GNSS Authentication and encryption - Revision history

Gema.Cueto at 08:06, 17 February 2021

2021-02-17T08:06:58Z

← Older revision		Revision as of 08:06, 17 February 2021
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	* Communications may be encrypted (e.g. encoded) to keep them secret and make them unreadable to a third party.		* Communications may be encrypted (e.g. encoded) to keep them secret and make them unreadable to a third party.
	* Authentication is an additional mechanism in which communications are digitally signed to verify its authenticity.		* Authentication is an additional mechanism in which communications are digitally signed to verify its authenticity.
	* Authentication and encryption mechanisms are one of the countermeasures which can help to mitigate spoofing attacks.
			Authentication and encryption mechanisms are one of the countermeasures which can help to mitigate spoofing attacks.

	==Encryption==		==Encryption==
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	The encryption can be symmetric (sender and receiver both hold the same secret information) or asymmetric (different information held by the two parties).		The encryption can be symmetric (sender and receiver both hold the same secret information) or asymmetric (different information held by the two parties).

	Current examples of encrypted GNSS signals are GPS P(Y) code~~<ref> E. D. Kaplan and C. Hegarty, Understanding GPS: Principles and Applications-2nd Edition, Chapter 4</ref>~~ for military use, [[Galileo Public Regulated Service (PRS) \| Galileo PRS]] or [[Galileo High Accuracy Service (HAS) \| Galileo HAS]] (this latter will include providing an additional encrypted navigation signal in a E6 band).		Current examples of encrypted GNSS signals are [[GPS Signal Plan \| GPS P(Y)]] code for military use, [[Galileo Public Regulated Service (PRS) \| Galileo PRS]] or [[Galileo High Accuracy Service (HAS) \| Galileo HAS]] (this latter will include providing an additional encrypted navigation signal in a E6 band).

	==Authentication==		==Authentication==

Gema.Cueto: /* Authentication */

2021-02-16T08:18:53Z

Authentication

← Older revision		Revision as of 08:18, 16 February 2021
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	Up until now, the main operational GNSS systems which have considered including authentication capabilities are GPS and Galileo. In the case of [[GPS General Introduction \| GPS]], a Chips-Message Robust Authentication (Chimera) approach, which is a hybrid NMA and spreading code authentication technique has been proposed for use within the new [[GPS Signal Plan\|GPS L1C signal]]. The NMA portion of this scheme is based on a well-established standard, the asymmetric elliptic curve digital signature algorithm (ECDSA) P-224, which simplifies the integration of the scheme into existing GNSS receivers.		Up until now, the main operational GNSS systems which have considered including authentication capabilities are GPS and Galileo. In the case of [[GPS General Introduction \| GPS]], a Chips-Message Robust Authentication (Chimera) approach, which is a hybrid NMA and spreading code authentication technique has been proposed for use within the new [[GPS Signal Plan\|GPS L1C signal]]. The NMA portion of this scheme is based on a well-established standard, the asymmetric elliptic curve digital signature algorithm (ECDSA) P-224, which simplifies the integration of the scheme into existing GNSS receivers.

	In the case of [[Galileo_Open_Service_Navigation_Message_Authentication\|Galileo OS-NMA]]; this feature consists in digitally signing the Open Service Navigation message in the E1 band, making use of forty reserved bits in the Galileo E1B data message and the TESTA protocol, thus keeping the rest of the navigation message unencrypted.		In the case of [[Galileo_Open_Service_Navigation_Message_Authentication\|Galileo OS-NMA]]; this feature consists in digitally signing the Open Service Navigation message in the E1 band, making use of forty reserved bits in the Galileo E1B data message and the TESTA protocol, thus keeping the rest of the navigation message unencrypted. Galileo OS-NMA is under testing phase and plans to be available to the users in the 2022-2023 timeframe.<ref>[https://www.gsa.europa.eu/newsroom/news/tests-galileo-osnma-underway Tests of Galileo OSNMA underway(europa.eu)]</ref>

