MXPA01003582A - Method and apparatus for determining the provenance of a data carrying disc - Google Patents

Abstract

The manufacturing process for a data carrying disc, such as a CD, begins with the production of a master, and in the physical manufacturing process of the master, variations are introduced which give the master distinctive physical characteristics and cause errors in the data. The master is used to form generations of discs, and the physical characteristics of the master are passed on down the generations. A group of discs manufactured from the same source consistently exhibit the physical characteristics of the master, and those physical characteristics are used as a"fingerprint"for identifying that source. To determine the provenance of a data carrying disc, uncorrected data is read from the disc. Information about errors is extracted from the data read. The error information is then compared with characteristic error information which characterises data carrying discs produced from a well known source to determine whether the data carrying disc has been produced from the known source. The error information extracted is representative of errors arising from the physical manufacturing process.

Description

METHOD AND DEVICE FOR DETERMINING THE PROVENIENCE OF A DATA-CARRYING DISC FIELD OF THE INVENTION The present invention relates to methods and apparatus for determining the origin of data-carrying discs, such as compact discs (CD), and digital versatile discs (DVD).

BACKGROUND OF THE INVENTION The traditional CD is a read-only storage medium. Originally, the CDs were used for the storage of music and other audio data. However, formats have been developed, such as the CD-ROM format, which facilitate the reliable storage of data for use by computers and other digital devices. The CD-ROM format has become very popular and has become the mass storage medium for computer programs and other files. CDs can store approximately 74 minutes of high-quality stereo sound or approximately 650 megabytes of data or some combination of both. The value of a CD to the end user, due to the value of the data it stores, is typically much more than its physical cost. This has made it an attractive target for counterfeiters who can produce replicas of an original CD at a nominal cost and sell the replicas, at the market price for the data, in order to have large profits. With distribution media such as audio tapes or video cassettes, the quality of counterfeit copies tends to be lower than that of the originals due to the corruption of the analog signal in the copying process. However, there is no such degradation in the case of discs such as CDs, since all the information is stored digitally. Therefore, counterfeiters can produce counterfeit copies of the CDs which are almost indistinguishable from the original or authentic CDS. If it were possible to distinguish between an original or authentic CD and a counterfeit, then the problems caused by the counterfeiters could be reduced sub- tinctly. Law enforcement officials, for example, would have a means to identify counterfeit CDs, and could more easily obtain search warranties and ensure prosecutions. If a CD carries a program, that program could be used to verify that it was loaded from an original, authentic CD.

BRIEF DESCRIPTION OF THE INVENTION The present invention aims to identify counterfeit CDs and other data carrying discs. According to a first aspect of the present invention there is provided a method for determining from a data carrier disk, the method comprising the steps for reading uncorrected data from the disk and extracting information about the errors derived from reading of data, and comparing the error information with the characteristic error information characterizing the data carrier disks produced from a known source to determine whether the data bearer disk has been produced from the known source. The manufacturing process for a data carrier disk, such as a CD, begins with the production of a master, and the physical manufacturing process of the teacher, variations are introduced which give the teacher distinctive physical characteristics and cause errors in the data. The teacher is used to form generations of records, and the physical characteristics of the teacher are passed from generation to generation. A group of discs is manufactured from the same source, therefore, they consistently exhibit the physical characteristics of the master, and those physical characteristics can be used as a "fingerprint" for, or as an identification of, that source. This invention has relevance for all data-carrying disks, such as CDs or DVDs (digital versatile disks) and other optical discs, where errors in the data, which arise from the physical manufacturing process, are consistently reproduced at all the disks that originate from the same source.

