Streaming system for delivering encrypted data, and streaming method thereof

• US 20040156508A1
• Filed: 03/29/2004
• Published: 08/12/2004
• Est. Priority Date: 01/31/2002
• Status: Active Grant

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Ishiguro, Ryuji, Futagami, Motomasa, Tada, Keiko
• Granted Patent: US 7,337,320 B2
• Time in Patent Office: Days
• US Class Current: 380/281
• CPC Class Codes: H04L 2209/60 Digital content management, e.g. content distribution
• CPC Class Codes: H04L 63/064 Hierarchical key distribution, e.g. by multi-tier trusted parties
• CPC Class Codes: H04L 63/065 for group communications cryptographic mechanisms or cryptographic arrangements for key management involving conference or group key H04L9/0833
• CPC Class Codes: H04L 65/1101 Session protocols
• CPC Class Codes: H04L 65/762 at the source reformatting of additional data in video distribution servers H04N21/2355
• CPC Class Codes: H04L 65/764 at the destination reformatting of additional data in video clients H04N21/4355
• CPC Class Codes: H04L 9/0822 using key encryption key
• CPC Class Codes: H04L 9/0836 using tree structure or hierarchical structure
• CPC Class Codes: H04L 9/0891 Revocation or update of secret information, e.g. encryption key update or rekeying

Abstract

The present invention is directed to a streaming system for encrypting encrypted data such as music and image, etc. to perform stream distribution thereof. Client terminals (30) used in this system structure leaves of the hierarchical tree structure, and hold a key set consisting of a route key, node keys and the own leaf key on a path of this tree structure, whereby SDP file is transmitted from a stream server (20). In the SDP file, there is stored encrypted information consisting of EKB including data encrypted by selection key that only specific client terminal holds and encrypted contents key data in which contents key has been encrypted. Only specific client terminal having selection key in key set (selected client terminal) decodes contents key from selection key to decode encrypted contents data caused to undergo stream distribution into contents data to perform real time reproduction thereof.

Claims

1. A streaming system including:

client terminals for decoding encrypted contents data in which contents data has been encrypted by contents key; and

a stream server for distributing the encrypted contents data and decoding information for decoding the encrypted contents data to the client terminals,

wherein the decoding information includes encrypted contents key data in which the contents key has been encrypted.

2. The streaming system as set forth in claim 1,

wherein the decoding information includes encrypted decode key data in which decode key for decoding the encrypted contents key data into the contents key has been encrypted.

3. The streaming system as set forth in claim 1,

wherein the decoding information is stored within a Session Description Protocol (SDP) file transmitted to the client terminals prior to stream distribution of the encrypted contents data by the stream server.

4. The streaming system as set forth in claim 2,

wherein the client terminals are structured as leaves of a hierarchical tree structure, each of which holds a key set consisting of a specific leaf key, node keys and a route key on a path to the route in a key tree consisting of the route key, node keys and leaf keys which are specific to the route, nodes and leaves of the hierarchical tree structure,

wherein the encrypted decode key data is stored in an Effective Key Block (EKB),

wherein the Effective Key Block (EKB) includes data portion for storing the encrypted decode key data encrypted by a selection key which is either one of key sets of one or more selection client terminals selected from the client terminals, and tag portion for identifying the position of the encrypted decode key data in the hierarchical tree structure, and

wherein the client terminal includes a first decode means for decoding the decode key by the selection key on the basis of information of the tag portion from the encrypted decode key data when the selection key coincides with either one of the key sets specific to the client terminals, a second decode means for decoding the contents key from the encrypted contents key data which is encrypted by the decode key, and a third decode means for decoding the contents data from the encrypted contents data which is encrypted by the contents key.

5. The streaming system as set forth in claim 4,

wherein the route and the route key are respectively the summit node and the summit node key specific to the summit node when one node of the hierarchical tree structure is the summit.

6. The streaming system as set forth in claim 4,

wherein the decode key is an updated route key or an updated node key in which the route key and/or the node keys of the key set have been updated by decode processing using the Effective Key Block (EKB) by the first decode processing means.

