JPS62264739A - Privacy call device - Google Patents

Abstract

PURPOSE:To realize the sophisticated privacy call system with simple constitution by sending 4-kind of pattern states in time division according to a privacy call key in the preset order and decoding the state at the reception side according to the order of the sake privacy call key as that of the sending side. CONSTITUTION:A voice signal from a microphone and the 1st carrier are added to the 1st BM1, and both side bands of its output are given to a BPF, an SSB wave is extracted, it and the 2nd carrier are fed to the 2nd BM and a privacy call pattern whose voice spectrum is modified is obtained at its output. The received privacy call signal is given to a balanced m demodulator (BD), from which both side bands are obtained, the result is iven to the BPF to form an SSB signal, which is demodulated by the 2nd BD to reproduce the voice signal. The 2nd carrier frequency is controlled by using a CPU from the 4-kind of privacy signal patterns.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a confidential communication device for preventing eavesdropping by a third party in a communication format in which voice is converted into an electrical signal, whether it is a telephone or wireless communication. It is something.

[Conventional technology and problems]

When making a call using electrical audio signals, basically the transmitting side uses a phycrophone to convert the strength of the sound waves into the magnitude of electricity, and sends it out by passing it through an electric wire or modulating the radio waves, and on the receiving side, the modulated waves are demodulated. The system converts the signal back into an audio signal, converts it into sonic vibration through a speaker, and receives the call. Therefore, in wired communication, it is possible to easily listen to the contents of a call by connecting a receiving device to the telephone line, and in wireless communication, by demodulating the received radio waves in the same modulation format as that of the transmitter. This is desirable for general telecommunications, excluding broadcast radio and amateur radio. Therefore, a confidential communication system is adopted for important communication lines to prevent eavesdropping by third parties, and recently many digital signaling systems have been developed, but here we will discuss only the analog signaling system that has the advantage of this invention. state

The basis of the confidential communication method for analog signals is to make it impossible for listeners to understand by changing the sound wave spectrum.
Methods for this include frequency shifting, frequency inversion, and division and replacement of frequency bands in the audio spectrum pattern, but since it is relatively easy to restore the content to an understandable level using only these methods, time-division There is a way to send it. In this case, even if it is possible to reconstruct a number of patterns, if the order of the sending patterns is not known, it will be impossible to reconstruct the whole, so the confidentiality is extremely high.

For this reason, the order of patterns that are set to be the same between the transmitter and the receiver is called a secret key, and in order to keep the operation timing of the secret key on the receiver side the same as that on the transmitter side, all synchronization signals are generated at the start of transmission. Usually, the first pattern of the secret key is activated at the same time as the synchronization signal ends.

In wireless communication or carrier communication, there are secrets due to special modulation formats. For example, since SSB waves cannot be understood by ordinary AM receivers, they were initially considered a type of secret communication method, but since they can be demodulated by injecting a BFO carrier into the detection, wobbling, which periodically fluctuates the carrier frequency, can be used for demodulation. The confidential telephone system was used for a long time in international telephone communications. However, this level of secret speech can be demodulated relatively easily at present, and a random number secret speech key method is required. However, the technology for generating and demodulating SSB waves is an important factor in the configuration of the secret speech device of the present invention. There is SSB below
This section describes wave generation and demodulation methods.

For details on SSB, see Single 5ide Band
It is an abbreviation for 5uppressed Carrier, and is obtained by removing the carrier from a normal amplitude modulated wave and extracting only one of the upper and lower sideband waves. The generation method is 3
Although there are various methods, the most practical one is the filter method shown in FIG.

In the figure, when an audio signal and a carrier are applied to a balanced modulator (hereinafter abbreviated as BM), the output is the carrier t-
This is an amplitude modulated wave that has been suppressed by about 20 dB, and only one of the upper and lower sidebands is extracted through a bandpass filter (hereinafter abbreviated as BPF), and the carrier is also suppressed by about 20 dB. The sideband waves (SSB) created in this way have exactly the same spectral array as the original audio, but the frequency is related to the carrier frequency, so it cannot be demodulated as audio by simply performing envelope detection. First, the original audio is restored by adding a carrier and performing product detection. If the carrier frequency added at this time is closer to the sideband than the original frequency, the demodulated sound will have a low pitch and a low pitch, and conversely, if it is far away, the demodulated sound will have a high pitch and a low pitch, and if the difference exceeds 100 Hz, it will be difficult to understand. This is what you experience when receiving waves.

