JP2024074206A - Judgment and verification device using error pattern chart of optical disc and digital watermark using error pattern - Google Patents

Abstract

To provide a method and a tool device for judging and verifying existence of destruction or forgery of evidence when a reading failure occurs on an optical disc, a method for individually identifying a disc, a digital watermark for improving the reliability in finding out unauthorized copying, if any, and an optical disc with the digital watermark embedded therein.SOLUTION: A method performs judgment and verification about destruction or forgery of evidence, wherein: when tracing an optical disc, a property that a recording time series coincides with an error time series, and a trace and a time series that there was a recording session even if data cannot be read are stored by being included in error distribution; and a property that a distribution status reflects a record history is used to estimate and approve a recording amount or recording time of the recording session by using an error pattern chart. Moreover, in order to realize a digital watermark capable of observation on the error pattern chart and an optical disc with improved reliability in finding out unauthorized copying, if any, individual identification of optical discs is performed by using the property that an error cannot be copied.SELECTED DRAWING: Figure 4

Description

The present invention relates to a method and device for investigating optical disks for storing data and for examining and verifying whether evidence has been destroyed or fabricated, a method for identifying individual disks, and an optical disk that increases the reliability of detecting unauthorized duplication.

An optical disk is a plate of light-transmitting plastic or the like, with a recording film and a reflective film layer, and a groove formed on the inside. The recording is an oval pit formed by a laser beam on the recording film. Since it is an industrial product, quality control is performed. For example, if the donut-shaped hole in the center of the disk is eccentric, the track will blur when the disk is rotated, and the optical head will exceed its tracking limit and become unable to read, so if the eccentricity is greater than a certain amount, it will be treated as a defective product. Alternatively, if the groove formation on the base is poor, it will be considered a defective product that induces tracking errors. If there are other problems, such as the thickness of the recording film being uneven or the reflectivity of the reflective film not reaching a specified value, it will be treated as a defective product that will cause the recorded data to be damaged.
As a method of quality assurance for optical disks, it is common to observe the amount of errors that occur during writing and reading of the disk. This not only allows manufacturing defects to be discovered, but also exposes problems in the manufacturing technology and may allow the cause to be inferred. For this reason, media manufacturers carry out error measurements when inspecting products before shipping.

On the other hand, even if the disk is an individual item that is treated as a defective product, since the error is an electrical signal, it can also be considered that the disk itself, which is a plastic plate that does not emit electrical signals, does not generate the error.
According to this view, errors are caused by faulty write or read operations in the drive device, so the source of the errors is the drive's electrical circuits. Even if the individual disks have manufacturing problems, the errors are considered to be caused by the action of the drive's electronic circuits, or the interaction between these, induced by the individual disks with manufacturing problems.

Error measurements are not only performed by disc manufacturers before shipment. In recent years, we have seen cases where users themselves measure errors on optical discs after recording data to see if any errors have occurred on the optical disc. This is because, as optical discs have become larger in capacity, they have begun to be used for backup purposes, and it has become necessary to manage the deterioration status of optical discs used for long-term backup storage. In relation to this, the Japanese Industrial Standards (JIS) have standardized it as "Long-term storage method for electronic documents (JIS Z6017)".

Conversely, optical discs are often used as evidence in civil and criminal court cases. The analysis of optical discs as evidence in court cases is called forensics. Forensic analysis of optical discs mainly concerns the contents of the data recorded on them, but because the contents of the data recorded on optical discs have high evidentiary value, they may also be subject to destruction of evidence.
The purpose of evidential analysis of optical disks is usually to read and evaluate the contents of the data reliably. In this case, the data output from the drive in which the optical disk is inserted is analyzed as being error-free.
The equipment and software applications used in such analysis methods are called digital forensic tools.
Originally, more than 99.9% of data recorded on a DVD was error-free, and even in the cases where errors did exist (less than about 0.1%), the DVD's error correction mechanism was so powerful that the errors were corrected, so it was assumed that 100% error correction would be completed.
As a result, typical conventional digital forensic tools do not have the functionality to efficiently analyze the digital signal after the optical signal read from the optical disk has been subjected to various signal processing operations, in its pre-error correction state.

What if the possibility of evidence destruction cannot be denied? The first thing to consider as evidence destruction in a legal case is the deletion of data files.
In contrast, in analysis using conventional digital forensic tools, the sample optical disk is inserted into an optical disk drive device connected to a computer or the like, and the recorded data status is read. Even if the data is not visible, analysis is still carried out to restore useful information by making full use of deleted data restoration application software, etc.
The target of deleted data restoration that can be expected to be successful with conventional digital forensic tools is deleted data files such as text data and still images in JPEG format. In this case, the data may be restored within the scope of the functions attached to the conventional digital forensic tools.
However, if the deleted data file is a video such as security video footage, restoration is difficult and there have been few successful cases.
Due to these practical circumstances, it has traditionally been considered reasonable to consider litigation cases to have concluded with the application of deleted data recovery application software, which is included in digital forensic tools.
In other words, in the past, although we did our best to the best of our ability, it could not be said that 100% analysis was performed.

Incidentally, with regard to optical disks, errors that occur during the recording and reading process account for less than 0.1% of the total recording volume. However, since errors are observed across almost the entire disk, even if there are more or less errors per sector, it can be said that the distribution of errors itself reflects the recording history of the disk.
In the past, when investigating the possibility of evidence destruction on optical disks that serve as evidence in legal cases, the perspective of investigating the recording history has been overlooked, and therefore error measurement for the purpose of investigating the possibility of evidence destruction has never been carried out.

As a remedy for this problem, the present invention takes advantage of the property that errors that occur during the recording and reading process of optical discs can be observed over almost the entire area of the disc, and considers that the distribution of errors reflects the recording history that occurred on the disc. Based on error measurements, it is possible to investigate and analyze what kind of errors exist at what locations between the start and end of the data area, thereby discovering the unique conditions at the time of recording that are reflected in the errors, and inventing a new analysis method and device to implement this method that compensates for areas that cannot be seen with conventional digital forensic tools. As a further application, it has invented an optical disc that increases the reliability of identifying individual discs and detecting unauthorized duplication.

Japanese Patent Application Laid-Open No. 5-250688 Japanese Patent Application Laid-Open No. 6-296112

Japanese Industrial Standards JIS X6257 Standards "Quality Assessment Methods for Optical Discs for Long-Term Data Storage and Operation Methods for Long-Term Storage Systems" 2017

Japanese Industrial Standard JIS X6256 Standard "Digital recording media for information exchange and storage - Test methods for estimating the life span of optical disk media for long-term data storage" 2019

Japanese Industrial Standards JIS Z6017 Standards "Long-term storage methods for electronic documents" 2013

Japanese Industrial Standards JIS X6249 Specification "80mm (1.46GB/side) and 120mm (4.70GB/side) DVD Recordable Discs (DVD-R)" 2009

Japanese Industrial Standards JIS X6282 Standards "120mm Recordable Optical Disk (CD-R) for Information Interchange" 2009

Japanese Industrial Standard JIS X6230 Standard "Digital recording media for information exchange and storage -- 120mm single-layer (25GB/disc) and dual-layer (50GB/disc) BD recordable discs" 2017

Japanese Industrial Standards JIS X6231 Specification "Digital recording media for information exchange and storage -- 120mm triple-layer single-sided (100GB/disc), triple-layer double-sided (200GB/disc) and quadruple-layer single-sided (128GB/disc) BD recordable discs" 2017

Japanese Industrial Standards JIS X6255 Standards "Data Migration Method for Optical Discs for Long-Term Data Storage" 2019

Japanese Industrial Standard JIS X6252 Specification "120mm (8.54Gbytes/side) and 80mm (2.66Gbytes/side) Dual-layer DVD Recordable Disc (DVD-R for DL)" 2011

International Organization for Standardization Standard ISO/IEC29121 Standard 2021

International Organization for Standardization ISO/IEC23912 Standards Corrected version 2006-04-01

International Organization for Standardization Standard ISO/IEC 30190 Standard 2021

International Organization for Standardization Standard ISO/IEC 30191 Standard 2021

International Organization for Standardization ISO/IEC 16963 Standards 2017

International Organization for Standardization ISO/IEC 12862 Standards 2011

International Electrotechnical Commission Standard IEC60908 Standard 1999

The problem to be solved is that conventional digital forensic tools were not able to analyze the digital area containing errors during the period from when the signal read by the optical head of an optical disk drive device is digitized to when it is error-corrected.
Furthermore, by applying the means invented to solve the problem, the problem that it was previously difficult to identify individual copy disks with the same hash value can also be solved.
In addition, the problem of detecting counterfeit copies, such as so-called pirated versions, is also solved.

The present invention is particularly effective when verifying whether or not evidence has been destroyed, so the main points of the principles applied in this case will be briefly described below.
On a DVD-R, data is recorded sequentially from the inner circumference without skipping any data. On the other hand, error measurement traces the entire area from the inner circumference address. This means that the time series of recording and the time series of error measurement match.
Furthermore, since there is no way to delete the error distribution, even if the evidence can be destroyed by deleting the files, if we focus on the error distribution, the evidence that the recording session existed cannot be destroyed.
In other words, even if evidence is destroyed, the traces and time series of what "happened" will be preserved as traces and time series on the error distribution.
Since errors are inherent to data, in the case of real-time recorded video data, the video recording time that existed before the file was deleted and the error recording time are the same in terms of the user area. Therefore, the percentage of the maximum writable capacity of the disk that the video data is, should match the percentage of the total disk capacity that the error distribution is. If they do not match, and the amount of playable video is unreasonably less than the amount of error distribution, then that disproportionate amount of video is deleted, revealing the possibility that evidence has been destroyed. From here on, the group of drawings that perform this function, showing the chronological results of error measurement, will be referred to as error pattern charts.

