System and method for preventing an illegal copy of contents

• US 7,095,853 B2
• Filed: 02/22/2001
• Issued: 08/22/2006
• Est. Priority Date: 02/24/2000
• Status: Expired due to Fees

• Current Assignee: RPX Corporation
• Original Assignee: NEC Corporation
• Inventors: Morishita, Takuya
• Primary Examiner(s): Zand, Kambiz
• Application Number:
  US09/792,194
• Publication Number:
  US 20010018743A1
• Time in Patent Office: 2,007 Days
• Field of Search: 380/201, 705/57, 713/200, 713/201
• US Class Current: 380/201
• CPC Class Codes: G06F 12/1408 by using cryptography for digital transmission H04L9/00
• 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 20/00557 wherein further management data is encrypted, e.g. sector headers, TOC or the lead-in or lead-out areas

Abstract

The method of preventing illegal copy of contents encrypts a header using a key generated from the previous sector, performs variable-length coding to the encrypted header to shorten its length, and stores the decoded header into the recording medium as well as contents data, in encryption phase. The method, in decryption phase, reproduces the contents data which have different length for each sector by decoding and encoding the header.

Claims

1. A method of preventing an illegal copy of contents stored in a recording medium in each sector of a fixed-length, each sector including a header and contents data, comprising the steps of:

encrypting at least a part of data to be stored as encrypted data in the sector, using a key generated based on data other than the data stored in the sector; and

variable-length coding only a part of the encrypted data to store the coded data into each sector of the recording medium;

wherein the decoded variable-length coded data is larger than corresponding coded data.

2. The method of claim 1, wherein the encrypting step and the variable-length coding step are performed for the header.

3. The method of claim 1, wherein the key is a part of the encrypted data in the previous sector or a hash value.

4. A recording medium readable by a computer, including sectors each of which comprises a header and contents data, at least a part of data stored in the sector being encrypted using a key generated based on data other than the data stored in the sector, only a part of the encrypted data being further variable-length coded;

wherein illegal copying of said sector is prevented;

wherein the decoded variable-length coded data is larger than corresponding coded data.

5. The recording medium of claim 4, wherein the encrypting and the variable-length coding are performed for the header.

6. The recording medium of claim 4, wherein the key is a part of the encrypted data in the previous sector or a hash value.

7. A system for preventing illegal copy of contents stored in a recording medium in a unit of fixed-length sector, each sector including a header and contents data, comprising an encryption device and a decryption device, wherein the encryption device includes:

an encryption key generator which generates an encryption key used to encrypt the header;

a header encryption unit which encrypts the header using the encryption key;

a variable-length coding unit which performs variable-length coding process to the encrypted header and changes the length of the encrypted header, and

a contents data encryption unit which encrypts the contents data, and

the decryption device includes;

a decryption key generator which generates a decryption key used to decrypt the header;

a header decryption unit which decrypts the header using the decryption key;

a variable-length decoding unit which performs variable-length decoding process to the decrypted header, wherein the decoded and decrypted header is longer than the header; and

a contents decryption unit which decrypts the contents.

8. An encryption device for preventing illegal copy of contents stored in a recording medium in a unit of fixed-length sector, each sector including a header and contents data, comprising:

an encryption key generator which generates an encryption key used to encrypt the header;

a header encryption unit which encrypts the header using the encryption key;

a variable-length coding unit which performs variable-length coding process to the encrypted header and changes the length of the header; and

a contents data encryption unit which encrypts the contents data;

wherein the decoded variable-length coded data is larger than corresponding coded data.

9. A decryption device for preventing illegal copy of contents stored in a recording medium in a unit of fixed-length sector, each sector including an encrypted header and encrypted contents data, comprising:

a decryption key generator which generates a decryption key used to decrypt the encrypted header;

a header decryption unit which decrypts the encrypted header using the decryption key;

a variable-length decoding unit which performs variable-length decoding process to the decrypted header; and

a contents decryption unit which decrypts the encrypted contents;

wherein a length of the decoded and decrypted header and decrypted contents is greater than the unit of fixed length sector.

10. A recording medium readable by a computer tangibly embodying a program of instructions executable by the computer to perform a method of preventing illegal copy of contents stored in a recording medium in a unit of fixed-length sector, each sector including a header and contents data, the method comprising the steps of:

encrypting at least a part of data to be stored in the sector, using a key generated based on data other than the data stored in the sector; and

variable-length coding only a part of the encrypted data and storing the coded data into the recording medium;

wherein the decoded variable-length coded data is larger than corresponding coded data.

11. A program product comprising, computer readable instructions and a recording medium bearing the computer readable instructions;

the instructions being adaptable to enable a computer to perform a method of preventing illegal copy of contents stored in a recording medium in a unit of fixed-length sector, each sector including a header and contents data, the method comprising the steps of;

encrypting at least a part of data to be stored in the sector, using a key generated based on data other than the data stored in the sector; and

variable-length coding only a part of the encrypted data and storing the coded data into the recording medium;

wherein the decoded variable-length coded data is larger than corresponding coded data.