JP2004187197A - Radio communication system, radio communication method and radio station - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a system constituted so that a normal transmitter/receiver individually creates a secret key in secret based on irregular fluctuation of radiowave propagation path characteristics of radio communication and the radio communication with high security is performed by using the created secret key. <P>SOLUTION: In the case of performing the radio communication by using the secret key, a signal for measurement is first transmitted from the respective radio stations 1, 2 to the other radio stations 2, 1, the signal for measurement which is transmitted from the other party and changed by the radio wave propagation path characteristics between the radio stations is received and time series of a delay profile is measured. Then, the secret keys are uniquely crated in the respective radio stations 1, 2 based on the delay profile and the communication is performed by using the shared secret keys. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to wireless communication, and more particularly to, for example, a wireless communication technique suitably used for wireless communication between mobile wireless terminals or between a mobile wireless terminal and a base station.
[0002]
[Prior art]
In recent years, with the development of the information society, information communication has become more and more important, and wiretapping and unauthorized use of information have become more serious problems. In particular, in wireless communication such as mobile communication, eavesdropping can be performed relatively easily and secretly by wireless interception, so that eavesdropping countermeasures are more important. As a countermeasure against eavesdropping, encryption and the like have been conventionally used, but there are the following problems when the existing technology is directly applied to mobile communication and the like.
[0003]
That is, among the encryption techniques, the public key cryptosystem has high security, but is not suitable for encrypting a large amount of data. In addition, since the amount of processing operation is large, it is difficult to apply the method to a mobile wireless terminal that has restrictions on power consumption and the amount of processing operation. On the other hand, a secret key cryptosystem, which is relatively easy to process, can also perform high-speed encryption of large amounts of data, but requires key management and key distribution. Further, in the secret key cryptosystem, if the same secret key is continuously used, there is a concern that a cryptanalysis attack is liable to occur and security is impaired. Further, in mobile communication, there is a problem that the risk of theft or loss of the terminal is high.
[0004]
On the other hand, secret communication can be performed using irregular phenomena such as channel noise and channel fluctuation. As a method utilizing channel noise, theoretical study of the possibility of secret key distribution using an eavesdropping channel (UM Maurer, "Secret key agreement by public discrimination from com- munication information," IEEE Transformation Information, "IEEE Transformation Information,"). vol39, no3, pp733-742, May, 1993). In addition, a method has been proposed for realizing secret communication by making use of irregular fluctuations in a mobile communication path and performing transmission control for giving a difference in error occurrence between a legitimate sender and receiver and an eavesdropper (Nakayama) Sasaoka, "Study of Security Communication System Using Channel Noise in Mobile Communication," IEICE Tech. 2002, B-5-73, March, 2002). However, these are not very simple methods.
[0005]
Also, methods for creating secret keys using noise and irregular phenomena are known.However, when using them for secret communication, there is a way to safely distribute the secret keys once created to authorized users. A means for strictly managing the key is essential. Then, a method of sharing the secret key without transmitting the secret key information between authorized senders and receivers, for example, creating a secret key individually by the authorized sender and receiver, and using the secret key in secret to an eavesdropper There is no known method of sharing a secret key by matching the secret key.
[0006]
[Problems to be solved by the invention]
The present invention focuses on such a problem. In general, in land mobile communication, a high-speed and complicated variation (multipath fading) occurs in a received electric field strength depending on radio wave propagation path characteristics. It is known that selective fading occurs when the arrival time difference (delay time difference) of multiplex waves cannot be ignored. This multipath fading is an irregular process in which the envelope distribution is generally a Rayleigh distribution, and its fluctuation speed is generally several Hz to several hundred Hz, so that the time is extremely short (for example, one second). If they are different, the fading time correlation becomes almost uncorrelated. Also, if the location is very small (about half a wavelength: 15 cm in the case of 1 GHz) at the reception of the mobile station, the fading spatial correlation becomes almost uncorrelated. It should be noted that the fading spatial correlation is almost uncorrelated at more than ten wavelengths even in the base station reception.
