Patent Publication Number: US-7212989-B1

Title: Vehicle-mounted communication device and road-to-vehicle communication device

Description:
This application is a continuation, of Application No. PCT/JP98/00342, filed in Japan on Jan. 28, 1998, and which designated the U.S.A. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a vehicle-mounted communication device and a road-to-vehicle communication device, and particularly to a vehicle-mounted communication device mounted on a vehicle and to a road-to-vehicle communication device which effects communication processing between the vehicle-mounted communication device and an on-road apparatus installed on a road side. 
     BACKGROUND ART 
     In recent years, an automatic toll collecting system has been developed which utilizes a toll pre-paid type card or a toll post-payment type card to receive charges for using charged facilities, for example, to receive a toll charged on a toll road. In the automatic toll collecting system, on-road apparatuses for road-to-vehicle communications (hereinafter referred to as “on-road apparatuses”) with antennas, each of which serves as an interrogator for making inquiries with respect to a vehicle for information in order to collect tolls automatically at entrance and exit gates of the toll road, are provided on the road side, and each of vehicle-mounted apparatuses for road-to-vehicle communications communications (hereinafter referred to as “vehicle-mounted apparatuses”) with antennas, each of which serves as a responder for responding to the information, with respect to which an inquiry was made is mounted on the vehicle, whereby the information is transferred by radio communications between the vehicle-mounted apparatus and the on-road apparatus. 
     In order to transfer the information between the vehicle-mounted apparatus and the on-road apparatus, toll information or vehicle information about a vehicle, and information about a user must be stored. For this reason, an IC card in which a large quantity of data can be stored may be used with information being written therein. 
     However, as described above, when the information is transferred between the vehicle-mounted apparatus and the on-road apparatus or when the information is transferred to and received from the IC card, the information is used with a form thereof left unchanged. As a result, there exists a problem that a person not intended by a user can easily disclose contents of the information. 
     Accordingly, there has been proposed an electronic identification system in which secrecy is kept by identifying that a transmitted secret code such as an inherent code coincides with at least one of a plurality of predetermined secret codes, thereby resulting in improvement of security (see Japanese Patent Application Laid-Open (JP-A) No. 6-511097). 
     However, in a conventional electronic identification system, only one kind of secret code is assigned to a user, and therefore, secret codes must be set correspondingly to the number of users so as to identify a great number of users. For this reason, in a road-to-vehicle communication device in which information is transferred to and received from each of a great number of users, the load on the device increases. Further, only one kind of secret code is assigned to a user, and therefore, when the secret code leaks out, the security of a system used by the user, namely, of the road-to-vehicle communication device, deteriorates. 
     Further, in order to collect a toll automatically by transferring information between the vehicle-mounted apparatus and the on-road apparatus, vehicle information about a vehicle and user information about a user, such as a balance of charges for accounting must be stored. Accordingly, the IC card in which a large quantity of data can be stored may be used with information being written therein. 
     However, in a case of transferring the above-described information, when the information is used in a general description form, there exists a problem that a person that is not intended by a user or an information provider can illegally alter or falsify the contents of the information and can also unlawfully utilize such information. 
     Accordingly, there has been proposed an automatic toll collecting system in which information communicated between an on-road apparatus and a vehicle-mounted apparatus is encoded so as to improve the security (see Japanese Patent Application Laid-Open (JP-A) No. 6-60237). In this system, encoded information stored in an IC card or encoded information from the on-road apparatus is made into a common sentence structure (made into a general descriptive form) in the vehicle-mounted apparatus, and processing for user information such as a balance of charges is effected. 
     However, in the conventional automatic toll collecting system, the user information made into a common sentence structure in the vehicle-mounted apparatus is temporarily stored. Accordingly, a person that is not intended by the user or the information provider can easily falsify the contents of the user information about a user such as the balance of charges, and the like, thereby resulting in deterioration of security. 
     SUMMARY OF THE INVENTION 
     In view of the above-described circumstances, an object of the present invention is to provide a vehicle-mounted communication device and a road-to-vehicle communication device, that can improve security using a simple structure and in a simple manner. 
     In addition to the above-described object, an object of the present invention is to provide a vehicle-mounted communication device and a road-to-vehicle communication device that can allow communication of information using a simple structure by making it difficult to leak or falsify information. 
     In order to achieve the above-described objects, a vehicle-mounted communication device comprises: transmitting/receiving means provided for communication of information with road-side communication means located at a road side; and relay means for relaying encryption information received from the road side by the transmitting/receiving means to an IC card which includes storage means for storing user information regarding a balance of charges and which also includes encryption means encrypts and outputs output information based on the user information and decodes encrypted input information regarding the user information. 
     The invention is a vehicle-mounted communication device as described above, wherein the relay means relays the output information encrypted by the IC card to the transmitting/receiving means. 
     The invention is a vehicle-mounted communication device as described above, further comprising encryption information storage means in which the encryption information is temporarily stored, wherein the transmitting/receiving means stores the encryption information in the encryption information storage means and transmits as is the encryption information stored in the encryption information storage means. 
     The invention is a vehicle-mounted communication device as described above, wherein at least one of the IC card and the road-side communication means outputs a portion of the output information in a state without encryption and information display means for displaying the portion of the output information outputted without being encrypted is further provided. 
     The invention is a road-to-vehicle communication device comprising: a vehicle-mounted communication device as described above, and road-side control means being located at a road side, including road-side communication means and provided for intercommunication of information with the vehicle-mounted communication device, and also including road-side encryption means for encrypting transmitted information and decoding received information. 
     The invention is a road-to-vehicle communication device as described above, wherein road-side encryption means of the road-side control means installed at an entrance gate effects encryption of transmitted information and road-side encryption means of the road-side control means installed at a toll reception gate effects only decoding of received information. 
     The invention is a road-to-vehicle communication device as descibed above, wherein the transmitted information is accounting information regarding accounting processing of charged facilities. 
     The invention is a road-to-vehicle communication device comprising: road-side control means being located at a road side, including road-side communication means and provided for intercommunication of information with vehicle-mounted communication means, and also including first encryption means for encrypting transmitted information, and decoding received information with a first electronic key; information control means including information transfer means which stores therein user information regarding at least one of a vehicle and a user and through which information is mutually transferred with respect to the vehicle-mounted communication means, and also including second encryption means for encrypting output information, and decoding input information with a second electronic key; and vehicle-mounted control means being installed on a vehicle side, including vehicle-mounted communication means provided for intercommunication of information with respect to the road-side communication device and for mutual transfer of information with respect to the information control means, and also including third encryption means which, during the communication of information, encrypts transmitted information and decodes received information with the first electronic key, and which during the transfer of information, encrypts output information and decodes input information with the second electronic key. 
     The invention of claim  9  is a road-to-vehicle communication device according to claim  8 , wherein each group of the first encryption means and the road-side communication means, the second encryption means and the information transfer means, and the third encryption means and the vehicle-mounted communication means are provided on the same substrate. 
     At the vehicle-mounted communication device intercommunication of information is carried out with respect to the road-side communication means located at the road side, with the transmitting/receiving means. The IC card is attachable and detachable at the vehicle-mounted communication device and stores in the storage means the user information regarding the balance of charges. The encryption means encrypts output information based on the user information and then outputs. The encryption means also decodes the encrypted input information regarding the user information. Among the information received from the road side by the transmitting/receiving means, the encryption information is relayed to the IC card by the relay means. Accordingly, the encryption information passes through the vehicle-mounted communication device in a form of being left unchanged, and thus, the secrecy of the encryption information is maintained and the security thereof is protected. 
     As described above, the above-described relay means relays the output information encrypted by the IC card to the transmitting/receiving means, so as to transmit the output information based on the encrypted user information from the IC card to the road side in a form of being left unchanged. As a result, the secrecy of the output information can be maintained and the security thereof can be protected. 