7. A streaming method including:

a step of transmitting decoding information for decoding encrypted contents data in which contents data has been encrypted by contents key from a stream server to client terminals;

a step of performing stream distribution of the encrypted contents data from the stream server to the client terminals; and

a decode step of allowing the client terminal to decode the encrypted contents data on the basis of the decoding information,

wherein the decoding information includes encrypted contents key data in which the contents key has been encrypted.

8. The streaming method as set forth in claim 7,

wherein the decoding information includes encrypted decode key data in which decode key for decoding the encrypted contents data into the contents key has been encrypted.

9. The streaming method as set forth in claim 7,

wherein the decoding information is stored within a Session Description Protocol (SDP) file transmitted from the stream server to the client terminals prior to stream distribution of the encrypted contents data by the stream server.

10. The streaming method as set forth in claim 8,

wherein the client terminals are structured as leaves of a hierarchical tree structure, each of which holds a key set consisting of a specific leaf key, node keys and a route key on a path to the route in a key tree consisting of the route key, node keys and leaf keys which are specific to the route, nodes and leaves of the hierarchical tree structure,

wherein the encrypted decode key data is stored in an Effective Key Block (EKB),

wherein the Effective Key Block (EKB) includes data portion for storing the encrypted decode key data encrypted by a selection key which is either one of key sets of one or more selection client terminals selected from the client terminals, and tag portion for identifying the position of the encrypted decode key data in the hierarchical tree structure, and

wherein the decode step includes a first decode step of decoding the decode key by the selection key on the basis of information of the tag portion from the encrypted decode key data when the selection key coincide with either one of key sets specific to the client terminals, a second decode step of decoding the contents key from the encrypted contents key data which is encrypted by the decode key, and a third decode step of decoding the contents data from the encrypted contents data which is encrypted by the contents key.

11. The streaming method as set forth in claim 10,

wherein the route and the route key are respectively the summit node and the summit node key specific to the summit node when one node of the hierarchical tree structure is the summit.

12. The streaming method as set forth in claim 10,

wherein the decode key is an updated route key or an updated node key in which the route key and/or the node keys of the key set have been updated by decode processing using the Effective Key Block (EKB) by the first decode step.

13. A client terminal including:

receiving means for receiving, from a stream server, decoding information for decoding encrypted contents data in which contents data has been encrypted by contents key;

stream receiving means for receiving the encrypted contents data caused to undergo stream distribution from the stream server; and

decode means for performing the decode processing,

wherein the decoding information includes encrypted contents key data in which the contents key for decoding the encrypted contents data has been encrypted.

14. The client terminal as set forth in claim 13,

wherein the decoding information includes encrypted decode key data in which decode key for decoding the encrypted contents key data into the contents key has been encrypted.

15. The client terminal as set forth in claim 13,

wherein the decoding information is stored within a Session Description Protocol (SDP) file received from the stream server prior to the stream reception.

16. The client terminal as set forth in claim 14,

wherein the client terminals are structured as leaves of a hierarchical tree structure, each of which holds a key set consisting of a specific leaf key, node keys and a route key on a path to the route in a key tree consisting of the route key, node keys and leaf keys which are specific to the route, nodes and leaves of the hierarchical tree structure,

wherein the encrypted decode key data is stored in an Effective Key Block (EKB),

wherein the Effective Key Block (EKB) includes data portion in which the encrypted decode key data encrypted by a selection key which is either one of the route key, the node keys and the leaf keys is stored, and tag portion for identifying the position of the encrypted decode key data in the hierarchical tree structure, and

wherein the decode means comprises a first decode means for decoding the decode key by the selection key on the basis of information of the tag portion from the encrypted decode key data when the selection key coincides with either one of the key sets, a second decode means for decoding the contents key from the encrypted contents key data which is encrypted by the decode key, and a third decode means for decoding the contents data from the encrypted contents data which is encrypted by the contents key.

17. The client terminal as set forth in claim 16,

wherein the route and the route key are respectively the summit node and the summit node key specific to the summit node when one node of the hierarchical tree structure is the summit.

