A printer system includes a printer and a printing consumable detachably mounted on the printer. The printer has a first integrated circuit which generates a random number, reference information using the random number and a secret key. The printing consumable has a second integrated circuit which generates validation information using the random number and the secret key received from the first integrated circuit. The printer also has processing circuitry configured for receiving the reference information from the first integrated circuit; receiving the validation information from the second integrated circuit; and comparing the reference information and validation information so as to validate the printing consumable device for use with the printer.