>Maybe the client itself is generating the keypair. In this case, the only issue I can see is the following: when the user wants to communicate with a friend, h

>Maybe the client itself is generating the keypair. In this case, the only issue I can see is the following: when the user wants to communicate with a friend, how can they be sure that the profile they are sending messages to (as displayed by their user interface and communicated by Facebook or Whatsapp or the friend's server) actually do belong to their friend? That's exactly the point though, how can they be sure in the event that their client (on the author's side) is a trojan? If the "author" client is deliberately compromised, there is no longer any reasonable means of ensuring that the public key the author uses to encrypt the messages is actually equal to the public key the recipient published. Of course, this point is very much riddled with paranoia: it is exceedingly unlikely that the WhatsApp client deliberately contains such a trojan, especially since there are much easier ways of gaining access to user's messages (such as compromising their firmware with some form of rootkit, possibly installed via the baseband, and then simply sending copies of the local message cache to the NSA).