Copy protection method and system for digital media

• US 20020169973A1
• Filed: 05/01/2002
• Published: 11/14/2002
• Est. Priority Date: 05/11/2001
• Status: Active Grant

• Current Assignee: LG Electronics, Inc. (LG Corporation)
• Original Assignee: LG Electronics, Inc. (LG Corporation)
• Inventors: Um, Soung Hyun, Stechkine, Alexandre, Kim, Byung Jin, Kim, Hyung Sun
• Granted Patent: US 7,254,838 B2
• Time in Patent Office: Days
• US Class Current: 713/193
• 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 21/6209 to a single file or object, e.g. in a secure envelope, encrypted and accessed using a key, or with access control rules appended to the object itself
• CPC Class Codes: G06F 2221/2107 File encryption
• CPC Class Codes: H04L 2209/605 Copy protection
• CPC Class Codes: H04L 9/0822 using key encryption key
• CPC Class Codes: H04L 9/0825 using asymmetric-key encryption or public key infrastructure [PKI], e.g. key signature or public key certificates
• CPC Class Codes: H04L 9/0891 Revocation or update of secret information, e.g. encryption key update or rekeying
• CPC Class Codes: H04L 9/3263 involving certificates, e.g. public key certificate [PKC] or attribute certificate [AC]; Public key infrastructure [PKI] arrangements network architectures or network communication protocols for supporting authentication of entities using certificates in a packet data network H04L63/0823

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 corresponding to the private key identification, an intermediate key decryptor receiving an encrypted intermediate key and decrypting the intermediate key with the actual private key, a media key decryptor obtaining an original media key by decrypting the decrypted intermediate key with a media identification; and a media data decryptor receiving an encrypted media data set and decrypting the media data set with the original 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 symmetric algorithm corresponding to an original media key;

(b) generating an intermediate key by encrypting said original media key with a media identification;

(c) encrypting said intermediate key with a public key of a compliant playing device;

(d) delivering said encrypted media data set, said encrypted intermediate key, and a media certificate to said playing device, said certificate including a private key identification of said playing device;

(e) searching for an actual private key corresponding to said private key identification;

(f) decrypting said delivered intermediate key with said actual private key;

(g) obtaining said original media key by decrypting said decrypted intermediate key with said media identification; and

(h) decrypting said delivered media data set with said obtained media key.

2. The method of claim 1, wherein said actual private key is searched by checking whether each of available private keys stored in said playing device corresponds to said private key identification.

3. The method of claim 2, 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.

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

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

6. 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 corresponding to said private key identification;

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

a media key decryptor obtaining an original media key by decrypting said decrypted intermediate key with a media identification; and

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

7. The system of claim 6, wherein said actual private key is searched by checking whether each of available private keys stored in said playing device corresponds to said private key identification.

8. The system of claim 7, 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.

9. The system of claim 8, further comprising a data-rewritable memory storing said one or more old private keys.

10. The system of claim 9, where said old private keys being stored in said memory are encrypted with a public key of said playing device.

11. The system of claim 6, wherein said encrypted intermediate key is initially encrypted with a public key of said playing device.

12. The system of claim 6, wherein said encrypted media data set is initially encrypted with said original media key.