	==Notes==		==Notes==

Gema.Cueto: /* Authentication */

2021-02-16T08:16:47Z

Authentication

← Older revision		Revision as of 08:16, 16 February 2021
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	Some variations and modifications have been proposed exploiting one or more signal components providing, in general, a high level of robustness against simplistic and intermediate spoofing attacks. This category of spoofing includes all the cases where the spoofer is able to generate asynchronous or synchronous counterfeit signals, but not to predict and/or a-priori generate valid NMA data. In fact, from a spoofer perspective, the cryptographically-protected data are not predictable a-priori and cannot be pre-computed by the spoofer. In this sense, a spoofer unable to generate valid cryptographic data can be easily detected by a receiver that implements the NMA algorithm.		Some variations and modifications have been proposed exploiting one or more signal components providing, in general, a high level of robustness against simplistic and intermediate spoofing attacks. This category of spoofing includes all the cases where the spoofer is able to generate asynchronous or synchronous counterfeit signals, but not to predict and/or a-priori generate valid NMA data. In fact, from a spoofer perspective, the cryptographically-protected data are not predictable a-priori and cannot be pre-computed by the spoofer. In this sense, a spoofer unable to generate valid cryptographic data can be easily detected by a receiver that implements the NMA algorithm.

	Up until now, the main operational GNSS systems which have considered including authentication capabilities are GPS and Galileo. In the case of GPS, a Chips-Message Robust Authentication (Chimera) approach, which is a hybrid NMA and spreading code authentication technique has been proposed for use within the new [[GPS Signal Plan\|GPS L1C signal]]. The NMA portion of this scheme is based on a well-established standard, the asymmetric elliptic curve digital signature algorithm (ECDSA) P-224, which simplifies the integration of the scheme into existing GNSS receivers.		Up until now, the main operational GNSS systems which have considered including authentication capabilities are GPS and Galileo. In the case of [[GPS General Introduction \| GPS]], a Chips-Message Robust Authentication (Chimera) approach, which is a hybrid NMA and spreading code authentication technique has been proposed for use within the new [[GPS Signal Plan\|GPS L1C signal]]. The NMA portion of this scheme is based on a well-established standard, the asymmetric elliptic curve digital signature algorithm (ECDSA) P-224, which simplifies the integration of the scheme into existing GNSS receivers.

	In the case of [[Galileo_Open_Service_Navigation_Message_Authentication\|Galileo OS-NMA]]; this feature consists in digitally signing the Open Service Navigation message in the E1 band, making use of forty reserved bits in the Galileo E1B data message and the TESTA protocol, thus keeping the rest of the navigation message unencrypted.		In the case of [[Galileo_Open_Service_Navigation_Message_Authentication\|Galileo OS-NMA]]; this feature consists in digitally signing the Open Service Navigation message in the E1 band, making use of forty reserved bits in the Galileo E1B data message and the TESTA protocol, thus keeping the rest of the navigation message unencrypted.

Gema.Cueto: /* Encryption */

2021-02-16T08:15:37Z

Encryption

← Older revision		Revision as of 08:15, 16 February 2021
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	The encryption can be symmetric (sender and receiver both hold the same secret information) or asymmetric (different information held by the two parties).		The encryption can be symmetric (sender and receiver both hold the same secret information) or asymmetric (different information held by the two parties).

	Current examples of encrypted GNSS signals are GPS P(Y) code]<ref>~~[E. D. Kaplan and C. Hegarty, 2006]~~ E. D. Kaplan and C. Hegarty, Understanding GPS: Principles and Applications-2nd Edition, Chapter 4.</ref> for military use, [[Galileo Public Regulated Service (PRS) \| Galileo PRS]] or [[Galileo High Accuracy Service (HAS) \| Galileo HAS]] (this latter will include providing an additional encrypted navigation signal in a E6 band).		Current examples of encrypted GNSS signals are GPS P(Y) code<ref> E. D. Kaplan and C. Hegarty, Understanding GPS: Principles and Applications-2nd Edition, Chapter 4</ref> for military use, [[Galileo Public Regulated Service (PRS) \| Galileo PRS]] or [[Galileo High Accuracy Service (HAS) \| Galileo HAS]] (this latter will include providing an additional encrypted navigation signal in a E6 band).

	==Authentication==		==Authentication==

Gema.Cueto: /* Encryption */

2021-02-16T08:14:48Z

Encryption

← Older revision		Revision as of 08:14, 16 February 2021
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	The encryption can be symmetric (sender and receiver both hold the same secret information) or asymmetric (different information held by the two parties).		The encryption can be symmetric (sender and receiver both hold the same secret information) or asymmetric (different information held by the two parties).