[0007]
On the other hand, in radio wave propagation, reversibility is established between specific transmission and reception points. That is, even if the propagation direction is reversed, the state of the propagation path between the two points (propagation path, attenuation, delay time, etc.) does not change. Therefore, when time-division duplexing is performed at the same frequency, the correlation of fading fluctuation between the signal received by the partner station and the signal received by the own station becomes stronger. For this reason, it is easy to share fading fluctuations (broadly, transmission path characteristics) between legitimate transmitters and receivers, and eavesdroppers share information on the transmission path characteristics at different receiving locations. Is almost impossible.
[0008]
Accordingly, the present invention provides a method in which an authorized sender and receiver individually create secret keys individually based on irregular fluctuations in the transmission path characteristics of wireless communication, and use the created secret keys to provide highly secure wireless communication. An object of the present invention is to provide a system capable of performing communication.
[0009]
[Means for Solving the Problems]
In order to solve the above problem, the present invention, when performing communication between wireless stations using a secret key, first, while transmitting a signal for measurement from each wireless station to another wireless station, and transmitted from the other party Receiving the measurement signal which has been changed due to the radio wave propagation path characteristics between the wireless stations. Then, based on the received measurement signal, each wireless station independently generates a secret key, and performs communication using the secret key.
[0010]
With this configuration, it is possible to create a secret key and prevent eavesdropping of the secret key in a simple manner, and if the secret key is thrown away, the terminal may be stolen or lost. Even in such a case, the secret key will not be stolen.
[0011]
Here, the “wireless station” means an apparatus, a terminal, a device, or the like that performs wireless communication using electromagnetic waves, and is, for example, a mobile terminal such as a mobile phone, a PHS (registered trademark), or a PDA. In addition, it includes those installed on the ground such as base stations. The “radio wave propagation path characteristic” is a characteristic indicating how a radio wave propagates between wireless stations. For example, “transmission path” and “attenuation”, which are unique characteristics between respective wireless stations. It includes not only natural radio wave propagation path characteristics such as "amount" and "propagation time difference" but also characteristics based on an artificially manipulated phenomenon. The “transmission path characteristic” is a characteristic indicating how a signal changes based on the radio wave propagation path characteristic. For example, the amplitude / phase of a signal depending on the radio wave propagation path characteristic and its fluctuation, transmission It includes the impulse response characteristics and the frequency characteristics of the road and their variations.
[0012]
Further, in such a system, when a secret key is generated, generation of a measurement signal, transmission processing, reception processing, and transmission path characteristics are performed so that dependence on the difference in the device characteristics of the transceiver in the wireless station is reduced. A secret key is created by performing a measurement process, a conversion process of a measured amount, and the like. Such a process may be performed for all of the generation of the measurement signal, the transmission process, the reception process, the measurement process of the transmission path characteristics, and the conversion process of the measured amount. It may be performed only for the user.
[0013]
With this configuration, the difference between the received measurement signals due to the difference in the device characteristics of the wireless stations can be reduced, and the mismatch between the secret keys can be minimized.
[0014]
Further, it receives key confirmation data irreversibly calculated based on the secret key of another wireless station, and receives the same irreversibly calculated data based on the received data and its own secret key. By confirming the match, the secret keys can be matched.
[0015]
With this configuration, even if the key confirmation data is transmitted to the partner station for matching, even if the information is eavesdropped by an eavesdropper, it cannot be returned to the secret key, The secret keys can be safely and reliably matched.
[0016]
Also, when confirming the secret key of each radio station, a syndrome calculated based on the secret key of the other radio station is received, and the syndrome calculated based on the received syndrome and the secret key of the own station is used. Perform error correction so that the secret keys match.
[0017]
With this configuration, even if the information about the syndrome is disclosed to the eavesdropper, the secret key itself is not known, and if the secret keys created by the respective radio stations are different, it is ensured. Can match their private keys.
