Can someone elaborate?
Can someone elaborate?
The second one is more difficult to evaluate. If you use the above mentioned "secret chat" feature, Telegram employs their own closed-source encryption scheme. That's usually an indicator to be cautious from the get-go. Since it's closed source, it can't really be trusted.
See [Wikipedia](https://en.wikipedia.org/wiki/Telegram_(software)#Security) for a timeline in regards to the security.
https://telegram.org/apps#source-code
Encryption for secret chats doesn't involve server, so technically it can be analyzed.
It's a pity Telegram decided to roll their own encryption scheme. I use Telegram a lot for daily business because it's superior desktop messenger product. I would gladly participate if somebody started a crowd-funding for Telegram's security and encryption audit.
Except if you are on desktop, you have no secret chats at all. And "desktop" includes GNU/Linux phones.