You don't have to believe in unbreakable encryption, just like you don't have to believe in unhackable cloud hosts. You just have to believe in hard enough to break and hard enough to hack. Then you're back to stuckagain's point, slightly revised: When A >> B and A >> C, A+B+C =~ A.

(Ah, that is, you have to believe that the encryption used in all legs of transit is hard enough to break.)