JPS61156972A - Interception preventing communication system - Google Patents

Abstract

PURPOSE:To effectively prevent an interception even by variously changing a cryptograph number capable of being set externally by setting a cipher key referring to the cryptograph number set by a receiving side without performing only by a fixed code of a previously set cipher. CONSTITUTION:When carrying out a facsimile transmission from a center to a certain car, if a communication preparing indicating signal is outputted, this is transmitted to respective cars from a transmitting section 9 through a radio. A receiving section 20 of the car addressed by this communication preparing indicating signal receives it, outputs communication preparing completion signal, and it is transmitted through a transmitting section 19. In this communication preparing completion signal, a cryptograph number is included and simultaneously transmitted. to a cipher key signal judging circuit 6, a fixed code for the transmission part and the cryptograph number returned from the transmission part are transmitted. Based on these, a cipher table 6-1 is subjected to an access and the cipher key determined by a combination of the fixed code and the cryptograph number is outputted.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an eavesdropping prevention method for mobile radio communications.

In particular, the present invention relates to a system in which an image signal is encoded and transmitted in accordance with an encryption key signal from the recipient side.

[Conventional technology]

For example, as shown in FIG.
．． 32 are communicating.

By the way, recently there have been cases in which one private taxi vehicle is sent image data such as a map at 7 axmire to pick up and drop off passengers, but in such cases, even if the contract is for a specific vehicle, other taxis may It is necessary to prevent vehicles from intercepting customers, and means to prevent wiretapping of video signals is required.

Therefore, when sending an image signal from the center 30 to a specific car, it is assumed that, as shown in FIG. After that, you will receive a unique PIN number for that car, which you have registered in advance at the center. On the receiving side, the personal identification number transmitted from the center is compared with the own personal identification number, and if they match, for example, the receiving side turns on the gate and receives the image signal.

[Problem that the invention seeks to solve]

By the way, since the setting of the unique password on the receiving side is done by inputting an external password, it is possible to change it at will. Therefore.

If an image signal is sent to the owner of the changed PIN, it can be received, so a highly accurate eavesdropping prevention method is required.

[Means for solving problems]

The above problems have been solved. In order to provide a more accurate wiretapping prevention method, the wiretapping prevention communication method of the present invention includes a transmission data generation means for outputting transmission data, and an interleap encoding method for changing the order of the signals output from the transmission data generation means. In the wiretapping prevention communication system, the center is equipped with a decoding circuit for restoring interleaved received signals to prevent wiretapping of wireless communication between a center equipped with a decoding circuit for restoring interleaved received signals, and multiple slave stations. The slave station is equipped with a communication control receiving circuit that receives the transmitted PIN number, an encryption key signal and a determination circuit that outputs the cipher key according to the PIN number, and a communication control circuit that sends the PIN number to the center. a control signal transmission circuit; a cryptographic key signal determination circuit that outputs a cryptographic key according to the password; and a decryption circuit that restores the order of received signals transmitted from received data based on the cryptographic key by the interleave decoding circuit. It is characterized by comprising an output circuit that outputs a signal.

[Effect]

As a result, the υ center encrypts and sends the transmitted data using a PIN code that corresponds to the code of the communication destination's car held by the center and the PIN code sent from the communication destination car. Even if another car changes its password without permission, it cannot be eavesdropped on.

〔Example〕

Before describing the present invention in detail using one embodiment, its outline will be explained with reference to FIG.

In the present invention, as shown in FIG. 2(a), a communication preparation instruction signal is first sent from the center to the destination vehicle. Of course, this communication preparation instruction signal includes an address.

When receiving this communication preparation instruction signal, the receiving side completes reception preparations and returns a communication preparation completion signal, as well as the vehicle's PIN number. In Figure 2 (al), the upper signal shows the signal sent from the center to each car (8-, R), and the lower signal shows the signal sent from each car to the center (S-R). ) is shown.

