JP2005346138A - Rf tag, control method of rf tag and communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To specify the security level of information to be recorded in an RFID tag, for each information, and to variably control the strength of a signal to be transmitted according to the security level of the information at the time of reading the information of the RFID tag from a reader/writer. <P>SOLUTION: Information received from a reader/writer 18 is recorded in an RFID tag 1 according to a security level specified by a reader/writer 18, and a control signal 24 is outputted to a load modulating circuit 2 by a controller 5 according to the security level of the recorded information so that the signal strength when the information is transmitted to the reader/writer 18 can be variably controlled. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a technique for transmitting and receiving information between an interrogator and an RF (Radio Frequency Identification) tag.

  Recently, for the purpose of improving the efficiency of logistics, there are plans in various markets to attach RFID (Radio Frequency Identification) tags to products and automate the logistics. Along with this, the manufacturing technology of RFID tags has also greatly advanced, and the unit price of RFID tags has been lowered to a practical level, and demonstration experiments are being started in various markets.

  However, when an RFID tag is attached to a product, it is possible to read information stored in the RFID tag from a remote location, and a third party can read information on the property without the owner of the product being aware of it. Because of this concern, some consumer groups are also opposed to attaching RFID tags to merchandise that may be infringed on privacy.

  As a means for relieving such anxiety of consumer groups, a method has been proposed in which the function of the RFID tag attached to the product is stopped when the product is purchased.

As for the non-contact IC card, as a means for solving the above problem, for example, Patent Document 1 discloses that a non-contact IC card has a proximity function that functions when the interrogator is at a short distance and an interrogator at a long distance. It is described that both functions of a remote function that functions at a certain time are provided and the functions are switched according to security.
Japanese Patent Laid-Open No. 10-312445

  However, the function of the RFID tag has high utility value even after the product purchase, and if the function of the RFID tag is stopped after the product purchase, the merit of the RFID tag cannot be fully utilized. For example, taking the case where RFID tags are attached to clothes as an example, it is possible to grasp the manufacturer and the type and quantity of products with different colors and sizes in the cardboard box without opening the cardboard box during the distribution process. In addition to taking out purchased clothes for cleaning, if the RFID information attached to the clothes is pre-recorded with ID information and information on how to handle it when washing, the cleaning company Not only is it unnecessary to attach a new tag for classification of management and cleaning processing, but also the work of classifying the clothes deposited in the cleaning processing step can be made efficient.

  In addition, when taking a book as an example, there have been many crimes of reselling a book shoplifted at a bookstore to a second-hand seller of a book recently, but in this case as well, whether it was officially purchased at a bookstore or not is attached to the book By recording as information on the RFID tag, it is possible to prevent crimes by refusing to purchase shoplifted books by second-hand sellers.

  Further, in order to configure the two types of functions described in Patent Document 1 relating to the non-contact IC card, there is a disadvantage that not only the cost increases but also the circuit scale increases.

  The present invention has been made to solve the above-described problems. When the security level of information recorded on an RFID tag is defined for each information and the information of the RFID tag is read from a reader / writer, the information The purpose is to variably control the signal strength to be transmitted according to the security level.

  The present invention is an RF tag, a recording means for recording information according to the security level, and a control for variably controlling the signal intensity when transmitting the information to the interrogator according to the security level of the information. Means.

  The present invention is a communication system for transmitting and receiving information between an interrogator and an RF tag, the interrogator having a defining means for defining a security level of information to be recorded in the RF tag, The RF tag records information received from the interrogator according to the security level defined by the interrogator, and transmits the information to the interrogator according to the security level of the recorded information. And control means for variably controlling the signal intensity at the time.

  Furthermore, the present invention is an RF tag control method, comprising: a recording step for recording information received from an interrogator; and a method for transmitting the information to the interrogator according to the security level of the recorded information. And a control step of variably controlling the signal intensity.

  According to the present invention, when the security level of information recorded in the RF tag is defined for each information, and the RF tag information is read from the interrogator, the signal strength to be transmitted is variable according to the security level of the information. By controlling this, information with a high security level can be prevented from being read unless the interrogator is in close contact with the RF tag, and it is possible to protect the privacy and expand the range of use of the function of the RF tag. .

