JP2007267073A - Radio communications system, and radio device used for the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radio communication system which can suppress the eavesdropping of a secret key. <P>SOLUTION: While the directivity of an array antenna 20 is switched to the directivity of n pieces, n pieces of electric waves are transmitted and received between radio devices 10 and 30. Further, the radio device 10 detects the n pieces of first electric wave intensity corresponding to the first n pieces of electric waves received from the radio device 30. By carrying out a predetermined operation to the first detected electric wave intensity of n pieces, a secret key Ks1 composed of a bit stream is created on the basis of the first permutated electric wave intensity of n pieces which are performed by the predetermined operation. Further, the radio device 30 detects the n pieces of second electric wave intensity corresponding to the second n pieces of electric waves received from the radio device 10. By carrying out a predetermined operation to the second detected electric wave intensity of n pieces, a secret key Ks2 composed of the same bit stream with that of the first secret key Ks1 is created on the basis of the second permutated electric wave intensity of n pieces which are performed by the predetermined operation. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a wireless communication system and a wireless device used therefor, and more particularly to a wireless communication system that wirelessly communicates encrypted information and a wireless device used therefor.

  Recently, with the development of the information society, information communication has become increasingly important, and wiretapping or unauthorized use of information has become a more serious problem. In order to prevent such eavesdropping of information, information has been conventionally encrypted and transmitted.

  There are public key cryptosystem and secret key cryptosystem as systems for encrypting information and communicating between terminal apparatuses. Public key cryptography is highly secure but is not suitable for encrypting large volumes of data.

  On the other hand, the secret key cryptosystem is relatively easy to process and allows high-speed encryption of a large amount of data, but it is necessary to transmit the secret key to the other party of communication. Also, in the secret key cryptosystem, if the same secret key is continuously used, it is easy to be subjected to a cryptanalysis attack and the safety may be impaired.

  Therefore, as a method of sharing a secret key without transmitting the secret key to the other party, a method of measuring the characteristics of the transmission path between the two terminal devices and generating the secret key at each terminal device based on the measured characteristics Has been proposed (Non-Patent Document 1).

  In this method, each terminal device measures a delay profile when data is transmitted and received between two terminal devices, converts the measured delay profile from an analog signal to a digital signal, and generates a secret key at each terminal device. Is the method. In other words, since the radio wave propagating in the transmission path is reversible, the delay profile when data is transmitted from one terminal device to the other terminal device transmits the same data from the other terminal device to one terminal device. It becomes the same as the delay profile. Therefore, the secret key generated based on the delay profile measured by one terminal device is the same as the secret key created based on the delay profile measured by the other terminal device.

As described above, the method of generating the secret key using the transmission path characteristics can share the same secret key only by transmitting and receiving the same data between the two terminal devices.
Motoki Horiike, Shuichi Sasaoka, “Secret Key Sharing Method Based on Irregular Fluctuations in Land Mobile Communication Channels”, IEICE Technical Report, The Institute of Electronics, Information and Communication Engineers, October 2002, TECHNICAL REPORT OF IEICE RCS2002-173, p. . 7-12.

  However, if an eavesdropper intercepts a plurality of radio waves transmitted between two terminals in the vicinity of each terminal and measures an intensity profile, the eavesdropper acquires an intensity profile close to the intensity profile measured at each terminal. be able to. As a result, the secret key may be decrypted.

  Therefore, the present invention has been made to solve such a problem, and an object of the present invention is to provide a wireless communication system capable of suppressing the eavesdropping of the secret key by improving the randomness of the secret key. is there.

  Another object of the present invention is to provide a radio apparatus used in a radio communication system capable of suppressing the eavesdropping of a secret key by improving the randomness of the secret key.

  According to the present invention, the wireless communication system includes first and second antennas and first and second wireless devices. The first and second wireless devices transmit and receive radio waves to and from each other through the wireless transmission path via the first and second antennas. Then, the first radio apparatus detects n first radio wave intensities corresponding to n (n is an integer of 2 or more) first radio waves transmitted by the second radio apparatus, and the detection is performed. From the first bit string in which the n first radio wave intensities are multi-valued or the second bit string in which a predetermined process is applied to the n first radio wave intensities to suppress the continuous arrangement of the same bit values. A first secret key is generated. The second radio apparatus detects n second radio field intensities corresponding to the n second radio waves transmitted by the first radio apparatus, and the detected n second radio field intensities are detected. Is subjected to a predetermined process on the second bit string or the n second radio wave intensities, and a second secret key composed of the same bit string as the first secret key is generated.

  Preferably, the first antenna is an antenna whose directivity can be electrically switched. The n first radio wave intensities are the n radio waves received by the first wireless device from the second wireless device when the directivity of the first antenna is changed to n directivities according to a predetermined pattern. N radio field intensities corresponding to the first radio wave. The n second radio wave intensities are the n second radio waves received from the first radio device by the second radio device when the directivity of the first antenna is changed to n directivities. N radio wave intensities corresponding to.

  Preferably, the first and second radio apparatuses generate predetermined first and second secret keys by performing predetermined arithmetic processing on the n first and second radio field intensities, respectively.

  Preferably, the first wireless device has an i-th first radio wave intensity and an i + α (α is a positive integer) -th first wave array in an array of n first radio wave intensities. The radio field strength is selected from the n first radio field strengths, and the difference between the selected i-th and i + α-th first radio field strengths is calculated to generate n third radio field strengths. A first secret key is generated based on the n third radio field intensities. The second radio apparatus arbitrarily selects the i-th and i + α-th second radio field intensities of the n second radio field intensities from the n second radio field intensities, and selects the selected i-th and i + α-th units. The difference between the second radio field intensities is calculated to generate n fourth radio field intensities, and the second secret key is generated based on the generated n fourth radio field intensities.

  Preferably, the first radio apparatus includes an n number of first radio wave intensities arranged in a ring shape with the i th first radio wave intensity and the i + 1 th first radio wave intensity in the n first radio wave intensity arrays. 1 is selected, and the i-th first radio field intensity is subtracted from the i + 1-th first radio field intensity to generate n third radio field intensities. Then, a first secret key is generated based on the n third radio wave intensities. The second radio apparatus includes n second radio waves in which the i-th first radio wave intensity and the i + 1-th first radio wave intensity in the n second radio wave intensity array are arranged in a ring shape. Select from the intensities, and subtract the i-th first radio field intensity from the (i + 1) -th first radio field intensity to generate n fourth radio field intensities. Then, a second secret key is generated based on the n fourth radio wave intensities.

  Preferably, the first radio apparatus subtracts the i-th first radio field intensity from the i + 1-th first radio field intensity, calculates an absolute value of the subtraction result, and obtains n third radio field intensities. Generate. Then, a first secret key is generated based on the n third radio wave intensities. The second radio apparatus subtracts the i-th first radio field intensity from the (i + 1) -th first radio field intensity and calculates an absolute value of the subtraction result to generate n fourth radio field intensity. Then, a second secret key is generated based on the n fourth radio wave intensities.

  Preferably, the first radio apparatus converts the i (i is a positive odd number) first radio wave intensity and the (i + 1) th first radio wave intensity into n pieces of the n first radio wave intensity arrays. Select from the first radio field intensity, calculate the difference between the selected i-th and i + 1-th first radio field intensities to generate n / 2 third radio field intensities, and generate the generated n / 2 The first secret key is generated based on the third radio field intensity. The second radio apparatus selects the i-th second radio field intensity and the i + 1-th second radio field intensity from the n second radio field intensities in the array of n second radio field intensities, The difference between the selected i-th and i + 1-th second radio field intensities is calculated to generate n / 2 fourth radio field intensities, and the second based on the generated n / 2 fourth radio field intensities. 2 secret key is generated.

  Preferably, the first radio apparatus generates n third radio field intensities by normalizing the n first radio field intensities with reference values, and an array of the generated n third radio field intensities. The i (i is 1 to n) -th third radio field intensity and i + α (α is a positive integer) -th third radio field intensity are selected from the n third radio field intensities, and the selected i The product of the i th and i + α th third radio wave intensities is calculated to generate n fourth radio wave intensities, and a first secret key is generated based on the generated n fourth radio wave intensities. . The second radio apparatus generates n fifth radio field intensities by normalizing the n second radio field intensities with reference values, and the i-th and i + α in the generated n fifth radio field intensities. The fifth fifth radio field strength is selected from the n fifth fifth radio field strengths, and the product of the selected i th and i + αth fifth radio field strengths is calculated to generate n sixth sixth radio field strengths. Then, a second secret key is generated based on the generated n sixth radio wave intensities.

  Preferably, the first radio apparatus generates n third radio field intensities by normalizing the n first radio field intensities with reference values, and an array of the generated n third radio field intensities. The i-th third radio field intensity and the i + 1-th third radio field intensity are selected from the n third radio field intensities, and the selected i-th and i + 1-th third radio field intensities are selected. N / 2 fourth radio wave intensities are generated by calculating the product of the radio wave intensities of the first and second secret radio keys based on the generated n / 2 fourth radio wave intensities. The second radio apparatus generates n fifth radio field intensities by normalizing the n second radio field intensities with a reference value, and the i th in the array of the generated n fifth radio field intensities. The fifth radio field intensity and the (i + 1) th fifth radio field intensity are selected from the n fifth radio field intensities, and the product of the selected i-th and i + 1th fifth radio field intensities is calculated. / 2 sixth radio field intensities are generated, and a second secret key is generated based on the generated n / 2 sixth radio field intensities.

  Preferably, the first radio apparatus further calculates an absolute value of the product to generate n fourth radio field strengths or n / 2 fourth radio field strengths. Then, a first secret key is generated based on the n fourth radio field strengths or the n / 2 fourth radio field strengths. The second radio apparatus further calculates an absolute value of the product to generate n sixth radio wave intensities or n / 2 sixth radio wave intensities. Then, a first secret key is generated based on the n sixth radio wave strengths or the n / 2 sixth radio wave strengths.

  Preferably, the first radio apparatus divides the n first radio field intensities into m (m is an integer of 2 or more) blocks, and sets m thresholds corresponding to the divided m blocks. Using the determined m threshold values, the first radio wave intensity included in the m blocks is multi-valued to generate a first secret key. The second radio apparatus divides the n second radio field intensities into m blocks, determines m threshold values corresponding to the divided m blocks, and sets the determined m threshold values. The second secret key is generated by converting the second radio wave intensity included in the m blocks into a multi-value.

  Preferably, the first radio apparatus generates n third radio field intensities by normalizing the n first radio field intensities with reference values, and an array of the generated n third radio field intensities. The i (i is 1 to n) -th third radio field intensity and i + α (α is a positive integer) -th third radio field intensity are selected from the n third radio field intensities, and the selected i The k-th power of the third radio field strength and the k power of the i-th third radio field strength are calculated, and the k-th power of the i-th third radio field strength and i + α are calculated. A difference of the kth power of the third radio wave strength is calculated to generate n fourth radio wave strengths, and a first secret key is generated based on the generated n fourth radio wave strengths. . The second radio apparatus generates n fifth radio field intensities by normalizing the n second radio field intensities with a reference value, and the i th in the array of the generated n fifth radio field intensities. The fifth radio field intensity and the i + αth fifth radio field intensity are selected from the n fifth radio field intensities, and the selected i-th fifth radio field intensity is raised to the k-th power and the i + αth fifth radio field intensity. Calculate the kth power of the radio field strength, calculate the difference between the calculated kth power of the i th fifth radio field strength and the kth power of the i + αth fifth radio field strength, and calculate the n sixth radio field strengths. And a second secret key is generated based on the generated n sixth radio wave intensities.

  Preferably, each of the first and second radio apparatuses includes all bits included in an arbitrary section when the same bit value continuously exists in an arbitrary section of the first and second bit strings in a range equal to or greater than a reference value. The first and second secret keys are generated by deleting the value.

  Further, according to the present invention, the wireless device is a wireless device used in a wireless communication system that performs cryptographic communication between wireless devices, wherein the first device according to any one of claims 1 to 13 is used. The wireless device is a wireless device or a second wireless device.

  In the radio communication system according to the present invention, a predetermined sequence is applied to a bit string obtained by multi-valued n radio wave intensities transmitted and received between two radio apparatuses, or n radio wave intensities are continuously arranged. A secret key composed of a bit string in which is suppressed is generated. In other words, even if a device other than the two wireless devices performs a predetermined process on the intercepted n radio wave intensities, the arithmetic processing is different from the two wireless devices, and the same secret key cannot be generated.

  Therefore, according to the present invention, wiretapping of the secret key can be suppressed.

  Embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

  FIG. 1 is a schematic diagram of a wireless communication system 100 according to an embodiment of the present invention. The wireless communication system 100 includes wireless devices 10 and 30, an antenna 11, and an array antenna 20.

  The antenna 11 is an omnidirectional antenna and is attached to the wireless device 10. The array antenna 20 is attached to the wireless device 30 and includes antenna elements 21 to 27. The antenna element 24 is a feeding element, and the antenna elements 21 to 23 and 25 to 27 are parasitic elements.

  The antenna elements 21 to 23 and 25 to 27 are arranged around the antenna element 24 in a substantially circular shape at equal intervals. When the wavelength of the radio wave transmitted and received by the array antenna 20 is λ, the distance between the antenna element 24 that is a feeding element and the antenna elements 21 to 23 and 25 to 27 that are parasitic elements is, for example, λ / 4. Set to

  The antenna elements 21 to 23 and 25 to 27 that are parasitic elements are loaded with varactor diodes (not shown) that are variable capacitance elements, and the array element is controlled by controlling the DC voltage applied to the loaded varactor diodes. The antenna 20 can perform adaptive beam forming.

  That is, the directivity of the array antenna 20 is changed by changing the DC voltage applied to the varactor diode included in the wireless device 30. Therefore, the array antenna 20 is an antenna whose directivity can be switched electrically.

  When communication is performed between the wireless device 10 and the wireless device 30, the radio wave directly propagates between the antenna 11 of the wireless device 10 and the array antenna 20 of the wireless device 30 or is affected by the intermediate 40. Propagate. As the intermediate 40, a reflector and an obstacle are assumed. When the intermediate 40 is a reflector, the radio wave emitted from the antenna 11 of the wireless device 10 or the array antenna 20 of the wireless device 30 is reflected by the intermediate 40 and is array antenna 20 of the wireless device 30 or the antenna of the wireless device 10. 11 is propagated. When the intermediate 40 is an obstacle, the radio wave emitted from the antenna 11 of the wireless device 10 or the array antenna 20 of the wireless device 30 is diffracted by the intermediate 40 and is arrayed 20 or the wireless device 10 of the wireless device 30. Is propagated to the antenna 11.

