JPS598102B2 - secret communication device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a secret communication device that improves the confidentiality of communication contents.

In the case of communication devices, it is often desired that communication information be exchanged only between parties involved.

However, with commonly used communication devices, it is relatively easy for a third party to intercept communication contents. Therefore,
BACKGROUND ART Various types of secret communication have been considered in the past in which communication information is polarized and transmitted.

That is, there is a conventional secret communication device of this type as shown in FIG. In the figure, 1 is a transmitting device and 2 is a receiving device. Now, in the transmitting device 1, when the original signal shown by the broken line in FIG. 2a is given to the sample and hold circuit 11, the original signal is sampled by the clock signal shown by the clock signal generator 12 in FIG. It is generated as a sampling signal shown in . When this sampling signal is applied to the polarity inverting circuit 13, the sampling signal is changed by the output of the code signal generator 14 which generates the binary code signal shown in FIG. 2c in synchronization with the clock signal. Polarity reversal (in this case code '0'
1", the polarity is reversed.) is performed, and as shown in Figure 2d
A signal shown by the solid line is obtained, which is generated via the low-pass filter 15 as a polarized signal shown by the broken line in FIG. 2d. On the other hand, in the receiving device 2, when the polarization signal from the transmitting side is given to the sample and hold circuit 21, the clock signal of the clock signal generator 22 on the receiving side is synchronized with the clock signal of the clock signal generator 12 on the transmitting side. A sampling signal similar to that shown by the solid line in FIG. 2d is generated.

When this sampling signal is applied to the polarity inverting circuit 23, it is synchronized with the clock signal and moreover, as shown in FIG.
The polarity of the sampling signal is inverted by the output of the code signal generator 24 on the receiving side which generates a code signal corresponding to the code signal shown in FIG. The signal is passed through the bandpass filter 25 and reproduced as an original signal similar to that shown by the broken line in FIG. 2a.
Therefore, if such transmitting/receiving devices 1 and 2 are used, a waveform considerably different from the original signal can be obtained as the polarized signal of the transmitting device 1, so even if a third party intercepts this output signal, it will be difficult to read the communication content. cannot be understood and communication information remains confidential.

However, according to such a conventional device, the sampling signal shown by the solid line in FIG. 2 d, which samples the polarized signal sent from the transmitting device 1, is the same as the sampling signal shown by the solid line in FIG. 2, which samples the original signal, and the sampling signal shown by the solid line in FIG. Since the signals have the same absolute value of the peak value, if we perform full-wave rectification of the sampling signal shown by the solid line in Figure 2 d to obtain the signal shown by the solid line in Figure 2 e, we can obtain the envelope shown by the broken line in Figure 2 e. , we obtain a waveform obtained by full-wave rectification of the original signal. If you listen to this full-wave rectified signal as it is, you will not be able to understand the content of the speech, but you will be able to feel the intonation of the words.
Therefore, even with such signals, it is quite possible to understand the contents of a call through training, and this also raises the possibility that the confidentiality of the communication contents cannot be sufficiently ensured. This invention was made to eliminate the above-mentioned drawbacks, and an object thereof is to provide a secret communication device that can sufficiently ensure the confidentiality of communication contents by changing the polarity and amplitude of the original signal according to the contents of the code. shall be. An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 3, 3 is a transmitting device and 4 is a receiving device. The transmitter 3 connects a sample and hold circuit 32 to an input terminal 31, connects a polarity and amplitude control device such as a variable amplifier 33 to this sample and hold circuit 32, and outputs an output to this variable amplifier 33 via a low-pass filter 34. terminal 35
are connected. A clock signal generator 36 is connected to the sample hold circuit 32. This clock signal generator 36 is designed to generate a clock signal of a predetermined period. Further, a code generator, for example, a code signal generator 37 is connected to the clock signal generator 36, and the variable amplifier 33 is connected to the code signal generator 37. In this case, the code signal generator 37 outputs a code in an appropriate signal format such as a binary code as a code, and in the illustrated example outputs a four-value code signal. Further, the variable amplifying device 33 to which this code signal is given is, for example, as shown in FIG. , the above analog switch? An amplifier corresponding to the above code signal is selected at , and only its output is passed through.
In this case, for example, the first amplifier 331 may include an amplifier that multiplies the input signal by one, such as a buffer, and the second amplifier 332
is an inverting amplifier that multiplies the input signal by -1, and a third amplifier 3.
33 is a positive phase amplifier that doubles the input signal, and the fourth amplifier 334 is an inverting amplifier that doubles the input signal. On the other hand, the receiving device 4 connects a sample and hold circuit 42 to an input terminal 41, connects a polarity and amplitude control device such as a variable amplifier 43 for reproducing the original signal to this sample and hold circuit 42, and connects a variable amplifier 43 to this sample and hold circuit 42. An output terminal 45 is connected via a range filter 44.