     As described above, the vehicle-mounted communication device can further include the encryption information storage means in which encryption information is temporarily stored. The encryption information storage means stores therein encryption information with the transmitting/receiving means. Further, the stored encryption information is transmitted as is by the transmitting/receiving means. As a result, the encryption information from the road side, which is unrelated to the user information stored in the IC card and is desired to be retained, for example, gate information which indicates an entrance gate, a mid-route, and the like, can be held in a form of being left unchanged and can also be transmitted to the road side. Accordingly, the secrecy of the information from the road side can be maintained and the security thereof can be protected. 
     Further, as described above, the information display means is further provided which outputs the portion of output information desired to be made known to a user without encryption by the IC card and displays the portion of the output information outputted without being encrypted, thereby resulting in that the user can confirm completion of communication or details that are results of accounting processing. 
     As described above, in the road-to-vehicle communication device of the present invention, the IC card is mounted in the vehicle-mounted communication device and information is mutually communicated with respect to the road-side control means located at the road side. The road-side encryption means of the road-side control means encrypts transmitted information and decodes received information. Accordingly, transmitted information to be transmitted from the road side passes through the vehicle-mounted communication device in a form of being encrypted. As described above as well, processing such as reception of charges can be effected for the IC card in such a manner that accounting information regarding accounting processing of charged facilities is transmitted and received as the transmitted information, and the resulting information also passes through the vehicle-mounted communication device in the form of being encrypted, thereby resulting in no damage to the secrecy of the information. 
     As described above, the road-to-vehicle communication device encrypts transmitted information with the road-side encryption means of the road-side control means located at an entrance gate and decodes received information by the road-side encryption means of the road-side control means located at a toll reception gate. As a result, the vehicle-mounted communication device does not have encryption means, and therefore, irregularities in charge payment caused by analysis of a cipher of the vehicle-mounted communication device can be made impossible. 
     Further, according to the invention, information is mutually communicated between the road-side communication means of the road-side control means and the vehicle-mounted communication means of the vehicle-mounted control means. Further, information is mutually transferred between the vehicle-mounted communication means of the vehicle-mounted control means and the information transfer means of the information control means. 
     During the communication of information, the road-side control means uses the first encryption means, with the first electronic key, to encrypt transmitted information to be transmitted to the vehicle-mounted control means and to decode received information from the vehicle-mounted control means. Further, the vehicle-mounted control means uses the third encryption means, with the first electronic key, to encrypt transmitted information to be transmitted to the road-side control means and to decode received information from the road-side control means. Accordingly, information can be encrypted using the first electronic key so as to be mutually communicated between the road-side control means and the vehicle-mounted control means, and therefore, the secrecy of information is maintained and the security thereof is thereby protected. 
     During the transfer of information, the vehicle-mounted control means uses the third encryption means, with the second electronic key, to encrypt output information and to decode input information. The information transfer means stores therein user information regarding at least one of a vehicle and a user. When the user information is outputted to the vehicle-mounted control means, the information transfer means uses the second encryption means, with the second electronic key, to encrypt, as output information, the user information and to decode input information from the vehicle-mounted control means. Accordingly, information can be encrypted using the second electronic key so as to be mutually transferred between the vehicle-mounted control means and the information transfer means, and therefore, the secrecy is maintained and the security is thereby protected. 
     As described above, secrecy is independently maintained using different electronic keys respectively for the communication of information and for the transfer of information, and therefore, the security of the road-to-vehicle communication device can be improved. Further, since secrecy is independently held, leakage of information can be restrained to the minimum until the secrecy becomes clear. 
     The above-described first, second, and third encryption means are each that which maintains secrecy, and therefore, so long as these encryption means are each made clear, the secrecy can be made clear. Accordingly, as described above as well, by providing each of the first encryption means and the road-side communication means, the second encryption means and the information transfer means, and the third encryption means and the vehicle-mounted communication means on the same substrate, on the same chip, for example, decoding such as analysis becomes difficult and the security of the road-to-vehicle communication device can be improved. 
     In the vehicle-mounted communication device of the present invention, among the information received from the road side by the transmitting/receiving means, the encryption information is relayed by the relay means to the IC card, and therefore, the encryption information passes through the vehicle-mounted communication device in the form of being left unchanged. Accordingly, there is an effect wherein the secrecy of the encryption information is maintained and the security can be protected. 
     In the road-to-vehicle communication device of the present invention, the IC card is mounted in the vehicle-mounted communication device which relays the encryption information and information is mutually communicated with respect to the road-side control means which encrypts transmitted information and decodes received information. Accordingly, there is an effect wherein the security can be maintained without the secrecy of the information being damaged. 
     Further, secrecy is independently maintained using different electronic keys, and therefore, there is an effect wherein the security of the road-to-vehicle communication device can be improved. 
     Further, by providing the first, second, and third encryption means, respectively together with corresponding road-side communication means, information transfer means, and vehicle-mounted communication means, on the same substrate, there is an effect wherein decoding such as analysis becomes difficult, improving the security of the road-to-vehicle communication device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram that shows an automatic toll receiving system according to a first embodiment of the present invention. 
         FIG. 2  is a schematic perspective view that shows a mid-route in the automatic toll receiving system of the first embodiment. 
         FIG. 3  is a block diagram that shows a vehicle-mounted apparatus of the first embodiment. 
         FIG. 4  is a block diagram that shows one example of an on-road apparatus of the first embodiment. 
         FIG. 5  is a block diagram that shows a structure of an IC card of the first embodiment. 
         FIG. 6  is a flow chart that shows a flow in a process of the vehicle-mounted apparatus of the first embodiment. 
         FIG. 7  is a flow chart that shows a flow in a process of the on-road apparatus of the first embodiment in a mid-route. 
         FIG. 8  is a flow chart that shows a flow in an exit gate process of the vehicle-mounted apparatus of the first embodiment. 
         FIG. 9  is a flow chart that shows a flow in a process of the on-road apparatus at an exit gate of the first embodiment. 
         FIG. 10  is a flow chart that shows a flow in a process of the IC card of the first embodiment. 
         FIG. 11  is an image diagram that shows the relationship between the on-road apparatus, the vehicle-mounted apparatus, and the IC card of the first embodiment when information is mutually transferred therebetween. 
         FIG. 12  is a block diagram that shows an automatic toll receiving system according to a second embodiment of the present invention. 
         FIG. 13  is a block diagram that shows a vehicle-mounted apparatus of the second embodiment. 
         FIG. 14  is a block diagram that shows one example of an on-road apparatus of the second embodiment. 
         FIG. 15  is a block diagram that shows an IC card and an information writing device of the second embodiment. 
         FIG. 16  is a flow chart that shows a process routine of the information writing device of the second embodiment. 
         FIG. 17  is a flow chart that shows a process routine of the vehicle-mounted apparatus with respect to the information writing device of the second embodiment. 
         FIG. 18  is a flow chart that shows a communication processing routine of the vehicle-mounted apparatus of the second embodiment. 
         FIG. 19  is a flow chart that shows a process routine of the on-road apparatus of the second embodiment. 
         FIG. 20  is a flow chart that shows a process routine of the IC card of the second embodiment. 
         FIG. 21  is an image diagram showing transmitting and receiving of information, which is effected between the information writing device and the vehicle-mounted apparatus of the second embodiment. 
         FIG. 22  is an image diagram showing transmitting and receiving of information, which is effected between an IC card read/write device and the vehicle-mounted apparatus of the second embodiment. 
         FIG. 23  is an image diagram showing transmitting and receiving of information, which is effected between the on-road apparatus and the vehicle-mounted apparatus and between the IC card read/write device and the vehicle-mounted apparatus in the second embodiment. 