[0018]
In the present invention, "sender" means a sender of information transmitted safely, and "recipient" means a legitimate recipient who should receive the information. "Eavesdropper" refers to an unauthorized recipient who is likely to eavesdrop, regardless of whether he or she intends to eavesdrop. The concepts of the sender, the receiver, and the eavesdropper are not limited to persons, but include automatic or manual devices having transmission, reception, and eavesdropping functions.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the present embodiment, a system for performing wireless communication with wireless stations 1 and 2 such as a mobile phone as shown in FIG. 2 will be described. In FIG. 2, 1 and 2 indicate authorized senders and receivers, and 3 indicates an eavesdropper.
[0020]
Radio stations 1 and 2 according to the present embodiment include a transmitting unit that transmits a measurement signal, and radio wave propagation path characteristics transmitted between radio stations 1 and 2 by the transmitting unit, that is, radio waves existing between radio stations. Receiving means for receiving a measurement signal that has changed due to the arrangement characteristics of all features, such as reflectors, scatterers, shields, and absorbers, and their radio characteristics, and a secret key based on the received measurement signal Key creation means for creating a secret key, and key confirmation means for confirming whether or not the created secret key matches. If the match of the secret key cannot be confirmed, error correction or the like is performed to achieve consistency. And a key matching unit, and encrypts and decrypts the signal using the matched secret key to perform communication. Hereinafter, the flows of the wireless stations 1 and 2 and the system in the present embodiment will be described in detail.
[0021]
FIG. 3 shows functional blocks of the wireless stations 1 and 2. FIG. 3 particularly shows functional blocks related to secret key sharing and secret communication.
[0022]
In FIG. 3, the radio stations 1 and 2 include at least a measurement signal generation unit 10, a transmission processing unit 11, an antenna unit 12, a reception processing unit 13, a transmission path characteristic measurement unit 14, a key creation unit 15, and a key agreement check unit 16. , A key matching unit 17 and a key storage unit 18. These cooperate to form a transmitting unit, a receiving unit, a key creating unit, a key checking unit, and a key matching unit.
[0023]
The measurement signal generator 10 generates a predetermined common measurement signal, and transmits the same to the other party via the transmission processor 11 and the antenna 12. Here, as the measurement signal, a communication signal can be used in addition to a case where a special signal is separately generated. The transmission processing unit 11 has a transmission system process such as modulation, frequency conversion, multiple access, and transmission signal amplification. The reception processing unit 13 performs a reception process of a signal transmitted from the other party via the antenna unit 12, and performs processes such as reception amplification, multiple access, frequency conversion, and demodulation. The transmission path characteristic measuring section 14 examines the transmission path characteristics of the received signal and transfers it to the key generation section 15. The key creation unit 15 converts the transmission path characteristics so as to be suitable for creation of a secret key, and then digitizes it to create a secret key represented by bit information. The key agreement confirmation unit 16 includes a key confirmation data generation unit 16a, a key confirmation data comparison unit 16b, and a result processing unit 16c as shown in FIG. The key confirmation data transmitted to the other party via the processing unit 11 and the antenna unit 12 or the data for key confirmation received from the other party created by the key confirmation data generation unit 16a of the own station is compared by the key confirmation data comparison unit 16b. Then, the result is transmitted to the key storage unit 18, the transmission processing unit 11, and the like. As shown in FIG. 5, the key matching unit 17 includes a pseudo syndrome creation unit 17a, a mismatch bit detection unit 17b, a key mismatch correction unit 17c, a confirmation data generation unit 17d, a key confirmation data comparison unit 17e, and a result processing unit 17f. In the case where a mismatch is confirmed by the key matching confirmation unit 16, the secret key is matched using the pseudo syndrome, and the matched secret key is processed in the same manner as the process of the key matching checking unit 16. Is converted to key confirmation data, and a match is confirmed. The key storage unit 18 temporarily stores the secret key whose matching has been confirmed by the key matching checking unit 16 or the secret key subjected to the matching process by the key matching unit 17. For example, during one communication, The information is stored. On the other hand, after confirming that the secret keys match, the encryption unit 19a encrypts the transmission data using the secret key so that the transmission data can be transmitted to the other party via the transmission processing unit 11 and the antenna unit 12. Conversely, the decryption unit 19b decrypts the encrypted data received via the antenna unit 12 and the reception processing unit 13 with a secret key, and outputs the decrypted data as received data.