	Current examples of encrypted GNSS signals are GPS P(Y) code for military use, [[Galileo Public Regulated Service (PRS) \| Galileo PRS]] or [[Galileo High Accuracy Service (HAS) \| Galileo HAS]] (this latter will include providing an additional encrypted navigation signal in a E6 band).		Current examples of encrypted GNSS signals are GPS P(Y) code]<ref>[E. D. Kaplan and C. Hegarty, 2006] E. D. Kaplan and C. Hegarty, Understanding GPS: Principles and Applications-2nd Edition, Chapter 4.</ref> for military use, [[Galileo Public Regulated Service (PRS) \| Galileo PRS]] or [[Galileo High Accuracy Service (HAS) \| Galileo HAS]] (this latter will include providing an additional encrypted navigation signal in a E6 band).

	==Authentication==		==Authentication==

Gema.Cueto at 08:11, 16 February 2021

2021-02-16T08:11:43Z

@@ Line 11: / Line 11: @@
 * Communications may be encrypted (e.g. encoded) to keep them secret and make them unreadable to a third party.
 * Authentication is an additional mechanism in which communications are digitally signed to verify its authenticity.
 In GNSS, authentication can be defined as the capability of a GNSS receiver to verify the authenticity of the GNSS information and of the entity transmitting it, to ensure that it comes from a trusted source. Authentication is an intrinsic GNSS capability remaining internal to the GNSS receiver.

Gema.Cueto at 07:47, 28 January 2021

2021-01-28T07:47:42Z

← Older revision		Revision as of 07:47, 28 January 2021
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	The basic idea behind authentication and encryption is to ensure that a message is identical to the one transmitted at its origin and that it was generated by a trusted source. Encryption and authentication refer to two interrelated mechanisms to protect communications:		The basic idea behind authentication and encryption is to ensure that a message is identical to the one transmitted at its origin and that it was generated by a trusted source. Encryption and authentication refer to two interrelated mechanisms to protect communications:
	* Communications may be encrypted (e.g. encoded) to keep them secret and make them unreadable to a third party.		* Communications may be encrypted (e.g. encoded) to keep them secret and make them unreadable to a third party.
	* Authentication is an additional mechanism in which communications are digitally signed to verify its authenticity.		* Authentication is an additional mechanism in which communications are digitally signed to verify its authenticity.

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	Different authentication techniques may be considered (unpredictable features at subcarrier or carrier level, as variable pulse shaping, frequency hopping, etc.), however the most promising ones are related to the authentication of the navigation messages.		Different authentication techniques may be considered (unpredictable features at subcarrier or carrier level, as variable pulse shaping, frequency hopping, etc.), however the most promising ones are related to the authentication of the navigation messages.

	Most Navigation Message Authentication (NMA) techniques are based on the Timed Efficient Stream Loss-Tolerant Authentication (TESLA) protocol <ref>I. Fernández-Hernández, V. Rijmen, G. Seco-Granados, J. Simon, I. Rodríguez, and J. David Calle, “A Navi-gation Message Authentication Proposal for the Galileo Open Service,” Navigation, Journal of The Institute of Navigation, vol. 63, no. 1, pp. 85-102</ref>. Some variations and modifications have been proposed exploiting one or more signal components providing, in general, a high level of robustness against simplistic and intermediate spoofing attacks. This category of spoofing includes all the cases where the spoofer is able to generate asynchronous or synchronous counterfeit signals, but not to predict and/or a-priori generate valid NMA data. In fact, from a spoofer perspective, the cryptographically-protected data are not predictable a-priori and cannot be pre-computed by the spoofer. In this sense, a spoofer unable to generate valid cryptographic data can be easily detected by a receiver that implements the NMA algorithm.		Most Navigation Message Authentication (NMA) techniques are based on the Timed Efficient Stream Loss-Tolerant Authentication (TESLA) protocol <ref>I. Fernández-Hernández, V. Rijmen, G. Seco-Granados, J. Simon, I. Rodríguez, and J. David Calle, “A Navi-gation Message Authentication Proposal for the Galileo Open Service,” Navigation, Journal of The Institute of Navigation, vol. 63, no. 1, pp. 85-102</ref>. One of the greatest advantages of this protocol is that it requires low bandwidth to transmit the authentication information, together with a tolerance to data loss in case a message is lost.
			Some variations and modifications have been proposed exploiting one or more signal components providing, in general, a high level of robustness against simplistic and intermediate spoofing attacks. This category of spoofing includes all the cases where the spoofer is able to generate asynchronous or synchronous counterfeit signals, but not to predict and/or a-priori generate valid NMA data. In fact, from a spoofer perspective, the cryptographically-protected data are not predictable a-priori and cannot be pre-computed by the spoofer. In this sense, a spoofer unable to generate valid cryptographic data can be easily detected by a receiver that implements the NMA algorithm.