  As described above, the radio wave propagates directly between the antenna 11 of the wireless device 10 and the array antenna 20 of the wireless device 30, propagates as a reflected wave by being reflected by the intermediate 40, or is diffracted by the intermediate 40. And propagates as a diffracted wave. When the radio wave propagates from the antenna 11 of the radio device 10 to the array antenna 20 of the radio device 30 (or from the array antenna 20 of the radio device 30 to the antenna 11 of the radio device 10), the direct propagation component, the reflected wave component, and the diffraction are transmitted. Wave components are mixed, and the component of the radio wave propagated from the antenna 11 of the wireless device 10 to the array antenna 20 of the wireless device 30 (or from the array antenna 20 of the wireless device 30 to the antenna 11 of the wireless device 10) The characteristics of the transmission path between the wireless device 10 and the wireless device 30 are determined depending on whether the transmission is performed.

  In the present invention, when communication is performed between the wireless device 10 and the wireless device 30, the directivity of the array antenna 20 is changed to a plurality of directivities, and predetermined communication is performed by time division duplex (TDD) or the like. Data is transmitted and received between the wireless devices 10 and 30. Then, the radio devices 10 and 30 generate a received signal profile RSSI indicating the intensity of a plurality of radio waves when the directivity of the array antenna 20 is changed to a plurality of directivities by a method described later, and the generated received signal profile A secret key is generated by a method to be described later based on RSSI.

  When the secret key is generated in the radio devices 10 and 30, the radio devices 10 and 30 encrypt the information with the generated secret key and transmit it to the other party, and decrypt the encrypted information received from the other party with the secret key. Get information. In this case, the wiretapping device 50 intercepts wireless communication between the wireless devices 10 and 30 via the antenna 51, but cannot wiretap the secret key generated in the wireless devices 10 and 30.

  FIG. 2 is a schematic block diagram of one radio apparatus 10 shown in FIG. The radio apparatus 10 includes a signal generation unit 110, a transmission processing unit 120, an antenna unit 130, a reception processing unit 140, a profile generation unit 150, a key creation unit 160, a key matching confirmation unit 170, and a key storage unit. 180, a key matching unit 190, an encryption unit 200, and a decryption unit 210.

  The signal generation unit 110 generates a packet including predetermined data to be transmitted to the wireless device 30 when generating the secret key, and outputs the generated packet to the transmission processing unit 120.

  The transmission processing unit 120 performs transmission processing such as modulation, frequency conversion, multiple access, and amplification of a transmission signal. The antenna unit 130 includes the antenna 11 illustrated in FIG. 1, transmits a packet from the transmission processing unit 120 to the wireless device 30, receives a packet from the wireless device 30, and supplies the packet to the reception processing unit 140 or the profile generation unit 150. To do.

  The reception processing unit 140 performs reception system processing such as reception signal amplification, multiple access, frequency conversion, and demodulation. Then, the reception processing unit 140 outputs the data or signal subjected to the reception processing to the key matching confirmation unit 170, the key matching unit 190, and the decryption unit 210 as necessary.

  The profile generation unit 150 sequentially receives a plurality of radio waves from the antenna unit 130 when the directivity of the array antenna 20 is switched to a plurality of directivities, and detects the intensity of the received plurality of radio waves by a method described later. Then, the profile generation unit 150 generates a reception signal profile RSSI by performing a predetermined calculation described later on the detected plurality of radio wave intensities, and outputs the generated reception signal profile RSSI to the key generation unit 160.

  Based on the received signal profile RSSI from the profile generation unit 150, the key generation unit 160 generates a secret key Ks1 including a bit string in which consecutive arrangements of the same bit values are suppressed by a method described later. Then, the key creation unit 160 outputs the created secret key Ks1 to the key matching confirmation unit 170 and the key matching unit 190.

  The key matching confirmation unit 170 transmits / receives a packet including predetermined data to / from the wireless device 30 via the transmission processing unit 120, the antenna unit 130, and the reception processing unit 140, and the secret key Ks1 created by the key creation unit 160 is wireless. Whether or not it matches the secret key Ks2 created in the device 30 is confirmed by a method described later. Then, the key matching confirmation unit 170 stores the secret key Ks1 in the key storage unit 180 when it is confirmed that the secret key Ks1 matches the secret key Ks2. Further, when the key match confirmation unit 170 confirms that the secret key Ks1 does not match the secret key Ks2, the key match confirmation unit 170 generates a mismatch signal NMTH and outputs it to the transmission processing unit 120 and the key matching unit 190.

  The key storage unit 180 stores the secret key Ks1 from the key matching confirmation unit 170 and the key matching unit 190. The key storage unit 180 outputs the stored secret key Ks1 to the encryption unit 200 and the decryption unit 210. Note that the key storage unit 180 may store the secret key Ks1 temporarily, for example, only during communication with the wireless device 30.

  Upon receiving the mismatch signal NMTH from the key matching confirmation unit 170, the key matching unit 190 matches the secret key Ks1 with the secret key Ks2 by a method described later. Then, the key matching unit 190 confirms that the matched secret key matches the secret key Ks2 by the same method as the method in the key match confirmation unit 170. When the key matching unit 190 confirms that the secret key Ks1 matches the secret key Ks2, the key matching unit 190 stores the secret key Ks1 in the key storage unit 180.

  The encryption unit 200 encrypts the transmission data with the secret key Ks1 stored in the key storage unit 180 and outputs the encrypted data to the transmission processing unit 120. The decryption unit 210 decrypts the signal from the reception processing unit 140 with the secret key Ks1 from the key storage unit 180 to generate reception data.

  FIG. 3 is a schematic block diagram of the other radio apparatus 30 shown in FIG. The wireless device 30 is the same as the wireless device 10 except that the antenna unit 130 of the wireless device 10 described in FIG. 2 is replaced with the antenna unit 220 and a directivity setting unit 230 is added.

  The antenna unit 220 includes the array antenna 20 shown in FIG. The antenna unit 220 transmits the data from the transmission processing unit 120 to the wireless device 10 with the directivity set by the directivity setting unit 230, and the data from the wireless device 10 is set by the directivity setting unit 230. Received with directivity and output to the reception processing unit 140 or the profile generation unit 150.

  The directivity setting unit 230 sets the directivity of the antenna unit 220. In addition, when the radio devices 10 and 30 generate the secret keys Ks1 and Ks2, the directivity setting unit 230 sequentially switches the directivity of the antenna unit 220 according to a predetermined order using a method described later.

  Further, the profile generation unit 150 of the wireless device 30 sequentially receives a plurality of radio waves from the antenna unit 220 when the directivity of the array antenna 20 is switched to a plurality of directions, and a method for later describing the strength of the received plurality of radio waves. Detect by. Then, the profile generation unit 150 of the wireless device 30 performs a predetermined calculation on the detected plurality of radio wave intensities to generate a reception signal profile RSSI, and outputs the generated reception signal profile RSSI to the key generation unit 160.

  FIG. 4 is a schematic block diagram of the directivity setting unit 230 shown in FIG. Directivity setting unit 230 includes varactor diodes 231 to 236 and a control voltage generation circuit 237. The varactor diodes 231 to 236 are loaded on the antenna elements 21 to 23 and 25 to 27 shown in FIG.

  The control voltage generation circuit 237 sequentially generates control voltage sets CLV1 to CLVn (n is an integer of 2 or more), and sequentially outputs the generated control voltage sets CLV1 to CLVn to the varactor diodes 231 to 236.

  Each of the control voltage sets CLV1 to CLVn includes six voltage values V1 to V6 corresponding to the six varactor diodes 231 to 236. When the varactor diodes 231 to 236 receive the control voltage set CLV1, the varactor diodes 231 to 236 have a predetermined capacity depending on the received control voltage set CLV1. The capacity is set, and the directivity of the array antenna 20 is set to one directivity. Further, when the varactor diodes 231 to 236 receive the control voltage set CLV2, the capacity loaded on the antenna elements 21 to 23 and 25 to 27, which are parasitic elements, is determined according to the received control voltage set CLV2. The capacity is set, and the directivity of the array antenna 20 is set to another directivity. Therefore, the varactor diodes 231 to 236 sequentially change the capacity loaded in the antenna elements 21 to 23 and 25 to 27 as parasitic elements according to the control voltage sets CLV1 to CLVn, and the directivity of the array antenna 20 is set to n. Sequentially change to directivity.

  FIG. 5 is a schematic block diagram of the key matching confirmation unit 170 shown in FIGS. 2 and 3. The key matching confirmation unit 170 includes a data generation unit 171, a data comparison unit 172, and a result processing unit 173. Note that the key matching confirmation unit 170 of the wireless devices 10 and 30 has the same configuration, but in FIG. 5, in order to explain the operation of confirming that the secret key Ks1 matches the secret key Ks2, the wireless device 30 Only the data generator 171 is shown.

  Upon receiving the secret key Ks1 from the key creation unit 160, the data generation unit 171 generates key confirmation data DCFM1 for confirming that the secret key Ks1 matches the secret key Ks2, and the generated key confirmation data. DCFM1 is output to the transmission processing unit 120 and the data comparison unit 172.

  In this case, the data generation unit 171 generates key confirmation data DCFM1 from the secret key Ks1 by irreversible calculation, one-way calculation, or the like. More specifically, the data generation unit 171 generates key confirmation data DCFM1 by calculating the hash value of the secret key Ks1 or Ks2.

  The data comparison unit 172 receives the key confirmation data DCFM1 from the data generation unit 171 and receives the key confirmation data DCFM2 generated by the data generation unit 171 of the wireless device 30 from the reception processing unit 140. Then, the data comparison unit 172 compares the key confirmation data DCFM1 with the key confirmation data DCFM2. When the key confirmation data DCFM1 matches the key confirmation data DCFM2, the data comparison unit 172 generates a coincidence signal MTH and outputs it to the result processing unit 173.

  Further, the data comparison unit 172 generates a mismatch signal NMTH when the key confirmation data DCFM1 does not match the key confirmation data DCFM2. Then, the data comparison unit 172 outputs the mismatch signal NMTH to the key matching unit 190 and transmits the mismatch signal NMTH to the radio apparatus 30 via the transmission processing unit 120 and the antenna unit 130.

  Upon receiving the match signal MTH from the data comparison unit 172, the result processing unit 173 stores the secret key Ks1 received from the key creation unit 160 in the key storage unit 180.

  FIG. 6 is a schematic block diagram of the key matching unit 190 shown in FIGS. The key matching unit 190 includes a pseudo syndrome generation unit 191, a mismatch bit detection unit 192, a key mismatch correction unit 193, a data generation unit 194, a data comparison unit 195, and a result processing unit 196.

  Note that the key matching unit 190 of the wireless devices 10 and 30 has the same configuration, but in FIG. 6, in order to explain the operation of matching the secret key Ks1 with the secret key Ks2, the wireless device 30 has a pseudo syndrome. Only the creation unit 191 is shown.

When receiving the mismatch signal NMTH from the data comparison unit 172 of the key match confirmation unit 170, the pseudo syndrome creation unit 191 calculates the syndrome s1 of the secret key Ks1 received from the key creation unit 160. More specifically, pseudo syndrome creation unit 191 detects a bit pattern x1 of private key Ks1, it calculates a syndrome s1 = x1H ^T by multiplying the parity check matrix H to the bit pattern x1. Then, the pseudo-syndrome creation unit 191 outputs the bit pattern x1 to key mismatch corrector 193 outputs the calculated syndrome s1 = x1H ^T to mismatch bit detector 192.

Incidentally, these operations are operations mod2, ^{H T} is a transposed matrix of the check matrix H.

Mismatch bit detector 192 receives syndrome s1 from pseudo syndrome creation unit 191, receives the syndrome s2 = x2H ^T computed by pseudo syndrome creation unit 191 of the wireless device 30 from the reception processing unit 140. Then, the mismatch bit detection unit 192 calculates a difference s = s1−s2 between the syndrome s1 and the syndrome s2.

It should be noted that, if the difference (bit pattern of the key disagreement) of the bit pattern of the secret key Ks1, Ks2 and e = x1-x2, the relationship of s = eH ^T is established. When s = 0, e = 0 and the bit pattern of the secret key Ks1 matches the bit pattern of the secret key Ks2.

When the calculated difference s is not 0 (that is, when e ≠ 0), the mismatch bit detection unit 192 derives the key mismatch bit pattern e from s = eH ^T and corrects the derived bit pattern e to the key mismatch correction. To the unit 193.

  The key mismatch correction unit 193 receives the bit pattern x1 from the pseudo syndrome generation unit 191 and receives the key mismatch bit pattern e from the mismatch bit detection unit 192. Then, the key mismatch correction unit 193 calculates the bit pattern x2 = x1-e of the other party's secret key by subtracting the bit pattern e that does not match the key pattern from the bit pattern x1.

  As described above, the key matching unit 190 regards the mismatch between the secret keys Ks1 and Ks2 as an error, and resolves the mismatch between the secret keys Ks1 and Ks2 by applying error correction.

  This method of matching secret keys may cause key matching to fail if the number of bits that do not match the key is greater than the error correction capability, so check the key matching after performing key matching. Need to do.

  When the data generation unit 194 receives the matched bit pattern (key) x2 = x1-e from the key mismatch correction unit 193, the data generation unit 194 generates key confirmation data DCFM3 based on the bit pattern (key) x2, and the generation thereof The key confirmation data DCFM3 thus made is output to the data comparison unit 195. Further, the data generation unit 194 transmits the generated key confirmation data DCFM3 to the wireless device 30 via the transmission processing unit 120 and the antenna unit 130.

  The data generation unit 194 generates key confirmation data DCFM3 by the same method as the generation method of the key confirmation data DCFM1 by the data generation unit 171 of the key matching confirmation unit 170.

  The data comparison unit 195 receives the key confirmation data DCFM3 from the data generation unit 194 and receives the key confirmation data DCFM4 generated by the wireless device 30 from the reception processing unit 140. Then, the data comparison unit 195 compares the key confirmation data DCFM3 with the key confirmation data DCFM4.

  When the key confirmation data DCFM3 matches the key confirmation data DCFM4, the data comparison unit 195 generates a coincidence signal MTH and outputs it to the result processing unit 196.

  Further, the data comparison unit 195 generates a mismatch signal NMTH when the key confirmation data DCFM3 does not match the key confirmation data DCFM4. Then, the data comparison unit 195 transmits the mismatch signal NMTH to the radio apparatus 30 via the transmission processing unit 120 and the antenna unit 130.

  When the result processing unit 196 receives the match signal MTH from the data comparison unit 195, the result processing unit 196 stores the bit pattern (key) x2 = x1-e received from the key mismatch correction unit 193 in the key storage unit 180.

  As described above, the data generation unit 194, the data comparison unit 195, and the result processing unit 196 confirm the coincidence of the keys that have been matched by the same method as the confirmation method in the key matching confirmation unit 170.

