[Standards] Proposed XMPP Extension: OMEMO Encryption

Dave Cridland dave at cridland.net
Tue Apr 12 18:18:46 UTC 2016

On 12 April 2016 at 17:08, Fabian Beutel <fabian.beutel at gmx.de> wrote:

> Hey everyone,
> as I'm currently trying to implement OMEMO out of curiosity, I wanted to
> bring up a few points that might be of interest to the discussion:
> 1. There still seems to be no real protocol specification, but there has
> been a "whitepaper" by Whatsapp [1] that describes the protocol used,
> which is not suitable as a standards specification but is a nice
> introduction for understanding the protocol - if anyone is interested.
There is, however, "olm", from the Matrix folk. This is a direct copy of
Axolotl, except done as a decent spec and with (I think) a
liberally-licensed reference implementation. Should be fully compatible
with Signal's.

If we can (nominally) switch to Olm, I'm actually quite happy with this
spec (given the current absence of any proxy re-encryption stuff).

> 2. A minor issue, but as you probably know, the people from
> OpenWhisperSystems have renamed their protocol from Axolotl to Signal
> and seem to be eager to push these changes throughaut their repositories.
> An updated OMEMO proposal should probably reflect that change, as
> references to Axolotl may become less clear when the Signal-people
> remove all appearences of the old name.
> 3. There have been discussions on this list to use v2 of the Axolotl
> protocol. However, it seems that the OWS people have removed support for
> v2 from most of their libraries ([2] for the Java lib, [3] for the C
> lib). That could indeed be a problem if v2 would be the default version,
> as probably most people will want to rely on the reference
> implementations...
> Best regards,
> Fabian
> [1] https://www.whatsapp.com/security/WhatsApp-Security-Whitepaper.pdf
> [2]
> https://github.com/WhisperSystems/libsignal-protocol-java/commit/87b5b940fbf9624ad0302721f6e54d7e5250df70
> [3]
> https://github.com/WhisperSystems/libsignal-protocol-c/commit/57d85a0dc81a4e6d59ac20633a08040f57a29ddb
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