So... How can we access the private certificates on our devices? Without direct access to those this has no partial privacy safeguard. Furthermore, Facebook is

So... How can we access the private certificates on our devices? Without direct access to those this has no partial privacy safeguard. Furthermore, Facebook issued the private keys to us for every contact, therefore they have the private and public key to every contact pair we've ever made.. and can therefore decrypt every message we've ever made. What proof do we have that this is not the case?