The center stores a unique code for each vehicle in advance, and uses the combination of this unique code and the PIN number returned by the communication ready signal to access a pre-prepared code table and encrypt the code. The key is read out, and the image signal is encrypted using the encryption key and transmitted. By the way, on the receiving side, the above-mentioned cipher table is prepared in which the cipher key to be used can be obtained by combining the unique code (previously set in the device, cannot be set externally) and the PIN number. Therefore, an encryption key for encrypting the image signal can be obtained, so that the encrypted image signal can be decoded.

After the reception of the image signal is completed in this manner, a reception completion signal is sent back to the center to complete the communication.

By the way, as the above-mentioned encryption, for example, the following can be done. In other words, as shown in Figure 2 (bl).

Divide one page of transmission screen into multiple sections dO, d1, etc.

Each section is divided into, for example, 32 parts. Then, the transmission order of the sections 1 to 32 is changed to the section d/ in FIG.
Prepare multiple transmission order conversion buttons P1 to Pa,
By decoding the received signal based on this transmission order conversion pattern, correct image signals can be transmitted and received. FIG. 2 (bl is an example of the transmission order conversion pattern P1 corresponding to the encryption key Ks. Therefore, by selecting this transmission order conversion pattern according to the combination of the unique code and the PIN number, wiretapping can be effectively prevented. In addition, there is a problem in that radio communication signals have fading, which causes strength and weakness in the received signal, so if a weak signal part continues for a long period of time, many errors are likely to occur, but converting the transmission order in this way is more C9
This also improves the drawback that the weak signal portion continues for a long period of time.

In order to carry out such communication, as shown in FIG.
d1. d, . . . and each section is divided into, for example, sections 1 to 320, and the order is converted into an order determined by the encryption key and transmitted. On the receiving side, an encryption key decoding circuit 21 and an image data order conversion circuit 22 are provided, which decode the partition order in which the image data is transmitted based on the encryption key used, and convert the image data according to the decrypted partition order. By converting the partition order.

The correct image signal can be restored without being intercepted.

An embodiment of the present invention will be described based on FIG. 1 and with reference to a map.

In Fig. 1, 1 is a center facsimile transmitter;
Reference numeral 2 denotes a center radio device having a transmitting section 9 and a receiving section 1O, and 3 a communication control signal transmitting circuit which outputs a transmission procedure signal of a protocol necessary for facsimile 1 communication.

For example, as shown in FIG. 2(a), 1 outputs a communication preparation instruction signal, and 4 is a communication control signal receiving circuit that receives the transmission procedure signal of the protocol. As shown in 9, those that receive the communication ready signal (including the PIN number) or receive the reception completion signal,
Reference numeral 5 represents a unique code table in which a fixed code unique to a vehicle device that communicates with the center is entered; 9 is a device that outputs a fixed code based on, for example, the vehicle number; 6 is an encryption key signal determination circuit; It has a cryptographic table 6-1 which outputs a cryptographic key to be applied based on a fixed code and a password, and specifies an interleave encoding mode based on the widely read cryptographic key.

7 is a transmission data generation circuit which reads a transmission document and converts it into an electrical signal; 8 is an interleave encoding circuit which converts the image data transmitted from the transmission data generation circuit 7 into, for example, FIG. It can be divided into sections 1 to 32 like section 4 in (b).

The transmission order of the divided image data is transmitted based on a transmission order conversion pattern determined according to the encryption key, and an example of the transmission order conversion button 01 is shown in section d of FIG. 2 (bl). The interleave encoding circuit 8 has transmission order conversion patterns P1.
P! ... is prepared, and one transmission order conversion pattern 01 is selected based on the encryption key transmitted from the encryption key signal determination circuit 6.

