WO2006104119A1

WO2006104119A1 - Data recording device, and data deleting method for use in the data recording device

Info

Publication number: WO2006104119A1
Application number: PCT/JP2006/306217
Authority: WO
Inventors: Yutaka Yamanaka
Original assignee: Nec Corporation
Priority date: 2005-03-29
Filing date: 2006-03-28
Publication date: 2006-10-05
Also published as: JP2008181574A

Abstract

A data recording device selects plural pieces of data corresponding to encryption key information in an ECC block formed in an optical disk, and forms, at the position of a recording bit string corresponding to the individual selected data pieces, an overwrite bit string different in format from that recording bit string. Thus, the encryption key information can be stably deleted without any instability in a servo.

Description

Specification

Data recording apparatus and data erasing method used in the data recording apparatus

The present invention relates to a data recording apparatus and a data erasing method used for the data recording apparatus, and in particular, such as a CD-R (Compact Disc-Recordable) and a DVD-R (Digital Versatile Disc-Recordable). The present invention also relates to a data recording apparatus suitable for protecting the copyright of a write-once recording medium on which data is recorded only once, and a data erasing method used in the data recording apparatus.

Background art

An optical disc is a recording medium on which data is recorded by forming minute pits on a disc substrate. As such an optical disk, following a read-only ROM (Read Only Memory) medium in which a recording bit string formed by embossed pits is formed in advance, in recent years, a CD-R (optical disk on which data is recorded only once is used. Compact Disc-Recordable) and DVD-R (Digital Versatile Disc-Recordable) are widely used. These optical disks are sometimes called write-once optical disks. In a write-once type optical disc, a spiral group for tracking is formed on a disc substrate to form a recording track, and a multi-layer recording layer made of an organic material or the like is formed on the recording track. In this recording layer, a high-power laser beam is condensed and partially altered, so that a recording bit string is formed by pits including a mark portion and a space portion, and data is recorded.

[0003] An optical disc on which data is recorded has a data format with the same configuration as that of a ROM medium on which embossed pit rows are formed, and servo signals with almost the same characteristics can be obtained. Easy to play. For example, in DVD-R, the recorded data is converted into a format in which additional information such as an ID and an error correction code is added to the original data, and the optical disk medium as a series of continuous recording bit strings. To be recorded. At this time, since error correction processing is performed for each fixed amount of data, the length of the amount of data becomes the basic unit of the recording bit string, and this is called a ¾ CC block. . The format of the recorded data is the same as the DVD-ROM recording format.

FIG. 10 is a diagram showing an example of a recording format on an optical disc that can be recorded.

In this recording format, as shown in FIG. 10, a recording track 2 having a spiral group structure is formed on the optical disc 1, and data is recorded along the recording track 2. In the inner periphery of the optical disc 1, predetermined information indicating the type of the disc and the like is often recorded in advance as a lead-in area at the time of manufacture. As shown on the right side of the figure, the recording bit string on the recording track 2 is composed of ECC blocks 3 having a predetermined length. Each time the recorded bit string of ECC block 3 is read, the original data is reliably restored by error correction processing. Such a recording format is disclosed in, for example, Japanese Patent Application Laid-Open No. 2004-24104.

[0005] By the way, in recent years, in order to protect the copyright of copyrighted data such as movies and music, a technique for preventing unauthorized copying using an optical disk on which data can be recorded has been proposed and used. It has become. In such a technique, the original data is mainly subjected to encryption processing using an encryption key having a length of about 40 to 128 bits, and is recorded on the optical disc. On the reproduction side, after the encryption key is obtained by a predetermined means, the recorded data is read out, and the original data is reproduced using the encryption key. Encryption keys are often used in combination, rather than one, depending on the purpose.

[0006] Conventionally, as this type of technology, for example, there are those described in the following documents.

Japanese Unexamined Patent Publication No. 2000-163883 discloses a technique for providing a recording area for recording additional information on an optical disk in order to prevent unauthorized duplication and unauthorized use of software. If necessary, the additional information includes encrypted data that is prohibited from being output from the recording / playback device, for example, management information to prevent unauthorized copying or unauthorized use of software. The In addition, control data indicating whether output prohibition information is included in the additional recording information is recorded in the recording area. By using this control data, output from the recording / reproducing apparatus for which output should be prohibited is suppressed, and alteration of the data is prevented.

