*   NIST don't mind hybrids.
True, but my impression from past conversations with NIST (as well as multiple 
regulators around the world, albeit with some exceptions) is that they see 
hybrids (and composites) as a temporary/transitional solution at best, with the 
goal of getting to pure PQC.


  *   There is also one particular set of purchasing requirements for US 
National Security systems (CNSA) that mandates pure PQC [1], where my 
impression [2] is strongly that this is not just to avoid "double migration" 
but perhaps even more so to simply reduce the number of algorithms they need to 
keep track of.
Without speculating about CNSA's motivation, it is true that if CNSA TLS 
profile (https://datatracker.ietf.org/doc/draft-becker-cnsa2-tls-profile/) were 
updated to add hybrid groups, there would be less immediate interest from MSFT 
side in advancing draft-ietf-tls-mlkem.

Cheers,

Andrei

From: Thom Wiggers <[email protected]>
Sent: Tuesday, March 3, 2026 12:28 AM
To: Loganaden Velvindron <[email protected]>
Cc: <[email protected]> <[email protected]>
Subject: [EXTERNAL] [TLS] Re: Proposed Text on hybrid vs non-hybrid | Re: WG 
Last Call: draft-ietf-tls-mlkem-05 (Ends 2026-02-27)

Hi Loganaden,


Op 3 mrt 2026, om 05:35 heeft Loganaden Velvindron 
<[email protected]<mailto:[email protected]>> het volgende geschreven:

Alternatively, if NIST could support hybrids officially, a lot of the
current issues would go away ?

NIST don't mind hybrids. It's SDOs in e.g. Canada and the UK that are sending 
strong messaging that "double" migrations are potentially very costly and 
risky, and thus urge people to consider a direct-to-pure-PQ migration.  There 
is also one particular set of purchasing requirements for US National Security 
systems (CNSA) that mandates pure PQC [1], where my impression [2] is strongly 
that this is not just to avoid "double migration" but perhaps even more so to 
simply reduce the number of algorithms they need to keep track of.

People who mind hybrids mostly appear to do so for "soft" reasons rather than 
"hard" technical reasons. Arguing how practical/fast/small hybrids are, and 
that they shouldn't mind them, isn't really a convincing argument for them.

Regards,

Thom


[1] CNSA 2.0 has one exception for when hybrids are absolutely necessary for 
compatibility reasons: my understanding is that this caveat exists basically 
just for IKEv2.
[2] Clearly I'm not an American nor do I work for the NSA, so I can't speak for 
them
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