> It uses a homebrew encryption scheme

Please stop with that. At some point every encryption scheme was "homebrew" (or rather, new). MTProto 1.0 had flaws, which were addressed in 2.0. The latter has been independently formally verified to be secure[0].

> Telegram is the least secure.

Against who? What is your threat model? Such absolutist blanket statements are useless by design.

> of all the major messengers

Which are Messenger, Whatsapp, and SMS/RCS around here. Signal shows up from time to time, and Matrix doesn't even register above statistical noise so I won't count them as "major" (Signal, being, in a stroke of optimism, at best a challenger)

Of these, SMS/RCS is a total clusterfuck, and the remainder is owned by Meta. Yes, Meta is high on my list of adversaries, and given their track record should probably be for anyone out there caring about their privacy. No, WhatsApp's E2E is not to be trusted[1][2].

So is Telegram the least secure of major messengers? definitely not.

Is Telegram perfect security, certainly not either, because that doesn't exist[6], but their E2E is solid, even without E2E, extra steps are taken to thwart certain adversaries[3][4], they have reproducible builds for their client binary builds[5], and as can be observed so far their actions are veering on the complete opposite side of Meta's.

Is Telegram an opportunity to convince non-{privacy,security}-minded random joes and janes to jump out of a bunch of terrible chat platform for a better (or less worse if you want) chat platform? I'd say probably. I mean, it really really looks like they're trying hard to get the job done.

[0]: https://github.com/miculan/telegram-mtproto2-verification

[1]: https://twitter.com/Shiftreduce/status/1347546599384346624

[2]: Meta controls the Es in this "E2E", and I won't trust that, ever.

[3]: https://telegram.org/faq#q-do-you-process-data-requests

[4]: https://security.stackexchange.com/questions/238562/how-does...

[5]: https://core.telegram.org/reproducible-builds

[6]: https://dl.acm.org/doi/10.1145/358198.358210

A non-standardized, homebrew encryption scheme does not necessarily have to be worse than a standardized algorithm - even though it often is. But if implemented correctly and by someone who knows what they are doing, I'd trust a homebrew algo more than one which has been approved by the west's codebreakers for general use.

You can enable e2e chats. But you lose cloud sync.

> Also, being based in the UAE doesn't inspire confidence on the privacy and security front...

Well the 5 eyes do not inspire confidence either, and that's where whatsapp is based.

And Apple has plans to automatically inform law enforcement from device scans. At least telegram client is open source so that is unlikely to happen on the client side directly.

> the number of people that can see the chats between me and my mother has just gone from two (me and her) to 500 (all the engineers on the telegram team).

And everyone from all companies to which Telegram will sell the data once they figure that there is a good money to be made from it.

If they have the plain text data they can do whatever they want with it.