More information on PAR or Parchive files can be found at Wikipedia, of course:http://en.wikipedia.org/wiki/Parchive
Fix "Password required" Error When Using Unrar in Ubuntu
If you've tried to use the built-in "Extract Here" functionality in Ubuntu'sFile Rollerto extract either a single or a multi-part zip or rar file and ended up with a "Password required" error, then you might just assume the files are password protected when in fact they are not.
