MXPA99001090A - Method for copy protecting a record carrier, copy protected record carrier and means for detecting access control information - Google Patents

Abstract

A method for copy protecting a record carrier is disclosed, in which method the copy protected record carriers are provided with a pattern of logical errors which cannot be corrected by the error correcting rules predefined for said record carrier. The pattern of logical errors represents access control information. The logical errors are generated during decoding the bit sequence read from the record carrier. Bit errors may be positioned in the bit sequence so as to counteract de-interleaving which is part of an error decoding process in a reading device and accumulate in error words which are uncorrectable. Also a method for detecting access control information and a retrieval arrangement are disclosed, which retrieval arrangement serves to detect the access control information by selecting at least one error location, but not all error locations on the record carrier, and verifying the presence of an error by reading the selected error location via the reading means.

Description

METHOD TO PROTECT AGAINST COPY A REGISTRAR CARRIER, PROTECTED REGISTRATION CARRIER AGAINST COPY AND MEANS TO DETECT ACCESS CONTROL INFORMATION DESCRIPTION OF THE INVENTION The invention relates to a method for protecting against copy a record carrier having information stored therein, according to the rules for formatting and correcting predetermined errors, comprising the steps of creating an image file that it comprises important information, generating access control information to control access to important information, producing a master portadox depending on the image file and access control information, production which comprises the steps of creating a sequence of bits applying the rules to format and correct errors to the image file and translate the sequence of bits into a physical pattern of marks, and multiply the record carrier using the record carrier. The invention further relates to a copy protected record carrier having a sequence of bits stored therein that represents information according to the rules for formatting and correcting predetermined errors, the information comprises important information and access control information for control access to important information The invention further relates to a method for detecting access control information on such a copy protected record carrier. The invention further relates to a recovery rule for retrieving information such as that of a copy-protected record carrier, the arrangement comprises reading means for reading the record carrier, the reading means comprises a reading unit for extracting a sequence of bits stored in the record carrier and an error correction unit for processing the bit sequence. A system for protecting against copying a record carrier, a copy protected copy carrier and a read array is known from EP-0545472 (document DI in the list of related documents). The known record carrier comprises a prearranged track guide, called pre-slot. In the track determined by the pre-race, the information that is written in a predefined form is represented by optically readable patterns which are formed by the variation of a first physical parameter, such as the height of the scanned surface. The pre-race has variations in a second physical parameter, such as an excursion in a transverse direction, also denoted as eccentric rotation. The eccentric rotation of the pre-bead is modulated by EM- and this modulation represents the access control information that is related to the information, such as a demixing code to retrieve the information stored as mixed information. The known device comprises reading means for reading patterns and recovery means for retrieving access control information. The known information carrying device forms a system for the reproduction of controlled information. For this purpose, the device comprises means for reproducing the information depending on the access control information. If the information is copied with a writable information carrier, the information in this copy will not be reproduced, because during the writing process only the patterns are written and the copy itself does not contain any access control information. A problem in the known system is that the reading means must be able to recover the access control information by detecting the variations of the second physical parameter. An object of the invention is to provide a system for protecting against copy of record carriers, which does not depend on variations of the physical parameters, while at the same time avoiding useful copies on the writable information carrier. For this purpose a method to protect against copying a record carrier as described in the initial paragraph, is characterized according to the invention because the 5 bits of the production step in the bit sequence are changed according to the access control information to constitute logical errors which can not be corrected by the error correction rules and which constitute a pattern of errors. A record carrier Copy-protected JO as described in the opening paragraph is characterized according to the invention because the bit sequence comprises bit errors that constitute logical errors, which can not be corrected by the error correction rules and which constitute a pattern from errors representing at least part of the access control information. The measurements are advantageous since the error pattern can be easily detected, while errors can not be included in the information stored in a copy of the record carrier via a standard recording device, because such registration devices have built-in error correction rules, which can not be manipulated. According to a second aspect of the invention a The method for detecting access control information on such a copy-protected record carrier is characterized in that the method comprises the steps of selecting at least one place with errors, but not all places with errors, places with errors which must have a logical error according to the error pattern, and verify the presence of an error by reading the places with selected errors. A recovery arrangement for recovering information from such a copy protected record carrier as described in the opening paragraph is characterized in that the arrangement comprises access control means to control access to information, access control means which are incorporated to detect the access control information by selecting at least one place with errors, but not all places with errors, places