  The best mode for carrying out the invention will be described below in detail with reference to the drawings. In this embodiment, as an RFID tag communication method, an “electromagnetic induction (magnetic field) method” using a coil-type antenna and using a magnetic flux induced between the RFID tag antenna and the reader / writer antenna is used. Will be described as an example.

  FIG. 1 is a block diagram showing a configuration of a reader / writer and an RFID tag in the present embodiment. In FIG. 1, 18 is a reader / writer (hereinafter referred to as an interrogator), and 1 is an RFID tag. The interrogator 18 includes a controller (cont) 12, a parallel-serial converter (hereinafter referred to as P / S converter) 13, an ASK (Amplitude Shift Keying) modulation circuit 14, antennas 17 and 22, a load demodulation circuit 16, and a serial-parallel converter. (Hereinafter referred to as S / P converter) 15. The controller 12 includes peripheral circuits including a CPU, a ROM, a RAM, an I / F circuit, and the like (not shown). The controller 12 transmits and receives data to and from the RFID tag 1 according to a program stored in the ROM. Operation and communication control with a personal computer (PC) (not shown) are performed.

  On the other hand, the RFID tag 1 includes an antenna 11, a power generation circuit 10, an ASK demodulation circuit 19, an S / P converter 3, a load modulation circuit 2, a P / S converter 4, and a controller 5.

  Here, the configuration and control of the controller 5 in the RFID tag 1 will be described with reference to FIG.

  FIG. 2 is a block diagram showing the configuration of the controller 5 in the RFID tag 1. As shown in FIG. 2, the controller 5 includes a CPU 201, a ROM 202 storing a program for controlling transmission / reception of data with the interrogator 18, a RAM 203 used as a work area, and a flash for recording information (FLASH). It comprises a peripheral circuit 205 including a ROM 204, an I / F circuit, etc., and performs data transmission / reception control with the interrogator 18 in accordance with a program stored in the ROM 202.

  FIG. 3 is a diagram showing a memory area of the flash ROM 204 in the controller 5. As shown in FIG. 3, the memory area of the flash ROM 204 is divided into a security level 0 area 301 and a security level 1 area 302. This security level 0 area 301 is an area for recording information that anyone can read, and the security level 1 area 302 is information that the owner does not want to read the recorded contents. Is an area for recording.

  Hereinafter, a communication function between the interrogator 18 and the RFID tag 1 will be described. First, a method for transmitting data from the interrogator 18 to the RFID tag 1 will be described.

  In the interrogator 18, the controller 12 outputs data and commands that the controller 12 wants to transmit to the RFID tag 1 to the P / S converter 13, the P / S converter 13 converts the data and commands into serial data, and the ASK modulation circuit 14 The carrier wave is modulated based on the serial data, and the modulated carrier wave (modulated wave) 20 is transmitted from the RFID tag 1 via the antenna 17.

  On the other hand, in the RFID tag 1, the antenna 11 receives the modulated wave 20 transmitted from the interrogator 18, the modulated wave 20 received by the power generation circuit 10 is rectified by a rectifier circuit, smoothed by a smoothing capacitor, and smoothed. The shunt regulator circuit is controlled so that the voltage does not exceed a predetermined value, and power is supplied to each element in the RFID tag 1. Then, after the ASK demodulating circuit 19 rectifies the modulated wave 20, the data carried on the modulated wave 20 is extracted by a known ASK demodulation method, and the S / P converter 3 converts it into parallel data and outputs it to the controller 5. To do. As a result, the controller 5 performs processing such as rewriting data in the flash ROM 204 in accordance with data and commands transmitted from the interrogator 18 and transmitting data stored in the flash ROM 204 to the interrogator 18.

  For example, when writing information that the third party does not want to read into the flash ROM 204 of the RFID tag 1, the interrogator 18 sends a command and data (information that does not want to be read) instructing the writing to the security level 1 area 302. .

  Next, a method for transmitting data from the RFID tag 1 to the interrogator 18 will be described. When a data transfer command is issued from the interrogator 18 to the controller 5 of the RFID tag 1 by the data and command described above, the controller 5 outputs the data to be transferred to the P / S converter 4, and the P / S converter 4 Is converted into serial data, and the load modulation circuit 2 places the data on the carrier 21 generated from the interrogator 18 and transmits the data to the interrogator 18 via the antennas 11 and 22.