	Up until now, the main operational GNSS systems which have considered including authentication capabilities are GPS and Galileo. In the case of GPS, a Chips-Message Robust Authentication (Chimera) approach, which is a hybrid NMA and spreading code authentication technique has been proposed for use within the new [[GPS Signal Plan\|GPS L1C signal]]. The NMA portion of this scheme is based on a well-established standard, the asymmetric elliptic curve digital signature algorithm (ECDSA) P-224, which simplifies the integration of the scheme into existing GNSS receivers.		Up until now, the main operational GNSS systems which have considered including authentication capabilities are GPS and Galileo. In the case of GPS, a Chips-Message Robust Authentication (Chimera) approach, which is a hybrid NMA and spreading code authentication technique has been proposed for use within the new [[GPS Signal Plan\|GPS L1C signal]]. The NMA portion of this scheme is based on a well-established standard, the asymmetric elliptic curve digital signature algorithm (ECDSA) P-224, which simplifies the integration of the scheme into existing GNSS receivers.

Gema.Cueto at 07:42, 28 January 2021

2021-01-28T07:42:35Z

← Older revision		Revision as of 07:42, 28 January 2021
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	\|Title={{PAGENAME}}		\|Title={{PAGENAME}}
	}}		}}

	The basic idea behind authentication and encryption is to ensure that a message is identical to the one transmitted at its origin and that it was generated by a trusted source. Encryption and authentication refer to two interrelated mechanisms to protect communications:		The basic idea behind authentication and encryption is to ensure that a message is identical to the one transmitted at its origin and that it was generated by a trusted source. Encryption and authentication refer to two interrelated mechanisms to protect communications:
	* Communications may be encrypted (e.g. encoded) to keep them secret and make them unreadable to a third party.		* Communications may be encrypted (e.g. encoded) to keep them secret and make them unreadable to a third party.
Line 15:		Line 16:
	Different authentication techniques may be considered (unpredictable features at subcarrier or carrier level, as variable pulse shaping, frequency hopping, etc.), however the most promising ones are related to the authentication of the navigation messages.		Different authentication techniques may be considered (unpredictable features at subcarrier or carrier level, as variable pulse shaping, frequency hopping, etc.), however the most promising ones are related to the authentication of the navigation messages.

	Most Navigation Message Authentication (NMA) techniques are based on the Timed Efficient Stream Loss-Tolerant Authentication (TESLA) protocol <ref>[I. Fernández-Hernández, V. Rijmen, G. Seco-Granados, J. Simon, I. Rodríguez, and J. David Calle, “A Navi-gation Message Authentication Proposal for the Galileo Open Service,” Navigation, Journal of The Institute of Navigation, vol. 63, no. 1, pp. 85-102]</ref>. Some variations and modifications have been proposed exploiting one or more signal components providing, in general, a high level of robustness against simplistic and intermediate spoofing attacks. This category of spoofing includes all the cases where the spoofer is able to generate asynchronous or synchronous counterfeit signals, but not to predict and/or a-priori generate valid NMA data. In fact, from a spoofer perspective, the cryptographically-protected data are not predictable a-priori and cannot be pre-computed by the spoofer. In this sense, a spoofer unable to generate valid cryptographic data can be easily detected by a receiver that implements the NMA algorithm.		Most Navigation Message Authentication (NMA) techniques are based on the Timed Efficient Stream Loss-Tolerant Authentication (TESLA) protocol <ref>I. Fernández-Hernández, V. Rijmen, G. Seco-Granados, J. Simon, I. Rodríguez, and J. David Calle, “A Navi-gation Message Authentication Proposal for the Galileo Open Service,” Navigation, Journal of The Institute of Navigation, vol. 63, no. 1, pp. 85-102</ref>. Some variations and modifications have been proposed exploiting one or more signal components providing, in general, a high level of robustness against simplistic and intermediate spoofing attacks. This category of spoofing includes all the cases where the spoofer is able to generate asynchronous or synchronous counterfeit signals, but not to predict and/or a-priori generate valid NMA data. In fact, from a spoofer perspective, the cryptographically-protected data are not predictable a-priori and cannot be pre-computed by the spoofer. In this sense, a spoofer unable to generate valid cryptographic data can be easily detected by a receiver that implements the NMA algorithm.

