EP1159742A1

EP1159742A1 - Antihacking optical recording disc and method for reading same

Info

Publication number: EP1159742A1
Application number: EP99958304A
Authority: EP
Inventors: François Thomson-CFS Prop. Intel. LE CARVENNEC
Original assignee: Thales SA
Current assignee: Thales SA
Priority date: 1998-12-15
Filing date: 1999-12-10
Publication date: 2001-12-05
Also published as: US6452886B1; FR2787232A1; AU1569400A; WO2000036601A1; FR2787232B1; JP2002532820A

Abstract

The invention concerns a recording disc comprising a main spiral track (1) and a section of secondary track (2) inserted between two successive turns of the main track. A use zone (3) comprises data (30) concerning the type of the antihacking disc and data (31) concerning the relative positioning of the section (2), which the disc player reaches by going to an address (A) of the main track and by skipping over the track (10). The section is then identified by identification data which it bears and then the disc physical structure is verified for its conformity with that described in the initialising zone. The invention is applicable to provide any optical disc, in particular CD or DVD with antihacking.

Description

ANTI-PIRACY OPTICAL RECORDING DISC AND METHOD FOR PLAYING SUCH A DISC

The invention relates to an anti-piracy optical recording disc and to a method for reading such a disc. The invention can in particular be applied to optical discs in CD or DVD format but it also extends to any other format. Due to the appearance on the market of CD type recorders

(CD-R or CD-RW and soon DVD burners) at low cost, duplication, in particular CD-ROM or DVD-ROM, has become or will become accessible to semi-professionals or amateurs. However, it is very important for publishers, in particular software or game publishers, to protect themselves against hacking of their data, especially if it is on an industrial scale.

There are already a few systems making it more difficult to copy information and / or use it. These systems are notably based on encryption techniques. However, their effectiveness is limited because, with the IT resources available to potential hackers, the "sealing" of these systems is far from impossible.

The subject of the invention is a disc and an anti-pirating reading method prohibiting unauthorized use of the stored information and in particular the use of pirated copies by using a disc having a specific physical configuration. The disc of the invention can be read by a conventional player, without modification. But its structure makes any copy by easily accessible means unusable and the structure of the disc cannot be simulated. In addition, the reproduction of such a disc cannot be done without very sophisticated and extremely expensive industrial means.

According to the invention, there is therefore provided an optical information recording disc comprising a continuous main recording track, recorded generally known in the form of a spiral comprising a plurality of successive turns, characterized in that the disc further comprises at least one section of secondary track interposed between two adjacent spiral turns, said section carrying at least one identification information specific to said section, a first information on the anti-piracy nature of the disc and a second information on the positioning of the section of secondary track relative to the main track, said first and second information being arranged in a zone of initialization of disc playback on the main track.

According to another aspect of the invention, there is provided a method for reading the above disc, characterized in that it comprises the steps of: a) reading the information arranged on the main track in said initialization area; b) check that the physical structure of the disk conforms to that described by the information in the initialization area; c) authorize the use of the information carried by the main track and the operation of the corresponding application only when the result of the verification of step b) is positive. The invention will be better understood and other characteristics and advantages will emerge from the following description and the accompanying drawings, in which:

- Figure 1 is the diagram of a first embodiment of a disc according to the invention; - Figure 2 shows a variant of the disc of Figure 1; and

- Figure 3 is another variant where the secondary track portion is assumed to occupy more than one revolution on the disc.

On an optical disc, in a conventional manner, the information is written on a track in the form of a spiral. The reader follows this spiral to recover the information. These are generally grouped by blocks recorded in sectors identified by addresses. On the support is recorded a content table (TOC or "Table of contents") assigning the blocks or sectors to the different files.

According to the invention, provision is made to insert between two (or more) adjacent turns of the main track a section of secondary track parallel to the main track.

Figure 1 shows an exemplary embodiment. On the disc is provided a main track 1 in a spiral. This track is designed to carry information in a conventional manner, for example in accordance with the specifications of CD or DVD discs. A section of secondary track 2 is interspersed between two consecutive laps of the main track 1. This section is here assumed to be much shorter than one lap of the track. This section is arranged with a standard spacing between the turns of the main track, that is to say that the spacing between the adjacent laps of the main track is equal to the standard spacing between two normal adjacent laps of the main track. It can be seen that at the level of the secondary track section, the main track reaches a double gauge; the connection between the standard deviation and the double deviation must be made gradually so that a normal reader does not have to skip a track.

