JP3878970B2 - Prepaid card and counterfeit identification device - Google Patents

Description

[0001]
[Technical field to which the invention belongs]
The present invention relates to a technique for preventing forgery of a prepaid card. When a prepaid card using a magnetic stripe is forged and used, the present invention can identify that the card is forged, a terminal device using the prepaid card, a plurality of terminal devices, The present invention relates to center devices connected by communication means. The present invention can be widely used for telephone cards, pachinko cards, transportation tickets, entertainment tickets, and others.
[0002]
[Prior art]
In recent years, unauthorized use of counterfeit prepaid cards has become a social problem. In particular, in the case of using a card with a magnetic stripe formed, the fraudster analyzes the data recorded on the magnetic stripe of the genuine card and overwrites the new information using a magnetic writer. By falsifying information or the like, a forged card that cannot be distinguished from a genuine card can be created relatively easily. Overwriting the magnetic stripe can be performed relatively easily and in large quantities once a device such as a magnetic writer is available, so the damage can be serious once it is forged by an unauthorized person. Therefore, when a prepaid card is used, the terminal device that reads the information of the prepaid card can identify whether it is a genuine prepaid card or a forged prepaid card, and also an unauthorized person. Requires an authentication method that can never be bypassed.
[0003]
In crime investigations, human DNA and fingerprints are used to identify individuals. this is,
1) DNA and fingerprints are information unique to an individual, and it can be considered that different people have different DNA and fingerprints (uniqueness).
2) DNA and fingerprints cannot be controlled and changed by humans (reproduction difficulty),
3) DNA and fingerprints are permanent and anyone can confirm them (reproducibility),
This is because it satisfies the conditions for identifying an individual.
[0004]
The same thing can be set for prepaid cards. If a feature value equivalent to DNA or fingerprint can be set inside the prepaid card, the terminal device can detect an improperly forged prepaid card. Can prevent in advance.
[0005]
Fernandez discloses in US Pat. Nos. 5,235,166 and 5,430,279 that the jitter that occurs when writing digital information on the magnetic stripe of a card can be used as information that is inherent, difficult to reproduce, and reproducible. did. Jitter generated in the magnetic stripe is a natural phenomenon due to physical unevenness of the magnetic stripe such as fluctuation of the physical thickness of the magnetic stripe, operation unevenness such as the rotation speed of the magnetic writer, unevenness of voltage and current applied to the magnetic writer, etc. Once a prepaid card is created, the jitter is unique, it is difficult to reproduce the same jitter, and once generated, the jitter can be read and reproduced any number of times. It was. Then, the jitter generated in a specific part of the magnetic stripe at the time of preparation of the prepaid card is observed, and the checksum of the jitter (and defined by Fernandez) is made, and this is digital information in another part of the magnetic stripe of the prepaid card. The invention to be recorded as is disclosed.
[0006]
In the conventional invention, when a prepaid card is used, information on the amount recorded in the magnetic stripe is read, and the jitter of a specific portion of the magnetic stripe is actually observed, which is the same as when the prepaid card is created. A checksum is calculated by logic, and it is checked whether or not it matches the checksum recorded as digital information. If they match, it is determined to be a genuine prepaid card, and if they do not match, a forged prepaid card is determined.
[0007]
For example, a fraudulent person purchases a genuine prepaid card, prepares another prepaid card of the same format, and copies all the digital information of the genuine prepaid card onto a magnetic stripe prepared separately. Suppose you make a fake prepaid card that looks exactly like a prepaid card. In many cases, a counterfeit prepaid card created in this way cannot be distinguished from a genuine prepaid card by a terminal device using the prepaid card. However, since the jitter of a specific part of the magnetic stripe is unique for each card, the genuinely purchased genuine one is different from the one created by copying, so the checksum obtained from the jitter of that specific part is It does not match the checksum recorded on the prepaid card. In the above prior art, forgery can be found in this way.
[0008]
[Problems to be solved by the invention]
This anti-counterfeiting method by Fernandez is an effective method, but depending on the number of bits of the checksum, even if it is a counterfeit prepaid card, a checksum that coincides with the jitter of a specific part of the card by chance will be at a certain rate. can get. In addition, the counterfeit prepaid can be used without being discovered if an unauthorized person knows by analyzing the position of the specific part on the magnetic stripe where the jitter is read and the logic of the checksum operation or by leaking the secret. An unauthorized person can create a card.
