According to the current version of the iPhone app, yes, my group chats are E2E encrypted. I believe the mechanism is to use a generic / per message key to enc

According to the current version of the iPhone app, yes, my group chats are E2E encrypted. I believe the mechanism is to use a generic / per message key to encrypt each individual message, and then use each recipient's public key to encrypt the encryption key before sending that (along with a link to the cipher text) to each end user. This is also why sending a video the first time takes forever (encrypt, upload, encrypt key, send key, send link), while forwarding it to another person (encrypt key, send key, send link) does not.