Conditional access system

Abstract

A conditional access system in which entitlement control messages (ECMs) containing the encryption keys used to encrypt a program transmission, are sent to a set-top box over a secure communications channel separate from the channel used for transmission of the encrypted program.

1 . An apparatus comprising:
 a transmitter configured to:
 transmit control messages associated with decoding a scrambled broadcast stream separately from the scrambled broadcast stream if access is authorized; and 
 not transmit the control messages if access is not authorized, 
   wherein access is authorized when a subscription exists between a user and a service provider in a home network region.   
   
   
       2 . The apparatus of  claim 1 , wherein the transmitter is associated with a second service provider different from the service provider in the home network region. 
   
   
       3 . The apparatus of  claim 2 , wherein the second service provider is associated with a roaming network region. 
   
   
       4 . The apparatus of  claim 1 , further comprising a subscription authorization module configured to check whether the subscription between the user and the service provider exists. 
   
   
       5 . The apparatus of  claim 1 , wherein the subscription includes roaming privileges. 
   
   
       6 . The apparatus of  claim 1 , wherein the transmitter is configured to transmit the control messages in response to receiving a request for the control messages. 
   
   
       7 . The apparatus of  claim 1 , wherein the transmitter is configured to transmit the control messages through a virtual private network. 
   
   
       8 . The apparatus of  claim 1 , wherein the transmitter is further configured to modify one or more control words in the control messages at a predetermined interval. 
   
   
       9 . A method comprising:
 determining whether a subscription exists between a user and a service provider in a home network region; and   in response to determining that the subscription exists, transmitting control messages associated with decoding a scrambled broadcast stream separately from the scrambled broadcast stream.   
   
   
       10 . The method of  claim 9 , wherein the control messages are transmitted in a roaming network region different from the home network region. 
   
   
       11 . The method of  claim 10 , wherein transmitting the control message is performed over a first channel different from a second channel over which the scrambled broadcast stream is transmitted. 
   
   
       12 . The method of  claim 9 , wherein determining whether the subscription exists between the user and the service provider in the home network region includes determining whether the subscription includes roaming privileges. 
   
   
       13 . The method of  claim 9 , further comprising receiving a request for the control messages and wherein determining whether a subscription exists is performed in response to receiving the request. 
   
   
       14 . The method of  claim 9 , further comprising encrypting the control messages for transmission. 
   
   
       15 . The method of  claim 9 , wherein the control messages are transmitted from a second service provider associated with a roaming network region different from the service provider in the home network region. 
   
   
       16 . The method of  claim 15 , further comprising revoking subscription rights in the home network region upon transmitting the control messages in the roaming network region. 
   
   
       17 . The method of  claim 9 , wherein the scrambled broadcast stream is transmitted over a first channel and the control messages are transmitted over a second channel different from the first channel. 
   
   
       18 . The method of  claim 17 , wherein the second channel is a virtual private network. 
   
   
       19 . The method of  claim 9 , further comprising modifying one or more control words in the control messages is changed at predetermined intervals. 
   
   
       20 . The method of  claim 9 , wherein the control messages further include access criteria for accessing a service through which the scrambled broadcast stream is transmitted.