[0024]
Next, a flow in the case where the wireless stations 1 and 2 configured as described above perform secret communication will be described with reference to FIG.
[0025]
(Measurement of measurement signal transmission / reception and transmission path characteristic fluctuation)
First, when the wireless stations 1 and 2 perform confidential communication, a common measurement signal is transmitted from each of the wireless stations 1 and 2 (step S1), and the measurement signals that have been changed based on the radio wave propagation path characteristics are transmitted to each other. Upon reception (step S2), the fluctuation of the transmission path characteristics is measured (step S3). When wireless communication is performed, the propagation path portion is common, but the transmission and reception portions of the wireless stations 1 and 2 are generally not common, so that the measurement signal and the measurement result of the transmission path characteristic are based on the device characteristics. An error occurs. In addition, the reversibility of the propagation path cannot be established unless the radio waves are strictly of the same frequency. Therefore, the same transmission frequency is used in both wireless stations 1 and 2. In this case, if radio waves of the same frequency are transmitted at the same time, interference occurs. Therefore, the measurement signal is transmitted by time division duplex (TDD). Further, in the antenna unit 12, when the transmitting antenna and the receiving antenna are different, the transmitting and receiving antenna characteristics are different, and an error occurs in the measurement result of the transmission path characteristic. . In addition, if there is a change in the signal output level in the transmission processing unit 11 or a change in the input / output signal amplification factor in the reception processing unit 13, an error in the measurement of the transmission path characteristics will occur. Is added. Furthermore, when frequency conversion is performed in the transmission processing unit 11 or the reception processing unit 13, the same local oscillator is used for transmission and reception as necessary, since frequency fluctuations and phase fluctuations of the local oscillator cause errors in the measurement of transmission line characteristics. I do.
[0026]
Further, in order to generate a secret key by further converting to a measurement amount that is less dependent on differences in device characteristics, it is important to select a measurement signal together with conversion of transmission line characteristics. The measurement signal includes a continuous wave (CW wave) for measuring amplitude and phase fluctuations of a transmission signal, a spread spectrum (SS) signal for measuring a delay profile, a sweep signal for measuring frequency characteristics of a transmission line, and a frequency of a transmission line. An OFDM signal whose characteristics can be measured can be used. When a CW wave is used as a measurement signal, the CW waves received by both radio stations are affected by a reception amplitude deviation depending on amplification characteristics of both transceivers and a phase deviation due to a phase fluctuation of a local oscillator. . Therefore, the relative value of the amplitude of the received CW wave is used. On the other hand, in the measurement of the delay profile, in addition to being affected by the reception amplitude deviation and the phase deviation, a power delay profile represented by a relative value is used. Also, if the reference time for measuring the delay is shifted between the two wireless stations, the power delay profile characteristics will be different, so that it is necessary to convert the measured amount into a measured amount that is not related to the time shift. As one of the methods, it is conceivable to obtain a spectrum of a power delay profile. As for the measurement of the frequency characteristic of the transmission path, the relative value of the amplitude frequency characteristic not including the phase component is obtained.
[0027]
Further, in the measurement of the transmission path characteristics, the cause of an error due to the fact that the conditions are not common between the two wireless stations 1 and 2 is a difference in interference and noise applied to the receiving side and a difference in measurement time. In order to reduce the influence of the difference between interference and noise, a method of transmitting the measurement signal a plurality of times, performing synchronous addition on the receiving side, and suppressing interference and noise on the signal is used. If the difference in the measurement time cannot be ignored with respect to the time change of the radio wave propagation path characteristics, the two radio stations measure each other temporally and correct the time difference by interpolating the characteristics at different times. Use a method.
