Zigfrid – A Passive RFID Fuzzer

Zigfrid is the end result of my RFID tinkering. Since I will most definitely forget most things described here in the (very) near future, I share this for those few who might find it interesting. Please be warned: This is not a toy. It is completely unreliable, untested, malicious tool, which can and will cause elevators to stop or even shut down immediately, locks to jam, hackers get jailed, and other weird RFID phenomenons. Ok, you get the idea, lets move on. I guess I watched too many movies as a kid, and craved myself one of those futuristic-looking RFID “master keys” which opens all doors [with a few flashing leds for a more attractive effect], but as I grew older and learned there isn’t one I decided to try and build one for myself. I ended up with a tiny passive device consisting an ATtiny85 AVR, an antenna (coil), and 1 capacitor, with no need for external power. It’s so tiny, it can fit in a common chewing gum and glued next to any RF reader to fuzz away. My RFID adventures began with a cheap 20$ Handheld RFID Reader/Copier – a simple battery-powered device with 2 buttons controlling the read & write functions of it’s PCB, which uses an obscure chip labeled with the mysterious “F300 ET94 242+” which later found to be based on a more popular chip C8051F300. I hacked the PCB and connected it via it’s pins to my Arduino and later to my BusPirate in the hope of getting something on it’s serial line via the RX & TX pins – (and maybe later to alter it?) for vain – only a random bits every a few reads was letting me know I’m looking at it all wrong. And I was.”


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