JP2010016559A - Encryption communication system, reception device, and transmission device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an encryption communication system which is capable of limiting reception objects when transmitting/receiving information. <P>SOLUTION: A speed of a preceding vehicle is calculated (S110). A latitude and a longitude as a present position of a user's vehicle are calculated on the basis of information obtained from a GPS receiver 11a (S120). The latitude and the longitude are corrected on the basis of information obtained from a gyroscope 11b or the like (S130). A traffic congestion level is estimated on the basis of the speed of the preceding vehicle (S140). A region wherein decryption is permitted is determined in accordance with the position of the user's vehicle and the traffic congestion level (S150). An encryption key for a decryption key determined by two pairs of latitudes and longitudes as boundary lines of the region is generated (S160). Traffic congestion information is encrypted into a ciphertext by the generated encryption key (S170). The ciphertext, the numbers of blocks in the direction from south to north and the direction from east to west, and an offset value are transmitted (S180). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an encryption communication system for transmitting ciphertexts by a common key cryptosystem from a transmission device to a reception device, and a transmission device and a reception device used in the encryption communication system.

In a vehicle-to-vehicle communication device, a technique for acquiring a traveling direction of a host vehicle using a GPS receiver and selecting a communication channel to be used for transmitting a radio signal based on the traveling direction is already known (for example, a patent) Reference 1). According to this technique, it is possible to communicate with a vehicle that is likely to collide with an intersection at an intersection or the like by selecting a communication channel, and processing for collision avoidance can be executed.
JP 2004-62381 A

  The problem of the technology described above is that although communication with a vehicle satisfying a specific condition can be selectively performed by selecting a communication channel, communication with a vehicle located at a specific location cannot be performed selectively. In other words, with the above-described technology, any vehicle can receive and acquire information as long as the communication direction and the radio wave intensity match. Therefore, with this type of conventionally known technology, information related to privacy cannot be transmitted in a dark manner.

  Another problem is that, depending on the type of information, it may be useful only for a user located in a specific location, but the technology known in the art is limited to vehicles located in a specific location. The information that is useful cannot be transmitted. That is, in the conventionally known technique, a large amount of unnecessary information flows from the transmission side to the reception side, and thus there is a problem that selection of reception information in the reception side vehicle is complicated.

  For example, information on traffic jams is not necessary for users of vehicles who are unlikely to be involved in the traffic jams. Therefore, information may be transmitted only to vehicles that are or are likely to be involved in a traffic jam. However, the above-described technique cannot solve this problem because the communication channel cannot be selected based on information other than the traveling direction.

  In view of the above-described problems, an object of the present invention is to provide a technique that enables a transmission side to transmit information toward a specific area when transmitting and receiving information.

  The invention according to claim 1, which has been made in order to solve the above-described problem, is a cryptographic communication system that transmits ciphertext by a common key cryptosystem from a transmitting device to a receiving device. The transmission apparatus includes a determination unit, an encryption key generation unit, a plaintext acquisition unit, an encryption unit, and a transmission unit.

  The determining means determines a region where ciphertext decryption is permitted as a ciphertext destination. The encryption key creation means creates an encryption key based on the location information of the area determined by the determination means. The plaintext acquisition unit acquires the plaintext to be transmitted. The encryption means creates the ciphertext by encrypting the plaintext acquired by the plaintext acquisition means with the encryption key created by the encryption key creation means. The transmission means transmits the ciphertext created by the encryption means to the surroundings in the form of electromagnetic waves.

On the other hand, the receiving device includes a receiving unit, a position acquisition unit, a decryption key creation unit, and a decryption unit.
The receiving unit receives the ciphertext transmitted from the transmitting unit. The position acquisition means acquires its own position information. The decryption key creation means creates a decryption key based on the position information acquired by the position acquisition means. The decrypting means decrypts the ciphertext received by the receiving means with the decryption key created by the decryption key creating means.

  According to the encryption communication system of the first aspect, the transmission device can transmit information toward a specific area. This is because, by creating the encryption key and the decryption key by the above-described method, only the reception device located in the area determined by the determination unit included in the transmission device can correctly decrypt the ciphertext.

  That is, according to the present invention, a ciphertext is transmitted to surroundings by radio waves or the like, but the ciphertext is not decrypted by a receiving device at an unintended position, and is selected for a receiving device at a specific location In addition to being able to transmit data, it is possible to safely exchange data with high privacy while preventing information leakage.

  A receiving apparatus according to a second aspect is a receiving apparatus constituting the cryptographic communication system according to the first aspect. According to this receiving apparatus, the above-described cryptographic communication system can be constructed, and the above-described effects can be obtained.

