Patent ID: 7500268

Claim:
A method of using a mobile device to authenticate a print medium before completing printing onto the print medium, the mobile device including processing means, a printhead, a print path extending past the printhead and a sensor adjacent the print path, the print medium comprising a substrate, the method comprising the steps of: using the sensor to sense coded data provided on a surface of the substrate whilst the print medium is moving along the print path, the coded data having a plurality of coded data portions, each of the plurality of coded data portions, encoding: the identity; and, at least a signature fragment; which encodes a signature fragment identity; using the processing means to interpret the plurality of coded data portions and determine the plurality of signature fragments in order to determine the signature fragment identity of each determined signature fragment and subsequently determining, using the determined signatur efragment ideitites, the determined signature to authenticate the print medium; and in the event the authentication step is successful, using the printhead to print onto the print medium.