Connected to the sample and hold circuit 42 is a clock signal generator 46 on the receiving side that generates a clock signal synchronized with the clock signal of the clock signal generator 36 on the transmitting side. Further, a code generator such as a code signal generator 47 is connected to the clock signal generator 46, and the variable amplification device 43 is connected to the code signal generator 47. In this case, the code signal generator 47 generates the same code signal as the code signal generator 37 described above as a code. Further, the variable amplifier device 43 to which this code signal is applied is similar to the above-mentioned variable amplifier 33, as shown in FIG. It is made by connecting
The analog switch 435 selects the amplifier corresponding to the code signal, and only the output thereof is passed through. In this case, the first amplifier 431 receives an input signal of 1
An amplifier that multiplies the input signal, such as a buffer, a second amplifier 432, an inverting amplifier that multiplies the input signal by -1, and a third amplifier 433.
For the fourth amplifier 434, a positive phase amplifier that multiplies the input signal by ten times is used, and a positive phase amplifier that multiplies the input signal by ten times is used for the fourth amplifier 434, respectively. Next, the operation of the apparatus constructed as above will be described.

Now, in the transmitting device 3, when the original signal shown by the broken line in FIG. The signal is generated as a sampling signal shown by the solid line in FIG. On the other hand, the code signal generator 37 is driven by the above clock signal and generates, for example, a four-value code signal shown in FIG. 5c. Although shown in Arabic numerals in FIG. 5C, they are actually expressed in binary codes. This code signal is then given to the variable amplification device 33.

Here, the analog switch 335 of the variable amplification device 33 is set to the first amplifier 331 when the code signal is "O", the second amplifier 332 when the code signal is "1", and the second amplifier 332 when the code signal is "2". 3 amplifier 333, when the code signal is ``3'', the 4th amplifier 333
If the amplifiers 334 are selected respectively, the sampling signal given by the sampling hold circuit 32 will be sent out as the code signal ゛゜0゜ through the amplifier 331 with the same amplitude, and similarly the code signal ゛゜゜゜ will be sent out with the same amplitude. The code signal ゛21 is sent through the amplifier 333 with the amplitude doubled, and the code signal ゛3゜゜ is sent to the amplifier 33.
4, the signal is transmitted with twice the amplitude and with the polarity reversed. As a result, the sampling signal is converted by the code signal shown in FIG. 5c into the signal shown by the solid line in FIG. is sent to the receiving side. In this case, such polarized signal has completely different polarity and absolute value of peak value from the original signal shown in FIG. 5a.

Therefore, even if this polarized signal is intercepted and full-wave rectified, it will not match the full-wave rectified version of the original signal, and as a result, not only the content of the communication but also the intonation of the speech cannot be interpreted, making it extremely secret. It is possible to provide a secret communication device with excellent security. On the other hand, in the receiving device 4, when the polarization signal sent from the transmitting device is applied to the sample and hold circuit 42 from the input terminal 41, a clock signal on the receiving side synchronized with the clock signal of the clock signal generator 36 on the transmitting side is generated. The signal is sampled by the clock signal of the generator 46 and is generated as a sampling signal similar to that shown by the solid line in FIG. On the other hand, the code signal generator 47 is driven by the clock signal on the receiving side, generates the same code signal as the code signal generator 37, and supplies this to the variable amplification device 43. Here, the code signal "0" is sent to the analog switch 435 of the variable amplification device 43.
When the first amplifier 431. When the code signal is "1", the second amplifier 432, when the code signal is "2", the third amplifier 433, when the code signal is "3", the fourth amplifier 43
4, the sampling signal given by the sampling hold circuit 42 will be sent out with the same amplitude through the amplifier 431 with the code signal "0", and will be sent out with the same amplitude with the code signal "1". 432 with the same amplitude but only the polarity is inverted, the code signal ``2'' is sent through the amplifier 433 with the amplitude multiplied by %, and the code signal ``3'' is sent through the amplifier 434 to increase the amplitude. As a result, the sampling signal is converted into a signal similar to that shown by the solid line in Fig. 5a by the code signal shown in Fig. 5c, and the polarity is inverted.
This signal passes through a low-pass filter 44 and is outputted from an output terminal 45 as an original signal similar to that shown by the broken line in FIG. 5a.