  Here, the configuration and operation of the load modulation circuit 2 will be described. The load modulation circuit 2 includes an attenuation load 7 for attenuating the signal amplitude of the carrier 21 generated from the interrogator 18, a modulation load 9 for modulating the carrier 21, and switches 6 and 8. When the controller 5 turns on the switch 6 by the control signal 24, the amplitude of the carrier 21 transmitted to the interrogator 18 is attenuated. Further, the data is put on the carrier 21 by turning on / off the switch 8 based on the data converted into the serial data by the P / S converter 4.

  On the other hand, the interrogator 18 receives the carrier 21 transmitted with data from the RFID tag 1 by the antenna 22, the load demodulation circuit 16 extracts the data, and the serial data is converted into parallel data by the S / P converter 15. The data is converted and transmitted to the controller 12.

  Next, a method in which the interrogator 18 extracts the serial data 25 from the carrier 21 transmitted from the RFID tag 1 will be described with reference to FIGS.

  FIG. 4 is a diagram showing a carrier transmitted from the RFID tag 1 to the interrogator 18. First, a method for placing data on the carrier 21 will be described with reference to FIG. FIG. 5 is an enlarged view of a circled portion 401 shown in FIG.

  In the RFID tag 1, as shown in FIG. 5, the switch 8 of the load modulation circuit 2 is turned OFF when the serial data 23 converted by the P / S converter 4 is “0”, and the serial data 23 is “1”. It becomes ON at. As a result, the load modulation circuit 2 can generate a modulated carrier 21 having a large amplitude when the serial data 23 is “0” and a small amplitude when the serial data 23 is “1”. In the interrogator 18, the carrier 21 received by the antenna 22 is output to the load demodulation circuit 16.

  FIG. 6 is a block diagram illustrating an example of the configuration of the load demodulation circuit 16. The carrier 21 input to the load demodulation circuit 16 is sent to the envelope generation circuit 601. Here, based on the carrier 21, the envelope generation circuit 601 generates an envelope 501 as shown in FIG. Then, the binarization circuit 602 binarizes the carrier 21 by comparing the envelope 501 with the threshold value 502 at the timing of the rising edge of the CLK 503 generated in synchronization with the carrier 21, and the subcarrier 504 (see FIG. 4). 402) is output. Next, the data generation circuit 603 takes out the inverted data every time the phase of the subcarrier 504 is inverted as serial data 25 (403 shown in FIG. 3) to be output to the S / P converter 15.

  Next, a method for variably controlling the transmission signal strength to the interrogator 18 according to the security level of information recorded in the flash ROM 204 of the RFID 1 will be described.

  In the RFID tag 1, when receiving a transmission command for information recorded in the flash ROM 204 from the interrogator 18, the controller 5 receives the transmission command for information recorded in the security level 0 area 301 of the flash ROM 204, or for security. It is determined whether the information is recorded in the level 1 area 302. Here, when the information of the security level 0 area 301 is transmitted, the control signal 24 turns off the switch 6 of the load modulation circuit 2 to transmit the information with a strong transmission signal strength. When transmitting the information in the area 302, the switch 6 is turned on by the control signal 24 to transmit the information with a low transmission signal strength.

  With this control method, the information in the security level 0 area 301 can be read simply by bringing the interrogator 18 close to the RFID tag 1, but the information in the security level 1 area 302 is closely attached to the RFID tag 1. Otherwise, it will not be readable.

  FIG. 7 is a diagram illustrating a state in which the output signal of the envelope circuit 601 is binarized by the binarization circuit 602 of the load demodulation circuit 16 of the interrogator 18 when the interrogator 18 is close to the RFID 1. Incidentally, reference numeral 702 corresponds to the threshold level 502 for binarization shown in FIG.

  (A) shown in FIG. 7 is a diagram illustrating an example of binarizing information in the security level 0 area 301 transmitted in a state where the transmission signal strength is strong, and the envelope 701 of the envelope circuit 601 is a threshold value. Since the level 702 is exceeded, the binarization circuit 602 can binarize this information, and as a result, the data generation circuit 603 can extract the data.

