EDIT: Was under the impression Telegram served closed source clients. Turns out it does not. I stand corrected. OLD COMMENT: E2e using a client that is not op

EDIT: Was under the impression Telegram served closed source clients. Turns out it does not. I stand corrected. OLD COMMENT: E2e using a client that is not opensource (on a system that is not trusted) is not helping much. E2e where the server is not open source should be okay, because the server-end can only snoop on some meta data (how much, when, what IP, chunk sizes, etc.) but not the content.