JPH073968B2 - Confidential communication device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a confidential communication device for maintaining communication confidentiality in wired communication or wireless communication.

(Prior Art) FIG. 2 shows a first method of a conventional confidential communication device (Japanese Patent Laid-Open No. Sho 60).
-89143) is a block diagram showing an example of the configuration, (A) shows a transmitting side, and (B) shows a receiving side. First, on the transmitting side in FIG. 2 (A), 1a is an audio input terminal and 2a is an LPF. Reference numeral 3a is a delay circuit (memory circuit) having N delay stages, which samples and stores the sound in accordance with the clock of the clock circuit (CP1) 4a, and at the same time sequentially outputs the sampling values sampled and stored before N sampling points. Is a variable delay circuit that constantly stores N sampling values. The output of the delay circuit, after passing through the LPF 5a, is added to the output of the synchronizing signal circuit 6a by the adding circuit 7a, and then sent to the wired or wireless transmission system 9a via the transmitting circuit 8a which performs modulation and amplification for transmission. It

On the receiving side of FIG. 2 (B), the received signal that has passed through the transmission system 9 is demodulated by a receiving circuit 10a including an amplifying and demodulating circuit, and then, a clock of a clock circuit (CP2) 12a is passed through an LPF 11a. According to the above, the received voice is sampled and stored, and at the same time, the sampling values sampled and stored before the N sampling time points are sequentially stored in the N sample storage circuit 14a for outputting via the LPF 13a. The synchronization between the transmission side and the reception side is performed by a synchronization separation circuit 15a that separates the synchronization signal sent from the synchronization signal generation circuit 6a on the transmission side from the reception signal, thereby completely synchronizing the clock on the reception side with that on the transmission side. Be done. FIG. 3 is a diagram showing a basic circuit configuration of the confidential communication device shown in FIG. 2, and the basic configuration is the same for both the transmitting side and the receiving side. That is, it comprises a delay circuit 3a such as a BBD for inputting and outputting an audio signal and a clock frequency control circuit 4a for controlling the frequency of its clock pulse 21a, and the clock frequency control circuit further comprises a master clock frequency oscillation circuit 17 and its Dividing circuit for dividing the output 18
A counter circuit 19a for counting clock pulses to the delay circuit 3a such as BBD, and a logic circuit 20a for controlling the frequency division number of the frequency divider circuit by the output signal of the counter.

The basic operation of the circuit in FIG. 3 is to change the clock frequency to BBD3a by changing the frequency division number,
By making the frequency of the clock pulse 21a at the time of input to the BD different from the clock frequency at the time of output after the delay, the frequency of the output audio signal is changed from that of the original, and the audio is scrambled. It is a thing.

On the other hand, on the receiving side (B), in the circuit having the same configuration as the transmitting side (A), by changing the clock frequency to the BBD14a on the receiving side in synchronization with the change in the clock frequency to the BBD3a on the transmitting side, The frequency of the input scrambled sound is configured so that the frequency of the scrambled audio is converted back to the original value and the restoration operation is performed.
If f ₁ and the output time are f ₂ , the audio frequency is converted to f ₂ / f ₁ times. The frequency change was cyclic between about 1/2 and 2 times.

Further, FIG. 4 shows a second method of the conventional confidential communication device (published by Ohmsha, Electronics, October 1984 issue, 56-62).
In the block diagram showing the configuration example of (Page), the encryption processing method is a frequency scrambler, and FFT is used instead of filter bank.
The band is subdivided using (Fast Fourier Transform). The audio signal is converted to a digital signal using the A / D converter, and 256 sample data divided at intervals of 32 ms is DSP.
To enter. The DSP first performs FFT processing on the audio signal and converts the time axis waveform into a frequency spectrum sequence. Here, a part of the spectrum is deleted, a dummy spectrum of 16 waves is inserted instead, and the entire band is transposed. After this the spectrum is reversed
After FFT, the original time-axis waveform is restored and encrypted output is obtained.

