Security device and method for conditional access system and set-top-box

A security apparatus and method for (Conditional Access System) and CAS discloses a STB (Set-Top-Box). Security apparatus using the CW encrypted content, the more receiving receives the ECM (Entitlement Control Message) from the STB from the CA agent (Conditional Access agent) and the STB to obtain a (Control Word) CW containing said ECM and a CA descrambler (descrambler) for decoding. CAS (Conditional Access System), STB (Set-Top-Box), ECM (Entitlement Control Message), EMM (Entitlement Management Message), (Control Word) CW