[0009]
On the other hand, in a prepaid card in which monetary information is recorded as digital information on many magnetic stripes, the monetary unit M (“yen” in Japan, which is dollar or cent in Japan) Units may be reduced). That is, n pieces of money amount information of money unit M (yen) are magnetically recorded so that the total becomes M × n (yen), and this money amount information is rewritten or deleted in units of M yen by use. It has become. That is, a terminal device using a prepaid card has a function of deleting unit amount information or rewriting amount information. Therefore, the specific part for reading the jitter needs to be a part that is not changed until the last monetary amount information is deleted. Therefore, the specific part of the magnetic stripe from which jitter is read must be set to a very limited part, so that the value as a random pattern is lowered. In addition, the position of the specific part is likely to be found by an unauthorized person.
[0010]
Each time the amount information is deleted or rewritten, a specific part can be changed or a new position can be set. However, in this case, the information for selecting the specific part and the above checksum are calculated. It is necessary to set information and other key information in advance in the terminal device, and this increases the possibility of being stolen and used by unauthorized persons.
[0011]
The present invention is made in such a background, and the prepaid card and its counterfeit identification that can greatly reduce the possibility of using a counterfeit prepaid card indistinguishable from a genuine prepaid card. An object is to provide an apparatus. Even if forgery succeeds due to fraud analysis, etc., the present invention has to make a large number of unusable counterfeit prepaid cards and select those that can be used from them. It is an object of the present invention to provide a prepaid card and a counterfeit identification device for which the card cannot be obtained. An object of the present invention is to provide a prepaid card and a counterfeit identification device thereof that can appropriately identify forgery for the remaining amount that can be used even when the amount information is changed by use.
[0012]
[Means for Solving the Problems]
The first aspect of the present invention is a prepaid card. The prepaid card of the present invention is formed on a prepaid card of amount Mn yen in which a magnetic stripe is formed and amount information of the amount unit M yen used for the magnetic stripe is magnetically recorded. At least n random patterns X on the magnetic stripe ₁ , X ₂ , ... X _n ,... Are recorded individually and erasable by the terminal device used. That is, a feature is that a plurality of n random patterns themselves are erased by h each time the amount of money Mh yen is used. In order to create a plurality of n random patterns, the simplest method is to divide a long random pattern into n pieces, but it can also be created by a more complicated method. Erasing by the terminal device can be performed by other methods such as punching holes in the magnetic stripe and overwriting the magnetic stripe.
[0013]
As a result, even when the amount information recorded in the magnetic stripe is rewritten, the random pattern is retained accordingly, and the remaining amount of the prepaid card can be specified in accordance with the number of random patterns.
[0014]
Here, the “random pattern” is a feature quantity that occurs accidentally when a prepaid card is manufactured, and is a random parameter that is difficult to control and functions as a digest of the card. The random pattern needs to be unique, difficult to reproduce, and reproducible. The uniqueness is that there is originally a one-to-one correspondence between patterns and cards, but in reality, the number of cards may be greater than the number of patterns. In that case, even if it is difficult physically and computationally difficult to find another card having the same pattern as that of a certain card, it may be unique. Reproduction difficulty means that it is difficult to intentionally create a specific pattern on another card. Reproducibility is the property that a pattern does not change over the lifetime of one card, and it can be recognized directly from the card by a person who verifies the prepaid card when necessary.
[0015]
The position (and / or magnitude) of pulsed jitter that occurs in the magnetic stripe of a prepaid card is a typical example of a random pattern. In other words, jitter that occurs in the magnetic stripe occurs by chance due to the material and thickness of the magnetic stripe, the nature of the magnetic writer to be recorded, the drive speed of the magnetic writer, drive unevenness, and other causes. The generation position and size are unique. This can be read by a general magnetic reader, and specific jitter cannot be intentionally written by a general magnetic writer. When information is newly overwritten on the magnetic stripe by a magnetic writer, the previous jitter disappears and new jitter is generated in the overwritten portion. For this reason, even if the prepaid card is forged by copying the magnetic stripe, the jitter position and size are different, so the terminal device can determine whether the jitter is true or false by checking the jitter position (and / or size). it can. Jitter can be recognized as pulse-like noise as amplitude information, and can also be recognized as unevenness in clock frequency or clock timing as frequency information or time information.