A more specific configuration of the present invention will now be described.
This invention consists of "001 - Error counting drive" and "002 - Personal computer installed with an application program for creating an error pattern chart" (Figure 1). The error counting drive is an optical disk drive (into which is inserted an optical disk to be inspected or an optical disk to be recorded and confirmed with a digital watermark) with an error counting function. In the case of a digital watermark using an error pattern, the optical disk itself is a constituent element of the invention, into which the digital watermark is embedded. Therefore, for a digital watermark invention, the optical disk on which the digital watermark is recorded can be a single constituent element. From these constituent elements, the error pattern chart in Figure 2 is generated, an analysis is performed, individual disc identification is performed, and the digital watermark is recorded and read.
First, the measurement method is as follows.
(1) The number of errors is counted by an error counting drive. The counted value, which is a set of the sector address (in hexadecimal notation) and the number of errors, is output from the error measuring device as a file in CSV format and is imported into a personal computer.
(2) The "error pattern chart creation application program" according to the embodiment of the present invention or a similar error pattern chart creation application program installed in a personal computer graphs the number of errors that have occurred for each address (represented as the amount of recorded data in the graph) from the innermost address to the outermost address within the user area, and creates an "error pattern chart."
At that time, within the scope of the standard functions of general-purpose spreadsheet application software such as Excel 2019, when trying to read a pair of sector address and number of errors and create a graph, there was a problem in which the hexadecimal value of the sector address could not be displayed correctly.
Therefore, in this invention, if you use Excel, you can create a dedicated program using Excel-VBA or similar to convert the sector address into the number of bytes consumed from the recording start point and display it on a chart (Figure 2).
Furthermore, in order to investigate optical discs for storing data and to assess and verify whether evidence has been destroyed or fabricated, which is the purpose of the present invention, the analysis will focus on the user area of the recording area of the optical disc, so the starting point of the chart to be created should be the starting point of the user area, which will make the analysis results clearer.
Therefore, when displaying the number of consumed bytes on the chart, the sector address (hexadecimal) is converted to decimal, and the amount from sector address 0 [hex] to the address of the start of the user area is subtracted as an offset, and the chart is created so that the start of the user area is displayed as 0.
For example, in the case of a DVD-R, the start point of the user area is 30000 [hex], and the offset amount after conversion to a decimal number is 196608 [dec].
For purposes such as appraisal or verification, the chart must be interpreted following measurement.
(3) Data storage optical discs such as CD-R, DVD-R, and BD-R are recorded sequentially from the start of recording without skipping tracks or sectors, and error measurement also traces the entire area from the inner circumference address. This results in the property that the time series of recording and the time series of the error pattern chart match. For this reason, even if the data is damaged and cannot be read, as long as it can be traced, the trace that the data recording session "existed" and its time series are included and preserved in the error distribution (Figure 3).
(4) Disks, being plastic plates that do not emit electrical signals, do not generate errors by themselves; it is the drive device that generates the errors. Any operation that is unexpected from the normal writing operation, such as an attempt to destroy evidence during the writing operation of the drive device, can also be a source of errors. Therefore, the error pattern chart also reflects defects in the writing operation due to unexpected operations during recording. In addition, since the time series during recording and the time series of the error pattern chart match, the error pattern chart shows the time series of the timing when defects in the writing operation during recording occurred. Since the interpretation of the error pattern chart is related to the recording state before error correction, it is possible to know the state of areas that cannot be seen with conventional digital forensic tools.
(5) Regarding the interpretation of the error pattern chart, the record history of deleted files is as follows:
With optical discs for storing data such as CD-R, DVD-R, and BD-R, it is possible to delete files that have been recorded by selecting the format. Deleted files, particularly video files, are often unable to be restored even with digital forensic tools. However, even if a file that was once recorded is deleted, traces of it remain in the error pattern. For this reason, even if the file contents cannot be read at all and the recording state of the file is unknown, by analyzing the error pattern chart it is possible to learn the recording history from optical discs that cannot be analyzed with conventional digital forensic tools. (Figure 4)
(6) The method for identifying individual disks by interpreting the error pattern chart is as follows.
Since the error pattern chart reflects differences in recording conditions, even if an optical disk has been copied using so-called disk copying and the hash values are identical and the disk would not be able to be distinguished as identical using conventional digital forensics, this method can be used to distinguish between disks if the recording conditions are different, for example, if the disk was copied using a computer and a duplicator, or if the computer, drive device, or duplicator used for copying was different.
When changing drives and writing to additional data, errors are likely to occur at the joints of the sessions, causing significant fluctuations in the recording timing and making synchronization errors more likely to occur. Once a synchronization error occurs, it will not disappear until synchronization is reestablished. Therefore, in error pattern analysis, the overwritten parts where a large number of errors are counted are characteristic parts that are the subject of error pattern analysis.
For example, in FIG. 4, four files were recorded in separate sessions in the order (1), (2), (3), and (4), resulting in large errors and step-like changes in errors at the transition between sessions.
In particular, between sessions (1) and (2) and between sessions (3) and (4), there are error patterns that show sharp, large error changes, and these error patterns are caused by "out-of-synchronization." Error changes caused by out-of-synchronization will be explained in a later section, and such error patterns make it easier to identify individual discs.
More specifically, the error count is measured using a measuring device that meets the JIS standard (JIS-Z6017), which ensures the reliability of the absolute value of the number of errors. The measuring device is designed to output the number of errors in a CSV file. The JIS standard measuring device itself is used to check whether the disc has deteriorated for the purpose of long-term storage of discs, and is not intended to determine the circumstances of evidence destruction or loss of evidence due to negligence. Therefore, an application program is added so that an error pattern chart for such a purpose can be automatically created. The contents of the program will be explained in the following embodiment by taking an application program written in Excel VBA as an example.
(7) By utilizing this property, it is possible to create optical discs with digital watermarks, as described below.
The most important property of watermarks imprinted on everyday paper currency and official documents is that the watermark does not appear in copies made of the original, or that the watermark cannot be copied.
The error pattern chart of the present invention visualizes the distribution of errors in all sectors of an optical disk, but since errors occur due to the laws of physics and are not something that can be copied arbitrarily, the error distribution on the original disk is not reproduced on the destination disk.
In other words, since errors cannot be copied, the error pattern cannot be copied either.
Therefore, as pattern 1, an unrecorded optical disk is embedded with an error pattern that is visually noticeable on an error pattern chart near the beginning of the user area, resulting in an optical disk with a digital watermark according to the present invention that has a higher degree of certainty in detecting unauthorized duplication. If data intended to be saved is recorded on an optical disk with a digital watermark embedded near the beginning of the user area according to the present invention, and the recorded optical disk is treated as the original disk, the error pattern near the beginning of the user area will not be copied to the destination disk, making it possible to detect that it is a copy (Figure 5).
As a pattern 2, an optical disk on which data intended to be stored has been recorded is embedded with a visually noticeable error pattern on an error pattern chart near the rear end of the user area as the electronic watermark according to the present invention before finalization, thereby making it possible to increase the certainty of detecting unauthorized copying with electronic watermark according to the present invention. If the optical disk after embedding the electronic watermark according to the present invention near the rear end of the user area is used as the original disk, the error pattern near the rear end of the user area will not be copied to the destination disk, making it possible to detect that it is a copy.
Furthermore, as pattern 3, as in pattern 2 above, an optical disk on which the first half of the data intended to be saved has already been recorded is embedded with an error pattern that is visually noticeable on an error pattern chart in the middle of the user area as an electronic watermark according to the present invention, and then the second half of the data intended to be saved is recorded. If this recorded optical disk is used as the original disk, then the error pattern near the middle of the user area will not be copied to a destination disk made by copying this, making it possible to detect that it is a copy.
The digital watermarks of Pattern 1, Pattern 2, and Pattern 3 can be combined and coexist, and a plurality of each can be embedded.
The above are the most essential features.

With this invention, even when data on a video recording disk is damaged and cannot be restored, and analysis using conventional digital forensic tools is not expected, analysis using the error pattern chart in this case can determine what percentage of the entire area contains error traces. For example, if there are error traces in 50% of a 120-minute disk, it can be determined that 60 minutes of recording took place.

When the disk is damaged and the data cannot be read due to the above effect, this method can trace the disk and read the errors, so it is possible to determine what percentage of the recordable time the error pattern corresponds to, and the amount of recorded time can be identified. For example, suppose that a certain location is secretly filmed so that it fits on one disk per day. Suppose that an accident occurs when the power is turned off for some reason when changing disks, causing the recording to end abnormally and making all of the videos from that day unplayable. If this is used as evidence in a lawsuit, it is possible that one party may claim that the fact that only the disk for that day is damaged and the video cannot be viewed means that one party destroyed evidence that contained a recording that was inconvenient for that party. In such cases, it is expected that the truth cannot be determined using conventional digital forensic tools, but by using this method, it is possible to determine what percentage of the recordable time the error pattern corresponds to, and the amount of recorded time can be identified. This makes it possible to prove the truth that "there is no recording from that time."

If only a specific file is deleted from a disk, the deleted file cannot be read as data, but it is possible to trace the entire disk, including the sector where the deleted file existed. By tracing the sectors, it is possible to count the number of errors. Therefore, by using this method, even if only a specific file is deleted from a disk, it is possible to know how much space the file equivalent to be deleted is by comparing the total capacity of the currently readable files with the total recording capacity consumed by the sectors where errors are found. (Figure 6)

A clone-like disk with the exact same file contents and structure can be created from an original disk, and this copying process is called disk copying. A disk copy has the same hash value as the original disk, making it nearly impossible to distinguish between the two disks using conventional digital forensics. Therefore, when data storage optical disks such as CD-Rs, DVD-Rs, and BD-Rs are treated as evidence in a lawsuit, the optical disk that is the evidence and the optical disk that is the copy of the evidence are considered to have equal evidentiary value if the procedures for making the evidence are carried out properly.
However, while it is not possible to distinguish between the original disk and the clone disk using conventional digital forensics, it is possible to distinguish between the two disks by comparing the error pattern charts produced by this method (Figure 7).
Figure 7 shows the error pattern charts for each of (1), (2), and (3) that were created when three disk copies were made from an original disk and labeled as (1), (2), and (3). Since a different write drive was used for each copy, by comparing and contrasting each error pattern chart in this way, it is possible to identify any changes in each one.