  FIG. 7B is a diagram illustrating an example of binarization of information in the security level 1 region 302 transmitted in a state where the transmission signal strength is weak. The envelope 703 of the envelope circuit 601 is a threshold value. Since the level is 702 or lower, the binarization circuit 602 cannot binarize this information, and as a result, the data generation circuit 603 cannot extract data.

  FIG. 8 is a diagram illustrating a state in which the output signal of the envelope circuit 601 is binarized by the binarization circuit 602 of the load demodulation circuit 16 of the interrogator 18 when the interrogator 18 is closely attached to the RFID 1. Reference numeral 802 corresponds to the threshold level 502 for binarization shown in FIG.

  (A) shown in FIG. 8 is a diagram illustrating an example of binarizing information in the security level 0 area 301 transmitted in a state where the transmission signal strength is strong. The envelope 801 of the envelope circuit 601 is a threshold value. Since the level 802 is exceeded, the binarization circuit 602 can binarize this information, and as a result, the data generation circuit 603 can extract the data.

  FIG. 8B is a diagram illustrating an example of binarizing information in the security level 1 region 302 transmitted in a state where the transmission signal strength is weak. The envelope 803 of the envelope circuit 601 is a threshold value. Since the level 802 is exceeded, the binarization circuit 602 can binarize this information, and as a result, the data generation circuit 603 can extract the data.

  As shown in FIGS. 7 and 8, the information in the security level 0 area 301 can be read regardless of whether the interrogator 18 is close to or close to the RFID tag 1, but the information in the security level 1 area 302 is If the interrogator 18 is not in close contact with the RFID tag 1, information cannot be read accurately. As described above, information that the third party does not want to read is recorded in the security level 1 area 302 of the RFID tag 1 so that the interrogator 18 cannot be read unless the interrogator 18 is in close contact with the RFID tag 1. Become.

  Next, a method for changing the signal transmission level to the interrogator 18 in accordance with the security level of information recorded in the RFID tag 1 will be described taking an example in which the RFID tag is attached to clothes.

  FIG. 9 is a diagram showing information recorded in the memory area of the flash ROM 204 in the RFID tag 1. When the clothes are shipped from the factory, as shown in FIG. 9, the size, color, material, manufacturing area, washing method, serial No. Various information such as price, manufacturer, etc. is recorded in the security level 0 area 301 of the flash ROM 204, and anyone can read it freely by bringing the interrogator 18 close to it. Can be used.

  Here, when the consumer purchases the clothes, the dealer attaches the interrogator 18 connected to the POS terminal 1001 as shown in FIG. 10 to the clothes to be purchased by the consumer. The information recorded in the memory area of the RFID tag 1 is read to collect sales data and the like.

  Next, among various information recorded on the RFID tag 1, information that the consumer does not want to be disclosed to the third party is moved to the security level 1 area 302 via the POS terminal 1001 and the interrogator 18. Specifically, for example, a display screen as shown in FIG. 11 may be displayed on the display device of the POS terminal 1001 to allow the consumer to change the security level.

  In addition, when changing or specifying the security level of information recorded in the RFID tag 1, the security level of information may be changed or specified only when authenticated by an authentication unit (user ID and password). Is possible.

  FIG. 11 is a diagram showing a display screen of the POS terminal 1001 when changing the security level of information. The consumer checks the information recorded on the RFID tag 1 attached to the clothes from the operation unit of the POS terminal 1001 (not shown), changes the security level according to preference for each item (information), and the RFID tag 1 In the flash ROM 204. At this time, by registering a personal identification number or the like, it is possible to prevent a third party from changing the contents and security level of information written in the flash ROM 204 without permission. Furthermore, the consumer can record his / her name in the flash ROM 204.

  FIG. 12 is a diagram showing the contents of the flash ROM 204 of the RFID tag 1 changed at the time of purchase. When the security level is changed on the screen shown in FIG. 11, the security level 0 area 301 includes a color, a material, a manufacturing area, a washing method, and a serial number. In the security level 1 area 302, the size, list price, manufacturer, and owner name are recorded.

  In this way, by recording privacy information in the security level 1 area 302, the consumer can prevent a third party from reading privacy-related information without permission when walking in the city with clothes. Can do.

  Further, after returning home, the consumer can bring all the information recorded in the RFID tag 1 into the PC by bringing the interrogator 18 connected to the personally owned PC into close contact with the RFID tag 1 attached to the clothes. Yes, it can be easily reflected in the household account book and the management data of the clothes that you own.

