Data protection system that protects data by encrypting the data

• US 7,395,425 B2
• Filed: 03/28/2002
• Issued: 07/01/2008
• Est. Priority Date: 03/29/2001
• Status: Active Grant

• Current Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Nakano, Toshihisa, Tatebayashi, Makoto, Ohmori, Motoji, Matsuzaki, Natsume
• Primary Examiner(s): Moazzami; Nasser
• Assistant Examiner(s): Okoronkwo; Chinwendu C
• Application Number:
  US10/297,089
• Publication Number:
  US 20030182565A1
• Time in Patent Office: 2,287 Days
• Field of Search: 713/163, 726 16- 21
• US Class Current: 713/163
• CPC Class Codes: G06F 21/10 Protecting distributed programs or content, e.g. vending or licensing of copyrighted material protection in video systems or pay television H04N7/16 ; Digital rights management [DRM]
• CPC Class Codes: G06F 2221/2107 File encryption
• CPC Class Codes: G11B 20/00086 Circuits for prevention of unauthorised reproduction or copying, e.g. piracy indicating unauthorised use of record carriers in general G11B23/28; scrambling for television signal recording H04N5/913; network architectures or network protocols for network security H04L63/00; cryptographic mechanisms or cryptographic arrangements for secret or secure communication H04L9/00
• CPC Class Codes: G11B 20/0021 involving encryption or decryption of contents recorded on or reproduced from a record carrier
• CPC Class Codes: H04L 2209/60 Digital content management, e.g. content distribution
• CPC Class Codes: H04L 2209/80 Wireless network architectures or network communication protocols for wireless network security H04W12/00
• CPC Class Codes: H04L 2463/101 applying security measures for digital rights management data processing systems or methods, specially adapted for commerce, e.g. marketing, shopping, billing, auctions or e-commerce G06Q30/00
• 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 9/08 Key distribution or management, e.g. generation, sharing or updating, of cryptographic keys or passwords network architectures or network communication protocols for supporting key management in a packet data network H04L63/06
• 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
• CPC Class Codes: H04N 2005/91364 the video signal being scrambled
• CPC Class Codes: H04N 21/2347 involving video stream encryption
• 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 21/4325 by playing back content from the storage medium reproduction of recorded television signals H04N5/76; reproduction of recorded television signals H04N9/79
• CPC Class Codes: H04N 21/4405 involving video stream decryption
• CPC Class Codes: H04N 5/913 for scrambling ; for copy protection
• 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 data protection system is provided that reduces, to a degree, the amount of encrypted data that is distributed to a plurality of terminals. In the data protection system a terminal whose decryption keys are exposed by a dishonest party is made to be unable to decrypt the data correctly, while other terminals are able to decrypt the data correctly.

The data protection system includes a plurality of terminals, and an encryption device that encrypts distribution data distributed to each terminal. Each terminal is corresponded with one node on a lowest level of a 4-ary tree structure or the like having a plurality of hierarchies. The data protection system, for each node in the tree structure, excluding those on the lowest level, determines a plurality of combination patterns that include combinations of two or more of all four nodes that are reached one level below the node, decides an individual decryption key for each determined combination pattern, and decides an individual decryption key for each node on the lowest level. Further, the data protection system has each terminal store all decryption keys decided for the nodes on the path from the node on the lowest level that corresponds to the terminal through to the node on the highest level. The data protection system prescribes nodes that are reached from the node on the lowest level that corresponds to the terminal through to the node on the highest level that correspond to a terminal that has been dishonestly analyzed as invalid nodes. For invalid nodes, other than invalid nodes on the lowest level, the data protection system designates an encryption key that corresponds to the decryption key decided in correspondence with the combination pattern that combines all nodes, excluding invalid nodes, of the four nodes that are reached one level below the node, and has the encryption device encrypt distribution data that uses each of the designated encryption keys.

Claims

1. A data protection system that comprises three or more terminals, an encryption device, and an encryption key designation device, and that protects distribution data that is to be distributed to said terminals, according to said encryption device encrypting the distribution data, wherein:

each terminal is operable to

(i) store a decryption key group assigned individually to the terminal, respectively, according to

(a) a determination of two or more terminal groups, which are groups having two or more terminals as members, so that each of the terminals is a member of at least one of the terminal groups, and so that any one of the terminal groups that shares a same terminal as a member with another one of the terminal groups does not completely include the other one of the terminal groups sharing the same terminal as a member and is not completely included in the other one of the terminal groups sharing the same terminal as a member,

(b) a decision of one or more decryption keys individually in correspondence with each terminal and each determined terminal group, and

(c) an assignment, to each terminal, the decryption key group, where the decryption key group is based on the decryption key decided in correspondence with the terminal, and decryption keys decided in correspondence with all terminal groups that include the terminal, respectively;

(ii) obtain an encrypted distribution data group that has been output from said encryption device, and

(iii) use a stored decryption key to decrypt encrypted distribution data;

said encryption key designation device is operable to designate encryption keys, and includes;

an invalid terminal designation unit for designating one or more terminals as invalid terminals; and

an encryption key designation unit for designating, when all the decryption keys assigned to the terminals, other than decryption keys assigned to the one or more invalid terminals, are prescribed as valid decryption keys, and when a procedure for selecting an assigned valid decryption key for the most terminals not designated as invalid terminals is repeated until all terminals not designated as invalid terminals have been assigned a selected valid decryption key, encryption keys that respectively correspond to each of the valid decryption keys that are selected as a result of the procedure; and

said encryption device includes an encryption unit for encrypting distribution data by successively using all the designated encryption keys to encrypt distribution data, generating the encrypted distribution data group, and outputting the generated encrypted distribution data group.