[0016]
There is a random pattern at the jitter position (and / or magnitude) of the digital information recorded on the magnetic stripe. The position (and / or magnitude) of the jitter can be observed and converted into digital information that can be recorded on the card's magnetic stripe as the card's unique signature. The digital information is preferably created by encryption kept secret. The cipher can be encrypted with a secret key known only to the center device, and can be decrypted with a public key set in the terminal device corresponding to the secret key. The number of random patterns set on the magnetic stripe is desirably n + 1 or more with respect to the prepaid card usable amount Mn circle in order to ensure the identification of the terminal device.
[0017]
When a prepaid card is used, the random pattern obtained by the terminal device used may have already been partially erased by use, but it is sufficient to perform verification using the unerased part. is there. That is, n + 1 random patterns are set for an unused prepaid card, and if there is a signature S encrypted with the secret key for the n + 1 random patterns, the original n + 1 is decrypted when the signature S is decrypted by the terminal device. Random patterns are obtained. The random pattern that can be actually observed by the terminal device from the prepaid card is a portion of n + 1 that is not erased by use, but it can be compared with the corresponding portion of the original n + 1 random patterns. . As the remaining amount decreases, the portion that can be verified decreases, but this is not a problem in practice.
[0018]
A second aspect of the present invention is a counterfeit prepaid card identification device for identifying the validity of a prepaid card. The apparatus of the present invention identifies the validity of a prepaid card of an amount Mn (yen) in which a magnetic stripe is formed and n pieces of money amount information M (yen) used for the magnetic stripe is magnetically recorded. When the user requests the use of the amount Mh (yen), h or more random patterns magnetically recorded on the magnetic stripe of the prepaid card and a signature obtained by encrypting the random pattern Is read from the prepaid card, the means for decoding the signature read by the reading means, the information decrypted by the means for decoding and the random pattern read by the means for reading are collated. Means for determining the validity of the prepaid card and use permission information of the amount Mh (yen) are sent and recorded in the magnetic stripe. Characterized in that a means for erasing a h number of random patterns.
[0019]
Also in this case, the signature is digital information obtained by encrypting the random pattern of the prepaid card with a secret key held in the center device, and the means for determining the validity and the means for deleting the h random patterns are: Provided in a terminal device in which the prepaid card is used, the terminal device includes means for holding a public key corresponding to the private key and decrypting the signature information using the public key.
[0020]
The identification capability can be further improved by providing a communication means for transmitting information on the validity of the prepaid card used in the terminal device between the center device and the terminal device. In other words, the center device has a card identification number ID set at the time of preparation of the prepaid card so that the prepaid card can be individually identified. _C , This card identification number ID _C The prepaid card by comparing the information coming from the terminal device with the database recorded with the signature information S set in the prepaid card in correspondence with the information recorded in the database. And a means for identifying fraud. In the database, the store number ID where the terminal device is installed _s Can be recorded together.
[0021]
With this configuration, when the same prepaid card is played back illegally and used, it can be found by collating it with a record in the database. In addition, if the remaining amount is recorded in the database for each prepaid card, the unauthorized use can be found more surely even though there is a problem with the capacity of the database.
[0022]
A third aspect of the present invention is software recorded on a magnetic medium. That is, it is characterized by a machine-readable storage medium in which software that becomes the above-described counterfeit prepaid card identification device is recorded by being installed in hardware including a program-controlled computer. . The encryption key necessary for the terminal device to decrypt the signature can be recorded on the same storage medium as the recording medium on which the device software is recorded. However, a separate storage is required for encryption key management. It can also be recorded on a medium. The storage medium on which the software is recorded may be a separate storage medium for the terminal device and the center device.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
The prepaid card is formed with a magnetic stripe for writing issue information and fee information. Magnetic stripes are widely used as prepaid cards because they have a small amount of information that can be recorded but are easy to write and the cards themselves are inexpensive. Since the magnetic stripe is a magnetic material, the recorded content is destroyed when it is close to magnetism. In addition, since a magnetic writer for writing information to the magnetic stripe is relatively easily available, there is a problem that it is easily tampered by an unauthorized person. In the case of a prepaid card using a magnetic stripe, the value is aggregated in the data recorded on the magnetic stripe, so when authenticating whether the prepaid card is authentic, unauthorized rewriting of data on the magnetic stripe or If the illegal copy can be verified accurately, forgery of the magnetic prepaid card can be prevented.
