| Internet-Draft | Updated recommendations for TLS keyshare | April 2026 |
| Westerbaan | Expires 16 October 2026 | [Page] |
This document recommends X25519MLKEM768, SecP256r1MLKEM768 and SecP384r1MLKEM1024 for use in TLS by updating their entries in the TLS Supported Groups registry (previously EC Named Curve Registry) to Recommended in the light of the future arrival of cryptographically relevant quantum computers.¶
[[ NOTE I 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. ]]¶
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/.¶
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Source for this draft and an issue tracker can be found at https://github.com/bwesterb/draft-westerbaan-tls-keyshare-recommendations.¶
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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].¶
To address this threat, this document updates the TLS Supported Groups registry to mark the post-quantum key shares X25519MLKEM768, SecP256r1MLKEM768 and SecP384r1MLKEM1024 as Recommended (Y) as defined in Section 6 of [RFC9847].¶
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.¶
Before the arrival of a cryptographically relevant quantum computer (CRQC), a TLS connection that negotiated a non-post quantum key share can be recorded decrypted in the future.¶
After the arrival of a CRQC, allowing a non-post quantum key share to be negotiated allows for an active quantum attack that achieves MITM, even if the server certificate is post quantum.¶
This document updates the TLS Supported Groups registry, according to the procedures in Section 6 of [RFC9847] as follows.¶
| Value | Description | Recommended |
|---|---|---|
| 4587 | SecP256r1MLKEM768 | Y |
| 4588 | X25519MLKEM768 | Y |
| 4589 | SecP384r1MLKEM1024 | Y |