SYSTEM, METHOD, AND SERVICE FOR TRACING TRAITORS FROM CONTENT PROTECTION CIRCUMVENTION DEVICES

• US 20090327717A1
• Filed: 06/05/2008
• Published: 12/31/2009
• Est. Priority Date: 12/08/2006
• Status: Active Grant

• Current Assignee: GlobalFoundries, Inc.
• Original Assignee: International Business Machines Corporation
• Inventors: Jin, Hongxia, Lotspiech, Jeffrey Bruce, Zigoris, Philip Anastasios
• Granted Patent: US 8,023,655 B2
• Time in Patent Office: Days
• US Class Current: 713/168
• CPC Class Codes: G09C 5/00 Ciphering apparatus or methods not provided for in the preceding groups, e.g. involving the concealment or deformation of graphic data such as designs, written or printed messages
• CPC Class Codes: H04L 2209/606 Traitor tracing
• CPC Class Codes: H04L 9/0891 Revocation or update of secret information, e.g. encryption key update or rekeying
• CPC Class Codes: H04L 9/32 including means for verifying the identity or authority of a user of the system or for message authentication, e.g. authorization, entity authentication, data integrity or data verification, non-repudiation, key authentication or verification of credentials

Abstract

A traitor tracing system generates a hypothesized model of the circumvention device that models a hypothesized set of device keys compromised by the circumvention device. The system iteratively invokes a subset tracing system to identify a compromised device key until substantially all the compromised device keys in the set of compromised device keys are identified so as to disable the circumvention device. A subset tracing system generates a circumvention device model that models behavior of a circumvention device using prior knowledge and The system iteratively selects and applies to the circumvention device a test based on the hypothesized model and the circumvention device model and receives a response from the circumvention device indicating a success of the test in playing protected content on the circumvention device. The system updates the hypothesized model using the received response, the selected test, a current version of the hypothesized model, and a current version of the circumvention device model to focus the test selecting process in determining the device keys obtained from the traitor.

Claims

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;

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

removing the compromised key, adding new keys to the hypothesized set of keys and updating the hypothesized model until the MKB created on the hypothesized set of device keys disables the circumvention device.

2. The method of claim 1, further comprising 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.

11. The method of claim 1, wherein the hypothesized model is represented by any of a tabular form, a function, a graphical model, and a Bayesian network.

12. The method of claim 1, wherein updating the hypothesized model comprises generating the probabilities of the newly added keys being in the circumvention device

3. A subset tracing method of identifying a compromised key from a circumvention device, the subset tracing method comprising:

generating a circumvention device model that models a behavior of a circumvention device;

selecting a test based on the hypothesized model and the circumvention device model to apply to the circumvention device;

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, 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 device.

4. The method of claim 3, wherein an iterative test comprises one or more of the test and one or more of the response, the iterative test being applied to the circumvention device until the compromised key is determined.

5. :

The method of claim 3, wherein the circumvention device comprises a plurality of compromised device keys.

6. The method of claim 3, wherein the test comprises a forensic media key block that obtains informative data about the compromised device key, by observing the response.

7. The method of claim 4, wherein the circumvention device model is fixed throughout the iterative test.

8. The method of claim 4, wherein the circumvention device model is modified as a result of at least one of the response, prior knowledge, and direction from a client.

9. The method of claim 3, wherein the circumvention device model comprises a set of tests from which the test is 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.

10. The method of claim 3, wherein the circumvention device model is represented by any of a tabular form, a function, a graphical model, and a Bayesian network.

13. The method of claim 3, wherein updating the hypothesized model comprises inference logic using any of a variable elimination, a belief propagation, and a junction tree.

14. The method of claim 13, wherein the inference logic utilizes an approximation algorithm comprising any of a sample based approximation, a partition-based approximation, and a loopy belief propagation.

15. The method of claim 3, wherein updating the hypothesized model comprises any of a graphic model or a Bayesian network to incorporate the response into the hypothesized model.

16. The method of claim 3, wherein selecting the test comprises utilizing gained informativeness information.

17. A computer program product having a plurality of executable instruction codes stored on a computer readable medium for tracing a traitor from a circumvention device, the circumvention device comprising at least one compromised device key obtained from the traitor, the computer program product comprising:

a set of instruction codes for generating a hypothesized model on a hypothesized set of device keys that models a hypothesis that the circumvention device comprises a hypothesized set of device keys;

a set of instruction codes for passing the hypothesized model and invoking the subset tracing method to identify a compromised key; and

a set of instruction codes for updating the hypothesized model.

