Implement Omemo / Axolotl

It would be so great if ChatSecure supported Conversation's Omemo protocol for multi-party, multi-device OTR.

[chrisballinger]

It's on the roadmap! 🎉

[tristan-k]

Soon we will be implementing OMEMO Encryption in ChatSecure iOS, and immediately contributing our OMEMO XEP code upstream to XMPPFramework so that other apps can benefit. We plan to utilize the pre-existing Objective-C library AxolotlKit, written by Frederic Jacobs, that has been used in production since the release of Open Whisper System’s Signal v2.0 for iOS. Unfortunately AxolotlKit is still currently GPL (and therefore not redistributable to the App Store) so this work is on hold until we can negotiate a change to an App Store-comptible copyleft license like LGPLv2 or MPL 2.0 from Fred and Moxie.

Written by Chris Ballinger — OCTOBER 02, 2015

Any update on this matter? Even though AxolotlKit is not redistributable in the App Store, why not make it possible to sideload the app for the more tech-savvy people?

[therob84]

I am also waiting very eagerly that Conversations will get another app which supports OMEMO/Axolotl over XMPP.

Any news about this for chatsecure/ZOM (esp. for iOS) as the last official announcement is from october 2015

[chrisballinger]

This work is semi-permanently on hold because of the license conflict. Moxie said that the public specification for Axolotl is incomplete, so it will be impossible for us to produce an alternative implementation that isn't a derivative work of one of the GPL libraries.

[amenk]

Can you explain? Isn't this thing here GPL? And why can't you use their axolotl implementation?

[amenk]

Okay. I read above that AppStore does not allow GPL.. Sorry for the noise

[therob84]

Thanks for clarification, Chris!
Although I like the idea that AppleIstore is/do not allowed to use GPL software, in this special case it is a pain, that the great OMEMO (Axolotl) protocol cannot be ported to any of the iOS Apps.....and thus is been hindered to become a more widespread alternative for XMPP...at least for iPhone users...which I unfortunately have in my circle of friends...

@chrisballinger Do you think there will be a breakthrough in porting OMEMO to any iOS App in the next....months? Or should we lay it to the graves?

btw: What I don't understand: e.g. Whattsapp also uses Axolotl encryption of TextSecure/Signal/OpenWhisperSystem, which also should be licensed under GPL, but is allowed in the AppleStore?
Where is the difference? Here are some more infos about, but not that I do understand it in detail :-/

[amenk]

@therob84 It thinks WhatsApp does not encrypt end-to-end when chatting with iOS users
https://www.quora.com/Is-WhatsApp-encrypted-for-iPhone

[therob84]

OK, for Whattsapp this could be true. But what's about Signal/OpenWhisperSystem in general, which I think uses E2E encryption at iOS? https://whispersystems.org/blog/the-new-signal/ It is stated for iOS that also group messages are E2Eenc, which means they have to use Axolotl, right? (Is here a difference in XMPP and non-XMPP in this legal-stuff?)

[chrisballinger]

Open Whisper Systems owns the full copyright on AxolotlKit so they can relicense it for distribution on the App Store for their own apps. They are currently licensing libaxolotl-java to WhatsApp for the Android version, but for whatever reason haven't yet done the same for WhatsApp iOS and AxolotlKit. I've been told there are no near-term plans to license AxolotlKit to other apps.

However, there may be a light at the end of the tunnel: https://github.com/SilentCircle/libsalamander

It appears that the Silent Circle team has implemented their own version of Axolotl using only the public specification and (presumably) avoided any reverse engineering of the GPL code. It is licensed Apache 2.0 so it could be used without issue on the App Store. I'm not sure if the key exchange is compatible with libaxolotl-java, among other things, so there is a chance it may not be compatible with Conversations current implementation of OMEMO.