Does this mean user1 to user2 or user1 to server and user2 to server. Both of them are end to end when you define end as client(user1, user2) or server. Again, it was proven several times that real user to user encryption is very rare, I am only aware of SILC doing that. I do not know enough about WhatsApp to believe it is user to user and I do not trust Facebook with anything. You can prove me wrong though.
user1 -- server -- user2
Does this mean user1 to user2 or user1 to server and user2 to server. Both of them are end to end when you define end as client(user1, user2) or server. Again, it was proven several times that real user to user encryption is very rare, I am only aware of SILC doing that. I do not know enough about WhatsApp to believe it is user to user and I do not trust Facebook with anything. You can prove me wrong though.