  FIG. 7 is a conceptual diagram of received signal strength. The control voltage generation circuit 237 of the directivity setting unit 230 sequentially generates control voltage sets CLV1 to CLVn each consisting of voltages V1 to V6 and outputs them to the varactor diodes 231 to 236. In this case, the voltages V1 to V6 are voltages for changing the capacity loaded on the antenna elements 21 to 23 and 25 to 27, respectively, and are, for example, DC voltages in the range of -20 to 0V. The control voltage generation circuit 237 determines each control voltage set CLV1 to CLVn by changing the voltage value of each of the voltages V1 to V6 according to 8-bit data, and the determined control voltage sets CLV1 to CLVn are varactors. Output to the diodes 231 to 236.

  The varactor diodes 231 to 236 set the directivity of the array antenna 20 to one directivity according to the control voltage set CLV1 including the voltages [V11, V12, V13, V14, V15, V16]. The varactor diodes 231 to 236 set the directivity of the array antenna 20 to another directivity according to the control voltage set CLV2 including the voltages [V21, V22, V23, V24, V25, V26]. Hereinafter, similarly, the varactor diodes 231 to 236 have control voltage sets CLV3 to CV3 each including voltages [V31, V32, V33, V34, V35, V36] to [Vn1, Vn2, Vn3, Vn4, Vn5, Vn6], respectively. The directivity of the array antenna 20 is sequentially switched according to CLVn.

  Thus, the varactor diodes 231 to 236 sequentially switch the directivity of the array antenna 20 to n directivities according to the control voltage sets CLV1 to CLVn. In this case, the control voltage generation circuit 237 sequentially outputs the control voltage sets CLV1 to CLVn to the varactor diodes 231 to 236 so that the directivity of the array antenna 20 is switched for each packet PKTn. The directivity of the array antenna 20 is switched for each packet PKTn.

  The array antenna 20 transmits one packet in each directivity while sequentially switching the directivity to n directivities.

  As a result, the profile generation unit 150 of the wireless device 10 receives n radio waves from the antenna unit 130 when the directivity of the array antenna 20 is switched to n directivities.

  And the profile production | generation part 150 of the radio | wireless apparatus 10 detects n radio field intensity WI1-WIN corresponding to n radio waves when the directivity of the array antenna 20 is switched to n directivity, A predetermined calculation is performed on the detected n radio wave intensities WI1 to WIn.

  Hereinafter, a method for creating a secret key will be described. When generating the secret keys Ks1 and Ks2, respectively, the wireless devices 10 and 30 transmit and receive 384 packets PKT1 to PKT384, for example.

  And the profile production | generation part 150 of the radio | wireless apparatuses 10 and 30 receives n (= 384) electromagnetic waves from the antenna parts 130 and 220, respectively, n (= 384) corresponding to the received n (= 384) radio waves. 384) The radio wave intensities WI1 to WIn are detected. Thereafter, the profile generation unit 150 of the radio apparatuses 10 and 30 generates a reception signal profile RSSI_org in which n (= 384) radio wave intensities WI1 to WIn are sequentially arranged, and n (= 384) constituting the reception signal profile RSSI_org. The received signal profile RSSI_pro composed of n (= 384) radio wave intensities WI1 ′ to WIn ′ is generated by performing a predetermined calculation described below on the radio wave intensities WI1 to WIn. Then, the profile generation unit 150 of the wireless devices 10 and 30 outputs the generated reception signal profile RSSI_pro to the key generation unit 160.

  The key creation unit 160 of the wireless devices 10 and 30 receives the received signal profile RSSI_pro from the profile generation unit 150, and uses the received signal profile RSSI_pro to receive the secret keys Ks1 and Ks2 by the method described below, respectively. Generate.

[Secret key creation method 1]
FIG. 8 is a diagram illustrating a first example of a secret key creation method. In addition, each numerical value shown to (a)-(c) of FIG. 8 shows the received signal strength of an electromagnetic wave, and a unit is dBm. The received signal profile RSSI_org is an array of n (= 384) radio wave intensities WI1 to WIn received from the antenna units 130 and 220 [2, 4, 4, 5, -7, 0, 6, 4, 4, −4, 6, 6, 6, 2,..., 2] (see FIG. 8A).

  The profile generation unit 150 of the radio apparatuses 10 and 30 generates a reception signal profile RSSI_org, calculates a difference between two consecutive radio wave intensities in the array of the generated reception signal profile RSSI_org, and receives the reception signal profile RSSI_pro1 (reception signal profile). One type of RSSI_pro) is generated.

  More specifically, the profile generation unit 150 of the wireless devices 10 and 30 selects the first radio wave intensity = [2] and the second radio wave intensity = [4] of the received signal profile RSSI_org, The first radio wave intensity = [2] is subtracted from the selected second radio wave intensity = [4] to generate the first radio wave intensity = [2] of the reception signal profile RSSI_pro1.

  Next, the profile generation unit 150 of the wireless devices 10 and 30 selects the second radio wave intensity = [4] and the third radio wave intensity = [4] of the received signal profile RSSI_org, and the selected second radio wave intensity = [4]. The second radio wave intensity = [4] is subtracted from the third radio wave intensity = [4] to generate the second radio wave intensity = [0] of the reception signal profile RSSI_pro1.

  Similarly, the profile generator 150 of the wireless devices 10 and 30 selects the i-th (i is a positive integer) -th radio wave intensity WIi and the (i + 1) -th radio wave intensity WIi + 1 of the received signal profile RSSI_org, The i-th radio wave intensity WIi is subtracted from the selected i + 1-th radio wave intensity WIi + 1 to generate the i-th radio wave intensity of the reception signal profile RSSI_pro1. Then, the profile generation unit 150 of the wireless devices 10 and 30 [2, 0, 1, −12, 7, 6, −2, 0, −8, 10, 0, 0, −4,. ] Is generated (refer to (b) of FIG. 8).

  In this case, when the last radio wave intensity = [2] of the received signal profile RSSI_org is selected as the i-th radio wave intensity WIi, the first radio wave intensity = [2] of the received signal profile RSSI_org is the i + 1-th radio wave intensity WIi + 1. Selected as. Accordingly, the profile generation unit 150 of the wireless devices 10 and 30 selects the i-th radio wave intensity WIi and the i + 1-th radio wave intensity WIi + 1 from the n radio wave intensities WI1 to WIn arranged in a ring shape.

  As described above, the profile generation unit 150 of the wireless devices 10 and 30 performs a predetermined calculation for calculating the difference between two consecutive radio field intensities for the n radio field intensities WI1 to WIn received from the antenna units 130 and 220, respectively. To generate a received signal profile RSSI_pro1.

  And the profile production | generation part 150 of the radio | wireless apparatuses 10 and 30 will output the produced | generated reception signal profile RSSI_pro1 to the key preparation part 160, if reception signal profile RSSI_pro1 is produced | generated.

  Upon receiving reception signal profile RSSI_pro1 from profile generation unit 150, key generation unit 160 of radio devices 10 and 30 calculates an average value or median value of n radio wave intensities WI1 ′ to WIn ′ constituting reception signal profile RSSI_pro1. The calculated average value or median value is set as a threshold value Ith. Then, the key creation unit 160 of the wireless devices 10 and 30 deletes a predetermined number of radio field intensities close to the threshold value Ith from the n radio field intensities WI1 ′ to WIn ′, and the remaining j (j is 2 An integer satisfying ≦ j <n) is multi-valued by the threshold value Ith to generate the secret key Ks1.

  More specifically, the key creation unit 160 of the wireless devices 10 and 30 sets “1” when the radio wave strengths WI1 ′ to WIj ′ are larger than the threshold value Ith, and the radio wave strengths WI1 ′ to WIj ′ are the thresholds. If the value is smaller than the value Ith, j radio wave intensities WI1 ′ to WIj ′ are multivalued as “0”. Then, the key creation unit 160 of the wireless devices 10 and 30 sets the bit string obtained by multi-valued j radio field strengths WI1 'to WIj' as the secret key Ks1.

  That is, the key creation unit 160 of the wireless devices 10 and 30 obtains the threshold = 0 based on the received signal profile RSSI_pro1, and deletes the radio field intensity in the vicinity of the obtained threshold = 0. In this case, the key creation unit 160 of the wireless devices 10 and 30 performs the second, third, seventh, eighth, eleventh, twelfth and nth (= 384) reception signal profiles RSSI_pro1. Is deleted (see (c) of FIG. 8), and the remaining j (= 128) radio wave intensities WI1 ′ to WIj ′ are multi-valued by a threshold value = 0 to form a bit string [101010. ] Are created (see (d) of FIG. 8).

  In the above, the profile generation unit 150 of the wireless devices 10 and 30 selects the i-th radio wave intensity WIi and the i + 1-th radio wave intensity WIi + 1 from the received signal profile RSSI_org, and the i-th radio wave intensity WIi + 1 to the i-th radio wave intensity WIi + 1. However, in the present invention, the profile generation unit 150 of the radio apparatuses 10 and 30 is not limited to this, and the i th radio wave intensity WIi is generated by subtracting the radio wave intensity WIi. The radio wave intensity WIi and the i + α (α is a positive integer) -th radio wave intensity WIi + α are selected from the received signal profile RSSI_org, and the i-th radio wave intensity WIi is subtracted from the i + α-th radio wave intensity WIi + α to i of the received signal profile RSSI_pro1. To generate the second field strength Good.

  Further, the profile generation unit 150 of the wireless devices 10 and 30 may generate the i-th radio wave intensity of the received signal profile RSSI_pro1 by subtracting the i + 1-th radio wave intensity WIi + 1 from the i-th radio wave intensity WIi. The i-th radio field intensity WIi may be subtracted from the i + α-th radio field intensity WIi + α to generate the i-th radio field intensity of the received signal profile RSSI_pro1.

[Secret key creation method 2]
FIG. 9 is a diagram illustrating a second example of a secret key creation method. In addition, each numerical value shown to (a)-(d) of FIG. 9 shows the received signal strength of an electromagnetic wave, and a unit is dBm. Based on the n radio waves received from the antenna units 130 and 220, the profile generation unit 150 of the wireless devices 10 and 30, respectively, receives the received signal profile RSSI_org = [2, 4, 4, 5, -7, 0. , 6, 4, 4, -4, 6, 6, 6, 2,..., 2] are generated (see FIG. 9A).

  And the profile production | generation part 150 of the radio | wireless apparatuses 10 and 30 calculates the difference of the two continuous radio wave strengths in the arrangement | sequence of the produced | generated reception signal profile RSSI_org, and produces | generates the reception signal profile RSSI_pro1 mentioned above ((FIG. 9 ( b)).

  After that, the profile generation unit 150 of the wireless devices 10 and 30 calculates the absolute value of each of the n (= 384) radio wave intensities WI1 ′ to WI1n ′ constituting the reception signal profile RSSI_pro1 to generate the reception signal profile RSSI_pro2. (See (c) of FIG. 9). Then, the profile generation unit 150 of the wireless devices 10 and 30 outputs the generated reception signal profile RSSI_pro2 to the key generation unit 160.

  When receiving the received signal profile RSSI_pro2 from the profile generating unit 150, the key creating unit 160 of the wireless devices 10 and 30 receives an average value of n radio field strengths | WI1 ′ | to | WIN ′ | constituting the received signal profile RSSI_pro2 or The median value is calculated, and the calculated average value or median value is set as the threshold value Ith. Then, the key creation unit 160 of the wireless devices 10 and 30 deletes a predetermined number of radio field intensities close to the threshold value Ith from the n radio field intensities | WI1 ′ | to | WINIn | The secret keys Ks1 and Ks2 are generated by converting the radio wave intensity | WI1 ′ | to | WIj ′ |

  That is, the key creation unit 160 of the wireless devices 10 and 30 obtains a threshold value = 3.6 based on the received signal profile RSSI_pro2, and obtains a predetermined number of radio wave intensities close to the obtained threshold value = 3.6. delete. In this case, the key creation unit 160 of the wireless devices 10 and 30 deletes the first, seventh, and thirteenth radio wave intensities of the received signal profile RSSI_pro2 (see (d) in FIG. 9), and the remaining j The (= 128) radio wave intensities | WI1 ′ | to | WIj ′ | are multi-valued with a threshold = 3.6 to generate secret keys Ks1, Ks2 composed of a bit string [0011101100... 0] (FIG. 9 (e)).

[Secret key creation method 3]
FIG. 10 is a diagram showing a third example of a secret key creation method. In addition, each numerical value shown to (a)-(c) of FIG. 10 shows the received signal strength of an electromagnetic wave, and a unit is dBm. Based on the n radio waves received from the antenna units 130 and 220, the profile generation unit 150 of the wireless devices 10 and 30, respectively, receives the received signal profile RSSI_org = [2, 4, 4, 5, -7, 0. , 6, 4, 4, −4, 6, 6, 6, 2,..., 2] are generated (see FIG. 10A).

  Then, the profile generation unit 150 of the wireless devices 10 and 30 calculates a difference between two independent radio wave strengths in the generated array of received signal profiles RSSI_org to generate a received signal profile RSSI_pro3 ((b in FIG. 10). )reference).

  More specifically, the profile generation unit 150 of the wireless devices 10 and 30 selects the first radio wave intensity [2] and the second radio wave intensity [4] from the received signal profile RSSI_org, and the selected By subtracting the first radio wave intensity [2] from the second radio wave intensity [4], the first radio wave intensity = [2] of the reception signal profile RSSI_pro3 is generated.

  Next, the profile generation unit 150 of the wireless devices 10 and 30 selects the third radio wave intensity = [4] and the fourth radio wave intensity = [5] of the received signal profile RSSI_org, and the selected second radio wave intensity = [5]. The third radio wave intensity = [4] is subtracted from the fourth radio wave intensity = [5] to generate the second radio wave intensity = [1] of the reception signal profile RSSI_pro3.

  Similarly, the profile generation unit 150 of the wireless devices 10 and 30 selects the (2i-1) th radio wave intensity WI2i-1 and the 2i th radio wave intensity WI2i of the received signal profile RSSI_org, and The (2i-1) -th radio wave intensity WI2i-1 is subtracted from the selected 2i-th radio wave intensity WI2i to generate the i-th radio wave intensity of the received signal profile RSSI_pro3. And the profile production | generation part 150 of the radio | wireless apparatuses 10 and 30 produces | generates the received signal profile RSSI_pro3 which consists of [2, 1, 7, -2, -8, 0, -4 ..., 0] (FIG. 10). (See (b)).

  As described above, the profile generation unit 150 of the wireless devices 10 and 30 calculates a difference between two independent and continuous radio field strengths for the n radio field strengths WI1 to WIn received from the antenna units 130 and 220, respectively. The received signal profile RSSI_pro3 is generated by performing the above calculation.

  And the profile production | generation part 150 of the radio | wireless apparatuses 10 and 30 will output the produced | generated reception signal profile RSSI_pro3 to the key preparation part 160, if reception signal profile RSSI_pro3 is produced | generated.