18. The client terminal as set forth in claim 16,

wherein the decode key is an updated route key or an updated node key in which the route key and/or the node keys of the key set have been updated by decode processing using the Effective Key Block (EKB) by the first decode means.

19. A contents data decoding method including:

a receiving step of receiving, from a stream server, decoding information for decoding encrypted contents data in which contents data has been encrypted by contents key;

a stream receiving step of receiving the encrypted contents data caused to undergo stream distribution from the stream server; and

a decode step of performing the decode processing,

wherein the decoding information includes encrypted contents key data in which the contents key for decoding the encrypted contents data has been encrypted.

20. The contents data decoding method as set forth in claim 19,

wherein the decoding information includes encrypted decode key data in which decode key for decoding the encrypted contents data into the contents key has been encrypted.

21. The contents data decoding method as set forth in claim 19,

wherein the decoding information is stored in a Session Description Protocol (SDP) file received from the stream server prior to the stream reception.

22. The contents data decoding method as set forth in claim 20,

wherein the encrypted decode key data is stored in an Effective Key Block (EKB),

wherein the Effective Key Block (EKB) includes data portion for storing the encrypted decode key data encrypted by a selection key which is either one of a route key, node keys and leaf keys which are respectively specific to the route, nodes and leaves of the hierarchical tree structure, and tag portion for identifying the position of the encrypted decode key data in the hierarchical tree structure, and

wherein the decode step includes a first decode step of decoding the decode key by the selection key on the basis of information of the tag portion from the encrypted decode key data when the selection key coincides with either one of key sets each consisting of a specific leaf key that a client terminal structured as leaf of the hierarchical tree structure has, node keys and a route key on a path to the route in a key tree consisting of the route key, node keys and leaf keys which are specific to the route, nodes and leaves of the hierarchical tree structure, a second decode step of decoding the contents key from the encrypted contents key data which is encrypted by the decode key, and a third decode step of decoding the contents data from the encrypted contents data which is encrypted by the contents key.

23. A program for allowing computer to execute a predetermined operation,

the program including:

a receiving step of receiving, from a stream server, decoding information for decoding encrypted contents data in which contents data has been encrypted by contents key;

a stream receiving step of receiving the encrypted contents data caused to undergo stream distribution from the stream server; and

a decode step of performing the decode processing,

wherein the decoding information includes encrypted contents key data in which the contents key for decoding the encrypted contents data has been encrypted.

24. The program as set forth in claim 23,

wherein the decoding information includes encrypted decode key data in which decode key for decoding the encrypted contents key data into the contents key has been encrypted.

25. The program as set forth in claim 23,

wherein the decoding information is stored in a Session Description Protocol (SDP) file received from the stream server prior to the stream reception.

26. The program as set forth in claim 24,

wherein the encrypted decode key data is stored in an Effective Key Block (EKB),

wherein the Effective Key Block (EKB) includes data portion for storing the encrypted decode key data encrypted by a selection key which is either one of a route key, node keys and leaf keys which are respectively specific to the route, nodes and leaves of a hierarchical tree structure, and tag portion for identifying the position of the encrypted decode key data in the hierarchical tree structure, and

wherein the decode step includes a first decode step of decoding the decode key by the selection key on the basis of information of the tag portion from the encrypted decode key data when the selection key coincides with either one of key sets each consisting of a specific leaf key that a client terminal structured as leaf of the hierarchical structure has, and node keys and a route key on a path to the route in a key tree consisting of the route key, node keys and leaf keys which are specific to the route, nodes and leaves of the hierarchical tree structure, a second decode step of decoding the contents key from the encrypted contents key data which is encrypted by the decode key, and a third decode step of decoding the contents data from the encrypted contents data which is encrypted by the contents key.

27. A computer readable recording medium adapted so that program for allowing computer to execute a predetermined operation is recorded,

the program including:

a receiving step of receiving, from a stream server, decoding information for decoding encrypted contents data in which contents data has been encrypted by contents key;

a stream receiving step of receiving the encrypted contents data caused to undergo stream distribution from the stream server; and

a decode step of performing the decode processing,

wherein the decoding information includes encrypted contents key data in which the contents key for decoding the encrypted contents data into the contents data has been encrypted.

