A METHOD OF CLONE BOX CHECKING OF CAS IMAGE BASED ON DOWNLOADABLE CONDITIONAL ACCESS SYSTEM

PURPOSE: A method for determining the duplication of a CAS image in a DCAS is provided for a DCAS host to transfer stored clone information to a DCAS server, compare synchronized clone information, and determine whether the CAS image is duplicated. CONSTITUTION: A DCAS(Downloadable Conditional Access System) host(300) receives the version information of a CAS(Conditional Access System) image from a DCAS server(200). The DCAS host compares the version information of the received CAS image and the version information of a CAS image stored in the DCAS host. The DCAS host loads stored clone information and transmits the clone information to the DCAS server. The DCAS host compares clone information received from the DCAS server and the clone information stored in the DCAS server and returns comparison result information. The DCAS host performs a security policy corresponding to the result information.