Cryptographic method and apparatus for restricting access to transmitted programming content using program identifiers

• US 6,373,948 B1
• Filed: 08/15/1997
• Issued: 04/16/2002
• Est. Priority Date: 08/15/1997
• Status: Expired due to Term

• Current Assignee: WSOU Investments, LLC (WSOU Holdings, LLC)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Wool, Avishai
• Primary Examiner(s): Barron, Jr., Gilberto
• Assistant Examiner(s): MEISLAHN, DOUGLAS J
• Application Number:
  US08/912,186
• Time in Patent Office: 1,705 Days
• Field of Search: 380/20, 380/239, 380/241
• US Class Current: 380/241
• CPC Class Codes: H04H 60/23 using cryptography, e.g. encryption, authentication, key distribution
• CPC Class Codes: H04L 2209/56 Financial cryptography, e.g. electronic payment or e-cash
• CPC Class Codes: H04L 2209/60 Digital content management, e.g. content distribution
• CPC Class Codes: H04L 9/088 Usage controlling of secret information, e.g. techniques for restricting cryptographic keys to pre-authorized uses, different access levels, validity of crypto-period, different key- or password length, or different strong and weak cryptographic algorithms network architectures or network communication protocols for using time-dependent keys in a packet data network H04L63/068
• CPC Class Codes: H04L 9/14 using a plurality of keys or algorithms
• CPC Class Codes: H04N 21/2347 involving video stream encryption
• CPC Class Codes: H04N 21/2362 Generation or processing of Service Information [SI]
• CPC Class Codes: H04N 21/26606 for generating or managing entitlement messages, e.g. Entitlement Control Message [ECM] or Entitlement Management Message [EMM] arrangements for conditional access to broadcast information or to broadcast-related services H04H60/14
• 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 7/163 by receiver means only
• 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

Abstract

A system for restricting access to transmitted programming content is disclosed, which transmits a program identifier with the encrypted programming content. A set-top terminal or similar mechanism restricts access to the transmitted multimedia information using stored decryption keys. The set-top terminal preferably receives entitlement information periodically from the head-end, corresponding to one or more packages of programs that the customer is entitled to for a given period. Each program is preferably encrypted by the head-end server prior to transmission, using a program key, K_p, which may be unique to the program. The set-top terminal uses the received program identifier, p, together with the stored entitlement information, to derive the decryption key necessary to decrypt the program. Each of the k-bit program keys, K_p, used to encrypt transmitted programs is a linear combination of a defined set of k-bit master keys, m₁ . . . m₁. The head-end server preferably generates a new set of master keys for the matrix, M, once per billing period. Since each program key, K_p, is a linear combination of the set of master keys, M, a customer desiring r programs, obtains access to the smallest linear subspace of programs, U, that contains those r programs. In addition, a package consists of (2ⁱ−1) program identifiers for some i less than or equal to n, which need not all be assigned to programs. An optional check matrix, C, allows the set-top terminal to determine, in advance, whether a received program is in the entitled subspace, U.

Claims

1. A method of transmitting a program having restricted access to an end-user, said method comprising the steps of:

assigning a program identifier to said program, said program identifier uniquely identifying said program for a duration of said program;

defining a plurality of master keys;

providing entitlement information to said end-user derived from said master keys;

encrypting said program using a program key, said program key being a linear combination of said master keys and said program identifier determining which keys in said plurality of master keys are utilized to generate said program key; and

transmitting said encrypted program together with said program identifier to said end-user, whereby said end-user can derive said program key from only said program identifier and said entitlement information.

2. The method according to claim 1, wherein said program is a portion of a linear subspace of programs obtained by said end-user.

3. The method according to claim 1, wherein said programs are organized in a manner that allows programs with related content to fit into a low dimensional linear subspace.

4. The method according to claim 1, further comprising the step of providing entitlement information to said end-user derived from said master keys based on the set of programs obtained by said end-user.

5. The method according to claim 4, wherein said entitlement information includes a set of keys derived from said master keys based on the set of programs obtained by said end-user.