[0007] Japanese Unexamined Patent Application Publication No. 2001-14794 discloses a digital signal from a read-only optical disk to a recordable optical disk. Disclosed is a recordable optical disc that makes tarcopy impossible. In the lead-in area of this recordable optical disc, a control data block including a pre-pit recording area in which fixed data including invalid scramble key data is recorded in a form that cannot be erased in advance is prepared. In the pre-pit recording area, scramble key data is recorded, and an error that makes error correction impossible is inserted in advance in a part of the inner code recorded in the area.

[0008] Furthermore, “Expanding copyright protection space from DVD”, Naoshi Yamada, Nikkei Electronics, Nikkei Business Publications, Inc., August 13, 2001, P.143-153, CSS (Content Scrambling Syst em) It describes copyright protection technology by encryption processing used in current DVD products such as CPRM (Content Protection for Recordable Media).

An example of such encryption processing is shown in FIG.

That is, the original data 11 is recorded on the optical disc 1 as the recording data la after the encryption process 12 is performed. In this case, the original data 11 is converted into a recording bit string corresponding to the recording format of the optical disc 1. One of the encryption keys used for encryption process 12 is a disk-specific encryption key lb. The encryption key lb is recorded in advance in the lead-in area or the like when each optical disk is manufactured. Use this encryption key lb

In this case, there is an advantage that even if the same recording bit string is copied to another optical disk, the original data 11 cannot be reproduced because the encryption key unique to the disk is different.

In addition, the data unique encryption key 13 is generated based on information attached to the original data 11 or information given in advance to the management authority of the copyright protection technology to the optical disc device. It is obvious that the data is legitimate data in accordance with the protection technology, and information obtained from the management organization of the copyright protection technology cannot be obtained and reproduced on the optical disk device. The device-generated encryption key 14 is an encryption key that is randomly generated by the optical disk device every time a series of data requiring copyright protection is recorded. When the same original data is recorded on the same optical disk However, it is possible to change the encryption key conditions. The data-specific encryption key 13 and the device-generated encryption key 14 are recorded on the optical disk 1 as encryption key recording data lc by an appropriate process, and passed to the reproduction-side optical disk device. [0010] As one advantage of using the device-generated encryption key 14, when using a rewritable optical disc, the entire recording data is erased by overwriting the encryption key recording data lc with another data. It is mentioned that the same effect as that obtained can be obtained. This eliminates the need to erase all recorded data when performing the process of moving the recorded data to another optical disc for each copyright (generally called the “move function”). In addition, even when using a write-once optical disc, the encryption key information can be obtained by forcibly overwriting the ECC block in which the device-generated encryption key 14 is recorded with an ECC block generated with other data. A method of erasing can be considered.

[0011] However, if a recording bit string conforming to the recording format is formed at a recording track position that has already been recorded, the write-once optical disk information is erased as soon as the servo becomes unstable during playback on a write-once optical disc. There is a problem that is not performed stably. This is because the ratio between the mark portion and the space portion after recording is normally assumed to be substantially equal, whereas the ratio of the mark portion increases due to overwriting. Also, if overwriting is performed, normal reproduction of data including address information becomes impossible, so access is not performed correctly, and ECC block boundaries are not properly determined, and before and after overwriting. There is also a problem that some data may not be reproducible.

Disclosure of the invention

[0012] The present invention has been made in view of the above-described circumstances, and the encryption key information is recorded on the write-once recording medium V and the encryption key information is stably erased. The purpose is to provide a data recording device!

In one aspect of the present invention, a data recording apparatus that records data on a recording medium by forming pits corresponding to a recording bit string on a recording track of the recording medium is a recording that generates recording data. A data generation unit; an overwrite data generation unit that generates an overwrite pattern; and a data recording unit that records the recording data or a recording bit string corresponding to the overwrite pattern on the recording medium. The recording data generation unit forms a sector by adding header information including at least an address to a fixed-length data block, and the plurality of sectors are arranged in a two-dimensional matrix, and each row direction and each column of the two-dimensional matrix. A two-dimensional program with ECC (Error Correcting Code) attached in the direction. An ECC block is configured using a mouth duct code, and recording data is generated by modulating the ECC block while inserting a synchronization code at a fixed interval. The overwrite data generation unit selects a plurality of data in the ECC block, and an overwrite bit string having a format different from that of the record bit string is located at a position of the record bit string corresponding to each of the selected plurality of data. Generate the overwrite pattern to be written.

