What does that get you, though? The formula for a valid card number (Mod 10) is public. If Home Depot uses a 1-way hash for the card number, and ONLY uses the c

What does that get you, though? The formula for a valid card number (Mod 10) is public. If Home Depot uses a 1-way hash for the card number, and ONLY uses the card number, you gain nothing - you still need the expiration date/CVV/Name to do much else.