JPS61228744A - Privacy call communication system - Google Patents

Abstract

PURPOSE:To attain the processing of encipherment and decoding in high speed by providing a means changing timewise a synchronizing code representing the start/end of a frame being the unit of sent information and a means disabling the mixture of the synchronizing code and the information in other frame. CONSTITUTION:Random number generators 30, 150 and memories 50, 130 are added to a data terminal equipment is a communication line to add the processing such as addition, deletion of the start/end flag sequence of a frame and disabled mixture between the flag sequence and other bit pattern in the frame to data terminal equipments 10, 170. Then a flag sequence corresponding to each flag control number, a bit inserting location and a bit pattern are stored in the memories 50, 130, a signal is sent from the data terminal equipment 10 and received by the data terminal equipment 170, then the flag sequence, bit inserting location and bit pattern in response to the flag control number are inputted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a secure communication system for preventing data interception and digitization in a communication line.

[Background of the invention]

As a conventional secret communication method, Japanese Patent Application Laid-Open No. 54-49002
However, this method transmits information while changing the code conversion method of the information using a program that can be changed sequentially. However, this method encrypts the entire information, making the device complicated. There was a problem that high-speed processing was not possible.

In addition, there is a method in which the entire information is not encrypted, and there is a method disclosed in Japanese Patent Application Laid-Open No. 54-52904, but this method is a method in which only the synchronization code is kept secret, and the synchronization code and transmission information as shown in this patent are It does not have a function to prevent confusion between
For this reason, if only the synchronization code is detected, the rest of the information becomes information that is not concealed at all.

Therefore, there is no function to hide the information itself, and it is a secret communication method mainly for analog signals.

In the future, with the development of satellite communication technology and optical communication technology, communication speeds will increase, and as a result, the need for encryption methods that can be applied to high-speed lines, which was difficult to use with conventional technology, will increase. Conceivable.

[Purpose of the invention]

An object of the present invention is to realize a secure communication system that can perform high-speed processing by concealing information without going through complicated processing steps.

[Summary of the invention]

In order to achieve the above object, the present invention provides the following features:
By changing the synchronization code to indicate the end of the frame over time, and adding a function to prevent the synchronization code from being confused with other data, we make it difficult to identify the frame.
This is to conceal information and detect quantity.

[Embodiments of the invention]

FIG. 1 shows an embodiment of a secure communication system according to the present invention.

First, in FIG. 1, the basic configuration and operation similar to those of a conventional communication line will be briefly explained. The data terminal devices 10 and 170 are devices located at the point of contact between the data communication system and the user, and are computers, terminal devices, etc. that input and output information.

The information is transmitted by signal transmission cables 70, 110 and input to data line termination devices 80, 100. The data line termination devices 80 and 100 have the function of converting and transmitting signals from the data terminal devices, due to reasons such as the distance between the data terminal devices 10 and 170. The signal converted by the data terminal equipment is
The signal is transmitted through the signal transmission cable 90 and communication is established.

The present invention is an international
Organization for 5 standards
OS I (Open
In the transmission procedure corresponding to the data link layer in the SystemInterconnection reference model,
It can be applied to most communication lines as long as transparency is guaranteed. However, here, based on the communication line shown in FIG.
An example will be explained in which 0 is a computer, signal transmission cables 70 and 110 are for baseband transmission, data line termination devices 80 and 100 are for modems, and signal transmission cable 90 is for broadband transmission.

In addition, as an example, the network architecture is based on the ISO O8I reference model, and in order to achieve confidentiality, the data link layer is HDLC.
A case in which a procedure with new functions added is adopted will be explained.

The basic idea of the present invention is to prevent the interception and quantity of information by making it difficult for a third party to identify, change, or create a flag sequence to distinguish each frame. It is.

In this embodiment, information is transmitted using the frame format shown in FIG.
: 8 bits, flag control sequence 210 : 8 bits, address sequence 220 : 8 bits, control sequence 230 : 8 bits, information sequence 240 :
Arbitrary bits, frame check sequence 250:1
6 bits, flag sequence 260: 8 bits.

Here, it can be seen that by removing the flag control sequence 210 from the above frame format, it becomes the same as the basic frame format of the HDLC procedure. Therefore, the functions of each sequence other than the flag sequence are similar to those in the HDLC procedure.

Next, to facilitate the explanation of this embodiment, a method for detecting the start and end of a frame in the HDLC procedure will be described.

