1. A device comprising: means for identifying a group of computers to which a subtree of a hierarchical namespace used to store files is to be delegated; means for generating a delegation certificate for the subtree, wherein the delegation certificate comprises: a first digitally signed certificate identifying another group of computers responsible for managing a namespace root of the subtree; and a second digitally signed certificate allowing authorization of the group of computers to manage the subtree to be traced to the other group of computers responsible for managing the namespace root; means for digitally signing the delegation certificate; and means for issuing the delegation certificate to the group of computers.