The Fission platform does not currently need to know that two keys are associated with the same underlying user, and is focused on correct-by-construction access regulated by having access to keys. This means that it has a very weak concept of "identity", and is more focused on the delegation of capabilities between keys. One advantage is that aside from the originating key, there is always plausible deniability about "who" is associated with any particular key, regardless of the certificates it holds.