YearOfPublication=2026
|Level=Intermediate
|Title={{Galileo Signal Authentication Service}}
}}

Lorem ipsum...