11 is an in-vehicle facsimile receiver, 12 is an in-vehicle radio device that is the same as the 7-axis receiver and has a transmitting section 19 and a receiving section 20, and 13 is a communication control signal receiving circuit, as shown in FIG. (a) A device for detecting that a communication preparation instruction signal has been received from the center; 14 is a communication control signal transmitting circuit; when the communication control signal receiving circuit 14 receives a communication preparation instruction signal transmitted from the center; 2 to a control unit (not shown) and correspondingly outputs a communication ready signal shown in FIG. 2 (al).
Reference numeral 15 denotes a password designation circuit for setting the vehicle's password.This password is not only included in the communication preparation completion signal and sent to the center, but also sent to the encryption key signal determination circuit 18, which will be described later. 16 is an interleave decoding circuit which decodes the received image signal according to the encryption key. Therefore, order conversion buttons R, R... If an encryption key tag is used, as shown in Figure 2 (bl), the first receiving section of each section is Send the first part of the manuscript
The second receiving section is restored to the 14th section of the transmitted document, the third receiving section is restored to the 29th section of the transmitted document, and so on. Interleave decoding processing is performed by conversion button P1. Naturally, the order conversion button for transmission and the order conversion button for decryption are the same for the same encryption key.

Reference numeral 17 denotes a received data recording circuit which receives the received signal decoded by the interleave decoding circuit 16 to a recording head and outputs an image onto recording paper.

Reference numeral 18 denotes an encryption key signal determination circuit which, like the encryption key signal determination circuit 6 in the facsimile transmitter 1, has a cryptographic table 18-1, and has a fixed code unique to the on-vehicle facsimile receiver and a password designation circuit 15. One that outputs the encryption key to be used according to the set password and specifies the interleave encoding mode based on this,
This specifies the order conversion button for Tamashi decoding.

An example of the interleave encoding circuit 8 and interleave decoding circuit 16 is shown in FIGS. 5(al) and 5(bl), respectively.

When performing interleaved coding, the reading circuit 50 and the second
Data as shown in do in FIG. 5(b) is held in the RAM 51. At this time, the address conversion ROM 54 is designated with an interleap encoding mode, for example, as shown in FIG. , 2, 3, etc., and sequentially writes the data transmitted from the reading circuit 50. However, when reading this, even if the address counter 53 outputs 1, 2, 3, and so on sequentially, , the address conversion ROM 54 is 1.14, 29.
31..., so the selector 52 uses the converted address output from the address conversion ROM 54 to select 9R.
Read the data from AM51. At this time, selector switch S
Since Wo is connected to the RAM 51 side, the transmitter 51
From there, interleaved data is output as shown by D' in FIG. 2 (bl).

When receiving interleaved data in this way, the receiving side knows in advance which interleaving mode will be used, so it uses the address conversion ROM 60.
Specify the interleaving code mode accordingly. When receiving data, the changeover switch SWI is connected to the receiving section 56 side.

The received data is sequentially transmitted to the RAM 57. At this time, the address counter 59 sequentially outputs addresses 1, 2.3, . . . , but these are converted into addresses 1, 14, 29, . With this, 9RAM57 has a second
The received data is written in the decoded order as shown in D in the figure (bl). After the division d3 is written to the RAM 57 in this way, the selector 58 then selects the address 1, which is output from the address counter 59, 2.3...
9RAM57 is read.

The data decoded in this way is stored in the received data storage circuit 6.
1.

Next, the operation of the present invention will be explained.

(1) When transmitting a facsimile from the center to a certain car, the selector switch SWo of the facsimile transmitter 1 at the center is connected to the communication control signal sending circuit 3 side, and when the facsimile receiver 11 mounted on the car is waiting for reception. The changeover switch SW1 is connected to the communication control signal receiving circuit 13 side. In this state, the communication control signal sending circuit 3 of the center is activated.

As shown in FIG. 2 (al), when a 2 communication preparation instruction signal is output, this signal is wirelessly transmitted from the transmitter 9 to each vehicle.

(2) The receiving unit 20 of the car addressed by this communication preparation instruction signal receives it, and its communication control signal receiving circuit 13 decodes it and reports it to a control unit (not shown), and also responds to this signal. In response, the communication control signal transmitting circuit 14 outputs a communication preparation completion signal shown in FIG. The vehicle's PIN number is included, and this PIN number is also sent to the center.When the communication ready signal is being sent in this way, the changeover switch SWI is switched to the interleave decoding circuit 16. can be switched to the side.

