If you have a Mac, and try to expand a password-protected PC Zip file (like an SDD or a Data Download), this Mac OS error message may be familiar (and annoying) to you:
Solution: we use the free Stuffit Expander software on our Macs, and it works like this:
Step 1: we see the "unable to expand..." error message, and head over to our Downloads folder to see the zip file we downloaded, but couldn't open.
Step 2: we right-click the zip file and choose "Open With Stuffit Expander" from the menu:
Step 3: we choose where we want the unzipped file to be saved.
Step 4: we are now prompted to enter the password, and the zip file opens.
In your university you might want to ask your IT department to say which software they recommend you download in order to open the file, however, Stuffit Expander from Smith Micro Software, Inc works really well on a Mac: https://apps.apple.com/us/app/stuffit-expander-16/id919269455
The people at Smith Micro Software, Inc https://www.stuffit.com say:
StuffIt Expander - Always Free!
Uncompress Zip archives, access StuffIt files, decompress tar, gzip and bzip archives, and more. Just drag, drop, and you're done! From BinHex to Zip, StuffIt to MIME, Expander accesses more formats, in less time, with zero hassles.
StuffIt Expander opens files created with WinZip®, 7zX, iShrink, SimplyRAR, Rarify, Rucksack (formerly iArchiver), BetterZip, RarMachine, GUI Tar, CleanArchiver, Springy, TarPit, RAR, Ez7z, Keka, and the compression utilities built into recent versions of Windows and macOS.
Q. Why won't the Mac's built-in 'Archive Utility' open password-protected Zip files?
A. Archive Utility isn't built to support password-protected zips.
Q. Are there alternatives to Stuffit Expander?
A. Yes, but we like this one.