[0028]
The measured value of the fluctuation of the transmission line characteristic transmitted and received in this way is used for the secret key generation in step S4.
[0029]
(Private key creation)
When a secret key is created from shared transmission path characteristics, sampling, quantization, and encoding are performed by some method, and analog information is converted to digital information. Here, it is necessary to prevent a slight difference between the transmission line characteristics measured by both wireless stations from causing a large mismatch between the secret keys.
[0030]
(Confirm key match)
It is confirmed whether the secret key created in step S4 is the same between the respective wireless stations (step S5). As a method of this confirmation, first, one radio station 2 generates key confirmation data based on the created secret key. This data is converted from the secret key by an irreversible operation or a one-way operation, and includes, for example, hashing. By using such a conversion, even if the key confirmation data is eavesdropped, the risk of decrypting the secret key information is extremely low. On the other hand, the wireless station 1 that has received the key confirmation data similarly creates the key confirmation data by performing the same irreversible operation or one-way operation on the secret key created by itself. Confirm the match between the data and the transmitted key confirmation data. If the two data do not match, it is known that the secret keys created by both parties do not match.On the other hand, if they do match, the secret keys also have a very high probability of matching, so the secret keys match. Then, the other station is notified of the coincidence, and the secret key is stored in the key storage unit 18.
[0031]
(Key mismatch measure)
If it is determined in step S5 that the two pieces of confirmation data do not match, information on the fact is notified to another station so that error correction can be performed (step S6). In this error correction, the mismatch between the secret keys is regarded as an error, and the mismatch between the keys is eliminated by applying error correction. In this method, for the sake of convenience, it is assumed that a certain block encoding is performed on the bit pattern of the secret key and an error is added. Then, both bit patterns x ₁ , X ₂ Is multiplied by the check matrix H, and the syndrome s ₁ = X ₁ H ^T , S ₂ = X ₂ H ^T Is calculated. These calculations are mod2 calculations. In the wireless station 1 that corrects the key mismatch, the syndrome s from the other wireless station 2 ₂ Received, and the syndrome s calculated by the own station ₁ Difference s = s ₁ -S ₂ Ask for. Difference of bit pattern of secret key (bit pattern of non-matching key) e = x ₁ -X ₂ Then s = eH ^T In a relationship. Here, when s = 0, it can be determined that e = 0, that is, there is no key mismatch. When s is not 0, e that satisfies the minimum number of mismatches can be estimated from s by the error correction decoding technique. Here, if the number of bits in which the keys do not match is within the error correction capability, the correction is correctly performed. In this way, when the key mismatch bit pattern e is obtained, the secret key x ₁ From the other party's secret key x ₂ = X ₁ -E is obtained. Even if the syndrome information is eavesdropped, the bit pattern of the information is not immediately guessed unless a special encoding is assumed. Further, in this method, if the number of bits of the key mismatch does not exceed the error correction capability, the key matching may fail. Therefore, it is desirable to separately confirm the key matching. For this reason, for the key after the key mismatch correction, the key confirmation data of the own station is created in the same manner as in step S5, and the key confirmation data received from another station is compared with the key confirmation data. Check and notify the other party. If the comparison of the key confirmation data does not match, there is a high possibility that the number of bits of the key mismatch does not exceed the error correction capability, so it is preferable to return to step 1 and re-create the secret key.
[0032]
(Communication with secret key)
When the matching of the secret keys is thus confirmed, the transmission data is encrypted using the secret key, and the received data is decrypted and output as the received data (step S7).