28. The recording medium as set forth in claim 27,

wherein the decoding information includes encrypted decode key data in which decode key for decoding the encrypted contents key data into the contents key has been encrypted.

29. The recording medium as set forth in claim 27,

wherein the decoding information is stored in a Session Description Protocol (SDP) file received from the stream server prior to the stream reception.

30. The recording medium as set forth in claim 28,

wherein the encrypted decode key data is stored in an Effective Key Block (EKB),

wherein the Effective Key Block (EKB) includes data portion for storing the encrypted decode key data encrypted by a selection key which is either one of a route key, node keys and leaf keys which are specific to the route, nodes and leaves of a hierarchical tree structure, and tag portion for identifying the position of the encrypted decode key data in the hierarchical tree structure, and

wherein the decode step includes a first decode step of decoding the decode key by the selection key on the basis of information of the tag portion from the encrypted decode key data when the selection key coincides with either one of key sets each consisting of a specific leaf key that a client terminal structured as leaf of the hierarchical tree structure has, and node keys and a route key on a path to the route in a key tree consisting of the route key, node keys and leaf keys which are specific to the route, nodes and leaves of the hierarchical tree structure, a second decode step of decoding the contents key from the encrypted contents key data which is encrypted by the decode key, and a third decode step of decoding the contents data from the encrypted contents data which is encrypted by the contents key.

31. A stream server including:

transmitting means for transmitting decoding information to client terminals; and

distribution means for performing stream distribution of encrypted contents data in which contents data has been encrypted by contents key to the client terminals,

wherein the decoding information includes encrypted contents key data in which the contents key for decoding the encrypted contents data into the contents data has been encrypted.

32. The stream server as set forth in claim 31,

wherein the decoding information includes encrypted decode key data in which decode key for decoding the encrypted contents data into the contents key has been encrypted.

33. The stream server as set forth in claim 31,

wherein the decoding information is stored in a Session Description Protocol (SDP) file transmitted before the enciphered contents data is caused to undergo stream distribution.

34. The stream server as set forth in claim 32,

wherein three is delivered streaming distribution data prepared so that additional information including an Effective Key Block (EKB) in which the encrypted decode key data has been stored and a Session Description Protocol (SDP) file in which the encrypted contents key data has been stored is added to the encrypted contents data,

wherein transmitting means which transmits the decoding information serves to transmit the Session Description Protocol (SDP) file prior to the stream distribution,

wherein the client terminal holds a key set consisting of keys on a path to the route in a key tree consisting of a route key, node keys and leaf keys which are specific to the route, nodes and the leaves of a hierarchical tree structure in which plural client terminals are structured as leaves,

wherein the Effective Key Block (EKB) includes data portion in which the encrypted decode key data has been stored, and tag portion for identifying the position of the encrypted decode key data in the hierarchical tree structure, and

wherein the encrypted decode key data can be decoded into the decode key on the basis of information of the tag portion by either one of keys included in a key set of one or more selection client terminals selected from the plural client terminals.

35. The stream server as set forth in claim 34,

wherein the route and the route key are respectively the summit node and the summit node key specific to the summit node when one node of the hierarchical tree structure is the summit.

36. The stream server as set forth in claim 34,

wherein the decode key is an updated route key or an updated node key in which the route key and/or the node keys of the key set have been updated by decode processing using the Effective Key Block (EKB) by the first decode means.

37. The stream server as set forth in claim 32,

wherein there is delivered streaming distribution data prepared so that additional information including a Session Description Protocol (SDP) file is added to the encrypted contents data,

the stream server including

data supplement means for supplementing an Effective Key Block (EKB) within which the encrypted decode key data has been stored and the encrypted contents key data to the Session Description Protocol (SDP) file,

wherein transmitting means which transmits the decoding information serves to transmit Session Description Protocol (SDP) file to which the Effective Key Block (EKB) and the encrypted contents data have been supplemented by the data supplement means prior to the stream distribution,

wherein the client terminal holds a key set consisting of keys on a path to the route in a key tree consisting of a route key, node keys and leaf keys which are respectively specific to the route, nodes and leaves of the hierarchical tree structure in which plural client terminals are structured as leaves,

wherein the Effective Key Block (EKB) includes data portion in which the encrypted decode key data has been stored, and tag portion for identifying the position of the encrypted decode key data in the hierarchical tree structure, and

wherein the encrypted decode key data can be decoded into the decode key on the basis of information of the tag portion by either one of keys included in a key set of one or more selection client terminal selected from the plural client terminals.