Furthermore, if the carrier frequency during demodulation is shifted to the opposite side of the sideband, the detected output will have a shape in which the audio spectrum is inverted.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a confidential communication device with a relatively simple configuration that can realize a highly confidential communication system in voice telecommunication calls.

[Summary of the invention]

This invention relies on voice telecommunications. In a call, the first
As shown in the figure, the normal frequency spectrum/arm ■ and the spectrum pattern with shifted frequency ■
Then, the frequency spectrum is inverted and the four-heel turn ■ and the frequency is inverted and shifted is the spectrum pattern ■, which are transmitted in a time-division manner according to a secret key in a preset permutation. This is a secret communication device characterized in that the frequency spectrum pattern of a received signal is restored to a completely normal frequency spectrum pattern according to the same permutation of secret keys as that of the speaking side.

Claim 2 provides a configuration in which, in order to synchronize the secret key on the transmitting side and the receiving side, a reset signal for the secret key operation is sent at least at the start of transmission in addition to the first four turns of the secret key. stipulates. In other words, in FIG. 2, column I1 represents the transmit/receive signal, and when the transmit switch is turned on from the receiving state "!" or the rest state, a reset signal for the private key operation is first sent and the own device ( This is to synchronize the confidential key operations on the transmitting and receiving sides by starting the confidential key circuits on the transmitting side and the receiving side at the same time.This reset signal may be a single-shot noggle, but In the communication system, there is a possibility of malfunction due to line noise, so it is appropriate to use a reset signal using a burst signal or a group of pulses, and to make the duration equal to 1/J? turn of the secret key.

The (n) column and the first book column in Figure 2 show the timing of the arrangement of the untold stories and arm turns, and the arm turns in ■ to ■ are the first rows, respectively.
This is the same as the 74 turns from ■ to ■ in the figure. For convenience, the diagram shows ■
They are arranged in the order of ■■■, but the secret key is established by using random numbers to arrange the patterns within one cycle of the secret key, so if the capacity of the secret key is allowed, the patterns within the secret key cycle It is possible to improve the sophistication of secret keys through overlapping combinations.

The second whistle (in the IF5 row, the first pattern ■ of the secret key starts from the end of the reset signal, but
As stated in claim 5, when "when transmitting continues for a long time, a synchronization signal is sent to the transmitted secret voice at scheduled time intervals", the synchronization signal is synchronized with the reset signal at each scheduled time interval. However, in reality, the synchronization is out of order, so forcing the synchronization to be corrected tends to create an unnatural feeling. However, the next private key cycle will start delayed by the synchronization period, and if the reset signal is lost on the receiving side, the synchronization will be lost. On the contrary! In the @) row, the first pattern ■ of the secret key starts operating when the reset signal is generated, and switches to the second pattern ■ when the reset signal ends, and the intermediate reset signal also starts operating as the first pattern ■ of the secret key. If someone did that during the period of J. Kuhn■, the reset signal would only correct the synchronization of the secret key, but the order of operations would remain the same, so even if the intermediate reset signal were to fail, it would cause a major problem in receiving calls. 2. When moving from transmitting to receiving, the other party receives a reset signal generated at the beginning of transmitting and synchronizes the private key.

Claim 3 is the configuration of a secret speech/9-turn generation circuit on the transmitting side, and to explain the example circuit shown in FIG.
and the first carrier 31 from the first local oscillator 3, and extract the SSB wave 41 through the double-side band wave 11t''BPF4tl- of the output, and send this to the second BM5.
and the second carrier 61 from the local oscillator 6 of
The output 51 is configured to transform the audio spectrum to obtain nine secret speech patterns. In this circuit, in order to create the four types of secret patterns described in Section 1, (Al) As illustrated in the upper part of FIG. distributed as symmetrical sidebands,
Through BPF 4 'ii-, only one side (the upper sideband in the figure) is fully extracted, and the SSB signal 41i shown in the middle of FIG. By doing so, a normal voice spectrum pattern as shown in the lower part of Figure 4 (■) is obtained. Although this seems like a wasteful operation, the practical effects will be explained later.

