Transport Layer Security B. E. Westerbaan Internet-Draft Cloudflare Updates: 8446, 9325 (if approved) M. Usama Sardar Intended status: Standards Track TU Dresden Expires: 12 April 2027 9 October 2026 Updated Recommendations for TLS Key Shares draft-westerbaan-tls-keyshare-recommendations-03 Abstract This document updates the TLS Supported Groups registry (previously EC Named Curve Registry) in the light of the future arrival of cryptographically relevant quantum computers: it removes the Recommended status from non-post-quantum key shares. [[ NOTE We use key share in the title and here as it's more accurate than "group" and perhaps more well known in the context TLS than key agreement or key exchange. ]] About This Document This note is to be removed before publishing as an RFC. The latest revision of this draft can be found at https://bwesterb.github.io/draft-westerbaan-tls-keyshare- recommendations/draft-westerbaan-tls-keyshare-recommendations.html. Status information for this document may be found at https://datatracker.ietf.org/doc/draft-westerbaan-tls-keyshare- recommendations/. Discussion of this document takes place on the Transport Layer Security Working Group mailing list (mailto:tls@ietf.org), which is archived at https://mailarchive.ietf.org/arch/browse/tls/. Subscribe at https://www.ietf.org/mailman/listinfo/tls/. Source for this draft and an issue tracker can be found at https://github.com/bwesterb/draft-westerbaan-tls-keyshare- recommendations. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Westerbaan & Usama Sardar Expires 12 April 2027 [Page 1] Internet-Draft Updated Recommendations for TLS Key Shar October 2026 Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. 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Code Components extracted from this document must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Conventions and Definitions . . . . . . . . . . . . . . . . . 3 3. Security Considerations . . . . . . . . . . . . . . . . . . . 3 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 3 5. References . . . . . . . . . . . . . . . . . . . . . . . . . 3 5.1. Normative References . . . . . . . . . . . . . . . . . . 3 5.2. Informative References . . . . . . . . . . . . . . . . . 4 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction A future cryptographically relevant quantum computer (CRQC) [RFC9794] can decrypt TLS handshakes recorded today that do not use post- quantum algorithms for their key shares: algorithms designed to be resistant against quantum attack. This threat is known as "harvest now, decrypt later" (HNDL) [I-D.ietf-pquip-pqc-engineers]. Westerbaan & Usama Sardar Expires 12 April 2027 [Page 2] Internet-Draft Updated Recommendations for TLS Key Shar October 2026 To address this threat, this document updates the TLS Supported Groups registry (https://www.iana.org/assignments/tls-parameters/tls- parameters.xhtml#tls-parameters-8) as defined in Section 6 of [RFC9847]: it removes the Recommended status from non-post-quantum key shares by setting them to N. 2. Conventions and Definitions 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. 3. Security Considerations Before the arrival of a CRQC, a TLS connection that negotiated a non- post quantum key share can be recorded to be decrypted in the future. After the arrival of a CRQC, allowing a non-post quantum key share to be negotiated allows for eavesdrop or an active quantum attack that achieves MITM or impersonation, even if the server certificate is post quantum. 4. IANA Considerations This document updates the TLS Supported Groups registry (https://www.iana.org/assignments/tls-parameters/tls- parameters.xhtml#tls-parameters-8), according to the procedures in Section 6 of [RFC9847] as follows. +=======+=============+=============+ | Value | Description | Recommended | +=======+=============+=============+ | 23 | secp256r1 | N | +-------+-------------+-------------+ | 24 | secp384r1 | N | +-------+-------------+-------------+ | 29 | x25519 | N | +-------+-------------+-------------+ | 30 | x448 | N | +-------+-------------+-------------+ Table 1 5. References 5.1. Normative References Westerbaan & Usama Sardar Expires 12 April 2027 [Page 3] Internet-Draft Updated Recommendations for TLS Key Shar October 2026 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018, . [RFC9325] Sheffer, Y., Saint-Andre, P., and T. Fossati, "Recommendations for Secure Use of Transport Layer Security (TLS) and Datagram Transport Layer Security (DTLS)", BCP 195, RFC 9325, DOI 10.17487/RFC9325, November 2022, . [RFC9847] Salowey, J. and S. Turner, "IANA Registry Updates for TLS and DTLS", RFC 9847, DOI 10.17487/RFC9847, December 2025, . 5.2. Informative References [I-D.ietf-pquip-pqc-engineers] Banerjee, A., Reddy.K, T., Schoinianakis, D., Hollebeek, T., and M. Ounsworth, "Post-Quantum Cryptography for Engineers", Work in Progress, Internet-Draft, draft-ietf- pquip-pqc-engineers-14, 25 August 2025, . [RFC9794] Driscoll, F., Parsons, M., and B. Hale, "Terminology for Post-Quantum Traditional Hybrid Schemes", RFC 9794, DOI 10.17487/RFC9794, June 2025, . Authors' Addresses Bas Westerbaan Cloudflare Email: bas@cloudflare.com Muhammad Usama Sardar TU Dresden Email: muhammad_usama.sardar@tu-dresden.de Westerbaan & Usama Sardar Expires 12 April 2027 [Page 4]