A transaction system is disclosed wherein, when a transaction, document or thing needs to be authenticated, information associated with one or more of the parties involved is coded together to produce a joint code. This joint code is then utilized to code information relevant to the transaction, document...http://www.google.com.hk/patents/US5555303?utm_source=gb-gplus-share專利 US5555303 - Secure transaction system and method utilized therein
