Reduced hierarchy key management system and method

• US 7,970,132 B2
• Filed: 10/21/2008
• Issued: 06/28/2011
• Est. Priority Date: 08/09/2004
• Status: Active Grant

• Current Assignee: Comcast Cable Communications LLC (Comcast Corporation)
• Original Assignee: Comcast Cable Holdings LLC (Comcast Corporation)
• Inventors: Fahrny, James William, Compton, Charles L.
• Primary Examiner(s): Brown; Christopher J
• Assistant Examiner(s): Le; Canh
• Application Number:
  US12/255,101
• Publication Number:
  US 20090052661A1
• Time in Patent Office: 980 Days
• Field of Search: 380/42, 380/239, 380/212, 380/227, 380/201, 380/228, 380/282, 380/231, 380/223, 380/210, 380/44, 380/37, 380/277, 380/278, 380/200, 380/264, 713/193, 713/189, 713/176, 726/26, 725 1- 4, 725 25- 31, 725/63, 725/67, 725/68, 725/86, 725/87, 725/100, 725/135, 725/138, 725/139, 725/143, 725/144, 725/151, 725/105, 725/110
• US Class Current: 380/42
• CPC Class Codes: H04L 2209/60 Digital content management, e.g. content distribution
• CPC Class Codes: H04L 9/0836 using tree structure or hierarchical structure
• CPC Class Codes: H04L 9/0897 involving additional devices, e.g. trusted platform module [TPM], smartcard or USB
• CPC Class Codes: H04N 21/2347 involving video stream encryption
• CPC Class Codes: H04N 21/26613 for generating or managing keys in general key distribution for secret or secure communication involving central third party, e.g. key distribution center [KDC] or trusted third party [TTP] H04L9/083; network support of key management H04L63/06; key management for network security in communication control or processing H04W12/04
• CPC Class Codes: H04N 21/4405 involving video stream decryption
• CPC Class Codes: H04N 21/4623 Processing of entitlement messages, e.g. ECM [Entitlement Control Message] or EMM [Entitlement Management Message] arrangements for conditional access to broadcast information or to broadcast-related services H04H60/14
• CPC Class Codes: H04N 21/835 Generation of protective data, e.g. certificates protecting software against unauthorised usage in a vending or licensing environment G06F21/10
• CPC Class Codes: H04N 7/162 Authorising the user terminal, e.g. by paying; Registering the use of a subscription channel, e.g. billing
• CPC Class Codes: H04N 7/1675 Providing digital key or authorisation information for generation or regeneration of the scrambling sequence pseudo-random number generators in general G06F7/58
• CPC Class Codes: H04N 7/17309 Transmission or handling of upstream communications

Abstract

A controller receives an encrypted media stream (“EMS”) and an identifier indicative of a selected content key from a headend. The EMS is encrypted with an encryption key and can be decrypted with a corresponding decryption key which is determinable from the selected content key. The controller receives indexes and content keys from the headend prior to receiving the EMS. Each index respectively corresponds to an identifier with one index corresponding to the identifier indicative of the selected content key. The content keys correspond to the indexes with one content key corresponding to the index corresponding to the identifier indicative of the selected content key. The controller selects the index corresponding to the identifier indicative of the selected content key upon receiving the EMS, determines the selected content key from the selected index, determines the decryption key from the selected content key, and decrypts the EMS with the decryption key.

Claims

1. A controller comprising:

digital circuitry configured to receive an encrypted media stream from a provider, wherein the encrypted media stream is encrypted with an encryption key and is configured to be decrypted with a decryption key corresponding to the encryption key, wherein the decryption key is configured to be determined from a selected content key;

wherein the digital circuitry is configured to receive with the encrypted media stream an identifier indicative of the selected content key from the provider without receiving with the encrypted media stream either the decryption key or the selected content key;

a first non-transitory memory including a plurality of indexes received from the provider prior to the encrypted media stream being received by the digital circuitry, wherein each index respectively corresponds to an identifier, with one of the indexes corresponding to the identifier indicative of the selected content key; and

a second non-transitory memory including a plurality of content keys received from the provider prior to the encrypted media stream being received by the digital circuitry, wherein the plurality of content keys correspond to the plurality of indexes, with one of the content keys corresponding to the index which corresponds to the identifier indicative of the selected content key;

wherein the digital circuitry is configured to select from the first non-transitory memory the index corresponding to the identifier indicative of the selected content key in response to receiving the encrypted media stream;

wherein the digital circuitry is configured to determine from the second non-transitory memory the selected content key using the selected index;

wherein the digital circuitry is configured to determine the decryption key from the selected content key and decrypt the encrypted media stream with the decryption key.

