System for determining successful reception of a message
View Patent ↗A method for determining that all of a scrambled message has been successfully received, the scrambled message being scrambled in accordance with a scrambling key and being capable of being descrambled in accordance with a descrambling key, descrambling key generating information for generating the descrambling key being included within a control message (ECM) associated with the scrambled message. The method includes providing a scrambled message scrambled in accordance with a scrambling key, generating an unmodified ECM including descrambling key generating information for generating a descrambling key for descrambling the scrambled message, generating a first derived value based on the scrambled message using a first value derivation function, applying a first modification function to the unmodified ECM, the first modification function being based, at least in part, on the first derived value, thereby producing a modified ECM, transmitting the scrambled message and the modified ECM to a receiver, and performing, at the receiver, the following steps: generating a second derived value based on the received scrambled message using a second value derivation function, applying a second modification function to the modified ECM, the second modification function being based, at least in part, on the second derived value and being an inverse of the first modification function, thereby producing the unmodified ECM, and employing the unmodified ECM to determine that all of the message has been successfully received. Related apparatus and methods are also provided.
1. In a system where a scrambled message is scrambled in accordance with a scrambling key and is capable of being descrambled in accordance with a descrambling key, descrambling key generating information for generating the descrambling key being comprised within a control message (ECM) associated with the scrambled message, an unmodified ECM comprising descrambling key generating information for generating a descrambling key for descrambling the scrambled message being generated by the system, a first derived value based on the scrambled message using a first value derivation function being generated by the system, a first modification function being applied to the unmodified ECM thereby producing a modified ECM, the first modification function being based, at least in part, on the first derived value, the scrambled message and the modified ECM being transmitted to a receiver, a method comprising, at the receiver:
receiving the scrambled message and the modified ECM;
generating a second derived value based on the received scrambled message using a second value derivation function;
applying a second modification function to the modified ECM thereby producing the unmodified ECM, the second modification function being based, at least in part, on the second derived value; and
employing the unmodified ECM to determine that all of the message has been successfully received.
2. The method according to claim 1 , wherein the employing includes:
producing the descrambling key from the unmodified ECM; and
descrambling the scrambled message using the descrambling key.
3. A method for producing a modified ECM for use in a system for determining that all of a scrambled message has been successfully received, the scrambled message being scrambled in accordance with a scrambling key and being capable of being descrambled in accordance with a descrambling key, descrambling key generating information for generating the descrambling key being comprised within a control message (ECM) associated with the scrambled message, the method comprising:
providing a scrambled message scrambled in accordance with a scrambling key;
generating an unmodified ECM comprising descrambling key generating information for generating a descrambling key for descrambling the scrambled message;
generating a first derived value based on the scrambled message using a first value derivation function; and
applying a first modification function to the unmodified ECM thereby producing a modified ECM, the first modification function being based, at least in part, on the first derived value.
4. The method according to claim 3 and also comprising transmitting at least one of:
the modified ECM; and
the scrambled message.
5. In a system where a scrambled message is scrambled in accordance with a scrambling key and is capable of being descrambled in accordance with a descrambling key, descrambling key generating information for generating the descrambling key being comprised within a control message (ECM) associated with the scrambled message, an unmodified ECM comprising descrambling key generating information for generating a descrambling key for descrambling the scrambled message being generated by the system, a first derived value based on the scrambled message using a first value derivation function being generated by the system, a first modification function being applied to the unmodified ECM, the first modification function being based, at least in part, on the first derived value, thereby producing a modified ECM, the scrambled message and the modified ECM being transmitted to a receiver, apparatus comprising:
second value derivation apparatus for generating a second derived value based on the received scrambled message using a second value derivation function;
second modifying apparatus for applying a second modification function to the modified ECM thereby producing the unmodified ECM, the second modification function being based, at least in part, on the second derived value; and
employing apparatus for employing the unmodified ECM to determine that all of the message has been successfully received.
6. Apparatus according to claim 5 and also comprising:
a second smart card, wherein the second smart card comprises at least one of the following:
the second modifying apparatus; and
at least a portion of the employing apparatus.
7. Apparatus for producing a modified ECM for use in a system for determining that all of a scrambled message has been successfully received, the scrambled message being scrambled in accordance with a scrambling key and being capable of being descrambled in accordance with a descrambling key, descrambling key generating information for generating the descrambling key being comprised within a control message (ECM) associated with the scrambled message, the apparatus comprising:
a scrambler for scrambling a message in accordance with a scrambling key, thereby producing a scrambled message;
an ECM generator for generating an unmodified ECM comprising descrambling key generating information for generating a descrambling key for descrambling the scrambled message;
first value derivation apparatus for generating a first derived value based on the scrambled message using a first value derivation function; and
first modifying apparatus for applying a first modification function to the unmodified ECM thereby producing a modified ECM, the first modification function being based, at least in part, on the first derived value.
8. The apparatus according to claim 7 and also comprising a transmitter operative to transmit at least one of:
the modified ECM; and
the scrambled message.
9. Apparatus according to claim 7 and also comprising:
a first smart card, wherein the first smart card comprises at least one of the following:
the ECM generator; and
the first modifying apparatus.
10. In a system where a scrambled message is scrambled in accordance with a scrambling key and is capable of being descrambled in accordance with a descrambling key, descrambling key generating information for generating the descrambling key being comprised within a control message (ECM) associated with the scrambled message, a method comprising, at a receiver:
receiving an unmodified ECM comprising descrambling key generating information for generating a descrambling key for descrambling the scrambled message generated by the system;
applying a first modification function to the unmodified ECM, the first modification function being based, at least in part, on a first derived value based on the scrambled message, thereby producing a modified ECM;
receiving the scrambled message and the modified ECM;
generating a second derived value based on the received scrambled message using a second value derivation function;
applying a second modification function to the modified ECM thereby producing the unmodified ECM, the second modification function being based, at least in part, on the second derived value; and
employing the unmodified ECM to determine that all of the message has been successfully received.
11. In a system where a scrambled message is scrambled in accordance with a scrambling key and is capable of being descrambled in accordance with a descrambling key, descrambling key generating information for generating the descrambling key being comprised within a control message (ECM) associated with the scrambled message, apparatus comprising:
a receiver operative to receive:
the scrambled message; and
an unmodified ECM comprising descrambling key generating information for generating a descrambling key for descrambling the scrambled message;
second value derivation apparatus for generating a second derived value based on the received scrambled message using a second value derivation function;
second modifying apparatus for applying a second modification function to the modified ECM thereby producing the unmodified ECM, the second modification function being based, at least in part, on the second derived value; and
employing apparatus for employing the unmodified ECM to determine that all of the message has been successfully received.