yan 🐇random n00by question: say that i have a key card and already determined that it's not NFC. what's the easiest way to figure out what protocol it is using? assuming it is passive RFID, is there a DIY way to read it (like with an SDR)?
filsy@bcrypt is it contactless? assuming yes then it'll most likely be a 125kHz one.
To read you can use this https://www.seeedstudio.com/125Khz-RFID-module-UART-p-171.html and an arduino.
Alternatively a proxmark will do the job.
Other tools are available from chinese sites https://www.aliexpress.com/item/125khz-RFID-Copier-Duplicator-Cloner-EM-reader-writer-3PCS-EM4305-writable-keyfob/32614618462.html