A method and apparatus for determining the distance between transitions from a first logical state to a second logical state stored on a medium (i.e., a document). This determination is used to precisely characterize the information pattern in order to authenticate the information and the medium on which...http://www.google.fr/patents/US6260146?utm_source=gb-gplus-shareBrevet US6260146 - Method and apparatus for securing and authenticating encoded data and documents containing such data
Method and apparatus for securing and authenticating encoded data and ...