  In addition, after purchase, the washing method, serial no. Is recorded in the security level 0 area 301, so that when a consumer puts out clothes for cleaning, the cleaning company can take out various information about clothes simply by bringing the interrogator 18 close to the RFID tag attached to the clothes. It is possible to simplify the voucher creation work. In addition, when the clothes are subjected to a cleaning process, the clothes cleaning method can be automatically read just by bringing the interrogator 18 close to the RFID tag attached to the clothes, so that the efficiency of the cleaning work can be improved. .

  Next, taking a case where the RFID tag 1 is attached to a book as an example, a specific example in which the signal transmission level to the interrogator 18 is changed according to the security level of information recorded in the RFID tag 1 will be described.

  FIG. 13 is a diagram showing information recorded in the memory area of the flash ROM 204 in the RFID tag 1. In the state where the book is shipped from the printing factory, as shown in FIG. 13, the title, author name, publication place, issue date, edition, printer, classification, ISBN (International Standard Book Code), bibliographic number, list price, sales Various information such as a store (in this example, the store name is not recorded), a sales date (in this example, no sales date is recorded), and the like are recorded in the security level 0 area 301 of the flash ROM 204. It is possible to read information freely by approaching, and can be used for inventory, etc. during distribution.

  Here, when the consumer purchases the book, the dealer attaches the interrogator 18 connected to the POS terminal 1001 as shown in FIG. 10 to the book purchased by the consumer. The information recorded in the memory area of the RFID tag 1 is read to collect sales data and the like.

  Next, among various information recorded on the RFID tag 1, information that the consumer does not want to be disclosed to the third party is moved to the security level 1 area 302 via the POS terminal 1001 and the interrogator 18. In this example, as shown in FIG. 14, the consumer changes all information other than the sales date to the security level 1 area 302 in order to protect privacy, and further adds information on the sales bookstore.

  In this way, by recording the sales date in the security level 0 area 301, when the consumer visits another bookstore with a purchased book and passes through the shoplifting prevention gate at the entrance of the bookstore, It is possible to automatically prove that the book you bring is the property of the consumer and avoid unnecessary suspicions.

  Further, after returning home, the consumer can bring all the information recorded in the RFID tag 1 into the PC by bringing the interrogator 18 connected to the personally owned PC into close contact with the RFID tag 1 attached to the book. Yes, it can be easily reflected in the household account book and the management data of the books you own.

  In addition, when selling a book owned by a consumer to a secondhand seller of a book, the secondhand seller attaches an interrogator to the book and reads the information recorded on the RFID tag 1 to read the book. You can check the information on the store where the item was sold and the date of sale, so it can be confirmed that the book was not illegally obtained such as shoplifting. For this reason, it is possible to prevent a crime in which a book is obtained by fraudulent means such as shoplifting and sold to a second-hand dealer to be converted into cash.

  In the above-described embodiment, the method for defining the security level of information based on the memory area of the flash ROM 204 for recording information has been described. However, the memory area of the flash ROM 204 is not divided for each security level of information. When the information indicating the security level is added to each information, recorded in the flash ROM 204, and the information is transmitted from the RFID tag 1 to the interrogator 18, the interrogator 18 is added according to the security level information added to the information. It is also possible to variably control the signal intensity at the time of transmission to the network.

  Further, the case where the security level of information is defined in two stages has been described. However, when the security level of information is defined in multiple stages and information is transmitted from the RFID tag 1 to the interrogator 18 according to the defined security level. The signal intensity may be changed in multiple stages.

  Even if the present invention is applied to a system composed of a plurality of devices (for example, a host computer, an interface device, a reader, a printer, etc.), it is applied to an apparatus (for example, a copier, a facsimile machine, etc.) composed of a single device. It may be applied.

  Another object of the present invention is to supply a recording medium in which a program code of software realizing the functions of the above-described embodiments is recorded to a system or apparatus, and the computer (CPU or MPU) of the system or apparatus stores the recording medium in the recording medium. Needless to say, this can also be achieved by reading and executing the programmed program code.

  In this case, the program code itself read from the recording medium realizes the functions of the above-described embodiment, and the recording medium storing the program code constitutes the present invention.

