METHOD FOR PREVENTING LAUNDERING AND REPACKAGING OF MULTIMEDIA CONTENT IN CONTENT DISTRIBUTION SYSTEMS

• US 20110016311A1
• Filed: 04/07/2009
• Published: 01/20/2011
• Est. Priority Date: 04/07/2008
• Status: Active Grant

• Current Assignee: Thomson Licensing (Vantiva SA)
• Original Assignee: Thomson Licensing (Vantiva SA)
• Inventors: Karroumi, Mohamed, Talpin, Yan-Mei Tang, Joye, Marc, Durand, Alain
• Granted Patent: US 9,252,957 B2
• Time in Patent Office: Days
• US Class Current: 713/155
• 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 9/3247 involving digital signatures

Abstract

A method for distributing content in a content distribution system is disclosed which comprises the steps of: encrypting at a Content Packager a content using a content encryption key to generate an encrypted content; sending the content encryption key to a Licensing Authority; receiving from the Licensing Authority a distribution key containing an encryption of the content decryption key (K_c) for a given set of authorized devices; creating a secure link between the content encryption key (K_c) and the content protected by this content encryption key using a signature of the content; and distributing the encrypted content together with the signature of the content. A method for receiving content distributed according to the above-mentioned method in a device able to play back the content is also disclosed where the content signature is checked before any play back of the content.

Claims

1. Method for distributing content in a content distribution system comprising the steps of:

encrypting at a Content Packager a content using a content encryption key (K_c) to generate an encrypted content (C);

sending the content encryption key to a Licensing Authority;

receiving from the Licensing Authority a distribution key containing an encryption of the content decryption key for a given set of authorized devices;

creating a secure link between the content encryption key and the content protected by this content encryption key using a signature of the content; and

distributing the encrypted content together with at least a part of the signature of the content;

wherein the content signature is generated by signing at the Content Packager the content and;

wherein the content signature is used to compute the content encryption key.

5. Method according to claim 1, wherein a part of the content signature is distributed in an encrypted form, in the distribution key, with the encrypted content.

8. Method according to claim 1 further comprising the steps of:

generating at the Content Packager a set of hierarchical keys K₁, . . . , K_i;

encrypting at the Content Packager the content encryption key using the first key K₁ in the set of hierarchical keys;

encrypting each key K_n, with n between 1 and i−

1, of the set of hierarchical keys with the subsequent key K_n+1 in the set of hierarchical keys;

sending to the Licensing Authority, instead of the content encryption key, the last key K_i of the set of hierarchical keys;

wherein the distribution key received from the Licensing Authority contains an encryption of the last key K_i for a given set of authorized devices;

and wherein the first key K₁ is generated by signing, at the Content Packager, the content encryption key and each key K_m, with m between 2 and i, of the set of hierarchical keys, is generated by signing, at the Content Packager, the preceding key K<sub>m−

1</sub> in the set of hierarchical keys.

9. Method according to claim 1, wherein the step of receiving, from the Licensing Authority, the distribution key further comprises the reception of a signature of said distribution key generated by the Licensing Authority.

10. Method for receiving content distributed according to the method of claim 9 in a device able to play back the content comprising the steps of:

verifying the content signature distributed with the content using a verification key of the Content Packager received with the distribution key; and

if the verification succeeds, obtaining from the distribution key the content encryption key using a device decryption key stored in said device and decrypting the content using the obtained content encryption key to play back the content.

11. Method according to claim 10 further comprising a step of:

verifying the signature of the distribution key using a verification key of the Licensing Authority stored in said device; and

performing the subsequent steps of the method according to claim 10 only if said verification of the signature of the distribution key succeeds.

12. Method according to claim 1, wherein another part of the content signature is distributed in clear with the encrypted content.

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