with errors which must have a logical error according to the error pattern, and verifying the presence of an error by reading the place with errors selected via the reading means. In this way it is advantageous to select a few places with errors from an available number, which results in a rapid response to the access control means. The reading of a sector that has errors can take up to 30 seconds in a standard reading device, such as a CD-ROM driver, due to successive automatic attempts. Also, selecting different places for each access control session increases the difficulties for a malicious party to imitate the access control process. It should be noted that WO 95/03655 (document D3) describes an encryption or coding system of PROM CD, in which the information on a CD-ROM is encrypted or coded by a key, which key is programmed in the CD-ROM after its manufacture damaging selected sectors so that they can not be read by conventional reading systems. The selected sectors are physically damaged by a high-energy laser. Registration bearers are activated individually to possess a specific key for each certain user or group of users. The invention was also based on the following recognition. The physically damaged selected parts of a record carrier lead to corrupted physical marks. When such damaged parts are read a read head may lose track, or the translation of the read signal to a sequence of bits may be disturbed or lose synchronization, all of which results in an uncontrollable number of errors. In addition, physical damage can be easily detected from physical parameters and can be imitated by a malicious party by physical means. Also, physically damaged sectors increase production costs. The invention was based on a logical error pattern, which does not increase production costs and allows precise control of the resulting errors. In addition, the inventors had the idea that physical errors can not be used to generate errors in a limited part of the recovered information, since they are similar to synchronization errors, type of errors which is widely disseminated due to the deinterleaving steps usually applied to the bit sequence in an error correction process and format elimination to recover the information. Therefore, an embodiment of the copy-protected register carrier is characterized in that, although the bit sequence comprises information bits and error correction bits, the information bits comprise the bit errors and / or because the bit errors they are located so that they accumulate in an incorrigible erroneous word by a wrong word correction rule when reproduced. This is advantageous given >that bit errors concentrate on erroneous words that result in ambiguities in JLogical errors, while error bits extend to other parts of the retrieved information. An additional embodiment of the copy-protected record carrier, record carrier which is subdivided into addressable sectors, is characterized in that the region carrier comprises a filling area, filling area which comprises sectors with errors and sectors without errors , sectors with errors which comprise the logical errors and constitute the error pattern. Using sectors as constituent elements for the 5-error pattern has the advantage that the reading devices - standard will read and process the information, sector by sector, generating at the same time an error message if a sector with an error has been detected incorrigible. An additional embodiment of the copy protected log carrier is characterized by the part of the bit sequence corresponding to sectors without errors which are adjacent to sectors with errors substantially comprising bit errors. In the case of some dust or scratches the affected sectors will show errors of random or small synchronization. If such errors had to be corrected in the presence of intentional bit errors, there would be an increased risk that a sector without errors would be classified as a sector with errors. Have bit errors substantially no intentional is advantageous since there is a low probability that the sectors without errors are misclassified. An additional mode of the copy-protected record carrier is characterized in that, although the The registration carrier has a predetermined storage capacity, which covers a part of the important information, the filling area substantially covers the remaining part of the storage capacity of the information. This has the following advantage. All the logical errors that make up the error pattern can only be detected by reading the entire filling area. In an average record carrier a relatively large percentage of the storage capacity of the information may be unused, which is available for the error pattern without increasing production costs. A, for example, 20 seconds of reading time for a sector that has errors due to several attempts, will take more than 1000 hours to read the total fill area on a CD-ROM that has 60% of its capacity unused. An embodiment of the method for detecting access control information is characterized in that the method also includes the steps of selecting at least one place without errors, but not all places without errors, places without errors which should not have a logical error of agreement to the pattern of errors, and verify the absence of an error by reading the places without selected errors. This is advantageous since an illegal copy that has errors in places without errors will also be detected. A further method of the method for detecting access control information is characterized in that at least one place without errors is selected, which is next to a place with errors. This is advantageous since an illegal copy that has physical errors or the type of synchronization extended over more places will be detected due to the deinterleaving rules. Advantageous, advantageous, additional embodiments of the copy protected record carrier, the recovery arrangement and the methods according to the invention are given in the additional dependent claims. These and other aspects of the invention will be apparent from, and further elucidated with reference to the embodiments described by way of example in the following description and with reference to the accompanying drawings, in which Figure 1 shows a carrier of registration protected against copying Figure 2 shows a logical map of a registration area of. a copy-protected record carrier Figure 3 shows an error correction unit Figure 4 shows a bit error pattern Figure 5 shows an arrangement for retrieving information from a copy-protected record carrier Figure 6 shows a diagram Schematic to protect against copy a record carrier.