Accordingly, in a method of the invention, the error information extracted is representative of errors arising from the physical manufacturing process and acts as a fingerprint for a particular known source in the manufacturing process. One embodiment of a method of the invention can be used to identify that a data carrier disk is genuine when error information is extracted from the disk that correlates with the error information characteristic of a genuine and known source. Similarly, the absence of correlation between the error information and the characteristic error information can be used to identify a counterfeit disk. CDs that carry music or popular computer programs, for example, can originate from a certain number of teachers coming from the manufacturing plants in different countries. Moreover, the teacher or each teacher will not be used to directly form the CDs. Each master is used in the production of a certain number of stampers which are used to produce the discs sold in the market. Therefore, it will be appreciated that although a teacher's fingerprint will be apparent in their progeny, each stage of the process will also introduce fingerprints from the sources used in these stages. Therefore, it is possible that if the error information extracted in one embodiment of a method of the invention is compared only with the error information characteristic of a genuine source, there will be no correlation. For example, if the characteristic error information comes from a teacher, but the cloning CDs can be made from one or a certain number of teachers, there may be no correlation and even this will not mean that the disk under test is forged. According to the above, unless the characteristic error information is used in the comparison, it is known to be characteristic of the single teacher, it will generally be necessary to store error information characteristic of a certain number of teachers or other sources. The characteristic error information with which the error information is compared may be representative of the errors that arise during the manufacture of the known sources. In addition, and / or alternatively, the sources from which the discs are produced can be printed with characteristic error information to provide copy protection signals in order to signify that the disc comes from a genuine source. The characteristic error information, with which the extracted error information is compared, can be read from a disk whose provenance is known, for example, in real time as the error information is extracted. Then a correlation can be made between the extracted error information and the characteristic error information from the genuine and known disk in order to determine the probability that the disk under test is a forgery. In a preferred embodiment, the characteristic error information is obtained from a group of discs from a known source, for example, those that are known to have been produced from a common and genuine master, or a common and genuine stamper . Common error information is then extracted for each of the disks in the group and stored to provide the characteristic error information with which the error information from a disk under test is compared. The methods of the invention can be used, as described, to determine whether a disk is genuine or counterfeit. Alternatively, the method can be used to establish the degree of similarity between a disc under test and discs from a known source. When data-carrying discs such as CDs and DVDs are read, the digital data is processed to correct the errors so that the normal output is free of errors. The error correction process is carried out in various stages. Therefore, where the disk is read by a laser, a bitstream is then formed which, for example, divided into blocks, whose blocks are translated into bytes and then into frames, the frames are submitted to error correction and then assembled into sectors and coding. The encoded data is then divided into sub-channels. In a method of the invention, the uncorrected information read from the data carrier disk can be taken from any of the stages or levels of data that are produced. The method requires that the data read reveals errors that have arisen from the physical manufacturing process. Accordingly, the data that is read does not usually undergo a significant error correction. Alternatively, the normal reading process can be modified to extract uncorrected information from the data bearer disk. Clearly, appropriate processing means may be used to allow the data to be read at any stage or level and extract the error information. In a reader for CD or DVD, for example, there are disk drive means for positioning the laser in relation to the sectors in the disk and the positioning data used by such disk unit means are not free of errors. In addition, the errors already incorporate means to read the positioning data. In a preferred embodiment of a method of the invention, it is proposed to extract the error information from the placement data read from the data carrier disk. Where the disk is a CD, it is preferred that a method of the invention reads the data blocks of the sub-channel Q in order to allow the extraction of the error information. In one embodiment of the method of the invention particularly relevant to current CDs and their readers, the method further comprises the steps for reading the blocks of the Q sub-channel of a CD and determining which blocks of the Q sub-channel have been corrupted or missing, and comparing the list of corrupted or missing blocks with a characteristic list of corrupted or missing blocks. The characteristic list of corrupted or missing blocks may have been produced by reading a group of CDs from a common source, determining for each disk a list of corrupted or missing blocks, and then forming a characteristic list of common or missing blocks common to all. the CDs of the group. In one embodiment, a number of characteristic lists obtained from the groups of CDs are stored and the error information extracted from a disk under test is compared with all the characteristic lists by which it is determined whether the CD is genuine. The present invention also extends to an apparatus for enabling the determination of the origin of a data carrier disk, the apparatus comprising a disk reader for reading uncorrected data from a data carrier disk, and processing means for extracting information. about the errors coming from the