[kwlug-disc] Secure IM news

[Nick Guenther]

Le 23 novembre 2016 21:41:08 HNE, Chamunks <chamunks at gmail.com> a écrit :
>SignalApp is perfectly open they only use GCM for an efficient method
>to
>tell clients where to send the message to p2p. None of the messages
>actually travel through GCM.  This is how android's designed to work

There are multiple layers of openness here. The code is open, but the service is not because they don't federate, and to protect the brand (the argument being that for the non-obsessed-geek crowd, that also protect a security by avoiding imitators) they actively stamp out anyone running even an alternate copy of the server. On top of that, the fact that any part of the infrastructure depends on Google's non-free systems is a lack of openness; isn't one of the core FSF software freedoms the ability to use the software wherever you can? Well, because of the tie into to GCM/Apple Push, you can't run it on BlackBerry 10, you can't run it under Pidgin

>
>The best part of the signal protocol is that unlike the OTR spec, it
>ratchets its keys for every message since its so cheap on the CPU these
>days to make more keys.

Yep! Signal has made great improvements to OTR. I personally think the best change is rather that the ratchet, being based on deterministic algorithms (hashes), supports offline messaging in a way OTR couldn't and therefore couldn't be used (effectively; you could with xabber but it was The Worst Thing) for mobile. Actually, my belief was that OTR also used a different key for each message, but it had to negotiate the key actively with the partner, which is why you had to have an active both-people-online session to use it. Do you know if I'm wrong about that?

I am not sure if you were debating my reluctance with this message. If you were, let me clarify that I'm not reluctant about Signal; it sucks that they have decided they don't have the resources to do federation, but I have peace with that and use and recommend Signal every day. My reluctance is about Matrix claiming "e2e group chats!" without maybe fully thinking through the threat model.