Figure 1 shows schematically a record protected copy carrier in the form of disk 1. The record carrier comprises a track 9 for storing information, which track is arranged in a helical pattern of turns around a central hole 10. The turns they can also be arranged concentrically instead of helically. The record carrier 1 is of an optically readable type, in which a transparent substrate is covered by a recording layer and a protective layer, such as the well-known Compact Disc (DC). The information on the -information carrier is represented by patterns of optically readable marks. For example, the position and / or length of the marks then represent a binary information signal. Brands can be made by means of presses, as is customary for read-only CDs, such as the CD-ROM on which depressions and protrusions are stamped between the depressions that represent the information. The invention can be used for any type of record carrier, on which information is recorded according to the predetermined error correction rules, such as high-density DVD optical disk (Digital Versatile Disk), optical tape or magnetic tape for digital video The track 9 comprises the marks and is searchable by a read head to read the stored information. The marks represent a sequence of bits according to a channel code, such as EEM for CD (Modulation from Eight to Fourteen). The bit sequence represents information according to the rules of correction of errors and to format predetermined, such as the CIRC (Code of Reed-Solomon Interleaved Crossed) for CD. According to the rule for formatting, the record carrier can be subdivided into addressable sectors, such as on the CD-ROM. The CD-ROM is described in ISO 10149, the specification of the CD-ROM. Information about the copy-protected record carrier 1 comprises important information and access control information to control access to important information, to prevent access to important information copied in an illegal copy, a copy which does not cover all of the necessary access control information. According to the invention, the record carrier protected against copy 1 is provided with logical errors 2, logical errors, which constitute an error pattern representing at least some of the access control information. The error pattern has at least one logical error in a predetermined place, but preferably, a pattern of logical errors in a relatively large number of predetermined places. A different error pattern can be generated for each new title to be distributed on a copy-protected registry bearer. In an error pattern mode, places with errors should intermix with places without errors or with essential information. In addition, the error pattern can comprise a number of places with isolated errors between places without errors, but also some places with consecutive errors. Preferably, the pattern of locations with errors is a pseudo-random pattern comprising about 50% of places with errors and 50% of places without errors, the pseudorandom pattern is generated from a value sown by a predetermined algorithm. The pattern of errors must be verified in an access control procedure, a procedure which is indissolubly included in the procedure to use the important information. The verification should include at least one place with errors and preferably also, at least one place without errors in the vicinity of a place with errors. This prevents a malicious party from easily imitating the error pattern by physically damaging a few places. A logical error is constituted by a number of bit errors in the bit sequence, number of bit errors which is incorrigible by the error correction rule. Bit errors can not be copied using a standard recording device, since such a device will accept the information to be recorded without the error correction bits. The recorder will process this information according to the rules of correction of errors and to format integrated, predetermined, to generate a new sequence of bits, including the bits of correction of errors "that are generated and inherently corrected. new bit sequence will not understand any error, it will not be accessible to change the bits in such standard register devices The new bit sequence can be registered in a writable record carrier, but this copy will not understand the error pattern. It should be noted, that logical errors must be applied to the sequence of bits after the error coding step before writing the physical pattern of marks so that it can not be corrected by the error decoding step after the reading of the marks . The application of errors to a higher system level before the encoding of errors, for example, by intentionally changing the CDC (Error Detection Code) in a sector or a sector header on a CD-ROM, can be easily imitated by a malicious part because the process of formatting higher levels is usually done via a program, and therefore is accessible to manipulation. An operational, but illegal, copy that comprises higher-level errors can be made with the standard registration devices and programs (adapted) in the connected computer system, for example a program for copying bits available to make audio CD copies. Since synchronization errors will occur due to dust or scratches on the surface of a record carrier, the error correction rules, for example CD, are specially designed to correct synchronization errors by applying collation before storing and deinterleaving after to read. The bit errors that constitute such synchronization error will be mixed with a larger number of other bits of the bit sequence by the deinterleaving rules that are part of the rules for formatting and correcting errors. A number of consecutive bit errors sufficient to produce incorrigible errors must be larger than the largest corrected synchronization error. The error correction rules are described with Figure 3. In a preferred embodiment only the selected bits of the bit sequence show errors, bits which are selected to be accumulated by de-interleaving, de-interleaving which is part of the rules for formatting and correct errors. This results in a place on the record carrier that shows a high concentration of errors, while the attached places show only a few or do not have errors. An example of bit errors is described in Figure 4. Usually the error correction rules and especially the (de) interleaving rules will operate on symbols, for example on 8-bit bytes, while the error correction process is applied to erroneous words of a number of symbols accumulated by deinterleaving. Erroneous symbols are selected to accumulate during deinterleaving into an incorrigible number in one or a few erroneous words. An effective way to apply bit errors is to invert each bit of a selected symbol in the original bit sequence without errors, selected symbol which must be provided with a bit error. Alternatively bit errors can be applied to the symbols, when the symbols are translated into the physical mark pattern, for example using a controllable EFM encoder. For such symbols the EFM encoder can be controlled to change some of the physical marks to be different from the marks originally attempted based on the error-free bit sequence. Preferably the resulting physical marks comply with the specified restrictions for the physical marks, so this ensures reliable operation of the reading and decoding process.

