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Renewable traitor tracing

  • US 9,520,993 B2
  • Filed: 09/19/2005
  • Issued: 12/13/2016
  • Est. Priority Date: 01/26/2001
  • Status: Active Grant
First Claim
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1. A method of preventing re-use of compromised sequence keys in a broadcast encryption system, the method comprising:

  • receiving a distributed protected file and a sequence key block at a receiver, the sequence key block being formulated to cryptographically revoke traitorous receivers;

    selecting a first Sequence Key from a plurality of Sequence Keys, the plurality of Sequence Keys being associated with the receiver, and the plurality of Sequence Keys being related by the sequence key block;

    determining by cryptographic testing that the first Sequence Key is compromised,cryptographic testing comprising applying the first Sequence Key to the sequence key block;

    determining that at least one additional Sequence Key is available;

    traversing the sequence key block to select a second Sequence Key from the plurality of sequence keys;

    determining by cryptographic testing that the second sequence key is compromised,cryptographic testing comprising applying the first Sequence Key to the sequence key block;

    traversing the remainder of the sequence key block and thereby determining that no uncompromised sequence keys can be determined from the sequence key block;

    identifying the receiver as traitorous based on the lack of uncompromised sequence keys.

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