Curious how sensitive the SKIM reader in the van is. This will probably work, but I don't know how much foil you'd need to guarantee it. You might be surprised how well some RFID transponders work despite aluminum foil:
I figured a few bucks was worth it to have a more definite answer.
Aluminum Foil Does Not Stop RFID
www.omniscienceisbliss.org
I figured a few bucks was worth it to have a more definite answer.
Or you could save the trip to the store by completely covering the grey plastic part of the key with a sheet of cooking tin foil - just make sure it's completely wrapped with no gaps and only the metal key 'blade' is exposed...