38. The stream server as set forth in claim 37,

wherein the route and the route key are respectively the summit node and the summit node key specific to the summit node when one node of the hierarchical tree structure is the summit.

39. The stream server as set forth in claim 37,

wherein the decode key is an updated route key or an updated node key in which the route key and/or the node keys of the key set have been updated by decode processing using the Effective Key Block (EKB) by the first decode means.

40. A data distribution method including:

a transmitting step of transmitting decoding information to client terminal terminals; and

a distribution step of performing stream distribution of encrypted contents data in which contents data has been encrypted by contents key to the client terminals,

wherein the decoding information includes encrypted contents key data in which the contents key for decoding the encrypted contents data into the contents data has been encrypted.

41. The data distribution method as set forth in claim 40,

wherein the decoding information includes encrypted decode key data in which decode key for decoding the encrypted contents data into the contents key has been encrypted.

42. The data distribution method as set forth in claim 40,

wherein the decoding information is stored within a Session Description Protocol (SDP) transmitted prior to stream distribution of the encrypted contents data.

43. The data distribution method as set forth in claim 41, including,

a step of receiving streaming distribution data prepared so that additional information including an Effective Key Block in which the encrypted decode key data has been stored and a Session Description Protocol (SDP) file in which the encrypted contents key data has been stored is added to the encrypted contents data,

wherein the transmitting step of transmitting the decoding information is a step of transmitting the Session Description Protocol (SDP) file prior to the stream distribution,

wherein the client terminal holds a key set consisting of keys on a path to the route in a key tree consisting of a route key, node keys and leaf keys which are specific to the route, nodes and leaves of the hierarchical tree structure in which plural client terminals are structured as leaves,

wherein the Effective Key Block (EKB) includes data portion in which the encrypted decode key data has been stored, and tag portion for identifying the position of the encrypted decode key data in the hierarchical tree structure, and

wherein the encrypted decode key data can be decoded into the decode key on the basis of information of the tag portion by either one of keys included in a key set of one or more selection client selected from the plural client terminals,

44. The data distribution method as set forth in claim 41, including:

a step of receiving streaming distribution data prepared so that additional information including a Session Description Protocol (SDP) file is added to the encrypted contents data, and

a data supplement step of supplementing an Effective Key Block (EKB) in which the encrypted decode key data has been stored and the encrypted contents key data to the Session Description Protocol (SDP) file,

wherein the transmitting step of transmitting decoding information is a step of transmitting the Session Description Protocol (SDP) file to which the Effective Key Block (EKB) and the encrypted contents key data have been supplemented by the data supplement step prior to the stream distribution,

wherein the client terminal holds a key set consisting of keys on a path to the route in a key tree consisting of a route key, node keys and leaf key which are specific to the route, nodes and leaves of the hierarchical tree structure in which plural client terminals are structured as leaves,

wherein the Effective Key Block (EKB) includes data portion in which the encrypted decode key data has been stored, and tag portion for identifying the position of the encrypted decode key data in the hierarchical tree structure, and

wherein the encrypted decode key data can be decoded into the decode key on the basis of information of the tag portion by either one of keys included in a key set of one or more selection client terminals selected from the plural client terminals.

45. A program for allowing computer to execute a predetermined operation, the program including:

a transmitting step of transmitting decoding information to client terminals; and

a distribution of performing stream distribution of encrypted contents data in which contents data has been encrypted by contents key to the client terminals,

wherein the decoding information includes encrypted contents key data in which the contents key for decoding the encrypted contents data into the contents data has been encrypted.

46. The program as set forth in claim 45,

wherein the decoding information includes encrypted decode key data in which decode key for decoding the encrypted contents key data into the contents key has been encrypted.