  The receiving device according to claim 3 is the receiving device according to claim 2 mounted on a moving body. In this receiving device, the position acquisition means includes positioning means, acceleration measurement means, and correction means.

  The positioning means measures the current position based on the GPS signal transmitted from the GPS satellite. The acceleration measuring unit measures the acceleration of the receiving device. The correcting unit corrects the current position measured by the positioning unit based on the information on the acceleration measured by the acceleration measuring unit.

  Then, the position acquisition means acquires the current position after correction by the correction means as its own position information, and the decryption key creation means creates a decryption key based on the current position after correction by the correction means.

According to the receiving apparatus of the third aspect, it is possible to accurately acquire its own position. Therefore, it is possible to accurately know whether or not it is located at the position determined by the determining means of the transmission apparatus.
A transmission device according to a fourth aspect is a transmission device constituting the cryptographic communication system according to the first aspect. According to this transmission apparatus, the above-described cryptographic communication system can be constructed, and the above-described effects can be obtained.

  By the way, the transmission device according to claim 4 may be configured as described in claim 5. The determining unit included in the transmission device according to claim 5 is configured to select an area from which the decryption of the ciphertext is permitted by selecting an arbitrary section from among a plurality of sections predetermined as a transmission target area by the transmitting unit. decide.

  According to the transmission device of the fifth aspect, the probability that the reception device can decrypt with the decryption key created based on its own position is increased. This is because if the transmitting device and the receiving device do not share the information on how the permitted position determined by the determining means is a divided area, the brute force attack must be relied upon for decoding. . Therefore, if the method of dividing the region is expressed by a plurality of predetermined sections and is shared between the transmitting device and the receiving device, the probability that a correct decryption key can be created will be significantly higher than the brute force attack. .

  The transmission device according to claim 4 or 5 may be configured as described in claim 6. According to a sixth aspect of the present invention, there is provided a transmission apparatus including a position acquisition unit that acquires its own position information. Then, the determining means determines an area where the decryption of the ciphertext is permitted based on the position information acquired by the position acquiring means.

  According to the transmission apparatus of the sixth aspect, the area based on the position of the transmission apparatus itself can be determined as the area where decoding is permitted. In other words, if the user's own position is not known, the area where decoding is permitted must be determined based on criteria that are not related to the position such as latitude and longitude. However, if its own position is known, it is possible to determine a region where decoding is permitted, such as a region far from itself. Therefore, for example, information having utility value for a receiving device only around the transmitting device can be transmitted to the receiving device.

  The transmission device according to claim 6 may be configured specifically as described in claim 7. The transmission device according to claim 7 is the transmission device according to claim 6, which is mounted on a moving body, wherein the position acquisition means includes positioning means, acceleration measurement means, and correction means. .

  The positioning means measures the current position based on the GPS signal transmitted from the GPS satellite. The acceleration measuring unit measures acceleration generated in the transmission device. The correcting unit corrects the current position measured by the positioning unit based on the information on the acceleration measured by the acceleration measuring unit.

  The position acquisition means acquires the current position after correction corrected by the correction means as its own position information, and the determination means permits decryption of the ciphertext based on the current position corrected by the correction means. Decide where to go.

  According to the transmission device of claim 7, it is possible to determine a region where decoding is permitted based on accurate information on the own position, for example, receiving information useful for the reception device only around the transmission device. When transmitting to the apparatus, it is possible to appropriately determine the transmission region (region where decoding is permitted).

  The transmission apparatus according to claim 6 or 7 may be configured as described in claim 8. A transmission device according to an eighth aspect is mounted on a vehicle as a moving body. The transmission device includes a speed measurement unit and an estimation unit. The speed measuring means measures the speed of other vehicles around the host vehicle. The estimating means estimates the degree of congestion around the host vehicle based on the measurement result of the speed measuring means. And a plaintext acquisition means acquires the information of the traffic congestion degree estimated by the estimation means as plaintext.

  According to the transmission device of the eighth aspect, it is possible to encrypt the degree of congestion around the host vehicle and transmit it to the periphery of the host vehicle. Therefore, if the receiving device is also provided in the vehicle, the receiving device can obtain information on the degree of traffic congestion around the host vehicle, so that the information on the degree of traffic congestion can be transmitted / received only in areas with high utility value. .

  The transmission device according to claim 8 may be configured as described in claim 9. The determining unit included in the transmission device according to claim 9 determines an area where the decryption of the ciphertext is permitted so that the area where the decryption of the ciphertext is permitted increases as the congestion degree estimated by the estimation unit increases. To do.

