Copy protection method and system for digital media

• US 20020118838A1
• Filed: 02/04/2002
• Published: 08/29/2002
• Est. Priority Date: 02/05/2001
• Status: Active Grant

• Current Assignee: LG Electronics, Inc. (LG Corporation)
• Original Assignee: LG Electronics, Inc. (LG Corporation)
• Inventors: Kuzmich, Vsevolod M., Belenko, Vyacheslav S.
• Granted Patent: US 7,509,682 B2
• Time in Patent Office: Days
• US Class Current: 380/277
• 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: G11B 20/00362 the key being obtained from a media key block [MKB]
• CPC Class Codes: G11B 20/00478 wherein contents are decrypted and re-encrypted with a different key when being copied from/to a record carrier
• CPC Class Codes: H04L 2209/605 Copy protection
• CPC Class Codes: H04L 9/0891 Revocation or update of secret information, e.g. encryption key update or rekeying

Abstract

A copy protection method and a copy protection system. are disclosed. The system includes a private key verifier receiving a media certificate that includes a private-key identification of a compliant playing device and searching for an actual private key by checking whether each of available private keys of the playing device corresponds to the private-key identification, a media key decryptor receiving an encrypted media key and decrypting the media key with the actual private key, and, a media data decryptor receiving an encrypted media data set and decrypting the media data set with the decrypted media key. The method and system of the present invention are applicable to all types of digital media data, and it makes no assumption of any specific media properties. The primary goal of the present invention is to significantly reduce the possibility of making any illegal copies on any nonstandard equipment and is to restrict the media data transfers only to authorized entities.

Claims

1. A copy protection method for digital media, the method comprising the steps of:

(a) encrypting an original media data set with a media key corresponding to a symmetric algorithm and encrypting said media key with a public key of a compliant playing device;

(b) delivering said media data set and media key encrypted in the step (a) and a media certificate to said playing device, said certificate including a private-key identification of said playing device, said private-key identification being encrypted with said public key;

(c) decrypting said private-key identification;

(d) searching for an actual private key by checking whether each of stored private keys of said playing device corresponds to said decrypted private-key identification;

(e) decrypting said delivered media key with said actual private key; and

(f) decrypting said delivered ;

media data set with said decrypted media key.

2. The method of claim 1, wherein said stored, private keys include a current private key and one or more old private keys, each of said old private keys being previously revoked through a key revocation process.

3. The method of claim 2, wherein said playing device includes a rewritable memory storing said old private keys.

4. The method of claim 3, wherein said older private keys being stored in said memory are encrypted with said public key.

5. A copy protection system for digital media, the system comprising:

a private key verifier receiving a media certificate that includes a private-key identification of a compliant playing device and searching for an actual private key by checking whether each of available private keys of said playing device corresponds to said private-key identification;

a media key decryptor receiving an encrypted media key and decrypting said media key with said actual private key; and

a media data decryptor receiving an encrypted media data set and decrypting said media data set with said decrypted media key.

6. The system of claim 5, wherein said available private keys include a current private key and one or more old, private keys, each of said old private keys being previously revoked through a key revocation process.

7. The system of claim 6, further comprising a data-rewritable memory storing said one or more old private keys.

8. The system of claim 7, where said older private keys being stored in said memory are encrypted with a public key of said playing device.

9. The system of claim 5, wherein said encrypted media key is encrypted with a public key of said playing device.

10. The system of claim 5, wherein said encrypted media data set is encrypted with an original media key.