I can't imagine how to solve the problem in an acceptable manner. Without something like certificates and encryption, some concept of identity, you're just not going to get anywhere, and I'm about fifteen miles into the "unacceptable" territory with that suggestion ("hey, guys, let's just rewrite the entire infrastructure from the very bottom!"). Your primitives are broken, any system built with them will be broken, and it's going to be more years before people are ready to even think about that.