18. The computer program product of claim 17, further comprising a set of instruction codes for 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.

22. The computer program product of claim 17, wherein the hypothesized model comprises a set of hypothesized device keys and a probability that the circumvention device contains the set of hypothesized device keys.

19. A computer program product having a plurality of executable instruction codes stored on a computer readable medium for tracing a traitor from a circumvention device, the circumvention device comprising at least one compromised device key obtained from the traitor, the computer program product comprising:

a set of instruction codes for generating a circumvention device model that models a behavior of the circumvention device;

a set of instruction codes for selecting a test based on the hypothesized model and the circumvention device model to apply to the circumvention device;

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

a set of instruction codes for updating the hypothesized model using the received response, 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

a set of instruction codes for testing the hypothesized model to determine the strength of the belief that the compromised device key is contained in the circumvention device.

20. The computer program product of claim 19, wherein the circumvention device comprises a plurality of sets of compromised device keys.

21. The computer program product of claim 19, wherein the test comprises a forensic media key block that obtains informativeness data about the compromised device key, by observing the response.

23. The computer program product of claim 19, wherein the circumvention device model is fixed throughout the iterative test.

24. The computer program product of claim 19, wherein the circumvention device model is modified as a result of at least one of the response, prior knowledge, and direction from a client.

25. The computer program product of claim 19, wherein the circumvention device model comprises a set of tests from which the test is 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.

26. The computer program product of claim 19, wherein the circumvention device model is represented by any of a tabular form, a function, a graphical model, and a Bayesian network.

27. The computer program product of claim 19, wherein the hypothesized model is represented by any of a tabular form, a function, a graphical model, and a Bayesian network.

28. The computer program product of claim 19, wherein updating the hypothesized model comprises inference logic using any of a variable elimination, a belief propagation, and a junction tree.

29. The computer program product of claim 28, wherein the inference logic utilizes an approximation algorithm comprising any of a sample based approximation, a partition-based approximation, and a loopy belief propagation.

30. The computer program product of claim 19, wherein updating the hypothesized model comprises any of a graphic model or a Bayesian network to incorporate the response into the hypothesized model.

31. The computer program product of claim 19, wherein the set of instruction codes for selecting the test comprises a set of instruction codes for utilizing gained informative information.

32. A processor-implemented system for tracing a traitor from a circumvention device, the circumvention device comprising at least one compromised device key obtained from the traitor, the system comprising:

means for 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;

means for passing the hypothesized model to the subset tracing method to identify a compromised device key; and

means for removing the compromised key, adding new keys to the hypothesized set of device keys and updating the hypothesized model until the MKB created on the hypothesized model can disable the circumvention device

33. The system of claim 32, further comprising means for 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.

34. A processor-implemented system for tracing a traitor from a circumvention device, the circumvention device comprising at least one compromised device key obtained from the traitor, the system comprising:

a circumvention device model module for generating a circumvention device model that models a behavior of the circumvention device;

the circumvention device model module generating a circumvention device model that models a behavior of the circumvention device;

a test selection module for selecting a test based on the hypothesized model and the circumvention device model to apply to the circumvention device;

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

the hypothesis update module updating the hypothesized model using the received response, 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

a significance module for testing the hypothesized model to determine the strength of the belief that the compromised device key is contained in the circumvention device.

35. The system of claim 34, wherein the circumvention device comprises a plurality of compromised device keys.

36. The system of claim 34, wherein the test comprises a forensic media key block that obtains informativeness data about the compromised device key, by observing the response.

37. A processor-implemented service for tracing a traitor from a circumvention device, the circumvention device comprising a set of compromised device keys obtained from the traitor, the service comprising:

generating a hypothesized model on a set of hypothesized device keys that models a hypothesis that the circumvention device comprises a hypothesized set of device keys;

passing on the hypothesized model to the subset tracing and detecting a compromised device key; and

updating the hypothesized model until the MKB created on the hypothesized set of keys can disable the circumvention device.