The fact that the files are encrypted in the first place appears to be a
bug/feature of Vista's built-in extractor when dealing with files compressed
in OS X with OS X's built-in GUI compression utility.
This issue can be easily recreated. Take any file on a Mac running OS X
10.4.x or higher (I've been unable to test this with earlier versions of OS
X) and Ctrl-click/Right-Click on it and choose 'Compress "Filename".
Then move that file to a PC running Windows Vista with all current updates
and no additional extraction software (i.e. no WinZip or WinRAR).
In Vista, right-click on the file and choose 'Extract All...' Vista extracts
the file(s) to a folder with the same name as the compressed file, the files
contained in the folder have green filenames indicating they are encrypted.
Vista's extractor encrypts the files during the extraction process.
Examining the properties of the file shows me that the account associated
with the encryption is vista_user(vista_user@vista_machine_name).
It's easy enough to remove the encryption by right clicking and modifying
the attributes. This only occurs with files compressed in OS X and extracted
with Vista's built-in extractor. This does not occur if WinZip or WinRAR is
used to extract the files on the Vista machine or with XP's built-in
extractor. This also does not occur the OS X command-line zip utility is
used to compress the file(s). The command line-utility does not include the
HFS metadata for the compressed files that the GUI compression utility does
include. It seems that if Vista's extractor sees that data it decides that
it needs to encrypt the files it's extracting.
I'd really like to understand why the Vista extractor is adding encryption
to the OS X compressed files when it extracts them. It's obviously not a
major problem, but the first time a Vista user extracts a Mac compressed file
in this manner on Vista they're prompted to back up encryption keys so they
don't lose access to their files. Vista's dialogue boxes do not specify
which files, so for less savvy users, these messages can be extremely
alarming.
Can anyone please explain why Vista's extractor is behaving in this manner
with files compressed on a Mac? I've literally searched all over the
Internet trying to understand this. Fortunately, I have a workaround with OS
X's command line utility, but I'd really like to understand why Vista is
doing this in the first place. Any information would be greatly appreciated.