“NFCopy85 is a 10 dollars device to make replay attacks against NFC payment systems. Tested it against Samsung Pay, Google Pay and Wells Fargo Wallet NFC tokens in US.
Hardware
NFCopy85 is a small version of NFCopy. This tiny version is a combination of ATtiny85 and a small PN532 board. Adding a 3.7 LiPo battery and a power booster to increase the 3.7V to 5V for the PN532 board. Also I added a LED with a resistor just for debugging and to show activity.
Software
For the software side, I modified the Adafruit PN532 library. By default, the library is too big for the ATtiny85 and some functions had to be edited for a good communication between the ATtiny85 and PN532 board. To establish the communication, I decided to use SPI. So I deleted all the parts in the library that were not needed for the SPI communication.”