Validation of printer cartridges using a unique identifier from an RFID tag, a serial number or identifier from a cartridge, and a seed to generate a reproducible key are described. The key is written to non-volatile memory of the RFID tag. The parameters for generation of the key are retrieved when the cartridge is asked to print in a printer, and a second key is generated, and the keys are compared. If the keys match, the cartridge is validated and printing continues.