A HackRF One software-defined radio (SDR) will let you zap out and receive radio signals all across the spectrum. Add a PortaPack, and you can do that on the go — for diagnostic tests and white hat hacking only, of course. It’s a handy setup that you can use for all sorts of things, specifically radio things. But, Salvador Mendoza has come up with another interesting use for his PortaPack as a mag stripe reader and “replayer.”
The magnetic stripe on credit cards stores data as bits, but is read as an analog audio track like a short cassette tape. When the card is swiped, a magnetic head in the reader “listens” to the data to determine your credit card information. So, Mendoza’s first step was to grab a magnetic card reader. That outputs the magnetic stripe’s audio tracks, but Mendoza still needed a way to get it to his PortaPack for later use.
For that, he used a cheap off-the-shelf FM transmitter. That creates a radio station that the HackRF One can tune into to pick up and record the mag stripe tracks. If Mendoza were a bad person, he could just go around swiping people’s cards to collect recordings, but he obviously won’t do that. With a mag stripe recording on hand as a WAV file, he can then replay it with a simple magnetic coil connected to the HackRF One’s audio output jack. The coil just needs to be positioned near a credit card reader’s magnetic head, and Mendoza can “swipe” any credit card he has recorded.