The signal processing of the decryption is performed in the same flow as the encryption, but the spectrum inserted by the encryption is deleted at the decryption stage. Here, the effect of inserting the dummy spectrum is to make the envelope curve indicating the presence or absence of voice remaining in the encrypted output constant, and at the same time, create an interfering wave in the encrypted spectrum to improve confidentiality. Furthermore, by changing the frequency transposition method for each FFT frame, the confidentiality can be further improved. To change the transposition for each frame, the transposition combination was written in the memory in advance, and the memory address was randomly indexed by the random number data generated by the DES-LSI.

(Problems to be Solved by the Invention) In summary, the first conventional method is to control the frequency of the system clock signal in accordance with the key signal. But,
Generally, it is not preferable to change the clock frequency in order to maintain stable operation of the system and avoid complication of the system. on the other hand,
In summary, the second conventional method is to divide a band of a transmission signal (for example, voice) into a finite number and make the arrangement correspond to a key signal. In this method, the number of divisions is quite limited, and since the features of the speech waveform cannot be sufficiently erased and remain, a dummy spectrum is inserted. However, there is a problem in that it is necessary to completely remove the dummy signal so that the dummy spectrum does not distort the transmission signal itself, and the transmission quality is inevitably deteriorated.

Therefore, an object of the present invention is to provide a confidential communication device in which the clock frequency is maintained constant and the dummy spectrum need not be inserted.

(Means for Solving Problems) The present invention relates to a secret communication device, for example, 64
A secret password storage means for storing a secret password having a bit length and a secret password for generating block password data (for example, 64-bit length) of a data pattern consisting of 1 and 0 different from the previous one at a constant cycle with the secret password as an initial value. Password generating means, generating a random signal having a random phase value varying between −π and + π corresponding to the block password, and generating a cosine wave having a cosine value corresponding to the random phase value and the random phase value. Random signal generating means for generating a sine wave having a sine value corresponding to, an orthogonalizing means for generating a quadrature wave component which is orthogonal to the input signal as an in-phase wave component, and the sine wave and the in-phase wave component are multiplied. A means for generating an in-phase output, and a means for multiplying a cosine wave and a quadrature wave component to generate a quadrature output, Taking the difference between the quadrature output and the phase output and has a synthesizing means for sending this as privacy output.

Further, the random signal generating means described above corresponds to 1 and 0 of the block password, and in the case of data (value) of 1, θ (nΔt) = θ ((n−1) Δt) + πf _R / 2f _S. ,
In the case of data (value) that is 0,
Δt) = θ ((n−1) Δt) −πf _R / 2f _S , and a random signal having a random phase value varying between −π and + π is generated.

Although the above is the configuration of the transmitting side, the receiving side can be demodulated by providing the same configuration as the transmitting side and performing an operation opposite to that of the transmitting side, as in a normal confidential communication system. You can

(Operation) As described above, the present invention does not change the clock frequency and does not insert a special dummy spectrum,
Since the input signal itself such as voice is controlled by the phase modulation using the product, the degree to which the transmission quality is impaired is slight.

Also, instead of switching the phase of the input signal according to the secret password or the block password data 1 and 0 generated by an appropriate algorithm using the secret password as an initial value, it is created by using the block password 1 and 0 patterns. Since the random phase value is changed, the phase can be changed for each sample of the input signal, and high confidentiality can be obtained.

(Embodiment) FIG. 1 is a block diagram showing an embodiment of the present invention.
1 is a secret password storage unit, 2 is a secret password conversion unit,
3 is a random signal generator, 4 to 6 constitute a modulator, 4 is an orthogonalization unit, 5 and 6 are multiplication units, respectively.
7 is a synthesizing unit, 8 is a demodulation password storage unit, 9 is a demodulation password conversion unit, 10 is a random signal generation unit, 11 to 13 are demodulation units, 11 is an orthogonalization unit, and 12 and 13 are The multiplication unit and the synthesis unit 14 are respectively.

