In a system for performing an action regarding an account in response to an electronic communication received from a sender by a receiver, wherein the electronic communication includes sender identity information associated with the account and a digital signature derived using a private key of a public-private...http://www.google.com.tw/patents/US6820199?utm_source=gb-gplus-share專利 US6820199 - Sending electronic transaction message, digital signature derived therefrom, and sender identity information in AADS system
