I'm considering enabling Archive Key Password in my CrashPlan account. I'd like to understand how secure this feature is.
CrashPlan documentation for Archive Key Password says (emphasis added):
Instead of securing the encryption key with your account password, you are choosing to secure the key with an additional password, called an archive key password. Only the secured encryption key is stored on CrashPlan servers.
The key is encrypted with your archive key password and stored on the master server
If you lose or forget your archive key password: [...]
Without an archive question enabled: There is no way to reset your archive key password if it is lost or forgotten. You will be unable to restore files and you must start over with a new account.
It then describes the Archive Question feature:
In the event that your archive key password is lost or forgotten, and you have this feature enabled, you can answer your archive question.
- If the salted and hashed version of the stored answer matches the salted and hashed version of the supplied answer, you can enter a new archive key password.
- The secure key stored on the master server is updated with the new archive key password.
Since the secured key is encrypted using the old archive key password, I would expect that updating the secured key requires it.
However, the old archive key password isn't available in this scenario (lost or forgotten), and is supposedly not stored on the servers.
How then can the secured key be updated with the new archive key password in this scenario?