RFID hacking preamble: a new peak detection for the proxmark3

Introduction Building upon the IIR filter from the last post we’re now going to improve the edge/peak detection fpga module. Why The current algorithm is really simple, maybe too simple: whenever the ADC value is above (resp. below) a hardcoded value, it outputs 1 (resp. 0) with hysteresis. There are two problems with that: well first, the hardcoded values… For some reason no one has really complained about it so far (?

RFID hacking preamble: designing an FPGA IIR filter for the proxmark3

Introduction At work, they recently replaced the coffee vending machine for a new one. One detail quickly piqued my interest though: you could now ask the front desk for an RFID token, pay your coffee with it instead of regular coins, and also deposit cash into the token at the vending machine. How does it work? Which RFID IC does it use? Can we play with it? The next few posts will narrate this journey.