  According to the transmission apparatus of Claim 9, the congestion degree around the own vehicle can be transmitted to an appropriate area. This is because, in general, the higher the degree of congestion, the more valuable the vehicle is in a wide area.

  The transmission device according to any one of claims 4 to 7 may be configured as described in claim 10. The plaintext acquisition means provided in the transmission device according to claim 10 acquires the plaintext through the user interface.

  According to the transmission device of the tenth aspect, since it is not necessary to generate plaintext by itself, the device can be configured simply and inexpensively. Moreover, since the information is obtained from the user interface, the information that the user desires to transmit can be acquired as plain text, encrypted, and transmitted while maintaining privacy.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic configuration diagram of a cryptographic communication system 1 to which the present invention is applied. The cryptographic communication system 1 includes a plurality of in-vehicle devices 10, a plurality of road infrastructures 30 configured to be capable of wireless communication with the in-vehicle devices 10, and an information center 50 configured to be capable of wired communication with the road infrastructure 30. The in-vehicle device 10 is used by being mounted on a four-wheel or two-wheel automobile. The road infrastructure 30 is installed on the road side.

  That is, in the encryption communication system 1, wireless communication is performed between the in-vehicle devices 10 and between the in-vehicle device 10 and the road infrastructure 30, and between the road infrastructure 30 and the information center 50 by wire. Communication takes place. With such a communication mode, the in-vehicle device 10 and the information center 50 can communicate with each other via the road infrastructure 30.

FIG. 2 is a block diagram illustrating the configurations of the in-vehicle device 10, the plurality of road infrastructures 30, and the information center 50.
The in-vehicle device 10 includes a positioning device 11 that measures the current position of the vehicle, an operation switch group 12 that functions as a user interface, a voice input unit 13 that receives voice input, and an external information input / output device 16 that exchanges information with an external device. A map data input device 17 for reading out map data and the like from the storage medium and inputting them to the control unit 20, a display unit 14 for displaying a map, a route guidance screen, etc., a voice output unit 15 for outputting various guide voices, A radar 19 for measuring a distance to the vehicle ahead of the host vehicle and a control unit 20 are provided.

  The positioning device 11 receives a transmission radio wave (GPS signal) from an artificial satellite for GPS (Global Positioning System) via a GPS antenna, and measures a position, a traveling direction, and the like of the vehicle, and a vehicle A gyroscope 11b for measuring the magnitude of the rotational motion generated in the vehicle, a distance sensor 11c for measuring the travel distance of the vehicle from the number of rotations of the wheels, and a geomagnetic sensor 11d for measuring the traveling direction from the geomagnetism.

The operation switch group 12 includes a touch panel configured integrally with the display unit 14 and mechanical key switches provided around the display unit 14.
The voice input unit 13 is composed of a microphone so that voice information emitted by the user can be acquired.

The display unit 14 is a color display device and includes a liquid crystal monitor or the like. A map around the current location of the vehicle is displayed on the display unit 14 under the control of the control unit 20.
The audio output unit 15 includes a speaker or the like, and outputs information received via the external information input / output device 16 as sound under the control of the control unit 20.

The external information input / output device 16 is configured to be able to wirelessly communicate with the surrounding in-vehicle device 10 and the road infrastructure 30 and functions as a wireless communication interface.
The map data input device 17 reads map data and the like stored in a storage medium (not shown) from the recording medium, and inputs this to the control unit 20. The storage medium stores road connection data (link and node data), terrain data, facility data, etc. as map data, as well as map matching data for improving positioning accuracy and route guidance. Audio data, speed limit information for each road, and the like are stored. The storage medium is a CD-ROM, DVD, hard disk, or the like.

  The radar 19 is configured to emit a millimeter wave toward the front of the vehicle, receive the reflected wave, and input the received information to the control unit 20 in accordance with a command from the control unit 20. With this configuration, in the in-vehicle device 10, the control unit 20 can measure the distance to the preceding vehicle.

  The control unit 20 includes a CPU 20a, a RAM 20b, a ROM 20c, an NVRAM 20d for storing various setting information, and the like. The CPU 20a executes various programs stored in the ROM 20c so that each unit in the apparatus can be controlled. In addition to overall control, various functions are realized.

  Specific examples of the various functions include a vehicle location specifying function, a map display function, a route guidance function, and the like. That is, the control unit 20 calculates the current location of the vehicle as a set of position coordinates (latitude / longitude) and traveling direction based on various signals input from the positioning device 11. Based on the calculation result, map data around the current location of the vehicle is acquired from the map data input device 17, and a map around the current location of the vehicle is displayed on the display unit 14 based on the map data.