[0014] Preferably, each of the selected data includes a part or all of the encryption key information generated when the recording data is generated.

[0015] When the encryption key information is stored in the header information of a predetermined sector, the overwrite data generation circuit corrects the encryption key information by forming the overwrite bit string. It is preferable to generate the overwriting pattern so that it becomes impossible.

[0016] In addition, the overwriting data generation circuit may form the overwriting bit string at a position of a recording bit string other than the recording bit string corresponding to the address and the synchronization code in the formed recording bit string. Preferably, the overwriting pattern is generated.

When the recording bit string and the overwrite bit string are recorded on the recording medium as a pit string composed of a mark part and a space part, the overwrite data generation circuit is configured to generate a ratio of the mark part of the overwrite bit string. It is preferable to generate the overwriting pattern so that is equal to or less than a predetermined value. In this case, it is preferable that the overwrite data generation circuit generates the overwrite pattern so that a ratio of the mark portion of the overwrite bit string is 20% or less.

[0018] Further, the overwrite data generation circuit may perform the overwrite so that the overwriting bit string is formed so that an error-correctable state occurs in a specific column part or row part with respect to the ECC block. U, prefer to generate patterns.

[0019] In another aspect of the present invention, a certain data erasure method includes adding a header information including at least an address to a fixed-length data block to form a sector, and arranging the plurality of sectors in a two-dimensional matrix. Using a 2D product code with ECC (Error Correcting Code) attached to each row direction and each column direction of the 2D matrix The ECC block is used for a data recording apparatus that records a recording bit string corresponding to recording data generated by modulating the ECC block while inserting a synchronization code at a fixed interval. The data erasing method includes a step of generating an overwrite pattern and a step of recording a recording bit string corresponding to the overwrite pattern on the recording medium. The step of generating the overwrite pattern includes a step of selecting a plurality of data in the ECC block, and an overwrite having a format different from that of the recording bit string at a position of the recording bit string corresponding to each of the selected plurality of data. And a step of generating the overwriting pattern so that the bit string is written.

[0020] Since the present invention selects a plurality of data in the ECC block and forms an overwrite bit string having a format different from that of the recording bit string at the position of the recording bit string corresponding to each selected data. The plurality of data can be erased stably. In particular, when encryption key information in an ECC block configured on a recording medium is selected as a plurality of data, the encryption key information is erased without causing servo instability. Can be performed stably.

Brief Description of Drawings

FIG. 1 is a block diagram showing an electrical configuration of a main part of a data recording apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing a data structure of a sector.

FIG. 3 is a diagram showing a two-dimensional matrix constructed by adding an error correction code using a plurality of sectors in FIG. 2.

FIG. 4 is a diagram showing a modification of the two-dimensional matrix of FIG.

FIG. 5A is a diagram showing sector data obtained by cutting out the modified two-dimensional matrix force of FIG.

FIG. 5B is a diagram showing sector data in which the modified two-dimensional matrix force of FIG. 4 is also cut out.

FIG. 6A is a diagram showing data in which the sector data force is also converted into a recording bit string.

FIG. 6B is a diagram showing data in which the sector data force is also converted into a recording bit string. FIG. 7A is a diagram showing an overwrite position.

FIG. 7B is a diagram showing an overwrite position.

FIG. 8 is a diagram showing an overwrite position.

FIG. 9 is a diagram showing another overwrite position.

FIG. 11 is a diagram showing encryption key processing.

BEST MODE FOR CARRYING OUT THE INVENTION

The data recording device of the present embodiment is an optical disk device 20, and includes an encryption circuit 21, a recording drive circuit 22, a spindle 23, an optical head 24, a data reproduction circuit 25, and an overwrite data generation circuit 26. It is composed of The encryption key circuit 21 encrypts the original data 46, converts it into a predetermined recording format, and outputs recording data 41.