JIS-compliant disc inspection machines, such as the TEAC Corporation product "Model: DK-5000S-0A," come with a dedicated application that outputs measurement results as numerical values in a CSV file, but does not create an error pattern chart. In the present invention, as an example described below, an application program with the function of automatically creating an error pattern chart has been created. With this, the error patterns of multiple discs can be displayed simultaneously on a single chart and compared, so that if the discs have the same recording conditions, the lines on the chart will appear to overlap, which helps clarify the recording history of the disc.

By actively utilizing the function of identifying the disc recording history by the error pattern according to the present invention, an optical disc with a digital watermark function can be realized.
By embedding a digital watermark consisting of a characteristic error pattern that can be visualized on an error pattern chart at the beginning of recording in the user area of an unrecorded optical disc, or in the middle of an optical disc during data recording, or near the rear end of a recorded optical disc before finalization, it is possible to give the disc the ability to distinguish its authenticity from other discs.

FIG. 1 is an explanatory diagram of components of the present invention, namely a personal computer (with an application program installed) and an optical disk drive with an error counting function (into which a sample disk or an optical disk on which a digital watermark is to be recorded and confirmed is loaded). FIG. 2 is an explanatory diagram of an error pattern chart according to the present invention. FIG. 3 is an explanatory diagram of the concept that, due to the property that the time series of recording and the time series of the error pattern chart coincide in the data storage optical disc of the present invention, traces of the existence of a data recording session and its time series are contained and stored in the error distribution. FIG. 4 is an explanatory diagram for understanding the recording history based on the nature that even if a file that has been recorded is deleted, its trace remains in the error pattern, in interpretation of the error pattern chart in the present invention. FIG. 5 is an explanatory diagram of the error pattern digital watermark in the present invention. FIG. 6 is an explanatory diagram of the present invention, which shows that even when only a specific file is deleted, it is possible to know how much capacity the deleted file occupies. FIG. 7 is an explanatory diagram of a method for distinguishing between an original disk and a clone disk of a disk copy according to the present invention. FIG. 8 shows the error generation state of an actual optical disc, which is the premise of an embodiment of the interpretation of an error pattern chart according to the present invention, and is an explanatory diagram of how the amount of errors generated differs from place to place and from session to session, resulting in a concentric error pattern. FIG. 9 shows the results of measuring errors across the entire range of a commercially available DVD. FIG. 10 is an error pattern chart of the test disc. Fig. 11 shows an example of a PLL circuit for an optical disk drive (quoted from Japanese Patent Application Laid-Open No. 5-250688). Figure 12 shows an experimental phase modulator (quoted from Japanese Patent Laid-Open Publication No. 6-296112). Figure 13 shows the ECC block of a DVD-R. (Quoted from the Japanese Industrial Standards JIS X6249 Standards "80mm (1.46GB/side) and 120mm (4.70GB/side) DVD Recordable Discs (DVD-R)" 2009) Figure 14 shows the allowable range of overwriting for JIS-compliant DVD-R. (Quoted from the Japanese Industrial Standard JIS X6249 Specification "80mm (1.46GB/side) and 120mm (4.70GB/side) DVD Recordable Discs (DVD-R)" 2009) FIG. 15 shows an error pattern chart when additionally writing to a DVD-R. (Table 1-1) (Table 1-2) (Table 1-3) (Table 1-4) (Table 1-5) (Table 1-6) (Table 1-7) (Table 1-8) Tables 1-1 to 1-8 are linked together to show a flow chart of the application program according to the embodiment. (Table 2) shows the source code of the application program according to the embodiment. Based on the change in the detailed regulations pertaining to the application, the images in the main text of this specification, which are represented by circled numbers in FIG. 1 to FIG. 15, Tables 1 and 2, are replaced with numbers in parentheses such as (1), (2) and (3) in accordance with the changes in the detailed regulations pertaining to the application, are replaced with numbers in parentheses such as (1) and (2) in the source code of the application program in List 2, and the corresponding images in List 1 are represented by circled numbers. When the program is implemented, the program is operated with the circled numbers replaced, which results in the same operation as the application program confirmed by experiments etc. in the application.

Until now, optical disks have been analyzed by digital forensics, assuming that the data output from the drive in which the disk is inserted is error-free. More than 99.9% of the data recorded on a DVD is error-free, and even if there are errors that only exist in about 0.1% or less, the error correction mechanism of the DVD is extremely powerful and most errors are corrected, so it is reasonable to perform digital forensics on the premise that 100% error correction is complete. Even if data is invisible or useful information cannot be restored even after deleted data recovery, if more than 99.9% of the area has been analyzed by digital forensics, it is often reasonable to consider that what should be done in digital forensics is complete.
However, when 99.9% of the area has been analyzed, there are cases where only 0.1% of the analysis area remains, and it is necessary to start with that area. Although errors that occur during the recording and reading process account for less than 0.1% of the total recording amount, they are observed over almost the entire area of the disk, even if there is a greater or lesser amount per sector, and we focused on the possibility that the distribution of errors themselves may reflect the recording history of the disk.
In the present invention, by examining the error distribution, a breakthrough is achieved in tackling the remaining 0.1% area, and by analyzing the occurrence of errors as an interaction between an optical disk and a drive, a new analysis method is implemented to supplement areas that cannot be seen by digital forensics.

It became known that special consideration was required for optical disks for backup purposes, and this was standardized in the Japanese Industrial Standards (JIS) as "Methods for long-term preservation of electronic documents (JIS Z6017)."
First standardized in 2006 and revised in 2013, the main points are: (1) it is based on the premise that optical discs have a limited lifespan; (2) digitally recorded data has strong error correction capabilities; (3) the error situation when data is first recorded on the disc is inspected across the entire area where data is recorded; (4) it is required that the number of errors across the entire surface of the optical disc be less than the value specified by the JIS as the reference value for initial quality inspection; (5) thereafter, the error situation across the entire surface of the optical disc is inspected in regular quality inspections approximately every five years, and it is required that the maximum value be less than the value specified by the JIS as the reference value for regular quality inspection; and if these requirements are not met, the disc is to be remade.
In the JIS standard (similar standards have also been established as international standards), full-area inspection is prescribed, and the inspection pass/fail criterion is the maximum error value within the optical disk surface.
In response to this, testing equipment designed to meet the standards began to appear on the market.
The present invention is implemented as a new analysis method that uses such JIS standard inspection equipment to carry out measurements and determine what type of errors exist and where they are located between the start and end of the data area, thereby analyzing the occurrence of errors as a result of the interaction between the optical disk and the drive, and compensating for areas that cannot be seen using digital forensics.

Furthermore, the present invention is embodied as an analysis method using an error pattern chart made up of a group of drawings showing the chronological results of error measurement, so that the error pattern of the disc being analyzed can be easily compared with the error pattern of a reference disc, or the error patterns of multiple discs can be easily compared.
Furthermore, since the error pattern chart reflects differences in recording conditions, it can be used as a method to distinguish between optical disks copied by so-called disk copying, which have the same hash value and cannot be distinguished as identical using conventional digital forensics, when the recording conditions are different, for example, when the disk is copied using a computer and when it is copied using a duplicator, or when the computer, drive device, and duplicator used for copying are different.
In addition, the principle of the present invention can be applied to an optical disk with a digital watermark, taking advantage of the property that errors cannot be copied and therefore error patterns cannot be copied.
By embedding a digital watermark in advance, an error pattern near the beginning of the user area cannot be copied, and the optical disk can be easily identified as a copy.
After data is recorded, the digital watermark according to the present invention is embedded near the rear end of the user area, thereby making it possible to realize an optical disk with a high degree of certainty in detecting unauthorized duplication.
After embedding the electronic watermark of the present invention in the middle of the user area, where data has been recorded up to a certain point, the latter half of the data that is originally intended to be saved is recorded, thereby resulting in an optical disc with an electronic watermark embedded near the middle of the user area.

This embodiment is an embodiment of an analysis method using an error pattern chart according to the present invention, which is a method of analyzing a digital region that has not been analyzed in the past, from when a signal read by an optical head is digitized until it is subjected to error correction.
An embodiment of a method for interpreting an error pattern chart of an optical disk according to the present invention will be described below.
When writing multiple times to the same optical disk up to the recording end, the first recording is called the first session, the nth recording is called the nth session, etc. When there are multiple sessions, and typically multiple writing drives are used, the error occurrence conditions change for each session, which is reflected in the error distribution.
If there is a mistake or an abnormal termination in the last session, it may become impossible to read any of the files recorded in that session, or it may become impossible to read any files recorded in previous sessions. However, even in this case, it is possible to trace the sectors recorded up to that point, and to find out the error occurrence status of the traced sectors.
One of the important properties related to the present invention is that when the error distribution is analyzed, the error distribution state for each individual DVD is observed, which is not a uniform distribution.
DVD-Rs must be formatted when first used, and if you select the append format when formatting, you can later record additional files on a disc that has already been recorded. You can also erase files that have been recorded. In this case, even if you erase a file, a record will be made in the file management area to indicate that it has been erased, and if it is a write-once optical disc, the recording state of the sector where the file existed will not change.
Therefore, even for sectors where a file has been deleted, the error distribution state before the file is deleted will be reflected in the error distribution state after the file is deleted.