[0024]
When information is recorded on the magnetic stripe, pulsed jitter is randomly generated in the magnetic stripe. FIG. 1 schematically shows such a state. This jitter can be read by existing and widely used magnetic readers. However, it is extremely difficult to write jitter at a specific position using a magnetic writer. The jitter existing on the magnetic stripe disappears if it is newly overwritten with a magnetic writer.
[0025]
Therefore, even if a forged prepaid card is made by copying the magnetic stripe, the jitter on the magnetic stripe exists at different positions. When a prepaid card is manufactured, jitter generated in the magnetic stripe after recording on the magnetic stripe is recorded as digital information. Then, when the prepaid card is used, whether or not the prepaid card has been rewritten by checking the jitter position actually observed from the prepaid card at the terminal with the recording by the digital information. Can be identified. This utilizes the fact that the read capability exceeds the write capability with respect to jitter, and in general, a physical quantity that satisfies this fact is likely to satisfy the requirements as a random pulse.
[0026]
In the magnetic prepaid card of the present invention, since this random pattern is used for authenticating the validity of the prepaid card, each prepaid card has a read random pattern, that is, the position of jitter on the magnetic stripe in this embodiment. It is encoded and recorded as digital information. At this time, it is not simply recorded as a digital code, but the jitter position on the magnetic stripe is encrypted with the secret key of the center apparatus and recorded as a signature. This is shown in FIG.
[0027]
In a terminal device using a prepaid card, this random pattern, that is, the position of jitter on the magnetic stripe is actually read from the prepaid card used, and a signature read as digital information from the magnetic stripe is also associated with the secret key. Decrypt with public key. The decrypted data should be a random pattern of the magnetic stripe, that is, a jitter position, and the validity of the prepaid card can be identified based on whether or not this is verified. In a genuine prepaid card, the decoded jitter position should match the read jitter position. If the magnetic stripe is overwritten, the jitter position has been changed, so that the read jitter position does not match the jitter position obtained by decoding the signature. Also, if you observe the jitter position that has been changed by overwriting and try to encrypt it, you cannot create a correct signature without knowing the secret key. .
[0028]
In many prepaid cards, if a user purchases a prepaid card and uses it, the amount information on the magnetic stripe is changed each time it is used multiple times instead of a one-time use. ing. When the amount information is changed, the jitter position is also partially changed from the first one. In this case, the jitter position is not stored until the end. According to the present invention, when the amount information is reduced each time it is used, the information on the jitter position can be effectively used for prepaid card authentication.
[0029]
The amount of the prepaid card is Mn yen, and the unit of use is M yen. Divide the entire random pattern by jitter and divide it into n + 1 individual random patterns X ₁ , X ₂ ... X _{n + 1} And Each random pattern can be erased individually by overwriting with a magnetic writer or punching holes. This is shown in FIG.
[0030]
In the center device, the i-th random pattern X _i And map f is determined from this. The map f is r _i +1 bit (t _i , R _i ). Where t _i Is 1 bit, R _i Is r _i Bit and r ₁ + R ₂ + ... r _{n + 1} = R. t _i Is a bit that determines whether or not the random pattern can be used. _i = 0 is adopted. R _i Is a parameter describing the random pattern. Further, the center apparatus selects a public key method in which both plaintext and ciphertext are composed of r bits, and a secret key K _s And public key K _p Generate a pair with. Keep the secret key strictly confidential.
[0031]
The prepaid card creation of the center apparatus will be described with reference to FIG. From the magnetic stripe in which the digital information of the card being created is written, n + 1 random patterns X ₁ , X ₂ ... X _{n + 1} Read (t _i , R _i ) = F (X _i ), I = 1,..., N + 1. If there is even one i for which t = 1, the magnetic information is rewritten and repeated again. Then R = (R ₁ , ..., R _{n + 1} ) With ambassador private key EK _s With signature S = EK _s (R) is calculated. And the card number ID set uniquely for the card _C , The signature S, and the number j of the first random pattern that can be used (in this case, j = 1) are entered at the end of the magnetic stripe.