	Up until now, the main operational GNSS systems which have considered including authentication capabilities are GPS and Galileo. In the case of GPS, a Chips-Message Robust Authentication (Chimera) approach, which is a hybrid NMA and spreading code authentication technique has been proposed for use within the new [[GPS Signal Plan\|GPS L1C signal]]. The NMA portion of this scheme is based on a well-established standard, the asymmetric elliptic curve digital signature algorithm (ECDSA) P-224, which simplifies the integration of the scheme into existing GNSS receivers.		Up until now, the main operational GNSS systems which have considered including authentication capabilities are GPS and Galileo. In the case of GPS, a Chips-Message Robust Authentication (Chimera) approach, which is a hybrid NMA and spreading code authentication technique has been proposed for use within the new [[GPS Signal Plan\|GPS L1C signal]]. The NMA portion of this scheme is based on a well-established standard, the asymmetric elliptic curve digital signature algorithm (ECDSA) P-224, which simplifies the integration of the scheme into existing GNSS receivers.

	In the case of [[~~Galileo OS-NMA~~\|Galileo OS-NMA]]; this feature consists in digitally signing the Open Service Navigation message in the E1 band, making use of forty reserved bits in the Galileo E1B data message and the TESTA protocol, thus keeping the rest of the navigation message unencrypted.		In the case of [[Galileo_Open_Service_Navigation_Message_Authentication\|Galileo OS-NMA]]; this feature consists in digitally signing the Open Service Navigation message in the E1 band, making use of forty reserved bits in the Galileo E1B data message and the TESTA protocol, thus keeping the rest of the navigation message unencrypted.

	==Notes==		==Notes==

Gema.Cueto at 07:04, 15 January 2021

2021-01-15T07:04:13Z

← Older revision		Revision as of 07:04, 15 January 2021
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	Most Navigation Message Authentication (NMA) techniques are based on the Timed Efficient Stream Loss-Tolerant Authentication (TESLA) protocol <ref>[I. Fernández-Hernández, V. Rijmen, G. Seco-Granados, J. Simon, I. Rodríguez, and J. David Calle, “A Navi-gation Message Authentication Proposal for the Galileo Open Service,” Navigation, Journal of The Institute of Navigation, vol. 63, no. 1, pp. 85-102]</ref>. Some variations and modifications have been proposed exploiting one or more signal components providing, in general, a high level of robustness against simplistic and intermediate spoofing attacks. This category of spoofing includes all the cases where the spoofer is able to generate asynchronous or synchronous counterfeit signals, but not to predict and/or a-priori generate valid NMA data. In fact, from a spoofer perspective, the cryptographically-protected data are not predictable a-priori and cannot be pre-computed by the spoofer. In this sense, a spoofer unable to generate valid cryptographic data can be easily detected by a receiver that implements the NMA algorithm.		Most Navigation Message Authentication (NMA) techniques are based on the Timed Efficient Stream Loss-Tolerant Authentication (TESLA) protocol <ref>[I. Fernández-Hernández, V. Rijmen, G. Seco-Granados, J. Simon, I. Rodríguez, and J. David Calle, “A Navi-gation Message Authentication Proposal for the Galileo Open Service,” Navigation, Journal of The Institute of Navigation, vol. 63, no. 1, pp. 85-102]</ref>. Some variations and modifications have been proposed exploiting one or more signal components providing, in general, a high level of robustness against simplistic and intermediate spoofing attacks. This category of spoofing includes all the cases where the spoofer is able to generate asynchronous or synchronous counterfeit signals, but not to predict and/or a-priori generate valid NMA data. In fact, from a spoofer perspective, the cryptographically-protected data are not predictable a-priori and cannot be pre-computed by the spoofer. In this sense, a spoofer unable to generate valid cryptographic data can be easily detected by a receiver that implements the NMA algorithm.

	Up until now, the main operational GNSS systems which have considered including authentication capabilities are GPS and Galileo. In the case of GPS, a Chips-Message Robust Authentication (Chimera) approach, which is a hybrid NMA and spreading code authentication technique has been proposed for use within the new [GPS Signal Plan \| GPS L1C signal]. The NMA portion of this scheme is based on a well-established standard, the asymmetric elliptic curve digital signature algorithm (ECDSA) P-224, which simplifies the integration of the scheme into existing GNSS receivers.		Up until now, the main operational GNSS systems which have considered including authentication capabilities are GPS and Galileo. In the case of GPS, a Chips-Message Robust Authentication (Chimera) approach, which is a hybrid NMA and spreading code authentication technique has been proposed for use within the new [[GPS Signal Plan\|GPS L1C signal]]. The NMA portion of this scheme is based on a well-established standard, the asymmetric elliptic curve digital signature algorithm (ECDSA) P-224, which simplifies the integration of the scheme into existing GNSS receivers.

