Subject: [dispatch] Discussion about Instant Messaging inside the MLS protocol

From: Rohan Mahy <[email-masked]>
Date: Tue, 8 Mar 2022 08:35:18 +0100

Hi,

I just submitted two new drafts about what happens inside the MLS
(Messaging Layer Security) protocol [0]. Many messaging services (Signal,
Telegram, WhatsApp, Wire) use variations on the DoubleRatchet protocol for
end-to-end encryption involving two clients. MLS defines a standardized
layer for end-to-end encrypting communication to an entire group, and was
largely motivated by extending DoubleRatchet security properties
efficiently to groups. Since the contents are encrypted, it seemed valuable
to define a format for basic interoperability for messaging systems.

The main draft [1] is mostly a profile of other things like CPIM and
various MIME headers.
[1] https://www.ietf.org/archive/id/draft-mahy-dispatch-immi-content-00.html
Please note that due to a formatting error as I was submitting, the
multipart/alternative example got truncated. I'm including it at the bottom
of this email.

The companion draft [2] defines two MLS extensions for negotiating MIME
types.
[2]
https://www.ietf.org/archive/id/draft-mahy-dispatch-immi-mls-mime-00.html

MLS has a narrow charter in the security area. [1] has really nothing to do
with the MLS protocol and requires app/art expertise. [2] is an extension
to MLS but has as much to do with MIME as with MLS and needs minimal
security expertise.

Dispatch seems as good a place as any to discuss this, so please have a
look and comment here.
Thanks,
-rohan

-----------
Omitted example from draft-mahy-dispatch-immi-content-00:

Content-type: multipart/alternative; boundary=XcrSXMwuRwk9

--XcrSXMwuRwk9
Content-type: message/cpim

From: <im:[email-masked]>
DateTime: 2022-02-08T22:13:45-00:00
Message-ID: <[email-masked]>

Content-Type: text/plain; charset=utf-8

Test Message
--XcrSXMwuRwk9
Content-type: application/vnd.examplevendor-fancy-im-message

<content of example vendor's fancy proprietary format>
--XcrSXMwuRwk9

*Rohan Mahy  *l  Vice President Engineering, Architecture

Chat: @rohan_wire on Wire

[0] https://www.ietf.org/archive/id/draft-ietf-mls-protocol-13.html

Wire <https://wire.com/en/download/> - Secure team messaging.

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