Because, with cryptography, the onus is on you to prove that your system is secure, not on other people to prove that it is broken. Everyone tells you there are many hints that your system is not secure, and you just go "well you can't prove it isn't, so there".

Do you truly need to ad-hominem attack tptacek? You sound pretty much like pseudoscientists when they blame mainstream science being too rigid and not accepting their groundbreaking theories.

Scientific approach is exactly what I'm calling for here. When a cryptographer resorts to arguments like "this algorithm won't work because it is not common/modern/accepted" without providing an exact way to break it, it doesn't sound like scientific approach to me. It's more like the religious mindset of someone who rigidly worships some limited list of tools (e.g. "NSA Suite B Cryptography") and punishes anyone who is independent enough to deviate from it.

In cryptography, the burden of proof is on the one proposing the system. It's up to the system designer to prove it secure. The reason why we stick to things like encrypt-then-HMAC, rather than rolling our own protocol, is that they HAVE been PROVEN secure. There are rigorous proofs [1,2] that HMAC and encrypt-then-HMAC are secure, assuming the underlying primitive is secure. There are no such proofs for Telegram's protocol, and there are many "smells" indicating attacks are possible, and I'm sure you'll see some actual examples soon.

[1] https://eprint.iacr.org/2006/043.pdf [2] http://cseweb.ucsd.edu/~mihir/papers/oem.pdf

Cryptography is HARD. It's so hard that it's hard to understand how hard it is. A large part of becoming a cryptographer is just learning how hard it is, and that you NEED security proofs, because it's just too easy to screw up.

I understand you're frustrated, but there's no need for the ad hominem attacks. tptacek is giving you good advice. We all want to see good crypto getting used. So why don't we work together to fix it instead of wasting our time defending a broken system? Honestly, replacing your protocol with encrypt-then-HMAC or the protocol from TextSecure isn't that big of a change, and it would make Telegram a lot better. So why not do it?

Pavel, folks here are being hard on you guys because historically, 9 out of 10 times "independent thinkers" who roll out their own crypto stacks get something wrong. That's why if you want to market your app to this crowd, you'll have a hard time selling something that is not what is a currently recommended crypto stack. Emphasizing that it is the NSA who recommends it is just a pasive-aggressive conspiracy theorizing. It may very well be the case that the NSA have ways of cracking their "Suite B", but we have no evidence of that, and if they do, do you really think that your ad-hoc solution would do much better against them?

So as I understand, you do agree that moxie's mock protocol ( http://thoughtcrime.org/blog/telegram-crypto-challenge/ ), which he designed to be as awful as possible, is as secure as Telegram's mtproto? There's no exact way to break it either, it's just as new, it doesn't use 'limited set of tools' too, both don't have any mathematical proofs. By your logic, I can't see how is it different to mtproto then? How do we know you don't have a protocol just like his?

I like this. "I'm calling for a scientific approach". Meaning, we throw out the last 20 years of scientific work on cryptography and start over from first principles, because the weight of the literature is inconvenient for your argument. It's an interesting tactic you've invented, and I'm surprised I haven't seen it in client change denial posts.

Well, when some of this "research" you promote ends up being backdoors planted by NSA (http://reut.rs/192XWwG), one has to be cautious.

Personally, I am more comfortable with 70s algorithms like Diffie-Hellman that have known and well-researched weaknesses. The "modern" algorithms actively promoted by US security firms after 9/11 are not time-tested, to say the least.

A large number of people who know what they are talking about have stated to you in the clearest terms possible that when it comes to cryptography and security systems, it is appropriate to place the burden of proof on the creators. It isn't an opinion, its a fact agreed on by every competent security practitioner on the planet. If you are going to continue to ignore this, no one is going to take anything you say about cryptography seriously.

Its not about dogma, its about safety. The fact that you fail to understand that is a testament to your inability to contribute to a meaningful conversation about security.

I'm sorry but I have to ask:

Can you prove that you indeed are Pavel Durov of VK?