6. The method according to claim 4, wherein said entitlement information includes a basis matrix representing a linear subspace of programs obtained by said end-user.

7. The method according to claim 4, wherein said end-user uses said received program identifier to derive said program key from said stored entitlement information.

8. The method according to claim 1, wherein said plurality of master keys are linearly independent.

9. The method according to claim 1, wherein said program key for said program is obtained by multiplying said plurality of master keys by said program identifier.

10. The method according to claim 1, wherein said program identifier is interleaved with the transmission of said encrypted program.

11. The method according to claim 1, wherein said program identifier is transmitted on a control channel.

12. The method according to claim 1, further comprising the step of providing a check matrix to said end-user that permits said end-user to determine whether said end-user is entitled to said program.

13. A method of transmitting a program to a plurality of end-users, said method comprising the steps of:

providing entitlement information to said end-user derived from a set of master keys;

encrypting said program using a program key, said program having a program identifier that uniquely identifies said program for a duration of said program, said program key being a linear combination of a plurality of master keys and said program identifier determining which keys in said plurality of master keys are utilized to generate said program key; and

transmitting said encrypted program together with said program identifier to said end-user, said program being a portion of a linear subspace of programs obtained by said end-user, whereby said end-user can derive said program key from only said program identifier and said entitlement information.

14. The method according to claim 13, wherein said programs are organized in a manner that allows programs with related content to fit into a low dimensional linear subspace.

15. The method according to claim 13, further comprising the step of providing entitlement information to said end-user derived from said master keys based on the set of programs obtained by said end-user.

16. The method according to claim 15, wherein said entitlement information includes a set of keys derived from said master keys based on the set of programs obtained by said end-user.

17. The method according to claim 15, wherein said entitlement information includes a basis matrix representing a linear subspace of programs obtained by said end-user.

18. The method according to claim 15, wherein said end-user uses said received program identifier to derive said program key from said stored entitlement information.

19. The method according to claim 13, wherein said plurality of master keys are linearly independent.

20. The method according to claim 13, wherein said program key for said program is obtained by multiplying said plurality of master keys by said program identifier.

21. The method according to claim 13, further comprising the step of providing a check matrix to said end-user that permits said end-user to determine whether said end-user is entitled to said program.

22. A method of transmitting a program associated with at least one package of programs to a plurality of end-users, said method comprising the steps of:

providing entitlement information to said end-users based on the set of programs obtained by said end-user;

encrypting said program using a program key, said program having a program identifier that uniquely identifies said program for a duration of said program, said program key being a linear combination of a plurality of master keys and said program identifier determining which keys in said plurality of master keys are utilized to generate said program key; and

transmitting said program identifier with said encrypted program to said end-users, whereby said end-users can derive said program key from only said program identifier and said stored entitlement information if said end-user is entitled to said program.

23. The method according to claim 22, wherein said program is a portion of a linear subspace of programs obtained by said end-user.

24. The method according to claim 22, wherein said programs are organized in a manner that allows programs with related content to fit into a low dimensional linear subspace.

25. The method according to claim 22, further comprising the step of providing entitlement information to said end-user derived from said master keys based on the set of programs obtained by said end-user.

26. The method according to claim 25, wherein said entitlement information includes a set of keys derived from said master keys based on the set of programs obtained by said end-user.

27. The method according to claim 25, wherein said entitlement information includes a basis matrix representing a linear subspace of programs obtained by said end-user.

28. The method according to claim 25, wherein said end-user uses said received program identifier to derive said program key from said stored entitlement information.

29. The method according to claim 22, wherein said plurality of master keys are linearly independent.

30. The method according to claim 22, wherein said program key for said program is obtained by multiplying said plurality of master keys by said program identifier.

31. The method according to claim 22, further comprising the step of providing a check matrix to said end-user that permits said end-user to determine whether said end-user is entitled to said program.