  Upon receiving reception signal profile RSSI_pro3 from profile generation unit 150, key generation unit 160 of wireless devices 10 and 30 calculates an average value or median value of n radio wave intensities WI1 ′ to WIn ′ constituting reception signal profile RSSI_pro3. The calculated average value or median value is set as a threshold value Ith. Then, the key creation unit 160 of the radio apparatuses 10 and 30 deletes a predetermined number of radio field intensities near the threshold value Ith from the n radio field intensities WI1 ′ to WIn ′, and the remaining j radio field intensities WI1. The secret keys Ks1 and Ks2 are generated by multi-leveling “˜WIj” with the threshold value Ith.

  That is, the key creation unit 160 of the wireless devices 10 and 30 obtains a threshold value = 0.5 based on the received signal profile RSSI_pro3, and sets a predetermined number of radio wave intensities close to the obtained threshold value = 0.5. delete. In this case, the key creation unit 160 of the wireless devices 10 and 30 deletes the second, sixth, and nth radio wave intensities of the received signal profile RSSI_pro3 (see (c) in FIG. 10), and the remaining j The (= 128) radio wave intensities WI1 ′ to WIj ′ are multi-valued with a threshold value = 0.5 to generate secret keys Ks1, Ks2 made up of a bit string [11000...] ((D) in FIG. 10). reference).

  In the above description, it has been described that the profile generation unit 150 of the radio apparatuses 10 and 30 calculates the difference between two independent radio wave intensities to generate the reception signal profile RSSI_pro3. However, in the present invention, the reception signal profile RSSI_pro3 is generated. The i-th radio wave intensity WIi and the i + α-th radio wave intensity WIi + α of the profile RSSI_org are selected, and the i-th radio wave intensity WIi is subtracted from the selected i + α-th radio wave intensity WIi + α to obtain the i-th radio wave of the received signal profile RSSI_pro3. Intensity is generated, the i + 1-th radio field intensity WIi + 1 and i + α + 1-th radio field intensity WIi + α + 1 of the received signal profile RSSI_org are selected, and the i + 1-th radio field intensity WIi + 1 is subtracted from the selected i + α + 1-th radio field intensity WIi + α + 1. Professional The i + 1th radio wave intensity of the file RSSI_pro3 may be generated.

  In this case, when the last radio wave intensity = [2] of the received signal profile RSSI_org is selected as the i-th radio wave intensity WIi, the α-th radio wave intensity from the top of the received signal profile RSSI_org is selected as the i + α-th radio wave intensity WIi + α. Is done. Accordingly, the profile generation unit 150 of the wireless devices 10 and 30 selects the i-th radio wave intensity WIi and the i + α-th radio wave intensity WIi + α from the n radio wave intensities WI1 to WIn arranged in a ring shape.

  Further, the i-th radio field intensity of the received signal profile RSSI_pro3 may be generated by subtracting the 2i-th radio field intensity WI2i from the (2i-1) -th radio field intensity WI2i-1. The i + αth radio field intensity WIi + α may be subtracted from WIi to generate the ith radio field intensity of the received signal profile RSSI_pro3.

  Further, when the secret key generation method 3 is used, the number of radio wave strengths constituting the received signal profile RSSI_pro3 is half the number of radio wave strengths constituting the received signal profile RSSI_org, so that the 128-bit secret keys Ks1, Ks2 , The reception signal profile RRSI_org composed of 768 radio wave intensities WI1 to WIn is generated, 384 reception signal profiles RRSI_pro3 are generated from the generated reception signal profile RRSI_org, and the reception signal profile RRSI_pro3 is configured. Of the 384 radio wave intensities WI1 ′ to WIn ′, 256 radio wave intensities close to the threshold are deleted to create 128-bit secret keys Ks1 and Ks2.

[Secret key creation method 4]
FIG. 11 is a diagram illustrating a fourth example of the secret key creation method. In addition, each numerical value shown to (a)-(d) of FIG. 11 shows the received signal strength of an electromagnetic wave, and a unit is dBm. Based on the n radio waves received from the antenna units 130 and 220, the profile generation unit 150 of the wireless devices 10 and 30, respectively, receives the received signal profile RSSI_org = [2, 4, 4, 5, -7, 0. , 6, 4, 4, -4, 6, 6, 6, 2,..., 2] are generated (see FIG. 11A).

  Then, the profile generation unit 150 of the wireless devices 10 and 30 selects the median value in the array of the generated reception signal profiles RSSI_org, and the n radio field strengths WI1 to WIn constituting the reception signal profile RSSI_org based on the selected median value. Is normalized.

  More specifically, when n radio field intensities WI1 to WIn are composed of 384 radio field intensities WI1 to WI384, the profile generation unit 150 of the radio apparatuses 10 and 30 sets the 192nd radio field intensity to the median = 4. Select as. Then, the profile generation unit 150 of the radio apparatuses 10 and 30 receives the received signal profile RSSI_org = [2, 4, 4, 5, −7, 0, 6, 4, 4, −4, based on the selected median value = 4. 6, 6, 6, 2,..., 2] is normalized to generate a received signal profile RSSI_pro4 (see FIG. 11B).

  Thereafter, the profile generation unit 150 of the wireless devices 10 and 30 calculates a product of two consecutive radio wave intensities in the array of the reception signal profiles RSSI_pro4 to generate a reception signal profile RSSI_pro5.

  More specifically, the profile generation unit 150 of the wireless devices 10 and 30 selects the first radio wave intensity [−2] and the second radio wave intensity [0] from the received signal profile RSSI_pro4 and selects them. The product of the first radio wave intensity [−2] and the second radio wave intensity [0] is calculated to generate the first radio wave intensity = [0] of the received signal profile RSSI_pro5.

  Next, the profile generation unit 150 of the wireless devices 10 and 30 selects the second radio wave intensity = [0] and the third radio wave intensity = [0] of the received signal profile RSSI_pro4, and the selected first The product of the second radio wave intensity = [0] and the third radio wave intensity = [0] is calculated to generate the second radio wave intensity = [0] of the received signal profile RSSI_pro5.

  Similarly, the profile generation unit 150 of the radio apparatuses 10 and 30 selects the i-th radio wave intensity WIi and the (i + 1) -th radio wave intensity WIi + 1 of the received signal profile RSSI_pro4, and selects the selected i-th radio wave intensity WIi + 1. The product of the radio wave intensity WIi and the (i + 1) th radio wave intensity WIi + 1 is calculated to generate the i th radio wave intensity of the reception signal profile RSSI_pro5. Then, the profile generation unit 150 of the wireless devices 10 and 30 [0, 0, 0, −11, 44, −8, 0, 0, 0, −16, 4, 4, −4,. ] Is generated (see (c) of FIG. 11).

  In this case, when the last radio wave intensity = [− 2] of the received signal profile RSSI_pro4 is selected as the i-th radio wave intensity WIi, the first radio wave intensity = [− 2] of the received signal profile RSSI_pro4 is the i + 1th radio wave. Intensity WIi + 1 is selected. Accordingly, the profile generation unit 150 of the wireless devices 10 and 30 selects the i-th radio wave intensity WIi and the i + 1-th radio wave intensity WIi + 1 from the n radio wave intensities WI1 to WIn arranged in a ring shape.

  As described above, the profile generation unit 150 of the radio apparatuses 10 and 30 calculates the normalization process and the product of two consecutive radio wave intensities for the n radio wave intensities WI1 to WIn received from the antenna units 130 and 220, respectively. The received signal profile RSSI_pro5 is generated by performing a predetermined calculation.

  And the profile production | generation part 150 of the radio | wireless apparatuses 10 and 30 will output the produced | generated reception signal profile RSSI_pro5 to the key preparation part 160, if reception signal profile RSSI_pro5 is produced | generated.

  When the key generation unit 160 of the wireless devices 10 and 30 receives the received signal profile RSSI_pro5 from the profile generation unit 150, the key generation unit 160 calculates an average value or a median value of the n radio field intensities WI1 ′ to WIn ′ constituting the received signal profile RSSI_pro5. The calculated average value or median value is set as a threshold value Ith. Then, the key creation unit 160 of the radio apparatuses 10 and 30 deletes a predetermined number of radio field intensities close to the threshold value Ith from the n radio field intensities WI1 ′ to WIn ′, and the remaining j radio field intensities WI1. The secret keys Ks1 and Ks2 are generated by multi-leveling “˜WIj” with the threshold value Ith.

  That is, the key creation unit 160 of the wireless devices 10 and 30 obtains a threshold value = 1.2 based on the received signal profile RSSI_pro5, and sets a predetermined number of radio wave intensities close to the obtained threshold value = 1.2. delete. In this case, the key creation unit 160 of the wireless devices 10 and 30 deletes the first to third and seventh to ninth radio wave intensities of the received signal profile RSSI_pro5 (see FIG. 11D). ), The remaining j (= 128) radio wave intensities WI1 ′ to WIj ′ are multi-valued by a threshold value = 1.2, and secret keys Ks1 and Ks2 including a bit string [0100110... 0] are generated ( (See (e) of FIG. 11).

  In the above description, the profile generation unit 150 of the wireless devices 10 and 30 selects the i-th radio wave intensity WIi and the i + 1-th radio wave intensity WIi + 1 from the received signal profile RSSI_pro4, and the selected i-th radio wave intensity WIi. Has been described that the i-th radio wave intensity of the received signal profile RSSI_pro5 is generated by calculating the product of the i + 1-th radio wave intensity WIi + 1. However, the present invention is not limited to this, and the profile generators of the radio apparatuses 10 and 30 are not limited thereto. 150 selects the i-th radio field intensity WIi and the i + α-th radio field intensity WIi + α from the received signal profile RSSI_pro4, and calculates and receives the product of the selected i-th radio field intensity WIi and i + α-th radio field intensity WIi + α. I-th signal strength of signal profile RSSI_pro5 It may be generated.

[Secret key creation method 5]
FIG. 12 is a diagram illustrating a fifth example of a secret key creation method. In addition, each numerical value shown to (a)-(d) of FIG. 12 shows the received signal strength of an electromagnetic wave, and a unit is dBm. Based on the n radio waves received from the antenna units 130 and 220, the profile generation unit 150 of the wireless devices 10 and 30, respectively, receives the received signal profile RSSI_org = [2, 4, 4, 5, -7, 0. , 6, 4, 4, −4, 6, 6, 6, 2,..., 2] are generated (see FIG. 12A).

  Then, the profile generation unit 150 of the radio apparatuses 10 and 30 receives and normalizes the n radio field strengths WI1 to WIn constituting the generated reception signal profile RSSI_org by the method described in [Secret Key Creation Method 4]. A signal profile RSSI_pro4 is generated (see FIG. 12B).

  Thereafter, the profile generation unit 150 of the radio apparatuses 10 and 30 calculates a product of two independent continuous radio wave intensities in the array of the reception signal profiles RSSI_pro4 to generate a reception signal profile RSSI_pro6 (see FIG. 12C). ).

  More specifically, the profile generation unit 150 of the wireless devices 10 and 30 selects the first radio wave intensity [−2] and the second radio wave intensity [0] from the received signal profile RSSI_pro4 and selects them. The product of the first radio wave intensity [−2] and the second radio wave intensity [0] is calculated to generate the first radio wave intensity = [0] of the received signal profile RSSI_pro6.

  Next, the profile generation unit 150 of the wireless devices 10 and 30 selects the third radio wave intensity = [0] and the fourth radio wave intensity = [1] of the received signal profile RSSI_pro4, and the selected first The product of the third radio wave intensity = [0] and the fourth radio wave intensity = [1] is calculated to generate the second radio wave intensity = [0] of the received signal profile RSSI_pro6.

  Similarly, the profile generation unit 150 of the radio apparatuses 10 and 30 selects the (2i-1) th radio wave intensity WI2i-1 and the 2i th radio wave intensity WI2i of the received signal profile RSSI_pro4, and The product of the selected (2i-1) -th radio wave intensity WI2i-1 and the 2i-th radio wave intensity WI2i is calculated to generate the i-th radio wave intensity of the received signal profile RSSI_pro6. And the profile production | generation part 150 of the radio | wireless apparatuses 10 and 30 produces | generates the received signal profile RSSI_pro6 which consists of [0, 0, 44, 0, 0, 4, -4, ..., 4] (( c)).

  As described above, the profile generation unit 150 of the wireless devices 10 and 30 respectively performs normalization processing and product of two independent continuous radio wave intensities on the n radio wave intensities WI1 to WIn received from the antenna units 130 and 220, respectively. The received signal profile RSSI_pro6 is generated by performing a predetermined calculation for calculating.

  And the profile production | generation part 150 of the radio | wireless apparatuses 10 and 30 will output the produced | generated reception signal profile RSSI_pro6 to the key preparation part 160, if the reception signal profile RSSI_pro6 is produced | generated.

  Upon receiving reception signal profile RSSI_pro6 from profile generation unit 150, key generation unit 160 of wireless devices 10 and 30 calculates an average value or median value of n radio wave intensities WI1 ′ to WIn ′ constituting reception signal profile RSSI_pro6. The calculated average value or median value is set as the threshold value Ith. Then, the key creation unit 160 of the radio apparatuses 10 and 30 deletes a predetermined number of radio field intensities close to the threshold value Ith from the n radio field intensities WI1 ′ to WIn ′, and the remaining j radio field intensities WI1. The secret keys Ks1 and Ks2 are created by multilingling “˜WIj” with the threshold value Ith.

  That is, the key creation unit 160 of the wireless devices 10 and 30 obtains threshold = 6 based on the received signal profile RSSI_pro6 and deletes a predetermined number of radio wave intensities close to the obtained threshold = 6. In this case, the key creation unit 160 of the wireless devices 10 and 30 deletes the sixth and last radio wave intensity of the received signal profile RSSI_pro6 (see (d) of FIG. 12), and the remaining j (= 128) pieces. The radio wave intensities WI1 ′ to WIj ′ are multi-valued by threshold = 6, and secret keys Ks1, Ks2 composed of a bit string [001000...] Are created (see (e) of FIG. 12).

  In the above description, it has been described that the profile generation unit 150 of the radio apparatuses 10 and 30 calculates the product of two independent radio field strengths to generate the reception signal profile RSSI_pro6. However, in the present invention, the reception signal profile The i-th radio wave intensity WIi and i + α-th radio wave intensity WIi + α of profile RSSI_pro4 are selected, and the product of the selected i-th radio wave intensity WIi and i + α-th radio wave intensity WIi + α is calculated to obtain i of received signal profile RSSI_pro6. The i + 1-th radio wave intensity WIi + 1 and i + α + 1-th radio wave intensity WIi + α + 1 of the received signal profile RSSI_pro4, and the product of the selected i + 1-th radio wave intensity WIi + 1 and i + α + 1-th radio wave intensity WIi + α + 1. Calculate and receive The i + 1-th radio wave intensity of the communication signal profile RSSI_pro6 may be generated.

