Threshold cryptography scheme for conditional access systems
First Claim
1. A method for managing access to a signal, said method comprising:
- receiving, in a smart card, data representative of a first share;
constructing a symmetric scrambling key using said first share and at least two additional shares, said at least two additional shares being stored in said smart card; and
descrambling a signal using said constructed scrambling key to provide a descrambled signal.
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Accused Products
Abstract
A method and apparatus for managing access to a signal representative of an event of a service provider, including receiving said signal in a smart card, said signal being scrambled using a scrambling key, receiving, in said smart card, data representative of a first share; constructing said scrambling key using said first share and at least one additional share, said additional share being stored in said smart card; and descrambling said signal using said constructed scrambling key to provide a descrambled signal, wherein the step of constructing said scrambling key comprises calculating the Y-intercept of the line formed on said Euclidean plane by said first, and said at least one additional share.
28 Citations
19 Claims
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1. A method for managing access to a signal, said method comprising:
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receiving, in a smart card, data representative of a first share;
constructing a symmetric scrambling key using said first share and at least two additional shares, said at least two additional shares being stored in said smart card; and
descrambling a signal using said constructed scrambling key to provide a descrambled signal. - View Dependent Claims (2, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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3. A method for managing access to a signal representative of an event of a service provider, said method comprising:
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receiving said signal in a smart card, said signal being scrambled using a symmetric scrambling key;
receiving, in said smart card, data representative of a first share;
constructing said scrambling key using said first share and second and third shares, said second and third shares being stored in said smart card; and
descrambling said signal using said constructed scrambling key to provide a descrambled signal, wherein the step of constructing said scrambling key comprises calculating the Y-intercept of the curve formed on said Euclidean plane by said first, second and third shares. - View Dependent Claims (4, 5)
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6. A system for managing access between a service provider and a device having a smart card coupled thereto, said device performing the steps of:
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receiving a signal in a smart card, said signal being scrambled using a symmetric scrambling key;
receiving, in said smart card, data representative of a first share;
constructing said scrambling key using said first share and second and third shares, said second and third shares being stored in said smart card; and
descrambling said signal using said constructed scrambling key to provide a descrambled signal, wherein the step of constructing said scrambling key comprises calculating the Y-intercept of the curve formed on said Euclidean plane by said first, second and third shares.
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7. A conditional access system comprising:
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at least one program service provider; and
,a digital device including at least one smart card for receiving a scrambled signal and a first share transmitted by the at least one program service provider;
wherein said at least one smart card includes second and third shares stored therein for descrambling the scrambled signal, said second and third shares being used in conjunction with said first share to descramble said scrambled signal.
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18. A method for operating a conditional access system comprising the steps of:
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transmitting a scrambled signal and a first share from a service provider to a digital device;
receiving in the digital device said scrambled signal and said first share;
constructing a scrambling key using said first share and at least two additional shares, said at least two additional shares being stored in a smart card of the digital device; and
descrambling the signal using said constructed scrambling key to provide a descrambled signal.
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19. A conditional access system comprising:
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a transmitter; and
,a receiver including at least one smart card for receiving a scrambled signal and a first share transmitted by the transmitter, wherein said at least one smart card includes second and third shares stored therein for descrambling the scrambled signal, said second and third shares being used in conjunction with said first share to descramble said scrambled signal.
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Specification