Sorry, but you seem to have not understood me at all.

And he is not alone.

You should perhaps start by telling us which protocol you are taling about. A client asking for a hash sounds like some peer-to-peer file sharing protocol, but rsync also uses a kind of hash. If it is not a common protocol, like HTTP, FTP, rsync, link to the protocol spec.

Then, don't invent new terminology, use the one from the protocol spec.

Alexander