To prevent piracy, audiovisual content is encrypted prior to transmission to consumers. A low-cost, high-security cryptographic rights module (such as a smartcard) enables devices such as players/displays to decode such content. Security-critical functions may be performed by the cryptographic module...http://www.google.com.tw/patents/US20060184807?utm_source=gb-gplus-share專利 US20060184807 - Specialized circuitry for cryptographic authentication and other purposes