The secret password and the demodulation password are the same, and are 64-bit passwords with the same 1.0 pattern.
Each is configured based on a password algorithm that generates block password data with a secret password and a demodulation password as initial values, and assuming that the generation frequency of each data bit is f _R [Hz], every 64 / f _R [sec], Generate block password data that does not have the periodicity different from the previous one. The random signal generation unit 3 (or 10) has the same frequency as the sampling frequency f _S of the voice signal according to the value R of 1.0 pattern of the block password data of the secret password generation unit 2 (or demodulation password generation unit 9). , Cosine wave θe corresponding to the random phase value θ is generated. Now, at the time t = nΔt (Δt = 1 / f _S ), the random phase value θ (nΔ
t) is when R = 1 When R = 0, Becomes Therefore, the output of the random signal generator 3 is θe
(NΔt) = cos (θ (nΔt)). At the same time, the random signal generator 3 changes the cosine signal θe (nΔt) to θe.
Sine wave signal θo (nΔt) = sin orthogonal to (nΔt)
(Θ (nΔt)).

In the following general expression, θe (nΔt) is referred to as an in-phase wave component, θo (nΔt) is referred to as a quadrature component, and the random phase value θ will be described later with reference to FIG. The orthogonalization units 4 and 11 are each composed of a Hilbert transform type transversal filter for converting into orthogonal signals, and the orthogonalization unit 4 generates the orthogonal wave component So of the voice input signal S, and the orthogonalization unit 11 Is the orthogonal wave component Po of the confidential output signal P.
To occur. The multiplication unit 5 determines the in-phase wave component of the voice input signal S.
Se (= S) and the in-phase output θe of the random signal generator 3 are multiplied and in-phase to obtain the output Te. The multiplication unit 6 multiplies the orthogonal wave component So of the voice input signal output from the orthogonalization unit 4 and the orthogonal component main force θo of the random signal generation unit 3 to obtain an orthogonal output To.

The synthesizing unit 7 synthesizes the in-phase output Te and the quadrature output To to generate the confidential output signal P. The multiplication unit 12 multiplies the in-phase wave component Pe (= P) of the confidential output signal P and the in-phase wave component θe of the random signal generation unit 1 to obtain the in-phase output De. The multiplication unit 13 is an orthogonalization unit
An orthogonal output Do is obtained by multiplying the orthogonal wave component Po of the confidential output signal P which is the output of 11 and the orthogonal wave component θo of the random signal generator 10. The synthesizer 14 synthesizes the in-phase output De and the quadrature output Do to generate a demodulated voice output SS. Now, as an input signal of the confidential communication device of FIG. 1, a tone signal S = cosωt of angular frequency ω
, Se = cosωt, So = sinωt, Te = cosωtcosθ
(T), To = sin ωtsin θ (t), and therefore, the output (secret signal) P on the transmission side is P = Te−To = cos (ωt + θ
(T)). On the receiving side, Pe = cos (ωt + θ
(T)), Po = sin (ωt + θ (t)), De = cos (ωt +
θ (t) cosθ (t), Do = sin (ωt + θ (t)) sinθ
(T) Therefore, the reciprocal output SS on the receiving side is SS = De + Do = co
s (ωt + θ (t)) cosθ (t) + sin (ωt + θ
(T)) sin θ (t) = cosωt, and it can be seen that the same signal as the confidential communication device input signal S = cosωt was obtained and completely demodulated.

FIG. 5 is an explanatory diagram of the random phase of this embodiment.
FIG. 5A shows the time variation of the output of the secret password password conversion unit 2 of FIG. 1, which is equal to the output time variation of the demodulation password conversion unit 9 of FIG. It is the value of the bit pattern R. FIG. 5B shows the time variation of the random phase θ of the random signal generators 3 and 10 of FIG.
The horizontal axis represents time, and the vertical axis represents the random phase value θ calculated from the bit pattern value R output from the encryption unit in FIG.
(T) is a value from -π [rad] to π [rad], and the in-phase and quadrature signal components θe and θ of the random signal generator are obtained.
o is θe (t) = cos θ (t), θo (t) = sin θ
(T). Note that in FIG. 5, 1 / f _R = 4 / f _S , and one block of the block password corresponds to 4 × 64 = 256 sample periods.

