Copy protection for optical discs

• US 6,532,201 B1
• Filed: 04/03/2000
• Issued: 03/11/2003
• Est. Priority Date: 04/03/2000
• Status: Expired due to Fees

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Hewlett-Packard Company (HP Inc.)
• Inventors: Hogan, Josh
• Primary Examiner(s): Tran, Thang V.
• Assistant Examiner(s): LE, KIMLIEN T
• Application Number:
  US09/542,679
• Time in Patent Office: 1,072 Days
• Field of Search: 369/47.28, 369/47.3, 369/47.37, 369/53.15, 369/53.21, 369/53.22, 369/53.29, 369/53.35, 369/53.36, 369/272, 714/54, 380/200, 380/201, 380/202, 380/203
• US Class Current: 369/53.21
• 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 20/00449 content scrambling system [CSS]
• CPC Class Codes: G11B 20/00579 said format change concerning the data encoding, e.g., modulation schemes violating run-length constraints, causing excessive DC content, or involving uncommon codewords or sync patterns
• CPC Class Codes: G11B 20/00586 said format change concerning the physical format of the recording medium
• CPC Class Codes: G11B 20/00927 wherein said defects or errors are generated on purpose, e.g. intended scratches
• CPC Class Codes: G11B 23/281 by changing the physical properties of the record carrier
• CPC Class Codes: G11B 7/24082 Meandering

Abstract

An optical disc has spatial features (notches, bumps, etc.) that intentionally cause read errors if arbitrary data is recorded on the disc in an area where the special features are located. The spatial features are located such that they occur in the center of longer marks or spaces of pre-determined data patterns. This allows pre-determined data patterns to be written and read without a significant number of errors, while arbitrary data patterns will be subject to a significant number of errors, rendering the arbitrary data unreadable. Control Data ECC blocks are partially pre-determined at least in the areas containing decryption keys, while still permitting some arbitrary data to be written in other areas of the Control Data ECC blocks. Therefore, compatibility with existing drives is preserved, without representing a threat of unauthorized copying of stamped discs.

Claims

1. A method of preventing arbitrary data from being read with a correctable error rate from an optical disc, comprising:

forming spatial features on the optical disc;

locating the spatial features on the optical disc so that when pre-determined data is written, the pre-determined data is aligned with the spatial features and a read error rate is sufficiently low to be correctable, and when data other than the pre-determined data is written, the data other than the pre-determined data is not aligned with the spatial features and a read error rate is too high to be correctable.

2. The method of claim 1, wherein the step of forming spatial features further comprises:

increasing a width of a groove on the optical disc, wherein a distance, tangential to a groove center line, along which the width of the groove is increased, is less than a spatial length of a data mark.

3. The method of claim 1, wherein the step of forming spatial features further comprises:

decreasing a width of a groove on the optical disc, wherein a distance, tangential to a groove center line, along which the width of the groove is decreased, is less than a spatial length of a data mark.

4. The method of claim 1, wherein the step of locating the spatial features further comprises:

locating the spatial features in an area reserved for decryption keys.

5. The method of claim 1, further comprising:

selecting the pre-determined data, so that substantially all bytes, in at least one column of bytes in an error correction block, contain at least some marks and spaces that are substantially longer than the length of the spatial features.

6. The method of claim 1, further comprising:

selecting the pre-determined data to be all binary zeros, before encoding.

7. A method of preventing arbitrary data from being read with correctable error rate from an optical disc, comprising:

forming spatial features on the optical disc, wherein when a transition between a mark and a space is not near one of the spatial features, no read error results when the disc is read by a drive, and wherein when a transition between a mark and a space is near one of the spatial features, a read error results when the disc is read by a drive; and

locating the spatial features on the optical disc so that when pre-determined data is written, transitions between marks and spaces are not near the spatial features, and when data other than the pre-determined data is written onto the optical disc, at least some transitions between marks and spaces are near the spatial features.

8. The method of claim 7, wherein the step of forming spatial features further comprises:

increasing a width of a groove on the optical disc, wherein a distance, tangential to a groove center line, along which the width of the groove is increased, is less than a spatial length of a data mark.

9. The method of claim 7, wherein the step of forming spatial features further comprises:

decreasing a width of a groove on the optical disc, wherein a distance, tangential to a groove center line, along which the width of the groove is decreased, is less than a spatial length of a data mark.

10. The method of claim 7, wherein the step of locating the spatial features further comprises:

locating the spatial features in an area reserved for decryption keys.

11. The method of claim 7, further comprising:

selecting the pre-determined data, so that substantially all bytes, in at least one column of bytes in an error correction block, contain at least some marks and spaces that are substantially longer than the length of the spatial features.

12. The method of claim 7, further comprising:

selecting the pre-determined data to be all binary zeros, before encoding.

13. An optical disc comprising:

a spatial feature, the spatial feature located in an area of the optical disc reserved for data for a decryption key;

wherein when a mark is spatially centered relative to the spatial feature, and the mark is read in a compatible disc drive, a resulting binary read data signal is not affected; and

wherein when the mark is positioned so that an end of the mark is adjacent to the spatial feature, and the mark is read in a compatible disc drive, a resulting binary read data signal is affected.

14. The optical disc of claim 13, further comprising:

a groove, the mark written in the groove.

15. The optical disc of claim 14, further comprising:

the spatial feature comprising an increase in a radial width of the groove, with a distance, tangential to a groove center line, along which the width of the groove is increased, being less than a spatial length of the mark.

16. The optical disc of claim 14, further comprising:

the spatial feature comprising a decrease in a radial width of the groove, with a distance, tangential to a groove center line, along which the width of the groove is decreased, being less than a spatial length of the mark.

17. An optical disc comprising:

a spatial feature, located in an area of the disc reserved for data for a decryption key;

wherein when a space is spatially centered relative to the spatial feature, and the space is read in a compatible disc drive, a resulting binary read data signal is not affected; and

wherein when the space is positioned so that an end of the space is adjacent to the spatial feature, and the space is read in a compatible disc drive, a resulting binary read data signal is affected.

18. The optical disc of claim 17, further comprising:

a groove, the space written in the groove.

19. The optical disc of claim 18, further comprising:

the spatial feature comprising an increase in a radial width of the groove, with a distance, tangential to a groove center line, along which the width of the groove is increased, being less than a spatial length of the space.

20. The optical disc of claim 18, further comprising:

the spatial feature comprising a decrease in a radial width of the groove, with a distance, tangential to a groove center line, along which the width of the groove is decreased, being less than a spatial length of the space.