A method and apparatus is disclosed for approving a transaction request between an electronic transaction system and a portable electronic authorization device (PEAD) carried by a user using an electronic service authorization token. The method includes the steps of receiving at the PEAD first digital...http://www.google.es/patents/US6175922?utm_source=gb-gplus-sharePatente US6175922 - Electronic transaction systems and methods therefor
Electronic transaction systems and methods therefor