FIG. 6 is an explanatory view of the power spectrum of the embodiment of the present invention. FIG. 6-a shows the power spectrum of the input signal,
Figure 6-b is the power spectrum of the confidential signal, Figure 6-
c is the power spectrum of the demodulated signal, where the horizontal axis is the frequency and the vertical axis is the normalized power value. As is clear from FIG. 6, when an input signal having dominant signal components at about 900 Hz and about 1600 Hz is concealed in this embodiment,
As shown in Fig. B), the signal is converted into a signal having a large number of unspecified frequency components, which makes it difficult to eavesdrop. Further, when this secret-speech signal is demodulated by the return-talk method of this embodiment, a demodulated signal having almost the same frequency component as the input signal having the frequency component of FIG. 6-a is obtained as shown in FIG. 6-c. It is possible to demodulate the obtained input voice signal with good clarity.

Moreover, the exchange to the unspecified number of frequency components in FIG. 6-b) is performed by the 1.0 pattern configuration of the password data output from the secret password password conversion unit 2 in FIG. 1 and the value of the generation frequency f _R of each bit pattern. The secret password is 64
With bit length, at least 2 ⁶⁴ lines or more confidential communication is possible.

(Effects of the Invention) As described above in detail, in the confidential communication device,
Since the secret password on the sending side and the demodulation password on the receiving side are the same, it can be expected that it is difficult for anyone other than the password owner to decipher and eavesdrop on the confidential output.
Further, a secret-speaking method in which a voice input signal is subjected to quadrature product modulation with a cosine wave and a sine wave having a non-random random phase generated from password data values generated based on the same block password algorithm on the transmitting side and the receiving side, and Therefore, the confidential output signal is obtained by phase-modulating the voice input signal with a non-periodic random phase value, and the effect that the confidential output of anyone other than the password sharer cannot be deciphered or eavesdropped can be expected. Further, by configuring the orthogonalization unit with a digital filter, all digital signal processing of the confidential communication device can be performed, and the effect of easy miniaturization can be expected. Further, since the secret-speech method that can obtain the secret-speech output that differs depending on the bit pattern value of the encryption unit output and its generation frequency is used, the effect that the secret-speech communication having a sufficiently large number of secrecy lines can be expected can be expected.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIGS.
FIG. 4 is an explanatory diagram of a conventional technique, FIG. 5 is an explanatory diagram of a block password and a random signal in FIG. 1, and FIG. 6 is an explanatory diagram of an example of a power spectrum in FIG. 1 ... Secret password storage unit, 2 ... Secret password password generation unit, 3 ... Random signal generation unit, 4 ... Orthogonalization unit, 5, 6
…… Multiplication section, 7 …… Synthesis section, 8 …… Demodulation password storage section, 9 …… Demodulation password conversion section, 10 …… Random signal generation section, S …… Voice input signal, P …… Secret output, SS ...... Voice demodulation output.

Claims (1)

[Claims] 1. A) a secret password storage means for storing a secret password, and b) generating a block password of a data pattern consisting of 1 and 0 which is different from the previous one at regular intervals, with the secret password as an initial value. A secret password password conversion means, and c) corresponding to 1 and 0 of the block password,
In the case of the data of 1, the relationship represented by the formula (1) and in the case of the data of 0 represented by the formula (2), a random signal having a random phase value varying between −π and + π is generated, and Random signal generating means for generating a cosine wave having a cosine value corresponding to the random phase value and a sine wave having a sine value corresponding to the random phase value, and θ (nΔt) = θ ((n-1) Δt) + Πf _R / 2f _S ...... Equation (1) θ (nΔt) = θ ((n-1) Δt) -πf _R / 2f _S・ ・ ・ Equation (2) However, θ (nΔt) is a random phase at the current sampling time. , Θ ((n−1) Δt) is a random phase value at the sampling time immediately before, f _R is a data bit generation frequency in the block password, and f _S is a sampling frequency) d) an in-phase component of the input signal As orthogonal to it Orthogonalizing means for generating an alternating wave component; e) a multiplying means for multiplying the sine wave and the in-phase wave component to generate an in-phase output; and f) multiplying the cosine wave and the quadrature wave component. A confidential communication apparatus, comprising: a multiplication means for multiplying to generate a quadrature output; and g) a synthesizing means for taking a difference between the in-phase output and the quadrature output and transmitting the difference as a secret output.