[0032]
FIG. 5 illustrates prepaid card authentication by the terminal device. Card number ID from used prepaid card _C , Signature S, and random pattern number j are read. In the figure, '' is added to what is read by the terminal device. (T _i , R _i ) = F (X _i ), I = 1,..., N + 1, and at least one t _i If i exists where = 1, the use of the prepaid card is rejected. A conversion operation using a public key is performed on the read signature S, and R = (R ₁ , ..., R _{n + 1} ) = EK _p R found and read (S) _i And converted R _i If they are equal, use is permitted, and if they are not equal, use of the prepaid card is rejected. EK _p (S) is a public conversion algorithm for the signature S.
[0033]
When the user requests to use Mh yen, if the remaining amount is sufficient, this is permitted, the random pattern is erased up to the hth, and the first usable random pattern is rewritten. When the number of the first random pattern that can be used becomes n + 1, the fact is displayed to the user and the prepaid card is collected.
[0034]
【Example】
FIG. 6 is a block diagram of an apparatus according to an embodiment of the present invention, in which a plurality of terminal devices are connected to one center device through a bidirectional communication path. The terminal device is arranged in the store. As an example, when considering a prepaid card for pachinko, the center device is a prepaid card issuer, the store is a pachinko store, and a plurality of terminal devices may be installed in one store. The terminal device uses a prepaid card purchased and accessed by a customer. That is, a prepaid card is inserted into the terminal device, and the terminal device reads the information on the magnetic stripe or rewrites a part of the information on the magnetic stripe. Both the center device and the terminal device are computer-controlled devices, and a large database is installed in the center device.
[0035]
The amount of the prepaid card is Mn yen, and the unit of use is M yen. In principle, used prepaid cards are collected. Each prepaid card has a long random pattern divided into n + 1 pieces. ₁ , ... X _{n + 1} And Each random pattern can be erased individually. In addition to the random pattern, r + d + α-bit data is entered in each prepaid card. Where r is the number of bits required for the signature S, d is the number of bits required to represent a number from 1 to n + 1, and α is a number ID unique to the prepaid card. _C Is the number of bits required to represent The center device has a database I that can store information of r + d + α + β bits for all currently available prepaid cards, and a database II that stores similar information for used prepaid cards for a certain period of time. β is the store number ID _s Is the number of bits required to represent It is assumed that an administrator and a user of a store or a terminal device may perform fraud.
[0036]
Select a public key method in which both plaintext and ciphertext consist of r bits, and a secret key K _p And public key K _s Generate a pair of Keep the secret key strictly confidential. Random pattern X _i To r _i +1 bit (t _i , R _i ) Is defined. Unique store number ID for the store _s give. Public key K _p , Open conversion algorithm EK _p , And map f are given to each terminal device. Unique device number ID in the store for the terminal device _t give. A bidirectional communication means is prepared between the center device and each terminal device. Between the store and the terminal device, the terminal device for each store confirms normal operation. The databases I and II are prepared.
[0037]
The prepaid card issuance procedure is as follows. n + 1 random patterns X ₁ , ... X _{n + 1} On the card. Read the random pattern and (t _i , R _i ) = F (X _i ), I = 1,..., N + 1. If there is even one i for which t = 1, the process returns to the beginning. R = (R ₁ , ..., R _{n + 1} ) Secret conversion EK _s And sign S = EK _s (R) is obtained. Let j = 1. Where j is the number of the first random pattern that can be used. Unique ID of card _C And print in text so that people can read it. (ID on the magnetic stripe of the card _C , S, j). Store ID that actually sells the card _s Determine. (ID _C , S, j, ID _s ) Into the database.
[0038]
The operation of the terminal device using the prepaid card is as follows. From card (ID ' _C , S ′, j ′). Random pattern X 'from the card _j , ..., X ' _{n + 1} Read (t ', R' _i ) = F (X ′ _i ), I = j ',..., N + 1, and at least one t' _i If i exists, the use of the card is rejected. The signature S ′ is converted by the public key, and R ″ = (R ″ ₁ , ..., n + 1) = EKP _s Find (S '). R ' _i = R " _i Is approved for j 'to n + 1 of i, the card is allowed to be used, and if not, the card is rejected.