The disc comprises on the main track an initial area 3, loading area or TOC or even area called “boot” in the Anglo-Saxon literature, which includes a first piece of information 30 on the anti-piracy nature of the disc and a second piece of information 31 on the positioning of the section of secondary track 2 relative to the main track. For example, information 31 will indicate address A on the main track as well as an indication of a jump to track 10 on the right which will allow the reader to go to the start of section 2. Information 31 may also include the indication of the length of the section (or of the end address). The section 2 comprises at least one piece of recorded information identifying said section. This section may also include other information usable in anti-piracy protection.

The operation for reading this disc is as follows. The player starts playing in the same way as a conventional disc; it necessarily centers on the main track, even if it passes for an instant through the secondary track section and goes to the initialization zone 3. There it reads information 30 and 31. This implies that the operation of the application and use of the information on the main track will only be authorized after verification that the physical structure of the disc conforms to that described in zone 3, which indicated that it was a anti-piracy disc and that a section 2 was at the positioning (start, length) determined by information 31.

The reading method according to the invention provides for several possible verification methods mentioned above. The first step is, in all cases, to go to the start of the secondary runway section 2 and to verify the presence of the section specific identification information.

A first possibility for this step is to indicate the address A on the main track facing the start of the section 2 and the direction of the jump of a track to be performed (here on the right in FIG. 1). But we could also go to the address A + 1 turn and make a jump to the left.

You must then ensure that the anti-piracy disk and its physical structure have not been simulated. To do this, a first method can consist in making the reader read, after address A, a complete revolution of the main track plus the expected length of section 2 (for example up to address A '). If the identification information for section 2 has not been found, it is because the disc has the advertised physical structure. Indeed, if we wanted to simulate section 2 on the main track, we would necessarily meet it from address A + 1 lap. It is clear that this verification can be carried out at the start of the use of the disc but also randomly during the use of the disc, which further increases the difficulty of copying the disc by simulating its structure.

To further improve anti-piracy security, we can, as already mentioned, indicate with information 31 the length of section 2. Indeed, we could imagine that we are making recordable discs with at least one length blank secondary track covering one or more spiral turns at the beginning of the disc or even, if there is no capacity problem, provide a secondary spiral track on the entire disc. A pirate could then copy the anti-piracy disc entirely and place section 2 in the right place on the blank secondary track. In this case, if we stop at the only verification described above, we will not notice that we are in front of a copy.

Also, provision may be made to further verify the length of the section by observing whether or not there is a portion of secondary track not recorded after section 2.

This can be done, for example, by checking that at the end of the indicated section, the reader immediately returns to the main track (to the right or left of the section) with the addresses provided. We can also do an operation consisting in going to the corresponding address A ', on the track main track, at the position of the end of section 2, then jump to the track (here on the left) and check that you land on the main track and not on a secondary track extension.

FIG. 2 represents a variant which makes pirating a disk even more difficult. This figure shows the main track 1, the initialization zone 3 and the first section of secondary track 2. However, a second section of secondary track 4 is provided, inserted in another position between two (or more) laps main. The positioning information 20 of this second section 4 is carried by the first section 2. Thus this information is relatively hidden.

After the reader has accessed the section 2 as provided above, it reads the information 20 to get to the section 4, for example in the same manner as previously by going to the address B then by performing a jump track 40 on the right. FIG. 3 illustrates another embodiment where the section of secondary track 2 ′ has a length greater than one complete revolution. This does not change the process described above.

However, when describing this other embodiment, another method of verifying the physical structure of the disc can be described. To do this, from the information read in zone 3, we go to address A and then we skip a track to the right to then read the section 2 'and its identification information. Verification of the physical structure of the disc can then be carried out by going to the main track at the address C = A + 1 lap, making a jump to the left and then verifying by the identification information that we read the section 2 'again.

