Even the closed source WhatsApp (uses ETE from the Signal guys) and iMessage are arguably less likely to contain cryptographic flaws than Telegram.
Even though you used the words "arguably less likely" to soften your statement, there's no way to check what WhatsApp or iMessage are doing because they're not open source. So even if security researchers want to look at the code or build their own clients, it's not possible. Reverse engineering is possible, but is tedious compared to having the source code. At least the Telegram client code is open source to support examining it.
That said, the criticism of Telegram for using home brewed encryption is appropriate and needs to be mentioned often (hopefully Telegram will change the protocol). Even the authors of this paper state:
> The take-home message (once again) is that well-studied, provably secure encryption schemes that achieve strong definitions of security (e.g., authenticated-encryption) are to be preferred to home-brewed encryption schemes.
In theory you could reverse engineer the binary (which is compiled code), this is how security firms try to understand malware (like stuxnet). But this is pretty hard to do.
The hard part of evaluating cryptographic messaging services isn't binary reversing; it's that evaluating cryptographic constructions is hard. The flaw we're discussing today in Telegram is evident from the documentation, but despite the fact that every cryptographer who has commented on Telegram has had nothing but bad things to say about how it does crypto, nobody connected these particular dots.
Crypto is hard. Next to crypto, reversing a program compiled with a normal compiler is just a speed bump.
The server sofware is closed source too, so we can't check what it does either.
What is your point then when both ends of the communication are closed source?
It seems to me that we could just fork the app and add in any ETE encryption we want. I get that everyone is annoyed at the Telegram people, but there are a bunch of open clients and the encryption we'd want must be independent of the server. For instance I could paste in PGP encrypted messages. Maybe there is some technical reason this wouldn't work?
> Reverse engineering is possible, but is tedious
I think for a security-related application, trusting that the code you have is the one being built and distributed as binary is a huge oversight. I'd argue that sniffing packets and stepping through code is the proper way (of course having code /does/ help with this) Consider: what idiot would put a backdoor in plain sight?
So, no, sniffing packets or stepping through code isn't the best way to do it. Best way is combining docs, source code, covert channel analysis, execution traces, and looking at them all for issues. That's still not even minimum requirement for high assurance security but how many problems are caught that exist in low-assurance source & binary distributed software.
WhatsApp can just turn off encryption when they want, without users knowing:
That's probably what happened in June:
"Investigators said earlier they had detained 16 people in the anti-terror raids after working with U.S. authorities to monitor suspects' communications on WhatsApp Inc.'s messaging service."
http://www.bloomberg.com/news/articles/2015-06-08/belgium-ar...
How good is your C#?
Do you have further sources aside from [1]?
[1] http://www.wired.com/2014/11/whatsapp-encrypted-messaging/
Edit:
Given the down vote(s), I guess I'm missing something obvious.
What I'm getting at is this: If our activities were completely encrypted and we appeared anonymous to WA/FB they couldn't hope to make money.
Would anyone smarter than me care to explain why this isn't the case?
Is the advertising so coarse as to ignore the content of what people say? Are they only propagating information about purchasing and browsing history through the metadata offered by the social network information in order to drive advertising?
All the questions should suggest that I'm genuinely curious and looking to understand, so if you read this and get riled up, instead of downvoting please take twenty seconds to guide me to the truth...