reversing a printer cartridge chip:
How does a printer know when the cartridge is empty? Instead of using a sensor, the toner or ink level information is simply stored in memory and updated after each print. This technique also applies to my old laser-jet printer. I was able to identify the chip on the toner cartridge as a 1-Wire EEPROM with some authentication features. We will see how and what the 1-Wire protocol is. I also re-implemented this chip and was able to pass authentication thanks to a secret key I dumped from another chip, allowing me to fool the printer in thinking the toner cartridge is never empty.