In the present embodiment, the encryption key circuit 21 forms a sector by adding header information including at least an address to a fixed-length data block constituting the original data 46. Furthermore, the encryption circuit 21 uses a two-dimensional product code in which the sectors are arranged in a two-dimensional matrix and ECC (error correction code) is added in each row direction and each column direction of the two-dimensional matrix. Configure ECC block. Furthermore, the encryption circuit 21 generates recording data 41 by modulating the configured ECC block while inserting a synchronization code at fixed intervals.

The recording drive circuit 22 generates a drive signal 43 corresponding to the recording data 41 given from the encryption circuit 21 or the overwrite pattern 42 given from the overwrite data generation circuit 26, and the drive signal 43 Is supplied to the optical head 24.

The spindle 23 drives the optical disc 1 to rotate. The optical disc 1 is, for example, a CD-R (Compact Disc-Recordable) ^ DVD-R (Digital Versatile Disc-Recordable), and a recording bit string is formed on the recorded track by a pit having a mark portion and a space portion. This is a write-once type optical recording medium in which data is recorded only once, and the optical head 24 generates an optical signal in response to the drive signal 43 output from the recording drive circuit 22 for recording. A bit string is recorded on a write-once optical disc 1. As a result, a recording bit string corresponding to the recording data 41 or the overwrite pattern 42 is recorded on the write-once optical disc 1. The optical head 24 writes the recording bit string on the optical disc 1, reads the recorded recording bit string, and outputs a reproduction signal 44 corresponding to the read recording bit string. The data reproduction circuit 25 generates a reproduction signal recording bit string 45 that is digital data from the reproduction signal 44. The overwrite data generation circuit 26 generates an overwrite pattern 42 in accordance with the data of the recording bit string 45 output from the data reproduction circuit 25. As described above, an overwrite operation is performed on the optical disk 1 via the recording drive circuit 22, and in this embodiment, the overwrite data generation circuit 26 selects a plurality of data in the ECC block constituting the recording bit string, and An overwrite pattern 42 is generated so that an overwrite bit string having a format different from that of the recording bit string is formed at the position of the recording bit string corresponding to each selected data.

[0026] Each of the selected data includes a part or all of the encryption key information when the data is encrypted. The encryption key information is stored in the header information of a predetermined sector, and the overwrite data generation circuit 26 makes the encryption key information uncorrectable by forming an overwrite bit string. The overwrite data generation circuit 26 also overwrites the overwrite pattern 42 so that the overwrite bit string is formed at the position of the record bit string other than the record bit string corresponding to the address and the synchronization code among the record bit strings already formed on the optical disc 1. Is generated. The overwrite data generation circuit 26 generates the overwrite pattern 42 so that the ratio of the mark portion of the overwrite bit string is a predetermined value (for example, 20%) or less. In addition, the overwrite data generation circuit 26 generates an overwrite pattern 42 so that an overwrite bit string that causes an error uncorrectable state in a specific column part or row part is formed for the ECC block.

The processing contents of the data erasing method used in the optical disc device 20 of this example will be described with reference to FIGS.

In this data erasing method, a plurality of data in the ECC block configured on the optical disc 1 is selected, and an overwrite bit string having a format different from that of the record bit string is located at the position of the record bit string corresponding to each selected data. As a result, multiple data are deleted. That is, the original data 46 is converted into sectors having the structure shown in FIG. In this example, the header data with ID (4 bytes), IED (2 bytes), and RSV (6 bytes) is added to the head of the original data 46 of 2048 bytes from DO to D2047, and EDC ( Additional information (4 bytes) is added as data. All the data is arranged as a matrix of 172 x 2 bytes and 6 rows of matrix elements. At this time, the left half of the matrix element is element L, and the right half is element R. ID is mainly information including address, and IED is error correction code of the same ID. Therefore, in the sector of this structure, address information can be reproduced by reproducing ID and IED without reproducing other data of the ECC block. RSV is an area reserved for system use. EDC is a code that performs error checking of the entire data contained in a sector.