reading of data, and to compare the error information with the characteristic error information which characterizes the discs carrying data produced from a known source to determine whether the disk carrying data read has been produced from a known source In one embodiment, the apparatus comprises means for identifying that a data carrier disk is genuine when the error information extracted from the disk is correlated with the characteristic error information from a known and genuine source. In one embodiment, the apparatus comprises means for storing characteristic error information from a number of known sources. In addition, and / or alternatively, the acerate may comprise means for storing characteristic error information which has been printed in known means. The processing means may be installed to compare the extracted error information with the characteristic error information read from a disk whose provenance is known as the error information is extracted. According to a further aspect of the present invention there is provided an apparatus for enabling the determination of the origin of a data carrier disk, the apparatus comprising a disk reader for reading blocks of data from a data carrier disk, processing means for identifying and listing the data blocks that have been corrupted or missing, storage means for storing a characteristic list of data. Corrupted or missing data blocks characterizing discs produced from a known source, and means for comparing the identified list with the characteristic list to determine whether the disc has been produced from the known source. Preferably, the disk reader is installed to read blocks of positioning data such that blocks of location data that have been corrupted or missing can be listed and compared with a characteristic list of blocks of corrupted or missing placement data. In one embodiment, wherein the disk is a CD, the disk reader is preferably installed to read the subchannel Q blocks in order to extract the error information. In one embodiment, the processing means is installed to determine which blocks of the Q sub-channel have been corrupted or missing, and to compare the list of corrupted or missing blocks with the characteristic list of corrupted or missing blocks. The characteristic list of corrupted or missing blocks may have been produced by reading a group of CDs from a common source, determining for each disk a list of corrupted or missing blocks, and then forming a characteristic list of corrupted or missing blocks common to all CDs of 1 group. In one embodiment, the apparatus has a storage means for storing a certain number of characteristic lists obtained from genuine disk groups, and the processing means is installed to compare the identified list with all the characteristic lists by which it is determined if a test disk is genuine. The previously defined methods and apparatus allow genuine and counterfeit discs to be distinguished where, for example, all genuine discs come from a common source in such a way that they all carry the unique fingerprint of that common source. However, where there is no more than one genuine source for a group of discs, unless the tester has access to characteristic error information, or fingerprints, from all genuine sources, the determination of the origin of a Trial disk may be in doubt. Therefore, the result of a test must be that this disk is prone to fake because it does not correlate with the stored fingerprint information. Accordingly, it may be preferred to print a characteristic fingerprint or unique identification error information on all genuine discs when they are manufactured. According to a still further aspect of the present invention there is provided a method for incorporating characteristic error information on a data carrier disk, wherein the data carrier disk is physically manufactured either directly or indirectly from a master, and wherein the master is produced by a manufacturing process which is controlled through processing means, the method comprising the step to provide identification error data to the processing means in such a way that the identification error information is Incorporates into the teacher during his training. Accordingly, all manufacturing plants for recorded audio or software material could be provided with unique identification error information for that material whose identification error information is printed on the master, and therefore on any copies made from The, during the manufacture. The methods and apparatus of the invention for determining the provenance of the discs can thus reliably identify all the genomic discs, and therefore all the fakes. The methods and apparatuses of the invention can be used not only to identify genuine or counterfeit discs, but also to deny access to the data on the discs.

BRIEF DESCRIPTION OF THE FIGURES The embodiments of the present invention will be described hereinafter by means of the example, with reference to the accompanying drawings, in which Figure 1 shows schematically a data carrier disk with a spiral track, Figure 2 shows a frame format of data read from a CD, Figure 3 illustrates the format of a block of subcode data read from a CD, Figure 4 illustrates the general data format of sub-channel Q, Figure 5 illustrates the formation of a list of locations of the data errors, Figure 6 shows a block diagram of an apparatus of one embodiment of the invention for determining the origin of a CD, and Figure 7 shows an apparatus diagram for incorporating the error information. of identification on a CD.

DETAILED DESCRIPTION OF THE INVENTION As clarified above, the present invention can be used for any data carrier disks where data errors in the disks arise from the physical manufacturing process will be consistent for all disks originating from the same source. In particular, the invention can be used for CDs and DVDs. As it is known, a CD or a DVD originates from a vitreous master which is cut by a laser while the disc rotates on a mandrel. The intensity of the laser beam is modulated by the data to be recorded. Each teacher is used to make copies of nickel which are used to make stampers. Commercial CDs and DVDs are manufactured using these stampers. Each master is physically unique, and will have errors resulting from imperfections in the vitreous substrate or coating, and stent e, and arise from variations, for example, in the spinning speed of the mandrel and the movement of the laser.