Figure 2 shows a logical map of the registration area of a copy-protected record carrier. The registration area is divided into addressable sectors from the top at address 00 to address MAX. The first area 21 may be a pre-entry area or space, such as the second area 2 of silence on a CD. The second area is a system area 22, which comprises system information about the contents of the disk, such as the PVD (Primary Volume Descriptor) on a CD-ROM. The remaining part of the disk is available for user data, such as important information and directory files. The user's data area can be subdivided into several-areas, subdivision which is free and is not limited to the map shown in Figure 2. In this map the remaining area comprises a third area 23 comprising user files 28, one fourth area 24 that does not comprise user data, and a fifth area 25 that again comprises user data. According to the invention, the fourth area 24 comprises a filling area 26. The filling area 26 has sectors with errors 11 indicated by the x and sectors without errors 12, sectors with errors which comprise the logical errors and constitute the pattern of mistakes. The filling area 26 can comprise a large number of sectors, for example 20 Mbytes, and can cover substantially all the registration area not covered by the important information. This has the advantage that, when the presence of the error pattern has to be verified, each time a small number or only one of the sectors with errors can be selected from the large number available in the filling area. A malicious person trying to intercept the verification will not see a recurring test of one or a few specific sectors, but most of the different sectors - it will be read from a large address range - to detect the presence of logical errors. This will effectively prevent the malicious party from designing simple interception means to falsify the read output of a sector. One more advantage can be achieved if the writable disk containing the illegal copy has a smaller data capacity than the pressed disk. For example, in most CD-ROMs a large part of the capacity is not used, but it can be filled completely by the filling area without increasing the cost of manufacturing, while CD-Rewritable or CD-Rewritable have a capacity less than a CD-ROM filled to its maximum capacity. In that case, not all the information (user information and filling area) can be transferred? to the illegal copy. In one embodiment, the additional access control information is comprised in the system area 22 or in some other area not directly accessible in a standard reading device, such as the entry, exit, or prior space area. Additional access control may be an indicative license code for the party making use of the system for copy-protected record carriers, and / or may be indicative of the error pattern, for example, to be used as seed in an algorithm that generate the error pattern. Figure 3 shows an error correction unit used in the CD system, called CIRC (Cross-Interleaved Reed-Solomon Code). A detailed description of the error correction rules CIRC can be found in GB 2076569 (PHQ 80009), document D2, the decoder in it is described with Figure 7. In Figure 3 the entry (on the left) is a block of 32 bytes stored consecutively on the record carrier, indicated by the column bytes numbered 0 to 31, comprising twelve bytes of data 0-11, four bytes of error correction C2 12-15, again twelve bytes of information 16 -27 and four bytes of error correction Cl. Odd bytes are delayed by a cycle in a first delay unit 31, and the resulting erroneous words of 32 bytes are corrected in their errors by the unit Cl 32. The unit Cl can correct a byte error and detect all the errors of byte 2 and 3, while the errors of byte 4-32 are detected with a very low failure rate. If the Cl unit detects an incorrigible error, it will indicate that all bytes are not reliable. The output of the unit Cl is delayed by a second delay unit 33, delaying byte 0 by 27 * 4 = 108 blocks, byte 1 by 26 * 4 = 102 blocks, etc. The output of the second delay unit 33 constitutes a second erroneous word, whose errors are corrected by the unit C2. Unit C2 usually corrects up to 2 errors, but can correct up to 4 bytes by suppression if unit Cl indicates all detected errors. The output of the unit C2 is demixed by the demixing unit 35. The functions described are the complement of the inverse functions in the encoder, all functions are well known from the CD system and are described in detail in document D2. According to the invention a logic error results from bit errors that are incorrigible, therefore bit errors can be present in the input blocks that accumulate up to at least 2 but preferably 3 or more errors in the words wrong at the input of the unit Cl. Also at least 3, but preferably at least 5 errors must be present in at least one second erroneous word at the input of the unit C2. For 