  In this case, when the last radio wave intensity = [− 2] of the received signal profile RSSI_pro4 is selected as the i-th radio wave intensity WIi, the α-th radio wave intensity from the top of the received signal profile RSSI_pro4 is set as the i + α-th radio wave intensity WIi + α. Selected. Accordingly, the profile generation unit 150 of the wireless devices 10 and 30 selects the i-th radio wave intensity WIi and the i + α-th radio wave intensity WIi + α from the n radio wave intensities WI1 to WIn arranged in a ring shape.

[Secret key creation method 6]
FIG. 13 is a diagram illustrating a sixth example of a secret key creation method. In addition, each numerical value shown to (a)-(e) of FIG. 13 shows the received signal strength of an electromagnetic wave, and a unit is dBm. The profile generation unit 150 of the wireless devices 10 and 30 generates the reception signal profile RSSI_pro5 based on the reception signal profile RSSI_org according to (a) to (c) of FIG. 11 showing [Secret key generation method 4] (FIG. 13 (a) to (c)).

  Thereafter, the profile generation unit 150 of the wireless devices 10 and 30 calculates the absolute value of each of the n radio field intensities WI1 ′ to WIn ′ constituting the received signal profile RSSI_pro5 and calculates the n radio field intensities | WI1 ′ | A reception signal profile RSSI_pro7 composed of | WIN ′ | is generated (see (d) of FIG. 13), and the generated reception signal profile RSSI_pro7 is output to the key creation unit 160.

  When receiving the received signal profile RSSI_pro7 from the profile generating unit 150, the key generating unit 160 of the wireless devices 10 and 30 receives an average value of n radio field intensities | WI1 ′ | to | WIN ′ | constituting the received signal profile RSSI_pro7 or The median value is calculated, and the calculated average value or median value is set as the threshold value Ith. Then, the key creation unit 160 of the wireless devices 10 and 30 deletes a predetermined number of radio field intensities close to the threshold value Ith from the n radio field intensities | WI1 ′ | to | WINIn | The secret keys Ks1 and Ks2 are generated by converting the radio wave intensity | WI1 ′ | to | WIj ′ |

  That is, the key creation unit 160 of the wireless devices 10 and 30 obtains a threshold value = 6.9 based on the received signal profile RSSI_pro7, and sets a predetermined number of radio wave intensities close to the obtained threshold value = 6.8. delete. In this case, the key creation unit 160 of the wireless devices 10 and 30 deletes the sixth, eleventh to thirteenth and last radio wave intensities of the received signal profile RSSI_pro7 (see (e) of FIG. 13), and the rest J (= 128) field strengths | WI1 ′ | to | WIj ′ | are multi-valued with a threshold value = 6.8 to generate secret keys Ks1, Ks2 composed of bit strings [0001110001. (See (f) of FIG. 13).

  As described above, in the secret key creation method 6, the absolute value of the product of two consecutive radio wave intensities is calculated to create the secret keys Ks1 and Ks2.

  In this secret key creation method 6, the secret keys Ks1 and Ks2 may be created by calculating the absolute values of a plurality of radio wave intensities constituting the received signal profile RSSI_pro6 shown in FIG.

[Secret key creation method 7]
FIG. 14 is a diagram illustrating a seventh example of a secret key creation method. In addition, each numerical value shown to (a)-(c) of FIG. 14 shows the received signal strength of an electromagnetic wave, and a unit is dBm. The profile generation unit 150 of the wireless devices 10 and 30 generates the above-described reception signal profile RSSI_org based on the n radio waves received from the antenna units 130 and 220, respectively (see (a) of FIG. 14). Then, the profile generation unit 150 of the wireless devices 10 and 30 outputs the generated reception signal profile RSSI_org to the key generation unit 160.

  When receiving the received signal profile RSSI_org from the profile generating unit 150, the key creating unit 160 of the wireless devices 10 and 30 converts the received radio signal strengths WI1 to WIn constituting the received received signal profile RSSI_org to m (m is 2 or more). Integer)) blocks BLK1 to BLKm, and threshold values Ith1 to Ithm are uniquely determined in each of the m blocks BLK1 to BLKm.

  In this case, the block BLK1 includes [2, 4, 4, 5, −7, 0], and the block BLK2 includes [6, 4, 4, −4, 6, 6]. The key generation unit 160 determines the threshold value Ith1 in the block BLK1 to be “1.3”, determines the threshold value Ith2 in the block BLK2 to be “4.3”, and so on. The threshold value Ithm is determined to be “2.1” (see FIG. 14B).

  Then, the key creation unit 160 of the wireless devices 10 and 30 deletes a predetermined number of radio wave intensities close to the threshold values Ith1 to Ithm for each of the blocks BLK1 to BLKm (see (c) of FIG. 14), and each of the blocks BLK1 to BLK1. The radio wave intensity remaining in BLKm is multi-valued by threshold values Ith1 to Ithm to generate secret keys Ks1, Ks2 consisting of bit string = [1111011 ...] (see FIG. 14D).

[Secret key creation method 8]
FIG. 15 is a diagram illustrating an eighth example of a secret key creation method. In addition, each numerical value shown to (a)-(d) of FIG. 15 shows the received signal strength of an electromagnetic wave, and a unit is dBm. The profile generation unit 150 of the radio apparatuses 10 and 30 generates the above-described reception signal profile RSSI_org based on the n radio waves received from the antenna units 130 and 220, respectively (see (a) of FIG. 15). Then, the profile generation unit 150 of the wireless devices 10 and 30 calculates the difference between two consecutive radio wave intensities in the generated reception signal profile RSSI_org array by the above-described method to generate the reception signal profile RSSI_pro1 (FIG. 15). The generated received signal profile RSSI_pro1 is output to the key creation unit 160.

  When receiving the received signal profile RSSI_pro1 from the profile generating unit 150, the key creating unit 160 of the wireless devices 10 and 30 converts the received n signal strengths WI1 to WIn constituting the received signal profile RSSI_pro1 into m blocks BLK1 to BLK1. The threshold values Ith1 to Ithm are uniquely determined in each of the m blocks BLK1 to BLKm.

  In this case, the block BLK1 is composed of [2, 0, 1, -12, 7, 6], and the block BLK2 is composed of [-2, 0, -8, 10, 0, 0]. The 30 key generation unit 160 determines the threshold value Ith1 in the block BLK1 to “0.6”, determines the threshold value Ith2 in the block BLK2 to “0”, and so on. The value Ithm is determined to be “1” (see FIG. 15C).

  Then, the key creation unit 160 of the wireless devices 10 and 30 deletes a predetermined number of radio wave intensities close to the threshold values Ith1 to Ithm for each of the blocks BLK1 to BLKm (see (d) in FIG. 15), and each of the blocks BLK1 to BLK1. The radio wave intensity remaining in BLKm is multi-valued by threshold values Ith1 to Ithm, and secret keys Ks1, Ks2 consisting of bit string = [011001...] Are created (see (e) of FIG. 15).

[Secret key creation method 9]
FIG. 16 is a diagram illustrating a ninth example of the secret key generation method. In addition, each numerical value shown to (a)-(e) of FIG. 16 shows the received signal strength of an electromagnetic wave, and a unit is dBm. The profile generation unit 150 of the radio apparatuses 10 and 30 generates the reception signal profile RSSI_org described above based on the n radio waves received from the antenna units 130 and 220, respectively (see (a) of FIG. 16). Then, the profile generation unit 150 of the wireless devices 10 and 30 normalizes the n radio wave intensities WI1 to WIn constituting the generated reception signal profile RSSI_org by the method described above to generate the reception signal profile RSSI_pro8 (FIG. 16). (See (b)).

  Thereafter, the profile generation unit 150 of the radio apparatuses 10 and 30 generates a reception signal profile RSSI_pro9 by squaring each of the n radio wave intensities WI1 to WIn constituting the reception signal profile RSSI_pro8 (see (c) of FIG. 16). ).

  And the profile production | generation part 150 of the radio | wireless apparatuses 10 and 30 will produce | generate reception signal profile RSSI_pro10 by calculating the difference of two continuous radio field strengths in the arrangement | sequence of the produced | generated reception signal profile RSSI_pro9, if the reception signal profile RSSI_pro9 is produced | generated. To do.

  More specifically, the profile generation unit 150 of the wireless devices 10 and 30 selects the first radio wave intensity [4] and the second radio wave intensity [0] from the received signal profile RSSI_pro9 and selects the selected By subtracting the first radio wave intensity [4] from the second radio wave intensity [0], the first radio wave intensity = [− 4] of the reception signal profile RSSI_pro10 is generated.

  Next, the profile generation unit 150 of the wireless devices 10 and 30 selects the second radio wave intensity = [0] and the third radio wave intensity = [0] of the received signal profile RSSI_pro9, and the selected second The second radio field intensity = [0] of the received signal profile RSSI_pro10 is generated by subtracting the second radio field intensity = [0] from the third radio field intensity = [0].

  Similarly, the profile generation unit 150 of the wireless devices 10 and 30 selects the i-th radio wave intensity WIi and the (i + 1) -th radio wave intensity WIi + 1 of the received signal profile RSSI_pro9, and selects the selected i + 1-th radio wave intensity. The i-th radio wave intensity WIi is subtracted from the radio wave intensity WIi + 1 to generate the i-th radio wave intensity of the reception signal profile RSSI_pro10. And the profile production | generation part 150 of the radio | wireless apparatuses 10 and 30 is [-4,0,1,120, -105, -12, -4,0,64, -60,0,0,0, ...,. 0] is generated (see (d) of FIG. 16).

  In this case, when the last radio wave intensity = [4] of the received signal profile RSSI_pro9 is selected as the i-th radio wave intensity WIi, the first radio wave intensity = [4] of the received signal profile RSSI_pro9 is the i + 1th radio wave intensity WIi + 1. Selected as. Accordingly, the profile generation unit 150 of the wireless devices 10 and 30 selects the i-th radio wave intensity WIi and the i + 1-th radio wave intensity WIi + 1 from the n radio wave intensities WI1 to WIn arranged in a ring shape.

  As described above, the profile generation unit 150 of the wireless devices 10 and 30 performs normalization processing and the difference between the squares of two continuous radio field intensities for the n radio field intensities WI1 to WIn received from the antenna units 130 and 220, respectively. The received signal profile RSSI_pro10 is generated by performing a predetermined calculation for calculating.

  And the profile production | generation part 150 of the radio | wireless apparatuses 10 and 30 will output the produced | generated reception signal profile RSSI_pro10 to the key preparation part 160, if reception signal profile RSSI_pro10 is produced | generated.

  When key generation unit 160 of radio apparatuses 10 and 30 receives reception signal profile RSSI_pro10 from profile generation unit 150, key generation unit 160 calculates an average value or median value of n radio wave intensities WI1 ′ to WIn ′ constituting reception signal profile RSSI_pro10. The calculated average value or median value is set as a threshold value Ith. Then, the key creation unit 160 of the radio apparatuses 10 and 30 deletes a predetermined number of radio field intensities close to the threshold value Ith from the n radio field intensities WI1 ′ to WIn ′, and the remaining j radio field intensities WI1. The secret keys Ks1 and Ks2 are created by multilingling “˜WIj” with the threshold value Ith.

  That is, the key creation unit 160 of the wireless devices 10 and 30 obtains the threshold = 0 based on the received signal profile RSSI_pro10 and deletes a predetermined number of radio wave intensities close to the obtained threshold = 0. In this case, the key creation unit 160 of the wireless devices 10 and 30 deletes the second, third, eighth, eleventh to thirteenth and last radio wave intensities of the received signal profile RSSI_pro10 (FIG. 16). The remaining j (= 128) radio wave intensities WI1 ′ to WIj ′ are multi-valued with a threshold value = 0 to generate secret keys Ks1 and Ks2 made up of a bit string [01100010...]. (See (f) of FIG. 16).

  In the above, the profile generation unit 150 of the wireless devices 10 and 30 selects the i-th radio wave intensity WIi and the (i + 1) -th radio wave intensity WIi + 1 from the received signal profile RSSI_pro8, and the selected i-th radio wave intensity WIi + 1. Although it has been described that the i-th radio wave intensity of the received signal profile RSSI_pro10 is generated by calculating the difference between the square of the radio wave intensity WIi and the square of the (i + 1) -th radio wave intensity WIi + 1, the present invention is not limited to this. The profile generation unit 150 of the devices 10 and 30 selects the i-th radio wave intensity WIi and the (i + 1) -th radio wave intensity WIi + 1 from the received signal profile RSSI_pro8, and k (k) of the selected i-th radio wave intensity WIi. Is the integer greater than or equal to 2) and the difference between the (i + 1) th radio wave intensity WIi + 1 and the k The i-th radio wave intensity of the received signal profile RSSI_pro10 may be calculated to select the i-th radio wave intensity WIi and the i + α-th radio wave intensity WIi + α from the received signal profile RSSI_pro8, and the selected i-th radio wave intensity is selected. The i-th radio wave intensity of the received signal profile RSSI_pro10 may be generated by calculating the difference between the k-th radio wave intensity WIi and the i + αth radio wave intensity WIi + α.

[Secret key creation method 10]
FIG. 17 is a diagram illustrating a tenth example of the secret key creation method. In addition, each numerical value shown to (a)-(e) of FIG. 17 shows the received signal strength of an electromagnetic wave, and a unit is dBm. The profile generation unit 150 of the wireless devices 10 and 30 generates the reception signal profile RSSI_org described above based on the n radio waves received from the antenna units 130 and 220, respectively (see (a) of FIG. 17). Then, the profile generation unit 150 of the wireless devices 10 and 30 normalizes the n radio wave intensities WI1 to WIn constituting the generated reception signal profile RSSI_org by the method described above to generate the reception signal profile RSSI_pro8 (FIG. 17). (See (b)).

  Thereafter, the profile generation unit 150 of the radio apparatuses 10 and 30 generates a reception signal profile RSSI_pro9 by squaring each of the n radio wave intensities WI1 to WIn constituting the reception signal profile RSSI_pro8 (see (c) of FIG. 17). ).

  Then, when the profile generation unit 150 of the radio apparatuses 10 and 30 generates the reception signal profile RSSI_pro9, the profile generation unit 150 calculates a difference between two independent radio wave intensities in the array of the generated reception signal profile RSSI_pro9 and receives the reception signal profile RSSI_pro11. Is generated.

  More specifically, the profile generation unit 150 of the wireless devices 10 and 30 selects the first radio wave intensity [4] and the second radio wave intensity [0] from the received signal profile RSSI_pro9 and selects the selected By subtracting the first radio wave intensity [4] from the second radio wave intensity [0], the first radio wave intensity = [− 4] of the reception signal profile RSSI_pro11 is generated.

  Next, the profile generation unit 150 of the wireless devices 10 and 30 selects the third radio wave intensity = [0] and the fourth radio wave intensity = [1] of the received signal profile RSSI_pro9, and the selected first The third radio wave intensity = [0] is subtracted from the fourth radio wave intensity = [1] to generate the second radio wave intensity = [1] of the reception signal profile RSSI_pro11.