47. The program as set forth in claim 45,

wherein the decoding information is stored a Session Description Protocol (SDP) file transmitted prior to stream distribution of the encrypted contents data.

48. The program as set forth in claim 46, including

a step of receiving streaming distribution data prepared so that additional information including an Effective Key Block (EKB) in which the encrypted decode key data has been stored and a Session Description Protocol (SDP) file in which the encrypted contents key data has been stored is added to the encrypted contents data,

wherein the transmitting step of transmitting the decoding information is a step of transmitting the Session Description Protocol (SDP) file prior to the stream distribution,

wherein the client terminal holds a key set consisting of keys on a path to the route in a key tree consisting of a route key, node keys and leaf keys which are respectively specific to the route, nodes and leaves of the hierarchical tree structure in which plural client terminals are structured as leaves,

wherein the Effective Key Block (EKB) includes data portion in which the encrypted decode key data has been stored, and tag portion for identifying the position of the encrypted decode key data in the hierarchical tree structure, and

wherein the encrypted decode key data can be decoded into the decode key on the basis of information of the tag portion by either one of keys included in a key set of one or more selection client terminals selected from the plural client terminals.

49. The program as set forth in claim 46, including:

a step of receiving streaming distribution data prepared so that additional information including a Session Description Protocol (SDP) file is added to the encrypted contents data; and

a data supplement step of supplementing an Effective Key Block (EKB) in which the encrypted decode key data has been stored and the encrypted contents key data to the Session Description Protocol (SDP) file,

wherein the transmitting step of transmitting the decoding information is a step of transmitting the Session Description Protocol (SDP) file to which the Effective Key Block (EKB) and the encrypted contents key data have been supplemented by the data supplement step prior to the stream distribution,

wherein the client terminal holds a key set consisting of keys on a path to the route in a key tree consisting of a route key, node keys and leaf keys which are respectively specific to the route, nodes and leaves of the hierarchical tree structure in which plural client terminals are structured as leaves,

wherein the Effective Key Block (EKB) includes data portion in which the encrypted decode key data has been stored, and tag portion for identifying the position of the encrypted decode key data in the hierarchical tree structure, and

wherein the encrypted decode key data can be decoded into the decode key on the basis of information of the tag portion by either one of keys included in a key set of one or more selection client terminal selected from the plural client terminals.

50. A computer readable recording medium adapted so that program for allowing computer to execute a predetermined operation is recorded,

the program including:

a transmitting step of transmitting decoding information to client terminals; and

a distribution step of performing stream distribution of encrypted contents data in which contents data has been encrypted by contents key to the client terminals,

wherein the decoding information includes encrypted contents key data in which the contents key for decoding the encrypted contents data into the contents data has been encrypted.

51. The recording medium as set forth in claim 50,

wherein the decoding information includes encrypted decode key data in which decode key for decoding the encrypted contents data into the contents key has been encrypted.

52. The recording medium as set forth in claim 50,

wherein the decoding information is stored in a Session Description Protocol (SDP) file transmitted prior to stream distribution of the encrypted contents data.

53. The recording medium as set forth in claim 51,

the program including:

a step of receiving streaming distribution data prepared so that additional information including an Effective Key Block (EKB) in which the encrypted decode key data has been stored and a Session Description Protocol (SDP) file in which the encrypted contents data has been stored is added to the encrypted contents data,

wherein the transmitting step of transmitting the decoding information is a step of transmitting the Session Description Protocol (SDP) file prior to the stream distribution,

wherein the client terminal holds a key set consisting of keys on a path to the route in a key tree consisting of a route key, node keys and leaf keys which are respectively specific to the route, nodes and leaves of a hierarchical tree structure in which plural client terminals are structured as leaves,

wherein the Effective Key Block (EKB) includes data portion in which the encrypted decode key data has been stored, and tag portion for identifying the position of the encrypted decode key data in the hierarchical tree structure, and

wherein the encrypted decode key data can be decoded into the decode key on the basis of information of the tag portion by either one of keys included in a key set of one or more selection client terminals selected from the plural client terminals.