  As a recording medium for supplying the program code, for example, a floppy (registered trademark) disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a CD-R, a magnetic tape, a nonvolatile memory card, a ROM, or the like is used. be able to.

  Further, by executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also an OS (operating system) operating on the computer based on the instruction of the program code. It goes without saying that a case where the function of the above-described embodiment is realized by performing part or all of the actual processing and the processing is included.

  Further, after the program code read from the recording medium is written in a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, the function expansion is performed based on the instruction of the program code. It goes without saying that the CPU or the like provided in the board or the function expansion unit performs part or all of the actual processing and the functions of the above-described embodiments are realized by the processing.

It is a block diagram which shows the structure of the reader / writer and RFID tag in this embodiment. 2 is a block diagram showing a configuration of a controller 5 in the RFID tag 1. FIG. 4 is a diagram showing a memory area of a flash ROM 204 in the controller 5. FIG. It is a figure showing the carrier transmitted to the interrogator 18 from the RFID tag 1. It is the figure which expanded the part 401 enclosed by the circle shown in FIG. 3 is a block diagram illustrating an example of a configuration of a load demodulation circuit 16. FIG. When the interrogator 18 is close to the RFID 1, the binarization circuit 602 of the load demodulation circuit 16 of the interrogator 18 shows a state in which the output signal of the envelope circuit 601 is binarized. When the interrogator 18 is in close contact with the RFID 1, it is a diagram showing a state in which the output signal of the envelope circuit 601 is binarized by the binarization circuit 602 of the load demodulation circuit 16 of the interrogator 18. FIG. FIG. 4 is a diagram showing information recorded in a memory area of a flash ROM 204 in the RFID tag 1. It is a figure which shows the connection state of the POS terminal 1001 and the interrogator 18. FIG. It is a figure which shows the display screen of the POS terminal 1001 at the time of changing the security level of information. It is a figure which shows the content of flash ROM204 of the RFID tag 1 changed at the time of purchase. FIG. 4 is a diagram showing information recorded in a memory area of a flash ROM 204 in the RFID tag 1. It is a figure which shows the content of flash ROM204 of the RFID tag 1 changed at the time of purchase.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 RFID tag 2 Load modulation circuit 3 S / P converter 4 P / S converter 5 Controller 6 Switch 7 Attenuation load 8 Switch 9 Modulation load 10 Power supply generation circuit 11 Antenna 12 Controller 13 P / S converter 14 ASK modulation circuit 15 S / P converter 16 Load demodulation circuit 17 Antenna 18 Interrogator 19 ASK demodulation circuit 20 Modulated wave 21 Carrier 22 Antenna 41 Envelope 42 Threshold value 43 CLK
44 Subcarrier 201 CPU
202 ROM
203 RAM
204 Flash ROM
205 Peripheral circuit 301 Security level 0 area 302 Security level 1 area 601 Envelope circuit 602 Binary circuit 603 Data generation circuit 1001 POS terminal

Claims (9)

An RF tag,
A recording means for recording information according to the security level;
An RF tag comprising: control means for variably controlling the signal intensity when transmitting the information to the interrogator according to the security level of the information. The RF tag according to claim 1, wherein the recording unit records information according to a security level based on an instruction from an interrogator.   The RF tag according to claim 1, wherein when the security level of information recorded on the RF tag is defined, the security level of information can be defined only when authenticated by an authentication unit.   The RF tag according to claim 1, wherein the recording unit has at least two recording areas, and records the information in a recording area corresponding to the security level.   2. The RF tag according to claim 1, wherein the recording unit further adds and records information defining the security level. A communication system for transmitting and receiving information between an interrogator and an RF tag,
The interrogator has a defining means for defining a security level of information to be recorded in the RF tag,
The RF tag records information received from the interrogator according to the security level defined by the interrogator, and transmits the information to the interrogator according to the security level of the recorded information. And a control means for variably controlling the signal intensity at the time of performing. An RF tag control method comprising:
A recording process for recording information received from the interrogator;
And a control step of variably controlling a signal intensity when transmitting the information to the interrogator according to a security level of the recorded information.   The program for making a computer perform the control method of RF tag of Claim 7.   A computer-readable recording medium on which the program according to claim 8 is recorded.

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