Just as the topic says. There should be an easy option to destructively reset and rekey a synced graph, in the event that the encryption key has been lost but at least one copy of the graph is still accessible somewhere - this doesn’t require any kind of key recovery mechanism, just overwriting of the synced data with a new sync encrypted with the new key. Maybe require reentering of the user’s login password to confirm, but as easy as it is to lose the key, it should be no more painful than that to fix it.