JPH08263927A - Data alteration preventive method - Google Patents

Abstract

PURPOSE: To provide a data alteration preventive method capable of confirming the propriety of the data recorded on a recording medium of DRAW type, such as optical card and preventing the alteration of the data recorded on the recording medium of DRAW type by deciding the presence or absence of the alteration to the recording medium. CONSTITUTION: A complement data C indicating the complement of the number expressed by an owner's identification data A recorded on the optical card is recorded in correspondence to the identification data A on the optical card. The complement data C recorded in corresponding to the identification data A is read out when reading out the identification data A. The presence or absence of the alteration is decided according to whether the number indicated by the complement data C is not the complement of the number indicated by the identification data A described above or not.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of preventing data tampering in a recording medium which can be additionally written.

[0002]

2. Description of the Related Art Conventionally, an optical card capable of additional writing has been known. A direct read-after-write type (hereinafter referred to as DRAW type) is generally used as an optical recording method of data in this type of optical card. Writing to a DRAW type optical card is performed by irradiating an optical recording material with laser light or the like to raise the temperature and causing a physical or chemical change (so-called heat mode recording method).

The "change" referred to here is a so-called irreversible change, and the changed portion cannot return to the original state. Therefore, writing other than addition can be prevented. For example, when bit data "01" is recorded on the optical card, the portion corresponding to "1" on the optical card physically or chemically changes. Since this change is irreversible, it is impossible to change the portion in which "1" is recorded to a state corresponding to other data, that is, "0".

Contrary to the above case, it is possible to physically or chemically change the part corresponding to "0" on the optical card and not change the part corresponding to "1". Needless to say. Also, from the past, DRAW
As an example of the type optical recording material, a low melting point metal simple substance such as tellurium (Te), an alloy thereof, an oxide, a carbide and the like have been proposed.

[0005]

By the way, when bit data "01" is recorded on an optical card, the portion corresponding to "1" changes irreversibly, but the portion corresponding to "0" does not change. . Therefore, the part corresponding to "0" on the optical card can be brought into a state corresponding to "1" by exposing it to the above-mentioned predetermined environment. That is, it is possible to tamper with a portion of the recorded data, which does not change (a portion corresponding to “0”), so as to represent other data.

This is, for example, as shown in FIG.
When the bit data A of "10011" is recorded on the optical card, it means that this data can be falsified into the bit data B of "11011". Moreover, even if such tampering is performed, there is no means or method for detecting it. Therefore, conventionally, a write-once type recording medium such as an optical card is
It can be said that it has a fatal drawback as a medium for recording information that requires high security such as the owner's ID and balance data.

The present invention has been made in view of the above circumstances, and confirms the validity of data recorded on a write-once recording medium such as an optical card, and determines whether the recording medium has been tampered with. By doing so, it is an object of the present invention to provide a data tampering prevention method capable of preventing tampering of data recorded on a write-once recording medium.

[0008]

In a data tampering prevention method according to the present invention, complement data representing the complement of the number represented by digital data recorded on a write-once recording medium is associated with the digital data and recorded. When recorded on a medium, when reading the digital data, the complement data recorded in association with the digital data is read,
It is characterized in that the presence or absence of tampering is determined by whether or not the number represented by the complement data is not the complement of the number represented by the digital data.

[0009]

According to the above data tampering prevention method, digital data and its complement data are recorded in association with each other on a write-once type recording medium. Further, at the time of reading the digital data, the complement data recorded in association with the digital data is read, and if the number represented by the complement data is not the complement of the number represented by the digital data, “tampering is present. If the number represented by the complement data is the complement of the number represented by the digital data, it is determined that “no alteration”.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 is a view showing a sectional structure of an additionally writable, ie, write-once type optical card 1 used in this embodiment. In this figure, from the upper layer, 1a is made of a polyurethane resin having a thickness of 0.2 μm. Surface hardening layer 1b is a transparent substrate of 0.4 mm polyacrylic resin, 1c is a solution of indoaniline metal complex dye in cyclohexanone, and a 1.5% solution thereof is a transparent substrate 1b.
The optical recording layer 1d is formed by applying a phthalocyanine dye to toluene, and a 2.0% solution of the phthalocyanine dye is applied to the optical recording layer 1b. A buffer layer 1e is formed of an epoxy adhesive. The adhesive layer 1f is a backing substrate made of hard vinyl chloride resin.

Recording on the optical card 1 having such a structure operates 830 based on the data to be recorded.
nm semiconductor laser. At this time, in this embodiment, data representing the complement of the numerical value represented by the data is recorded in the optical card 1 in association with the data to be recorded. In this embodiment, the optical card 1 is supposed to record the identification data of the owner and the like in a predetermined format.

Next, the data structure of the optical card 1 will be described with reference to FIG. FIG. 1 is a diagram for explaining a data tampering prevention method according to an embodiment of the present invention, and logically shows a data structure of a medium to which this method is applied. In FIG. 1, A is owner identification data, which is represented by bits A1 to A5, and in this example, "100".
11 ”. C is complement data representing the complement of the identification data A and is represented by bits C1 to C5, which is "01100" in this example. Further, F is an address table of predetermined bits in which the addresses where the identification data A and the complement data C are recorded are recorded.

Next, a card processing system for reading data from the optical card 1 having the above data structure will be described with reference to FIG. FIG. 3 is a diagram showing a schematic configuration of the system, in which 2 is an optical card reader for optically scanning the optical card 1 and reading the data recorded on the optical card 1, and 3 is an optical card. A control device that controls the reader 2 and the information presenting device 4 (described later), and communicates with a host computer (not shown) to perform various processes.
It has a CPU, a ROM, a RAM, various I / O interfaces, and the like. Note that the ROM stores a program executed by the CPU, here, for example, a program for authenticating the identification data of the owner. The information presentation device 4 is, for example, a display or a voice output device,
The information supplied from the control device 3 is presented to the card owner or system administrator.

