Note I'm talking "clone of the Arduino", not "Arduino-based clone of the YubiKey". My point was that if you don't need protection against key extraction, you ca

Note I'm talking "clone of the Arduino", not "Arduino-based clone of the YubiKey". My point was that if you don't need protection against key extraction, you can just get an ultra-cheap microcontroler and write code to do the crypto operations on them. This thread talks about sub-1$ Arduinos: https://old.reddit.com/r/arduino/comments/dixa9x/awesome_sub_1delivered_arduino_ide_compatible/ https://old.reddit.com/r/arduino/comments/dixa9x/awesome_sub... I can't speak to the quality of those, but my friend got some sub-1$ Arduionos in the past (not sure which) and said they worked.