     
    
    
     BEST MODES FOR CARRYING OUT THE INVENTION 
     Embodiments of the present invention will hereinafter be described in detail with reference to the accompanying drawings. The present embodiments each show that the present invention is applied to an automatic toll receiving system for automatically receiving a toll from each of vehicles running on a toll road or the like. 
     In the automatic toll receiving system, information is transferred between an apparatus mounted on a vehicle and an on-road apparatus having flat antennas (or other antennas, for example, Yagi antennas) provided at ground portions of an entrance gate, an exit gate, and the like through radio communications to thereby determine a traffic section (route) over which the vehicle has been driven and the type of the vehicle and automatically accept a traffic toll or the like without stopping the vehicle at the entrance and exit gates. 
     First Embodiment 
     A first embodiment will first be described. 
     As shown in  FIG. 1 , an automatic toll receiving system of the present embodiment is structured to include an on-road apparatus  10  provided on the road side and a vehicle-mounted apparatus  30  mounted on a vehicle, and information is mutually transferred between the on-road apparatus  10  and the vehicle-mounted apparatus  30  by radio communications. The on-road apparatus communicating with the vehicle-mounted apparatus  30  is provided with flat antennas (or other antennas, for example, Yagi antennas) for transmitting and receiving various information and is disposed at each of an entrance gate of a toll road, a mid-route (check barrier), and an exit gate or the like. The on-road apparatus  10  includes a memory  28  (see  FIG. 4 ) in which an electronic key A for encryption of information is stored and the vehicle-mounted apparatus  30  includes a storage circuit  48  (see  FIG. 3 ) in which the above-described encryption information is stored, as will be described in detail later. When information is mutually transferred between the on-road apparatus  10  and the vehicle-mounted apparatus  30  by radio communications, transmitted information is encrypted using the electronic key A on the side of the on-road apparatus and is transmitted to the vehicle-mounted apparatus  30 . This encryption (or decoding) can be provided using a method based on Data Encryption Standard (a so-called DES) or the like. 
     An IC card  62  (which will be described in detail later) in which various information is stored is provided so as to be detachable from the vehicle-mounted apparatus  30 . Information is mutually transferred between the vehicle-mounted apparatus  30  and the IC card  62 . The IC card  62  includes a memory  70  (see  FIG. 5 ) in which a security mechanism M provided with a process for encrypting or decoding information is stored. This security mechanism is used to manufacture or issue the IC card  62  and is in advance set in accordance with an operation thereof. A plurality of logic which are provided for encryption or decoding by the security mechanism can be stored on the side of the on-road apparatus and any one security mechanism can be selectively used. 
     Next, the vehicle-mounted apparatus  30  and the on-road apparatus  10  communicating with the vehicle-mounted apparatus  30  will be described in detail. Further, in the present embodiment, a description will be given in which an on-road apparatus provided in the mid-route  200  is shown as an example. Further, for simplifying an explanation, a mid-route antenna  218  provided for radio communication with a vehicle  90  traveling along a lane  202  and a mid-route antenna control device  232  are used for the explanation. Further, a vehicle-mounted battery (not shown) is connected to the vehicle-mounted apparatus  30 . 
     As shown in  FIG. 2 , in the mid-route  200  located immediately before or after a branching point of a toll road, two lanes, the lane  202  and a lane  204 , are provided side by side between a ground  208  and a ground  214 . An arch  216  is disposed between the ground  208  and the ground  214  in such a manner as to extend over the lanes  202  and  204 . Route recognizing antennas  218 ,  220 , and  222  are disposed on the arch  216 . The route recognizing antenna  218  is located above the lane  202  for radio communication with a vehicle traveling along the lane  202 . The route recognizing antenna  222  is located above the lane  204  for radio communication with a vehicle traveling along the lane  204 . The route recognizing antenna  220  is disposed substantially at an intermediate point between the route recognizing antennas  218  and  222  such that it is located above a centerline  206  between the lanes  202  and  204 , for radio communication with a vehicle running so as to straddle the boundary between the lanes  202  and  204 . 
     A route control center  230  equipped with the route recognizing antenna control device  232  is disposed on the ground  214 . The route recognizing antennas  218 ,  220 , and  222  are connected to the route recognizing antenna control device  232 . 
     In the above-described mid-route  200 , the route recognizing antenna control device  232  transmits route information, which represents the kind of route a vehicle  90  traveled on a toll road, to the vehicle-mounted device  30  mounted on the vehicle  90 , via the route recognizing antenna. The route recognizing antenna control device  232  can be connected to a central computer for collectively controlling a running state of the vehicle on the toll road. A recovery gate can be disposed at the mid-route  200  so as to write the route information indicating a mid-route into the vehicle-mounted apparatus using the IC card  62 . The recovery gate is provided with an IC card read/write device in which the IC card  62  is removably mounted. The IC card read/write device is connected to the central computer. The recovery gate may be disposed at a parking area or a service area. 
     Meanwhile, at the entrance gate that is another on-road apparatus, entrance information of the toll road is transmitted to the vehicle-mounted apparatus  30  mounted on the vehicle. Further, at the exit gate, exit information which indicates an exit gate is transmitted to the vehicle-mounted apparatus  30  mounted on a vehicle, and for example, traffic charges or tolls corresponding to the section (route) run by the vehicle or to the type of vehicle are automatically received. 
     This entrance information and exit information can be transferred by an operator via an IC card. For example, when a communication error occurs, at the recovery gate for writing in data such as the entrance information which indicates an entrance gate using the IC card or for reading out data stored in the vehicle-mounted apparatus, the IC card read/write device to which the IC card  62  can be attached and detached is used to enable execution of transfer of the entrance and exit information. Codes such as numbers or the like, which are in advance assigned respectively to positions of toll roads, may be used for the entrance information and route information. 
     As shown in  FIG. 3 , the vehicle-mounted apparatus  30  is provided with a receiving antenna  32  for receiving a data signal transmitted from the on-road apparatus. The receiving antenna  32  is connected via a data signal receiving circuit  44  to a signal processing circuit  46  structured so as to include a microcomputer. The microcomputer of the signal processing circuit  46  stores therein a processing program, which will be described below. 
     A storage circuit  48  is connected to the signal processing circuit  46 . Information regarding the vehicle-mounted apparatus is stored in the storage circuit  48 . Namely, when the vehicle-mounted apparatus is mounted on a vehicle, a vehicle number (the number recorded on a number plate) serving as an ID code and information regarding the type of a vehicle on which the vehicle-mounted apparatus is mounted are in advance stored in the storage circuit  48 . Further, a region in which encryption information is stored is in advance allocated in the storage circuit  48 . The encryption information includes the entrance information (entrance number, date and time at which the vehicle passed through the entrance gate, and the like) encrypted on a on-road apparatus side, and also includes route information regarding a check barrier (check barrier number, date and time at which the vehicle passed through the check barrier), if the vehicle passes through the mid-route (check barrier), which will be described later in detail. 
     A transmission circuit  50  which transmits as a response signal a data signal including an ID code is connected to the signal processing circuit  46 . The transmission circuit  50  is connected to a transmission antenna  52 . The vehicle-mounted apparatus  30  transmits the data signal from the signal processing circuit  46  via the transmission antenna  52 . The transmission antenna  52  may be provided to function as a transmission/reception antenna. 
     An IC card read/write device  60  is connected to the vehicle-mounted apparatus  30  so as to read data from the mounted IC card  62  and to write data in the IC card  62 . The IC card read/write device  60  is equipped with a limit switch  58  which mechanically detects insertion of the IC card  62 . Whether the IC card is inserted may be optically detected by determining whether light is interrupted by the inserted IC card using a photo-interrupter formed with a light emitting element and a light receiving element being disposed opposite to each other. 
     Connected to the signal processing circuit  46  are a display  54  comprised of an LCD or a CRT for displaying whether the IC card is inserted or non-inserted and other information including the card value balance, and a ten-key pad  56  (a simple push-button switch may also be used) which inputs a signal to the signal processing circuit  46 . 