Among the frame formats in the HDLC procedure,
Flag sequences 200 and 260 are sequences indicating the start and end of each frame, and are '01111110'.
It is represented by a bit pattern. Therefore '0
By simply monitoring the bit pattern 1111110', it is possible to detect the start and end of a frame. However, '0' is also used in places other than the flag sequence.
Since there is a possibility that a bit pattern 111110' may appear, in order to prevent the bit pattern from being mistakenly detected as a flag sequence, on the receiving side, five consecutive '1' bits must appear in locations other than the flag sequence. In this case, the next IO1 bit is inserted to prevent mixing with the flag sequence. In addition, when reading the transmitted information after detecting the start and end of a frame, the
The original state can be restored by removing the 0' bit.

By the above method, it is possible to transmit information of any bit pattern. However, with such methods, it is possible for a third party to detect the start and end of a frame simply by monitoring the flag sequence, making it easy to intercept and quantify the data. Put it away.

Therefore, in this embodiment, in order to avoid confusing the bit pattern of the flag sequence with the flag sequence, the bit pattern to be inserted and its insertion position are changed for each frame, thereby making it difficult to intercept and quantify the data.

Specifically, by transmitting information on the flag sequence pattern and bit pattern to be inserted using the flag control sequence 210 of the frame format shown in FIG. 2, the flag sequence and bit pattern to be inserted are controlled for each frame. Make changes.

However, in this example, only the basic signal processing method is explained and additional functions are omitted, so -
The start flag sequence within a frame has the same bit pattern as the end flag sequence of the previous frame. This point can be changed depending on where the flag control sequence is inserted within the frame.

Next, an explanation will be given using a specific device as an example. As shown in FIG. By adding to the data terminal device 10, 170 measures for adding and deleting the start/end flag sequence and for not mixing the flag sequence with other bit patterns in the frame, as shown in FIGS. It will be done.

Here, in order to facilitate understanding, only the case where data is transmitted from the data terminal device 10 and received by the data terminal device 170 in FIG. 1 will be explained.
Even in the reverse case, communication is possible in the same way, and therefore application to full-duplex communication is also possible.

First, data is transmitted by adding the data processing flow shown in FIG. 3 to the functions of a conventional data terminal device.

First, 5 TART is performed by transmitting data.

In block 300, the start flag sequence '01111110' is transmitted only in the first frame.

At block 310, a flag control number is input from the random number generator 30 (which generates random numbers from 1 to 256).

In block 320, the flag sequence, bit insertion location, and bit pattern corresponding to the flag control number are input from the memory 5o.

Note that the memories 50 and 130 contain the following information as shown in FIG.
It is assumed that the flag sequence, bit insertion location, and bit pattern corresponding to each flag control number are stored.

At block 330, a flag control sequence, which is information regarding the flag control number, is transmitted. At this time, by transmitting the flag control number in encrypted form, it is possible to make data interception and quantity even more difficult.

In block 340, it is determined whether a bit insertion portion exists in a portion other than the flag sequence. If a bit insertion location exists, a bit pattern corresponding to the bit insertion location is input at block 350.

Block 360 transmits all information except the flag sequence.

At block 370, the flag sequence input from the memory at block 320 is transmitted as an end flag sequence.

In block 380, it is determined whether or not to end the data transmission, and if it is to end, the next frame is not transmitted and is END. If further data transmission is to be continued, block 390 transmits the same sequence as the end flag sequence as the start flag sequence. In this case, if data is transmitted continuously, either the start or end flag sequence may be omitted.

Next, a reception method performed by the data terminal device 170 will be explained.

In the case of reception, as shown in FIG.
The start flag sequence '01111110' is detected.

At block 410, the start flag sequence is removed.

In block 420, a flag control sequence is detected and a flag control number is determined.

In block 430, the flag sequence, bit insertion location, and bit pattern corresponding to the flag control number are input from the memory 130. Here, memory 50, 130
It is assumed that the same data is entered in .

At block 440, a determination is made whether an end flag sequence has been detected.

If the end flag sequence has not been detected, block 460 determines whether a bit insertion point has been detected, and if so, block 470 determines whether the next bit pattern (from memory in block 430) is detected. input).

If the bit insertion point is not detected in block 460, or after the processing in block 470 is completed, block 440 again judges whether the end flag sequence is detected.

If a termination flag sequence is detected, block 4
50, the termination flag sequence is removed.

In block 480, a determination is made as to whether data transmission has ended or not, and if it has ended, it will be marked with E.

If further data transmission is to be continued, block 49
0, a start flag sequence is detected and the process returns to block 410.

By using the above method, it is possible to hide the start and end flag sequences, and also encrypt other information using a simple method, making it possible to realize a secure communication method that can process faster than conventional methods. .

Next, the conventional communication method (based on HDLC procedure) and
A case will be described in which actual data is transmitted using this embodiment.

