[km-fs-pcs] MLS-TLS: how to decrypt data sent immediately after a resumption request

[Gaëtan Wattiau <[e-mail]>]

Hello,

The MLS-TLS draft says the following:

> Resumption, where initiator or responder can resume a previously

> interrupted connection without having to repeat phase 1,

> including the ability to send data in the first flight of
> messages.

Does that mean the initiator of the resumption can send data without waiting for the ResumptionResponse​?

If that's the case, then it's unclear how the server is meant to decrypt those as it is meant to immediately apply the commit in the ResumptionRequest​ and then create and apply a commit sent back in the ResumptionResponse​:

> The responder receiving a ResumptionRequest MUST validate and apply
> the commit in the ResumptionRequest and create a commit with
> UpdatePath to send back as part of a ResumptionResponse.

(from MLS-2-party profile)

How is the Responder meant to decrypt the data sent by the initiator before the ResumptionResponse​ was processed?

Thanks,

Gaëtan