As shown in FIG. 3, a two-dimensional matrix configured by adding an error correction code using a plurality of sectors in FIG. 2 is composed of, for example, 32 sectors. “OL” in the column represents the element L of the 0th sector and the element R of the Oth sector of the “OR” force. In the odd-numbered sector, element L and element R are arranged with their left and right interchanged. In addition, a matrix of 6 × 32 = 192 rows is composed of 32 sector data. This matrix is divided in the row direction at the boundary between element L and element R, and a 10-byte error correction code PI is added to each data of 172 bytes of each row of element L and 172 bytes of each row of element scale. ing. For example, when a Reed-Solomon error correction code is added, error correction of up to 5 bytes and detection of error occurrence byte positions of up to 10 bytes can be performed in a total of 182 bytes of data. In this case, it is possible to add an error correction code to the entire 172 X 2 = 344 bytes of each line. If the amount of data exceeds 256 bytes, the calculation of the Reed Solomon error correction processing becomes complicated and time-consuming. Therefore, it is more advantageous to divide into half elements.

Similarly, in the column direction of the matrix, a 16-byte error correction code PO by the Reed-Solomon method is added to 192 bytes of each column. In this case, it is possible to correct an error at any position up to 8 bytes for 208 bytes of data in the column direction, and up to 16 bytes if an error position is specified. For the error correction code PO, an error correction code PI is added in the row direction. When playing back data, first, in the row direction Error correction and error position detection are performed, and then error correction in the column direction is performed. As a result, a higher error correction capability can be achieved than when error correction is performed on a column or row alone. In this embodiment, a method of adding error correction codes in a matrix form in this way is “two-dimensional product code” t.

Next, as shown in FIG. 4, the data of the error correction code PO is decomposed line by line and inserted immediately below the element L of each sector. As described above, when data including the error correction code PI and error correction code PO added to the elements of each sector is newly set as sector data, the data amount of all the sector data becomes a constant value.

FIG. 5A is a diagram showing the structure of the 0th sector data cut out from FIG. 4, and the even-numbered sector data all have the same structure. FIG. 5B shows the structure of the first sector data, and the odd-numbered sector data all have the same structure. As shown in these figures, when data is read along the matrix from left to right in the row direction and from top to bottom in the column direction,

ID + IED + RSV + D0 ~ D2047 + EDC

As shown, the data are arranged in the same order.

Next, each sector data is converted into recording bit data for recording on the optical disc 1.

(Modulated). In the present embodiment, for example, an ETM (Eight to Twelve Modulation, 8Z 12) modulation system that converts 1-byte data into 12 bit string data is used. In this case, even-numbered sector data is converted into a recording bit string as shown in FIG. 6A, and odd-numbered sector data is converted into a recording bit string as shown in FIG. 6B. That is, 182 bytes of data are converted into a bit string of 2184 (= 182 X 12) bits. This bit string is divided into two to generate two bit strings of 1092 bits each, and a SYNC pattern (synchronization code) consisting of 24 bit strings is added to the head of each bit string. The SYNC pattern includes a bit string pattern that does not appear in normal modulation. For example, in the case of ETM modulation, a pattern including a continuous mark portion or space portion of 13 clocks or more is used.

[0034] With this SYNC pattern, data breaks can be easily identified, and the same SYNC pattern can be used even when out-of-synchronization occurs when the playback signal clock cannot be detected in the middle of the data. It can be easily recovered by detecting the event. Furthermore, by making the SYNC pattern 47, 48 inserted at the beginning of the sector data a fixed pattern different from other SYNC patterns, the head position of the sector data can be easily detected, and the address information immediately after that is detected. Is easily replayed. A recording bit string obtained by recording 32 sectors of the recording bit string obtained by converting the sector data is an ECC block on the recording track. In some cases, a recording format in which a predetermined pattern is inserted between ECC blocks may be used.

Next, a method for deleting the encryption key that is the subject of the present embodiment will be described.

In this embodiment, a recording bit string for overwriting different from the recording format is formed. First, the ECC block in which the encryption key information is stored is overwritten and erased. In this case, if overwriting is performed using a recording bit string equivalent to a normal ECC block, the address and SYNC pattern may also be overwritten. Such overwriting prevents access using addresses and synchronized playback of data using the SYNC pattern. Therefore, a special overwrite pattern is generated.

