Here is my talk I did last year on hacking Hotel Room Keys and Point of Sale Systems.
Take a look at weaknesses in Point of sale systems and the foundation of hotel key data and the Property management systems that manage the keys. Using a modified MST injection method Weston will demonstrate several attacks on POS and Hotel keys including brute forcing other guest’s keys from your card information as a start point. And methods of injecting keystrokes into POS systems just as if you had a keyboard plugged into the system. This includes injecting keystrokes to open cash drawer and abusing Magstripe based rewards programs that are used a variety of environments from retail down to rewards programs in Slot Machines.
Let me know if you have any questions