  Similarly, the profile generation unit 150 of the wireless devices 10 and 30 selects the (2i-1) th radio wave intensity WI2i-1 and the 2i radio wave intensity WI2i of the received signal profile RSSI_pro9, and The (2i-1) -th radio wave intensity WI2i-1 is subtracted from the selected 2i-th radio wave intensity WI2i to generate the i-th radio wave intensity of the received signal profile RSSI_pro11. And the profile production | generation part 150 of the radio | wireless apparatuses 10 and 30 produces | generates the received signal profile RSSI_pro11 which consists of [-4, 1, -105, -4, 64, 0, 0, ...] ((of FIG. 17 ( d)).

  As described above, the profile generation unit 150 of the radio apparatuses 10 and 30 applies normalization processing and squares of two independent radio field intensities to the n radio field intensities WI1 to WIn received from the antenna units 130 and 220, respectively. The received signal profile RSSI_pro11 is generated by performing a predetermined calculation for calculating the difference between the received signal profile RSSI_pro11.

  And the profile production | generation part 150 of the radio | wireless apparatuses 10 and 30 will output the produced | generated reception signal profile RSSI_pro11 to the key preparation part 160, if reception signal profile RSSI_pro11 is produced | generated.

  When receiving the reception signal profile RSSI_pro11 from the profile generation unit 150, the key generation unit 160 of the wireless devices 10 and 30 calculates an average value or median value of the n radio field intensities WI1 ′ to WIn ′ constituting the reception signal profile RSSI_pro11. The calculated average value or median value is set as a threshold value Ith. Then, the key creation unit 160 of the radio apparatuses 10 and 30 deletes a predetermined number of radio field intensities close to the threshold value Ith from the n radio field intensities WI1 ′ to WIn ′, and the remaining j radio field intensities WI1. The secret keys Ks1 and Ks2 are created by multilingling “˜WIj” with the threshold value Ith.

  That is, the key creation unit 160 of the wireless devices 10 and 30 obtains a threshold value = −8.2 based on the received signal profile RSSI_pro11, and a predetermined number of radio waves close to the obtained threshold value = −8.2. Remove strength. In this case, the key creation unit 160 of the radio apparatuses 10 and 30 deletes the first, second, fourth, sixth, and seventh radio wave intensities of the received signal profile RSSI_pro10 ((( e)), the remaining j (= 128) radio wave intensities WI1 ′ to WIj ′ are multi-valued by a threshold = −8.2, and secret keys Ks1 and Ks2 including a bit string [01. It is created (see (f) of FIG. 17).

  In the above, the profile generation unit 150 of the wireless devices 10 and 30 selects the (2i-1) th radio wave intensity WI2i-1 and the 2i th radio wave intensity WI2i from the received signal profile RSSI_pro8, and It has been described that the difference between the square of the selected (2i-1) -th radio wave intensity WI2i-1 and the square of the 2i-th radio wave intensity WI2i is calculated to generate the i-th radio wave intensity of the received signal profile RSSI_pro11. In the present invention, the profile generation unit 150 of the radio apparatuses 10 and 30 is not limited to this, and the received signal profile RSSI_pro8 includes the (2i-1) th radio wave intensity WI2i-1 and the 2i th radio wave intensity WI2i. And the selected (2i-1) th radio wave intensity WI2i-1 to the k-th power and the 2ith power The i-th radio wave intensity of the received signal profile RSSI_pro11 may be generated by calculating the difference between the intensity WI2i and the k-th power, and the i-th radio wave intensity WIi and the i + αth radio wave intensity WIi + α from the received signal profile RSSI_pro8. And the difference between the selected i-th field strength WIi to the k-th power and the i + α-th field strength WIi + α to the k-th power is calculated to generate the i-th field strength of the received signal profile RSSI_pro11. Good.

  In this case, when the last radio wave intensity = [− 2] of the received signal profile RSSI_pro8 is selected as the i-th radio wave intensity WIi, the α-th radio wave intensity from the top of the received signal profile RSSI_pro8 is i + α-th radio wave intensity WIi + α. Selected. Accordingly, the profile generation unit 150 of the wireless devices 10 and 30 selects the i-th radio wave intensity WIi and the i + α-th radio wave intensity WIi + α from the n radio wave intensities WI1 to WIn arranged in a ring shape.

[Secret key creation method 11]
FIG. 18 is a diagram illustrating an eleventh example of the secret key generation method. The profile generation unit 150 of the radio apparatuses 10 and 30 generates the above-described reception signal profile RSSI_org based on the n radio waves received from the antenna units 130 and 220, respectively (see (a) of FIG. 18). The generated reception signal profile RSSI_org is output to the key creation unit 160.

  When receiving the reception signal profile RSSI_org from the profile generation unit 150, the key generation unit 160 of the wireless devices 10 and 30 determines the threshold value Ith of the n radio wave intensities WI1 to WIn constituting the reception signal profile RSSI_org. The n number of radio wave intensities WI1 to WIn are multi-valued by the threshold value Ith to generate the bit string Bclm1 (see FIG. 18B). In this case, the bit string Bclm1 has a section SEC in which five “0” s continue.

  When “0” or “1” continues for a reference value (for example, three) or more in an arbitrary section, the key creation unit 160 of the wireless devices 10 and 30 deletes the bit string in the section. Accordingly, the key creation unit 160 of the wireless devices 10 and 30 creates secret keys Ks1 and Ks2 including the bit string Bclm2 by deleting the section SEC in which five “0” s continue.

  In the secret keys Ks1 and Ks2 created by each of the secret key creation methods 1 to 11 described above, “0” or “1” is suppressed from being continuously arranged (FIGS. 8 to 18). The various operations in the secret key creation methods 1 to 10 and the process in the secret key creation method 11 constitute a “predetermined process” that suppresses a continuous arrangement of the same bit values.

  In the secret key generation methods 1 to 10 described above, the n key radio wave strengths WI1 to WIn received by the antenna units 130 and 220 are subtracted, multiplied, and subtracted after the power to obtain a secret key. In the present invention, the sum of the i-th radio wave intensity WIi and the i + α-th radio wave intensity WIi + α, i-th, is not limited to this. The sum of the kth power of the radio field intensity WIi and the kth power of the i + αth radio field intensity WIi + α, the division of the ith radio field intensity WIi and the i + αth radio field intensity WIi + α, and the kth power of the ith radio field intensity WIi The secret keys Ks1 and Ks2 may be generated by performing operations such as division of the i + αth radio wave intensity WIi + α with the k-th power.

  In the present invention, the secret keys Ks1 and Ks2 may be created by combining at least two of the secret key creation methods 1 to 11 described above.

  FIG. 19 is a flowchart for explaining an operation of creating a secret key between two wireless devices 10 and 30 and performing encrypted communication using any one of the creation methods 1 to 10 described above.

  When a series of operations is started, the transmission processing unit 120 of the wireless device 30 sets i = 1 (step S1). And the directivity setting part 230 of the radio | wireless apparatus 30 sets the directivity of the array antenna 20 to one directivity Di by the control voltage set CLV1 (step S2).

  Thereafter, the signal generation unit 110 of the wireless device 10 generates a packet PKT1 including predetermined data and outputs the packet PKT1 to the transmission processing unit 120. The transmission processing unit 120 of the wireless device 10 performs processing such as frequency conversion and modulation on the packet PKT1, and transmits radio waves constituting predetermined data to the wireless device 30 via the antenna 11 (antenna unit 130) (step S3). ).

  In the wireless device 30, the array antenna 20 (antenna unit 230) receives radio waves from the radio device 10 and outputs the received radio waves to the profile generation unit 150. The profile generation unit 150 of the wireless device 30 detects the intensity WI2i of the radio wave received from the array antenna 20 (step S4).

  Thereafter, the signal generation unit 110 of the wireless device 30 generates a packet PKT1 including predetermined data and outputs the packet PKT1 to the transmission processing unit 120. The transmission processing unit 120 of the wireless device 30 performs processing such as frequency conversion and modulation on the packet PKT1, and transmits radio waves constituting predetermined data to the wireless device 10 via the array antenna 20 (step S5).

  In the wireless device 10, the antenna 11 (antenna unit 130) receives the radio wave from the radio device 30 and outputs the received radio wave to the profile generation unit 150. The profile generation unit 150 of the wireless device 10 detects the intensity WI1i of the radio wave received from the antenna 11 (step S6).

  Thereafter, the transmission processing unit 120 of the wireless device 30 determines whether i = n (= 384) (step S7). When i = n is not satisfied, the transmission processing unit 120 of the wireless device 30 sets i = i + 1 (step S8), and steps S2 to S8 are repeatedly executed until it is determined in step S7 that i = n. Is done. That is, the directivity of the array antenna 20 is changed to n directivities by the control voltage sets CLV1 to CLVn, and predetermined data is configured between the antenna 11 of the wireless device 10 and the array antenna 20 of the wireless device 30. Steps S2 to S8 are repeatedly executed until radio waves are transmitted and received and the radio wave intensities WI11 to WI1n and WI21 to WI2n are detected.

  If it is determined in step S7 that i = n, in the wireless device 30, the profile generation unit 150 performs a predetermined calculation (the calculation shown in the generation method 1 to the generation method 10) on the n radio wave intensities WI21 to WI2n. 1) to generate n radio field strengths WI21 ′ to WI2n ′ (step S9), and to generate a received signal profile RSSI_pro including the generated n radio field strengths WI21 ′ to WI2n ′. To 160.

  The key creation unit 160 of the wireless device 30 calculates a threshold value based on the average value or the median value from the received signal profile RSSI_pro, and a predetermined number (= 256) of radio field strengths having intensities close to the calculated threshold value. , And j (128) radio wave intensities WI21 ′ to WI2j ′ are selected from the n radio wave intensities WI21 ′ to WI2n ′. Then, the key creation unit 160 of the wireless device 30 multi-values the j radio field intensities WI21 ′ to WI2j ′ using threshold values, and creates a secret key Ks2 having each of the multi-values as a bit pattern ( Step S10).

  In addition, the profile generation unit 150 of the wireless device 10 performs a predetermined calculation (any of the calculations shown in the creation method 1 to the creation method 10) on the n radio field strengths WI11 to WI1n, and the n radio field strengths WI11 ′ to WI11 ′. WI1n ′ is generated (step S11), and a reception signal profile RSSI_pro including the generated n radio wave intensities WI11 ′ to WI1n ′ is generated and output to the key generation unit 160.

  The key creation unit 160 of the wireless device 10 calculates a threshold value based on the average value or the median value from the received signal profile RSSI_pro, and a predetermined number (= 256) of radio field strengths having intensities close to the calculated threshold value. , And j (128) radio wave intensities WI11 ′ to WI1j ′ are selected from the n radio wave intensities WI11 ′ to WI1n ′. Then, the key creation unit 160 of the wireless device 10 multi-values the j radio wave intensities WI11 ′ to WI1j ′ using threshold values, and creates a secret key Ks1 having each of the multi-values as a bit pattern ( Step S12).

  Thereafter, in the wireless device 10, the key creation unit 160 outputs the secret key Ks 1 to the key matching confirmation unit 170. The data generation unit 171 of the key matching confirmation unit 170 generates the key confirmation data DCFM1 by the method described above and outputs it to the transmission processing unit 120 and the data comparison unit 172. The transmission processing unit 120 performs processing such as modulation on the key confirmation data DCFM1, and transmits the key confirmation data DCFM1 to the wireless device 30 via the antenna unit 130.

  Then, the antenna unit 130 receives the key confirmation data DCFM2 generated in the wireless device 30 from the wireless device 30, and outputs the received key confirmation data DCFM2 to the reception processing unit 140. The reception processing unit 140 performs predetermined processing on the key confirmation data DCFM2 and outputs the key confirmation data DCFM2 to the data comparison unit 172 of the key matching confirmation unit 170.

  The data comparison unit 172 compares the key confirmation data DCFM1 from the data generation unit 171 with the key confirmation data DCFM2 from the reception processing unit 140. Then, when the key confirmation data DCFM1 matches the key confirmation data DCFM2, the data comparison unit 172 generates a coincidence signal MTH and outputs it to the result processing unit 173. The result processing unit 173 stores the secret key Ks1 from the key creation unit 160 in the key storage unit 180 according to the match signal MTH.

  On the other hand, when the key confirmation data DCFM1 does not match the key confirmation data DCFM2, the data comparison unit 172 generates a mismatch signal NMTH and outputs it to the transmission processing unit 120 and the key matching unit 190. The transmission processing unit 120 transmits the mismatch signal NMTH to the radio apparatus 30 via the antenna unit 130. Then, the wireless device 30 detects that the wireless device 10 has confirmed that the secret keys Ks1 and Ks2 do not match.

  Thereby, the confirmation of the key agreement in the wireless device 10 ends (step S13).

  Instead of the key matching confirmation in the wireless device 10, a key matching confirmation may be performed in the wireless device 30 (step S14).

When it is confirmed in step S13 that the secret keys Ks1 and Ks2 do not match, the pseudo syndrome generation unit 191 of the key matching unit 190 receives the mismatch signal NMTH from the key match confirmation unit 170 in the wireless device 10. Then, the pseudo syndrome generator 191 detects the bit pattern x1 of the secret key Ks1 received from the key generator 160 according to the mismatch signal NMTH, and calculates the syndrome s1 = x1H ^T of the detected bit pattern x1.

Pseudo syndrome creation unit 191 outputs the syndrome s1 = x1H ^T which is calculated to mismatch bit detector 192, and outputs the bit pattern x1 to key mismatch corrector 193.

On the other hand, the wireless device 30 receives a disagreement signal NMTH from radio device 10 in step S13, in response to the received mismatch signal NMTH, to the radio device 10 calculates a syndrome s2 = x2H ^T.

Antenna unit 130 of radio device 10 receives and outputs syndrome s2 = x2H ^T from radio device 30 to the reception processing unit 140. Reception processing unit 140 performs predetermined processing on the syndrome s2 = x2H ^T, and outputs the syndrome s2 = x2H ^T to the key matching unit 190.

Mismatch bit detector 192 of the key agreement unit 190 receives a syndrome s2 = x2H ^T created in the wireless device 30 from the reception processing unit 140. The mismatch bit detector 192 calculates a difference s = s1-s2 of the syndrome s2 = x2H ^T created in the syndrome s1 = x1H ^T and the wireless device 30 that was created in the wireless device 10.

Thereafter, mismatch bit detector 192 confirms that the s ≠ 0, is calculated on the basis of a bit pattern e = x1-x2 key mismatch s = eH ^T, the bit pattern e of the operated key mismatch The data is output to the key mismatch correction unit 193.

  The key mismatch correction unit 193 uses the bit pattern x1 from the pseudo syndrome generation unit 191 and the key mismatch bit pattern e from the mismatch bit detection unit 192 to generate the bit pattern of the secret key Ks2 generated in the wireless device 30. x2 = x1-e is calculated.

