Patent ID: 8020002

Claim:
A method of authenticating a print medium to allow printing thereon by a printhead of a mobile device, the method comprising using the mobile device to: sense coded data on the print medium to determine an identity of the print medium, a part of a digital signature of the identity of a plurality of parts of the digital signature and a part identifier of a plurality of part identifiers which each identify a respective signature part encoded by the coded data; determine, using the determined signature part and respective part identifier, the entire digital signature; generate, using the determined signature and a public key stored in the mobile device, a generated identity; and compare the determined and generated identities to determine if the print medium is authentic, wherein the print medium includes an orientation indicator, the method comprising using the mobile device to: sense the orientation indicator prior to sensing the coded data; and prevent printing in the event the print medium is inserted incorrectly in a print path of the mobile device.