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System, Method, and Service for Tracing Traitors from Content Protection Circumvention Devices

  • US 20080137864A1
  • Filed: 12/08/2006
  • Published: 06/12/2008
  • Est. Priority Date: 12/08/2006
  • Status: Active Grant
First Claim
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1. A processor-implemented method of tracing a traitor from a circumvention device, the circumvention device comprising a set of compromised device keys obtained from the traitor, the method comprising:

  • generating a hypothesized model on a hypothesized set of device keys that models a hypothesis that the circumvention device comprises the hypothesized set of device keys, wherein the hypothesized model is represented by any of a tabular form, a function, a graphical model, and a Bayesian network;

    passing the hypothesized model to a subset tracing method to identify a compromised device key, the subset tracing method comprising;

    generating a circumvention device model that models a behavior of a circumvention device, whereinthe circumvention device model comprises a set of tests from which tests are selected, a set of key sets comprising one key set for each of the set of tests, and a probability for each of the key sets indicating a probability that the circumvention device will play the one of the set of tests associated with the key set; and

    the circumvention device model is represented by any of a tabular form, a function, a graphical model, and a Bayesian network;

    selecting a test, utilizing gained informativeness information and based on the hypothesized model and the circumvention device model, to apply to the circumvention device, wherein the test comprises a forensic media key block that obtains informative data about the compromised device key by observing the response;

    receiving a response from the circumvention device, the response indicating a success of the test in playing a protected content on the circumvention device;

    updating the hypothesized model using the received response, incorporating the response into the hypothesized model using any of a graphic model or a Bayesian network, and using the selected test, a current version of the hypothesized model, and a current version of the circumvention device model for selecting at least one test that identifies the compromised device keys obtained from the traitor; and

    testing the hypothesized model to determine the strength of the belief that the compromised device key is contained in the circumvention deviceremoving the compromised key, adding new keys to the hypothesized set of keys and updating the hypothesized model, wherein updating the hypothesized model comprises;

    generating the probabilities of the newly added keys being in the circumvention device; and

    applying an inference logic using any of a variable elimination, a belief propagation, and a junction tree, wherein the inference logic utilizes an approximation algorithm comprising any of a sample based approximation, a partition-based approximation, and a loopy belief propagation;

    iteratively detecting additional compromised device keys from the set of compromised device keys, until substantially all the compromised device keys in the set of compromised device keys are identified so as to disable the circumvention device; and

    creating a media key block MKB on the hypothesized set of device keys that disables the circumvention device.

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