"Now, normally the two sides would compute the shared key as (g^a)^b mod p and (g^b)^a mod p. Instead, the original version of MTProto computed it as
(g^a)^b mod p XOR nonce
where nonce was an arbitrary, supposedly random value sent by the server along with the peer’s public contribution.
This was a completely non-standard and useless addition, and all it did was let the server perform an undetected Person-in-the-Middle attack."
https://buttondown.email/cryptography-dispatches/archive/cry...
That's a really long way to say e2ee requires special steps: Deliberately selecting "new secret chat".
If there's ANY barriers to e2ee such as this one, then non-e2ee ends up being used.
That's just how it is, how non-technical people are, and why we should steer everybody away from Telegram.
When creating a 1 to 1 chat, it's one of the default buttons. In Android, you click a {pencil} icon, then "new chat" (encrypted in transit and at rest like your bank website) or "new secret chat" (end to end encrypted)
> - It is not an open protocol.
The protocol is fully open source and audited. https://telegram.org/apps scroll down to source code.
> - It is not open source.
As above https://telegram.org/apps . The client apps are fully open source and reproducible.
> - It has a history of extremely poor cryptography practices.
People pointed out the security issues in MTProto v1, and they were all addressed in MTProto v2 over 3 years ago.
You may be recalling some FUD spread by the author of what eventually became Signal, but none of what you said above is factual.