When observing the base surface of an actual CD-R or DVD-R, it is normal to be able to see a concentric pattern, and because the density of the pattern varies from place to place, it looks like a doughnut-shaped pattern overlapping each other. It is rare for the pattern to not be visible.
The amount of errors generated varies from place to place and from session to session. If we were to observe the error generation situation and express it as a pattern, a concentric pattern would reflect the reality.
If we think of subtracting only the data portion from a state in which data and errors are mixed, we can think of the distribution of errors as a donut-shaped pattern that changes.
(Figure 8)

In the case of a DVD-R on which data is written incrementally rather than the entire area being written at once, the error distribution changes around the boundaries near the start and end of recording, which are the boundaries between recording sessions.
If a session terminates abnormally, this is also reflected in the error distribution of the termination location.
Therefore, even if some kind of accident occurs when writing to a DVD-R, etc., and some or all of the file becomes unreadable, reading the error distribution that reflects the abnormal termination of the session due to the accident can provide clues for estimating what happened.

9 shows the results of measuring the overall error of a commercially available DVD. This is the result of measuring a single-layered DVD.
The number of errors remained constant, below 100 across the entire disc (the error rate is 0.033% for 8 ECC blocks (182 x 208 x 8) when the value is 100), which can be said to reflect the recording method used in DVD-ROMs, which are manufactured using the stamping method.
If a DVD-R is created in a write-once format, it is possible to delete files that have already been recorded. If all recorded files are deleted, they will no longer appear in the computer's Explorer, but if you measure errors across the entire DVD-R, the sectors where the files were recorded before the deletion will still contain errors from when they were recorded, even if they cannot be read as data.
Since there are no files, this is more of a sector tracing result than an error measurement result, but if the recorded files, recording order, Explorer display, etc., or an explanation are shown, it will become a diagram that can explain the error distribution situation.

FIG. 10 shows an error pattern chart of the test disc.
The subject was a DVD-R on which four image files had been recorded for testing purposes and then all files had been deleted.
The bottom center of the figure shows the display in a computer's Explorer, but since all the files have already been deleted, nothing is displayed. The bottom right of the figure shows recorded video files (part of a movie), which were recorded as separate sessions in the order of (1), (2), (3), and (4), and then all deleted at once. (1) is 6 minutes long, (2) is 10 minutes long, (3) is 14 minutes long, and (4) is 18 minutes long. The top of the figure shows the results of error measurements over the entire disc. The bottom left of the figure shows an enlarged portion of the global error diagram in the top figure, showing the error patterns in the sectors where files (1), (2), (3), and (4) were recorded.
Unlike commercially available DVDs, which have errors across the entire disc, the error occurrence conditions vary depending on the location, so the graph shows a stepped pattern.
There are large spikes of error between (1) and (2) and between (3) and (4).
This is not caused by a defective disk or the like, but is an error caused by out-of-synchronization that occurs when starting recording in a new session because the time standard is different from that of the previous session, and details will be described later in the section on Example 2. Since it serves as a marker for the join between sessions, it is easier to analyze if a synchronization error has occurred.
In this way, even if a disk does not show any files, analysis using an error pattern chart makes it possible to find evidence that files were recorded in four sessions.
A DVD-R from which data cannot be read cannot be analyzed by digital forensics. Even if security camera images recorded on a DVD-R are deleted, it is often difficult to restore the images by digital forensics.
Even under such circumstances, if the disc is not physically damaged, it is possible to trace it. If this is the case, then by carrying out optical disc analysis techniques using error pattern charts, it is possible to establish the fact that "some kind of accident occurred causing the session to end abnormally," and to generate evidence, etc., which is expected to fill in the areas that are not covered by traditional digital forensic analysis.

To summarize the concept of error print analysis, if a file cannot be read from the disk being analyzed or if the file cannot be restored, traditional digital forensics cannot proceed any further.
On the other hand, even if the file cannot be read, the session still exists and the session always contains some error, more or less.
Because the distribution of errors changes for each session, if an accident or other event occurs during recording on the disc and causes the session to end abnormally, this will be reflected in the error occurrence status. By measuring and charting the error distribution from the start point of recording on the disc (0.0 GB) to the maximum recordable point (4.38 GB for a write-once formatted DVD-R), the event that occurred can be inferred from the error pattern that reflects the abnormal end of the session due to an accident.
Therefore, by using the analysis method using the error pattern chart according to the present invention, it is possible to analyze optical disks on which accidents occurred during writing, which could not be analyzed using conventional digital forensics.
The procedure is as follows: (1) assume a possible situation and recreate the same situation, (2) write to a simulation DVD-R under that situation, (3) measure the error distribution on the simulation DVD-R, (4) chart and visualize the obtained error distribution (error pattern chart of comparison), (5) measure and chart and visualize the error distribution on the DVD-R to be analyzed (error pattern of analysis), and by comparing the error patterns in (4) and (5), it is possible to find traces that can be used to infer the event that occurred.

In the first embodiment, by carrying out an analysis using an error pattern chart on a write-once type optical disk, the following effects can be expected to be useful in determining facts in appraisal work.
(1) If it is claimed that a file that should have been recorded has been lost, but no evidence of this can be found through digital forensics and the deleted data cannot be restored, then if error measurements are carried out and an error pattern chart is created, and it is determined that the error patterns are in proportion to the capacity of the current readable files, then it can be presumed that there is no evidence that the recorded files have been deleted.
(2) When the observed error pattern does not match the current amount of readable files, it may be possible to infer the possibility of file deletion, as in the case of Figure 10 above.
(3) As an application, for example, in the case of Figure 10, if the person who recorded and deleted the files states that he recorded and then deleted files (1), (2), (3), and (4), and did not record the fifth or subsequent files, this can be supported by the error pattern chart.
(4) If it is indicated that an uncorrectable error, such as an extremely large error pattern, has occurred in the final recording portion of the last session, it may be possible to infer that an accident, such as a forced interruption of writing, has occurred and the session has terminated abnormally.
(5) For originals recorded in separate sessions, an error print chart like the example given in the previous section can be obtained. On the other hand, for copies, whether they are copied using a computer or a duplicator, if the entire process is recorded in one go from the start point to the end point, the error print pattern for each session will differ from that of the original. Therefore, it may be possible to distinguish between originals and copies by the error print.
(6) If the original is created in a write-once format and then turned into evidence, and then altered by adding new files using another computer, etc., an error pattern chart may show that the error patterns in the altered areas have steps or large error patterns at the joints, which may be useful in discovering and proving the alteration.

The second embodiment is an embodiment of a method for analyzing an error caused by out-of-synchronization.
As mentioned above, the optical disk itself does not generate errors; errors result from faulty writing or reading operations in the drive device, and the source of the errors is the electronic circuitry of the drive.
And when the drive's electronics read the data recorded on the optical disk, if they can't synchronize it with the reference clock pulses that were used when writing to the optical disk, everything will go erroneous.
Digital media that uses a motor to rotate a disk is required to (1) maintain a set number of rotations and (2) synchronize the clock pulse with the signal read from the rotating media. When synchronization is required in addition to the number of rotations, a method called PLL (Phase Lock Loop) is used. This involves installing a reference quartz oscillator inside the device, integrating an angle detector that generates a pulse at every fixed rotation angle with the rotating body, and matching the phase of the reference quartz with the phase of the angle detection signal to achieve a rotation speed accuracy equivalent to the accuracy limit of the angle detector's resolution.
In the case of optical disks, the phase of the signal output from the head that reads the disk, i.e., the phase on the disk side, is used as the reference, and the phase of the clock pulse of the data reader is aligned with this. In this way, there is only one clock pulse that serves as the phase reference, so as long as the phases are aligned, it will not cause errors.
Although the motor that spins the optical disk is highly accurate, it is unavoidable that there is at least 0.1% rotational unevenness, and if the rotational unevenness during writing and reading overlaps, it will be doubled, so the reference clock pulse will fluctuate by that amount. In addition, since the phase is unstable when the disk starts to rotate, it is necessary to add a circuit that makes the phase of the clock pulse of the data reader follow the phase of the signal output from the head that reads the disk, that is, the phase on the disk side. Here too, a PLL circuit is used.
An example of a PLL circuit for an optical disk drive is shown in Figure 11 (quoted from Japanese Patent Application Laid-Open No. 5-250688).
As shown in the schematic signal diagram at the bottom of the figure, the signal from the optical pickup is something like a synthesized sine wave whose frequency changes and whose harmonic components also fluctuate ("TE" in the figure).
For example, if a small amount of mold grows on the surface of an optical disc, making some of the pits unreadable, a portion of the signal will be missing, as shown by TE in the diagram. If a clock pulse is created from this signal by simply digitizing it through binarization, the clock pulse will change depending on whether there is a signal loss or not, as shown by "TC" in the diagram, causing an error.
The PLL circuit prevents this by generating a clock pulse based on the phase of the rising edge of the binary and digitized signal, and when there is a phase discrepancy between the clock pulse it generates and the signal from the optical pickup, it applies feedback to align the phase of the clock pulse it generates, thereby reducing the phase difference.
The PLL circuit installed in the optical disk drive takes into consideration the unique characteristic of optical disk drives that the signal may occasionally drop out, and limits the fluctuation range of the clock pulse frequency when reading data continuously, except in situations where the basic clock pulse frequency is expected to change significantly (when accessing a file at a distant address). The phase change during steady rotation is designed to be within about 20%, but there is a sufficient phase change margin for disk rotation irregularities.
In such a design example, if there is a phase change of more than 20%, it is assumed that there has been a signal loss, and the changed phase is not followed; instead, a clock pulse is generated while maintaining the previously established reference phase, thereby maintaining the correct read timing.
This is intended to prevent an error due to one missing signal from leading to an error in reading the next signal.

The main cause of the large number of errors that still occur is the phenomenon of "losing synchronization" in the PLL circuit.
Loss of synchronization occurs when a large event occurs that exceeds the phase change margin in the design specifications of the PLL circuit.
One of the assumed causes of desynchronization is when the reflective film of the disk rusts or the recording film changes over time, making it impossible to read signals over a wide area. In this case, the signal that should track the phase of the clock pulse is cut off for a long period of time, causing the phase of the clock pulse to shift significantly without being noticed. This is a form of desynchronization, and all data following the desynchronization will become erroneous.
Also, when the drive motor ages and the rotational irregularities increase, out-of-sync occurs if the fluctuations exceed the tracking range of the PLL circuit.
Another anticipated example is when the signal's C/N ratio (carrier-to-noise ratio) deteriorates, causing repeated situations in which the phase shift is due to the noise, and the phase shift continues to exceed the design margin, causing loss of synchronization and resulting in an error.
These phenomena can be confirmed experimentally. Figure 12 shows an experimental phase modulator. (Quoted from Japanese Patent Laid-Open Publication No. 6-296112)
When the drive's reference clock pulse is Φ0 in the figure, this circuit can obtain signals SP and SP' in the figure that have been affected by the reference phase change by applying SA in the figure as a simulation signal for rotation unevenness and noise.
When a signal with such a phase fluctuation is input to a PLL circuit, it is possible to confirm how out-of-synchronization occurs when the phase change exceeds the design margin.

To compensate for the one-time writing restriction, DVD-R is a write-once format (multi-session), and the standard supports the ability to add and delete files as needed, just like a USB memory stick.
However, if the drive on which data is written the first time is different from the drive on which data is written the second, third, etc., problems are likely to occur.
When writing data using different drives A and B, in a place such as the file management area, the records written by drive A and drive B are close to each other. The optical pickup judges the reference threshold for binarizing the signal according to the signal strength of drive A or drive B, whichever is written deeper, so the signal written shallower is suppressed and the C/N ratio deteriorates.
If a loss of synchronization occurs due to a deterioration in the C/N ratio, causing a large number of uncorrectable errors, it may become impossible to read the file itself.
There are also drives on the market that have write depths that are outside of the standard, and when appending data to one of these drives in turn using another drive, problems are sometimes seen where a file can be read on one drive (A), but the file that was written on drive B cannot be read at all on drive B.

The error pattern caused by the difference in write timing among a plurality of drives as described above has distinctive features.
The DVD's powerful error correction mechanism comes from the fact that horizontal and vertical parity is provided in the data format, and errors can be corrected by parity check. The JIS standard stipulates that "The number of PI errors is the number of rows in an ECC block that have at least one byte of error. In any eight consecutive ECC blocks, the total number of PI errors before error correction shall be 280 or less." The following is a brief summary of this regulation.
Error correction processing is performed on data and parity in units called ECC blocks, and one ECC block is made up of 208 lines, each of which is 182 bytes long.
Of the 182 bytes in one row, 172 bytes are data, and the final 10 bytes are PI (inner parity = inner code parity).
Of the 208 rows, 192 rows are data, and the final 16 rows are PO (outer parity = outer code parity).
Figure 13 shows the ECC block of a DVD-R. (Japanese Industrial Standards JIS X6249 Standards "80mm (1.46GB/side) and 120mm (4.70GB/side) DVD Recordable Discs (DVD-R)" 2009)
If there is an error of one byte or more in one row in a certain ECC block, it is called a PI error (PIE), which can be corrected by internal parity. Up to 280 errors can be corrected.
In addition, a state in which an error is contained in one row in one ECC even after error correction by internal parity is called a PO error (POE) or PIF error. Although this is a severe error, it may be possible to correct it by external parity even in this state.
An error that cannot be corrected even using external parity is called a POF error, and since there is no way to correct it, it results in data loss.
For error measurement on DVD-R, a test called PI/PO test is used which counts the number of errors corrected in one ECC block.
Generally, a test called PI-SUM8 is performed to count the number of errors in eight consecutive ECC blocks.

When writing is performed by alternately using the A drive and the B drive, the clock pulses generated by the quartz oscillators inside the devices of both drives cannot be synchronized.
Similarly, it is not possible to move the optical heads of both the A drive and the B drive in exactly the same way.
As a result, the timing of the start of recording cannot be matched, and a phase shift occurs when moving from an area written by drive A to an area written by drive B. If the phase shift is large, it cannot be followed and desynchronization occurs.
Furthermore, when using a different drive for each session in a write-once format, a small amount of overwriting may occur at the end of the previous recording.
When the overwritten portion is measured with an error measuring device, a large number of errors are counted, but since this is not a data portion of the record and is not subject to file output, for quality assurance purposes, the errors in this portion are not counted.

Such slight overwriting is inherent in the JIS standard and is considered to be permissible under the standard.
For example, JIS X6249, which specifies the characteristics of DVD-R, stipulates that when a new session is started after a session is closed, the start of the recording of the new session may be within one byte before or within one byte after the end of the recording of the previous session in the linking sector, which is the connecting part. Figure 14 shows the allowable overwrite range for JIS-standard DVD-R.

However, in terms of error pattern analysis, the overwritten portion where such a large number of errors are counted is a characteristic portion that is the subject of error pattern analysis.
FIG. 15 shows an error pattern chart when additional data is written to a DVD-R.
When using different drives for each append session, overwriting is likely to occur at the joints as mentioned above, so although the joints are not data and are not subject to error correction, they are displayed as large errors in the notation. This is because the phase of the overwritten part fluctuated beyond the tracking limit of the PLL circuit, causing an out-of-synchronization and resulting in a large error.
In addition, since the average value of the error measurement values in the data area differs for each session, the error pattern chart is displayed in a stepped manner.
When analyzing multi-layered DVDs or Blu-ray discs, step-like error patterns are observed at the joints between the layers, so this must be distinguished from overwriting.

In the second embodiment, by carrying out an analysis using an error pattern chart on a write-once type optical disk, the following effects can be expected to contribute to the inference of facts in appraisal work.
A. Large spike-shaped error pattern If a very large spike-shaped error is observed on the error pattern chart, it is possible that a write session has ended (including an abnormal end) at that location, or that a temporary write interruption to prevent a buffer underrun has occurred, and new write operations have begun.
b) Stair-like error patterns If the error pattern chart has a stepped pattern that corresponds to the total session size estimated from the file size that can be read from the disc, then in the case of a single-layer DVD/BD, it is possible that a different drive was used for recording each session.
C) Exceptions for multi-layer DVDs and multi-layer Blu-rays For the error pattern charts of dual-layer DVD-R-DL 8.5 GB and BD-R-DL 50 GB, triple-layer BD-R-XL 100 GB, and quadruple-layer BD-R-XL 128 GB, the error pattern chart will have a stepped appearance at the change of layers.
However, if the step location does not coincide with the seam of the layers, it is possible that each session was recorded using a different drive.

The third embodiment is an embodiment of a digital watermark that uses the nature of errors that occur due to desynchronization to perform individual identification, and an embodiment of an optical disk that can be individually identified.

Out-of-synchronization can be intentionally created. For example, in an experiment, if a DVD-R disk on which files were recorded in the first session using an external drive WH16NS58DUP manufactured by LG HLDS was once terminated and the disk was removed, and then in the second session files were recorded using an external drive DVR-S21DBK manufactured by PIODATA, there was a very high probability of obtaining a large spike-like error pattern caused by out-of-synchronization between the first and second sessions.
Even with other drive combinations, if you change drives for each session, you will often get large spike-like error patterns.

Using this, immediately after formatting a DVD-R, (1) a small file of a predetermined size is recorded, (2) the session is terminated, (3) the drive is switched to another drive, a small file is recorded as a new session, and (4) the session is terminated. Through this process of (1) to (4), each time a new session is recorded on a different drive, one artificially large spike-like error pattern can be obtained, and by performing a new session multiple times, multiple large spike-like error patterns can be obtained, concentrated in the area near the inner circumference of the disc immediately after formatting.
Although the probability of a large spike-like error occurring is not 100%, when the above operation is carried out with the intention of generating, for example, eight consecutive large spike-like errors, experimentally five or more large spike-like errors have been obtained.

It is possible to intentionally prevent out-of-synchronization. For example, in an experiment, a DVD-R disc was recorded as the first session using a Lenovo ThinkPad W540 computer with a built-in DVD drive MATSUSHITA DVD drive UJ8E2, and then the session was terminated and the disc was removed. In the second session, files were then recorded using a Dell E6540 computer with a built-in DVD drive. With a very high probability, no large spike-shaped error patterns were observed between the first and second sessions. Depending on the drive design, it is possible to intentionally prevent out-of-synchronization.

By utilizing these facts, immediately after formatting a DVD-R, multiple sessions can be combined to intentionally cause desynchronization, concentrating on the area near the inner circumference, and sessions to intentionally prevent desynchronization, making it possible to freely generate or not generate large spike-like errors at regular intervals.
If it is possible to intentionally create an arrangement of large spike-like errors in this way, then, for example, by making 4 groups x 8 sessions from the innermost circumference into such an intentional out-of-synchronization error generation area, it will be possible to reliably observe large spike-like errors for 4 groups, making it possible to record an identification code of at least 4 bits in length.
If a separate ID code is attached to each disk, there will be 4 bits, i.e., 16 different identification codes, and it is also possible to use a common identification code for disks recorded at a certain business establishment.
Instead of 4 bits, the identification code may be shorter or longer.
Hereinafter, such a method of attaching an identification code will be referred to as an error pattern digital watermark.
The above-mentioned FIG. 5 shows an embodiment of the error fingerprint digital watermark.

An error pattern digital watermark can be recorded immediately after formatting before data is recorded, or it can be recorded on the outermost circumference after all recording has been completed and just before finalization. It can also be recorded halfway between the innermost and outermost circumferences. One possible use for recording at a midpoint is when recording data for multiple days on a single disc, by recording such an error pattern digital watermark at the end of each day's recording, it is possible to clearly distinguish the boundaries between recording dates.

Since the error fingerprint watermark is removed as an electromagnetic signal after error correction, when an original disk on which an error fingerprint watermark is recorded is copied, the error fingerprint watermark is not reproduced on the copy disk.
This property can be used to distinguish between originals and copies.
This property is not dependent on the file being recorded, and even if the original and copy have the same file hash value, the original and copy can be distinguished from each other.

As described above, by adding an error pattern digital watermark to a file to be saved before recording, an optical disk that can be individually identified can be realized.
Also, after recording a file to be saved, an error pattern digital watermark can be added to realize an optical disk that can be individually identified.

The fourth embodiment relates to a method for identifying disks having the same hash value by using an error pattern.
In conventional digital forensics, when it comes to determining whether a target disk is an original or a copy, if the disk images are identical, the hash values are the same and it is impossible to distinguish between them. Furthermore, there has been almost no discussion about the significance of identifying and classifying disks with the same hash value.
However, in litigation cases, the switching of originals and copies due to fabrication, substitution, or damage of evidence can become a point of contention in court, so there is a need for methods to identify or classify individual disks even if the hash values of the disk images are the same, and in this respect it is desirable to have methods that can complement traditional digital forensics.
Furthermore, in the case of the production of pirated copies, which is a violation of copyright law, when there are multiple disks that are all pirated copies, it is possible to classify them based on the differences in the error patterns. As a result of the classification, it may be possible to distinguish between those mass-produced by duplicators and the small number of disks that are the masters of the pirated copies, which is expected to be useful in identifying the perpetrators of the pirated copies production.
By using the error print analysis method of this case, it is possible to distinguish between originals and copies by observing the error distribution, even if the hash values are the same.

A widely used method of copying disks is to use a computer to use copying software to download a disk image of the source disk and then write that disk image to an unused disk, resulting in a copy with the same file hash value.
There has not been much talk about error patterns on copies until now, but on the original disc, a step-like change in the error patterns can be seen at the seams between sessions, but this does not occur on the copy disc.
In some cases, copies may end up with significantly fewer errors and be of higher quality than the original.
When talking about disc images, one might misunderstand that they copy and reproduce every single piece of information on the original disc, but this result embodies the fact that this is not the case.
A disk image merely copies logical blocks, and cannot copy or generate things like errors, which occur as natural, scientific, physical phenomena and can be corrected and addressed when they occur.
In this case, when the image of the original disk is read, all the errors on the error pattern chart are corrected, and an error-free disk image is created. Then, when writing to the copy disk, writing is done in one go from the beginning to the end, so there is no overwriting and major errors are unlikely to occur.
By using the method of the present invention to identify disks with the same hash value by the error pattern, it is possible to read the situation in which the recording history is reflected in the error pattern, and therefore to distinguish between an original disk in which a synchronization error has occurred and a copy disk in which no synchronization error has occurred, or to distinguish between a copy disk in which no step-like error pattern change has occurred.

Furthermore, experiments have shown that even if copies are made from the same original disk using the same drive, if the recording history is even slightly different, the error fingerprints will be different, and it may be possible to identify individual disks even if disk images with the same hash values are recorded. For example, when copying a disk using a PC and the copy function of copying software, you can select an option to use or not use the HDD. The error fingerprints of the copies may differ depending on whether or not you use this option.
By using the method of the present invention to identify disks with the same hash value by error prints, it is possible to read the situation in which the recording history is reflected in the error prints. In conclusion, for disks with different recording histories, even if the recorded disk images are the same, it is possible to identify individual disks by analyzing the error prints.
FIG. 7 mentioned above is an explanatory diagram of an embodiment of a method for identifying disks having the same hash value by using an error pattern by disk copying.

In Example 5, when data on a video recording disk is damaged and cannot be restored, and analysis using conventional digital forensic tools is not expected, the analysis method using the error pattern chart in question can determine what percentage of the entire area the error traces account for, which can be used as verification in litigation, etc., and can be used as evidence.

As can be seen from the fact that DVD-Rs for TV recording are sold as "120 minutes" discs, the total recording time per disc is determined by the settings of the recording mode, etc., so if it is possible to measure what percentage of the recording area has errors compared to the maximum recording capacity of a disc, then it is possible to determine with almost certainty that "because there are traces of errors in 60% of a disc set to record 120 minutes in its entirety, 72 minutes of recording had been performed before the data was damaged," without any need for complex interpretations.

In legal proceedings, such measurements can be carried out as verification because they are of a nature that can be perceived through the five senses, faithfully recorded, and interpreted.

Example 6 relates to a device used for analysis using an error pattern chart.

When measurements are to be used as evidence in court, JIS standard measuring equipment with guaranteed reliability should be used.
Currently available JIS standard inspection devices trace the disk from the innermost circumference and count the number of errors for each error correction block. One such inspection device, the TEAC DK-5000S-0A, outputs the error count results as a CSV file with sector addresses and the number of errors, and although the numerical values can be accurately grasped, no charts are created.
In this method, the conclusion depends on where the error is located on the disk. An error pattern chart makes it easy to see, and it is appropriate to create a line graph using Excel.
However, disk sector addresses are specified in hexadecimal, so creating charts in Excel requires some skill. Excel does not handle hexadecimal addresses well, and when reading them as numbers, it treats the "E" in the hexadecimal number 0123456789ABCDEF as an exponent. No matter how you change Excel's settings, this problem will not be solved as long as you read "E" as a number.
To solve this problem, some ingenuity is required, such as reading the hexadecimal address as a character string and then converting it to a decimal number.
In this embodiment, an application program for generating an error pattern chart from an inspection machine that outputs hexadecimal addresses and the number of errors in a CSV format file is exemplified as a device for generating an error pattern chart.

Table 1 (divided into Tables 1-1 through 1-8) shows a flow chart of an exemplary application program.
Table 2 shows the source code of an exemplary application program.

（表１－２）

（表１－３）

（表１－４）

（表１－５）

（表１－６）

（表１－７）

（表１－８）

The examples in these lists are the source code for an Excel VBA application program that creates an overlaid error pattern chart for comparison from eight CSV (with txt extension) files of error measurement results measured using the app provided with the TEAC DK-5000S-0A.
(Table 1-1)

(Table 1-2)

(Table 1-3)

(Table 1-4)

(Table 1-5)

(Table 1-6)

(Table 1-7)

(Table 1-8)

(Table 2)

Sub Macro02 Full Area Inspection()