5 errors in a second erroneous word, at least 17 output blocks marked with consecutive errors of Cl, which have errors and a group of 5 bytes of information consecutively numbered, are required. For example, errors in byte 0 in block 0 will accumulate in the input of C2 with errors in byte 2 in block 8 and errors in byte 4 in block 16. To create a group of logical errors Within a specific data unit, such as a sector in the CD system, more bit errors than the previous minimum number of 5 errors in 17 consecutive blocks should preferably be applied. An additional error correction layer, such as the one used in the CD-ROM to correct errors within a sector, can correct some incorrigible logical errors by the previous error correction rules. Therefore, a larger number of logical errors should be included. One mode achieves a safe margin without risk of expanding errors over a large area that has errors in all first or second 12 bytes of information consecutively numbered. Such errors will be diffused due to the second delay unit in 12 * 4 = 48 blocks and 1 additional block due to the first delay unit, and having 24 consecutive blocks with errors, in 48 +1 + 24 = 73 blocks. As a block comprises 24 bytes of information, it affects 73 * 24 bytes = 1752 bytes, which are also within a sector of the CD-ROM format (2352 bytes) as long as the blocks with errors are placed within that sector . The sector comprises 98 blocks, so that a maximum of 49 consecutive blocks can have errors without affecting neighboring sectors. It should be noted that they have to apply errors to all the bytes in the blocks, which would be the case if a complete area of the disk is provided with errors, for example, physically damaging the area, it is not a solution to create logical errors. Such errors will be dispersed at least in 28 * 4 + 1 = 113 blocks, and with a minimum of 17 blocks with consecutive errors in 130 blocks. The number of bytes affected is 130 * 24 = 3232, which is more than one sector. When errors that are incorrigible in the unit Cl and / or C2 are detected, the bytes will not be changed, but they will be marked as errors. Bit errors in the information bits result in bit errors propagating to the output of the error correction unit, while the error correction bits are used in the error correction unit and will not be visible in the output. Therefore, in a preferred embodiment, bit errors are present in the information bits and not in the error correction bits. In addition, bit errors will not be propagated by de-interleaving to attached sectors, which remain free of errors. Therefore, in a preferred embodiment, the part of the bit sequence corresponding to sectors without errors attached to sectors with errors, does not substantially comprise bit errors. Although some bit errors can be corrected in the attached sectors, there is a greater risk of incorrigible errors if additional errors, for example caused by dust, are combined with bit errors. In that case a sector without errors can be falsely classified as a sector with errors. Although the bit errors accumulate in a few selected erroneous words and therefore directly affect only the selected places, a good number of symbols (= bytes) will be marked by the unit Cl as unreliable (in fact all the symbols in all Cl words have 2 or more erroneous bytes). The error unit C2 will first calculate a syndrome to detect any possible errors, which indicates whether errors are present. Additional calculations will indicate the number of errors and possibly indicate which symbols need to be corrected. Several methods can be used for the correction, such as errors in only 1 or 2 symbols can be directly corrected, and to correct from 2 to 4 erroneous symbols the marks of the previous Cl unit can be used to indicate which symbol to replace (correction by elimination). Usually the C2 unit will not use the Cl marks if it detects 0 or 1 errors. Therefore the large number of symbols marked, but not changed, will not be noticed or classified as errors by unit C2. Preferably, for a sectorized format of symbols marked by Cl, they should be as much as possible within the sector with errors selected, since additional errors caused by dust, etc., can cause incorrigible C2 errors in combination with the symbols marked of Cl. For a detailed description of the error processing rules, reference is made to D2. In a different embodiment using the double-layer error coding C2 / C1, errors are introduced during coding after the coding step of C2 but before the * coding step of Cl. Consequently, during decoding no errors are detected in the Cl decoder, and the marking of Cl symbols does not occur. However, in the decoding step of C2, errors that are incorrigible appear. All errors can be easily controlled to be within the sector, since interleaving and de-interleaving occurs after the coding of C2 and before the decoding step by C2.