[0033]
As described above, in the above embodiment, the secret key is created using the transmission path characteristic shared between the wireless stations, so that it becomes impossible for an eavesdropper to create this secret key in another place. , The risk of eavesdropping can be reduced. Further, in this embodiment, each of the radio stations 1 and 2 performs a measurement signal, transmission processing, reception processing, transmission / reception processing including transmission path characteristic measurement, and the like so as to reduce the influence of device characteristics. Therefore, the mismatch of the secret keys to be created can be reduced as much as possible. Further, in the present embodiment, key confirmation data is transmitted by performing hashing or the like to confirm the coincidence of the secret keys, and when both data do not match, error correction is performed. Therefore, the secret keys can be safely and reliably matched.
[0034]
The present invention is not limited to the above embodiment, but can be implemented in various modes.
[0035]
For example, in the above-described embodiment, a natural radio wave propagation path characteristic between wireless stations is used as the radio wave propagation path characteristic. However, the present invention is not limited to this, and an artificially operated radio wave propagation path characteristic may be used. You may do it. As this method, as shown in FIG. 6, an artificial moving object or a fluctuating object is installed between the radio stations, a means for giving an irregular movement or fluctuation, an electromagnetic characteristic without using the movement or fluctuation of the object. There are means to artificially change. As a device for changing the electromagnetic characteristics, there is a device in which an antenna is installed between wireless stations and the equivalent length of the antenna is electrically changed to control the reflectance and absorptance of radio waves. As another means, there is a means for adding a radio wave propagation path characteristic fluctuation generating unit to both or one of the radio stations. Here, there are transmission diversity from a plurality of antennas and a transmission adaptive array as those that cause a change in radio wave propagation characteristics. The irregular fluctuation of the radio wave propagation path characteristic can be generated by irregularly changing the complex weight (amplitude and phase) of the antenna. A case where it is preferable to use such an artificial radio wave propagation characteristic is, for example, a case where there is no movement of the radio station and no moving object between the radio stations, and a time change of the radio wave propagation path characteristic hardly occurs. Is the case.
[0036]
Further, in the above embodiment, error correction by syndrome is performed as a countermeasure for key mismatch. However, the present invention is not limited to this, and a plurality of secret key candidates are created in advance on the wireless station receiving key confirmation data. Alternatively, the secret keys may be matched using these.
[0037]
Note that, in the relationship between the present invention and the above embodiment,
The transmission means corresponds to the measurement signal generation unit 10, the transmission processing unit 11, and the antenna unit 12,
The receiving means corresponds to the antenna unit 12 and the reception processing unit 13,
The key generation means corresponds to the transmission line characteristic measurement unit 14 and the key generation unit 15,
The key confirmation means corresponds to the key agreement confirmation unit 16,
The key matching means corresponds to the key matching unit 17,
The communication unit corresponds to the encryption unit 19a, the transmission processing unit 11, the antenna unit 12, the reception processing unit 13, and the decryption unit 19b.
[0038]
【Example】
Based on the above embodiment, the results of actual evaluation of characteristics using computer simulation are shown.
[0039]
In this simulation, a legitimate sender / receiver uses TDD and has a function of measuring a delay profile. As the system specifications, SS modulation to which TDMA / TDD was applied as shown in FIG. 8 was assumed. As shown in FIG. 7, the secret key generation procedure first transmits and receives the SS modulated wave, which is a signal for delay profile measurement, performs synchronous addition on the receiving side, and measures the time series of the delay profile as the transmission path characteristics. I do. Further, the influence of the measurement time difference of the delay profile is removed by interpolation at one of the wireless stations. Thereafter, the time series of the delay profile is Fourier-transformed to obtain a time-varying frequency characteristic of the transmission path, sampled in the time / frequency domain, and binarized to obtain a key candidate as a bit pattern. Further, a key mismatch measure is taken, and normal key sharing is confirmed. After that, encryption / decryption is performed using the shared secret key.
