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Is Telegram really an encrypted messaging app? (blog.cryptographyengineering.com)
submitted 3 weeks 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] 1 points 3 weeks ago

I mean really, we don't need an entire article to explain how encryption works on Telegram.

  1. Chats by default aren't fully e2e. Your key must be kept on the server(s) to enable instant sync with other devices

  2. There is a full e2e chat, you can enable this at any time. But, it doesn't do groups, it's only between 2 parties, and it doesn't sync across devices.

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

None of this is new info, it's been talked about for 2 years now.

[-] [email protected] 0 points 3 weeks ago

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] -1 points 2 weeks ago

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] 0 points 2 weeks ago* (last edited 2 weeks ago)

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] -1 points 2 weeks ago

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

[-] [email protected] 0 points 3 weeks ago

Are there any programs that can do e2e in a group chat? My limited knowledge of e2e and encryption makes me think that'd be extremely difficult and even clunkier

[-] [email protected] 0 points 3 weeks ago

Signal

[-] [email protected] 0 points 2 weeks ago

Ah yes, the metadata collection app for the NSA.

[-] [email protected] 0 points 2 weeks ago

Isn't Signal's whole thing that they reduce metadata as much as they can? What do you recommend? Matrix and XMPP certainly aren't options if you value metadata protection.

[-] [email protected] 0 points 2 weeks ago

The phone number is the most important piece of metadata, and collecting numbers of people who want to use e2ee and are willing to use an app that's inconvenient, then building graphs of these people and cross referencing the numbers with all the other data the government has is clearly valuable.

Whether other apps are better or worse in terms of collection of metadata is completely irrelevant when evaluating whether Signal itself is safe. However, as far as alternatives go Simplex https://simplex.chat/ seems to be one of the better options.

Even if no chat app protected metadata properly, that's still an important fact to acknowledge. Furthermore, it may be more important for people to protect their metadata from a specific government that has agency over them. If you live in US or a US protectorate, then data being leaked to the US government is your primary concern.

[-] [email protected] 0 points 2 weeks ago

I mean, Signal has over 100 million downloads on the Play Store alone. Even on the odd chance those phone numbers do somehow end up in the hands of the NSA or whatever the chances of it actually relaying any real information about you is second to none.

Even then, you can't assume everyone who uses Signal wants to use e2ee explicitly. Some might just like the app's style, some might have family members who only use Signal, some might have an ethical problem with corporate apps but aren't computer-brained enough to know how SimpleX or Jabber or some other obscure alternative works.

Is the phone number requirement bad? Yes, absolutely. Does that instantly rule out all opportunity for it being a good app, privacy wise? Definitely not.

Further; privacy should be simple. Signal is designed to be as close to perfect as it can be without compromising too much privacy. They have decided that a phone number is necessary to prevent spam, and to combat the privacy implications of that they have chosen not to block temporary numbers for those who are more concerned.

Private chat apps are useless if noone knows how to use them. Signal tries to fix that, and I think they're doing a pretty good job even if it does have it's pitfalls.

[-] [email protected] -1 points 2 weeks ago

I think you missed the point there. The value for the NSA is in knowing which phone numbers communicate with other phone numbers which is precisely the metadata that Signal leaks. This allows you to build networks of users who are doing private communication. Next, you can cross reference the phone numbers with the data from Google, Meta, etc. and then if you see that one of them is a person of interest, then you immediately know the other people they talk to who are now also of interest.

The fact that people keep trying to downplay this is truly phenomenal to me. Once again, Signal is an app that uses a central server based in the US, that almost certainly shares data with the government. Anybody who minimally cares about their privacy should be concerned about this.

Signal is not an app that's private. Period. If you don't understand this then you don't understand what the term privacy means.

[-] [email protected] 0 points 2 weeks ago

There is a reason the Russian government allow the use of it and even let their military use it - and it is not due to security! They have a backdoor into the chats and UAE it actively for listening in on things and spreading propaganda and disinformation.

[-] [email protected] 0 points 2 weeks ago

Then why do the Ukrainians also use it?

[-] [email protected] 2 points 1 week ago

Nør for military communication. Just for public info

this post was submitted on 25 Aug 2024
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