E-Maculation

Does anyone know what encryption algorithm was used the Apple File Security? The only information I can find is that it was 128-bit encryption.

I have some old files that were encrypted on OS9 and I'm hoping to decrypt them using SheepShaver (I know the password), but they aren't recognized as being encrypted (no little yellow key in the corner of the icon) so I'm trying to learn more about the algorithm.

Are you sure the old files were copied and archived correctly? If they were copied to a Windows drive, they may have lost their resource forks, or at least their Type/Creator information.

Try creating an encrypted file and see if you can decrypt it. If so, then Jorpho's guess may be right. You might be able to use an old utility like FileBuddy to restore at least part of the lost resource fork.

Yes, they have been moved around a lot,

I was able to change the file attribute using instructions here