     As shown in  FIG. 4 , the on-road apparatus for a vehicle traveling along the lane  202  is comprised of the mid-route antenna  218  and the mid-route antenna control device  232 . The mid-route antenna  218  is comprised of a transmission antenna  22  and a receiving antenna  26 . The mid-route antenna control device  232  is provided with a signal processing circuit  12  structured so as to include a microcomputer. The microcomputer stores therein a processing program which will be described later. The signal processing circuit  12  can be connected to a central computer  400  (not shown). 
     The signal processing circuit  12  is connected to a transmission circuit  14  which generates a data signal including an instruction. The transmission circuit  14  is connected to the transmission antenna  22  and a signal from the transmission circuit  14  is transmitted from the transmission antenna  22 . Further, connected to the signal processing circuit  12  is a receiving circuit  24  to which the receiving antenna  26  for receiving a signal transmitted from the vehicle-mounted apparatus  30  is connected. The receiving circuit  24  fetches and outputs a data signal included in the signal transmitted from the vehicle-mounted apparatus  30 , via the receiving antenna  26 . 
     Also connected to the signal processing circuit  12  is the memory  28 . The memory  28  in advance stores therein the electronic key A. Encryption of transmitted information and decoding of received information are effected using the electronic key A in the on-road apparatus at the mid-route. The memory  28  also in advance stores therein the security mechanism M used for transfer of data between the IC card  62  and the memory  28 . 
     Other structures in the mid-route  200  are the same as the above-described ones, and therefore, descriptions thereof will be omitted. Further, respective antennas and antenna control devices at the entrance gate and the exit gate are substantially the same in structure as those referred to above, and descriptions thereof will be omitted. 
     In the above-described vehicle-mounted apparatus and on-road apparatus, an antenna formed with a transmission antenna and a receiving antenna being separated from each other is used. However, a transmission/reception type antenna may be used. 
     Further, in the above-described embodiment, the same electronic key is used both for encryption and decoding, but different electronic keys may also be used. 
     As shown in  FIG. 5 , the IC card  62 , which can be inserted in the vehicle-mounted apparatus  30 , is comprised of a microcomputer including a CPU  64 , a RAM  66 , a ROM  68 , the memory  70 , and an input/output (I/O) port  72 , which are connected by a bus  74  so as to allow transfer of a command or data therebetween. The memory  70  is used to store the security mechanism M and various information. The ROM  68  stores therein a processing routine which will be described later. The input/output port  72  can be connected to the vehicle-mounted apparatus  30 . Although not illustrated, the IC card  62  is provided with a power source circuit so as to supply a power source when necessary. 
     The above-described IC card can store, as various information, information regarding the vehicle-mounted apparatus such as a card number, balance information, information about utilization details (entrance gate number, exit gate number, toll, time and date of utilization, and the like), and also can store a certified key code for having a card correspond to a vehicle-mounted apparatus. 
     Next, an operation of the present embodiment will be described. 
     A description will first be given of communication processing which is mutually effected between an on-road apparatus and the vehicle-mounted apparatus.  FIG. 11  shows a main process effected in each of the on-road apparatus, the vehicle-mounted apparatus, and the IC card, and a flow of information which is mutually transferred therebetween. 
     As shown in  FIG. 7 , in step  114 , the on-road apparatus located in the mid-route transmits an inquiry signal until it receives a response signal from the vehicle-mounted apparatus  30 . When the on-road apparatus receives the response signal (when the decision of step  116  is affirmative), in the subsequent step  118 , gate information, in this case, route information is encrypted by the electronic key A (corresponding to process S 1  shown in  FIG. 11 ). In step  120 , a signal including the encrypted route information and the like is transmitted (corresponding to a transfer w 1  in  FIG. 11 ). The above-described inquiry signal includes information that indicates the kind of gate at which the on-road apparatus is provided. The information that represents the kind of gate includes, for example, a gate number expressed by a common sentence or simple common-sentence information such as “entrance”, “mid-route”, and the like. 
     Further, in the on-road apparatus at the entrance gate, substantially the same processing as the above-described one is effected, but in place of the signal including the route information and the like, a signal including an entrance gate number indicating an entrance gate, and the like is encrypted and transmitted. Further, in the on-road apparatus at the exit gate as well, substantially the same processing as the above-described one is effected. A toll receiving operation effected via communications will be described later. 
     The on-road apparatus as can transmit, to the vehicle-mounted apparatus, simple common-sentence information as the information that indicates the kind of gate. Other information may also be selectively indicated as common-sentence information or encryption information in the on-road apparatus by separating from each other beforehand information that may be made into a common sentence as simple common-sentence information, and information that should be encrypted as encryption information. 
     As described above, the on-road apparatus  10  transmits to the vehicle-mounted apparatus  30  the encryption information, and therefore, the information transferred between the on-road apparatus  10  and the vehicle-mounted apparatus  30  can maintain secrecy, and security with respect to interception of information is improved. 
       FIG. 6  shows in detail communication processing of the vehicle-mounted apparatus. When in step  102  the vehicle-mounted apparatus waits until it receives an inquiry signal from the on-road apparatus, and then receives the inquiry signal (when the decision of step  102  is affirmative), in the subsequent step  104 , the vehicle-mounted apparatus reads vehicle information (for example, an ID code such as an identification code that specifies a driver&#39;s own vehicle) and transmits, as a response signal, a signal including the vehicle information. 
     When in step  106  the vehicle-mounted apparatus waits until it receives a signal from the on-road apparatus and then receives the signal (when the decision of step  106  is affirmative), it is determined that certification of the on-road apparatus and the vehicle-mounted apparatus has been completed, and in the subsequent step  108 , it is determined whether accounting processing is required by determining whether the kind of gate indicates the exit gate using the information included in the inquiry signal and indicating the kind of gate at which the on-road apparatus is provided. When the kind of gate is the exit gate, accounting processing is required, and therefore, the decision of step  108  is affirmative. In step  112 , the accounting processing is executed, as will be described later, and the present routine ends. 
     On the other hand, when the kind of gate is an entrance gate or a mid-route, the accounting processing is not required, and therefore, the decision of step  108  is negative and the process proceeds to step  110 . In step  110 , information transmitted from a gate at which the accounting processing is not required, namely, encryption information based on the signal received in step  106  is stored in the storage circuit  48  as is (corresponding to a process S 6  in  FIG. 11 ) and the present routine ends. Accordingly, the contents of the entrance information or route information are stored in the storage circuit  48  of the vehicle-mounted apparatus  30  in a state of being left encrypted. 
     As described above, since the entrance information or route information is maintained in the vehicle-mounted apparatus  30  in a state of being left encrypted, it becomes difficult to intercept the information transferred between the on-road apparatus  10  and the vehicle-mounted apparatus  30  resulting from a common-sentence structure and secrecy is maintained, thereby resulting in improvement of security with respect to interception of information. Further, the vehicle-mounted apparatus may merely store the encrypted information and does not need to provide a processing portion for encryption or decoding. For this reason, irregularities in charge payment caused by alteration, reproduction, and falsification due to disassembly inspection of a vehicle-mounted apparatus or analysis of a cipher are made impossible and the device configuration can be simplified. 
     Next, a description will be given of processing at an exit gate. 
     As shown in  FIG. 9 , when in step  136  an on-road apparatus installed at an exit gate transmits an inquiry signal including the kind of gate until it receives a response signal from the vehicle-mounted apparatus  30  and the on-road apparatus then receives the response signal (when the decision of step  138  is affirmative), in the subsequent step  138 , the on-road apparatus transmits an information read-out requesting signal to the vehicle-mounted apparatus  30 . This step  138  gives a request for reading out the encryption information stored in the storage circuit  48  of the vehicle-mounted apparatus  30  to the vehicle-mounted apparatus. Subsequently, when in step  140  the on-road apparatus transmits the information read-out requesting signal until it receives a signal from the vehicle-mounted apparatus  30  and the on-road apparatus then receives the signal (when the decision of step  142  is affirmative), in the subsequent step  144 , the electronic key A is read and the received signal is decoded using the electronic key A (corresponding to a process S 2  in  FIG. 11 ). 