  Then, the data generation unit 194, the data comparison unit 195, and the result processing unit 196 confirm the coincidence of the matched keys x2 = x1-e by the same operation as the key coincidence confirmation operation in the key coincidence confirmation unit 170.

  Thereby, the key mismatch countermeasure is completed (step S15).

  In place of the key mismatch countermeasure in the wireless device 10, a key mismatch countermeasure may be taken in the wireless device 30 (step S16).

  When it is confirmed in step S13 that the secret key Ks1 matches the secret key Ks2, or when a countermeasure for key mismatch is taken in step S15, the encryption unit 200 of the wireless device 10 receives the secret key Ks1 from the key storage unit 180. Is transmitted, the transmission data is encrypted, and the encrypted transmission data is output to the transmission processing unit 120. Then, the transmission processing unit 120 modulates the encrypted transmission data and transmits the encrypted transmission data to the wireless device 30 via the antenna unit 130.

  Further, the antenna unit 130 of the wireless device 10 receives the encrypted transmission data from the wireless device 30, and outputs the received encrypted transmission data to the reception processing unit 140. The reception processing unit 140 performs a predetermined process on the encrypted transmission data and outputs the encrypted transmission data to the decryption unit 210.

  The decryption unit 210 decrypts the encrypted transmission data from the reception processing unit 140 with the secret key Ks1, and acquires the reception data.

  Thereby, the encryption / decryption with the secret key Ks1 is completed (step S17).

  The wireless device 30 also performs encryption / decryption using the secret key Ks2 by the same operation as the wireless device 10 (step S18). And a series of operation | movement is complete | finished.

  FIG. 20 is a flowchart for explaining an operation of creating a secret key between two wireless devices 10 and 30 and performing encrypted communication using the creation method 11 described above. The flowchart shown in FIG. 20 is the same as the flowchart shown in FIG. 19 except that steps S9 to S12 in the flowchart shown in FIG. 19 are replaced with steps S9A to S12A, respectively.

  If it is determined in step S7 described above that i = n, the profile generation unit 150 of the wireless device 30 generates a reception signal profile RSSI_org including n radio wave intensities WI21 to WI2n, and the generated reception signal The profile RSSI_org is output to the key creation unit 160. Then, when receiving the reception signal profile RSSI_org from the profile generation unit 150, the key creation unit 160 of the wireless device 30 determines from the average value or the median value of the n radio field intensities WI21 to WI2n constituting the received reception signal profile RSSI_org. And the n number of radio wave intensities WI21 to WI2n are multi-valued according to the obtained threshold to generate a bit string Bclm2_org (step S9A).

  Then, the key creation unit 160 of the wireless device 30 creates a secret key Ks2 by deleting any section in the bit string Bclm2_org where the same bit value continuously exists above the reference value (step S10A).

  Thereafter, the profile generation unit 150 of the wireless device 10 generates a reception signal profile RSSI_org including n radio field strengths WI11 to WI1n, and outputs the generated reception signal profile RSSI_org to the key generation unit 160. When receiving the reception signal profile RSSI_org from the profile generation unit 150, the key generation unit 160 of the wireless device 10 receives the average value or median value of the n radio field intensities WI11 to WI1n constituting the received reception signal profile RSSI_org. And the n radio wave intensities WI11 to WI1n are multi-valued according to the obtained threshold value to generate a bit string Bclm1_org (step S11A).

  Then, the key creation unit 160 of the wireless device 30 creates a secret key Ks1 by deleting any section in the bit string Bclm1_org where the same bit value continuously exists above the reference value (step S12A).

  Then, each step after step S13 mentioned above is performed, and a series of operations are completed.

  The operations of steps S3 and S4 shown in FIG. 19 and FIG. 20 are performed by transmitting a radio wave for generating a reception signal profile RSSI_org in the wireless device 30 from the antenna 11 of the wireless device 10 to the array antenna 20 of the wireless device 30; The radio device 30 detects the radio wave intensity WI2i. The operations shown in steps S5 and S6 are performed by the radio device 10 to generate radio waves from the array antenna 20 of the radio device 30 for generating the reception signal profile RSSI_org. The radio device 10 detects the intensity WI1i of the radio wave. Then, transmission of the radio wave constituting the predetermined data from the antenna 11 of the radio apparatus 10 to the array antenna 20 of the radio apparatus 30 and transmission from the array antenna 20 of the radio radio apparatus 30 constituting the predetermined data to the antenna 11 of the radio apparatus 10 are performed. Transmission to is performed alternately with the directivity of the array antenna 20 set to one directivity. That is, radio waves constituting predetermined data are transmitted and received between the antenna 11 of the wireless device 10 and the array antenna 20 of the wireless device 30 by time division duplex (TDD) or the like.

  Accordingly, the directivity of the array antenna 20 is set to one directivity, and radio waves constituting predetermined data are transmitted from the antenna 11 of the radio apparatus 10 to the array antenna 20 of the radio apparatus 30, and the radio apparatus 30 receives the radio wave intensity WI2i. Immediately after the signal is detected, the radio waves constituting the same predetermined data can be transmitted from the array antenna 20 of the radio apparatus 30 to the antenna 11 of the radio apparatus 10 so that the radio apparatus 10 can detect the radio field intensity WI1i. As a result, radio waves constituting predetermined data can be transmitted and received between the radio apparatuses 10 and 30 while ensuring the same transmission path characteristics between the radio apparatuses 10 and 30, and n radio wave intensities WI11 to WI1n can be obtained due to the reversibility of the radio waves. It can be made to correspond to n radio field strengths WI21 to WI2n, respectively. As a result, the j radio field intensities WI11 'to WI1j' can be matched with the j radio field intensities WI21 'to WI2j', respectively. Then, the secret key Ks1 created in the wireless device 10 can be easily matched with the secret key Ks2 created in the wireless device 30.

  In addition, since radio waves constituting the predetermined data are transmitted and received between the wireless devices 10 and 30 by time division duplex (TDD) or the like, the predetermined data is transmitted via one array antenna 20 while suppressing radio wave interference. The radio wave to be configured can be transmitted and received between the wireless devices 10 and 30.

  Furthermore, since the key confirmation data DCFM1 to DCFM1-4 are generated by performing irreversible computations or one-way computations on the secret keys Ks1 and Ks2, even if the key confirmation data DCFM1 to DCFM4 are wiretapped, they are secret. The risk that the keys Ks1 and Ks2 are decrypted can be extremely reduced.

Furthermore, syndromes s1, s2, so obtained by multiplying the transposed matrix ^{H T} of the parity check matrix H in the key x1, x2 indicating the bit pattern of the secret key Ks1, Ks2, immediately be syndromes s1, s2 are eavesdropped information This bit pattern is not inferred unless a special encoding is assumed. Therefore, eavesdropping can be suppressed and the secret keys can be matched.

  Further, n radio field strengths WI11 to WI1n, WI21 to WI2n are subjected to a predetermined calculation to generate n radio field strengths WI11 ′ to WI1n ′ and WI21 ′ to WI2n, and the generated n radio field strengths WI11 ′. Since the j radio field strengths WI11 ′ to WI1j ′ and WI21 ′ to WI2j ′ selected from WI1n ′ and WI21 ′ to WI2n are multi-valued to generate the secret keys Ks1 and Ks2, the wiretapping device 50 It is not possible to detect what kind of calculation is being performed in the radio devices 10 and 30, and nj radio field intensities out of n radio field intensities WI11 ′ to WI1n ′ and WI21 ′ to WI2n ′. It is confirmed that j radio field strengths WI11 ′ to WI1j ′ and WI21 ′ to WI2j ′ are selected and j-bit secret keys Ks1 and Ks2 are generated. Can not. Then, even if the key lengths of the secret keys Ks1, Ks2 are known, if the secret key is decrypted by the brute force method, the secret key cannot be decrypted within a practical period. Therefore, the keys of the secret keys Ks1, Ks2 If the length is unknown, the secret keys Ks1 and Ks2 can hardly be decrypted. Therefore, wiretapping of the secret keys Ks1 and Ks2 by the wiretapping device 50 can be suppressed.

  The operation of performing communication between the wireless devices 10 and 30 is actually performed by a CPU (Central Processing Unit), and the CPU mounted on the wireless device 10 performs steps S3, S6, and S11 shown in FIG. , S12, S13, S15, S17 is read from a ROM (Read Only Memory), and the CPU mounted on the wireless device 30 performs steps S1, S2, S4, S5, S7 to S10, S14 shown in FIG. , S16 and S18 are read from the ROM, and the two CPUs mounted on the wireless devices 10 and 30 execute the read programs and perform communication between the wireless devices 10 and 30 according to the flowchart shown in FIG. .

  Further, the CPU mounted on the wireless device 10 reads a program including the steps S3, S6, S11A, S12A, S13, S15, and S17 shown in FIG. 20 reads out a program including each step S1, S2, S4, S5, S7, S8, S9A, S10A, S14, S16, and S18 from the ROM, and the two CPUs mounted on the wireless devices 10 and 30 read the program. The wireless device 10 and 30 communicate with each other according to the flowchart shown in FIG.

  Accordingly, the ROM corresponds to a computer (CPU) readable recording medium that records a program for causing the computer (CPU) to perform an operation of performing communication between the wireless devices 10 and 30.

  Hereinafter, the result of the random number test of the secret keys Ks1 and Ks2 created by the creation method according to the present invention will be described. As the random number test, items related to the random number of FIPS PUB 140-2 and the NIST 800-22 test in FIPS (Federal Information Processing Standards) of the information processing equipment procurement standard FIPS (Federal Information Processing Standards) of the US federal government were used.

  FIPS PUB 140-2 provides four types of items related to random numbers: The Monobit Test, The Poker Test, The Runs Test, and The Longruns Test. In the present invention, the Poker Test and the Poker Test Test was used.

The Poker Test divides a binary sequence of 20000 bits into 5000 cells each having 4 bits. Then, there are 2 ⁴ = 16 types of cell patterns, and the number of appearances g _p is counted for each pattern (the pattern number is p = 0 to 15). Then, when the appearance frequency of a certain pattern becomes higher (lower), the statistic x becomes larger. The statistic x is expressed by the following equation.

  The Poker Test was performed depending on whether the statistic x satisfies 2.16 <x <46.17.

  The Runs Test counts the number of runs (= continuation of the same bit value) of a certain length appearing in a binary sequence of 20000 bits. This test is performed individually for run lengths of 1, 2, 3, 4, 5 and 6 or more. Since each of the bit values “0” and “1” is performed, a total of 12 tests are performed.

  As the statistic x, the number of runs of each length appearing in 20000 bits is used, and the selection range shown in Table 1 is used as the selection range of the statistic x.

  The NIST 800-22 test consists of the following 16 items.

N1: One-dimensional frequency test N2: Block unit frequency test N3: Continuous test N4: Longest block test in block unit N5: Binary matrix rank test N6: Discrete Fourier transform test N7: Non-overlapping template fit test N8: Overlapping N9: Maurer's universal statistical test N10: Lempel-Ziv compression test N11: Linear complexity test N12: Series test N13: Approximate entropy test N14: Cumulative sum test N15: Random deviation test N16: Various random deviations Test The one-dimensional frequency test is a test for examining the deviation from the standard normal distribution of the appearance frequency of “1” in the random number sequence. The block-by-block frequency test is a test in which a random number sequence is divided in units of m bits, and the appearance frequency of “1” in each partial sequence is examined by chi-square test. The continuous test is a test in which the number of places where Xi ≠ Xi + 1 in the random number sequence {Xi} is obtained and the deviation from the standard normal distribution is examined.

  The longest run test in block units divides a random number sequence in m bits, assigns each subsequence to 7 ranks according to the length of the longest run, and tests the frequency by chi-square test. This is a test to check the bias. In the binary matrix rank test, a random number sequence is divided into non-overlapping blocks of length M × Q, and an M × Q binary matrix is constructed from each block. Each matrix is assigned to three classes according to the rank, and the frequency is tested by chi-square test to check the rank bias.

  The discrete Fourier transform test is a test for examining the periodicity of a random number sequence by decomposing a random number sequence into frequency components by discrete Fourier transform and examining the ratio at which the peak at each frequency exceeds a threshold value. In the template matching test without overlapping, the random number sequence is divided into eight blocks, and an m-bit window is slid for each block from the top, and the probability that the window and the m-character template match is examined. Then, the number of fits of each of the 8 blocks is tested by a chi-square test to check the bias of the number of matches.

  In the template matching test with overlap, the random number sequence is divided into 968 blocks, each block is assigned to 6 classes according to the number of times the m-character template is matched, and the frequency is tested by chi-square test. It is a test to check the bias of.

  Maurer's universal statistical test is a test for examining the uniformity and compressibility of a random number sequence by examining the interval between patterns of length L bits in the random number sequence. The Lempel-Ziv compression test is a test for examining the uniformity / compressibility of a random number sequence by examining the total number of different subsequences using a Lempel-Ziv algorithm.

  The linear complexity test is a test for examining the periodicity of a random number sequence by dividing a random number sequence into length M blocks and obtaining the linear complexity for each block using the Berlekamp-Massery algorithm. The series test is performed by checking whether a m-bit length pattern, a length m-1 bit pattern, and a length m-2 bit pattern appear uniformly in a random number sequence. This is a test to examine the possibility and compressibility.

The approximate entropy test is a test for checking the uniformity and compressibility of a random number sequence by checking whether a pattern of m bits in length and a pattern of m + 1 bits in length appear uniformly. is there. The cumulative sum test is a test for calculating a sum S _i from the head and tail to the i-th bit for a random number sequence, obtaining the maximum value, and examining the deviation of the obtained maximum value from the standard normal distribution. .

In the random deviation test, S _i represented by the following equation is obtained for the random number sequence {Xj}, and it is considered that one cycle from S _i = to “0” is -4 to −1, and 1 It is a test for examining the bias of the appearance frequency of the cycle for each of the eight states of -4.

Various random deviations assay determines the _{S i} by the formula (2) with respect to random number sequence {Xj}, is -9-1, and 1-9 of 18 kinds of examining the deviation of frequency of occurrence of state test .

  The items shown in N2, N4, N11, N12, and N14 are the minimum necessary items when performing the NIST 800-22 test.

  In addition, as a sample for comparison with the above-described The Poker Test, The Runs Test, and NIST 800-22 test, a secret key created by interleaving n radio wave intensities WI1-WIN was used.

  FIG. 21 is a conceptual diagram of interleaving processing. Assuming that the array of n radio field intensities WI1 to WIn is the radio field intensity array WI, the radio field intensity array WI is divided into blocks BLK1 to BLK3. Then, the first radio wave intensity WI1 included in the block BLK1 is selected, then the first radio wave intensity WIL + 1 included in the block BLK2 is selected, and then the first radio wave intensity WI2L + 1 included in the block BLK3 is selected. select.

