TESLA Update for GNSS SBAS Authentication

Internet-Draft	TESLA Update	October 2025
Moskowitz	Expires 23 April 2026	[Page]

Abstract

This document updates TESLA [RFC4082] to current cryptographic methods for use by the International Civil Aviation Organization (ICAO) in their Global Navigation Satellite System (GNSS) Satellite-based augmentation system (SBAS) authentication protocol. The TESLA updates are to align it with current best practices.¶

Status of This Memo

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Copyright Notice

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1. Introduction

TESLA [RFC4082] (Timed Efficient Stream Loss-Tolerant Authentication) uses the best practices for cryptography when published in 2005. This is quite dated, and any modern use of TESLA needs to adjust to current algorithms and methods.¶

This document focuses on thhe TESLA design targeted by the International Civil Aviation Organization (ICAO) in their Global Navigation Satellite System (GNSS) Satellite-based augmentation system (SBAS) authentication protocol.¶

The SBAS authentication protocol is more than a modern TESLA implementation. It uses a very tightly designed PKI and the C509 certificate encoding [C509-Certificates] to work within the very highly constrained SBAS communication link. The PKI is out-of-scope for this document and is described elsewhere within ICAO.¶

This document is very much a "work in progress", in that various ICAO SBAS documents need to be excised for their technical updates to TESLA. For example, TESLA specifies using a message authentication code (MAC) of all communicated data. SBAS is using HMAC [RFC2104] and KMAC [NIST.SP.800-185].¶

1.1. SBAS use of TESLA

The updating of TESLA in SBAS Authentication is outlined in [SBAS Authentication]. This document is the public source of changes made to TESLA and some of the justifications.¶

2. Terms and Definitions

2.1. Requirements Terminology

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.¶

6. References

6.1. Normative References

[RFC2119]: Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, <https://www.rfc-editor.org/info/rfc2119>.
[RFC4082]: Perrig, A., Song, D., Canetti, R., Tygar, J. D., and B. Briscoe, "Timed Efficient Stream Loss-Tolerant Authentication (TESLA): Multicast Source Authentication Transform Introduction", RFC 4082, DOI 10.17487/RFC4082, June 2005, <https://www.rfc-editor.org/info/rfc4082>.
[RFC8174]: Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, <https://www.rfc-editor.org/info/rfc8174>.

6.2. Informative References

[C509-Certificates]: Mattsson, J. P., Selander, G., Raza, S., Höglund, J., and M. Furuhed, "CBOR Encoded X.509 Certificates (C509 Certificates)", Work in Progress, Internet-Draft, draft-ietf-cose-cbor-encoded-cert-15, 18 August 2025, <https://datatracker.ietf.org/doc/html/draft-ietf-cose-cbor-encoded-cert-15>.
[NIST.SP.800-185]: Kelsey, J., Change, S., Perlner, R., and National Institute of Standards and Technology, "SHA-3 derived functions: cSHAKE, KMAC, TupleHash and ParallelHash", DOI 10.6028/nist.sp.800-185, December 2016, <https://doi.org/10.6028/nist.sp.800-185>.
[RFC2104]: Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-Hashing for Message Authentication", RFC 2104, DOI 10.17487/RFC2104, February 1997, <https://www.rfc-editor.org/info/rfc2104>.
[SBAS Authentication]: Walter, T.W., "Authentication of Satellite-Based Augmentation Systems with Over-the-Air Rekeying Schemes", <https://navi.ion.org/content/70/3/navi.595>.

Acknowledgments

This work is in conjunction with the ICAO SBAS Authention Study Group members. This includes, and is not limited to: Jed Dennis (FAA Consultant), Abdel Youssouf (Eurocontrol), Timo Warns (Airbus), Todd Walter (Stanford) and chair Mikaël Mabilleau (Eurocontrol).¶