2. The data protection system of claim 1, wherein:

said encryption unit is operable to output the generated encrypted distribution data group to be recorded on at least one data recording medium; and

each terminal is operable to read the encrypted distribution data from one of the at least one data recording medium, and decrypt the encrypted distribution data.

3. The data protection system of claim 2, wherein:

said encryption device includes

a content storage unit for storing content data that is a digital work,

a random number generation unit for generating the distribution data that is a random number, and

a content encryption unit for encrypting the content data, by using the generated distribution data as a key, so as to generate encrypted content data;

said encryption device is operable to generate an encrypted distribution data group by encrypting the generated distribution data successively by using each of the encryption keys designated by said encryption key designation device, and record the encrypted distribution data group and the generated encrypted content on the at least one data recording medium; and

each terminal is operable to read the encrypted content and the encrypted distribution data group from one of the at least one recording medium, decrypt the encrypted distribution data, and use the resulting distribution data to decrypt the encrypted content data.

4. The data protection system of claim 2, further comprising an encryption key designation information recording device for recording encryption key designation information that designates the encryption key designated by said encryption key designation device, wherein:

each terminal includes

a random number generation unit for generating the distribution data that is a random number,

a content storage unit for storing content data that is a digital work, and

an encryption key selection unit for reading the encryption key designation information from the at least one data recording medium, and selecting the encryption key designated by the encryption key designation information, from among the encryption key group that corresponds to the decryption key group stored by the terminal; and

said encryption unit is operable to encrypt distribution data by successively using all the encryption keys designated by the encryption keys designated by said encryption designation device so as to generate an encrypted distribution data group, and output the generated encrypted distribution data group.

5. The data protection system of claim 1, wherein:

said encryption unit is operable to transmit the generated encrypted distribution data group to each terminal; and

each terminal is operable to receive the transmitted encrypted distribution data group and decrypt the received encrypted distribution data group.

6. The data protection system of claim 1, wherein said each terminal is operable to store the decryption key group which is assigned individually to the terminal also according to an assignment, to each terminal, of the decryption key decided in correspondence with the terminal and all decryption keys decided in correspondence with all terminal groups that include the terminal.

7. The data protection system of claim 6, wherein said each terminal is operable to store the decryption key group which is assigned individually to the terminal also according to a determination of terminal groups so that at least one terminal group exists that completely includes the two or more terminal groups, and so that any one of the terminal groups within the two or more terminal groups that shares a same terminal group as a member with another one of the terminal groups does not completely include the other one of the terminal groups that shares the same terminal group as a member and is not completely included in the other one of the terminal groups that shares the same terminal group as a member.

8. The data protection system of claim 7, wherein said each terminal is operable to store the decryption key group which is assigned individually to the terminal also according to a determination of the terminal groups so that each terminal group includes three or more terminals as members, and so that a terminal group exists that contains three or more terminal groups.

9. The data protection system of claim 8, further comprising:

a key storage device for, when each terminal is corresponded with a node on a lowest level in an N-ary tree structure having a plurality of hierarchies, where N is a natural number equal to or greater than three,

determining, for each node other than the nodes on the lowest level, a plurality of combination patterns, for each one of N nodes that are reached from the each node constituting a parent node of the one of the N nodes, that are combinations of two or more of the N nodes including the one of the N nodes, and that include a combination of all of the N nodes,

deciding an individual decryption key for each determined combination pattern and storing each decided decryption key in correspondence with the parent node, and

further stores an individual decryption key in correspondence with each node in the lowest level; and

a decryption key determining device for

(i) executing

(a) the determination of the two or more terminal groups,

(b) the decision of the one or more decryption keys individually in correspondence with each terminal and each determined terminal group, and

(c) the assignment of the decryption key group to each terminal,

(ii) determining the decryption key group that is assigned to each terminal, and

(iii) determining decryption keys to be assigned to each terminal, the decryption keys being (a) decryption keys selected from among the decryption keys stored in said key storage device in correspondence with each node on a same path, which is a path from the node corresponding to the terminal on the lowest level to a node on the highest level, excluding the node that corresponds to the terminal, and corresponding with all of the combination patterns that include a node that is one level below the each node on the same path, and (b) the decryption key stored in said key storage device in correspondence with the terminal;

wherein the terminal groups have a one-to-one correspondence with the combination patterns, and each terminal group is a group whose members are all the terminals that correspond to all nodes on the lowest level that are reached from all the combined nodes in the corresponding combination pattern;

wherein said encryption key designation unit, for the N-ary tree structure, prescribes all nodes from which a node on the lowest level of the N-ary tree structure that corresponds to an invalid terminal is reached as invalid nodes, performs encryption key designation processing first with a node on the highest level as a processing target node, and repeatedly performs the encryption key designation processing until all processing target nodes have been processed; and

wherein said encryption key designation unit is operable to perform the encryption key designation processing on one processing target node at a time that has not been processed, and is processing that

