Comment 1 for bug 1413044

Ouch, that's pretty bad. I suppose there could be two parts to fixing this:
1-provide some kind of option to allow the user to keep the original .xbcrypt files on decrypt but that will also mean making --copyback aware so it doesn't copy the .xbcrypt files back on restore.
2-bump the xbcrypt chunk header version and add some kind of marker at the beginning of the encrypted chunk that can be validated on decryption, but this would effectively weaken the encryption and would not solve the issue of older/existing backups.