[0036] For example, if the encryption key information is recorded in the area RSV in FIG. 2, the area RSV is not included in the original data 46! /, So it is recognized by the upper file system. Because it is a part, there is an advantage that the same encryption key information is not easily stolen. However, since the capacity of the area RSV is small, one encryption key information is stored across multiple sectors in the ECC block. That is, in the even-numbered recording bit string, the data in the area RSV is the portion of the recording bit 30 corresponding to RSV data in FIG. 7A. First, the recording bit string is overwritten in this portion to make the data unreproducible. In addition, in the odd-numbered recording bit string, the data in the area RSV becomes the portion of the recording bit 32 corresponding to RSV data in FIG. 7B.

[0037] However, this portion becomes the RSV data portion 34 in the arrangement of the two-dimensional product code shown in FIG. 8, but it is at most 6 bytes in the row direction and at most 15 bytes in the column direction. The two-dimensional product code makes it possible to correct errors. In order to exceed the error correction capability of the two-dimensional product code, data over the same column in element R is overwritten first. When using a Reed-Solomon error correction code, it is sufficient to cover 5 bytes or more. For example, select the additional data part 35 in Fig. 8 in the column direction. And do it. This corresponds to the additional data equivalent recording pits 31, 33 in FIG. In this case, as long as it is added in the same column, it may be another place, or data at discontinuous positions other than continuous data may be selected. Next, overwrite more than 5 bytes in the line direction. For example, if the data is overwritten in the column direction as shown in the re-added data portion 36 in FIG.

[0038] In addition, if the portion to be overwritten is not as close as possible within the sector, stable reproduction is performed in which it is difficult for out-of-serving to occur if synchronization is lost. The amount of data in the additional data portion 35 and the re-addition data portion 36 is determined based on the error correction capability of the error correction code. In addition, as the pattern of the recording bit string to be overwritten, it is about 72 recording bits long with a maximum of 6 bytes of data, so it is possible to make it impossible to reliably reproduce by overwriting all with the data of the mark part. is there. Also, for example, it is possible to make most data unreproducible even with a long mark length repetitive pattern, such as a 10-pit length mark portion and a 3-pit length space portion. In addition, in the recording bit string to be overwritten, the data portion (ID and IED) corresponding to the sector address and the portion of the SYNC pattern become a space portion, so it should not be overwritten substantially. In this way, stable data playback operation is possible even after overwriting.

[0039] When the encryption key information is recorded in the original data 46 of a specific sector, the recorded bit portion corresponding to that sector is overwritten so that error correction cannot be performed. Specifically, overwriting is performed so that data of 11 bytes or more is incorrect in the row direction. At this time, if the overwrite position is aligned in the column direction, an error will occur in data 6 in the column direction in one sector. If it is an even-numbered sector, recording is performed as shown in the overwrite recording bit 37 shown in FIG. In addition, select 11 or more rows in which errors occur in the same column direction in the matrix layout and perform overwriting. For example, if the encryption key information is included in the 0th sector and this sector is overwritten, the lines to be overwritten are changed to 2, 4, 8, 10, 12, 14, 16, 18, If the second line of each of the 20th, 22nd, 24th, and 26th sectors and the predetermined line are determined in advance, the pattern of the uncorrectable line that occurs during error correction in the line direction can be detected. Thus, the optical disk device 20 can reliably recognize that the encryption key deletion process by overwriting has been performed. [0040] Further, in the column direction between rows, it is possible to perform overwriting with specific columns such as 2, 5, 6, 8, 9,. It is possible to confirm overwriting. In this embodiment, in order to make error correction impossible in the row direction, it is sufficient to generate about 6% error in 11 bytes or more in 182 bytes. When this is done by overwriting a fixed pattern, if the probability that the overwritten mark overlaps the recorded mark position is 50%, it is almost impossible to correct if overwriting is performed with a recording pattern in which about 20% of the mark is overwritten. Become. Furthermore, in order to achieve reliable uncorrectability, the corresponding ECC block is played back, and a mark of about 10% is randomly added to the played back recorded bit string to increase the certainty of erasure. Is also possible.