[0039]
When the user requests the use of Mh yen, if the remaining amount is sufficient, the use is permitted, the random pattern is deleted from j to j + h, and the number j of the first available random pattern is rewritten to j + h. . When the number of available random patterns reaches n + 1, the fact is displayed and the card is collected. ID 'in the store _C , S ′, j ′, h and the terminal device number ID _t To be notified.
[0040]
The notification from the store to the center device is as follows. The store has an information ID 'about the card used from the terminal device. _C , S ′, j ′, h are received, the validity is confirmed, and the information is stored for a certain period for an audit or the like. If it is not valid, the terminal device is inspected. Its information ID ' _C , S ', j', h are store number IDs _s At the same time, it is sent to the center device through the communication means.
[0041]
The updating and payment of the center device database is as follows. Card number from database I is ID ' _C Item (ID ' _C , S ′, j ′, h). When the item which becomes the card number does not exist in the database I, the database II is searched. If it does not exist in Database II, the payment is rejected as illegal. If it exists in the database II, the following operation is performed on the item. That is, if the signature S is correct and the remaining amount is present, the contents of the data (ID ' _C , S ′, j ′, h). If there is no remaining amount, this information is transferred to Database II and stored for a certain period. Pay the store an amount equivalent to the updated usage. If it is determined that the signature is not valid, the payment is rejected as an illegal input. If the random pattern number j does not match the contents of the database, the accident processing is started.
[0042]
The accident processing of the center device is performed as follows. Card number ID ' _C If it has not been recovered, attempt to recover it. When the card is collected, a determination is made as to which record is correct from the unerased random pattern of the card and the signature. If the card has been collected, consider which store had an accident or fraud based on store records.
[0043]
A numerical example of this embodiment system is as follows. That is, if the total number of prepaid cards that can be used is 10 billion, the number of stores is 100,000, and the maximum amount of the card is 20 M yen, n is 20. If the number of bits of the copy R of the random pattern X is 10 and only the last is 40, the number of bits r for displaying the copy R is 240. The number of bits d required to represent the number of bits from 1 to n is 5, the number of bits α required to represent the card number is 40, and the number of bits β required to represent the store number is about 18. The data to be written is about 400 bits including error correction or check bits. In addition to this, 20 random patterns and 1 random parameter from which a 40-bit parameter can be extracted must be entered on the card. Therefore, the size of the database I is about 500 gigabytes. The database II depends on the storage period of used card information, but requires several times the capacity of the database I.
[0044]
For the number of bits 240 required to represent the random parameter copy R, an elliptical cipher can be used as the public key cipher. Although the security of this encryption is not completely guaranteed, it cannot be easily broken in about 5 to 10 years. Forging a card is not impossible if a pattern of about 2 to the 50th power is prepared, but this requires tens of thousands of times the storage capacity of the database of the center device, and it takes a lot of time to generate data Therefore, forgery that matches the card amount cannot occur.
[0045]
When using a used card to tamper with the amount of money, one random pattern, that is, increasing M yen (for example, 500 yen), is considered to be successful without overwriting about 500 times. . Further, the number of times can be further greatly increased by using a connection portion of a random pattern.
[0046]
[Application example]
When the terminal device knows the secret key, the terminal device can attach a signature similar to that of the center device to the random pattern. Therefore, instead of erasing the used part, there can be a forgery of rewriting a random pattern and adding a signature to it. In this case, a single signature is applied to both the rewritten random pattern and the available amount. There is a way to turn it on.
[0047]
In this method, since any terminal device must be able to generate a valid random pattern, the range of random patterns that can be adopted must be increased. Therefore, in order to increase the security, it is necessary to keep the number of bits describing the random pattern sufficiently large. However, since there is only one random pattern to be written on the card, even if the memory capacity of the card is limited, the random pattern can be made quite large, and if the tamper resistance of the device is not broken, counterfeiting and tampering will occur. There is a good chance that you can make a very difficult card.
[0048]
If the tamper resistance of the store and the terminal device is high, unauthorized seriousness from the store is impossible. The database of the center device has a function that can prevent an illegal report from the store. In this case, the database of the center device can be omitted.