     Meanwhile, different electronic keys A can be used at the time of encryption and decoding, and an electronic key B (≠A) used for decoding may be stored and used. 
     In the subsequent step  146 , using the decoded entrance information and route information and information regarding the type of a vehicle stored in the vehicle-mounted apparatus, tolls charged the vehicle in a distance from the entrance gate, the mid-route, and until the exit gate are calculated, and data or command is generated which is used to collect automatically the calculated tolls using the IC card (corresponding to a process S 3  in  FIG. 11 ). In the subsequent step  148 , the generated data or command is encrypted by the security mechanism M of the IC card (corresponding to process S 4  in  FIG. 11 ), and in the subsequent step  150 , the encrypted data or command is transmitted. The data or command encrypted in step  148  is transmitted through the vehicle-mounted apparatus and is transferred to the IC card, as will be described later in detail (corresponding to a transfer w 3  in  FIG. 11 ). 
     In the subsequent step  152 , the on-road apparatus waits until it receives a signal from the vehicle-mounted apparatus, and when the on-road apparatus receives the signal (when the decision of step  152  is affirmative), in the subsequent step  154 , the signal is decoded by the security mechanism M of the IC card. The received signal is an information signal from the IC card. In other words, the encryption information outputted from the IC card  62  is transmitted by the vehicle-mounted apparatus in a state of being left unchanged (corresponding to the transfer w 3  in  FIG. 11 ). Further, when the IC card does not have the security mechanism M, as will be described later, the IC card sends back to the on-road apparatus the encryption information in a state of being left unchanged, for example. 
     In the subsequent step  154 , the received signal is decoded. In step  156 , based on a determination as to whether the data or command transmitted in the above-described step  150  has been sent back left unchanged, it is determined whether accounting processing has been carried out using the IC card  62  mounted on the vehicle-mounted apparatus  30 . When the transmitted data or command has been sent back left unchanged, the decision of step  156  is affirmative, and in step  158 , the data or command is encrypted by a security mechanism different from the security mechanism M. Thereafter, the process returns to step  150  and the above-described process is repeated. 
     In the foregoing, first, a cipher is transmitted by the security mechanism M. When this mechanism is different from that at the side of the IC card  62 , it is sequentially changed to the different mechanism, and thereafter, encryption is effected so as to allow coincidence of security mechanisms. Alternatively, first, the mechanism at the side of the IC card  62  is interrogated, and based on the answer thereto, the security mechanism may be determined. As a result, even when one security mechanism to be used is selected from a great number of security mechanisms, high speed processing becomes possible. 
     On the other hand, when the decision of step  156  is negative, it is determined that the accounting processing has been carried out using the IC card  62 . In the subsequent step  160 , it is determined whether the received signal includes data indicating that reception of tolls has been completed. When the signal does not include such data, the decision of step  160  is negative and the process returns to step  152 . When the received signal includes the data which indicates that reception of tolls has been completed, the decision of step  160  is affirmative. In the subsequent step  162 , utilization details regarding reception of tolls are prepared (corresponding to a process S 5  in  FIG. 11 ), and are further transmitted, together with an end signal, to the vehicle-mounted apparatus in the form of a common sentence without being encrypted (corresponding to a transfer w 5  in  FIG. 11 ). Meanwhile, the preparation of utilization details effected by the on-road apparatus and the transmission of the end signal to the vehicle-mounted apparatus may also be carried out in the IC card  62  (corresponding to a transfer w 6  in  FIG. 11 ). 
       FIG. 8  shows in detail, as processing effected by the vehicle-mounted apparatus, an exit gate process in step  112  shown in  FIG. 6 . In step  122 , the vehicle-mounted apparatus waits until it receives the information read-out requesting signal transmitted from the on-road apparatus. When the vehicle-mounted apparatus receives the information read-out requesting signal (when the decision of step  122  is affirmative), in the subsequent step  124 , the encryption information stored in the storage circuit  48  is read out as is left unchanged. In the subsequent step  126 , the encryption information is transmitted as is left unchanged (corresponding to a transfer w 2  in  FIG. 11 ). 
     In the subsequent step  128 , the vehicle-mounted apparatus waits until it receives a signal from the on-road apparatus, and when the vehicle-mounted apparatus receives the signal (when the decision of step  128  is affirmative), in the subsequent step  130 , the on-road apparatus  10  and the IC card  62  are bypassed. Namely, the received signal from the on-road apparatus  10  is outputted to the IC card  62  in a state of being left unchanged, and the output signal outputted from the IC card  62  is transmitted to the on-road apparartus  10  in a state of being left unchanged (corresponding to the passing through the vehicle-mounted apparatus indicated by the transfer w 3  and w 4  in  FIG. 11 ). This received signal and output signal are encrypted, and therefore, they may be temporarily stored in the vehicle-mounted apparatus. 
     In the subsequent step  132 , it is determined whether the received signal includes an end signal in the form of a common sentence. When the signal does not include the end signal, the decision of step  132  is negative and the process returns to step  128 . When the signal includes the end signal, the decision of step  132  is affirmative, and in step  134 , bypassing of the on-road apparatus  10  and the IC card  62  is cancelled, and in the subsequent step  135 , the received utilization details for reception of tolls is indicated (corresponding to a process S 7  in  FIG. 11 ). 
       FIG. 10  shows a process of the IC card  62 ; it is determined whether a signal is inputted from the vehicle-mounted apparatus  30 . When a signal is not inputted, the decision of step  164  is negative and the decision of step  164  is made repeatedly. On the other hand, when a signal is inputted (corresponding to the transfer w 4  in  FIG. 11 ), the decision of step  164  is affirmative. In the subsequent step  166 , a signal inputted by decoding processing included in the security mechanism M is decoded (corresponding to a process S 8  in  FIG. 11 ). In the subsequent step  168 , it is determined whether the decoded signal is a read/write request given to the IC card  62 . 
     When the inputted signal cannot be decoded or when a request other than the read/write request is given, the decision of step  168  is negative. In the subsequent step  170 , a signal inputted from the vehicle-mounted apparatus is sent back in a state of being left unchanged, and thereafter, the process returns to step  164 . As a result, correspondence of an IC based on a plurality of different security mechanisms is made possible. On the other hand, when the process for the IC card  62  is the request for reading and writing date, the decision of step  168  is affirmative. In the subsequent step  172 , it is determined whether the request is that for writing, and when the request is that for writing data, the decision of step  172  is affirmative, and the process proceeds to step  174 . When the request is that for reading, the decision of step  172  is negative and the process proceeds to step  180 . 
     In step  174 , data is written in the memory  70  by the security mechanism M. For example, reception of tolls in which tolls that are decoded data from the on-road apparatus is charged with respect to the balance of charges for accounting and the resulting balance of charges (balance information) is written in the memory  70  (corresponding to a process S 9  in  FIG. 11 ). In the subsequent step  176 , the data written in the memory  70 , for example, the balance information and a toll-reception completion signal are encrypted by the securing mechanism M and are, in step  178 , outputted to the vehicle-mounted apparatus  30  (corresponding to the passing through the vehicle-mounted apparatus and outputting to the on-road apparatus indicated by the transfer w 4  in  FIG. 11 ). 
     In step  180 , data is read from the memory  70  by the security mechanism M. In the subsequent step  182 , the read data balance information, for example, is encrypted, and in step  178 , it is outputted to the vehicle-mounted apparatus  30 . 
