Privacy

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Is Telegram really an encrypted messaging app? (blog.cryptographyengineering.com)

submitted 3 months ago by [email protected] to c/[email protected]

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Blog post by crypto professor Matthew Green, discussing what Telegram does (I wasn't familiar with it) and criticizing its cryptography. He says Telegram by default is not end-to-end encrypted. It does have an end-to-end "secret chat" feature, but it's a nuisance to activate and only works for two-person chats (not groups) where both people are online when the chat starts.

It still isn't clear to me why Telegram's founder was arrested. Green expresses some concern over that but doesn't give any details that weren't in the headlines.

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[–] [email protected] 11 points 3 months ago (1 children)

Telegram’s encryption isn’t open source, so no one can verify it’s soundness or risks.

This is not true, it is available in the open-source Telegram clients.

What you probably mean is that it is using an unusual and not well studied encryption algorithm. This means you need to be a real cryptography expert to spot flaws in it.

Telegram justifies this with a bit of FUD about well known encryption algorithm being NSA sponsored etc, but when cryptography experts did look at Telegram's homegrown algorithm they were less than impressed.

[–] [email protected] -2 points 2 months ago (1 children)

As I recall, Telegram put up bounties for people actually demonstrating exploits in its encryption. Have any of these cryptography experts actually shown exploits?

[–] [email protected] 1 points 2 months ago* (last edited 2 months ago) (1 children)

telegram put up bounties relating to specific properties of their encryption, yes but there’s more to private messaging than just encryption… for example afaik it’s trivial to do things like replay attacks

their encryption may not be flawed, but they failed to design an algorithm that protects against the wide array of modern attacks, as they are mathematicians; not security experts. they understood the maths, but not the wider scope of implementation

a good example of these is linked down thread about MLS

Security properties of MLS include message confidentiality, message integrity and authentication, membership authentication, asynchronicity, forward secrecy, post-compromise security, and scalability.

the telegram bounties afaik only cover 1 security property

[–] [email protected] -2 points 2 months ago (1 children)

But can you provide an example of an actual flaw being demonstrated by anybody with or without a bounty?

[–] [email protected] 1 points 2 months ago* (last edited 2 months ago) (1 children)

i neither have the time nor inclination to research to that degree - i’m merely saying that the bounties prove very little, and change nothing about how people should treat non-standard protocols and algorithms. in fact, the lack of substance is proof that they don’t fully understand the scope of what’s required in the field of security

[–] [email protected] 0 points 2 months ago

And I'm saying that despite people constantly throwing shade on the protocol, nobody has actually showed any flaws in it over many years. The whole dogma that non-standard protocols and algorithms should be shunned out of principle is just that. Meanwhile, plenty of exploits have been found in standard protocols. Not only that there are known cases where US security agencies introduced exploits into popular protocols. https://www.theverge.com/2013/12/20/5231006/nsa-paid-10-million-for-a-back-door-into-rsa-encryption-according-to