As described above, in this embodiment, a plurality of data corresponding to the encryption key information in the ECC block configured on the optical disc 1 is selected, and the position of the recording bit string corresponding to each selected data In addition, since an overwrite bit string having a format different from that of the recording bit string is formed, the encryption key information can be erased stably without occurrence of servo instability. Especially when the encryption key information is recorded in the area RSV, the address and synchronization

Except for the code, the additional data part 35 in the row direction and the re-added data part 36 in the column direction are aligned to form an overwrite bit string at a predetermined position, so the data part storing the encryption key information is error-corrected. In addition, a stable reproduction operation is ensured. In addition, when the encryption key information is recorded in the original data 46 of a specific sector, the overwrite data generation circuit 26 does not perform error correction in a specific column portion or row portion with respect to the ECC block. Since the overwriting bit string is formed so that a valid state is generated, the encryption key information is erased stably.

As described above, the embodiments of the present invention have been described in detail with reference to the drawings. However, the specific configuration is not limited to the embodiments, and there may be changes in the design without departing from the gist of the present invention. Are included in the present invention.

For example, the ETM modulation used in the above embodiment may be, for example, 17 modulation or 8Z16 modulation. Further, in the above embodiment, the recording medium force CD-R, DVD-R, and other optical discs can be applied to all write-once recording media. Ma Even if a rewritable type recording medium such as CD-RW or DVD-RW is used as the recording medium, almost the same operations and effects as in the above embodiment can be obtained.

Claims

The scope of the claims

[1] A data recording apparatus for recording data on the recording medium by forming pits corresponding to a recording bit string on a recording track of the recording medium,

A sector is constructed by adding header information including at least an address to a fixed-length data block, and a plurality of the sectors are arranged in a two-dimensional matrix, and ECC (in each row direction and each column direction of the two-dimensional matrix) An ECC block is configured using a two-dimensional product code with an error correcting code (error correcting code) attached, and the ECC block is modulated by inserting a synchronization code at a fixed interval for recording. A recording data generation unit for generating data;

An overwrite data generation unit for generating an overwrite pattern;

A data recording unit for recording a recording bit string corresponding to the recording data or the overwrite pattern on the recording medium

And

The overwrite data generation unit selects a plurality of data in the ECC block, and an overwrite bit string having a format different from that of the record bit string is located at a position of the record bit string corresponding to each of the selected plurality of data. Generate the overwriting pattern to be written

Data recording device.

[2] Each of the selected data includes a part or all of the encryption key information generated when the recording data is generated.

The data recording device according to claim 1.

[3] The encryption key information is stored in the header information of a predetermined sector, and the overwrite data generation circuit makes the encryption key information uncorrectable by forming the overwrite bit string. The data recording device according to claim 2, wherein the overwriting pattern is generated as follows.

[4] The overwrite data generation circuit generates the overwrite pattern so that the overwrite bit string is formed at a position of a record bit string other than the record bit string corresponding to the address and synchronization code in the formed record bit string. Generate The data recording device according to claim 1.

[5] The recording bit string and the overwriting bit string are recorded on the recording medium as pit strings each including a mark part and a space part,

The overwrite data generation circuit generates the overwrite pattern so that a ratio of the mark portion of the overwrite bit string is equal to or less than a predetermined value.

The data recording device according to claim 1.

[6] The overwrite data generation circuit generates the overwrite pattern so that a ratio of the mark portion of the overwrite bit string is 20% or less.

The data recording device according to claim 5.

[7] The overwriting data generation circuit generates the overwriting pattern so that the overwriting bit string is formed in the ECC block so that an error uncorrectable state occurs in a specific column part or row part. Do

The data recording device according to claim 1.

[8] A sector is formed by attaching header information including at least an address to a fixed-length data block, and the plurality of sectors are arranged in a two-dimensional matrix, and each row direction and each column of the two-dimensional matrix An ECC block is configured using a two-dimensional product code with ECC (Error Correcting Code) attached to the direction, and the ECC block is modulated while inserting a synchronization code at a fixed interval. A data erasing method used in a data recording apparatus for recording on a recording medium a recording bit string corresponding to recording data generated by

Generating an overwrite pattern;

Recording a recording bit string corresponding to the overwrite pattern on the recording medium,

The step of generating the overwriting pattern includes:

Selecting a plurality of data in the ECC block;

Generating the overwrite pattern so that an overwrite bit string having a format different from that of the recording bit string is written at the position of the recording bit string corresponding to each of the selected plurality of data. A data erasing method comprising: