JP4402000B2 - Magnetic recording medium authenticity determination method and magnetic recording medium reading / writing apparatus - Google Patents

Description

  The present invention relates to a method for determining authenticity in a magnetic recording medium such as a magnetic card, and an apparatus for reading / writing authentication information to / from the magnetic recording medium.

  Various cards, such as cash cards, credit cards, prepaid cards, point cards, etc., in which personal information, frequency information of money, etc. are recorded, are widely used. Unauthorized use of these cards due to counterfeiting and alteration has become a major social problem, and countermeasures are required. In a magnetic card for recording information on a magnetic material, it is necessary to read / write information in an environment where the mechanism accuracy and electrical accuracy of the drive system of the read / write device (reader / writer) are low. The amount of information that can be written is small (generally about several hundred bits), the application range is limited, and information can be easily rewritten by a read / write device, so there is a high risk of unauthorized rewriting.

  As countermeasures against such unauthorized use, various technologies have been developed and proposed in the past, but many of these technologies are not compatible with magnetic cards that have been widely used so far in terms of manufacturing methods and operations. Therefore, most of them cannot be used under the prevalent infrastructure.

  Therefore, the present inventor can immediately detect that there has been an unauthorized use by someone other than himself / herself or an unauthorized rewrite of the recorded contents, and still maintain a certain degree of compatibility with conventional magnetic cards. We have developed and proposed a magnetic card authentication method, authentication system, and magnetic card that can be authenticated in this way. Such a technique proposed by the present inventor is such that, as disclosed in International Publication No. WO03 / 102925 A1, a magnetic card data is written with noise superimposed thereon, and waveform disturbance due to motor wobbling at the time of reading is performed. The signal component is extracted after normalization, and the noise component is analyzed and converted into data.

  In the writing of magnetic data, the write signal is normally performed by two waves of 1F and 2F (a signal having a frequency twice as high as 1F) generated from an accurate clock. Due to the characteristics of individual heads at the time of writing, variations in the drive system, etc., the exact length is not one to two. Since this is slightly different each time it is written, it can become a characteristic characteristic of magnetic data. Therefore, various techniques for preventing forgery of a magnetic card using this have been proposed. For example, Japanese Patent Application Laid-Open No. 10-149417 discloses a technique for achieving a forgery prevention effect by encrypting and recording the jitter of a magnetic signal recorded on a magnetic card on the magnetic card. .

International Publication Number WO03 / 102925 A1 JP-A-10-149417 Japanese Patent Application No. 2004-307030

  However, in the technique previously proposed by the present inventor, since the frequency of the noise component is overwhelmingly higher than the data waveform, a device capable of handling a higher frequency is required as compared with the conventional reader and writer. There is a problem. In addition, there is a problem that the reliability of the noise component becomes lower than the reliability of the data with respect to the deterioration of the read conditions such as dirt, dirt, breakage, and bending attached to the read head and the card.

  Further, in the technique disclosed in Japanese Patent Application Laid-Open No. 10-149417, etc., a waveform deviation at the time of reading, such as an advanced reading device, an influence of a peak shift or the like that occurs when reading is actually performed, is better. It is large and not yet put into practical use.

  An object of the present invention is to provide a magnetic recording medium read / write device and a magnetic recording medium authenticity determination method that solve the above-described problems and are difficult to forge or alter.

  A first invention is a magnetic recording medium authenticity determination method for determining the authenticity of a magnetic recording medium in which data is magnetically recorded in a recording area composed of a plurality of tracks. A modified data creation step for creating a plurality of modified data by modifying at least one of the data based on a predetermined rule by a plurality of methods, and storing information associated with each modified data and each modification method And a modified data selection step for selecting modified data suitable for adding authenticity determination information among the plurality of modified data, and a portion of the modified data selected in the modified data selection step Information indicating whether the authenticity determination information is added and the authenticity determination information is added to the signal peak in a manner of shifting the signal peak in time Storing, authenticating information adding step, modified data to which the authenticity determining information is added, and magnetic recording step for magnetically recording the modified data or basic data to which the authenticating information is not added to separate tracks; A data restoration step for reading a signal of data magnetically recorded in the recording area and adding the authentication information, and a data restoring step for restoring the modified data or basic data to which the authentication information is not added; An interpolation curve creating step for creating an interpolation curve based on the peak timing of the portion where no peak shift has occurred among the data signals to which the authenticity determination information is not added, and the restored modified data signal Magnetic recording by comparing the peak of the modified data to which the authentication information is added to the interpolation curve. Characterized in that it comprises a authenticity determination step of determining authenticity of the body.

  A second invention is a magnetic recording medium authenticity determination method for determining the authenticity of a magnetic recording medium on which data is magnetically recorded in a recording area, wherein one basic data is divided into a plurality of types based on a predetermined rule. A plurality of modified data is created by modifying by the method, and a modified data creating step for storing information associated with each modified data and each modified method, and authentication information is added among the plurality of modified data A modified data selection step for selecting modified data suitable for the determination, and a part of the modified data selected in the modified data selection step with authentication information in such a manner that the peak of the modified data signal is shifted in time. And adding the authentication information adding step for storing the information indicating to which part the authentication information has been added, and the revision to which the determination information is added. A magnetic recording step for magnetically recording data in a recording area of a magnetic recording medium; a modified data restoring step for restoring a modified data signal by reading a signal of data magnetically recorded in the recording area; An interpolated curve creating step for creating an interpolated curve based on the peak timing of the portion of the modified data signal where no peak shift has occurred and the authenticity determination information is not added, and the restored And a step of determining the authenticity of the magnetic recording medium by comparing the peak to which the authenticity determination information is added in the modified data signal and the interpolation curve.

  In the first and second inventions, the predetermined rule in the modified data creation step can be based on an M-sequence random number generation method. The interpolation curve may be a cubic spline curve.

  According to a third aspect of the present invention, there is provided a magnetic recording medium reading / writing device for magnetically recording data in a recording area composed of a plurality of tracks, wherein at least one of the basic data recorded on the plurality of tracks is determined according to a predetermined rule. A modified data creating means for creating a plurality of modified data by modifying in a plurality of ways based on the method, and storing information associated with each modified data and each modified method, and among the plurality of modified data The modified data selecting means for selecting the modified data suitable for adding the authentication information, and the peak of the modified data signal is shifted in time to a part of the modified data selected by the modified data selecting means. Authenticity determination information adding means for adding authenticity determination information in an aspect and storing information indicating which part the authenticity determination information is added to; Magnetic recording means for magnetically recording the modified data to which the authentication information is added and the modified data or basic data to which the authentication information is not added on separate tracks; A data restoration means for restoring the modified data to which the authenticity determination information is added by reading the data signal and the modified data or basic data to which the authenticity determination information is not added, and the restored authenticity determination information is added. Interpolation curve creation means for creating an interpolation curve based on the peak timing of the portion where no peak shift occurs in the signal of no data, and authentication information is added to the restored modified data signal And authenticating means for determining the authenticity of the magnetic recording medium by comparing the peak of the modified data with the interpolation curve. To.

  A fourth invention is a magnetic recording medium read / write device in which data is magnetically recorded in a recording area, wherein a plurality of modifications are made by modifying one basic data by a plurality of methods based on a predetermined rule. A modified data creating means for creating data and storing information associated with each modified data and each modification method, and modified data suitable for adding authenticity determination information among the plurality of modified data Authentication data is added to a part of the modification data selection means to be selected and the modification data selected by the modification data selection means in such a manner that the peak of the signal of the modification data is shifted in time, and to which part the authentication data is Authentication information adding means for storing information indicating whether the determination information has been added, and the modified data to which the determination information is added are magnetically recorded in the recording area of the magnetic recording medium. Magnetic recording means for recording the data, modified data restoring means for restoring the modified data signal by reading the magnetically recorded data signal in the recording area, and the peak shift of the restored modified data signal Interpolating curve creating means for creating an interpolating curve based on the timing of the peak of the portion where the authenticity determining information is not added and the authenticity determining information of the restored modified data signal And authenticating means for determining the authenticity of the magnetic recording medium by comparing the peak to which the symbol is added and the interpolation curve.

  In the third and fourth inventions, the predetermined rule in the modified data creating means can be based on an M-sequence random number generation method. The interpolation curve may be a cubic spline curve.

  According to the present invention, when adding authenticity determination information in such a manner that the signal peak is shifted in time, the basic data is modified in a plurality of ways based on a predetermined rule to generate a plurality of modified data. In this case, the modification data suitable for adding the authenticity determination information is selected, and since the authentication information is added to a part thereof, no peak shift occurs after the modification data is restored, and The interpolation curve created based on the peak timing of the part to which the authentication information is not added more accurately reflects the speed fluctuation of the motor. As a result, the part to which the authentication information is added and the interpolation curve The authenticity determination executed by comparing the two is accurate and reliable.

Embodiments of the present invention will be described below with reference to the drawings.
In the following, a magnetic card is taken as an example of the magnetic recording medium, and the authentication information writing method and apparatus for the same of the present invention will be described. The magnetic recording medium that magnetically records the recording medium that requires confirmation of the identity is included.

  FIG. 1 is a schematic view showing a state in which a general magnetic card 10 is inserted into a magnetic card reader / writer (magnetic card writing / reading device). The magnetic card reader / writer is provided with a magnetic head 18, whereby information is written in the magnetic recording area 12 of the magnetic card 10, and information recorded in the magnetic recording area is also read out by the magnetic head 18. . The magnetic recording area 12 is formed of a magnetic material applied directly to the base surface of the magnetic card 10, or a film attached to the base surface of the magnetic card 10 and coated with a magnetic layer. In this example, the magnetic recording area 12 includes three magnetic tracks 12a, 12b, and 12c, but the number of magnetic tracks is not limited to this.

  Basic data for performing the original function of the magnetic card is recorded on the magnetic tracks 12a, 12b, and 12c. This basic data may be read-only or rewritable. If the use of the magnetic card is like a bank cash card or credit card, it will be read-only, and the owner's name, bank account number, credit card number, date of issue, etc. will be recorded in advance as basic data Is done. On the other hand, if the application of the magnetic card is like a prepaid card, the usage amount, usage frequency, etc. are recorded as basic data, and these basic data can be rewritten after the card is distributed.

  Here, with reference to FIG. 2, the principle of the authenticity determination of the magnetic card according to the present embodiment will be described. FIG. 2 is a schematic waveform diagram showing a method of putting a signal of a writing method called “F2F method” and a signal for authenticity determination in this embodiment.

  2, (A) is a logical value of basic data written to the magnetic card, (B) is an original write signal of basic data corresponding to the logical value of (A), and (C) is a write signal of (B). A signal to which information for authenticity determination is added, (D) indicates a reference clock for controlling a basic data write operation and the like. The frequency of the reference clock is F, and the signal waveform corresponding to the logical value “1” of the basic data and the signal waveform corresponding to the logical value “0” are as shown in (B) of the reference clock of (D). In this case, the frequency (2F) of the signal waveform corresponding to the logical value “1” is twice the frequency (F) of the signal waveform corresponding to the logical value “0”. That is, the case where the signal level transition occurs within a certain period (1/2 of the period of the reference clock) indicated by t corresponds to the logical value “1”, and the level transition does not occur during this period. Corresponds to the logical value “0”. By supplying the signal shown in (C) to the magnetic head, the basic data is magnetically recorded on the magnetic card.

  As can be seen from the original write signal in FIG. 2B, a signal level transition always occurs between the bits of the basic data. Therefore, in the present embodiment, the signal level transition timing between a predetermined bit (only one is preferable, but it is generally preferable to determine about several tens) and the next bit. A signal for authenticity determination is added in such a manner that is intentionally shifted. In the example of FIG. 2C, the transition timing is shifted in a direction that is delayed by a predetermined timing at time t1 and time t2. As described above, whether the magnetic card is genuine or forged is determined depending on whether or not there is a shift in timing of signal level transition between a specific bit and the next bit.

  It should be noted that such a timing shift amount of about several percent is sufficient. On the other hand, there is no inconvenience in recognition of basic data even if there is such a shift. In FIG. 2C, the timing is shifted in the direction of delaying the timing, but it is of course possible to shift it in the direction of increasing the timing.

  Incidentally, a so-called “peak shift” phenomenon as shown in FIG. 3 occurs in a signal obtained by reading magnetically written information based on the F2F method. FIG. 3C shows the case where the write signal shown in FIG. 3B (the same as FIG. 2B, information for authenticity determination is not added) is written to the magnetic card and read. The signal waveform obtained is shown. As shown in PS1 to PS4 in FIG. 3C, the peak shift is a peak of a signal existing between a short period part (high frequency part) and a long period part (low frequency part). This is a phenomenon that shifts to the longer period side. When this is considered corresponding to the basic data of (A), the peak shift occurs in the portion where the data transitions from “0” to “1” and the portion where the data transitions from “1” to “0”. On the other hand, no peak shift occurs at a portion where the data transitions from “0” to “0” or a portion where the data transitions from “1” to “1”.

  Therefore, it is not preferable to put authentication information for shifting the timing of level transition on the part where such a peak shift occurs, and it is desirable that the part where the authentication is put be a part where no peak shift occurs.

  Further, as described above, a general magnetic card reader / writer has low mechanism accuracy and electrical accuracy of the drive system, and the speed of the motor that carries the magnetic card varies considerably. Such fluctuation occurs particularly in the initial stage when the conveyance is started, during the conveyance, and at the final stage when the conveyance is stopped. Therefore, even if the write signal has the original timing based on the reference clock as shown in FIG. 3B, the magnetic information is not necessarily stored in the magnetic recording area due to such a change in the conveyance speed. It is not recorded uniformly.

  In addition, since the change in the conveyance speed occurs at the time of reading out the magnetic information, the timing of the signal obtained by reading the magnetic information is greatly deviated from the initial one. Even if there is such a change in the conveyance speed, there is no problem because the specifications are formulated in advance so as not to hinder the writing and reading of the basic data. However, when a signal for authenticity determination is added in such a manner that the signal level transition timing is intentionally slightly shifted, such a change in the conveyance speed can be a major obstacle to the determination of authenticity.

  Therefore, in the present embodiment, the position to which the authentication information is added is found by compensating for such a change in the conveyance speed. As a method, a plurality of peaks that do not cause peak shift and are not added with information for authenticity determination are extracted from a signal obtained by reading from a magnetic card, and an interpolation curve is obtained using these. The shape of the interpolation curve obtained in this way corresponds to the fluctuation of the conveyance speed. Therefore, even if the peak appears to be out of sync, the peak shift does not occur at this point as long as it is on this interpolation curve, and information for authenticity determination is also added. I understand that it is not. The most general example of the interpolation curve is a cubic spline curve.

  On the other hand, even if it seems that the peak does not appear to deviate at a glance, if it is found that it is far from the interpolation curve as a result of comparison with the interpolation curve, it is judged whether the peak is shifted or the authenticity is determined. Information for is either added. In this case, as described above, since the portion where the peak shift occurs can be known in advance, if such a peak is excluded, it can be identified whether or not information for authenticity determination is added. .

  Furthermore, in order to be able to compensate the conveyance speed described above, it is premised that the obtained interpolation curve is accurate. In order to obtain an accurate interpolation curve, it is desirable to have as many points as possible. However, as described above, a peak where a peak shift occurs or a peak with information for authenticity determination cannot be used. The number of points that can be used for drawing the interpolation curve depends on the distribution of logical values “1” and “0” in the basic data. For this reason, if the number of peaks where no peak shift occurs is not sufficient, an accurate interpolation curve cannot be drawn, and as a result, the reliability of authenticity determination is affected.

  Therefore, in this embodiment, such a problem is solved by the method described below. FIG. 4 is a signal waveform diagram for explaining the authenticity determination of the magnetic card according to the present embodiment. In the figure, (A) shows an example of basic data. On the other hand, (B) shows an example of modified data obtained by modifying the content of the basic data shown in (A) by a basic data modifying unit described later. (C) shows the driver output waveform of the modified data shown in (B), that is, the waveform of the write signal. However, information for authenticity determination is not added to the waveform of (C) here.

  FIG. 4D shows a signal waveform obtained by reading magnetic information from the magnetic card on which the write signal shown in FIG. 4C is recorded. However, (D) does not include deviation information other than the peak shift (for example, deviation due to a change in the conveyance speed of the motor or deviation due to other external factors). When the write signal shown in FIG. 4C and the read signal shown in FIG. 4D are compared, “1” is changed to “0” at time t1, and “0” is changed to “1” at time t5. Therefore, there is a peak shift in the direction indicated by the arrow.

  Considering a set of three time points t1, t2, and t3 in the read signal shown in FIG. 4D, a peak shift occurs at t1 and the peak shifts, and there is no peak shift at t2 and t3. In a situation where the amount of peak shift cannot be accurately grasped, even if the temporal position of t3 is accurate, since the position of t1 is shifted, there is t2 from the temporal positions of t1 and t3. The power position cannot be determined accurately. Similarly, considering three time points t3, t4, and t5 as a set, the peak of t5 is shifted due to the peak shift, and t3 and t4 are not deviated. Therefore, even if the temporal position of t3 is accurate, since the shift occurs at the position of t5, the position where t4 should be cannot be accurately determined from t3 and t5.

  On the other hand, when the three time points t2, t3, and t4 are considered as a set, no peak shift occurs at all three points. Therefore, the position where t3 should be can be accurately determined from the temporal positions of t2 and t4. That is, the position of t3 can be determined by the interpolation curve derived from the peaks of the read signal waveforms at t2 and t4. From this, when there are four consecutive logical values “0” or “1”, it is possible to grasp the exact position of the peak of the waveform between the second value and the third value. I understand. Of course, the same can be considered when five or more of the same values are connected.

Based on this, FIG. 5 shows an example in which authenticity determination is performed in one track. In the waveform diagram shown in FIG. 5, (A) and (B) are the same as FIG. FIG. 5C shows that the process of shifting the peak of the signal corresponding to the boundary between the third data and the fourth data is performed on the data of (B). That is, as shown in FIG. 5 (D) is a write signal of the data sequence, the third time point of the rear trailing edge of the data, deliberately toward the time only the fourth data indicated by t _ID It is deliberately shifted (in the direction of delay). Then, the authenticity of the magnetic card inserted into the magnetic card reader / writer can be determined or the user of the magnetic card can be authenticated based on the presence or absence of such a signal shift.

  FIG. 5E shows a signal waveform when the magnetic information corresponding to (D) is read. Here, in order to understand the invention, an explanation will be given by using an ideal read signal excluding the influence of a drive system such as a motor or a waveform shift due to an external factor. In the readout signal of FIG. 5E, it can be seen that a peak shift occurs at P1 and P5, and the peak that may contain the authenticity determination information is P3 in which four “0” s are connected. I understand that. Therefore, first, an interpolation curve as a reference is created based on the temporal positions of the four peaks P2, P4, P6, and P7. Then, by comparing the temporal position (position that should be) corresponding to the peak P3 of the interpolation curve with the actual temporal position of P3, if a predetermined deviation occurs, the magnetic card is genuine. On the other hand, if there is no deviation, the magnetic card can be determined to be a counterfeit card in which only basic information is copied.

  FIG. 6 is a diagram showing an example of an interpolation curve that is actually created based on the description of FIG. 5 above. Here, a spline curve is used as the interpolation curve. In FIG. 6, the horizontal axis indicates time, and each vertical line P <b> 1 to P <b> 7 indicates the time when the waveform of the obtained signal waveform peaks for each cycle corresponding to FIG. Yes. On the other hand, lines S1 to S7 parallel to the horizontal axis are reference lines drawn at equal intervals in order to obtain an interpolation curve.

  In FIG. 6, the “x” mark on the vertical line P5 indicates that a peak shift has occurred. The reason why the occurrence of the peak shift can be determined in this way is that it is known in advance from FIG. 5B and FIG. 5C that a transition from the logical value “0” to “1” occurs at this point. It is. Such points are not used to create an interpolation curve. On the other hand, a total of four “◯” marks on P2, P4, P6, and P7 indicate that no peak shift occurs and no authenticity information is included. The “Δ” mark on P3 indicates that no peak shift has occurred as described above, and there is a possibility of including authenticity information.

  First, an interpolation curve (solid line) is drawn using the four points indicated by “◯” in FIG. Subsequently, an interpolation curve (dotted line) is drawn using the five points indicated by “◯” and “Δ”. Then, these two curves are compared. As a result, if it is determined that there is a large deviation at the point Δ, this is because the authenticity information is included at this point. Since it is known in advance whether or not the authentic information is included, if it is determined that there is no deviation like the “△” mark on P3 at the point where the authentic information should be included, the card is forged. Or it turns out that the possibility of having been altered is high.

  In the above, two interpolation curves were drawn and the curves were compared with each other, but only the first interpolation curve was drawn, and the point that included the authenticity information in advance was on this interpolation curve. It is also possible to determine the authenticity of the card by examining only whether or not.

  Next, a magnetic card reader / writer to which the method described above is actually applied will be described. FIG. 7 is an overall block diagram of the magnetic card reader / writer according to the first embodiment. The magnetic card reader / writer shown in FIG. 7 is an example in the case of executing authenticity determination using two tracks. In general, different basic data is written in these two tracks.

  In FIG. 7, an external interface (I / F) 21 is a circuit for communicating with the outside, and performs input / output of signals such as input of basic data, the result of authenticity determination, and output of read data. The reader / writer main control unit 22 is responsible for the main control of the magnetic card reader / writer. Upon receiving a request for writing / reading basic data via the external interface 21, the reader / writer main control unit 22 controls the drive motor (not shown). Controls data input / output.

  The basic data modification unit 23 modifies the content of the basic data input from the external interface 21. Specifically, a known random number generation method called an M series can be used. That is, an initial value and basic data, which are sequentially selected from a plurality of initial values stored in advance in the initial value table 24, are substituted into a predetermined formula to create a data sequence having the same number of bits as the basic data. Is stored in the modified data storage unit 25. The number of pieces of modification data to be created can be determined according to each application. However, even if 256 pieces of modification data are created, the burden on the reader / writer main control unit does not become so large. Here, both basic data written in the two tracks A and B are modified and stored in the modified data storage unit 25.

  Each modified data stored in the modified data storage unit 25 is added with the initial value used for modification, for example, at the end. This initial value is required when returning the modified data to the original data. Instead of adding this initial value to the modified data, it is stored, for example, on a dedicated server or the like via a network, and when the modified data is restored to the original data, the initial value is read again via the network. It can also be in the form.

  The optimum modified data selection unit 26 examines the plurality of modified data stored in the modified data storage unit 25, and selects desirable modified data for adding the authenticity determination information from among the modified data. Here, various factors can be considered as the determination criterion of “modified data desirable for adding authenticity determination information”. For example, select a basic data with a small peak shift, or if there is no peak that can add authenticity determination information such as peak P3 in FIG. Various criteria can be set based on whether these criteria are appropriately combined or whether the above-described interpolation curve can be accurately drawn. It is also possible to examine all the modified data and select the most appropriate one, but if it finds one that satisfies a certain standard that the interpolation curve can be drawn to a certain degree of accuracy, select it. Also good. In this way, the processing time can be shortened.

  Note that the processing performed in the basic data modification unit 23 is not limited to using M-sequence random numbers, and various other methods are conceivable at the present time, so the present invention is limited to those using M-sequence random numbers. Not.

  The write data creation unit 27 writes the modification data to be written on the track A by adding the information for authenticity determination held by the authentication determination information unit 28 to the modification data selected by the optimum modification data selection unit 26. Create data. On the other hand, for the modified data written to the track B, a write signal is created without adding authenticity determination information. As described above, information for authenticity determination is added in such a manner that a predetermined number of portions where the peak shift of modified data is known not to occur are extracted by a predetermined number and the level transition timing in this portion is shifted by a predetermined amount. Is done. The information for authenticity determination added here (which part of the timing is shifted or the shift amount) is stored in the authenticity determination unit 35 and used in the subsequent authenticity determination processing.

  The authenticity determination information unit 28 is a part that holds information for authenticity determination. As the information for authenticity determination, for example, information such as what number, what number, and what number of peaks in which a peak shift has not occurred is added. For example, if a random number circuit etc. is built in and what information is added to what part of the modified data is generated randomly as information for authenticity determination without going through artificial elements, the card The forgery prevention effect can be further enhanced.

  Instead of providing the authenticity determination information unit 28 inside the magnetic card reader / writer, the authenticity determination information unit 28 is separated from the magnetic card reader / writer. It is also possible to store the information in the unit 28 and access the authenticity determination information unit 28 via the network again when executing the authenticity determination.

  The drivers 29A and 29B drive the magnetic heads 18A and 18B based on the write data created by the write data creation unit 27, respectively. The magnetic heads 18A and 18B receive the control of the drivers 29A and 29B at the time of writing, and actually write data to the tracks A and B of the magnetic card 10, and at the time of reading output the signals read from the tracks to the amplifiers 31A and 31B. The amplifiers 31A and 31B amplify signals read from the magnetic card by the magnetic heads 18A and 18B to a predetermined level, but are not essential to the present invention.

  The read signals amplified by the amplifying units 31A and 31B are sent to the modified data restoring units 32A and 32B, and the modified data shown in FIG. 4B is obtained from the respective waveforms read by the heads 18A and 18B. Restore. The restored modified data is sent to the peak identifying units 33A and 33B, where a peak where a peak shift has occurred and a peak where no peak shift has occurred are identified based on the restored modified data. The That is, in the restored modified data, the part that transitions from “0” to “1” and the part that transitions from “1” to “0” are identified as the part where the peak shift occurs, The part other than is identified as a part where no peak shift occurs.

  Information regarding the peak identified as having no peak shift by the peak identifying unit 33B is sent to the interpolation curve creating unit 34, where an interpolation curve such as a cubic spline curve is created. As described above, the authentication information is not added to the information recorded in the track B, and even if a deviation occurs in the peak of the signal waveform read from the track B, it is not due to the peak shift. This is due to external factors such as fluctuations in the conveyance speed. The interpolation curve reflects such external factors. Similarly, for the signal from the track A in which the same peak shift occurs due to an external factor, the authenticity determination can be performed as follows using this interpolation curve.

  The authenticity determination unit 35 receives information on the peak of the signal waveform read from the track A from the peak identification unit 33A and receives information on the interpolation curve for the track B from the interpolation curve creation unit 34. The authenticity determination unit 25 also receives information related to the peak to which the authenticity determination information is added from the write data creation unit 27. Based on these pieces of information, it is determined whether or not the peak of the signal waveform read from the track A, to which the authenticity determination information is added, is on the interpolation curve.

  As described above, since the peak corresponding to the portion to which the authentication information is added is intentionally shifted, it should not be on the interpolation curve. On the other hand, if the malicious user reads the basic data from the original owner's magnetic card in some way and copies it, the basic data is the same. Since no authenticity determination information is added, the peak shift at that portion is only due to an external factor, which should be on the interpolation curve as described above. Of course, it is possible to add authenticity determination information to a plurality of positions and determine that the magnetic card is authentic even when a predetermined condition is satisfied for all of them, and in this way, the safety is further enhanced.

  Further, for example, if the position where the authentication information is added is changed for each bank, and the reader / writer recognizes where the authentication information is added, when the card is inserted. It is also possible to recognize where the bank that issued the card is, and to use the authentication information in this manner.

  The authenticity determination unit 35 determines the authenticity of the inserted magnetic card by such a method, and when it is determined that the card is a fake magnetic card, the subsequent processing is rejected. On the other hand, if it is determined that the magnetic card is a genuine magnetic card, the modified data is sent from the modified data restoration unit to the basic data restoration unit 36. The basic data restoration unit 36 refers to the initial value added to the end of the modified data when stored in the modified data storage unit 25, and restores the original basic data using this. The subsequent processing is the same as that of a normal magnetic card reader / writer.

  In the first embodiment described so far, the authenticity determination is performed based on the information written in the two tracks. However, in the second embodiment below, the magnetic card is based on only a single track using the same concept. Authenticity is determined. FIG. 8 is a block diagram showing the entire magnetic card reader / writer according to the second embodiment. In the following description, detailed description of the same parts as those in the embodiment shown in FIG. 7 is omitted.

  The write data creation unit 107 finds a part in which the information for authenticity determination can be written from the modified data selected by the optimum modified data selection unit 106, and the authenticity held by the authenticity determination information unit 108 in that part. Write data is created by adding information for determination. As in the case of the first embodiment, the information for authenticity determination is added in such a manner that the signal level transition timing is intentionally shifted. The authenticity determination information added here is stored in the authenticity determination unit 121. Here, the “writable part” is, for example, a part in which four or more (bits) of the same data (“0” or “1”) is connected.

  The modified data restoration unit 118 restores the modified data as shown in FIG. 4B from the signal waveform read by the magnetic head 18. The restored modified data is sent to the peak identifying unit 119, and here, based on the restored modified data, a peak where a peak shift has occurred and a peak where no peak shift has occurred are identified. That is, in the restored modified data, the part that transitions from “0” to “1” and the part that transitions from “1” to “0” are identified as the part where the peak shift occurs, Other portions are identified as portions where no peak shift occurs.

  However, the difference from the first embodiment is that the peak identifying unit 119 is added with the authenticity determination information among the peaks for which no peak shift has occurred, based on the information provided from the write data creation unit 107. In addition, the peak is also identified.

  The interpolation curve creation unit 120 creates an interpolation curve such as a cubic spline curve, for example, based on the peak that has been identified by the peak identification unit 119 and has no peak shift. Note that when creating an interpolation curve, the peak identified by the peak identifying unit 119 as having been added with the authenticity determination information is removed in advance. This is because such a peak cannot be used to create an interpolation curve because the signal level transition timing is intentionally shifted. The shape of the interpolation curve obtained in this way reflects external factors such as fluctuations in the conveyance speed, as in the first embodiment.

  When such an interpolation curve is obtained, the authenticity determination unit 121 determines that no peak shift has occurred by the peak specifying unit 119 and shifts the authentication information to any peak given from the write data creation unit 107. The authenticity determination is performed by checking whether these peaks are on the interpolation curve using the information indicating whether or not these are added.

  As described above, in the second embodiment, not only a single track can be used for high-security authenticity determination, but also, for example, in the case of a magnetic card having three tracks, The authenticity determination of Embodiment 2 described can be applied. In this way, the effect of preventing unauthorized use and counterfeiting is further enhanced than in the case of the first embodiment.

  A magnetic recording medium read / write device and a magnetic recording medium authenticity determination method according to the present invention include a read-only magnetic card such as a cash card or a credit card used in a bank, and a prepaid card for viewing a television in an accommodation facility. And rewritable magnetic cards such as prepaid cards with money amount information used at game halls, etc., which can be used in recording media that record information magnetically and require identification / authentication of the recording medium In particular, it can be used more effectively in cases where it is necessary to prevent forgery and unauthorized tampering.

It is the schematic which showed the state in which the general magnetic card | curd 10 was inserted in the reader / writer for magnetic cards. It is a schematic waveform diagram showing a method of putting a signal of a writing method called “F2F method” and a signal for authenticity determination. It is a wave form diagram for demonstrating what is called a "peak shift". It is a wave form diagram for demonstrating the modification data suitable for adding authenticity determination information. It is the wave form diagram which showed the modification data and the method of adding the authentication information to this. It is the figure which showed the example of the interpolation curve actually produced. 1 is an overall block diagram of a magnetic card reader / writer according to Embodiment 1. FIG. FIG. 5 is a block diagram showing an entire magnetic card reader / writer according to a second embodiment.

Explanation of symbols

10 Magnetic card 12 Magnetic recording area 18, 18A, 18B Magnetic head 21, 101 External I / F
22, 102 Reader / writer main control unit 23, 103 Basic data modification unit 24, 104 Initial value table unit 25, 105 Modification data storage unit 26, 106 Comfortable modification data selection unit 27, 107 Write data creation unit 28, 108 Information section 29A, 29B, 109 Driver 31A, 31B, 111 Amplifier 32A, 32B, 118 Modified data restoration section 33A, 33B, 119 Peak identification section 34, 120 Interpolation curve creation section 35, 121 Authentication determination section 36, 122 Basic data restoration Part

Claims (12)

A method for determining the authenticity of a magnetic recording medium for determining the authenticity of a magnetic recording medium in which data is magnetically recorded in a recording area comprising a plurality of tracks,
Thereby creating modified data modified based on at least one predetermined rule of the basic data to be recorded on said plurality of tracks, to store information linked to the method of the modified data and the modified, altered data creation step When,
Some of the modified data created in said modified data creation step, was added to the authenticity determination information which parts with the addition of authenticity determination information in a manner that shifting the peak of the signal peak shift is not generated in time Authenticating information adding step for storing information indicating whether or not,
A magnetic recording step for magnetically recording the modified data to which the authentication information is added and the modified data or basic data to which the authentication information is not added on separate tracks;
A data restoration step for reading a signal of data magnetically recorded in the recording area and adding authenticity determination information; and a data restoring step for restoring modified data or basic data to which no authenticity determination information is added;
Interpolation that creates an interpolation curve based on the peak timing of the portion of the restored data signal to which no authentication information is added and no peak shift has occurred and no authentication information is added A curve creation step;
An authenticity determination step of determining the authenticity of the magnetic recording medium by comparing the peak of the modified data to which the authenticity determination information is added in the restored modified data signal and the interpolation curve;
A method for determining the authenticity of a magnetic recording medium, comprising:   The magnetic recording medium authenticity determination method according to claim 1, wherein the predetermined rule in the modified data creation step is based on an M-sequence random number generation method.   The magnetic recording medium authenticity determination method according to claim 1, wherein the interpolation curve is a cubic spline curve. A method of determining the authenticity of a magnetic recording medium for determining the authenticity of a magnetic recording medium in which data is magnetically recorded in a recording area,
One of the basic data as well as create a modified data by modifying, based on a predetermined rule, stores the information that combines the method of the modified data and the modified, and the modified data creation step,
Some of the modified data created in said modified data creation step, was added to the authenticity determination information which parts with the addition of authenticity determination information in a manner that shifting the peak of the signal peak shift is not generated in time Storing the information indicating whether or not the authentication information is added,
A magnetic recording step for magnetically recording the modified data to which the determination information is added in a recording area of a magnetic recording medium;
A modified data restoring step of reading a signal of data magnetically recorded in the recording area and restoring a signal of modified data;
An interpolation curve creating step for creating an interpolation curve based on the peak timing of the portion of the restored modified data signal where no peak shift has occurred and the authenticity determination information is not added,
An authenticity determining step for determining the authenticity of the magnetic recording medium by comparing the peak to which the authenticity determination information is added in the restored modified data signal and the interpolation curve;
A method for determining the authenticity of a magnetic recording medium, comprising:   5. The method of determining authenticity of a magnetic recording medium according to claim 4, wherein the predetermined rule in the modified data creation step is based on an M-sequence random number generation method.   The magnetic recording medium authenticity determination method according to claim 4, wherein the interpolation curve is a cubic spline curve. A magnetic recording medium read / write device for magnetically recording data in a recording area composed of a plurality of tracks,
Thereby creating modified data modified based on at least one predetermined rule of the basic data to be recorded on said plurality of tracks, to store information linked to the method of the modified data and the modified, altered data creating means When,
Some of the modified data created by said modified data generating means, and adds the authentication judgment information which parts with the addition of authenticity determination information in a manner that shifting the peak of the signal peak shift is not generated in time Authentication information adding means for storing information indicating whether or not,
Magnetic recording means for magnetically recording the modified data to which the authentication information is added and the modified data or basic data to which the authentication information is not added to separate tracks;
Data restoration means for restoring the modified data to which the authentication information is added by reading the signal of the data magnetically recorded in the recording area, and the modified data or the basic data to which the authentication information is not added;
Interpolation curve creating means for creating an interpolation curve based on the peak timing of the portion of the data signal to which the restored authenticity determination information is not added and where no peak shift occurs,
An authenticity determination means for determining the authenticity of the magnetic recording medium by comparing the peak of the modified data to which the authenticity determination information is added in the restored modified data signal and the interpolation curve;
A magnetic recording medium reading / writing device comprising:   The magnetic recording medium read / write device according to claim 7, wherein the predetermined rule in the modified data creating unit is based on an M-sequence random number generation method.   The magnetic recording medium read / write device according to claim 7, wherein the interpolation curve is a cubic spline curve. A magnetic recording medium read / write device in which data is magnetically recorded in a recording area,
Thereby creating modified data by modifying the basis of one of the basic data on a predetermined rule, stores the information that combines the method of the modified data and the modified, and the modified data generating means,
Some of the modified data created by said modified data generating means, and adds the authentication judgment information which parts with the addition of authenticity determination information in a manner that shifting the peak of the signal peak shift is not generated in time Authentication information adding means for storing information indicating whether or not,
Magnetic recording means for magnetically recording the modified data added with the determination information in a recording area of a magnetic recording medium;
A modified data restoring means for reading a signal of data magnetically recorded in the recording area and restoring a signal of modified data;
Interpolation curve creation means for creating an interpolation curve based on the peak timing of the portion of the restored modified data signal where no peak shift has occurred and the authenticity determination information is not added,
An authenticity determining means for determining the authenticity of the magnetic recording medium by comparing the peak to which the authenticity determination information is added in the restored modified data signal and the interpolation curve;
A magnetic recording medium reading / writing device comprising:   The magnetic recording medium read / write device according to claim 10, wherein the predetermined rule in the modified data creating unit is based on an M-sequence random number generation method.   The magnetic recording medium reading / writing device according to claim 10, wherein the interpolation curve is a cubic spline curve.

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