These errors produce a fingerprint that is inherent to the teacher. Similarly, as the copy generations to produce the stamper and then the CD / DVD discs are manufactured directly and then indirectly from the master, additional unique fingerprints will be superimposed on each generation copy. These fingerprints, which are physical characteristics that can corrupt or cause errors in the data, are passed on to successive generations of copies. Of course, each generation, due to the manufacturing process used to produce it, has its own set of errors or its own fingerprint. Therefore, each CD or DVD has imposed fingerprints, one of which can be attributed to each of their ancestors. With the methods and apparatus of the invention, a group of discs coming from a common source are analyzed, for example all formed by the same stamper, and the errors common to all the discs in the group are identified. These common errors are therefore representative of the stamper's fingerprint and can be compared with the errors on a test disk to determine whether or not the test disk belongs to the same group. With this invention, errors in the data are accessed to determine the digital fingerprint of a disk. It will be appreciated that the data format of a CD differs from that of a DVD. For simplicity, the present invention is described herein with specific reference to CDs. However, the invention is applicable to DVDs, although the level at which errors in the DVD data format are detected will differ, and a modified DVD reader may be required in order to access the errors. In accordance with the foregoing, to further explain a specific embodiment of the present invention, the data format of a CD will now be briefly described. The data is recorded on the CDs in accordance with International Standard ISO / IEC 10149. The data is present on the CD as a sequence of holes of variable length in the reflective material of a CD. As indicated in Figure 1, these holes lie on a narrow spiral 4 which extends continuously from near the center of the reflecting portion to near the outside of the reflective portion of a CD 6. A CD player uses a laser to scan along the spiral and detects the edges of the holes by measuring the reflectance of the disk as it explores. The presence of a hole causes less light to be reflected back. The laser produces a beam of light which is reflected from the disk 6 to measure its intensity with a photodetector. The photodetector produces an analog signal which can be identified with the reflectance of the disc along the spiral. The signal is amplified and converted to produce a zero-bit stream with a set of bits for each detected edge. This is called the EFM stream (modulation eight to fourteen) and is the first digital signal coming from the disk. The EFM flow is divided into blocks separated by a 24-bit synchronization pattern. The synchronization pattern is followed by three "junction" bits and then 33 batches of 14-bit words each followed by three "junction" bits. The 14-bit words are passed through an EMF demodulator (for example, a query table) which translates the words into 8-bit bytes. Each block of EFM separated by the 24-bit synchronization pattern is therefore translated into a "frame" of 33 bytes as illustrated in Figure 2. One byte of each frame is used for the "subcode" and the remaining 32 bytes are passed to the decoders Cl and C2 which apply the error correction. The error corrected data comes out of the encoders in 24-bit blocks. These blocks are assembled sequentially, 98 at the same time, in sectors of 2352 bytes. These 2352 bytes encode the audio data but the computer data has another layer of error correction on top, leaving 2048 bytes of user data. The subcode bytes are vertically assembled 98 at the same time into subcode blocks as shown in Figure 3. The first two subcode bytes are synchronization bytes and the rest of the bytes are divided into subchannels P, Q, R, S, T, U, V, and W. The sub-channel P consists of the 96-bit high order bit of non-synchronization subcode. The subchannel block Q is made from the second highest order bit of the same bytes and so it happens if. Figure 4 shows the general data format of the subchannel block Q. As shown, the first four bytes of the subchannel block Q are the "control" field 8, the second four make up the "ADR" field 10. The 72 DATA-Q bits, 12, follow later, the interpretation of which depends on the value of the ADR field. Then follows a 16-bit CRC 14 over the previous three fields. The CRC detects errors but does not correct them. There is virtually the same number of subchannel Q blocks as sectors on a CD. It may seem from the description that the subchannel Q blocks correspond to sectors on a one-to-one basis; but this is not true enough since the encoders Cl and C2 delay some bytes for copying purposes with burst errors. The subchannel Q blocks do not enjoy the same level of error correction as the data in the sectors. This means that a few subchannel blocks on the disk do not have valid CRCs and therefore are corrupted due to the natural errors introduced during the master creation process and general usage wear. Normally the blocks of the sub-channel Q are used by the disk drive of a CD player to navigate around the CD. When the "ADR" field contains "0001" the DATA-Q bits encode the position of the block in the track from the beginning of the disc. Therefore, each block of subchannel Q has a unique address which increases monotonically. The subchannel block Q can be used to record other information such as the UPC / EAN which is effectively a bar code or an ISRC as defined in DIN- 31-621. These blocks of the subchannel Q do not contain many position data and therefore they are not so useful to navigate around the disk drive. They are placed at regular but fairly large intervals on subchannel Q so as not to interfere with the navigation requirements of the CD drive. It