A personal verification system comprising a user device which is adapted to generate a time varying, multi-character, nonpredictable code; a verification device; a mechanism for permitting the user to communicate the nonpredictable code generated by the user device at a given time to the verification...http://www.google.ca/patents/US4998279?utm_source=gb-gplus-sharePatent US4998279 - Method and apparatus for personal verification utilizing nonpredictable codes and biocharacteristics