  Further, the control unit 20 receives a route guidance command from the user through the operation switch group 12, the voice input unit 13, and the like. Then, the optimum route from the point where the vehicle is located at the time of command input to the destination specified by this command is calculated using a known technique such as the Dijkstra method. Then, this route guidance is performed through the display unit 14 and the voice output unit 15.

In addition, the control part 20 implement | achieves an encryption communication function by performing the process regarding encryption communication (it mentions later in detail).
On the other hand, the road infrastructure 30 is a communication device including a processing unit 31, a communication unit 34, and an I / F (interface) 35. The processing unit 31 is configured as a well-known microcomputer and executes processing related to cryptographic communication (details will be described later). The communication unit 34 is configured as a wireless communication interface capable of wireless communication with the external information input / output device 16, and transmits / receives information to / from the external information input / output device 16 wirelessly in accordance with instructions from the processing unit 31. Then, the processing unit 31 performs wired communication with the information center 50 via the I / F 35.

  The information center 50 includes a processing unit 51, an operation switch group 52, and an I / F 55. The processing unit 51 is configured as a well-known microcomputer and executes processing related to cryptographic communication (details will be described later). The processing unit 51 is configured to be able to transmit and receive information to and from the processing unit 31 via a wire via the I / F 55 and the I / F 35. The operation switch group 52 functions as a user interface and is used to input information to the processing unit 51.

  From here, processing related to cryptographic communication will be described. In the present embodiment, encrypted communication is realized by the first transmission process executed by the control unit 20 and the reception process executed by the control unit 20 and the processing unit 31. That is, the information (ciphertext) encrypted by the first transmission process is transmitted, and the received ciphertext is decrypted by the reception process. First, the first transmission process will be described.

  FIG. 3 is a flowchart showing the first transmission process. The first transmission process is repeatedly executed mainly by the control unit 20 included in the in-vehicle device 10. The first transmission process is executed by the control unit 20 in order to transmit the information related to the encrypted traffic jam to the road infrastructure 30 and the in-vehicle device 10 of another vehicle.

  First, the control unit 20 calculates the speed of the preceding vehicle based on the information on the distance to the preceding vehicle obtained from the radar 19 (S110). Specifically, the relative speed with respect to the own vehicle is calculated by differentiating the distance to the preceding vehicle with time, and the speed of the preceding vehicle with respect to the road is calculated by taking into account the speed of the own vehicle obtained from the distance sensor 11c. calculate.

  Next, based on the information obtained from the GPS receiver 11a, the latitude / longitude as the current position of the host vehicle is measured (S120). Then, the latitude / longitude calculated based on the information from the GPS receiver 11a is corrected by inertial navigation based on the acceleration information of the host vehicle obtained from the gyroscope 11b, the distance sensor 11c, and the geomagnetic sensor 11d (S130). To supplementarily explain S120 and S130, the information obtained from the GPS is coarser than a predetermined time interval. Therefore, the process of S130 is executed to correct the change in the current position accompanying the movement from obtaining GPS information at a certain time until obtaining information at the next time.

  Next, the traffic congestion level is estimated based on the speed of the preceding vehicle (S140). The traffic congestion level is represented by an integer of 1 to 5, and 5 represents a state where traffic is most congested. Specifically, the congestion level is estimated by comparing the speed limit with the average speed of the vehicle ahead in a predetermined time. For example, if the average speed of the preceding vehicle is 80% or more of the speed limit, the traffic level is 1, the traffic level is 2 if it is 60% to 80%, the traffic level 3 if it is 40% to 60%, and the traffic level 4 if it is 20% to 40%. If it is less than 20%, the traffic level is 5. In addition, the information on the speed limit of the road where the host vehicle specified from the position obtained in S130 exists is acquired via the map data input device 17.

  Next, an area (permitted position) where the decryption of the code is permitted is determined from the position of the subject vehicle after the correction in the process in S130 and the traffic congestion level estimated in S140 (S150). Here, with reference to FIG. 4, a predetermined section for determining the permitted position will be described. The section here is defined by each square area surrounded by latitude and longitude in increments of 0.00005 °, with reference to latitude 35 ° north and longitude 137 ° east (point PA shown in FIG. 4). It is.

  The operation of S150 will be specifically described. The section is selected as the traffic congestion level becomes higher with the position of the own vehicle (shown as a white circle in FIG. 4) as the center according to the traffic congestion level. Decide the region by expanding the range.

  For example, the area of the square centered on the corrected position of the vehicle is determined as the permitted position, and the length of the side of the square is 100 m for traffic jam level 1 and 200 m for traffic jam level 2. By determining the condition, the area is determined by expanding the range for selecting the section according to the size of the traffic congestion level.