32. A method for decoding an encrypted program, said method comprising the steps of:

receiving entitlement information from a provider of said program, said entitlement information based on a set of programs obtained by said customer;

receiving said encrypted program together with a program identifier that uniquely identifies said program for a duration of said program, said encrypted program encrypted with a program key, said program key being a linear combination of master keys and said program identifier determining which keys in said plurality of master keys are utilized to generate said program key;

deriving said program key from only said program identifier and said stored entitlement information; and

decrypting said encrypted program using said program key.

33. The method according to claim 32, wherein said program is a portion of a linear subspace of programs obtained by an end-user.

34. The method according to claim 32, wherein said entitlement information includes a set of keys derived from said master keys based on the set of programs obtained by an end-user.

35. The method according to claim 32, wherein said entitlement information includes a basis matrix representing a linear subspace of programs obtained by an end-user.

36. The method according to claim 32, wherein said plurality of master keys are linearly independent.

37. The method according to claim 32, wherein said program identifier is interleaved with the transmission of said encrypted program.

38. The method according to claim 32, wherein said program identifier is transmitted on a control channel.

39. The method according to claim 32, further comprising the step of receiving a check matrix that permits an end-user to determine whether said end-user is entitled to said program.

40. The method according to claim 32, wherein said program identifier is evaluated upon a request to view said program.

41. The method according to claim 32, wherein said program identifier is evaluated in advance of a request to view said program.

42. A method for receiving an encrypted program having restricted access, said method comprising the steps of:

receiving entitlement information derived from a set of master keys;

receiving said program together with a program identifier that uniquely identifies said program for a duration of said program, said program encrypted using a program key, said program key being a linear combination of a plurality of master keys and said program identifier determining which keys in said plurality of master keys are utilized to generate said program key;

deriving said program key from only said program identifier and said stored entitlement information, said entitlement information being derived from said master keys based on a linear subspace of programs obtained by said customer; and

decrypting said encrypted program using said program key.

43. The method according to claim 42, wherein said entitlement information includes a set of keys derived from said master keys based on the set of programs obtained by an end-user.

44. The method according to claim 42, wherein said entitlement information includes a basis matrix representing a linear subspace of programs obtained by an end-user.

45. The method according to claim 42, wherein said plurality of master keys are linearly independent.

46. The method according to claim 42, wherein said program identifier is interleaved with the transmission of said encrypted program.

47. The method according to claim 42, wherein said program identifier is transmitted on a control channel.

48. The method according to claim 42, further comprising the step of receiving a check matrix that permits an end-user to determine whether said end-user is entitled to said program.

49. The method according to claim 42, wherein said program identifier is evaluated upon a request to view said program.

50. The method according to claim 42, wherein said program identifier is evaluated in advance of a request to view said program.

51. An article of manufacture for transmitting a program having restricted access to an end-user, comprising:

a computer readable medium having computer readable program code means embodied thereon, said computer readable program code means comprising;

a step to assign a program identifier to said program that uniquely identifies said program for a duration of said program;

a step to define a plurality of master keys;

a step to provide entitlement information to said end-user derived from said master keys;

a step to encrypt said program using a program key, said program key being a linear combination of said master keys and said program identifier determining which keys in said plurality of master keys are utilized to generate said program key; and

a step to transmit said encrypted program together with said program identifier to said end-user, whereby said end-user can derive said program key from only said program identifier and said entitlement information.

52. An article of manufacture for decoding an encrypted program, comprising:

a computer readable medium having computer readable program code means embodied thereon, said computer readable program code means comprising;

a step to receive entitlement information from a provider of said program, said entitlement information based on a set of programs obtained by said customer;

a step to receive said program together with a program identifier that uniquely identifies said program for a duration of said program, said program encrypted using a program key, said program key being a linear combination of a plurality of master keys and said program identifier determining which keys in said plurality of master keys are utilized to generate said program key;

a step to derive said program key from only said program identifier and stored entitlement information, said entitlement information being derived from said master keys based on a linear subspace of programs obtained by said customer; and

a step to decrypt said encrypted program using said program key.