     As described above, in the present embodiment, among information to be communicated between the on-road apparatus and the vehicle-mounted apparatus, information such as entrance information or route information, which has a high secrecy to prohibit alteration thereof, is used in a state of being left encrypted (in the form of encryption information) and the encrypted information is temporarily stored in the vehicle-mounted apparatus as it is. Accordingly, alteration of information such as entrance information or route information becomes difficult; therefore, the reliability of the information itself can be improved and the secrecy thereof can be maintained. 
     Further, in a case in which reading and writing is effected for an IC card in which user information regarding a user such as the balance of charges or the like is stored, when information is transferred using the encryption information encrypted by the security mechanism of the IC card itself and the information of the IC card is outputted via the vehicle-mounted apparatus which transmits and receives information to and from the on-road apparatus, or when the information from the on-road apparatus is inputted, the vehicle-mounted apparatus merely allows passing of the encrypted information and does not decode the information. Accordingly, information is not altered and the secrecy thereof can be maintained. 
     Moreover, the vehicle-mounted apparatus merely allows passing of the encryption information therethrough, and therefore, the vehicle-mounted apparatus does not need to provide processing for encryption or decoding. As a result, the structure of the vehicle-mounted apparatus is simplified and a calculation load of the vehicle-mounted apparatus can be reduced. 
     Further, in the road-to-vehicle communications, a two-way communication (optical communication or the like is also possible) is employed and the present invention can be applied thereto. 
     The above-described system can be applied to a road or a parking area for simple reception of tolls wherein a gate is not present. 
     Further, in the above-described system, there was described a case in which a vehicle-mounted apparatus includes neither a structure nor a process for encryption and decoding, but a common sentence-structured portion may be deleted by well-known general encryption. 
     Second Embodiment 
     Next, a second embodiment will be described. Further, this embodiment has substantially the same structure as that of the above-described embodiment, and therefore, the same members as those of the above-described embodiment will be denoted by the same reference numerals and detailed descriptions thereof will be omitted. 
     As shown in  FIG. 12 , an automatic toll receiving system of the present embodiment is structured to include the on-road apparatus  10  provided on the road side and the vehicle-mounted apparatus  30  mounted on a vehicle. Information is mutually transferred between the on-road apparatus  10  and the vehicle-mounted apparatus  30  by radio communications. An on-road apparatus communicating with the vehicle-mounted apparatus  30  includes antennas for transmitting and receiving various information and is disposed in each of an entrance gate of a toll road, a mid-route thereof, and an exit gate. The on-road apparatus  10  includes a memory  28  (see  FIG. 14 ) in which the electronic key A is stored, and the vehicle-mounted apparatus  30  includes the storage circuit  48  (see  FIG. 13 ) in which electronic keys A, B, and C are stored, as will be described in detail later. When information is mutually transferred between the on-road apparatus  10  and the vehicle-mounted apparatus  30  by radio communications, transmitted information is encrypted and received information is decoded, using the electronic key A. 
     The above-described encryption and decoding can be provided using a secret key encryption system (for example, Data Encryption Standard (DES)). 
     The IC card  62  (described in detail later) in which various information is stored is detachable from the vehicle-mounted apparatus  30 . Information is mutually transferred between the vehicle-mounted apparatus  30  and the IC card  62 . The IC card  62  includes the memory  70  (see  FIG. 15 ) in which the electronic key B is stored. When information is transferred between the vehicle-mounted apparatus  30  and the IC card  62 , transmitted information is encrypted using the electronic key B and received information is decoded. 
     The type of a vehicle on which the vehicle-mounted apparatus  30  is mounted or vehicle information such as an ID number may be written in the vehicle-mounted apparatus  30 . The vehicle information is written using an information writing device  76 . The information writing device  76  includes a memory  84  in which the electronic key C is stored (see  FIG. 15 ). When the vehicle information is transferred between the vehicle-mounted apparatus  30  and the information writing device  76 , the vehicle information is encrypted using the electronic key C and received information is decoded. 
     Next, the vehicle-mounted apparatus  30  and the on-road apparatus  10  communicating with the vehicle-mounted apparatus  30  will be described in detail. The present embodiment will be described with an on-road apparatus provided in the mid-route  200  being given as an example. Further, for simplifying explanation, the mid-route antenna  218  provided for radio communication with the vehicle  90  traveling along the lane  202  and the mid-route antenna control device  232  are used. A vehicle-mounted battery (not shown) is connected to the vehicle-mounted apparatus  30 . 
     Similar to the above-described embodiment, in the mid-route  200  of the present embodiment, the two lanes  202  and  204  are provided side by side. The arch  216  on which the route recognizing antennas  218 ,  220 , and  222  are disposed is provided between the ground  208  and the ground  214  in such a manner as to extend over the lanes  202  and  204 . (see  FIG. 2 ). 
     As shown in  FIG. 13 , the vehicle-mounted apparatus  30  includes the receiving antenna  32  for receiving a data signal transmitted from the on-road apparatus. The receiving antenna  32  demodulates a received modulated wave and is connected to a demodulation circuit  34  for obtaining the data signal. The demodulation circuit  34  can also obtain a carrier wave of an electric wave transmitted from the on-road apparatus and may be connected to the transmission circuit  50 . The demodulation circuit  34  is connected via the data signal receiving circuit  44  to the signal processing circuit  46  including a microcomputer. The microcomputer of the signal processing circuit  46  stores therein a processing program and the like, as will be described later. 
     The storage circuit  48  is connected to the signal processing circuit  46 . The storage circuit  48  in advance stores therein the electronic keys A, B, and C. Further, the information writing device  76  can be connected to the signal processing circuit  46  and information regarding a vehicle-mounted apparatus is stored in the storage circuit  48 . Namely, when the vehicle-mounted apparatus is mounted on a vehicle, a vehicle number (the number recorded on a number plate) serving as an ID code is stored in the storage circuit  48  by the information writing device  76  and information regarding the type of the vehicle on which the vehicle-mounted apparatus is mounted is also stored in the storage circuit  48 . Further, when the IC card  62  is inserted, information about the balance (such as information about the money left and the result of updating of the balance at the time that the IC card  62  is used within a service area at which the vehicle stops midway) of the IC card  62  is stored in the storage circuit  48 . Further, when the vehicle has passed through an entrance gate, a vehicle-type code detected at the entrance gate and entrance information (entrance number, date and time of passage of the vehicle, and the like) are stored in the storage circuit  48 . When the vehicle has passed through a mid-route (check barrier), check barrier information (check barrier number and date and time of passage of the vehicle) corresponding to the passed check barrier is stored in the storage circuit  48 . And when a communication error arises, communication error information (type of error, positions at which the error occurred (type of gate, gate number, antenna number, and the like), date and time of occurrence of the error, the number of times that an error occurs, and the like) or the like is stored in the storage circuit  48 . 
     The transmission circuit  50  for transmitting, as a response signal, a data signal including an ID code, and the like is connected to the signal processing circuit  46 . The transmission circuit  50  is connected to a transmission antenna  52 . The vehicle-mounted apparatus  30  modulates a carrier wave obtained by demodulating the modulated wave received at the receiving antenna  32 , based on a data signal from the signal processing circuit  46  and can send back the modulated carrier wave through the transmission antenna  52 . Meanwhile, the transmission antenna  52  is provided so as to function as a transmitting/receiving antenna. An unmodulated carrier wave transmitted from the on-road apparatus is received by the transmission antenna  52 , and thereafter, the unmodulated carrier wave may be modulated by the transmission circuit  50  based on the data signal from the signal processing circuit  46 , so as to be sent back via the transmission antenna  52 . 
     Further, the IC card read/write device  60  for reading data from the IC card  62  inserted therein and writing data into the IC card  62  is connected to the vehicle-mounted apparatus  30 . The limit switch  58  for mechanically detecting the insertion of the IC card  62  is provided in the IC card read/write device  60 . Whether the IC card has been inserted into the IC card read/write device  60  may be optically detected by determining, using a photo-interrupter composed of a light-emitting element and a light-receiving element disposed opposite each other, whether light is cut off by the inserted IC card. 
