Method for ensuring content protection and subscription compliance

• US 7,523,307 B2
• Filed: 01/08/2002
• Issued: 04/21/2009
• Est. Priority Date: 01/26/2001
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Lotspiech, Jeffrey Bruce, Pestoni, Florian, Naor, Dalit, Nin, Sigfredo Ismael
• Primary Examiner(s): Zand; Kambiz
• Assistant Examiner(s): Wyszynski; Aubrey H
• Application Number:
  US10/042,652
• Publication Number:
  US 20020104001A1
• Time in Patent Office: 2,660 Days
• Field of Search: 713/158, 713/163
• US Class Current: 713/163
• CPC Class Codes: G11B 20/0021 involving encryption or decryption of contents recorded on or reproduced from a record carrier
• CPC Class Codes: H04L 12/18 for broadcast or conference , e.g. multicast
• CPC Class Codes: H04L 2209/605 Copy protection
• CPC Class Codes: H04L 2209/606 Traitor tracing
• CPC Class Codes: H04L 63/0428 wherein the data content is protected, e.g. by encrypting or encapsulating the payload
• 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

A method for enforcing compliance in both the copy protect domain and service subscription domain for streamed multicast data. Each content is encrypted with a title key that itself is encrypted with a channel unique key which is a hash of a session key and a channel key. A compliant player is given the channel key upon registration for a subscription service (representing subscription protection) and is also given device keys upon activation (representing copy protection) for decrypting the session key. Consequently, the channel unique key can be obtained (and, hence, the content decrypted) only by a player that is compliant with both copy protection rules and subscription rules. The channel key can be refreshed periodically as subscriptions change or expire.

Claims

1. A computer-implemented method for securely transmitting multicast data, comprising:

encrypting at least one title T with at least title key K_T; and

encrypting the title key K_T with at least one channel-unique key K_cu using at least one encryption function S to render a multicast data channel encrypted as S_Kcu(K_T), S_KT(T), wherein the channel-unique key K_cu is the result of a combination of a channel key K_c and a session key K_s, wherein the session key K_s is encrypted with at least a first encryption scheme B^R_s1 to render a session key block, further comprising providing at least one player with device keys K_d to activate the player and providing the player with the channel key K_c and the session key block, wherein the player can determine the session key K_s from the session key block using the device keys K_d further comprising periodically refreshing the channel key K_c to enforce subscriptions, wherein a new channel key K_c′

is encrypted with at least a second encryption scheme B^R_s2 and wherein the encryption scheme B^R_s2 includes;

assigning each player in a group of players respective private information I_u;

partitioning players not in a revoked set R into disjoint subsets S_i1, . . . S_im having associated subset keys L_i1, . . . L_im; and

encrypting the session key K_s with the subset keys L_i1, . . . L_im to render m encrypted versions of the session key K_s.

2. The method of claim 1, wherein the combination is a hash function of a concatenation of the channel key_c and session key K_s.

3. The method of claim 1, wherein at least one of the providing acts is undertaken in a point-to-point communication.

4. The method of claim 1, wherein at least one of the providing acts is undertaken as part of a broadcast.

5. The method of claim 1, comprising selectively updating the session key block.

6. The method of claim 5, comprising updating the session key block by encrypting an updated session key with at least the encryption scheme B^R_s1.

7. The method of claim 1, wherein the new channel key K_c′

is sent in a message that is split.

8. The method of claim 1, wherein the new channel key K_c′

is refreshed using plural messages.

9. The method of claim 1, wherein the encryption scheme B^R_s2 further includes partitioning the players into groups S₁, . . . ,S_w, wherein “

w”

is an integer, and the groups establish subtrees in a tree.

10. The method of claim 9, wherein the tree includes a root and plural nodes, each node having at least one associated label, and wherein each subset includes all leaves in a subtree rooted at some node v_i that are not in the subtree rooted at some other node v_j that descends from v_i.

11. The method of claim 10, wherein the revoked set R defines a spanning tree, and wherein the method includes:

initializing a cover tree T as the spanning tree;

iteratively removing nodes from the cover tree T and adding nodes to a cover until the cover tree T has at most one node.

12. The method of claim 10, wherein each node has at least one label possibly induced by at least one of its ancestors, and wherein each player is assigned labels from all nodes hanging from a direct path between the player and the root but not from nodes in the direct path.

13. The method of claim 12, wherein labels are assigned to subsets using a pseudorandom sequence generator, and the act of decrypting includes evaluating the pseudorandom sequence generator.