(Bl fcSSB signal 4 obtained in the same manner as in (A) above)
By setting the frequency of the second carrier 61, which is added to the second BM5 along with 1, to the carrier 61b, which is shifted by 11 from the first carrier 31, an audio spectrum pattern in which the frequency is completely shifted as shown in the lower part of υ Figure 4 is obtained. .

(C1 Obtained in the same way as in (A) above 7'jSSB signal 41
At the same time, by setting the frequency of the second carrier 61 added to the second BM5 to the second carrier frequency 61c set at the opposite position of the sideband 41, a pattern in which the audio spectrum is inverted as shown in the bottom part of FIG. 4 is obtained. .

(D) SSB signal 41 obtained in the same manner as in (A) above
At the same time, the frequency of the second carrier 61 added to the 20th BM5 is changed to a second carrier frequency 61d shifted by f2 from the opposite position of the sideband 41, thereby producing an audio space as shown in the lower row of FIG.

You get a pattern of inverted and shifted trams.

Claim 4 is a configuration of a recovery and reproducing circuit based on a confidential message/book turn on the receiver side, and in accordance with the principle of confidential message recovery and reproduction in which the procedure for creating a confidential message pattern is reversed, in the circuit illustrated in FIG. The secret signal 51 is passed through the first balanced demodulator (hereinafter abbreviated as BD) 25 to obtain both sideband waves 251, passed through the BPF 24ffi to become an SSB signal 241, and demodulated by the second BD 21 to generate audio. The general rule is that the signal 20'', (reconstructed), BPF 24 has the same characteristics as BPF 4 in FIG. 3, and carrier oscillators 26 and 23 are respectively equal to 6 and 3 in FIG. When the frequencies of 26 and 23 are swapped, it becomes necessary to widen the bandwidth of the BPF 24 by the shift frequency at the turns 2 and 2 in FIG.

Among the carrier oscillators 3, 6, 23, and 26, the fixed frequency is a crystal oscillator, and the variable frequency is a PLL (Phase Locked Loop) for frequency setting and stability.
) Usually, it is configured with a controlled oscillator, and since the frequency of the PLL controlled oscillator can be set by numerical input, it is controlled by the output of the confidential key 7/27, and the confidential key 7 on the transmitting side and the confidential key 27 on the receiving side are controlled. The synchronization of the operations is performed by sending out a reset signal for the secret key operation at least at the start of transmission, as described in the second and fifth sections.

As mentioned in Section 3 (A), among the four types of confidential conversation patterns, ■ is the input audio signal 20 (51
) and the output audio signal 51 (20) have exactly the same shape, so there is no need to pass the signal through the power secret circuit in this way, but the creation and restoration of the 4 m secret speech/2 turns is done by controlling the carrier frequency using the secret key. Since it can be done simply by doing the following, there is no disadvantage in terms of structure or operation.

[Embodiments of the invention]

FIG. 6 shows an embodiment of the present invention. In the transmitter-side secret signal circuit, the configuration of the first BM-BPF and the second BM is the same as in Figure 3, and the four-way secret signal pattern of ■■■■ in Figure 1 uses the frequency of the second carrier oscillator as the secret key. Instead of directly setting the
ing Unit)f: to fully control the second carrier frequency, the secret key is also taken into the CPU, and the rise of the transmission power supply voltage is used as the transmission start signal,
As a reset signal for the secret key, a specific frequency v within the audio frequency band is sent to the secret signal output circuit for the first turn period of the secret key cycle (in this case, each pattern is set to 100m5), and the reset signal is terminated. At times, the CPU provides setting data for the second ninth turn of the secret key cycle to the second carrier oscillator, and thereafter sends out the secret number turns in accordance with the secret key at a pitch of 100 ms.

The secret communication circuit on the receiver side is the 1st BD-BPF and the 2nd BD.
The configuration is the same as that in Fig. 5, and the input signal is taken into the reset signal '1cPU through the reset signal detection circuit.
Synchronizing with the end of the reset signal, the CPU starts the second I turn of the secret key, gives the second pattern setting data to the first carrier oscillator, and thereafter the secret key is set to 100.
They operate in synchronization with m5 pitches. The reset signal detection circuit may be a mechanically resonant micro fork or frequency decoder IC that sensitively detects only specific frequencies.
etc. have been put into practice.

