Several months ago, we got a new coffee dispenser machine at work that waits for an NFC tag before pouring a hot beverage. Everyone has a tag, and with this tag, we get free drinks. At first I wanted to clone it, so I played with this nice and inexpensive NFC reader (based on the well supported PN532 chip), but found out my tag, which is a Mifare Classic 1K from NXP (MF1 IC S50), was not vulnerable anymore to the current available cloning technique. Since I had never played with NFC before, I still wanted to get some data and see what I could do with it. So I switched to a new goal which was sniffing an NFC transaction between the coffee dispenser machine and my tag.