is not possible to detect errors on a CD when reading sector data as extensive error correction procedures ensure that sector data is always correct. However, there is no error correction applied to subchannel Q. Moreover, as the subchannel Q is used to provide position information it can be read by a conventional CD player. This means that specialized hardware is not needed to read the error information from the disk and then conventional processing means can use the data reading to extract the error information. With the method of the invention, laser reception moves to some position on the CD. In response to a command of the reading sub-channel Q, the block of the sub-channel Q that most recently passed under laser reception is read. This process is repeated sequentially until all the subchannel Q blocks have been read on a CD. As the entire isolate is read sequentially, any missing Q subchannel block can be identified and enlisted. These are the subchannel Q blocks which include corrupted data. They can be detected by comparing the CRC recorded at the end of the block with a CRC computed by the disk unit. If the CRCs are not the same, the subchannel block Q is listed as corrupted and therefore missing. As explained previously, a list of missing blocks will be unique for each disc, although a set of discs from the same stamper, for example, will have errors in common. Figure 5 schematically shows a CD 6 which has a number of errors E which are corrupted blocks of the Q sub-channel. The location of the errors E is listed, as described below, to form a list of errors L. Figure 6 shows a modality of an apparatus for determining the origin of a CD. This apparatus comprises a CD player 21 connected to the processing means 22. The processing means 22 communicates with a data storage 23 and also has a screen 24 which can be used to visually indicate information about the origin determination process. As explained above, a disc 6 is inserted to be tested in the CD player 21 and, under the control of the microprocessor 22, the CD is read sequentially. The CRC of each subchannel block Q is checked against the contents of the block and the microprocessor 22 then stores or displays a list L of the subchannel Q blocks which do not have a valid CRC. The list of corrupted or missing blocks could be used alone to determine the provenance of the CD. further, if required, the subchannel Q blocks which contain UPC / EANs or ISRCs are detected and written to be stored or displayed by the microprocessor 22. The microprocessor 22 may also, if required, calculate a checksum of the data on the CD and store or display the computed value. In addition or alternatively, it is possible to buffer the error flags coming from the encoders Cl and C2. This allows to extract the sectors of a list, and the positions within the sectors, where errors have been detected by the decoders. The decoders Cl and C2, as well as detecting errors, can correct them, and this fact, together with the information regarding which decoder detected the error and which decoder corrected the error, if indeed it corrected it, can be removed too. By all these means, the microprocessor 22 extracts error information from the CD to be used to determine its provenance. This error information is then compared with characteristic error information. To obtain the characteristic error information for comparison, the disks coming from the same batch are read using the apparatus shown in Figure 6 to extract the same error information as described. In this regard, the group of discs that have been read will have all been produced from the same master or stamper with the assumption that all the discs in that group will have errors caused by the fingerprint of that master or stamper. The data from all the disks in the group are compared to identify the error information that is common to each disk. Then the error information characteristic list can be formed and stored or displayed by the microprocessor 22. Then, the error information extracted from the disk under test can be compared with the characteristic list and it is possible to determine, by that comparison, whether the disk comes from the same group as the discs used to make the characteristic list. It would be possible to simply verify that the disk under test has all the errors in the characteristic list. However, preferably, the data from the test disk and the characteristic error data are correlated to calculate their degree of similarity. This can be done by cross-referencing the two sets of data, identifying the common characteristics, and then making a calculation using statistical methods of probability of common characteristics that occur purely by chance. A calculation of the probability that the discs come from different factories can be made. A certain probability is taken as the threshold above which the hypothesis will be accepted. The statistical method used can be selected as required. Current Bayesian statistical methods are preferred. When a characteristic list of error characteristics has been obtained and stored from a group of disks, it is then possible to sequentially test a certain number of disks against that stored list. The process can be accelerated by using the stored list to identify the portions of the disk under test in which errors would be expected, and then read only those portions on the test disk rather than sequentially reading the entire test disk. It is possible to generate a glass master with the missing Q subchannel blocks known by intentionally corrupting the CRC of some subchannel Q blocks at known positions. By this method, the positions of the blocks of the intentional missing Q sub-channel will be known before the glass master is fabricated and the data is recorded in it. If a vitreous master is produced using this process, then it is possible to verify that a disc is legitimate when searching to