Alternatively, a combination of Cl and Cl errors can be used. The invention can be applied in systems that use different error correction rules, such as the DVD. A correspondence pattern can be found of bit errors that counteracts de-interleaving according to the above description. In additional applications a more sophisticated method of error correction may be the repeated application of the error correction rules by first inserting the output of the first error correction process as the encoder and secondly deinterleaving and applying the error correction rules again. Since some errors can be corrected in the first process such a second error correction process can correct additional errors. To prevent a method from correcting the logical errors, preferably the frequency and placement of the bits of the bit errors is such that they are incorrigible in each error correction layer. Figure 4 shows a bit error pattern for the CIRC error correction rules as described in Figure 3. Bit errors are designed to accumulate in the wrong words of Cl as well as in the wrong words of C2, in both cases up to 5 errors. The error pattern can be moved to other information bytes (0-11, 16-27), but it should cover only the information bytes and not the error correction bytes. In Figure 4 the errors in the bytes are indicated by the letters a, b, c, d, e, while the bytes without errors were not marked. To affect 20 consecutive Cl words, 21 blocks with errors have been provided, the odd bytes starting a block before and the even blocks stopping a block afterwards to compensate for the first delay unit 31. Due to the delays in the second delay unit 33 the errors marked by the same letter will accumulate in the words of C2, so that 4 consecutive C2 blocks will have 5 errors Xe ", in the following 4 blocks of C2 5 errors d", up to at least 4 blocks of C2 with errors ^ a. "Errors will not be compensated because in each wrong word of Cl or C2, 0 or 5 errors will accumulate.This scheme of errors can easily be extended to more errors and more consecutive erroneous words as required or by other rules of It can also be applied a few times within a sector, to avoid any process of correction of synchronization errors, later to correct the logical errors. with Figure 3, Cl corrector has a probability of 100% detection of erroneous words 2 and 3, while occasionally be falsely corrected 4-32 can errors. Therefore, a preferred modality that uses Cl errors has only 3 accumulated errors in the Cl words. An effective error pattern that has 3 CI errors can be derived from Figure 4 by applying only errors a, b, c and omitting errors d and e. Alternatively instead of having 4 consecutive CI blocks with errors, only the first of each quad can be provided with errors, resulting in a block error of C2. The error pattern that begins in byte 0 as shown in Figure 4 results in almost all bytes marked, but without changing Cl preceding the erroneous bytes, the first is byte 27 of block 2 that precedes the bytes. logical errors for 108 blocks. Only a few bytes marked, but not changed, will follow after the logical errors, that is, the last one is byte 0 of block 21 delaying 16 blocks. Preferably synchronizing the affected blocks with the sectors, the marked bytes, but without changing will be placed within the sector with errors, for example, the error pattern of Figure 4 should be applied to the end of the sector with errors. Correspondingly, when errors are applied to the bytes with the highest numbering (for example 23-27), most of the bytes marked but not changed will be delayed behind the logical errors. Figure 5 shows an arrangement for retrieving the information of a record carrier protected against copy 1 and processing the information. The array comprises a reading unit for reading the bit sequence of the record carrier 1. The reading unit comprises a read head 41 for scanning the track and generating a read signal corresponding to the physical marks on the record carrier , and a translator unit 42 for translating the read signal into the bit sequence, for example an EFM decoder for decoding in a CD system. The bit sequence is coupled to an error correction unit 43 to recover the information and correct possible errors, for example, the CIRC corrector in a CD system. The retrieved information is coupled to the access control means 47 to control access to the information. The access control information is available to be further processed at the output 48 of the access control means 47. During reading the read head 41 is placed on the track by a servo unit 44 of the usual type, while the carrier The register is rotated with a motor unit 45. The information reading is controlled via the controller 46, which controller controls the motor unit 45, the servo unit 44 and the "errors 43" correction unit, and is arranged to receiving read commands, for example via an interface with the access control means 47. The access control means 47 can be implemented in integrated circuits in a reading device which also comprises the above reading means. that the information will not be released in the output 48 if the respective access control information is not present in the record carrier. and access can be implemented alternatively in a computer connected via an interface to a standard reading device, such as a CD-ROM driver. In the computer the access control means can be built on an interconnection board or they can be made by a program running in a central processing unit. The program for performing an access control can be delivered to a user in the copy-protected record carrier. This is advantageous, since no delicate equipment is necessary and that the user has all the necessary means to access the information protected against copy incorporated in the record carrier. The access control according to the invention will be carried out as follows. The means of access control will first obtain the access control information indicative of the error pattern. This access control information may be a pattern stored in a record carrier, for example, the license code described with Figure 2, or an access code supplied via a network, by example, the Internet or a paper. In an embodiment the error pattern can be generated using an initial value and a predefined algorithm, the initial value is stored in the record carrier against copy. Second, the presence of errors must be verified It is logical to make sure that the disk is an original disk, protected against copying and not an illegal copy. The access control means will select one or more places with errors on the record carrier, or sectors with errors if the record carrier has a format with addressable sectors, each place with errors should have a logical error according to the error pattern . Third, the presence of an error is verified by reading the place with selected errors. Since the reading device will generate an error message on the interface in the event that a sector read comprises incorrigible errors, the presence of logical errors can be detected effectively. Since a copy will not include logical errors, the copy will be rejected and access to the information will be denied. Preferably, a few places with random errors are selected from a large number of places with