JPH0685785A - Ciphering processing method in electric communication - Google Patents

Abstract

PURPOSE:To improve the ciphering performance with simple configuration by applying fast speed Fourier transformation to a digital signal, inserting noise information to several points of a spectrum of a signal through the transformation by means of multiplication and sending the transformed result. CONSTITUTION:An FFT(fast speed Fourier transformation) section 3 applies mathematical processing transforming the time axis into the frequency axis with respect to a digitized voice signal so as to rearrange FET coefficients. A noise component is multiplied with an FFT processing output (waveform b) by a multiplier (MIX) 4. The noise component is a pseudo noise pattern (waveform f) generated by a noise generator 5. The FFT spectrum of noise information is inserted to several points of the FFT spectrum of the voice signal (waveform a) by multiplier processing and so long as the noise information pattern cannot be eliminated at a receiver side, the voice signal cannot be demodulated. Thus, the communication with high ciphering performance is attained with simple configuration.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a confidential communication processing method in telecommunications which is suitable for use in securing confidentiality of telephone calls in the telecommunications field.

[0002]

2. Description of the Related Art Wireless or wired communication, in particular, mobile communication via wireless (police radio, NTT car telephone,
In home wireless telephones, eavesdropping becomes a big problem because broadband receivers are easily available, and confidential communication systems are used in some communication fields (for example, police radio).

There are a digital system and an analog system in the secret system, and the digital system is the best in terms of performance.
It is necessary to allocate an auxiliary signal for encryption processing by digitization, which causes a problem in cost. On the other hand, the analog method includes a spectrum inversion method (used in police radio), a frequency transition method, a spectrum rotation method, a frequency division method, an FFT (Fast Fourier Transform) scramble method, and the like.

For example, in the case of the spectrum inversion method, the secrecy is enhanced by dividing the spectrum into a large number and replacing them. Further, in the case of the FFT scramble method, on the transmission side, first, the audio signal (analog signal) is digitized by A / D conversion, and on the other hand, the FFT processing unit converts the time axis into the frequency axis, and further the FFT coefficient (frequency spectrum). The components are exchanged (scrambled), the inverse FFT processing is further performed, and the result is transmitted to the transmission system. Then, on the receiving side, FFT processing → descrambling → inverse FF
Playback is performed on the path of T → D / A conversion.

[0005]

However, in the above-mentioned conventional technique, there is a problem that the transmission capacity becomes enormous in the case of the FFT scramble method, and in the spectrum inversion method, the speech content is understood by suppressing the voice. There is a problem that it can be done.

[0006] Therefore, an object of the present invention is to provide a confidential communication processing method in telecommunications capable of improving confidentiality with a simple structure.

[0007]

In order to achieve the above object, the present invention converts an analog audio signal into a digital signal, performs a fast Fourier transform on the digital signal, and converts the spectrum of the signal by the conversion. The noise information is inserted into the several points by multiplication and transmitted.

The noise information can be coded and inserted. Further, on the receiving side, the received signal including the spectrally processed voice information is digitized, and the noise information corresponding to the noise information on the transmitting side is removed from the fast Fourier transform result for the digital signal to perform demodulation. There is.

[0009]

According to the above-mentioned means, the FFT spectrum of the noise information is inserted into several points of the FFT spectrum of the voice signal by the multiplication process, and the voice signal is demodulated unless this noise information pattern is removed on the receiving side. It is not possible. Therefore, highly confidential communication is possible with a simple configuration.

Further, by coding and inserting the noise information, it becomes possible to change the noise pattern, making it difficult to decipher the communication by anyone other than the authorized receiver.

On the receiving side, noise information corresponding to the noise information on the transmitting side is generated, and the noise information incorporated in the voice information is subtracted and removed. Therefore, it is possible to take out only the voice signal from which the noise information that has been inserted for confidentiality is removed, and it is possible to easily achieve the construction of a communication system that can achieve a high degree of confidentiality with a simple configuration.

[0012]

1 is a block diagram showing an embodiment of a confidential communication apparatus using the method of the present invention, and FIG. 2 is a waveform diagram of each part showing the operation of the embodiment of FIG. In this embodiment, an example of a wireless communication system with a specific partner is shown.

