Security device and head end in conditional access system and method for controlling illegal use in the system
First Claim
Patent Images
1. A security device for a conditional access system (CAS), the device comprising:
- a key database for storing a user key UK assigned to a subscriber; and
a decryptor for sequentially decrypting an update key EUK(BK) encrypted with the user key UK, a channel management key EBK(CMK) encrypted with the update key BK, and a control word ECMK(CW) encrypted with the channel management key CMK, and outputting a control word CW;
wherein at least one of the update key BK, the channel management key CMK and the control word CB are received from a head end of a conditional access system, and the user key UK is received from the key database.
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Abstract
A security device and a head end of a conditional access system (CAS), and a method for controlling illegal use of the conditional access system, capable of minimizing the number of entitlement management messages (EMMs) to be distributed from a head end to a user are provided. Update keys encrypted with user keys and channel management keys encrypted with the update keys are utilized.
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Citations
14 Claims
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1. A security device for a conditional access system (CAS), the device comprising:
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a key database for storing a user key UK assigned to a subscriber; and
a decryptor for sequentially decrypting an update key EUK(BK) encrypted with the user key UK, a channel management key EBK(CMK) encrypted with the update key BK, and a control word ECMK(CW) encrypted with the channel management key CMK, and outputting a control word CW;
wherein at least one of the update key BK, the channel management key CMK and the control word CB are received from a head end of a conditional access system, and the user key UK is received from the key database. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A head end for a conditional access system (CAS), the head end comprising:
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a key database for storing a user key UK assigned to a subscriber of a conditional access system;
a generator for generating an update key BK, a channel management key CMK, and a control word CW;
an encryptor for encrypting the update key BK with the user key UK, the channel management key CMK with the update key BK, and the control word CW with the channel management key CMK; and
a transmitter for transmitting the encrypted update key EUK(BK), the encrypted channel management key EBK(CMK), and the encrypted control word ECMK(CW) to the subscriber. - View Dependent Claims (9, 10, 11, 12)
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13. A method for controlling illegal use of a conditional access system (CAS), the method comprising the steps of:
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distributing an update key BK, a channel management key CMK, and a control word CW to a subscriber of a conditional access system;
encrypting an updated update key BKn with a user key UK of the subscriber, an updated channel management key CMKn with the updated update key BKn, and an updated control word CWn with the updated channel management key CMKn;
redistributing the encrypted updated update key BKn, the updated channel management key CMKn, and the updated control word CWn to the subscriber; and
sequentially decrypting the re-distributed encrypted update key EUK(BKn), channel management key EBK(CMKn), and control word ECMK(CWn) with the user key UK of the subscriber; and
updating the distributed update key BK, channel management key CMK, and control word CW with the updated update key BKn, updated channel management key CMKn, and updated control word CWn. - View Dependent Claims (14)
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Specification