"bioctl -P" is to change passphrase without wiping the encrypted partition's contents. How do you generate a new keydisk without wiping the same?

[Tinker]

"bioctl -P" is to change passphrase without wiping the encrypted 
partition's contents. How do you generate a new keydisk without wiping 
the same?

I.e. I have an encrypted partition /dev/sd0a which is encrypted using 
the keydisk /dev/sd1a . Say /dev/sd1a's contents were compromised. How 
do you generate a new one without needing to wipe /dev/sd0a .

I.e. exactly the same as "-P" but for the keydisk usecase.

(Of course the old keydisk/password is needed at replacement time.)

Thanks,
Tinker