Next, with reference to FIG. 1, a description will be given of a process in which the system configured as described above confirms the validity of the data recorded on the optical card 1. The above system is
It is assumed that a power source (not shown) has been turned on and is in a standby state. In such a state, when the owner inserts the optical card 1 into a position where the optical card reader 2 can scan, the optical card reader 2 supplies data to that effect to the control device 3.

Upon the supply of the above-mentioned data, the control device 3 supplies the data for reading the contents of the address table F to the optical card reader 2. As a result, the predetermined portion of the optical card 1 where the address table F is recorded is scanned by the optical card reader 2, and the data read by this scanning is supplied to the control device 3. Control device 3
The optical card reader 2 extracts the address table F included in the data supplied from the optical card reader 2 and reads the identification data A and the complement data C recorded at the address represented by the table F. Supply to.

As a result, the portion of the optical card 1 where the identification data A and the complement data C are recorded is the optical card reader 2.
And the data read by this scanning is supplied to the control device 3. The control device 3 extracts the identification data A and the complement data C included in the data supplied from the optical card reader 2, and the value represented by the identification data A and the value represented by the complement data C match. Only if the identification data A is valid, that is,
It is determined that the optical card 1 has not been tampered with.

Here, the basis of the above determination will be described. For example, when the recording unit is irreversibly changed to represent "1" and not changed to represent "0", the value of the bit A2 of the identification data A is set to "0" as shown in FIG. It becomes possible to obtain the identification data A ′ by changing from 1 to “1”. That is, all the parts corresponding to “0” (the parts that have not changed) can be changed to “1”.

By the way, in this embodiment, the complement data C is prepared. Each bit C1 to C of this complement data C
The value ("0" or "1") stored in 5 is always different from the value stored in each bit A1 to A5 of the identification data A. That is, the corresponding bits of the identification data A and the complement data C have contradictory values. From the definition of the write-once type storage medium, in the case shown in FIG.
It is completely impossible to change the part corresponding to "1" to "0".

Therefore, even if the identification data A can be obtained by changing the identification data A, it is absolutely impossible to change the complement data C to correspond to the identification data A '. Of course, even if the complement data C can be changed, the identification data A cannot be changed correspondingly. Since the data structure is designed so that such a premise exists, the correctness can be determined by a simple arithmetic process of whether or not the identification data A and the complement data C satisfy the complement relationship. .

When the optical card 1 shown in FIG. 3 is determined to be a "tampered card" by the above arithmetic processing, the control device 3 transmits the information to the owner or the manager, and the information presenting device 4 is used. Supply predetermined data to. As a result, the information presenting device 4 provides the owner or the manager with information that the card has been tampered with or that the card that has been tampered with has been used.

As described above, according to one embodiment of the present invention, the reliability of important information such as owner identification data can be significantly improved. Further, by confirming the legitimacy of the data recorded on the optical card 1 and surely determining whether or not the optical card 1 has been tampered with, the tampering of the data recorded on the optical card 1 can be prevented.

In the above-described embodiment, the example in which the complement data is not associated with the address table F has been shown, but the same data may be associated to prevent falsification of the address table F. Further, when the data storage position is applied to a recording medium having a predetermined storage position, the address table F may not be provided. Further, it goes without saying that not only the identification data of the owner but also any digital data such as voice or image data may be applied. Therefore, for example, it is possible to set and apply the complement data to the data compressed based on an arbitrary compression algorithm.

Further, in the above-described embodiment, the data recording medium is the optical card, but the present invention is not limited to this, and the CD-R is used.
It is also possible to apply to a write-once medium in which either "1" or "0" is recorded by an irreversible change. Further, not only the identification data and the balance data but also the complement data may be set for all the data recorded on the medium. In this case, the recording capacity of the medium is about half that of the normal case, but the reliability of data is dramatically improved. Further, not only the information presenting device 4 but also an alarm device for notifying the use of the tampered card may be provided. This can further prevent the tampering of the card.

[0024]

As described above, according to the present invention,
Digital data and its complement data are recorded in association with each other on a write-once recording medium. Further, at the time of reading the digital data, the complement data recorded in association with the digital data is read, and if the number represented by the complement data is not the complement of the number represented by the digital data, “tampering is present. If the number represented by the complement data is the complement of the number represented by the digital data, it is determined that “no alteration”. Therefore, by confirming the validity of the data recorded on the write-once type recording medium such as an optical card and judging whether the data is tampered with or not, the tampering of the data recorded on the write-once type recording medium is prevented. There is an effect that can be done.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a data tampering prevention method according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a structure of an optical card 1 used in the same method.

FIG. 3 is a block diagram showing a schematic configuration of a card processing system to which the method is applied.

FIG. 4 is a diagram showing an example of falsification of data recorded on an optical card.

[Explanation of symbols]

 1 Optical Card 2 Optical Card Reader 3 Controller 4 Information Presenter A Identification Data (Bit Data) A'Identification Data B Identification Data (Bit Data) C Complement Data F Address Table

Claims (1)

[Claims] 1. Complementary data representing the complement of the number represented by digital data recorded on a write-once recording medium is recorded on the recording medium in association with the digital data, and the digital data is read at the time of reading the digital data. Reading the complement data recorded in association with the data,
A data tampering prevention method, characterized in that the presence or absence of tampering is determined by whether or not the number represented by the complement data is a complement of the number represented by the digital data.