     The display  54  comprised of an LCD or CRT for displaying whether the IC card has been inserted, the balance, and the like thereon, and the ten key  56  for inputting a signal to the signal processing circuit  46  are each connected to the signal processing circuit  46 . 
     As shown in  FIG. 14 , the on-road apparatus for a vehicle traveling along the lane  202  is comprised of the mid-route antenna  218  and the mid-route antenna control device  232 . The mid-route antenna  218  is comprised of the transmission antenna  22  and the receiving antenna  26 . The mid-route antenna control device  232  has the signal processing circuit  12  including a microcomputer. The microcomputer stores therein a processing program which will be described later. The signal processing circuit  12  can be connected to a central computer  400  (not shown). The signal processing circuit  12  is connected to the transmission circuit  14  which generates a data signal including an instruction (a communication requesting signal). The transmission circuit  14  is connected via a mixer  18  to the transmission antenna  22 . A carrier wave generation circuit  20  which generates a carrier wave having a predetermined frequency is connected to the mixer  18 . The mixer  18  mixes a signal inputted from the transmission circuit  14  and a carrier wave inputted from the carrier wave generation circuit  20  and modulates the carrier wave inputted from the carrier wave generation circuit  20  with the signal inputted from the transmission circuit  14 . Further, the modulated wave is transmitted as a radio wave from the transmission antenna  22 . 
     Connected to the carrier wave generation circuit  20  is the receiving circuit  24  which fetches a data signal from the modulated wave modulated and sent back from the vehicle-mounted apparatus  30  and received by the receiving antenna  26 . The receiving circuit  24  is connected to the signal processing circuit  12 . Further, the receiving circuit  24  is connected to the carrier wave generation circuit  20  and a carrier wave transmitted for comparison of the carrier wave included in the signal sent back from the vehicle-mounted apparatus  30  is inputted thereto. 
     Other structures in the mid-route  200  are the same as the above-described ones, and therefore, descriptions thereof will be omitted. Further, respective antennas and antenna control devices at an entrance gate  100  and an exit gate  300  are substantially the same in structure as those referred to the above, and therefore, descriptions thereof will be omitted. 
     Further, in the above-described vehicle-mounted apparatus and on-road apparatus, an antenna comprised of the transmitting and receiving antennas separated from each other is used. However, a transmission/reception type antenna may be used. 
     As shown in  FIG. 15 , the IC card  62  which can be inserted in the vehicle-mounted apparatus  30  is comprised of a microcomputer including the CPU  64 , the RAM  66 , the ROM  68 , the memory  70 , and the input/output (I/O) port  72 , which are connected by the bus  74  so as to allow transfer of a command or data therebetween. The memory  70  is used for storage of the electronic key B and various information. Further, the ROM  68  stores therein a processing routine which will be described later. The input/output port  72  can be connected to the vehicle-mounted apparatus  30  or to the IC read/write device  60 . Further, although not illustrated, the IC card  62  is provided with a power source circuit so as to supply a power source constantly. 
     The above-described IC card can store, as various information, information regarding the vehicle-mounted apparatus such as a card number, balance information, information about utilization details (entrance gate number, exit gate number, toll, date and time of utilization, and the like), and also can store a certified key code for having a card correspond to the vehicle-mounted apparatus, namely, recording the electronic key B. 
     Further, there can be used, as the IC card, various cards, for example, a memory card such as an LSI card, a magnetic card, a hologram card on which information can be optically recorded and reproduced, or a magneto-optical card on which information can be magneto-optically recorded and reproduced. 
     The information writing device  76  for writing the information regarding the vehicle-mounted apparatus in the above-described vehicle-mounted apparatus  30  can be connected to the vehicle-mounted apparatus  30  and is comprised of a microcomputer including a CPU  78 , a RAM  80 , a ROM  82 , a memory  84 , and an input/output (I/O) port  86 , which are connected by a bus  88  so as to allow transfer of a command or data. The memory  84  is used for storage of the electronic key C and various information. The ROM  82  stores therein a processing routine, which will be described later. The input/output port  86  can be connected to the vehicle-mounted apparatus  30 . 
     Next, an operation of the present embodiment will be described. 
     First, a process for writing vehicle information in the vehicle-mounted apparatus  30  will be described. 
       FIG. 16  shows a process routine in the information writing device  76  for writing vehicle information in the vehicle-mounted apparatus  30 . When the process is executed, in step  200 , vehicle information such as the type of vehicle on which the vehicle-mounted apparatus  30  is mounted, an ID number, and the like, which is to be written in the vehicle-mounted apparatus  30 , is set. In the subsequent step  202 , the electronic key C is read and the set vehicle information is encrypted by the electronic key C. In the subsequent step  204 , the encrypted vehicle information is outputted to the vehicle-mounted apparatus  30  (see an output C 1  in  FIG. 21 ). The information writing device  76  thus encrypts the vehicle information to be outputted and maintains the secrecy of the information. 
       FIG. 17  shows a process routine of the vehicle-mounted apparatus when the vehicle information is written therein. In step  206 , the vehicle-mounted apparatus waits until information is inputted thereto, and when information is inputted, in step  208 , the electronic key C is read and the inputted information is decoded by the electronic key C. In the subsequent step  210 , it is determined whether the decoded information is the vehicle information. When the decoded information is not the vehicle information, it is determined that other processing is effected or false information is given (when the decision of step  210  is negative), and the present routine ends. On the other hand, when the decoded information is the vehicle information (when the decision of step  210  is affirmative), in step  212 , the decoded vehicle information is written in the storage circuit  48 . As described above, in the vehicle-mounted apparatus  30 , the encrypted information is decoded and it is determined whether the decoded information is the vehicle information. Accordingly, there is no possibility of the inputted information being incorrectly written in the vehicle-mounted apparatus. 
     Next, intercommunication processing between the on-road apparatus and the vehicle-mounted apparatus will be described. 
       FIG. 18  shows in detail communication processing of the vehicle-mounted apparatus. In step  214 , the vehicle-mounted apparatus waits until it receives a signal from the on-road apparatus (see a transfer A 1  in  FIG. 23 ). When the vehicle-mounted apparatus receives the signal (when the decision of step  214  is affirmative), in the subsequent step  216 , the electronic key A is read and the received signal is decoded by the electronic key A. In the subsequent step  218 , it is determined whether the decoded signal is an inquiry signal. When the decoded signal is not an inquiry signal, the decision of step  218  is negative, and the process returns to step  214 . When the decoded signal is an inquiry signal, the decision of the step  218  is affirmative and the process proceeds to step  220 . 
     In step  220 , the electronic key A and the vehicle information (for example, an ID code such as an identification code which specifies a vehicle), and the vehicle information is encrypted by the electronic key A. In the subsequent step  222 , with the received inquiry signal being used as a carrier wave, a modulated wave wherein the carrier wave is modulated with the encrypted vehicle information is transmitted as an inquiry signal (a transfer A 2  in  FIG. 23 ). 
     Next, in step  224 , the vehicle-mounted apparatus waits until it receives a signal from the on-road apparatus (a transfer A 3  in  FIG. 23 ). When the vehicle-mounted apparatus receives the signal (when the decision of step  224  is affirmative), in step  226 , the received signal is decoded by the electronic key A. In the subsequent step  228 , by determining whether the decoded signal includes entrance information, it is determined whether the vehicle is presently passing the entrance gate. When the vehicle is not passing the entrance gate (when the decision of step  228  is negative), the process proceeds to step  230 . When the vehicle is passing the entrance gate, in step  232 , entrance gate processing (the transfer A 4  to An in  FIG. 23 ) is executed. In this entrance gate processing, in step  506 , the entrance information which is an entrance gate number included in the received signal is stored in the storage circuit  48  of the vehicle-mounted apparatus  30 . 
