Got a little confused.

What I know is, according to RFC 9370, the initiator is not allowed to prepare 
the following ADDKEs, as beside NONE, any other KEM cannot be duplicated in two 
or multiple ADDKEs.

addke1=kem1,kem2
addke2=kem1,kem2,none

Guilin

From: Songbo Bu <[email protected]>
Sent: Tuesday, 23 June 2026 10:01 pm
To: Andrew Cagney <[email protected]>
Cc: Wang Guilin <[email protected]>; [email protected]; lilun (F) 
<[email protected]>; [email protected]; [email protected]
Subject: Re: [IPsec] Re: New I-D: 
draft-li-ipsecme-extensions-for-robust-negotiation


Hi Andrew,

Yes, I think you are right. I was reading that case too narrowly.

With:
ADDKE1 = { PQ_KEM_1, PQ_KEM_2 } ADDKE2 = { PQ_KEM_1, PQ_KEM_2, NONE }

the responder can express the outcomes I had in mind, assuming the normal RFC 
9370 rule that the selected non-NONE algorithms are not duplicated:

  *   both: select PQ_KEM_1 in one ADDKE slot and PQ_KEM_2 in the other;
  *   only PQ_KEM_1: select PQ_KEM_1 and NONE;
  *   only PQ_KEM_2: select PQ_KEM_2 and NONE.

So I would retract my “not directly expressible” phrasing for that row.

The remaining implementation-facing point still seems useful: if the 
initiator’s intent is “one mandatory from this set, plus at most one optional 
additional method from the same set”, it should encode that with an explicit 
NONE in the optional ADDKE slot, not by sending repeated mandatory ADDKE lists 
and expecting the responder to repair them. A responder should still reject 
outcomes that require duplicated non-NONE algorithms or an implicit NONE that 
was not proposed.

Best,
Songbo

On Tue, 23 Jun 2026 09:40:09 -0400, Andrew Cagney 
[email protected]<mailto:[email protected]> wrote:

  *   both-or-one, meaning (PQ_KEM_1 AND PQ_KEM_2) OR PQ_KEM_1 OR PQ_KEM_2: not 
directly expressible as one RFC 9370 proposal, as far
as I can tell.

addke1=kem1,kem2
addke2=kem1,kem2,none
?
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