Note for ResKey owners who also use Authorize dot net, in addition to not needing the CVC code, I leaned today that it also doesn't need the card type (MC/VISA/AMEX/DISC) that ResKey asks for.
I had somebody give me their card info. I didn't get the card type and didn't want to contact the guest again, so I ran the card with it set to VISA. It went fine but when I got the Authorize confirmation number, it shows it was actually a Mastercard. Authorize doesn't care.
Apparently all that's really needed is the card number, exp. date, and zip code..