[0049]
To prevent damage to the entire system even if the tamper resistance of the terminal equipment is broken and the secret key is exposed, it is effective to limit one secret key to one store or a specific group. It is. On that occasion, the store or the group can use only the card signed with the private key, but there is a system that can use the card of another store by rewriting the card of the other store with the device of the store. It is done. In order to perform such rewriting, it is necessary to check whether the signature of another store is valid. For this, it is conceivable to make an inquiry to the center device by means of real-time communication means, to make an inquiry directly to other stores, or to equip the terminal device with means for judging the validity of the method of other stores.
[0050]
【The invention's effect】
As described above, according to the present invention, even with a prepaid card that rewrites money amount information each time it is used, authentication using a random pattern is possible up to the final value of the remaining amount, and it is counterfeited practically and economically. It is possible to obtain a prepaid card and an authentication device for which a profit cannot be obtained even if it is performed.
[Brief description of the drawings]
FIG. 1 is a diagram schematically illustrating jitter on a magnetic stripe.
FIG. 2 is a diagram showing a state in which a signature is recorded together with a random pattern on a prepaid card.
FIG. 3 is a diagram for explaining a state in which a random pattern on a magnetic stripe is disabled and decoded data is obtained from a usable portion.
FIG. 4 is a diagram for explaining a procedure for manufacturing the prepaid card of the present invention by the center device.
FIG. 5 is a diagram for explaining a procedure for erasing using a prepaid card of the present invention in a terminal device.
FIG. 6 is a diagram illustrating a state in which a plurality of terminal devices are connected to the center device by communication means.

Claims (11)

In a prepaid card of an amount Mn (yen) in which a magnetic stripe is formed and amount information M of amount unit M (yen) used for the magnetic stripe is magnetically recorded, at least n random numbers are provided on the magnetic stripe. Patterns X ₁ , X ₂ ,... X _n ,... Are recorded individually and erasable by the terminal device used,
The prepaid card , wherein the random pattern is generated based on jitter generated by recording digital information on the magnetic stripe .   The prepaid card according to claim 1, wherein the number of the random patterns is n + 1.   The prepaid card according to claim 1 or 2, wherein the random pattern and information obtained by encrypting the random pattern are recorded as a signature on the magnetic stripe of the card.   The prepaid card according to claim 3, wherein the signature is encrypted with a secret key and can be decrypted with a public key held in the terminal device. An apparatus for identifying the validity of a prepaid card of an amount Mn (yen) in which a magnetic stripe is formed and amount information of the amount unit M (yen) used for the magnetic stripe is magnetically recorded.
When the user requests the use of the amount Mh (yen), the random pattern that is magnetically recorded on the magnetic stripe of the prepaid card and the signature encrypted with the random pattern are read from the prepaid card. And means for decrypting the signature read by the reading means, and verifying the validity of the prepaid card by comparing the information decrypted by the decrypting means with the random pattern read by the reading means And means for sending use permission information of the amount Mh (yen) and erasing h random patterns recorded on the magnetic stripe,
The counterfeit prepaid card identification device , wherein the random pattern is generated based on jitter generated by recording digital information on the magnetic stripe .   The signature is digital information obtained by encrypting a random pattern of the prepaid card with a secret key held in a center device, and the means for determining the validity and the means for erasing the h random patterns are: The counterfeit according to claim 5, wherein the terminal device includes a means for holding a public key corresponding to the secret key and decrypting the signature information using the public key. Prepaid card identification device.   The counterfeit prepaid card identification device according to claim 6, wherein communication means for transmitting information about a prepaid card used in the terminal device is provided between the center device and the terminal device. The center device includes a card identification number ID _C set when the prepaid card is created and set so that the prepaid card can be individually identified, and signature information set for the prepaid card corresponding to the card identification number ID _C 8. A database in which S is recorded, and means for identifying fraud of the prepaid card by comparing information arriving from the terminal device via the communication means with information recorded in the database. Counterfeit prepaid card identification device.   The counterfeit prepaid card identification device according to claim 8, wherein a store number IDs where the terminal device is installed is also recorded in the database.   10. A machine-readable storage medium having recorded thereon software that becomes a counterfeit prepaid card identification device according to claim 5 by being installed in hardware including a program-controlled computer.   The storage medium according to claim 10, wherein an encryption key for the terminal device to decrypt the signature is recorded on the same storage medium or on another storage medium.

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