First, the transmitting side will be described. Human voice, etc.
The audio signal (waveform a) of
1) is converted into an electric signal by the amplifier 1 and further the amplifier 2
Increased to required level by (built-in A / D converter)
After being widened, it is digitalized by the built-in A / D converter.
Be converted. FFT section for digitized audio signals
Mathematical processing to convert the time axis to the frequency axis by 3
Apply to switch the FFT coefficient. This process
This is equivalent to dividing the wave number band into 70 to 90 ways.
This means that there are 0 to 90 different keys. The present invention
Then, for this FFT processing output (waveform b), noise
Minutes are multiplied by a multiplier (MIX) 4. This noise component
Is a pseudo noise pattern created by the noise generator 5.
(Waveform f), and some existing noise patterns
(For example, 16 types consisting of 4 chord combinations)
You can choose from. The amplifier 6
After amplification to bell, by the same method as in the case of FFT section 3
FFT processing is performed in the FFT unit 7 (waveform c). Multiplier
The result of multiplication by 4 is waveform d.
Inappropriate for processing such as high frequency amplification and frequency conversion in the communication circuit
Therefore, the IFFT (inverse FFT) unit 8 performs the inverse FFT processing.
To obtain the waveform e. On the other hand, in the transmitter 9, the frequency
Number modulation, frequency mixing, frequency multiplication, high frequency power amplification, etc.
And, for example, VHF band (for example, 800 to 900M
H z high frequency power in the mobile communication band) to obtain the antenna (A
NT) 10.

On the other hand, on the receiving side, the antenna 11 receives the high-frequency signal from the antenna 10, and the receiver 12 (high-frequency amplification, frequency mixing, frequency demodulation, and A / D converter built-in) can perform amplification and FFT processing. After being converted into a digital signal, the FFT unit 13 performs FFT processing and demodulates the inverse FFT signal as a waveform d. Further, the noise generator 15 generates a pseudo noise pattern, which is amplified by the amplifier 16 and then applied to the FFT unit 17. At this time, the noise information is decoded by the code detection circuit 18 with respect to the demodulation result by the FFT unit 13, and a pseudo noise pattern matching the decoded code (there are four types as described above) is given from the noise generator 15. FFT only at times
The FFT processing by the unit 17 is executed, and this is applied to the multiplier 14. The multiplier 14 outputs the FF from the output of the FFT unit 13.
The output of the T section 17 is divided to obtain the waveform b. When the IFFT unit 19 performs an inverse FFT process on this signal, a waveform a, that is, a voice signal is demodulated. The audio signal is amplified by the amplifier 20, and the speaker 21 (or earphone) is driven.

As described above, in the past, the secret talk was made only by the operation of changing the spectrum of the voice, but according to the present embodiment, the secret talk system which cannot be easily decoded by adding noise is constructed. can do. In addition, narrowing of the band is facilitated and the influence of level fluctuation can be reduced.

In the above description, only wireless is shown, but the present invention can be applied to wired.

[0017]

Since the present invention is configured as described above, it has the following effects.

In the confidential communication processing method in telecommunications of claim 1, an analog voice signal is converted into a digital signal, a fast Fourier transform is applied to this digital signal, and noise information is obtained at several points of the spectrum of the signal by this conversion. Is transmitted by multiplying by, thus enabling highly confidential communication with a simple configuration. In the confidential communication processing method in telecommunications of claim 2, noise information is coded and inserted. Therefore, the noise pattern can be changed, and it is possible to make it difficult for a person other than the authorized receiver to decipher the communication.

According to the third aspect of the present invention, in the confidential communication processing method in telecommunication, the received signal containing the spectrally processed voice information is digitized, and the noise information corresponding to the noise information on the transmission side is obtained from the fast Fourier transform result of the digital signal. Since the demodulation is performed by removing it, it is possible to construct a high degree of confidentiality on the receiving side with a simple configuration.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a confidential communication device using the method of the present invention.

FIG. 2 is a waveform chart of each part showing the operation of the embodiment of FIG.

[Explanation of symbols]

 1 Microphone 2 Amplifier 3 FFT section 4 Multiplying section 5 Noise generator 6 Amplifier 7 FFT section 8 IFFT section 9 Transmitting section 10 Antenna 11 Antenna 12 Receiving section 13 FFT section 14 Multiplier 15 Noise generator 16 Amplifier 17 FFT section 18 Code detection Circuit 19 IFFT section 20 Amplifier 21 Speaker

Claims (3)

[Claims] 1. An analog voice signal is converted into a digital signal, a fast Fourier transform is applied to this digital signal, and noise information is inserted into several points of the spectrum of the signal by this conversion by multiplication to be transmitted. Confidential talk processing method in telecommunications. 2. The confidential communication processing method in telecommunications according to claim 1, wherein the noise information is coded and inserted. 3. A demodulation is performed by digitizing a reception signal containing spectrum-processed voice information, removing noise information corresponding to the noise information on the transmission side from a fast Fourier transform result of the digital signal, and demodulating the received signal. Confidential talk processing method in telecommunications.