  However, since the area is determined by the unit of division, it is difficult to accurately match with a good number such as 100 m. Therefore, in this embodiment, the section is selected so as to be close to the target to some extent.

  For example, when a square of 100 m square centering on the position of the host vehicle is drawn, a row of sections divided into the inside and outside of the square by each side of the square appears. With respect to the rows of these sections, if the area inside the square is wider than that outside, the permitted position may be set, and if not, the permitted position may not be set. In the example of FIG. 4, a region surrounded by a double line is a set of sections selected as a permitted position.

  Next, an encryption key determined by DES (Data Encryption Standard) is created for the decryption key determined by the latitude and the longitude of the two sides of the square which are the boundary lines of the area determined in the previous step (S160).

  The decryption key is a number in which the two pairs of latitude and longitude (latitude and longitude of two sides of the square) are arranged. Specifically, this decryption key is represented by the latitude of the side located on the south side, the latitude of the side located on the north side, the longitude of the side located on the west side, and the longitude of the side located on the east side.

  However, three digits after the decimal point and six digits after the decimal point. Therefore, if the number of digits after the decimal point is one or two digits, zero is added to the head. The order of arrangement is the latitude on the south side, the latitude on the north side, the longitude on the west side, and the longitude on the east side.

  For example, in the area surrounded by the double line in FIG. 4, the decryption key has a number of 36 digits of 0500000030035000651370000513700045. Since DES is a common key encryption, the encryption key is uniquely determined with respect to the decryption key. In S160, an encryption key corresponding to the decryption key determined in this way is created.

  Next, the traffic information is encrypted with the created encryption key to create a ciphertext (S170). The traffic jam information mentioned here is a traffic jam level, a latitude as the position of the host vehicle, and a longitude as the position of the host vehicle in this order. Note that latitude and longitude are numbers with 3 digits after the decimal point and 6 digits after the decimal point. As with the decryption key, if the decimal point is one digit or two digits, zero is added to the head.

  Finally, the ciphertext, the number of sections in the east-west direction and the north-south direction of the area where the decryption is permitted, and the offset value are set as a set, and these pieces of information are transmitted as external data through the external information input / output device 16 in a wireless form. Transmit to the surroundings (S180). In the case of FIG. 4, the number of sections in the east-west direction is 8, and the number of sections in the north-south direction is 7.

  In addition, the offset value refers to a reference point PA of 35 ° north latitude and 137 ° east longitude for each of the east-west direction and the north-south direction, and a point PB at the northeast corner of the area that is determined as an area where encryption decryption is permitted. Is the remainder obtained by dividing the distance in number of partitions by the number of partitions in the area where the decryption of the encryption is permitted. In the case of FIG. 4, in the east-west direction, there is a distance of 9 sections between the reference point PA and the point PB. Therefore, since the remainder obtained by dividing 9 by 8 (the number of sections in the east-west direction of the area where the decryption of the code is permitted) is 1, the offset value in the east-west direction is 1. Similarly in the north-south direction, the remainder 13 is obtained by dividing the number of sections 13 in the north-south direction between the reference point PA and the point PB by the number of sections 7 in the north-south direction of the area where the decryption is permitted. The east-west direction 1 and the north-south direction 6 calculated in this way are offset values in the case of FIG.

  The reason why the number of partitions and the offset value are calculated and transmitted together with the ciphertext is to uniquely determine the decryption key. There are an infinite number of ways to determine a rectangular area that includes a section to which the device belongs. Therefore, the number of sections and the offset value are used so that the rectangular area is uniquely determined.

  That is, based on the number of sections and the offset value, it can be seen that the square defined by the transmission side as the permitted position is either the area surrounded by the double line or the broken line shown in FIG. And the process (S250-S260) which considers the square to which the position belongs from these squares as a square determined as the permitted position by the transmission side (S250 to S260) is executed in the reception process described below.

  Subsequently, the reception process will be described with reference to FIG. The reception process is executed mainly by the control unit 20 included in the in-vehicle device 10. And a process is started by receiving the above-mentioned 1 set of information which consists of a ciphertext, the number of divisions, and an offset value transmitted by a 1st transmission process.

  First, based on information obtained from the GPS receiver 11a, the latitude / longitude as the current position of the host vehicle is measured (S230). Then, based on the vehicle acceleration information obtained from the gyroscope 11b, the distance sensor 11c, and the geomagnetic sensor 11d, the latitude / longitude calculated based on the information from the GPS receiver 11a is corrected by inertial navigation (S240).

