A method of determining a counterfeit security document which includes a number of coded data portions indicative of an identity of the security document; and at least part of a digital signature of at least part of the identity. The method includes using a sensing device to sense at least one coded...http://www.google.ca/patents/US7506168?utm_source=gb-gplus-sharePatent US7506168 - Method for identifying a counterfeit security document
