Two questions.
My family insist on using Whatsapp for the family chats. I have to keep a copy on a device just so I can communicate with them. I do so under protest, as I was always told it isn't secure. My brother has just said
"oh Whatsapp is encrypted, it's perfectly secure".
First, is it actually as encrypted and safe as my brother claims? That would solve everything.
Second, if it isn't, where can I get some proof that we should switch to Telegram or whatever? Proof which doesn't make me look like a raving loony?
The contents of the chat messages are e2e encrypted, so meta can't see what you are sending.
But they can see all of the Meta data, ie how often you chat with someone, how often you send pictures/videos/voice messages, etc.
That is more than enough to know everything about you and your friends.
Even if we assume correct e2ee is used (which we have no way of knowing), Meta can still see what you are sending and receiving, because they control the endpoints. It's their app, after all.
They use the Signal protocol for e2ee.
Or so they claim. We can't really verify their implementation though.
Even if they do, you can't know whether they can access the encryption keys. It's all just layers of "but this, but that" and at the very bottom a layer of "trust me, bro".