I think the general trust issues people have are - metadata / contact lists in the hand of Facebook - a proprietary binary that _claims_ to use said encryptio

I think the general trust issues people have are - metadata / contact lists in the hand of Facebook - a proprietary binary that _claims_ to use said encryption schemes Scenarios that you could come up with: The next version of WhatsApp sends unencrypted data again. WhatsApp encrypts for your recipient just fine, but also encrypts the same message for the great Facebook skeleton key. Basically trust is a bigger problem than you acknowledge here, I think. If you trust the encryption scheme, even the specific encryption implementation, then you still need to trust the (binary, closed) application. Ignoring the metadata issue completely for now.