Sheets("Sheet3").Select

ChDir "D:\ExcelMacro4ErrorChart"
Workbooks.OpenTextFilename:= _
"D:\ExcelMacro4ErrorChart\driveD\ExamAll01Times.txt", Origin:=932 _
, StartRow:=1, DataType:=xlDelimited, TextQualifier:=xlDoubleQuote, _
ConsecutiveDelimiter:=False, Tab:=False, Semicolon:=False, Comma:=True _
, Space:=False, Other:=False, FieldInfo:=Array(Array(1, 2), Array(2, 1), _
Array(3, 1)), TrailingMinusNumbers:=True
Columns("A:C").Select
Selection.Copy
Windows("Reproducibility test 8 times.xlsm").Activate
ActiveSheet.Paste
Windows("ExamAll01Times.txt").Activate
Application.CutCopyMode = False
ActiveWorkbook.SaveAs Filename:= _
"D:\ExcelMacro4ErrorChart\ExamAll01Times.xlsx", FileFormat _
:=xlOpenXMLWorkbook, CreateBackup:=False
ActiveWindow.Close
Workbooks.OpenTextFilename:= _
"D:\ExcelMacro4ErrorChart\driveD\ExamAll02Times.txt", Origin:=932 _
, StartRow:=1, DataType:=xlDelimited, TextQualifier:=xlDoubleQuote, _
ConsecutiveDelimiter:=False, Tab:=False, Semicolon:=False, Comma:=True _
, Space:=False, Other:=False, FieldInfo:=Array(Array(1, 2), Array(2, 1), _
Array(3, 1)), TrailingMinusNumbers:=True
Columns("A:C").Select
Selection.Copy
Windows("Reproducibility test 8 times.xlsm").Activate
Range("D1").Select
ActiveSheet.Paste
Windows("ExamAll02Times.txt").Activate
Application.CutCopyMode = False
ActiveWorkbook.SaveAs Filename:= _
"D:\ExcelMacro4ErrorChart\ExamAll02Times.xlsx", FileFormat _
:=xlOpenXMLWorkbook, CreateBackup:=False
ActiveWindow.Close
Range("G1").Select
Workbooks.OpenTextFilename:= _
"D:\ExcelMacro4ErrorChart\driveD\ExamAll03Times.txt", Origin:=932 _
, StartRow:=1, DataType:=xlDelimited, TextQualifier:=xlDoubleQuote, _
ConsecutiveDelimiter:=False, Tab:=False, Semicolon:=False, Comma:=True _
, Space:=False, Other:=False, FieldInfo:=Array(Array(1, 2), Array(2, 1), _
Array(3, 1)), TrailingMinusNumbers:=True
Columns("A:C").Select
Selection.Copy
Windows("Reproducibility test 8 times.xlsm").Activate
ActiveSheet.Paste
Windows("ExamAll03Times.txt").Activate
Application.CutCopyMode = False
ActiveWorkbook.SaveAs Filename:= _
"D:\ExcelMacro4ErrorChart\ExamAll03Times.xlsx", FileFormat _
:=xlOpenXMLWorkbook, CreateBackup:=False
ActiveWindow.Close
Workbooks.OpenTextFilename:= _
"D:\ExcelMacro4ErrorChart\driveD\ExamAll04Times.txt", Origin:=932 _
, StartRow:=1, DataType:=xlDelimited, TextQualifier:=xlDoubleQuote, _
ConsecutiveDelimiter:=False, Tab:=False, Semicolon:=False, Comma:=True _
, Space:=False, Other:=False, FieldInfo:=Array(Array(1, 2), Array(2, 1), _
Array(3, 1)), TrailingMinusNumbers:=True
Columns("A:C").Select
Selection.Copy
Application.Left = 18.625
Application.Top = 38.125
Windows("Reproducibility test 8 times.xlsm").Activate
Range("J1").Select
ActiveSheet.Paste
Windows("ExamAll04Times.txt").Activate
Application.CutCopyMode = False
ActiveWorkbook.SaveAs Filename:= _
"D:\ExcelMacro4ErrorChart\ExamAll04Times.xlsx", FileFormat _
:=xlOpenXMLWorkbook, CreateBackup:=False
ActiveWindow.Close
Range("M1").Select
Workbooks.OpenTextFilename:= _
"D:\ExcelMacro4ErrorChart\driveD\ExamAll05Times.txt", Origin:=932 _
, StartRow:=1, DataType:=xlDelimited, TextQualifier:=xlDoubleQuote, _
ConsecutiveDelimiter:=False, Tab:=False, Semicolon:=False, Comma:=True _
, Space:=False, Other:=False, FieldInfo:=Array(Array(1, 2), Array(2, 1), _
Array(3, 1)), TrailingMinusNumbers:=True
Columns("A:C").Select
Selection.Copy
Windows("Reproducibility test 8 times.xlsm").Activate
ActiveSheet.Paste
Windows("ExamAll05Times.txt").Activate
Application.CutCopyMode = False
ActiveWorkbook.SaveAs Filename:= _
"D:\ExcelMacro4ErrorChart\ExamAll05Times.xlsx", FileFormat _
:=xlOpenXMLWorkbook, CreateBackup:=False
ActiveWindow.Close
Range("P1").Select
Workbooks.OpenTextFilename:= _
"D:\ExcelMacro4ErrorChart\driveD\ExamAll06Times.txt", Origin:=932 _
, StartRow:=1, DataType:=xlDelimited, TextQualifier:=xlDoubleQuote, _
ConsecutiveDelimiter:=False, Tab:=False, Semicolon:=False, Comma:=True _
, Space:=False, Other:=False, FieldInfo:=Array(Array(1, 2), Array(2, 1), _
Array(3, 1)), TrailingMinusNumbers:=True
Columns("A:C").Select
Selection.Copy
Windows("Reproducibility test 8 times.xlsm").Activate
ActiveSheet.Paste
ActiveWindow.SmallScrollToRight:=2
Windows("ExamAll06Times.txt").Activate
Application.CutCopyMode = False
ActiveWorkbook.SaveAs Filename:= _
"D:\ExcelMacro4ErrorChart\ExamAll06Times.xlsx", FileFormat _
:=xlOpenXMLWorkbook, CreateBackup:=False
ActiveWindow.Close
Range("S1").Select
Workbooks.OpenTextFilename:= _
"D:\ExcelMacro4ErrorChart\driveD\ExamAll07Times.txt", Origin:=932 _
, StartRow:=1, DataType:=xlDelimited, TextQualifier:=xlDoubleQuote, _
ConsecutiveDelimiter:=False, Tab:=False, Semicolon:=False, Comma:=True _
, Space:=False, Other:=False, FieldInfo:=Array(Array(1, 2), Array(2, 1), _
Array(3, 1)), TrailingMinusNumbers:=True
Columns("A:C").Select
Selection.Copy
Windows("Reproducibility test 8 times.xlsm").Activate
ActiveSheet.Paste
ActiveWindow.ScrollColumn = 4
Windows("ExamAll07Times.txt").Activate
Application.CutCopyMode = False
ActiveWorkbook.SaveAs Filename:= _
"D:\ExcelMacro4ErrorChart\ExamAll07Times.xlsx", FileFormat _
:=xlOpenXMLWorkbook, CreateBackup:=False
ActiveWindow.Close
Range("V1").Select
Workbooks.OpenTextFilename:= _
"D:\ExcelMacro4ErrorChart\driveD\ExamAll08Times.txt", Origin:=932 _
, StartRow:=1, DataType:=xlDelimited, TextQualifier:=xlDoubleQuote, _
ConsecutiveDelimiter:=False, Tab:=False, Semicolon:=False, Comma:=True _
, Space:=False, Other:=False, FieldInfo:=Array(Array(1, 2), Array(2, 1), _
Array(3, 1)), TrailingMinusNumbers:=True
Columns("A:C").Select
Selection.Copy
Windows("Reproducibility test 8 times.xlsm").Activate
ActiveSheet.Paste
Windows("ExamAll08Times.txt").Activate
Application.CutCopyMode = False
ActiveWorkbook.SaveAs Filename:= _
"D:\ExcelMacro4ErrorChart\ExamAll08Times.xlsx", FileFormat _
:=xlOpenXMLWorkbook, CreateBackup:=False
ActiveWindow.Close
Sheets("Sheet3").Select
Sheets("Sheet3").Copy Before:=Sheets(1)
ActiveWindow.ScrollColumn = 12
ActiveWindow.ScrollColumn = 1
Range("A1").Select
Sheets("Sheet3 (2)").Select
Sheets("Sheet3 (2)").Copy Before:=Sheets(1)
Columns("A:A").Select
Selection.Insert Shift:=xlToRight, CopyOrigin:=xlFormatFromLeftOrAbove
Range("A1").Select
ActiveCell.FormulaR1C1 = "PBA⇒GB1"
Range("A2").Select
ActiveCell.FormulaR1C1 = "=DECIMAL(RC[1],16)"
Selection.Copy
Range("A3").Select
Selection.SpecialCells(xlCellTypeLastCell).Select
Range("A3:A17934").Select
Range("A17934").Activate
ActiveSheet.Paste
ActiveWindow.ScrollRow = 3810
ActiveWindow.ScrollRow = 1
Range("A1").Select
Application.CutCopyMode = False
ActiveCell.FormulaR1C1 = "PBA⇒decimal"
Columns("A:A").Select
Selection.Insert Shift:=xlToRight, CopyOrigin:=xlFormatFromLeftOrAbove
Range("A1").Select
ActiveCell.FormulaR1C1 = "offset"
Range("A2").Select
ActiveCell.FormulaR1C1 = "=RC[1]-196608"
Range("A2").Select
Selection.Copy
Selection.SpecialCells(xlCellTypeLastCell).Select
Range("A3:A17934").Select
Range("A17934").Activate
ActiveSheet.Paste
ActiveWindow.ScrollRow = 3805
ActiveWindow.ScrollRow = 1
Columns("A:A").Select
Application.CutCopyMode = False
Selection.Insert Shift:=xlToRight, CopyOrigin:=xlFormatFromLeftOrAbove
Range("A1").Select
ActiveCell.FormulaR1C1 = "×2048"
Range("A2").Select
ActiveCell.FormulaR1C1 = "=RC[1]*2048"
Range("A2").Select
Selection.Copy
Selection.SpecialCells(xlCellTypeLastCell).Select
Range("A3:A17934").Select
Range("A17934").Activate
ActiveSheet.Paste
ActiveWindow.ScrollRow = 3810
ActiveWindow.ScrollRow = 1
Columns("A:A").Select
Application.CutCopyMode = False
Selection.Insert Shift:=xlToRight, CopyOrigin:=xlFormatFromLeftOrAbove
Range("A1").Select
ActiveCell.FormulaR1C1 = ""
Range("A2").Select
ActiveCell.FormulaR1C1 = "=RC[1]/1000000000"
Range("A2").Select
Selection.Copy
Selection.SpecialCells(xlCellTypeLastCell).Select
Range("A3:A17934").Select
Range("A17934").Activate
ActiveSheet.Paste
ActiveWindow.ScrollRow = 3810
ActiveWindow.ScrollRow = 1
Columns("A:A").Select
Application.CutCopyMode = False
Selection.Insert Shift:=xlToRight, CopyOrigin:=xlFormatFromLeftOrAbove
Columns("A:A").Select
Selection.NumberFormatLocal = "0.00_ "
Columns("B:B").Select
Selection.Copy
Range("A1").Select
Selection.PasteSpecial Paste:=xlPasteValues, Operation:=xlNone, SkipBlanks _
:=False, Transpose:=False
Sheets("Sheet3 (3)").Select
Application.CutCopyMode = False
Sheets("Sheet3 (3)").Copy Before:=Sheets(1)
Columns("B:F").Select
Selection.Delete Shift:=xlToLeft
Range("B1").Select
ActiveCell.FormulaR1C1 = "PI・SUM8(1)"
Columns("C:D").Select
Selection.Delete Shift:=xlToLeft
Range("C1").Select
ActiveCell.FormulaR1C1 = "PI・SUM8(2)"
Columns("D:E").Select
Selection.Delete Shift:=xlToLeft
Range("D1").Select
ActiveCell.FormulaR1C1 = "PI・SUM8(3)"
Columns("E:F").Select
Selection.Delete Shift:=xlToLeft
Range("E1").Select
ActiveCell.FormulaR1C1 = "PI・SUM8(4)"
Columns("F:G").Select
Selection.Delete Shift:=xlToLeft
Range("F1").Select
ActiveCell.FormulaR1C1 = "PI・SUM8(5)"
Columns("G:H").Select
Selection.Delete Shift:=xlToLeft
Range("G1").Select
ActiveCell.FormulaR1C1 = "PI・SUM8(6)"
Columns("H:H").Select
Selection.ColumnWidth = 9.75
Selection.ColumnWidth = 9.81
Columns("H:I").Select
Selection.Delete Shift:=xlToLeft
Range("H1").Select
ActiveCell.FormulaR1C1 = "PI・SUM8(7)"
Columns("I:J").Select
Selection.Delete Shift:=xlToLeft
Range("I1").Select
ActiveCell.FormulaR1C1 = "PI・SUM8(8)"
Columns("J:J").Select
Selection.Delete Shift:=xlToLeft
Range("A1").Select
Sheets("Sheet3 (4)").Select
Sheets("Sheet3 (4)").Name = "PI・SUM8(1)-(8)"



