Method and apparatus for secure transmissions. Each user is provided a registration key. A long-time updated broadcast key is encrypted using the registration key and provided periodically to a user. A short-time updated key is encrypted using the broadcast key. The short-time key is available with each...http://www.google.com.tw/patents/US7352868?utm_source=gb-gplus-share專利 US7352868 - Method and apparatus for security in a data processing system
