Why exactly do you assume that a credit card reader is a "closed box that is obviously provided by a bank"? I've implemented point-of-sale systems before, and

Why exactly do you assume that a credit card reader is a "closed box that is obviously provided by a bank"? I've implemented point-of-sale systems before, and lemme tell you, there's nothing magical about a magstripe reader, a microcontroller, and a bit of firmware. Think for a second about recent credit-card purchases you've made. If your habits are anything like mine, aside from gas stations (where the reader is usually integrated into the pump), most card "swipes" happen through either a peripheral device connected to a generic PC, or a compact card reader with little more than a keypad and phone jack, with no visible branding, certification, or tamper-resistant seals in sight.