Your users seem to map to a set of permissions on a distibuted filesystem. Or a git repository.
This is my point: the idea is already implemented many times, but all the applications are too different from the field I want to work in. For example, kludging ssh and rsync to do instant messaging would solve the problem, but it's way too painful to deploy and maintain.
However, there's no description of your constraints or requirements. The words 'cryptography' or 'secure' do not appear in the question. Is the protocol destined to run on a local network with well-behaving agents?
Not on a local network, but through SSL, and node users will have to explicitly trust each other's public keys before the connection is possible, so the agents should be considered well-behaved. My major is far from cryptography, so I try to go for well-known cryptographic primitives instead of trying to roll my own.