[Other Examples]

In the configuration of the present invention, the BM and BD can be constructed from the same member, and it is desirable that the BPF have the same characteristics. Therefore, FIG. 7 shows an embodiment in which these are used in common for transmitting and receiving calls.

When transmitting a message, the confidential communication circuit 2 turns the input switch S and the output switch S2 to the T side, and the first BM/BD operates as a BM, the first carrier is all fixed frequency, and the second BM/BD
D also operates as a BM, and the second carrier sets the second carrier frequency based on the output data of the CPU that has taken in the secret key data.

When receiving a call, flip switches S1 and 82'i to the R side, and press
The second BM/BD operates as a BD, and the first carrier is configured to set the first carrier frequency based on the output data of the CPU that has taken in the secret key data.

To synchronize the private key operations on the transmitting side and the receiving side, at the start of transmission, the CPU sends a reset signal of a specific frequency within the audio band to the confidential signal output line at the rising edge of the transmitting/receiving signal, and In this case, the received reset signal is taken into the t-CPU from the secret signal input line through the reset detection circuit, and the timing of the secret key operation is made to match that of the transmitting side.

FIG. 8 shows a general flowchart of the CPU.

First, start by turning on the power or resetting it.

First, the secret key data is taken in, then it is checked whether it is transmitting or receiving, and the receiving side performs a synchronization acquisition operation, and the clock signal sent from the transmitting side or the cent signal is used as a synchronizing signal to start. Next, the operation of switching to the next equal turn υ is continued through the one-step cycle timer of the secret key pattern (set to 100m5 in this case).

In the transmission state, first, a reset signal is sent synchronously, and after a 100m5 timer, the secret key pattern continues to be switched.

〔Effect of the invention〕

In confidential communication, the most important purpose is to maintain the confidentiality of the contents of the call, but in mobile communication devices and subscriber telephones with a large number of stations, due to cost and space considerations, it is necessary to simplify the device and use the main unit as an additional device. It is desirable to be able to attach it externally.

In the present invention, since the configuration uses a telepathic secret key that combines four types of secret stories/book turns with random numbers, the secret story property is extremely high compared to the single secret story method, and the secret story/four turns are directly attached to the secret story key itself. It does not contain any instructions for secrecy, and only works in combination with a specific secret device, and diversity can be increased by selecting the carrier frequency of the secret device, so the secrecy of the secret key itself is a problem. It is highly safe because it does not cause any damage.

As a confidential communication device circuit, it is possible to create four types of confidential communication patterns by simply changing the carrier frequency using the same circuit, and in practical use, the transmitting device and the receiving device are the same as the circuit shown in FIG. 7 of other embodiments. Since it can be configured with the following circuits, the required components of the entire device can be reduced by almost half and the device can be made compact, making it convenient for externally attaching it to a conventional communication device as an adapter.

As a dual-purpose circuit for transmitting and receiving, a bidirectional circuit using diodes for BM/BD can be used, and by passing the received confidential signal in the opposite direction to the confidential signal circuit on the transmitting side as shown in Figure 6, it is possible to transmit using the same circuit. /It is also possible to configure a confidential communication device.

As described above, the confidential communication device of the present invention has the effect of maintaining a high degree of confidentiality with a relatively simple configuration of the confidential communication circuit.

[Brief explanation of drawings]

Figure 1 is a configuration diagram of the audio spectrum of four types of secret speech patterns, Figure 2 is a diagram of the composition of the secret key pattern cycle, Figure 3 is a diagram of the configuration of the secret speech device on the transmitting side, and Figure 4 is the secret speech 74' in Figure 3. 5 is a configuration diagram of the confidential communication device on the receiver side, FIG. 6 is a configuration diagram of an embodiment of the confidential communication device of the present invention, and FIG. 7 is a configuration diagram of another embodiment of the present invention, FIG. 8 is a general flowchart of the CPU in FIG. 1.5...BM, 2...Microphone, 3.6.2
3.26...Carrier oscillator, 4.24...BPF
. 21/25...BD, 7/27...secret key. Patent Applicant Yaesu Musen Co., Ltd. No. 1 Fig. 3--111111111- i-Haru FL+ Fig. 8

Claims (5)

