Patent ID: 8635455

Claim:
A replaceable cartridge comprising a consumable colorant for a printer, said cartridge comprising a device for encrypted communication with the printer, the device comprising: a first non-volatile memory; a base key stored in the first non-volatile memory; and, a one-way function for application to the base key; wherein the device is configured to: retrieve the base key from the first non-volatile memory; generate a first variant key using the one-way function, the base key and information from the printer; store the first variant key in the first non-volatile memory; generate a digital signature using the first variant key; and authenticate communications between the device and the printer using the digital signature, and wherein the device is configured to limit a number of times the base key is retrieved from the first non-volatile memory in a given period of time without limiting a number of times the variant key is used during the given period of time.