An electronic transaction system operable on an all-purpose communication system, the transaction system allowing the use of an electronic check on which drawees' digital signatures are added using a public key cryptosystem to prevent the illegal alteration or raising of the checks. The electronic checks...http://www.google.com.tw/patents/US6411942?utm_source=gb-gplus-share專利 US6411942 - Electronic transaction system and systems for issuing and examining electronic check
