MTProto is not end-to-end. MTProto is their obfuscated client-server transport encryption.

What the commenter above is referring to is Telegram defaulting to saving your messages on the server in plaintext. You can use a "secret chat" which enables end-to-end encryption, but that is separate from MTProto.

Your sentiment is correct though. Messages should not be visible in plaintext to the server.

it's still there, but hidden. You need to tap the username in the chat window, and then it'll be in that screen's triple-dot button menu.

Lacking end-to-end encryption does not mean it lacks any encryption at all, and that point seems to escape most people.

Not using end-to-end encryption is the equivalent of using best practice developed nearly 30 years ago [1] and saying "this is good enough". E2EE as a default has been taking off for about 10 years now [2], that Telegram is going into 2025 and still doesn't have this basic feature tells me they're not serious about security.

To take it to its logical conclusion you can argue that Signal is also “unencrypted” because it needs to be eventually in order for you to read a message. Ridiculous? Absolutely, but so is the oft-made opine that Telegram is unencrypted.

Ridiculous? Yes, you're missing the entire point of end-to-end encryption, which you immediately discredit any security Telegram wants to claim:

The difference is that Telegram stores a copy of your chats that they themselves can decrypt for operational reasons.

Telegram (and anyone who may have access to their infrastructure, via hack or purchase) has complete access to view your messages. This is what E2EE prevents. With Telegram, someone could have access to all your private messages and you would never know. With E2EE someone would need to compromise your personal device(s). One gives you zero options to protect yourself against the invasion of your privacy, the other lets you take steps to protect yourself.

the other hand, if you fill your Telegram hosted chats with a whole load of benign crap that nobody could possibly care about and actually use the “secret chat bullshit” for your spicier chats then you have plausible deniability baked right in.

The problem here is that you should not be mixing secure contexts with insecure ones, basic OPSEC. Signal completely mitigates this by making everything private by default. The end user does not need to "switch context" to be secure.

[1] Developed by Netscape, SSL was released in 1995 - https://en.wikipedia.org/wiki/Transport_Layer_Security#SSL_1.0,_2.0,_and_3.0

[2] Whatsapp gets E2EE in 2014, Signal (then known as TextSecure, was already using E2EE) - https://www.wired.com/2014/11/whatsapp-encrypted-messaging/

Signal is completely open source and auditable by anyone: https://github.com/signalapp

if you were to create your own clone, it would not interoperate with the real one.

if a messenger is truly 0 trust end to end encryption, it doesn't matter who owns the servers or the legal protections of data because they won't have any data anyway. that's why signal is so good, when they get subpoenaed the only information that they actually have is the last connection and message sent unix times or something. still secure regardless of being in the US and being run on centralized Amazon, google, and cloudflare servers.