It is clear that the anti-piracy protection can be further improved by recording on the secondary track section or sections other information than that of identification. In particular, it is possible to introduce encryption techniques (authorization key, etc.).

The advantages of the invention are numerous. The main track information is read transparently by standard readers. Only basic access / read functions of the reader are used, activated beforehand or during the course of the application and the use of the information on the disc. This leads to good compatibility with standard means of implementation of drives and application processes and an additional difficulty in simulating operation with copy disks, since it is more difficult to identify the use of disk identification when this recourse takes place during the usage program.

The effectiveness of the anti-piracy according to the invention is all the greater when the general public users of current recorders cannot implement the structure described. In addition, the positioning and the length of the secondary track section or sections may vary from one type of disc to another, it is not possible to produce special recordable discs intended for pirated copying of the discs according to the invention .

Finally, the serial duplication of pirated copies (pressing) is not within the reach of a simple industrial pirate because it requires specific resources corresponding to very significant investments such as two-beam mastering machines.

Claims

1. Optical information recording disc comprising a main recording track (1) continuous, recorded generally known in the form of a spiral comprising a plurality of successive turns, characterized in that the disc further comprises , on the one hand at least one section of secondary track (2) interposed between adjacent spiral turns, said section carrying at least one specific identification information, on the other hand first information (30) on the anti- disc piracy and a second piece of information (31) on the positioning of the section or sections of secondary track with respect to the main track, as well as a characteristic indication of the length of the section or sections, said first and second information being arranged in an area (3) initialization of disc playback on the main track.

2. Disc according to claim 1, characterized in that said secondary track section (2) is disposed between the adjacent turns of the spiral with a spacing with respect to each of these equal to the standard spacing between two turns of the spiral any successive.

3. Disc according to one of claims 1 or 2, characterized in that said secondary track section further carries information usable during the course of the application stored on said main track.

4. Disc according to any one of claims 1 to 3, characterized in that the disc further comprises at least a second section of secondary track (4) interposed in another position between consecutive spiral turns, said second section bearing at least one identification information specific to said second section, and in that the first section of secondary track also carries at least third information (20) on the positioning of said second section (4) relative to the main track (1 ).

5. A method of reading an optical information recording disc comprising a continuous main recording track (1), recorded generally known in the form of a spiral comprising a plurality of successive turns, the disc comprising, in addition, on the one hand at least one section of secondary track (2) interposed between adjacent spiral turns, said section carrying at least specific identification information, on the other hand first information (30) on the nature anti-piracy of the disc and a second piece of information (31) on the positioning of the section of secondary track with respect to the main track, said first and second information being arranged in an area (3) for initializing the reading of the disc on the main track, said method being characterized in that it comprises the steps of: a) reading the information arranged on the main track in said initialization area; b) check that the physical structure of the disk conforms to that described by the information in the initialization area; c) authorize the use of the information carried by the main track and the operation of the corresponding application only when the result of the verification of step b) is positive.

6. Method according to claim 5, characterized in that said step b) consists of: b1) using said second positioning information to access said section of secondary track; b2) verify the presence of said section specific identification information; and b3) verify that the said section is not an element of the main runway.

7. Method according to claim 6 for reading a disc according to any one of claims 1 to 4, characterized in that said step b3) of checking that said section is not an element of the main track s' performs from said second positioning information and from said characteristic indication of section length.

8. Method according to one of claims 6 or 7, characterized in that the access according to step b1) to said section of secondary track is carried out by accessing a predetermined address of said main track provided by said second information and by jumping a track in the direction indicated by said second information.

9. Method according to one of claims 7 or 8, characterized in that the verification according to step b3) is carried out by reading at least one complete revolution of the main track starting from the address facing said longer section l space occupied by the information carried by said section and by verifying that said identification information is not encountered.

10. Method according to claim 8, characterized in that the verification according to step b3) is carried out by making a complete revolution of the main track starting from the address opposite said section, then by making a jump track in the opposite direction to the jump made during step b1), finally by checking for the presence of said section specific identification information.

11. A method according to any one of claims 7 to 10, characterized in that said method further comprises a step of verifying the absence of a secondary track after the end of said section.