Of course, in this case, only the authorized receiver who knows the code in advance can generate a code signal identical to the code signal of the code signal generator 37 on the transmitting side, thereby maintaining the confidentiality of the communication contents. Become.

Therefore, with such a configuration, a polarized signal having a completely different polarity and amplitude from the original signal is transmitted in accordance with a preset code signal, and this is transmitted to an authorized receiver who knows the code signal in advance. Since the original signal can be regenerated only in the 2-value code signal, the confidentiality of the communication contents can be sufficiently ensured compared to the conventional binary code signal in which only the polarity of the original signal is inverted.

It should be noted that the present invention is not limited to the above-mentioned embodiments, but can be implemented with appropriate modifications within the scope without changing the gist. For example, in the embodiment described in -H, the code signal is ゛0゛~゛3゛1.
Although four types of cases have been described, the number of types can be further increased. Further, the variable width amplification devices 33, 43 of the above-mentioned embodiments
may be anything that changes the polarity and amplitude of the input signal, that is, the sampling signal, and in addition to a positive phase amplifier and an inverting amplifier, a positive phase attenuation and an inverting attenuation can also be used. Furthermore, as shown in FIG. 6, the same effect as described above can be obtained by variably amplifying the original signal in the transmitting device 3 in the variable amplifying device 33 and then sampling it in the sampling hold circuit 32. Further, as shown in FIG. 7, even in the receiving device 4, the same effect as described above can be obtained even if the polarized signal is variably amplified by the variable amplification device 43 and then sampled by the sample hold circuit 42. Here, in FIGS. 6 and 7, the same parts as those in FIG. 3 are given the same reference numerals, and explanations thereof will be omitted. As described above, according to the present invention, it is possible to provide a secret communication device that can sufficiently ensure the confidentiality of communication contents by changing the polarity and amplitude of the original signal according to the contents of the code.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an example of a conventional secret communication device.
FIG. 2 is a waveform diagram for explaining the device, FIG. 3 is a block diagram showing an embodiment of the invention, FIG. 4 is a block diagram showing a variable amplifier circuit used in the embodiment, and FIG. The figure is a waveform diagram for explaining the same embodiment, and FIGS. 6 and 7 are block diagrams showing other embodiments of the invention, respectively. 1, 3... Transmitting device, 2, 4... Receiving device, 11, 32, 42... Sample hold circuit, 12, 36, 46... Clock signal generator, 13... Polarity inversion circuit, 14, 37, 47
・・・・・・Code signal generator, 15, 34, 44...
...Low-pass filter, 31,41...Input terminal, 33,43...Variable amplification device, 331-3
34,431-434...Amplifier, 335,4
35...Analog switch, 35,45...
...Output terminal.

Claims (1)

[Claims] 1. A code generator that generates a preset code signal at a predetermined cycle; a code generator that changes the polarity and amplitude of the original signal according to the code signal of this device and outputs a polarized signal; a control device, a transmitting device having a sample and hold circuit that samples the original signal input to the device or the polarized signal outputted in synchronization with the encrypted signal; A cipher generating device that generates signals synchronously; a polarity and amplitude control device that changes the polarity and amplitude of the polarization signal according to the cipher signal of this device and reproduces the original signal; a polarization signal input or output to this device; a receiver having a sample and hold circuit that samples the original signal transmitted in synchronization with the encrypted signal. 2. A secret communication device characterized in that the code generator comprises a code signal generator that generates a binary code.