54. The recording medium as set forth in claim 51,

wherein the program includes

a step of receiving streaming distribution data prepared so that additional information including a Session Description Protocol (SDP) file is added to the encrypted contents data, and

a data supplement step of supplementing an Effective Key Block (EKB) in which the encrypted decode key data has been stored and the encrypted contents key data to the Session Description Protocol (SDP) file,

wherein the transmitting step of transmitting the decoding information is a step of transmitting the Session Description Protocol (SDP) file to which the Effective Key Block (EKB) and the encrypted contents key data are supplemented by the data supplement step prior to the stream distribution,

wherein the client terminal holds a key set consisting of keys on a path to the route in a key tree consisting of a route key, node keys and leaf keys which are respectively specific to the route, nodes and leaves of the hierarchical tree structure in which plural client terminals are structured as leaves,

wherein the Effective Key Block (EKB) includes data portion in which the encrypted decode key data has been stored, and tag portion for identifying the position of the encrypted decode key data in the hierarchical structure, and

wherein the encrypted decode key data can be decoded into the decode key on the basis of information of the tag portion by either one of keys included in a key set of one or more selection client terminals selected from plural client terminals.

55. An authoring apparatus including:

file preparation means for adding decoding information for decoding encrypted contents data in which contents data has been encrypted by contents key to the encrypted contents data to prepare stream distribution data used when a stream server performs stream distribution,

wherein the decoding information includes encrypted contents key data in which the contents key has been encrypted.

56. The authoring apparatus as set forth in claim 55,

wherein the decoding information includes encrypted decode key data in which decode key for decoding the encrypted contents data into the contents key has been encrypted.

57. The authoring apparatus as set forth in claim 55,

wherein the stream distribution data includes a Session Description Protocol (SDP) file, and

wherein the decoding information is stored in the Session Description Protocol (SDP) file.

58. The authoring apparatus as set forth in claim 56,

wherein the file preparation means adds additional information including an Effective Key Block (EKB) in which the decoding key data has been stored and a Session Description Protocol (SDP) file in which the encrypted contents key data has been stored to the encrypted contents data to prepare streaming distribution data when the stream server performs stream distribution of contents data utilizable only at one or more selection client terminals selected from plural different client terminals,

wherein the client terminal holds a key set consisting of keys on a path to the route in a key tree consisting of a route key, node keys and leaf keys which are respectively specific to the route, nodes and leaves of the hierarchical tree structure in which plural client terminals are structured as leaves,

wherein the Effective Key Block (EKB) includes data portion in which the encrypted decode key data in which the decode key for decoding the encrypted contents key data has been encrypted has been stored, and tag portion for identifying the position of the encrypted decode key data in the hierarchical tree structure, and

wherein the encrypted decode key data can be decoded into the decode key on the basis of information of the tag portion by either one of keys included in a key set that the selection client terminal has.

59. The authoring apparatus as set forth in claim 58,

wherein the route and the route key are respectively the summit node and the summit node key specific to the summit node when one node of the hierarchical tree structure is the summit.

60. The authoring apparatus as set forth in claim 58,

wherein the decode key is an updated route key or an updated node key in which the route key and/or the node keys of the key set have been updated by decode processing using the Effective Key Block (EKB) by the first decode means.

61. An authoring method including:

a file preparation step of preparing stream distribution data used when a stream server performs stream distribution in the state where decoding information for decoding encrypted contents data in which contents data has been encrypted by contents key is added to the encrypted contents data to prepare stream distribution data used when a stream server performs stream distribution,

wherein the decoding information includes encrypted contents key data in which the contents key has been encrypted.

62. The authoring method as set forth in claim 61,

wherein the decoding information includes encrypted decode key data in which decode key for decoding the encrypted contents key data into the contents key has been encrypted.

63. The authoring method as set forth in claim 61,

wherein the stream distribution data includes a Session Description Protocol (SDP) file, and

wherein the decoding information is stored in the Session Description Protocol (SDP) file.