[Claims] (1) In telephone calls using electrical audio signals, there are four types of pattern states: a normal frequency spectrum pattern, a spectrum pattern with the frequency shifted, a pattern with the frequency spectrum reversed, and a spectrum pattern with the frequency reversed and shifted. A secret communication device characterized by transmitting data in a time-division manner according to a preset permutation of secret keys, and restoring the frequency spectrum pattern of a received signal to a normal frequency spectrum pattern on the receiving side according to the same permutation of the secret keys as on the transmitting side. . (2) In order to synchronize the confidential keys on the transmitting side and the receiving side, a reset signal for the confidential key operation is sent at least at the start of transmission in addition to the first pattern of the confidential key. The secret communication device described in paragraph 1. (3) The configuration of the secret message pattern generation circuit on the sending side is as follows:
The audio signal and the first carrier frequency are applied to a balanced modulator, the output of the first balanced modulator is passed through a bandpass filter, only one sideband is taken out, and the second carrier frequency is applied to the second balanced modulator. (A) To create a normal audio spectrum pattern, sidebands distributed above and below the first carrier frequency are added to the output of the first balanced modulator to obtain the desired spectrum pattern. Pass through a bandpass filter to remove unnecessary sidebands and carriers, extract only one sideband, and add this to a second balanced modulator with a second carrier having the same frequency as the first carrier frequency.
By passing it through an audio band low-pass filter, it is configured to obtain an audio output signal with the same normal spectrum pattern as that input to the first balanced modulator. To create the output, the sidebands distributed above and below the first carrier frequency in the output of the first balanced modulator are passed through a bandpass filter to remove unnecessary sidebands and carriers, and only one sideband is extracted. A second carrier frequency that is different from the first carrier frequency by the shift frequency is added to the second balanced modulator, and is passed through an audio band low-pass filter to generate an audio output signal with a frequency-shifted spectrum pattern. (C) To create a frequency-inverted audio spectrum pattern, the sidebands distributed above and below the first carrier at the output of the first balanced modulator are filtered through a bandpass filter to eliminate unnecessary sidebands. The carrier is removed to extract only one sideband, and a second carrier frequency, in which the first carrier frequency is set at the opposite position of the sideband, is added to the second balanced modulator to generate a low frequency band for the audio band. It is configured to obtain an audio output signal with a spectrum pattern that is an inversion of the audio spectrum input to the first balanced modulator by passing it through a band pass filter. At the output of the first balanced modulator, the sidebands distributed above and below the first carrier are passed through a bandpass filter to remove unnecessary sidebands and carriers, extracting only one sideband, and using this as the second balanced modulator. A second carrier frequency that differs by a shift frequency from the opposite position of the first carrier frequency and the sideband is added to the modulator, and the second carrier frequency is passed through a low-pass filter for the audio band, thereby adding a second carrier frequency to the first balanced modulator. The secret speech device according to claim 1, which is configured to obtain an audio output signal having a spectrum pattern obtained by inverting an input audio spectrum and shifting its frequency. (4) The configuration of the restoration/reproduction circuit based on the secret pattern on the receiver side is such that the secret speech signal received by the first balanced demodulator and the first
The output of the first balanced demodulator is passed through a bandpass filter to take out only one sideband, and is applied to the second balanced demodulator together with the second carrier frequency to reproduce normal speech. In restoring and reproducing the four types of audio secret speech patterns as set forth in claim 3, the frequency band of the bandpass filter is changed to the bandpass filter of the transmitting side secret speech device as set forth in claim 3. the injected carrier frequency of the first balanced demodulator is equal to the second carrier frequency of the transmitting-side privacy device of the third term, and the injected carrier frequency of the second balanced demodulator is equal to the second carrier frequency of the transmitting side of the third term. The secret speech device according to claim 1, which is equal to the first carrier frequency of the secret speech device and is configured to switch in synchronization with each of the four types of secret speech audio patterns. (5) For synchronization of carrier frequency switching for restoring and reproducing four types of confidential patterns between the transmitting confidential circuit according to claim 3 and the receiving confidential circuit according to claim 4, At the start of the transmitting operation, a synchronizing signal is sent in place of the first transmitting voice pattern, and when the synchronizing signal is stopped, a specific clause of a combination of secret voice patterns that has been set in advance on both the transmitting and receiving sides is transmitted. Claim 1, which performs more independent synchronization, and is configured such that a synchronization signal can be input to the transmitted confidential voice at scheduled time intervals when transmitting continues for a long time. The secret device described.