According to [RFC](http://tools.ietf.org/html/rfc4287#section-4.2.6): 

    When an Atom Document is relocated, migrated, syndicated,
    republished, exported, or imported, the content of its atom:id
    element MUST NOT change.  Put another way, an atom:id element
    pertains to all instantiations of a particular Atom entry or feed;
    revisions retain the same content in their atom:id elements.  It is
    suggested that the atom:id element be stored along with the
    associated resource.

So, relying on `SecureRandom` is incorrect. I'll fix that. But we do need a scheme for ensuring the uniqueness, unless we add UUID fields for the builds and repos.