errors available on the record carrier, for example, in a dedicated fill area to understand the error pattern that has sectors with errors and sectors without errors. Alternatively, sectors with errors can be interconnected with valid sectors comprising normal user information. To achieve a rapid response for access control to take place, preferably only one sector is selected and read. In practice reading a sector that has incorrigible errors can only cause a delay of a few seconds, which delay is caused by the reading device that tries to read the sector a few times. Such retries are standard in practice to improve the likelihood of successful information retrieval in the event of dust or scratches. The error pattern can be verified additionally by selecting at least one place without errors, but not all places without errors, places without errors which should not have a logical error according to the error pattern, and verifying the absence of an error by reading the place without errors selected. Since the reading of a sector without errors will be very rapid, for example, 0.2 seconds, a larger number of sectors without errors are preferably selected and read, for example, 10 to 40. The sectors without errors are preferably selected via a process of random selection of all sectors without errors available. In one embodiment the content of the sectors without errors can be verified, for example, by including a verification value in such a sector that must be derived from the sector number and the license code by means of a predetermined encryption or coding algorithm. In an additional mode, sectors are selected and verified without errors before and after a sector without errors has been selected. This has the advantage that, for example, 21 to 81 apparently randomly selected sectors are read, of which only one comprises an error. This has the advantage that a malicious party will have a harder time trying to imitate this verification process. Since the error pattern according to the invention is designed to accumulate all the bit errors in the sectors with errors without affecting the attached sectors, some sectors with errors attached to sectors with errors should preferably be selected. This will most likely expose illegal copies damaged in certain areas to the imitation of the error pattern. The access control for a computer program can be done as follows. The information carrier contains the computer program, while some essential data are included in the access control information. The computer program can be encrypted or encoded in itself, while a small boot program takes the place of the program and controls access to the main program. The access control information may be, for example, a decoding key, a serial number or an access code or, possibly, a small part of the program code (a subroutine, object or module). Due to the need for such essential data, the program can only work well if both the information and the access control information are available. The boot program can read the access control information from a hidden location on the record carrier, such as the license code included in system area 22 (see Figure 2) and / or additional access data files . Subsequently, the presence of the error pattern can be verified as described above. Figure 6 shows a schematic diagram for protecting against copy a record carrier. In the following text it was assumed, that the invention was applied under the control of a grantor. In the first step 61 the editor creates a new program title 71. The editor does not need to make any changes to the program to use the invention. The system can be fully developed and tested first. In the second step 62 the editor encrypts or encodes the main executable file (for example for a DOS or Windows system) to create a set of encrypted or coded files 72. Using a utility program provided by the grantor the editor encrypts this using a number of license as the encryption or encryption key. Unique license numbers are granted by the grantor for each product produced. As an example, if the title of the program to be protected has a program called foo.exe the encryption process encrypts it, renames it as foo.icd and includes a new program, provided by the grantor which renamed it as foo.exe . This program is then responsible for carrying out the security checks, verifying the license number and putting the encrypted program (foo.icd) into service. In a third step 63 the editor creates an image file 73, such as an ISO 9660 Image, 5 of the set of encrypted files 72. Using an Authorized CD package the editor creates the image file 73 of its complete program title in a hard disk controller. In a fourth step 64 the image file 73 is modified to create all the content 74 of the copy protected copy carrier, which has a logical map as described in Figure 2. A second utility program provided by the grantor modifies the image file 73 by adding a license structure that includes the license number to the system area 22. The file image 73 is further modified to fill the size of the image to include the fill area. The total duration is preferably more than 74 minutes (333,000 sectors). The license structure maintains a reference to the start and end sectors of the filling area. In the area of the sectors will be good or bad and the distribution of the sectors will be determined by a pseudo-random process, which can be initiated with the license number. In a fifth step 65 the image file is processed to create a master disk 75, for example, by a Headquarters. The image file 74 is sent to the Head Office on a magnetic tape or other suitable means. Using a modified Laser Beam Registration program according to the invention, a master disc or pattern 75 is produced. The Laser Beam Registration program 5 makes use of the license structure to determine which sectors in the filled area are marked as bad and which as good. The ratio of sectors marked as good can be fixed, for example, of approximately 50%. The errors are applied according to the patterns of 11O errors described above with Figure 4. In a sixth step 66, copy-protected record carriers 76, such as CD-ROM, are produced duplicating master disk 75. The error pattern is transferred to each disk in this step. 15 Although the invention has been explained by one modality using the CD-ROM as "example that has the I CIRC error correction rules, it should be clear that other record carriers, magnetic or optical tape, etc. can be used. in the invention, if such carriers registry includes information protected by the protection rules against predefined errors. For example, a high-density DVD disc also uses an error correction process. Although the invention has been described with reference to the preferred embodiments thereof, it must be understand that these are not limiting examples. Thus, different modifications may become apparent to those skilled in the art, without departing from the scope of the invention, as defined by the claims. For example, by applying error patterns in data protected against errors transmitted via a network such as the Internet access control may be provided according to the invention. In addition, the invention depends on each and every feature or combination of novel features.