(i) when a combination pattern exists that relates to a combination that includes all nodes, other than invalid nodes, one level below the processing target node, designates an encryption key that corresponds to the decryption key stored by said key storage device in correspondence with the combination pattern, and if one or more invalid nodes exists one level below the processing target node and the one level below the processing target node is not the lowest level, newly makes all of the one or more invalid nodes that are one level below the processing target node processing target nodes, and

(ii) when a combination pattern does not exist that relates to a combination including all nodes, other than invalid nodes, one level below the processing target node, designates encryption keys stored in correspondence with all the nodes, other than the invalid nodes, by said key storage device in the level one level below if one level below is the lowest level, and if one level below is not the lowest level, newly makes all the nodes that are one level below the processing target node processing target nodes.

10. The data protection system of claim 9, wherein said key storage device is operable to perform the determination of the plurality of combination patterns for each node excluding the nodes on the lowest level in the N-ary tree structure by prescribing combination patterns so that each combination pattern corresponds to one of all combinations of two or more of the N nodes that are one level below and are reached from the each node constituting a parent node of the two or more of the N nodes, and said key storage device is operable to store the determined decryption keys in correspondence with the parent node.

11. The data protection system of claim 9, wherein said key storage device is operable to perform the determination of the plurality of combination patterns for each node excluding the nodes on the lowest level for the N-ary tree structure by prescribing combination patterns so that each combination pattern corresponds to one of all combinations of all N of the nodes and N−

1 of the N nodes that are one level below and are reached from the each node constituting a parent node of the N nodes, and said key storage device is operable to store the determined decryption keys in correspondence with the parent node.

12. The data protection system of claim 9, wherein:

said encryption unit is operable to output in correspondence, for each encryption key designated by said encryption key designation device, encrypted distribution data that is generated by encrypting data by using the designated encryption key, and encryption key node identification information for designating a position in the tree structure of the node that is corresponded by said key storage device with the decryption key corresponding to the encryption key; and

each terminal is operable to store the decryption key that has been individually assigned to the terminal, respectively, according to

(i) the determination of the two or more terminal groups,

(ii) the decision of the one or more decryption keys individually in correspondence with each terminal and each determined terminal group, and

(iii) the assignment of the decryption key group to each terminal, in correspondence with decryption key node identifying information of the node with which the decryption key is corresponded, obtain the encrypted distribution data group and an encryption key node identification information group, and decrypt the encrypted distribution data that corresponds to encryption key node identification information that matches the decryption key node identification information stored by the terminal, by using the decryption key that corresponds with the decryption key node identification information.

13. The data protection system of claim 9, wherein:

said encryption key designation device includes a key storage device for storing the corresponding encryption key of each decryption key that is stored by said key storage device; and

the corresponding encryption key and decryption key stored by said key storage unit are different from each other.

14. A method of using a data protection system that comprises three or more terminals, an encryption device, and an encryption key designation device, to protect distribution data that is to be distributed to said terminals, according to said encryption device encrypting the distribution data, said method comprising:

using each terminal to

(i) store a decryption key group assigned individually to the terminal, respectively, according to

(a) a determination of two or more terminal groups, which are groups having two or more terminals as members, so that each of the terminals is a member of at least one of the terminal groups, and so that any one of the terminal groups that shares a same terminal as a member with another one of the terminal groups does not completely include the other one of the terminal groups sharing the same terminal as a member and is not completely included in the other one of the terminal groups sharing the same terminal as a member,

(b) a decision of one or more decryption keys individually in correspondence with each terminal and each determined terminal group, and

(c) an assignment, to each terminal, the decryption key group, where the decryption key group is based on the decryption key decided in correspondence with the terminal, and decryption keys decided in correspondence with all terminal groups that include the terminal, respectively;

(ii) obtain an encrypted distribution data group that has been output from said encryption device, and

(iii) use a stored decryption key to decrypt encrypted distribution data;

using said encryption key designation device to designate encryption keys by

(i) using an invalid terminal designation unit of said encryption key designation device to designate one or more terminals as invalid terminals, and

(ii) using an encryption key designation unit of said encryption key designation device to designate, when all the decryption keys assigned to the terminals, other than decryption keys assigned to the one or more invalid terminals, are prescribed as valid decryption keys, and when a procedure for selecting an assigned valid decryption key for the most terminals not designated as invalid terminals is repeated until all terminals not designated as invalid terminals have been assigned a selected valid decryption key, encryption keys that respectively correspond to each of the valid decryption keys that are selected as a result of the procedure; and

using an encryption unit of said encryption device to encrypt distribution data by successively using all the designated encryption keys to encrypt distribution data, generating the encrypted distribution data group, and outputting the generated encrypted distribution data group.