Copy-protected optical disk and protection process for such disk

• US 20010024411A1
• Filed: 02/09/2001
• Published: 09/27/2001
• Est. Priority Date: 02/11/2000
• Status: Active Grant

• Current Assignee: MPO International
• Original Assignee: Thomson-CSF
• Inventors: Duhamel, Jean-Louis, Rieux, Marc Des, Le Carvennec, Francois, Pirot, Francois-Xavier
• Granted Patent: US 6,738,331 B2
• Time in Patent Office: Days
• 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 20/00586 said format change concerning the physical format of the recording medium
• CPC Class Codes: G11B 23/284 on the record carrier
• CPC Class Codes: G11B 7/007 Arrangement of the information on the record carrier, e.g. form of tracks , actual track shape, e.g. wobbled, or cross-section, e.g. v-shaped; Sequential information structures, e.g. sectoring or header formats within a track

Abstract

The disclosure relates to an optical disk of the type including at least one spiral track on which information marks are written in sectors whose addresses are substantially sequential along the track, wherein said disk includes a copy protection zone (PZ) comprising two parts of equal size each including a series of sectors designated by identical addresses on each of the two parts, the data written in this zone being shared between the sectors of the two parts, each sector of the zone also carrying an identifier (D1, D2) characteristic of the part to which the sector belongs, and specific protection data to enable verification of the presence and constitution of said protection zone (PZ) and to enable use of the data written in this zone, at least part of said specific protection data being recorded on said disk. The invention is notably applicable to anti-piracy protection of CD-ROM and DVD-ROM type disks.

Claims

1. A copy-protected optical disk of the type including at least one spiral track on which information marks are written in sectors whose addresses are substantially sequential along the track, wherein said disk includes:

a copy protection zone (PZ) comprising two parts of equal size each including a series of sectors designated by identical addresses (A to A+Q) on each of the two parts, the data written in this zone being shared between the sectors of the two parts and each sector of the zone also carrying an identifier (D1, D2) characteristic of the part to which the sector belongs; and

at least specific protection data to enable verification of the presence and constitution of said protection zone (PZ) and to enable use of the data written in this zone, at least some elements of said specific protection data being recorded on said disk.

2. An optical disk according to

claim 1

, characterized in that it includes a main continuous spiral track (1) covering all the useful part of the disk and whose sectors have addresses ordered substantially sequentially along this track, and at least one secondary track (2) inserted between turns of said main track, the sectors on this secondary track and the adjacent sectors in a given radial direction on said main track having the same addresses (A to A+Q), in order to constitute said two parts of said protection zone (PZ).

3. An optical disk according to

claim 2

, wherein said insertion of said secondary track in said main track is carried out in such a manner as to maintain the normal pitch of the spiral track over substantially the whole disk.

4. A copy-protection process to determine whether an optical disk is an original disk or an illegal copy and prevent normal use in the case of a copy, said original disk including at least one spiral track (1) on which information marks are written in sectors whose addresses are substantially sequential along the track, said process being characterized in that it consists in:

defining on the original disk a protection zone (PZ;

PZ′

) in two parts of equal size each including a series of sectors designated by identical addresses (A to A+Q) on each of the two parts, the data written in this zone being shared between the sectors of the two parts and each sector of the zone also carrying an identifier (D1, D2) characteristic of the part to which the sector belongs;

performing a succession of reads of at least one predetermined sector (X) of said protection zone;

verifying, by means of said identifiers (D1, D2), that during these reads, access has been made to the two predetermined sectors (X) having the same address in each of two said parts of said protection zone.

5. A copy-protection process according to

claim 4

, characterized in that it also consists in defining on the original disk a forward jump zone (FJZ) and a backward jump zone (BJZ) on either side of the said protection zone (PZ;

PZ′

), and in that said stage involving a succession of reads consists in making a first series of reads starting from the forward jump zone and a second series of reads starting from the backward jump zone.

6. A process according to anyone of claims 4 or 5, wherein, when said stage of verification of access to said predetermined sector (X) does not enable access to the two sectors of the same address in each of two said parts of said protection zone, this stage is repeated on other sectors of said protection zone (PZ;

PZ′

).

7. A process according to anyone of

claims 4

to

6

, in which the original disk includes a continuous spiral main track (1) covering all the useful part of the disk and whose sectors have addresses ordered substantially sequentially along this track, and at least one secondary track (2) inserted between the spirals of the main track, said process being characterized in that the same addresses (A to A+Q) are assigned to successive sectors on said secondary track and to the sectors substantially adjacent in a given radial direction on the main track, in order to constitute said two parts of said protection zone.

8. A process according to

claim 7

, characterized in that it also includes a stage to verify the physical presence of said secondary track.

9. A process according to

claim 8

, wherein said verification of the physical presence of said secondary track is based on the verification of the durations of different processes and/or reads carried out on said disk.

10. A process according to

claim 9

, wherein said verification of the physical presence of said secondary track consists in measuring the time necessary for the reading of all the sectors between an address preceding the first address (A) of said protection zone (PZ) and an address after the last address (A+Q) of this protection zone.

11. A process according to

claim 9

, wherein said verification of the physical presence of said secondary track consists in measuring the time (t₃) necessary for the reading of all the sectors having an address between the first address (A) of said protection zone (PZ) and the last address (A+Q) of this protection zone, starting from one of said jump zones (FJZ, BJZ), then measuring the time (t₄) necessary for the reading of all the sectors having an address between the first address (A) of said protection zone (PZ) and an address (A+Q+p) after the last address (A+Q) of this protection zone, starting from the same jump zone, and finally comparing said reading times (t₃, t₄).

12. A process according to

claim 11

, characterized in that it also includes a read, starting from the other jump zone (BJZ, FJZ), of the sectors of addresses between an address (A+Q−

k) preceding the last address (A+Q) of said protection zone and an address (A+Q+p) after the last address (A+Q) of this protection zone, and checking said identifiers (D1, D2) detected during this reading.

13. A process according to anyone of

claims 7

to

12

, characterized in that it also includes replacing by lures, on said main track, the data items of the application corresponding to the data recorded in sectors of said secondary track, such that said lures and the data actually recorded on said main track form a coherent and executable set of data, and in that, when said process reveals that the disk is a copy, the reading of the genuine and lure data on said main track allows the application to continue executing but in a degraded manner.