  Next, a decryption key is created from the self-position corrected in S240, predetermined section information, and the received number of sections and offset value (S250). As described at the end of the description of the first transmission process, based on these pieces of information, a 36-digit number is uniquely determined in the same manner as the decryption key defined in S160.

  That is, in S250, the square area to which the corrected self-location belongs belongs among the square areas determined from the received number of partitions and the offset value, and is located on the latitude and north sides of the side located on the south side of the area. A decryption key is created from information on the latitude of the side, the longitude of the side located on the west side, and the longitude of the side located on the east side.

  Further, after the process of S250, the received ciphertext is tried to be decrypted with the created decryption key (S260). If the host vehicle is located in an area where decryption is permitted in the first transmission process, the ciphertext can be decrypted correctly.

  This is because the decryption key determined in S160 of the first transmission process matches the decryption key created in S250. On the contrary, if the own vehicle is not located in the area where the decryption permitted in the first transmission process is permitted, the ciphertext cannot be decrypted correctly.

  Therefore, after the process of S260, it is determined whether the received ciphertext has been correctly decrypted (S270). Specifically, it is determined whether or not the received ciphertext can be correctly decrypted by determining whether or not the plaintext description obtained by decrypting the ciphertext conforms to a predetermined format. Can do.

  If the decryption is successful (Yes in S270), a predetermined process is executed (S280), and the reception process is terminated. The predetermined processing is, for example, a route search in which information (congestion level information) obtained by decrypting ciphertext is notified to the driver through the display unit 14 or the voice output unit 15, or a route that bypasses the congested road is bypassed. It is something to do.

  Specifically, in this embodiment, the congestion level and the source location information are obtained by decrypting the ciphertext. Therefore, from this information, the vehicle occupant is notified, for example, as character information or graphic information through the display unit 14 that the notified level of traffic congestion has occurred near the position corresponding to the transmission source.

On the other hand, if the decryption has failed (No in S270), the reception process is terminated without executing the predetermined process.
The first transmission process and the reception process executed by the control unit 20 of the in-vehicle device 10 have been described above, but the above-described set of information including the ciphertext, the number of sections, and the offset value transmitted from the in-vehicle device 10 is as follows. It is also received by the road infrastructure 30.

  The road infrastructure 30 also attempts to decrypt the ciphertext by the same method as the in-vehicle device 10. When the ciphertext is correctly decrypted in the road infrastructure 30, the traffic jam information is provided to the information center 50 via the I / F 35.

  That is, the processing unit 31 included in the road infrastructure 30 also executes the same process as the reception process shown in FIG. However, since the road infrastructure 30 does not move, instead of S230 and S240, a process of acquiring the self-position stored in the storage medium included in the processing unit 31 is executed. Furthermore, the content of the predetermined process corresponding to S280 is read as transmission of the decrypted traffic jam information to the processing unit 51 provided in the information center 50.

  On the other hand, the information center 50 receives the traffic jam information transmitted from each road infrastructure 30 through the I / F 55, and the processing unit 51 collects the traffic jam information. For example, the average value of the traffic level in each region is obtained from the received traffic information group, and highly accurate information is obtained as the traffic level in each region. Then, processing such as distributing the congestion information with improved accuracy to the road infrastructure 30 is executed.

  However, if traffic information is transmitted from the road infrastructure 30 in the same manner as before, unnecessary traffic information for each vehicle is notified to the vehicle occupant. For this reason, in this embodiment, the information center 50 determines an area corresponding to the traffic congestion information to be transmitted as an area to be transmitted, and distributes the determined content to the road infrastructure 30 together with the traffic congestion information. Then, the road infrastructure 30 encrypts the traffic jam information by the same method as that of the above-described in-vehicle device 10 with the transmission target area notified from the information center 50 as a permitted position, and forms the electromagnetic wave around the ciphertext. Send with.

  As described above, the cryptographic communication system 1 is configured such that only a device located in an area intended by the transmission side can decrypt the cipher. Therefore, a device located in an area where it is not clearly required cannot decode the traffic jam information, and thus does not give extra information.

  Further, the road infrastructure 30 does not transmit information to the information center 50 unless the received ciphertext can be decrypted. Therefore, according to the present embodiment, unnecessary information is not transmitted and received on the communication path connecting the road infrastructure 30 and the information center 50, and congestion of the communication path can be reduced. Moreover, in order to suppress communication traffic, the road infrastructure 30 does not have to select information to be transmitted to the information center 50, and the processing load on the road infrastructure 30 can be reduced.