List of related documents (DI) EP-0545472 (PHN 13922) Closed information system with protection against physical copy (D2) GB 2076569 (PHQ 80009) The detection and correction of CIRC errors.

• (D3) WO 95/03655 PROM CD encryption or coding system.

Claims (21)

CHAPTER CLAIMEDICATORÍO Having described the invention, it is considered as a novelty and, therefore, the content is claimed in the following:

1. A method for protecting against copying a record carrier having information stored therein, according to the rules for formatting and correcting predetermined errors, comprising the steps of (a) creating an image file comprising important information, (b) ) generate access control information to control the access to important information, (c) produce a master bearer or pattern that depends on the image file and access control information, which comprises the steps of creating a sequence of bits applying the rules to format and correct errors to the image file and translate the sequence of bits into a physical pattern of marks, and (d) multiply the record carrier using the master carrier or pattern, characterized in that in step (c) the bits in the bit sequence are changed according to the control information - of access to constitute logical errors which can not be corrected gone by the rules of correction of errors and that constitute a pattern of errors.

2. The method for protecting against copy a record carrier according to claim 1, 5 characterized in that at least the important information is encrypted or encoded depending on the access control information.

3. The method for protecting against copy a record carrier according to claim 1, characterized in that at least some of the access control information is included in the image file and the error pattern is generated depending on the information Access control included.

4. 'A copy protected record carrier 15 having a sequence of bits stored therein, representing information according to the rules for formatting and correcting predetermined errors, the information comprises important information and access control information to control access to important information, Characterized in that the bit sequence comprises bit errors that constitute logical errors, which can not be corrected by the error correction rules and which constitute an error pattern representing at least part of the access control information.

5. The record carrier protected against copying according to claim 4, record carrier which is divided into addressable sectors, characterized in that the record carrier comprises a filler area, filler area which comprises sectors with errors and sectors without errors, sectors with errors which comprise the logical errors and constitute the error pattern.

6. The copy-protected register carrier according to claim 5, characterized in that the part of the bit sequence corresponding to sectors without errors that are attached to sectors with errors does not substantially comprise bit errors. 1 .

The copy protected copy carrier according to claim 5, characterized in that, although the record carrier has a predetermined information storage capacity of which the important information covers a part, the filling area substantially covers the remaining part of the information. the storage capacity of information.

8. The copy-protected register carrier according to claim 4, characterized in that, although the bit sequence comprises information bits and error correction bits, the information bits comprise the bit errors.

9. The copy protected copy carrier according to claim 4, characterized in that the bit errors are localized so that they accumulate in at least one erroneous word, which can not be corrected by a wrong word correction rule during the reproduction.

10. The copy protected copy carrier according to claim 9, characterized in that the record carrier is a CD, the error correction rule is layer C2.

11. The copy protected copy carrier according to claim 9, characterized in that the bit errors are located so that they accumulate by deinterleaving, deinterleaving which is part of the rules for formatting and correcting errors.

12. The copy protected copy carrier according to claim 9, characterized in that the bit errors are located so that they accumulate in at least one second erroneous word, which can not be corrected by a second rule to correct words wrong.

13. The copy protected copy carrier according to claims 11 and 12, characterized in that the record carrier is a CD, the erroneous word correction rule is the C2 layer and the second erroneous word correction rule is the Cl layer of the rules to correct CD errors.

A method for detecting access control information in a copy protected record carrier according to any of claims 4 to 13, characterized in that the method comprises the steps of selecting at least one place with errors, but not all places with errors, places with errors which must have a logical error according to the error pattern, and verify the presence of an error by reading the place (s) with selected errors.

15. The method for detecting access control information according to claim 14, characterized in that the method further comprises the steps of selecting at least one place without errors, but not all places without errors, place (s) without errors which should not have a logical error according to the pattern of errors, and verify the absence of an error by reading the place (s) without selected errors.

16. The method for detecting access control information according to claim 14, characterized in that at least one place without errors is selected which is next to a place with errors.

17. The method for detecting access control information according to claim 14, characterized in that the method comprises a step of recovering at least some of the access control information indicative of the error pattern of the important information before selecting places.

18. The method for detecting access control information according to claim 14, characterized in that, although the record carrier is subdivided into addressasectors, the presence or absence of an error in a location is verified by reading the respective sector and generating an error message when an incorrigierror is detected during the reading of the sector.

19. The copy protected copy carrier according to claim 4, characterized in that the record carrier comprises a program for executing the method according to any of claims 14 to 18 in a computer system.

20. A recovery arrangement for recovering information from a copy-protected record carrier according to any of claims 4 to 13, the arrangement comprises reading means for reading the record carrier, the reading means comprising a reading unit for extracting the sequence of bits stored in the record carrier and an error correction unit for processing the bit sequence, characterized in that the array comprises access control means for controlling access to information, access control means which are incorporate to detect access control information by selecting at least one place with errors, but not all places with errors, place (s) with errors which must have a logical error according to the pattern of errors, and verify the presence of an error by reading the place with errors selected via the reading means. The recovery arrangement according to claim 20, characterized in that, although the record carrier is divided into addressasectors, the reading means comprise a control unit for controlling the reading of a sector and generating an error message when an incorrigierror is detected.