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Conditional access system

Conditional access system description/claims

This application is a continuation of co-pending U.S. application Ser. No. 09/893,523, entitled “CONDITIONAL ACCESS SYSTEM,” filed Jun. 29, 2001, the content of which is incorporated herein by reference in its entirety.

The present invention relates generally to the field of broadcast and reception, particularly but not exclusively to a conditional access system in a digital satellite television system. More particularly, aspects of the present invention relate to the transfer of entitlement control messages in a channel separate from the broadcast channel.

Conditional access systems are well known and widely used in conjunction with currently available pay television systems. At present, such systems are based on the transmission of programmes scrambled with control words which are received by subscribers having a set-top box and a smart card for each subscription package. The smart card for a subscription package from a particular service provider allows the scrambled programmes within the package to be descrambled and viewed. The broadcast stream further contains entitlement management messages and entitlement control messages, which are necessary for the smart card to descramble the broadcast. The terms scrambled and encrypted are used interchangeably in this application. WO 98/43426 discloses a digital satellite television system in which the entitlement management messages are transmissible to the set-top box via a modem based back channel, rather than via the broadcast channel. This is done to speed up viewer authorisation in viewing systems such as pay-per-view, since there is a certain time delay before the subscriber authorisation system (SAS) can include the proper entitlement management messages in the broadcast stream. However, the entitlement control messages which contain the control word in an encrypted format are sent via the broadcast channel. The control word is decrypted at the set-top box by means of a smart card.

According to the present invention, there is provided a conditional access system comprising a first transmitter for transmitting a scrambled broadcast stream and a second transmitter for transmitting a plurality of control messages separate from the broadcast stream, said control messages including information for descrambling the broadcast stream.

The control messages may be sufficient on their own to allow the broadcast stream to be descrambled.

By separating the broadcast and control message channels, the need for a smart card can be obviated, since the information for descrambling the broadcast stream can be incorporated in said control messages without being encrypted. While the control messages can then be encrypted for transmission over a secure link, for example over a virtual private network using a protocol such as the https secure sockets protocol, the unencrypted control words are recovered at the receiver side of the secure link, so that the decoder does not require a smart card for decryption. Advantageously, since the decoder is thereby provided with ready to use decryption keys, the decoder can be made to be independent of any specialised conditional access system.

Additional security can be provided by encrypting the information for descrambling the broadcast stream into the control messages, which gives rise to the need for a smart card, such as a virtual or software smart card, at the decoder.

According to the invention, there is further provided a conditional access system comprising a first receiver for receiving a scrambled broadcast stream and a second receiver for receiving a plurality of control messages separate from the broadcast stream, the control messages including information for descrambling the broadcast stream.

The invention further provides a decoder for use in a conditional access system for decrypting encrypted broadcast content, comprising a first input module for receiving said encrypted broadcast content from a first communications channel and a second input module for receiving a plurality of control messages from a second communications channel, said control messages containing descrambling information for decrypting said broadcast content.

According to the invention, there is also provided a method for use in a conditional access system, in which a scrambled broadcast stream is transmitted to a decoder, said decoder being operable to receive a plurality of control messages including information for descrambling the broadcast stream, the method comprising sending said control messages to said decoder separately from said broadcast stream.

The invention yet further provides a method for use in a conditional access system, in which a scrambled broadcast stream is transmitted to a first decoder and a second decoder, said first and second decoders being operable to receive a plurality of control messages including information for descrambling the broadcast stream, the method comprising receiving a request to transmit a plurality of control messages to said second decoder separately from the broadcast stream.

Roaming can thereby be facilitated. By denying a service to the first decoder while the control message stream is being sent to the second decoder, use of the service at the subscriber's home location can be prevented whilst roaming.

The first decoder does not need to have the ability to receive control messages separately and can be a conventional decoder.

According to the invention, there is additionally provided a conditional access system, comprising a first communications channel for carrying a broadcast stream, said stream being scrambled with a stream of control words and a second communications channel separate from the first channel for carrying a stream of entitlement control messages, said entitlement control messages incorporating information relating to the stream of control words for descrambling the broadcast stream.

The entitlement control messages can alone contain all of the information required to descramble the broadcast stream, so that there is no need for other messages, such as entitlement management messages, to be transmitted. Furthermore, in this case, a decoder for descrambling the broadcast stream does not require a smart card.

• Provisional Patent
• Utility Patent

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