  Next, an example in which accident information is transmitted from the information center 50 to the in-vehicle device 10 will be described as a second embodiment. However, since the schematic configuration of the system and the hardware configuration of each device in the second embodiment are the same as those in the first embodiment, description of the same configuration as that in the first embodiment will be omitted as appropriate.

  In the second embodiment, the road infrastructure 30 encrypts the accident information received from the information center 50 by the method of the present invention and transmits it to the surroundings. Then, the in-vehicle device 10 receives and decrypts this ciphertext. In the second embodiment, the reason why the accident information is encrypted and transmitted by the method of the present invention is that the accident information is not necessary depending on the location where the user exists even if the accident information is transmitted over a wide range, similar to the traffic jam information. It is to become. In addition, since the detailed contents of the accident are contents related to privacy for the accident party, it is necessary to limit the transmission range of the accident information in consideration of this.

As an explanation of the second embodiment, a center transmission process for distributing accident information will be described first.
FIG. 6 is a flowchart showing the center transmission process. This process is a process executed mainly by the processing unit 51 provided in the information center 50.

  First, accident information and distribution area information as a permitted position are acquired from the administrator of the information center 50 through the operation switch group 52 (S310). The accident information includes information on latitude and longitude as the position where the traffic accident occurred. The distribution area information is two sets of latitude / longitude information for determining a rectangular area defined by the section described with reference to FIG.

  A specific example of how to determine the distribution area is as follows. First, the manager of the information center 50 determines the severity of the accident in three stages and inputs the value. Then, the processing unit 51 determines the delivery area based on the received information on the severity and the information on the area whose area is determined in advance so as to be proportional to the severity.

  Then, the road infrastructure 30 necessary for the radio wave to reach the entire distribution area is specified (S320). Note that information such as where each road infrastructure 30 is and where the radio waves emitted by each road infrastructure 30 reach is stored in advance in a storage medium included in the processing unit 51. And the process part 51 transmits the acquired accident information and the information of a delivery area to the process part 31 with which the specified road infrastructure 30 is provided via I / F55 (S330), and complete | finishes this process.

  Next, the second transmission process will be described with reference to FIG. The second transmission process is executed mainly by the processing unit 31 included in the road infrastructure 30. The second transmission process is started when the processing unit 31 receives information transmitted by the center transmission process.

  First, an encryption key for a decryption key that is uniquely determined from the received distribution area information is created according to DES (S460). The method for creating the decryption key is the same as S150 in the first transmission process. Then, the received accident information is converted into a ciphertext with the created encryption key (S470). Finally, the ciphertext, the number of partitions, and the offset value are transmitted through the communication unit 34 (S480), and this process ends. The number of partitions and the offset value are the same as those described in S180 of the first transmission process.

And the vehicle-mounted apparatus 10 will perform the reception process demonstrated in Example 1, if the cryptogram transmitted by the 2nd transmission process is received through the external information input / output device 16. FIG.
As described above, even when the road infrastructure 30 is the transmission subject, the same effects as in the first embodiment can be obtained. In addition, there is a case where accident information is not related to privacy because it is related to privacy. Even in such a case, if the area where decoding can be performed can be limited on the transmission side, it is possible to balance the necessity of transmitting and receiving information.
[Other variations]
In the first transmission process, the accident information may be encrypted and transmitted instead of the traffic jam information. The method of acquiring the accident information is realized such that a person who has encountered or witnessed an accident inputs the information to the control unit 20 through the operation switch group 12. In particular, when distributing the accident information to the surroundings, psychological resistance to transmitting information is softened if the area where decoding is possible is limited.

If the road infrastructure 30 decodes the accident information and transmits it to the information center 50, the information center 50 does not need to acquire the accident information from the operation switch group 52.
[Correspondence]
The correspondence relationship between the claims and the embodiments will be described. The determination means is S150, the encryption key creation means is S160 and S460, the plaintext acquisition means is S110 to S140 and S310, the encryption means is S170, the transmission means is S180 and S480, and the position acquisition means provided in the reception device is S230 to S240, decryption The key creation means is realized by S250, the decryption means is realized by S260, the position acquisition means provided in the transmission apparatus is realized by S120 to S130, the positioning means is realized by S120, and the speed measurement means is realized by S110.