2. The controller of claim 1 wherein:

the first non-transitory memory includes a content key index table which contains the plurality of indexes.

3. The controller of claim 1 wherein:

the second non-transitory memory includes a content key list which contains the plurality of content keys.

4. The controller of claim 1 wherein:

the digital circuitry, the first non-transitory memory, and the second non-transitory memory are part of a set-top-box.

5. The controller of claim 1 wherein:

the identifier indicative of the selected content key is a program identifier.

6. The controller of claim 1 wherein:

the identifier indicative of the selected content key is a video-on-demand identifier.

7. The controller of claim 1 wherein:

the first non-transitory memory receives the plurality of indexes from the provider in an entitlement management message downloaded from the provider to the first non-transitory memory prior to the encrypted media stream being received by the digital circuitry.

8. The controller of claim 1 wherein:

the second non-transitory memory receives the plurality of content keys from the provider in an entitlement management message downloaded from the provider to the second memory prior to the encrypted media stream being received by the digital circuitry.

9. The controller of claim 1 wherein:

determining the decryption key from the selected content key includes determining the decryption key from the selected content key and a working key modifier.

10. The controller of claim 9 wherein:

the digital circuitry is configured to determine the decryption key from the selected content key and the working key modifier using at least one of an exclusive OR (EXOR) and a hashing operator.

11. The controller of claim 1 wherein:

the plurality of indexes comprises a plurality of initialization vector (“

IV”

) values and the plurality of content keys comprises initialization vectors.

12. A method comprising:

receiving at a microprocessor an encrypted media stream from a provider remote from the microprocessor, wherein the encrypted media stream is encrypted with an encryption key and is configured to be decrypted with a decryption key corresponding to the encryption key, wherein the decryption key is configured to be determined from a selected content key;

receiving at the microprocessor with the encrypted media stream an identifier indicative of the selected content key from the provider without receiving with the encrypted media stream either the decryption key or the selected content key;

receiving at the microprocessor a plurality of indexes from the provider prior to receiving the encrypted media stream, wherein each index respectively corresponds to an identifier, with one of the indexes corresponding to the identifier indicative of the selected content key;

receiving at the microprocessor a plurality of content keys from the provider prior to receiving the encrypted media stream, wherein the plurality of content keys corresponds to the plurality of indexes, with one of the content keys corresponding to the index which corresponds to the identifier indicative of the selected content key;

selecting by the microprocessor the index corresponding to the identifier indicative of the selected content key in response to receiving the encrypted media stream;

determining by the microprocessor the selected content key using the selected index;

determining by the microprocessor the decryption key from the selected content key; and

decrypting by the microprocessor the encrypted media stream with the decryption key.

13. The method of claim 12 wherein:

receiving at the microprocessor the plurality of indexes from the provider prior to receiving the encrypted media stream includes receiving at the microprocessor the plurality of indexes from the provider in an entitlement management message downloaded from the provider to the microprocessor prior to receiving the encrypted media stream.

14. The method of claim 12 wherein:

receiving at the microprocessor the plurality of content keys from the provider prior to receiving the encrypted media stream includes receiving at the microprocessor the plurality of content keys from the provider in an entitlement management message downloaded from the provider to the microprocessor prior to receiving the encrypted media stream.