[0040]
The results are shown in FIGS. FIG. 9 is an example of a power delay profile. The measurement results for the sender, receiver, and eavesdropper are all different, but when the time difference is corrected for the measurement result of the legitimate sender and receiver, the result is the same, whereas the eavesdropper measures the shape. Quite different. FIG. 10 shows a result of measuring such a time change of the power delay profile and obtaining a time-varying amplitude frequency characteristic. The bit pattern of (0, 1) created by performing eight-time determination of this time-varying amplitude frequency characteristic and twelve samples in the time axis direction and performing a binary determination using an average value of 96 sample values as a threshold value is illustrated. 11 is shown. The bit patterns of the two match, indicating that the secret key can be shared.
[0041]
Next, a description will be given of the rate of occurrence of key mismatch and the effect of the key mismatch countermeasure when the measurement of the transmission path characteristics is not ideal. FIG. 12 shows the deterioration due to the measurement time difference and the improvement effect by interpolation. It can be seen that the key mismatch rate can be reduced by linear interpolation or cubic interpolation. FIG. 13 shows a noise reduction effect by synchronous addition. FIG. 14 shows the effect of a key mismatch measure using error correction decoding. It can be seen that the key mismatch rate is almost zero when the signal-to-noise power ratio (SN ratio) is about 20 dB.
[0042]
【The invention's effect】
According to the present invention, when communication is performed between wireless stations using a secret key, first, a measurement signal is transmitted from each wireless station to another wireless station, and the measurement signal transmitted from the other The measurement signal changed by the radio wave propagation path characteristic between the stations is received. Then, based on the received measurement signal, each wireless station independently creates a secret key, and performs communication using the created secret key. It is possible to prevent the secret key from being stolen.
[Brief description of the drawings]
FIG. 1 is a flowchart showing a state of wireless communication according to an embodiment;
FIG. 2 is a schematic diagram of a system in the embodiment.
FIG. 3 is a functional block diagram of a wireless station according to the embodiment;
FIG. 4 is a detailed block diagram of a key matching check unit in the embodiment.
FIG. 5 is a detailed block diagram of a key matching unit in the embodiment.
FIG. 6 is a schematic diagram of a system according to another embodiment.
FIG. 7 is a diagram showing a simulation flow in the embodiment.
FIG. 8 is a diagram showing specifications of a simulation system.
FIG. 9 is a diagram showing a power delay profile in a simulation.
FIG. 10 is a diagram illustrating a time-varying amplitude frequency characteristic (absolute value) of a transmission line in a simulation.
FIG. 11 is a diagram showing a bit pattern created in a simulation;
FIG. 12 is a diagram showing an improvement effect by interpolation of a key mismatch characteristic in a simulation;
FIG. 13 is a diagram showing an improvement effect of a key addition characteristic in a simulation by synchronous addition;
FIG. 14 is a diagram showing a key mismatch characteristic when error correction decoding is applied in a simulation;
[Explanation of symbols]
1, 2, ... wireless station
3 ... Eavesdropper
10 ... Measurement signal generator
11 ... Transmission processing unit
12 ... antenna
13 ... Reception processing unit
14 ... Transmission line characteristic measuring unit
15 ... key creation unit
16 ... Key agreement check section
17 ... Key matching unit
18 Key storage unit
19a: encryption unit
19b: decoding unit

Claims (18)

In a wireless communication system for performing communication between wireless stations using a secret key, a transmitting unit for transmitting a measurement signal to another wireless station to each wireless station, and a wireless station transmitted from another wireless station, Receiving means for receiving a measurement signal that has changed between, a key creation means for creating a secret key based on the received measurement signal; and encrypting and decrypting the signal using the created secret key. A wireless communication system, comprising: communication means for performing communication. The wireless communication system according to claim 1, wherein the measurement signal that has changed between the wireless stations is a measurement signal that has changed due to radio wave propagation characteristics between the wireless stations. 2. The wireless communication system according to claim 1, wherein the measurement signal changed between the wireless stations is a measurement signal changed due to a radio wave propagation path characteristic between the artificially operated wireless stations. In a wireless communication method for performing communication between wireless stations using a secret key, transmitting a measurement signal from each wireless station to each other, and transmitting a measurement signal transmitted from another wireless station and changed between wireless stations. Receiving, generating a secret key in each radio station based on the received measurement signal, encrypting the signal using the generated secret key, decrypting and communicating, A wireless communication method comprising: The wireless communication method according to claim 4, wherein the measurement signal changed between the wireless stations is a measurement signal changed due to a radio wave propagation path characteristic between the wireless stations. 