[km-fs-pcs] Re: Relation to "MLS Targeted Messages"

[Konrad Kohbrok <[e-mail]>]

Hi Gaëtan,

Good question. The reason it’s specified for two parties is mostly simplicity and that it matches or requirements. We could certainly adapt MLS-TLS to work with more than two clients. Two immediate consequences would be that you’d need a corresponding profile that ensures that all parties agree on the order of commits and that you would lose sender authentication, because authentication of messages in the TLS stream is symmetric. 

Sticking with two parties keeps it simple for now. If there is interest in a solution for more parties I’d be happy to discuss what that could look like. 

Konrad

Am 19.06.2026 um 21:38 schrieb Gaëtan Wattiau <gaetan.wattiau=[e-mail]>:



Ok! Thanks for the quick reply. 

I think what I don't understand is why this RFC is so specifically bound to the two-party profile, instead of a more generic: "this is how we generate and roll TLS session keys with MLS". Explaining the rationale for this scope in the introduction would be helpful to newcomers like me.

Gaëtan

On Friday, June 19th, 2026 at 7:08 PM, Raphael Robert <ietf=[e-mail]> wrote:

MLS targeted messages are not a replacement for the MLS 2 party profile, they are really different things.

MLS targeted messages wouldn’t make much sense in a 2 party setting, they were designed for groups with more than two members, because their purpose is to encrypt messages between exactly two members so that the other n-2 members cannot decrypt it.

In other words, there’s no relationship to MLS targeted messages whatsoever. Thank you for the question though, this shows that the text in the current draft could maybe be improved.

Raphael

On 19. Jun 2026, at 19:28, Gaëtan Wattiau <gaetan.wattiau=[e-mail]> wrote:

I just read the MLS-TLS draft, and my understanding is that it is currently centered on a two-party with a two-party profile.

Have you considered a direction where this stays conceptually 1:1 at the messaging layer, but within an MLS group, using something like targeted messages [1] rather than MLS two-party profile?

Best, 

Gaëtan Wattiau

[1]: https://datatracker.ietf.org/doc/draft-ietf-mls-targeted-messages/">https://datatracker.ietf.org/doc/draft-ietf-mls-targeted-messages/

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