1 is a diagram showing a schematic configuration of a cryptographic communication system 1. FIG. It is a block diagram which shows schematic structure of each apparatus. It is a flowchart showing a 1st transmission process. It is a figure showing a predetermined division. It is a flowchart showing a reception process. It is a flowchart showing a center transmission process. It is a flowchart showing a 2nd transmission process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Encryption communication system, 10 ... In-vehicle apparatus, 11 ... Positioning device, 11a ... GPS receiver, 11b ... Gyroscope, 11c ... Distance sensor, 11d ... Geomagnetic sensor, 12, 52 ... Operation switch group, 13 ... Voice input part , 14 ... Display section, 15 ... Audio output section, 16 ... External information input / output device, 17 ... Map data input device, 19 ... Radar, 20 ... Control section, 30 ... Road infrastructure, 31, 51 ... Processing section, 34 ... Communication unit, 35, 55 ... I / F, 50 ... Information center

Claims (10)

An encryption communication system for transmitting ciphertext by a common key cryptosystem from a transmission device to a reception device,
The transmitter is
Determining means for determining an area where decryption of the ciphertext is permitted, as a destination of the ciphertext;
An encryption key generating means for generating an encryption key based on the location information of the area determined by the determining means;
Plaintext acquisition means for acquiring plaintext to be transmitted;
An encryption unit that creates the ciphertext by encrypting the plaintext acquired by the plaintext acquisition unit with the encryption key created by the encryption key creation unit;
A transmission means for transmitting the ciphertext created by the encryption means to the surroundings in the form of electromagnetic waves;
With
The receiving device is:
Receiving means for receiving ciphertext transmitted from the transmitting means;
Position acquisition means for acquiring own position information;
A decryption key creating means for creating a decryption key based on the position information obtained by the position obtaining means;
Decryption means for decrypting the ciphertext received by the reception means with the decryption key created by the decryption key creation means;
A cryptographic communication system comprising: Receiving means for receiving a ciphertext by a common key cryptosystem transmitted from an external device in the form of electromagnetic waves;
Position acquisition means for acquiring own position information;
A decryption key creating means for creating a decryption key based on the position information obtained by the position obtaining means;
Decryption means for decrypting the ciphertext received by the reception means with the decryption key created by the decryption key creation means;
A receiving apparatus comprising: The receiving device according to claim 2, which is mounted on a moving body,
The position acquisition means includes
Positioning means for positioning the current position based on GPS signals transmitted from GPS satellites;
Acceleration measuring means for measuring the acceleration of the receiving device;
Correction means for correcting the current position measured by the positioning means based on information on acceleration measured by the acceleration measuring means;
The current position after correction by the correction means is acquired as the position information of itself,
The receiving device, wherein the decryption key creation means creates a decryption key based on the current position after correction by the correction means. A transmission device that transmits ciphertext using a common key cryptosystem,
Determining means for determining an area where decryption of the ciphertext is permitted, as a destination of the ciphertext;
An encryption key generating means for generating an encryption key based on the location information of the area determined by the determining means;
Plaintext acquisition means for acquiring plaintext to be transmitted;
An encryption unit that creates the ciphertext by encrypting the plaintext acquired by the plaintext acquisition unit with the encryption key created by the encryption key creation unit;
A transmission means for transmitting the ciphertext created by the encryption means to the surroundings in the form of electromagnetic waves;
A transmission device comprising: The determining means determines an area where the decryption of the ciphertext is permitted by selecting an arbitrary section from among a plurality of sections predetermined as a transmission target area by the transmitting means. The transmission device according to claim 4. Provided with position acquisition means for acquiring own position information;
The transmission device according to claim 4 or 5, wherein the determination unit determines an area where the decryption of the ciphertext is permitted based on the position information acquired by the position acquisition unit. The transmission device according to claim 6, which is mounted on a mobile body,
The position acquisition means includes
Positioning means for positioning the current position based on GPS signals transmitted from GPS satellites;
Acceleration measuring means for measuring acceleration generated in the transmission device;
Correction means for correcting the current position measured by the positioning means based on information on acceleration measured by the acceleration measuring means;
The current position after correction corrected by the correction means is acquired as the position information of itself,
The transmission device according to claim 1, wherein the determination unit determines a region where the decryption of the ciphertext is permitted based on a current position corrected by the correction unit. The transmission device according to claim 6 or 7, which is mounted on a vehicle,
Speed measuring means for measuring the speed of other vehicles around the host vehicle;
Based on the measurement result of the speed measuring means, estimating means for estimating the degree of traffic congestion around the host vehicle,
With
The transmission apparatus according to claim 1, wherein the plaintext acquisition unit acquires information on a degree of congestion estimated by the estimation unit as the plaintext. The determining means determines an area where the decryption of the ciphertext is permitted by expanding the area where the decryption of the ciphertext is permitted, as the degree of congestion estimated by the estimation means increases. The transmission device according to claim 8. The transmission device according to any one of claims 4 to 7, wherein the plaintext acquisition unit acquires the plaintext through a user interface.