	In the case of [Galileo OS-NMA \| Galileo OS-NMA]; this feature consists in digitally signing the Open Service Navigation message in the E1 band, making use of forty reserved bits in the Galileo E1B data message and the TESTA protocol, thus keeping the rest of the navigation message unencrypted.		In the case of [[Galileo OS-NMA\|Galileo OS-NMA]]; this feature consists in digitally signing the Open Service Navigation message in the E1 band, making use of forty reserved bits in the Galileo E1B data message and the TESTA protocol, thus keeping the rest of the navigation message unencrypted.

	==Notes==		==Notes==

Gema.Cueto: Created page with "{{Article Infobox2 |Category=Fundamentals |Editors=GMV |Level=Basic |YearOfPublication=2021 |Logo=GMV |Title={{PAGENAME}} }} The basic idea behind authentication and encryptio..."

2021-01-15T07:02:30Z

Created page with "{{Article Infobox2 |Category=Fundamentals |Editors=GMV |Level=Basic |YearOfPublication=2021 |Logo=GMV |Title={{PAGENAME}} }} The basic idea behind authentication and encryptio..."

New page

{{Article Infobox2
|Category=Fundamentals
|Editors=GMV
|Level=Basic
|YearOfPublication=2021
|Logo=GMV
|Title={{PAGENAME}}
}}
The basic idea behind authentication and encryption is to ensure that a message is identical to the one transmitted at its origin and that it was generated by a trusted source. Encryption and authentication refer to two interrelated mechanisms to protect communications:
* Communications may be encrypted (e.g. encoded) to keep them secret and make them unreadable to a third party.
* Authentication is an additional mechanism in which communications are digitally signed to verify its authenticity.

In GNSS, authentication can be defined as the capability of a GNSS receiver to verify the authenticity of the GNSS information and of the entity transmitting it, to ensure that it comes from a trusted source. Authentication is an intrinsic GNSS capability remaining internal to the GNSS receiver.

Different authentication techniques may be considered (unpredictable features at subcarrier or carrier level, as variable pulse shaping, frequency hopping, etc.), however the most promising ones are related to the authentication of the navigation messages.

Most Navigation Message Authentication (NMA) techniques are based on the Timed Efficient Stream Loss-Tolerant Authentication (TESLA) protocol <ref>[I. Fernández-Hernández, V. Rijmen, G. Seco-Granados, J. Simon, I. Rodríguez, and J. David Calle, “A Navi-gation Message Authentication Proposal for the Galileo Open Service,” Navigation, Journal of The Institute of Navigation, vol. 63, no. 1, pp. 85-102]</ref>. Some variations and modifications have been proposed exploiting one or more signal components providing, in general, a high level of robustness against simplistic and intermediate spoofing attacks. This category of spoofing includes all the cases where the spoofer is able to generate asynchronous or synchronous counterfeit signals, but not to predict and/or a-priori generate valid NMA data. In fact, from a spoofer perspective, the cryptographically-protected data are not predictable a-priori and cannot be pre-computed by the spoofer. In this sense, a spoofer unable to generate valid cryptographic data can be easily detected by a receiver that implements the NMA algorithm.

Up until now, the main operational GNSS systems which have considered including authentication capabilities are GPS and Galileo. In the case of GPS, a Chips-Message Robust Authentication (Chimera) approach, which is a hybrid NMA and spreading code authentication technique has been proposed for use within the new [GPS Signal Plan | GPS L1C signal]. The NMA portion of this scheme is based on a well-established standard, the asymmetric elliptic curve digital signature algorithm (ECDSA) P-224, which simplifies the integration of the scheme into existing GNSS receivers.

In the case of [Galileo OS-NMA | Galileo OS-NMA]; this feature consists in digitally signing the Open Service Navigation message in the E1 band, making use of forty reserved bits in the Galileo E1B data message and the TESTA protocol, thus keeping the rest of the navigation message unencrypted.

==Notes==
<references group="footnotes"/>

==References==
<references/>

[[Category:Fundamentals]]