identify on a disk the known missing subchannel Q blocks. If any of the missing blocks, are in fact present, a determination can be made that the CD is forged and this information could be used, if required, to stop the execution of the disk. Conversely, if the missing blocks are missing, it is determined that the disk is genuine and can be used normally. Figure 7 shows an apparatus for recording a master with known identification error information such as, for example, a known characteristic list of subchannel blocks Q. The apparatus shown in Figure 7 is very similar to the conventional apparatus for manufacturing a master . The apparatus has a processing means 34, with memory, for controlling the system. In particular, the processor 34 controls a laser 32 for writing to a disk 20. A data storage medium 37, which will contain the data to be encoded on the disk 20, is coupled to the microprocessor 34, and the data is subsequently passed to the signal coding circuitry 33 wherein the data is then encoded in a laser intensity modulation signal. This signal is passed to the laser 32 which produces laser light with the required modulation. The light is passed through the laser graduation optics 31 which focus the laser light on the correct portions of the disc 20. The processing means 34 controls the placement of the graduation optics 31 by means of a writing servo 35. The processing means 34 also controls the rotary speed of the disk 20 by means of a needle controller 36 which controls the speed of rotation of a mandrel on which the disk 20 is installed. To add identification error information to the master , and for all generations of copies produced therefrom, it is only necessary to provide the required identification error data in the data storage medium 37. The identification error data causes the flow of user data encoded on the laser intensity modulation signal to be altered in order to introduce the features identified in the identification error data. Where the disc is a vitreous master, all stampers and discs made physically from it will have the same identification error data. If such a CD is then subjected to the method of the invention to identify its provenance, error information will be produced which correlates strongly with the identification error data supplied to the master in its manufacture. Where the identification error data added to the master, as described above, is an intentional corruption of subchannel Q blocks, a group of legitimate disks can be used to produce a list of the missing Q subchannel blocks common to the group . Then, it is only necessary to test each test disk to see if it has subchannel block Q in portions of it where the legitimate disks have missing Q subchannel blocks. The identification of a block where it is supposed to be missing shows that the CD is counterfeit. It will be appreciated that variations and modifications of the present invention may be made within the scope of this application.

Claims (26)

1. CLAIMS Having described the invention as an antecedent, the content of the following claims is claimed as property: 1. A method for determining the origin of a data carrier disk characterized in that, the method comprises the steps for reading data not corrected from the disk and extracting information about the errors derived from the reading of data, and comparing the error information with the characteristic error information characterizing the data carrier disks produced from a known source to determine whether the data bearer disk has occurred from the known source 2. A method according to claim 1, characterized in that the error information extracted is representative of errors arising from the physical manufacturing process. A method according to claim 1 or claim 2, characterized in that a data carrier disk is identified as genuine when the error information extracted from the disk is correlated with the error information characteristic of a genuine and known source. A method according to claim 1 or claim 2, characterized in that a data carrier disk is identified as counterfeit in the absence of correlation between the error information and the characteristic error information. A method according to any one of the preceding claims, characterized in that the sources from which the discs are produced have been printed with characteristic error information to provide copies protection signals on genuine discs. 6. A method according to any of claims 1 to 4, characterized in that it comprises the step to read the characteristic error information, with which the extracted error information is compared, from a disk whose provenance is known, and then to make a correlation between the extracted error information and the characteristic error information from the genuine and known disk in order to determine the probability that the disk under test is a forgery. A method according to claim 6, characterized in that the characteristic error information is read from the genuine and known disk in real time. A method according to any of claims 1 to 4, characterized in that it further comprises the steps for obtaining characteristic error information from a group of disks of a common source, and extracting and storing error information common to each of the disks in the group to provide the characteristic error information with which the error information from a disk under test is compared. A method according to any of the preceding claims, characterized in that the data on the data carrier disk is normally read by a process arranged to correct errors, the error correction process involving various stages or levels of reading, processing, correction and coding, and in that the method further comprises the steps for reading uncorrected information from the data carrier disk by taking data from any of the stages or data levels that occur during a normal reading process. A method according to any of claims 1 to 8, characterized in that the data on the data carrier disk is normally read by a process arranged to correct errors, the method comprising the step to modify a normal reading process in order to extract uncorrected information from the data bearer disk. A method according to claim 9 or claim 10, characterized in that it comprises the step for extracting error information from a data carrier disk from the reading of disk placement data. 12. A method according to the rei indication 11, characterized in that the disk is a CD, and the data blocks of the sub-channel Q are read in order to allow the extraction of the error information. 