When you swipe your bank card at a retailer, the cost has to pass through a financial institution like a bank, which confirms the transaction, debits the cardholder’s account, and relays the cost to the retailer to finish the sale. This could be costly — banks charge a payment for the service — and insecure for customers, as current hacks on Target’s point-of-sale techniques have proven. There is also the potential for bank card fraud, which prices merchants in the us hundreds of millions of dollars a year.