from
http://club.cdfreaks.com/showpost.php?p=671606&postcount=4
"There are many reasons to archive the CSS keys.
Depending on the situation (region mismatch, brute force attack required, amount of vulnerable blocks) calculating the CSS key can take quite long.
Keeping this key in an archive will speed up the process in the future.
Some drives (RICOH, Philips) can reveal the correct title keys due to a firmware bug even on region mismatch, but it is required to open and close the drive tray after key exchange.
I believe AnyDVD is the only Software, that does use the "open/close tray trick" to get correct title keys from these drives, even if there are not enough vulnerable blocks available for a brute force attack.
Opening / closing the tray is very annoying, but because of the CSS Key archive this has to be done only once. The next time you insert the same DVD, the keys will be taken from the archive.
Sometimes AnyDVD is not able to get the key with a brute force attack, and it will "guess" the correct key (usually correctly). You can change/verify the guessed keys in the archive. If you change the "Substitute" flag from yes to no, AnyDVD will take the "guessed" key for granted and will no longer display a warning message.
If you messed up the archive, AnyDVD can delete single keys, all keys for a title or the whole archive if you wish.
You can even import/export/edit keys. e.g., you have a second computer with a drive, which can reveal the keys without brute force attack. You can transfer the keys from one computer to another.
Last but not least, you can compare / exchange keys with other software, e.g. DVDDecrypter.
The key archive is kept in the registry, together with a MD5 checksum to identify the title the keys belong to."
-- James