(3) When the reception unit 10 at the center receives this communication preparation completion signal, the changeover switch SWo is connected to the interleave encoding circuit 8 side. By the way, the communication control signal receiving circuit 4 of the center notifies the control unit (not shown) that the communication preparation completion signal has been returned from the other party, and also outputs the returned password to the encryption key signal determining circuit 6. . By the way, since the center knows the destination car, it also outputs the address for that car (for example, the car number) to the unique code table 5. As a result, a fixed code specific to the facsimile receiver of the destination party is read from the unique code table 5, and this fixed code is also output to the encryption key signal determination circuit 6.

(4) In this way, the fixed code of the destination and the password returned from the destination are transmitted to the encryption key signal determination circuit 6, and based on these, the encryption table 6-1 is accessed and the fixed code and the password are accessed. For example, 1 is output as the encryption key determined by the combination of the passwords. This encryption key is transmitted to the interleave encoding circuit 8. Therefore, the interleaving encoding circuit 8
Based on the transmission order conversion button P1 corresponding to the transmission order conversion button P1, the image signal transmitted from the transmission data generation circuit 7 is encrypted and transmitted to the transmission section 9.

(5) By the way, the in-vehicle facsimile receiver on the receiving side also transmits its unique code and the above-mentioned password to the encryption key signal determination circuit 18, and obtains 1 as the encryption key to be used from the encryption table 18-1. 1 is transmitted to the interleave decryption circuit 16 as the encryption key for decryption. Therefore, the encrypted image signals sequentially received by the receiving section 20 are decoded by the interleap decoding circuit 16, and the received data recording circuit 17 restores the image onto the recording paper.

In this way, according to the present invention, the interleaving control of the image signal can be performed based on the receiving side's password, so that the confidentiality can be greatly improved.

In the above description, the example of a personal taxi has been explained, but the invention is of course not limited to this, and can also be used to prevent eavesdropping on facsimiles in other fields.

〔Effect of the invention〕

According to the present invention, encryption is not performed using only a predetermined fixed code, but the encryption key can also be set by referring to the PIN set on the receiving side, so the PIN can be set externally. Even if an attempt is made to eavesdrop by changing the information in various ways, this can be very effectively prevented.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention, FIG. 2 is an explanatory diagram of the operation of the present invention, FIGS. 3 and 4 are explanatory diagrams of a conventional device, and FIG. 5 (al is an interleap encoding circuit. fbl is an interleap decoding circuit. In the figure, 1 is a center facsimile transmitter, 2 is a center radio, 3 is a communication control signal transmitting circuit. 4 is a communication control signal receiving circuit, 5 is a unique code table,
6 is an encryption key signal determination circuit, 7 is a transmission data generation circuit,
8 is an interleap encoding circuit, 9 is a transmitter, 10 is a receiver, 11 is an on-vehicle facsimile receiver, 12 is an on-vehicle radio, 13 is a communication control signal receiving circuit, and 14 is a communication control signal transmitting circuit. 15 is a password designating circuit, 16 is an interleave decoding circuit, 17 is a received data recording circuit, 18 is an encryption key signal determining circuit, 19 is a transmitter, and 20 is a receiver.

Claims (1)

[Claims] 1. Restore the interleaved received signal with a center including a transmission data generation means for outputting transmission data and an interleave encoding circuit for changing the order of the signals output from the transmission data generation means. In an anti-wiretapping communication system that prevents wiretapping of wireless communications between a plurality of slave stations equipped with a decryption circuit, the center includes a communication control receiving circuit that receives a password transmitted from the slave stations; Equipped with an encryption key signal determination circuit that outputs an encryption key according to the PIN number, and the slave station has a communication control signal transmission circuit that sends the PIN number to the center and outputs an encryption key according to the PIN number. and an output circuit that outputs a decrypted signal obtained by restoring the order of received signals transmitted from received data based on the encryption key by the interleave decryption circuit. Eavesdropping prevention communication method. 2. The wiretapping prevention communication according to claim 1, wherein the encryption key signal determination circuit provided in the center and the slave station outputs the encryption key based on the personal identification number and fixed code. method.