ActiveSheet.Shapes.AddChart xlLine, 180, 100, 800, 400

With ActiveSheet.ChartObjects(1).Chart
.SetSourceData Source:=Range(Range("A1"), ActiveCell.SpecialCells(Type:=xlCellTypeLastCell))


.SeriesCollection(1).Format.Fill.ForeColor _
.ObjectThemeColor = msoThemeColorAccent6


.Axes(xlValue, xlPrimary).HasTitle = True
.Axes(xlValue, xlPrimary).AxisTitle.Text = "Number of Errors"
.Axes(xlValue, xlPrimary).AxisTitle.Orientation = xlVertical
.Axes(xlValue, xlPrimary).TickLabels.NumberFormat = "####"

.HasTitle = True
.ChartTitle.Text = "Full Area Inspection PI-SUM8"


.HasLegend = True
.Legend.Position = xlLegendPositionTop

End With







Sheets("Sheet3 (3)").Select
Sheets("Sheet3 (3)").Copy Before:=Sheets(1)
Columns("B:G").Select
Selection.Delete Shift:=xlToLeft
Range("B1").Select
ActiveCell.FormulaR1C1 = "POF(1)"
Columns("C:D").Select
Selection.Delete Shift:=xlToLeft
Range("C1").Select
Selection.ClearContents
ActiveCell.FormulaR1C1 = "POF(2)"
Columns("D:E").Select
Selection.Delete Shift:=xlToLeft
Range("D1").Select
ActiveCell.FormulaR1C1 = "POF(3)"
Columns("E:F").Select
Selection.Delete Shift:=xlToLeft
Range("E1").Select
ActiveCell.FormulaR1C1 = "POF(4)"
Columns("F:G").Select
Selection.Delete Shift:=xlToLeft
Range("F1").Select
ActiveCell.FormulaR1C1 = "POF(5)"
Columns("G:H").Select
Selection.Delete Shift:=xlToLeft
Range("G1").Select
ActiveCell.FormulaR1C1 = "POF(6)"
Columns("H:I").Select
Selection.Delete Shift:=xlToLeft
Range("H1").Select
ActiveCell.FormulaR1C1 = "POF(7)"
Columns("I:J").Select
Selection.Delete Shift:=xlToLeft
Range("I1").Select
ActiveCell.FormulaR1C1 = "POF(8)"
Range("A1").Select
Sheets("Sheet3 (4)").Select
Sheets("Sheet3 (4)").Name = "POF(1)-(8) Entire Area"
Range("A1").Select
ActiveWorkbook.Save


ActiveSheet.Shapes.AddChart xlLine, 180, 100, 800, 400

With ActiveSheet.ChartObjects(1).Chart
.SetSourceData Source:=Range(Range("A1"), ActiveCell.SpecialCells(Type:=xlCellTypeLastCell))


.SeriesCollection(1).Format.Fill.ForeColor _
.ObjectThemeColor = msoThemeColorAccent6


.Axes(xlValue, xlPrimary).HasTitle = True
.Axes(xlValue, xlPrimary).AxisTitle.Text = "Number of Errors"
.Axes(xlValue, xlPrimary).AxisTitle.Orientation = xlVertical
.Axes(xlValue, xlPrimary).TickLabels.NumberFormat = "####"


.HasTitle = True
.ChartTitle.Text = "Full Area Inspection POF"


.HasLegend = True
.Legend.Position = xlLegendPositionTop

End With



Sheets("POF(1)-(8) all areas").Select
Dim myChartObjPOF As ChartObject
For Each myChartObjPOF In ActiveSheet.ChartObjects
With myChartObjPOF.Chart
.Export ThisWorkbook.Path &"＼"& .ChartTitle.Text &".png"
End With
Next



Sheets("PI・SUM8(1)-(8) all areas").Select
Dim myChartObj As ChartObject
For Each myChartObj In ActiveSheet.ChartObjects
With myChartObj.Chart
.Export ThisWorkbook.Path &"＼"& .ChartTitle.Text &".png"
End With
Next





End Sub

With regard to recordable optical discs, the following effects are expected to contribute to the inference of facts in appraisal work.
(1) If it is claimed that a file that should have been recorded has been lost, but no evidence of this can be found through digital forensics and the deleted data cannot be restored, then if error measurements are carried out and an error pattern chart is created, and it is determined that the amount of error patterns is commensurate with the capacity of the current readable files, then it can be presumed that there is no evidence that the recorded files have been deleted.
(2) When the observed error pattern does not match the current amount of readable files, it may be possible to infer the possibility of file deletion, as in the case of Figure 4 above.
(3) As an application, for example, in the case of Figure 4, if the person who recorded and deleted the files states that he recorded and then deleted files (1), (2), (3), and (4), and did not record the fifth or subsequent files, this can be supported by the error pattern chart.
(4) If it is indicated that an uncorrectable error, such as an extremely large error pattern, has occurred in the final recording portion of the last session, it may be possible to infer that an accident, such as a forced interruption of writing, has occurred and the session has terminated abnormally.
(5) For originals recorded in separate sessions, an error print chart like the example given in the previous section can be obtained. On the other hand, for copies, whether they are copied using a computer or a duplicator, if the entire process is recorded in one go from the start point to the end point, the error print pattern for each session will differ from that of the original. Therefore, it may be possible to distinguish between originals and copies by the error print.
(6) If the original is created in a write-once format and then turned into evidence, and then a new file is added using another computer or other device to tamper with the document, an error pattern chart may show a step in the error pattern in the tampered area or a large error pattern at the joint, which may be useful in discovering and proving the tampering.
(7) If a very large spike-like error is observed on the error pattern chart, it may be possible to discover and prove that a write session has ended (including an abnormal end) at that location, or that a temporary write interruption has occurred to prevent a buffer underrun, and that a new write may have been performed.
(8) If the error pattern chart has a stepped pattern corresponding to the total session size estimated from the file size that can be read from the disc, it may be useful for single-layer DVDs and BDs to discover and prove the possibility that different drives were used for recording each session. However, as an exception to multi-layer DVDs and multi-layer Blu-rays, the error pattern chart for dual-layer DVD-R-DL 8.5GB and BD-R-DL 50GB, triple-layer BD-R-XL 100GB, and quadruple-layer BD-R-XL 128GB has a stepped pattern at the change of layers. On the other hand, this may be useful for discovering and proving the possibility that different drives were used for recording each session, as long as the step position does not coincide with the seam of the layers.
(9) It is possible to create a digital watermark for individual identification by utilizing the nature of errors that occur due to out-of-synchronization.
(10) It is possible to create optical disks that are individually identifiable by utilizing the nature of errors that occur due to out-of-synchronization.
(11) Disks with the same hash value can be identified by their error prints.
(12) When data on a video recording disk is damaged and cannot be restored, and analysis using conventional digital forensic tools is not expected, the analysis method using the error pattern chart in this case can determine what percentage of the entire area the error traces cover, and this can be used as evidence in litigation, etc. to determine what percentage of the maximum recording capacity was recorded.

001 Error counting drive 002 Personal computer with error pattern chart creation application program installed

Claims (5)

A method for identifying and verifying optical disks that are experiencing problems with reading data on the entire disk or on a portion of it, which utilizes the following characteristics: errors that occur during the recording and reading process of an optical disk are observed over almost the entire disk; when error measurements are traced from the inner peripheral address, the recording time series and the error measurement time series match; traces of a data recording session even when data cannot be read, and the time series are contained and stored in the error distribution; and the distribution reflects the recording history that occurred on the disk. This method uses an error pattern chart for optical disks to identify whether or not a data recording session has occurred in the section from the start to the end of the user data area where data reading is experiencing problems, and to infer the amount of data recorded or the recording time of that session. This is a part of an instrument used to verify and examine optical disks that have problems reading data on the entire disk or on parts of it. It is characterized by the fact that errors that occur during the recording and reading process of an optical disk are observed over almost the entire disk, that when error measurements are traced from the inner peripheral address, the recording time series and the error measurement time series match, that even if data cannot be read, there is evidence that a data recording session occurred, and that this time series is contained and stored in the error distribution, and that the distribution reflects the recording history that occurred on the disk. It is an optical disk error pattern chart that utilizes these properties to show whether or not a data recording session occurred in the section from the start to the end of the user data area where data reading is impaired, as well as the recording volume or recording time of that session. This is an application program for creating error pattern charts for optical disks, which is a part of an instrument used to verify and examine optical disks that have problems reading data on the entire disk or on parts of it, and which utilizes the characteristics that errors that occur during the recording and reading process of an optical disk are observed over almost the entire disk, that when error measurements are traced from the inner peripheral address, the recording time series and the error measurement time series match, that even if data becomes unreadable, there is evidence that there was a data recording session, and that time series is contained and stored in the error distribution, and that the distribution reflects the recording history that occurred on the disk, to show whether there was a data recording session or not, and the recording amount or recording time of that session in the section from the start to the end of the user data area where there is a problem reading data, and to display multiple measurements to confirm reproducibility, or the measurement results of multiple disks, overlaid multiple times as necessary. A method for identifying individual copies of optical discs, characterized by the use of an error pattern chart for optical discs, taking advantage of the property that errors that occur during the recording and reading process of optical discs can be observed over almost the entire disc and that errors cannot be copied. An electronic watermark that takes advantage of the property that errors that occur during the recording and reading process of an optical disc cannot be copied, and an optical disc that has said electronic watermark embedded in it.