Is that true? I was hoping the link between the keys remained offline. The secrecy would only break if the attacker got the main key and the backup key.
Discussion
Ah, so the main key does a gift wrap to send the backup to a new pubkey, thats why the relationship between these two keys is private?
And thus even if the main key leaks, the backup keys are not known.
And if you need to access the backups just giftwrap them with yet another key so that they backup key never leaves the backup client.
Yep, the main key doesn't have any gift wrap to recover from.