  When the first radio wave intensity WI1, WIL + 1, WI2L + 1 is selected from each of the three blocks BLK1 to BLK3, the process returns to the block BLK1, selects the second radio wave intensity WI2 included in the block BLK1, and then selects the block BLK2. The second radio wave intensity WIL + 2 included is selected, and then the radio wave intensity WI2L + 2 included in the block BLK3 is selected.

  Hereinafter, similarly, one radio wave intensity is sequentially selected from the three blocks BLK1 to BLK3 and arranged.

In this case, when the radio wave intensity selected from the block BLK3 is lost, one radio wave intensity is sequentially selected from the two blocks BLK1, BLK2.
That is, as shown by the arrows in FIG. 21, one radio wave intensity is sequentially selected from the three blocks BLK1 to BLK3 and arranged.

  As a result, a rearranged radio wave intensity array WI_EX in which the radio wave intensity WI1, WIL + 1, WI2L + 1,.

  When the rearranged radio wave intensity array WI_EX is obtained, an average value or median value of n pieces of rearranged radio wave intensity WI1, WIL + 1, WI2L + 1,. A predetermined number of rearranged radio wave strengths close to the obtained threshold value are deleted, and the remaining j rearranged radio wave strengths are multivalued by the threshold value to create a secret key. The above is a method for creating a secret key by interleaving.

  As a result of performing the above-mentioned The Poker Test and The Runs Test for the secret keys Ks1 and Ks2 created by the above-described secret key creation method 3 (a method of calculating the difference between two independent continuous radio wave strengths), interleaving processing is performed. Passed both The Poker Test and The Runs Test.

  On the other hand, as a result of performing the above-mentioned The Poker Test and The Runs Test on the secret key created without using the method of calculating the difference between two independent continuous radio field strengths, It failed the Poker Test and The Runs Test, and passed the The Poker Test and The Runs Test for the first time by applying the interleaving process once.

  Next, the results of the NIST 800-22 test will be described. The samples used for the NIST 800-22 test are the following seven types of samples.

SPL1. Secret key length: 636288, interleave processing: once SPL2. Secret key length: 636288, Interleave processing: 2 times SPL3. Secret key length: 636288, interleave processing: 3 times SPL4. Secret key length: 1336768, interleave processing: once SPL5. Secret key length: 1336768, interleave processing: 2 times SPL6. Secret key length: 1336768, interleave processing: 3 times SPL7. Secret key length: 636288, secret key creation method 1
Table 2 shows the results of the NIST 800-22 test for samples SPL1 to SPL7.

  Note that “*” in Table 2 represents the minimum necessary items for the NIST 800-22 test.

  From the results shown in Table 2, the method of creating the secret keys Ks1 and Ks2 by calculating the difference between two consecutive radio wave intensities in the array of n radio wave intensities WI1 to WIn is the minimum necessary for the NIST800-22 test. It is possible to create a secret key that has passed the item and is less likely to be wiretapped than a method of creating a secret key using interleave processing.

  As described above, it has been found that the method of generating the secret keys Ks1 and Ks2 by performing a predetermined calculation on the n radio wave intensities WI1 to WIn is effective as a method of generating a secret key that is difficult to be wiretapped.

  In the above, of the two wireless devices 10 and 30 that perform wireless communication, one wireless device 10 is equipped with the omnidirectional antenna 11 and the other wireless device 30 electrically switches directivity. Although it has been described that the possible array antenna 20 is mounted, the present invention is not limited to this, and both the wireless devices 10 and 30 may be mounted with omnidirectional antennas. 30 may be equipped with an array antenna 20 that can electrically switch directivity.

  Even if both radio apparatuses 10 and 30 are equipped with omnidirectional antennas, by performing a predetermined calculation on the detected n radio wave intensities, “0” and “1” in the secret keys Ks1 and Ks2 The distribution can be distributed and wiretapping of the secret keys Ks1, Ks2 can be prevented.

  Further, the present invention comprises a bit string obtained by multi-valued n radio wave intensities WI1 to WIn or a bit string in which the n consecutive radio wave intensities WI1 to WIn are subjected to predetermined processing to suppress a continuous arrangement of the same bit values. What is necessary is just to generate the secret keys Ks1, Ks2.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and is intended to include meanings equivalent to the scope of claims for patent and all modifications within the scope.

  The present invention is applied to a wireless communication system capable of suppressing eavesdropping of a secret key by improving the randomness of the secret key. In addition, the present invention is applied to a wireless device used in a wireless communication system that can suppress the eavesdropping of a secret key by improving the randomness of the secret key.

1 is a schematic diagram of a radio communication system according to an embodiment of the present invention. It is a schematic block diagram of one radio | wireless apparatus shown in FIG. FIG. 3 is a schematic block diagram of the other wireless device shown in FIG. 1. It is a schematic block diagram of the directivity setting part shown in FIG. FIG. 4 is a schematic block diagram of a key matching confirmation unit shown in FIGS. 2 and 3. FIG. 4 is a schematic block diagram of a key matching unit shown in FIGS. 2 and 3. It is a conceptual diagram of received signal strength. It is a figure which shows the 1st example of the production method of a secret key. It is a figure which shows the 2nd example of the production method of a secret key. It is a figure which shows the 3rd example of the production method of a secret key. It is a figure which shows the 4th example of the production method of a secret key. It is a figure which shows the 5th example of the production method of a secret key. It is a figure which shows the 6th example of the production method of a secret key. It is a figure which shows the 7th example of the production method of a secret key. It is a figure which shows the 8th example of the production method of a secret key. It is a figure which shows the 9th example of the production method of a secret key. It is a figure which shows the 10th example of the production method of a secret key. It is a figure which shows the 11th example of the production method of a secret key. It is a flowchart for demonstrating the operation | movement which produces a secret key between two radio | wireless apparatuses using either of the production methods 1-10 produced above, and performs encryption communication. It is a flowchart for demonstrating the operation | movement which produces a secret key between two radio | wireless apparatuses using the preparation method 11 mentioned above, and performs encryption communication. It is a conceptual diagram of an interleaving process.

Explanation of symbols

  10, 30 wireless device, 11, 51 antenna, 20 array antenna, 21-27 antenna element, 40, 66 obstacle, 50 wiretapping device, 100 wireless communication system, 110 signal generation unit, 120 transmission processing unit, 130, 220 antenna , 140 reception processing unit, 150 profile generation unit, 160 key generation unit, 170 key matching confirmation unit, 171, 194 data generation unit, 172, 195 data comparison unit, 173, 196 result processing unit, 180 key storage unit, 190 Key matching unit, 191 pseudo syndrome generation unit, 192 mismatch bit detection unit, 193 key mismatch correction unit, 200 encryption unit, 210 decryption unit, 230 directivity setting unit, 231 to 236 varactor diode, 237 control voltage generation circuit.

Claims (14)

First and second antennas;
First and second wireless devices that transmit and receive radio waves by a wireless transmission path via the first and second antennas,
The first radio apparatus detects n first radio wave intensities corresponding to n (n is an integer of 2 or more) first radio waves transmitted by the second radio apparatus, and the detection is performed. The first bit string in which the n first radio wave intensities are multi-valued or the second bit string in which a predetermined process is applied to the n first radio wave intensities to suppress a continuous arrangement of the same bit values. Generate a first secret key consisting of
The second radio apparatus detects n second radio field intensities corresponding to the n second radio waves transmitted by the first radio apparatus, and the detected n second radio field intensities are detected. Wireless communication system for generating a second secret key composed of the same bit string as the first secret key by performing the predetermined processing on the second bit string obtained by multi-valued or the n second radio wave intensities . The first antenna is an antenna capable of electrically switching directivity;
The n first radio wave intensities are received by the first wireless device from the second wireless device when the directivity of the first antenna is changed to n directivities according to a predetermined pattern. N radio field intensities corresponding to the n first radio waves
The n second radio field intensities are n received by the second wireless device from the first wireless device when the directivity of the first antenna is changed to the n directivity. The wireless communication system according to claim 1, wherein n radio field intensities corresponding to the second radio wave.   The first and second wireless devices generate predetermined first and second secret keys by performing predetermined arithmetic processing on the n first and second radio field intensities, respectively. The wireless communication system according to claim 2. The first radio apparatus includes an i (i is 1 to n) -th first radio wave intensity and an i + α (α is a positive integer) -th first radio wave in the n first radio wave intensity arrays. The intensity is selected from the n first radio field intensities, and the difference between the selected i-th and i + α-th first radio field intensities is calculated to generate n third radio field intensities. Generating the first secret key based on the n third radio field strengths,
The second radio apparatus arbitrarily selects the i-th and i + αth second radio field intensities of the n second radio field intensities from the n second radio field intensities, and selects the selected i th And the difference between the i + αth second radio field intensities is generated to generate n fourth radio field intensities, and the second secret key is generated based on the generated n fourth radio field intensities. The wireless communication system according to claim 3. The first radio apparatus includes the n pieces of the n first radio wave intensities arranged in a ring shape with the i-th first radio wave intensity and the i + 1-th first radio wave intensity in the arrangement of the n first radio wave intensities. Selecting from the first radio field intensity and subtracting the i-th first radio field intensity from the i + 1st first radio field intensity to generate the n third radio field intensities,
The second radio apparatus includes the n number of the n number of second radio wave intensities arranged in a ring shape with the i th first radio wave intensity and the i + 1 th first radio wave intensity arranged in a ring shape. 5. The n fourth radio field intensities are generated by selecting the second radio field intensity and subtracting the i th first radio field intensity from the i + 1 th first radio field intensity. Wireless communication system. The first radio apparatus subtracts the i-th first radio field intensity from the i + 1-th first radio field intensity, calculates an absolute value of the subtraction result, and calculates the n third radio field intensities. Produces
The second radio apparatus subtracts the i-th first radio field intensity from the i + 1-th first radio field intensity, calculates an absolute value of the subtraction result, and calculates the n fourth radio field intensity. The wireless communication system according to claim 5, wherein: The first wireless device determines the i (i is a positive odd number) first radio field intensity and the (i + 1) th first radio field intensity in the n first radio field intensity arrays. Select from the first radio field intensity, calculate the difference between the selected i-th and i + 1-th first radio field intensities to generate n / 2 third radio field intensities, and generate the generated n / 2 Generating the first secret key based on the third radio field intensity of
The second radio apparatus calculates the i-th second radio field intensity and the i + 1-th second radio field intensity in the n second radio field intensity arrays from the n second radio field intensities. Selecting, calculating a difference between the selected i-th and i + 1-th second radio field intensities to generate n / 2 fourth radio field intensities, and generating the generated n / 2 fourth radio field intensities. The wireless communication system according to claim 3, wherein the second secret key is generated based on the information. The first radio apparatus generates n third radio field intensities by normalizing the n first radio field intensities with a reference value, and in the array of the generated n third radio field intensities. The i (i is 1 to n) th third radio wave intensity and the i + α (α is a positive integer) th third radio wave intensity are selected from the n third radio wave intensities, and the selected i The product of the i th and i + α th third radio field intensities is generated to generate n fourth radio field intensities, and the first secret key is generated based on the generated n fourth radio field intensities And
The second radio apparatus normalizes the n second radio field intensities with the reference value to generate n fifth radio field intensities, and i in the generated n fifth radio field intensities. The fifth i-αth and i + α-th fifth radio field intensities are selected from the n fifth radio field intensities, and the product of the selected i-th and i + α-th fifth radio field intensities is calculated to obtain n sixth The wireless communication system according to claim 3, wherein a radio wave intensity is generated, and the second secret key is generated based on the generated n sixth radio wave intensities. The first radio apparatus generates n third radio field intensities by normalizing the n first radio field intensities with a reference value, and in the array of the generated n third radio field intensities. The i (i is a positive odd number) th radio wave intensity and the i + 1 th third radio wave intensity are selected from the n third radio wave intensities, and the selected i th and i + 1 th third wave intensity are selected. To generate n / 2 fourth radio field intensities, and generate the first secret key based on the generated n / 2 fourth radio field intensities,
The second radio apparatus generates n fifth radio field intensities by normalizing the n second radio field intensities with a reference value, and in the array of the generated n fifth radio field intensities. The i-th fifth radio field intensity and the (i + 1) -th fifth radio field intensity are selected from the n fifth radio field intensities, and the product of the selected i-th and i + 1-th fifth radio field intensities is obtained. 4. The radio according to claim 3, wherein n / 2 sixth radio wave intensities are generated by calculation, and the second secret key is generated based on the generated n / 2 sixth radio wave intensities. Communications system. The first wireless device further calculates an absolute value of the product to generate the n fourth radio field strengths or the n / 2 fourth radio field strengths,
The said 2nd radio | wireless apparatus further calculates the absolute value of the said product, and produces | generates the said 6th radio field intensity of the n pieces or the 6th radio field intensity of the said n / 2. 9. The wireless communication system according to 9. The first radio apparatus divides the n first radio field intensities into m (m is an integer of 2 or more) blocks, and determines m threshold values corresponding to the divided m blocks. And using the determined m thresholds to multi-value the first radio wave intensity included in the m blocks to generate the first secret key,
The second radio apparatus divides the n second radio field intensities into m blocks, determines m threshold values corresponding to the divided m blocks, and determines the determined m number of blocks. The wireless communication system according to claim 3, wherein the second secret key is generated by converting the second radio wave intensity included in the m blocks into a multi-value using a threshold value. The first radio apparatus generates n third radio field intensities by normalizing the n first radio field intensities with a reference value, and in the array of the generated n third radio field intensities. The i (i is 1 to n) th third radio wave intensity and the i + α (α is a positive integer) th third radio wave intensity are selected from the n third radio wave intensities, and the selected i The k-th power of the third radio field strength and the k power of the i-th third radio field strength are calculated, and the k-th power of the i-th third radio field strength and i + α are calculated. An n number of fourth radio field intensities are generated by calculating a difference of the kth power of the third third radio field intensity, and the first secret key is generated based on the generated n fourth radio field intensities And
The second radio apparatus generates n fifth radio field intensities by normalizing the n second radio field intensities with reference values, and in the array of the generated n fifth radio field intensities. The i-th fifth radio field intensity and the i + αth fifth radio field intensity are selected from the n fifth radio field intensities, and the selected i-th fifth radio field intensity is raised to the k-th power and i + α-th The fifth power of the fifth radio wave intensity is calculated, and the difference between the calculated kth power of the i-th fifth radio wave intensity and the kth power of the (i + α) th fifth radio wave intensity is calculated. The wireless communication system according to claim 3, wherein a radio wave intensity is generated, and the second secret key is generated based on the generated n sixth radio wave intensities.   Each of the first and second radio apparatuses includes all the bits included in the arbitrary section when the same bit value continuously exists in an arbitrary section of the first and second bit strings at a reference value or more. The wireless communication system according to claim 1 or 2, wherein the first and second secret keys are generated by deleting a value. A wireless device used in a wireless communication system that performs cryptographic communication between wireless devices,
A wireless device comprising the first wireless device or the second wireless device according to any one of claims 1 to 13.

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