15. A system comprising:

one or more servers at a provider operation location; and

a client device remotely located from the provider operation location;

wherein a media stream is encrypted at the provider operation location with an encryption key to generate an encrypted media stream, wherein the encrypted media stream is configured to be decrypted with a decryption key corresponding to the encryption key, wherein the decryption key is configured to be determined from a selected content key;

wherein the encrypted media stream is transmitted with an identifier indicative of the selected content key from the provider operation location to the client device without transmitting with the encrypted media stream either the decryption key or the selected content key;

wherein prior to transmitting the encrypted media stream with the identifier to the client device, a plurality of indexes is transmitted from the provider operation location to the client device, wherein each index respectively corresponds to an identifier, with one of the indexes corresponding to the identifier indicative of the selected content key;

wherein prior to transmitting the encrypted media stream with the identifier to the client device, a plurality of content keys is transmitted from the provider operation location to the client device, wherein the plurality of content keys corresponds to the indexes, with one of the content keys corresponding to the index which corresponds to the identifier indicative of the selected content key;

wherein the client device is configured to select the index corresponding to the identifier indicative of the selected content key in response to receiving the encrypted media stream, determine the selected content key using the selected index, determine the decryption key from the selected content key, and decrypt the encrypted media stream with the decryption key.

16. The system of claim 15 further comprising:

a network;

wherein the encrypted media stream is transmitted with an identifier, the plurality of indexes, and the plurality of content keys from the provider operation location over the network to the client device.

17. The system of claim 15 wherein:

the client device is a set-top-box.

18. The system of claim 15 wherein:

the client device is located at a consumer location remote from the provider operation location.

19. The system of claim 15 wherein:

the plurality of indexes is transmitted from the provider operation location to the client device in an entitlement management message prior to transmitting the encrypted media stream with the identifier to the client device.

20. The system of claim 15 wherein:

the plurality of content keys is transmitted from the provider operation location to the client device in an entitlement management message prior to transmitting the encrypted media stream with the identifier to the client device.

21. A controller comprising:

a microprocessor,

a memory storing executable instructions, which when executed by the microprocessor, cause the controller to provide;

a decryption engine for receiving an encrypted media stream from a provider, wherein the encrypted media stream is encrypted with an encryption key and is configured to be decrypted with a decryption key corresponding to the encryption key, wherein the decryption key is configured to be determined from a selected content key,

wherein the decryption engine receives with the encrypted media stream an identifier indicative of the selected content key from the provider without receiving with the encrypted media stream either the decryption key or the selected content key;

a first memory including a plurality of indexes received from the provider prior to the encrypted media stream being received by the decryption engine, wherein each index respectively corresponds to an identifier, with one of the indexes corresponding to the identifier indicative of the selected content key; and

a second memory including a plurality of content keys received from the provider prior to the encrypted media stream being received by the decryption engine, wherein the plurality of content keys correspond to the indexes, with one of the content keys corresponding to the index which corresponds to the identifier indicative of the selected content key;

wherein the decryption engine selects from the first non-transitory memory the index corresponding to the identifier indicative of the selected content key in response to receiving the encrypted media stream;

wherein the decryption engine determines from the second non-transitory memory the selected content key using the selected index;

wherein the decryption engine determines the decryption key from the selected content key and decrypts the encrypted media stream with the decryption key.

22. The controller of claim 21 wherein:

the first non-transitory memory includes a content key index table which contains the plurality of indexes.

23. The controller of claim 21 wherein:

the second non-transitory memory includes a content key list which contains the plurality of content keys.

24. The controller of claim 21 wherein:

the decryption engine, the first non-transitory memory, and the second non-transitory memory are part of a set-top-box.

25. The controller of claim 21 wherein:

the identifier indicative of the selected content key is a program identifier.

26. The controller of claim 21 wherein:

the identifier indicative of the selected content key is a video-on-demand identifier.

27. The controller of claim 21 wherein:

the first non-transitory memory receives the plurality of indexes from the provider in an entitlement management message downloaded from the provider to the first non-transitory memory prior to the encrypted media stream being received by the decryption engine.

28. The controller of claim 21 wherein:

the second non-transitory memory receives the plurality of content keys from the provider in an entitlement management message downloaded from the provider to the second memory prior to the encrypted media stream being received by the decryption engine.

29. The controller of claim 21 wherein:

determining the decryption key from the selected content key includes the decryption engine determining the decryption key from the selected content key and a working key modifier.

30. The controller of claim 29 wherein:

the decryption engine determines the decryption key from the selected content key and the working key modifier using at least one of an exclusive OR (EXOR) and a hashing operator.

31. The controller of claim 21 wherein:

the plurality of indexes comprises a plurality of initialization vector (“

IV”

) values and the plurality of content keys comprises initialization vectors.