In FIG. 6, consider the case of transmitting an information sequence 600. In the case of the conventional HDLC procedure, frame 700 is transmitted, and in the case of this embodiment, frame 80 is transmitted.
0 is transmitted. However, for ease of understanding, addresses 720 and 220, controls 730 and 230 will be explained here.
．． Each sequence of frame checks 750 and 250 is omitted.

A case in which the information sequence 600 is transmitted according to this embodiment will be briefly described below.

First, a start flag sequence 200 '01111110' is sent according to the procedure shown in FIG.

Next, a flag control number is input from the random number generator 30 or 150. Here, it is assumed that '255' is input.

Next, a flag control sequence 210 is transmitted. In the example shown in Figure 6, '255' is expressed as '11111111' and transmitted, but as already mentioned, by using encryption to transmit the data, it becomes even more difficult to intercept and digitize the data. is possible. Various codes can be considered as the codes to be applied, but since they are not the essence of this embodiment, they are omitted here.

Next, the transmission of the information sequence '11000000' takes place. However, as shown in FIG. 5, in this sequence, there is a bit insertion point 'ooooo↑' that corresponds to the flag control number '255', so next, the bit pattern '1' is inserted. is inserted and the information sequence is changed to '110000010'.

In FIG. 5, it is assumed that transmission is performed starting from the left bit.

When the information sequence 240 is transmitted, the flag sequence '0000' corresponding to the flag control number '255' is transmitted.
0010' is transmitted as the end flag sequence 260.

From the above results, in the case of the frame 700 transmitted by the HDLC procedure, as long as a third party monitors the start/end flag sequence '01111110', it is possible to easily intercept or quantify the required information 740. In contrast, according to the method shown in this embodiment, information regarding the relationship shown in FIG. 5, the data transmission/reception procedure shown in FIGS. 3 and 4, and the method for determining the flag control number from the flag control sequence is not available. Otherwise, it would be difficult to intercept the data, and even if the data was placed, it could be easily discovered due to a mismatch between the flag control sequence and the flag sequence.

Further, in this embodiment, information regarding the flag control number is added to the frame and transmitted, but other methods may also be considered, such as the embodiments shown in FIGS. 7 and 8.

In the example shown in FIG. 7, information regarding the flag control number and other information are transmitted using signals of different frequencies. The equipment configuration includes data terminal devices 10, 170, flag control number transmission cables 910, 960, information transmission cables 920° 970, and frequency demultiplexing/synthesizing device 93.
0,950, and a signal transmission cable 940.

In the example shown in FIG. 8, a cable for transmitting information regarding the flag control number and a cable for transmitting information are provided separately. The equipment configuration is data terminal equipment 10, 1
70, a flag control number transmission cable 1000, and an information transmission cable 1100.

In the examples shown in FIGS. 7 and 8, unlike the example shown in FIG. 1, the timing of changing the flag control method is not limited to each frame, and can be changed freely. Further, as the information to be transmitted, it is possible to transmit not only the flag control number but also some or all of the relationships shown in FIG. 4.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to perform encryption and decryption processing at high speed, which was difficult with conventional secret communication methods, and it can be adapted to communication lines that are expected to increase in speed in the future. This has the effect of making it possible.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the configuration of a communication line according to an embodiment of the present invention, Fig. 2 is a diagram showing a frame format according to this embodiment, and Fig. 3 is a diagram showing signal processing on the transmitter side in this embodiment. FIG. 4 is a flowchart showing the signal processing procedure on the receiver side in this embodiment. FIG. 5 is a flowchart showing the signal processing procedure on the receiver side in this embodiment. Figure 6 is a diagram showing the relationship between locations and bit patterns, and Figure 6 is a diagram showing the difference in bit patterns when information is actually sent between the HDLC procedure and this embodiment.
FIGS. 7 and 8 are diagrams showing equipment configurations of other embodiments of the present invention.

Claims (1)

[Claims] 1. Means for temporally changing synchronization codes indicating the start and end of a frame, which is a unit of transmitted information, in a communication line consisting of a data transmitting means, a data receiving means, and a data transmitting means. and a means for not mixing the synchronization code and other information in the frame. 2. The secret communication method according to item 1, characterized in that the information regarding the change of the synchronization code is transmitted by means different from the data transmission means. 3. The secret communication method according to item 1, characterized in that information regarding the change of the synchronization code is transmitted in addition to the frame. 4. Confidentiality according to item 1, characterized in that information regarding the means for temporally changing the synchronization code and information regarding the means for not mixing the synchronization code with information in other frames are concealed. Communication method.