64. The authoring method as set forth in claim 62,

wherein the file preparation step is a step of adding additional information including an Effective Key Block (EKB) in which decoding key data has been stored and a Session Description Protocol (SDP) file in which the encrypted contents key data has been stored to the encrypted contents data to prepare streaming distribution data used when the stream server performs stream distribution of contents data utilizable at one or more selection client terminals selected from plural different client terminals,

wherein the client terminal holds a key set consisting of keys on a path to the route in a key tree consisting of a route key, node keys and leaf keys which are respectively specific to the route, nodes and leaves of the hierarchical tree structure in which plural client terminals are structured as leaves,

wherein the Effective Key Block (EKB) includes data portion in which the encrypted decode key data has been stored, and tag portion for identifying the position of the encrypted decode key data in the hierarchical tree structure, and

wherein the encrypted decode key data can be decoded into the decode key on the basis of information of the tag portion by either one of keys included in a key set that the selection client terminal has.

65. A program for allowing computer to execute a predetermined operation,

the program including

a file preparation step of adding decoding information for decoding encrypted contents data in which contents data has been encrypted by contents key to the encrypted contents data to prepare stream distribution data used when a stream server performs stream distribution,

wherein the decoding information includes encrypted contents key data in which the contents key has been encrypted.

66. The program as set forth in claim 65,

wherein the decoding information includes encrypted decode key data in which decode key for decoding the encrypted contents key data into the contents key has been encrypted.

67. The program as set forth in claim 65,

wherein the stream distribution data includes a Session Description Protocol (SDP) file, and

wherein the decoding information is stored in the Session Description Protocol (SDP) file.

68. The program as set forth in claim 66,

wherein the file preparation step is a step of adding additional information including an Effective Key Block (EKB) in which decoding key data has been stored and a Session Description Protocol (SDP) file in which the encrypted contents key data has been stored to the encrypted contents data to prepare streaming distribution data used when the stream server performs stream distribution of contents data utilizable only at one selected selection client terminal or terminals selected from plural different client terminals,

wherein the client terminal holds a key set consisting of keys on a path to the route in a key tree consisting of a route key, node keys and leaf keys which are respectively specific to the route, nodes and leaves of the hierarchical tree structure in which plural client terminals are structured as leaves,

wherein the Effective Key Block (EKB) includes data portion in which the encrypted decode key data has been stored, and tag portion for identifying the position of the encrypted decode key data in the hierarchical tree structure, and

wherein the encrypted decode key data can be decoded into the decode key on the basis of information of the tag portion by either one of keys included in a key set that the selection client terminal has.

69. A computer readable recording medium adapted so that program for allowing computer to execute a predetermined operation is recorded,

the program including

a file preparation step of adding decoding information for decoding encrypted contents data in which contents data has been encrypted by contents key to the encrypted contents data to prepare stream distribution data used when a stream server performs stream distribution,

wherein the decoding information includes encrypted contents key data in which the contents key has been encrypted.

70. The recording medium as set forth in claim 69,

wherein the decoding information includes encrypted decode key data in which decode key for decoding the encrypted contents data into the contents key has been encrypted.

71. The recording medium as set forth in claim 69,

wherein the stream distribution data includes a Session Description Protocol (SDP) file, and

wherein the decoding information is stored in the Session description Protocol (SDP) file.

72. The recording medium as set forth in claim 70,

wherein the file preparation step is a step of adding additional information including an Effective Key Block (EKB) in which decoding key data has been stored and a Session Description Protocol (SDP) file in which the encrypted contents data has been stored to the encrypted contents data to prepare streaming distribution data used when the stream server performs stream distribution of contents data utilizable only at one or more selection client terminal selected from plural different client terminals,

wherein the client terminal holds a key set consisting of keys on a path to the route in a key tree consisting of a route key, node keys and leaf keys which are respectively specific to the route, nodes and leaves of the hierarchical tree structure in which plural client terminals are structured as leaves,

wherein the Effective Key Block (EKB) includes data portion in which the encrypted decode key data has been stored, and tag portion for identifying the position of the encrypted decode key data in the hierarchical tree structure, and

wherein the encrypted decode key data can be decoded into the decode key on the basis of information of the tag portion by either one of keys included in a key set that the selection client terminal has.