5. The wireless communication method according to claim 4, wherein the measurement signal changed between the wireless stations is a measurement signal changed due to radio wave propagation characteristics between artificially operated wireless stations. In a wireless station that performs communication with another wireless station using a secret key, a transmitting unit that transmits a measurement signal for generating a secret key to the other wireless station, the other wireless station Receiving means for receiving a measurement signal that has been changed between wireless stations, a key creation means for creating a secret key based on the received measurement signal, and a signal using the created secret key. And a communication means for performing communication by encrypting, decrypting and communicating. The secret key is obtained by performing processing including at least one of generation of a measurement signal, transmission processing, reception processing, and transmission path characteristic measurement so as to reduce dependence on the device characteristic difference between the two radio stations. The wireless station according to claim 7, wherein the secret key is created by converting the created measurement signal and / or the received measurement signal into a measurement quantity that is less dependent on a difference in device characteristics. Further, receiving key confirmation data irreversibly calculated based on the secret key of the other wireless station, and confirming the key confirmation irreversibly calculated based on the received data and the secret key of the own station. 9. The wireless station according to claim 7, further comprising key confirmation means for confirming the coincidence of the secret keys by confirming the coincidence of the data for use. Furthermore, a syndrome calculated based on the secret key of the other wireless station is received, error correction is performed using the received syndrome and a syndrome calculated based on the secret key of the own station, and the secret key is matched. The wireless station according to claim 7, further comprising a key matching unit configured to perform key matching. The radio station according to any one of claims 7 to 10, wherein the measurement signal that has changed between the radio stations is a measurement signal that has changed due to radio wave propagation characteristics between the radio stations. The wireless station according to any one of claims 7 to 10, wherein the measurement signal that has changed between the wireless stations is a measurement signal that has changed due to radio wave propagation characteristics between artificially operated wireless stations. In a wireless communication method for performing communication with another wireless station using a secret key, a step of transmitting a measurement signal for generating a secret key to the other wireless station; Is transmitted from the step of receiving a measurement signal changed between wireless stations, a step of creating a secret key based on the received measurement signal, and encrypting the signal using the created secret key, Performing wireless communication by decoding. The secret key is obtained by performing processing including at least one of generation of a measurement signal, transmission processing, reception processing, and transmission path characteristic measurement so as to reduce dependence on the device characteristic difference between the two radio stations. 14. The wireless communication method according to claim 13, wherein the secret key is created by converting the created measurement signal and / or the received measurement signal into a measurement quantity that is less dependent on a difference in device characteristics. Further, receiving key confirmation data irreversibly calculated based on the secret key of the other wireless station, and confirming the key confirmation irreversibly calculated based on the received data and the secret key of the own station. 15. The wireless communication method according to claim 13, further comprising the step of confirming a match of a secret key by confirming a match of data for use. Furthermore, a syndrome calculated based on the secret key of the other wireless station is received, error correction is performed using the received syndrome and a syndrome calculated based on the secret key of the own station, and the secret key is matched. The wireless communication method according to any one of claims 13 to 15, further comprising a step of causing the wireless communication. 17. The wireless communication method according to claim 13, wherein the measurement signal that has changed between the wireless stations is a measurement signal that has changed due to radio wave propagation characteristics between the wireless stations. 17. The wireless communication method according to claim 13, wherein the measurement signal that has changed between the wireless stations is a measurement signal that has changed due to a radio wave propagation path characteristic between the wireless stations that have been artificially operated.

Images