> Some might argue whatsapp or signal or Telegram E2E is exactly that. I talk about the email.
These three are not equivalent.
Signal is the gold standard for secure, end-to-end encrypted messaging. The client is open-source, and (at least on Android) builds are reproducible. It's possible to audit the code and confirm that Signal isn't intercepting the messages via side-channel and sending them to Signal's servers, encrypted with a different key. It also notifies you whenever a users's public key has changed (ie, when they switch to a different phone), which protects against someone hijacking your phone number using the telecom system.
WhatsApp does encrypt messages with per-user keys, but it's not end-to-end in the sense that Facebook still manages the keys and could provide you with a compromised key. Facebook also produces the only client, which means that it could easily eavesdrop messages and send them to Facebook's servers via a side-channel. Until recently, WhatsApp also didn't notify you when a user's key had changed. This wasn't a "backdoor" as the Guardian sensationally reported it, but it is a security liability for users looking for secure end-to-end encryption.
Telegram is completely insecure. For starters, group messages on Telegram are sent... in plain text. No encryption whatsoever.
These three are not equivalent.
Signal is the gold standard for secure, end-to-end encrypted messaging. The client is open-source, and (at least on Android) builds are reproducible. It's possible to audit the code and confirm that Signal isn't intercepting the messages via side-channel and sending them to Signal's servers, encrypted with a different key. It also notifies you whenever a users's public key has changed (ie, when they switch to a different phone), which protects against someone hijacking your phone number using the telecom system.
WhatsApp does encrypt messages with per-user keys, but it's not end-to-end in the sense that Facebook still manages the keys and could provide you with a compromised key. Facebook also produces the only client, which means that it could easily eavesdrop messages and send them to Facebook's servers via a side-channel. Until recently, WhatsApp also didn't notify you when a user's key had changed. This wasn't a "backdoor" as the Guardian sensationally reported it, but it is a security liability for users looking for secure end-to-end encryption.
Telegram is completely insecure. For starters, group messages on Telegram are sent... in plain text. No encryption whatsoever.