     In step  230 , based on a determination as to whether the decoded signal includes a mid-route code (check barrier information), it is determined whether the vehicle has passed the mid-route  200 . When the vehicle has passed the mid-route  200  (when the decision of step  230  is affirmative), in step  234 , mid-route processing is executed. When the vehicle has not passed the mid-route  200  (when the decision of step  230  is negative), it is determined that the vehicle has passed an exit gate, and in step  236 , exit gate processing is executed. 
     In this mid-route processing, mid-route information based on a mid-route code included in the decoded signal is stored in the storage circuit  48  of the vehicle-mounted apparatus  30 . Further, in the exit gate processing of step  514 , based on information regarding the type of vehicle stored in the vehicle-mounted apparatus, balance information stored in the IC card mounted in the vehicle-mounted apparatus, and a toll table recorded in advance in the vehicle-mounted apparatus, tolls charged on a route from the entrance gate to the exit gate with the mid-route located therebetween are calculated from the present balance, and the charged tolls are automatically collected. After the tolls have been normally collected, entrance information is cleared. In the mid-route processing or in the exit entrance processing, transfer of information indicated by the transfer A 4  to An shown in  FIG. 23  is carried out in accordance with the number of processes. The transfer of information to the IC card will be described later. 
     As shown in  FIG. 19 , in step  238 , an on-road apparatus located in a mid-route reads the electronic key A and encrypts an inquiry signal by the electronic key A. In the subsequent step  240 , the on-road apparatus transmits the encrypted inquiry signal (see the transfer A 1  in  FIG. 23 ). 
     Subsequently, the on-road apparatus transmits the encrypted inquiry signal until it receives the response signal from the vehicle-mounted apparatus  30 , and in the subsequent step  242 , it is determined whether the on-road apparatus has received the signal from the vehicle-mounted apparatus  30 . When the on-road apparatus has received the signal, the decision of step  242  is affirmative, and in the subsequent step  244 , the signal is decoded using the electronic key A. When the on-road apparatus has not received the signal (when the decision of step  242  is negative), the process returns to step  238 . 
     In the subsequent step  246 , it is determined whether the decoded signal is a response signal. When it is the response signal (when the decision of step  246  is affirmative), in step  248 , gate information, in this case, mid-route information is encrypted using the electronic key A. In the subsequent step  250 , the on-road apparatus transmits a signal including the encrypted mid-route information and the like (see the transfer A 3  in  FIG. 23 ). 
     Meanwhile, in the on-road apparatus at the entrance gate, substantially the same process as the above-described one is executed, but the on-road apparatus transmits, in place of the signal including the mid-route information and the like, a signal including an entrance gate number, which represents the entrance gate, and the like. Further, in the on-road apparatus at the exit gate  300  as well, substantially the same process as the above-described one is executed, but the toll receiving processing may be executed by a signal including an exit code representing an exit gate, and the like or by radio communications. 
     In the transfer of a signal between the above-described on-road apparatus  10  and the vehicle-mounted apparatus  30 , information is decoded by the electronic key A. Accordingly, the information transferred between the on-road apparatus  10  and the vehicle-mounted apparatus  30  maintains secrecy, and the security to the interception of information can be improved. 
     Next, a process for the transfer of information between the IC card  62  and the vehicle-mounted apparatus  30  will be described. In the following, processing in the IC card read/write device  60  connected to the vehicle-mounted apparatus  30  will be described, and the present invention can also be applied to a case in which an IC card read/write device is independently located at a recovery gate or the like. 
       FIG. 20  shows a process in the IC card  62 . In step  252 , it is determined whether a signal is inputted from the vehicle-mounted apparatus  30 . When a signal is not inputted, the decision of step  252  is negative and the decision of step  252  is made repeatedly. On the other hand, when a signal is inputted (see a transfer B 1  in  FIG. 22  and the transfer B 1  in  FIG. 23 ), the decision of step  252  is affirmative, and in step  254 , the IC card reads the electronic key B and decodes the inputted signal by the electronic key B. In the subsequent step  256 , it is determined whether the decoded signal is a read/write request given to the IC card  62 . When the inputted signal is a request other than the read/write request, the decision of step  256  is negative, and the process returns to step  252 . On the other hand, when the process effected for the IC card  62  is the request for reading and writing, the decision of step  256  is affirmative. In the subsequent step  258 , it is determined whether the request is that for writing. When the request is that for writing data, the decision of step  258  is affirmative, and the process proceeds to step  260 , and when the request is that for reading data, the decision of step  258  is negative, and the process proceeds to step  266 . 
     In step  260 , a request for output of data is given to the vehicle-mounted apparatus  30  (see a transfer B 2  in  FIG. 22  and a transfer B 2  in  FIG. 23 ), and the data is inputted to the IC card. The inputted data is decoded in step  262  and the decoded data is written in the memory  70  in step  264 . 
     In step  266 , the data stored in the memory  70  is read, and in the subsequent step  268 , the data is encrypted by the electronic key B. In step  270 , the data is outputted to the vehicle-mounted apparatus  30  (see the transfer B 2  in  FIG. 22  and the transfer B 2  in  FIG. 23 ). 
     Accordingly, the information transferred between the vehicle-mounted apparatus and the IC card is allowed to maintain secrecy so as to improve the security with respect to the interception of the information. 
     As described above, in the present embodiment, at the time of communication of information between the on-road apparatus and the vehicle-mounted apparatus and in the transfer of information between the vehicle-mounted apparatus and the IC card or between the vehicle-mounted apparatus and the information writing device, the information is encrypted or decoded using different electronic keys. For this reason, even when the secrecy of one electronic key leaks out, disclosure of the secrecy of a system can be kept to a minimum. Accordingly, the reliability of data held by each system can be improved and the load of each system can be reduced by the secrecy which is based on a small number of electronic keys. 
     Meanwhile, the above-described system can be applied to a toll road of a simple toll collecting system, or a parking area, wherein a gate is not present. For this reason, this system can be used only for reception of tolls or transfer of simple information such as parking time, time for passage, and the like, and the system of the present embodiment can easily be applied. 
     The above-described process routine may be executed using a floppy disk (FD) serving as a recording medium without being stored in a memory or ROM of each of the on-road apparatus and the vehicle-mounted apparatus. In this case, in the on-road apparatus, a floppy disk unit (FDU) in which a floppy disk can be removably inserted may be connected to an input/output port of the signal processing circuit  12  or the like, and in the vehicle-mounted apparatus, a floppy disk unit (FDU) in which a floppy disk can be removably inserted may be connected to an input/output port of the signal processing circuit  46  or the like. As a result, the above-described process routine or the like can be read out and written in a floppy disk using the FDU, and a program can be recorded in advance in the floppy disk without being stored in a ROM or the like, and the processing program recorded in the floppy disk via the FDU can be executed. Further, in place of the FDU, a mass storage (not shown) such as a hard disk device is connected to the input/output port and the processing program recorded in the floppy disk may be executed by being stored (installed) in the mass storage (not shown). Further, as the recording medium, an optical disk such as a CD-ROM, or a photo-magnetic disk such as an MD, MO, or the like is provided. When these disks are used, a CD-ROM device, an MD device, an MO device, or the like may be used in place of or in addition to the above-described FDU. 
     INDUSTRIAL APPLICABILITY 
     As described above, the vehicle-mounted communication device and road-to-vehicle communication device according to the present invention are suitably used for the vehicle-mounted communication device mounted on a vehicle and for the road-to-vehicle communication device in which communication processing is effected between the vehicle-mounted communication device and an on-road apparatus located on the road side, and are, for example, applied to an automatic toll receiving system for automatically receiving a toll for a vehicle running on a toll road or the like or a vehicle parked in a toll parking area.