13. A method according to the claim 12, characterized in that it comprises the steps for reading the blocks of the sub-channel Q of a CD and determining which blocks of the sub-channel Q have been corrupted or missing, and comparing the list of corrupted or missing blocks with a characteristic list of corrupted or missing blocks. 14. An apparatus for enabling the determination of origin of a data carrier disk characterized in that the apparatus comprises a disk reader for reading uncorrected data from a data carrier disk, and processing means for extracting information about the errors coming from of reading data, and for comparing the error information with the characteristic error information which characterizes the data carrying disks produced from a known source to determine whether the read data bearer disk has been produced from a known source. Apparatus according to claim 14, characterized in that it further comprises means for identifying that a data carrier disk is genuine when the error information extracted from the disk is correlated with the error information characteristic of a genuine and known source. Apparatus according to claim 14 or claim 15, characterized in that it comprises means for storing characteristic error information from a number of known sources. Apparatus according to any of claims 14 to 16, characterized in that it also comprises means for storing the characteristic error information which has been printed in known sources. 18. Apparatus according to any of claims 14 to 17, characterized in that said processing means is installed to compare the extracted error information with the characteristic error information read from a disk whose provenance is known as the error information is extracted. . 19. Apparatus for enabling the determination of the origin of a data carrier disk because the apparatus comprises a disk reader for reading blocks of data from a data carrier disk, processing means for identifying and listing data blocks which corrupted or missing, storage medium for storing a characteristic list of corrupted or missing data blocks which characterizes discs produced from a known source, and means for comparing the identified list with the characteristic list to determine whether the disc It has been produced from the known source. Apparatus according to claim 19, characterized in that the disk reader is installed to read blocks of positioning data in such a way that blocks of laying data that have been corrupted or are missing can be listed and compared with a block characteristic list. of corrupted or missing placement data. Apparatus according to claim 20, characterized in that the disk is a CD, and in that the disk reader is installed to read the subchannel Q blocks in order to extract the error information. 22. Apparatus according to any of claims 19 to 21, characterized in that the apparatus has storage means for storing a certain number of characteristic lists obtained from groups of genuine discs, and the processing means are installed to compare the identified list with all the characteristic lists by means of which it is determined if a disc to test is genuine. 23. A method for incorporating identification error information into a disk bearer disk, wherein the disk bearer disk is physically manufactured either directly or indirectly from a master, and because the master is produced by a manufacturing process which is controlled by processing means, the method comprising the step to provide identification error data to the processing means in such a way that the identification error information is incorporated into the master during its formation. 24. A method for determining the origin of a data carrier disk substratically as described above with reference to the accompanying drawings 25. Apparatus for allowing the determination of the provenance of a data carrier disk substantially as described above with reference to the accompanying drawings. 26. A method for incorporating identification error information into a data carrier disk substantially as described above with reference to the accompanying drawings. SUMMARY The manufacturing process for a data carrier disk, such as a CD, begins with the production of a teacher, and in the physical manufacturing process of the teacher, variations are introduced which give the teacher distinctive physical characteristics and cause errors in the data. The teacher is used to form generations of records, and the physical characteristics of the teacher are passed from generation to generation. A group of discs that is manufactured from the same source consistently exhibits the physical characteristics of the teacher, and those physical characteristics are used as a "fingerprint" to identify that source. To determine the origin of a data carrier disk, the uncorrected data is read from the disk. The information about the errors is extracted from the reading of the data. The error information is then compared with the characteristic error information which characterizes the data carrier disks produced from a well-known source to determine whether the data carrier disk has been produced from the known source. The extracted error information is representative of the errors that arise from the physical manufacturing process.