[TelegramApp]

Still, there are sometimes valid reasons for not re-using existing solutions.

In our case, we needed something that is both secure and competitive in comparison to mass market solutions in terms of speed, working on weak connections and usability.

Disclaimer: I work for Telegram.

[ge0rg]

It is a really bad idea to compromise security for speed and connection stability. Processing power is a question of scaling the hardware, communication speed is hardly affected by a proper encryption scheme, neither is reliability of the application-layer protocol.

Usability, however, is a different beast. You must compromise security to make a chat application appeal to "regular" users. Still, this is a trade-off that can be clearly communicated to the user and to developers, and does not require a custom crypto protocol. You can achieve the same effects with using existing and tested libraries.

Edit: Disclaimer: I am the developer of the yaxim Android XMPP client and the operator of the public yax.im XMPP server (both available at http://yax.im).

[e12e]

Thank you for the plug for yaxim. I've been searching around for a "good enough" jabber client for android, and while yaxim isn't there yet (for me: no otr support, single server) it looks like it's headed in the right direction!

[finnn]

Have you looked at ChatSecure? It has OTR, multiple servers, all that good stuff. It's not wonderful but it ain't bad (curious to hear what others have to say, I haven't really used much else)

[e12e]

I have it installed, but not really looked at it. My last "burst" use of xmpp was via facebook -- as most of my contacts don't use "plain" jabber right now. Before that I used it a bit for work -- but then rarely on my phone.

Now that google is killing talk in favour of proprietary hangouts, I predict it'll be a while before I'm a serious xmpp user again.

Sadly it's very hard to push process changes when one are in the minority in a group... Thanks for the reminder though, it does look like it full-fills most of my needs (and fixes annoyances I've encountered with other android clients).

[TelegramApp]

MTProto still uses RSA, AES + DH. So I would disagree that what we have here means 'compromising security for speed and stability'. It is rather optimizing for speed and stability, while staying secure.

[ska]

Often in the crypto world, these are exactly the good intentions with which the road to hell(pwnage?) is paved.

Knowing this, I hope you can appreciate why the burden of proof on your unproven team and approach is fairly high.

[micheljansen]

Absolutely, just trying to point out that the original poster raised some valid points that didn't deserved to be dismissed as "ad hominem". I haven't had a chance to dissect your work (but appreciate that you have made that possible in the first place) and I believe extraordinary claims require extraordinary scrutiny :)

[e12e]

How do you improve on OTR?