JP2011097332A - Private transmitter and receiver device, private transmitting and receiving method, and private communication apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a private transmitter by which marked confidentiality is achieved by a simple configuration or the like. <P>SOLUTION: The private transmitter includes: a band division filter which divides an analog voice signal according to bands; an A/D converter which converts a plurality of signals divided according to the bands by the band division filter into digital signals, respectively; a scramble processing circuit which performs scramble processing to the respective digital signals converted by the A/D converter; a D/A converter which converts the respective digital signals to which the scramble processing is performed by the scramble processing circuit into analog signals; and an SSB modulation circuit for performing SSB modulation to the respective analog signals converted by the D/A converter as a single sideband wave on the basis of a carrier wave with a predetermined amplitude to be transmitted. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a secret transmission device, a secret reception device, a secret transmission method, a secret reception method, and a secret communication device that convert analog speech into a digital signal and perform bit scramble processing to make it a secret story.

  In recent years, there has been an increasing demand for voice communication concealment in networks such as the Internet and mobile communication networks such as mobile phones. For example, in the case of voice communication via the Internet, digitized signal data is transmitted on the network in packet units. As the encryption technology at this time, IPsec (Security Architecture for Internet Protocol) or the like is used. However, since IPsec encrypts the protocol in the network layer, even if the application in the upper layer does not support encryption. While there is an advantage that security can be ensured, there is an operational problem in that advanced technical knowledge is required, such as requiring a large number of communication settings to be strictly matched between two communicating points.

  Also, in mobile phones, the secrecy of voice communication has naturally increased after the shift to the so-called third-generation mobile communication system, but all subscribers are forced to use the same encryption method. However, it is not always a complete security system, and in addition to the encryption technology provided in the mobile communication infrastructure itself, analog secret technology that can be used in the voice band (generally 200 to 3200 Hz) is used together. The secret resolving of the secret story because it is easy to predict human utterances (the feature is that there are many silent parts when the inflection of the utterance is seen as a signal wave) in the frequency inversion technology and phase transition inversion technology of The device was relatively easy to manufacture, and it was not always perfect as a secret technology.

  Therefore, it is possible to change the frequency spectrum division width between a band with a large amount of audio signal information and a band with a small amount of information, and it is easy to perform processing at both ends of the divided band and to create a program that can be easily created. An apparatus and a secret voice signal receiving apparatus are provided (Patent Document 1).

  The secret speech signal utterance device disclosed in Patent Document 1 is a secret speech signal generator that scrambles a speech signal on the frequency axis using a QMF (Quadrature Mirror Filter) that converts the speech signal into a frequency spectrum and divides it into a predetermined bandwidth. An encryption key converter that determines how to scramble on the frequency axis based on the input key number data, and the voice signal is divided into predetermined bands, and each of the divided bands A QMF analyzer that obtains a baseband signal of QMF, a baseband signal of each band output from the QMF analyzer based on a signal from the encryption key converter, A QMF synthesizer that receives a signal from the switcher, synthesizes it by QMF, and outputs the synthesized signal is provided.

  Further, the secret speech receiving and speaking device disclosed in Patent Document 1 is a secret speech signal receiving device that receives a secret speech signal obtained by applying a scramble on the frequency axis to a speech signal using QMF, and scrambles the speech signal. An encryption key converter for determining how to cancel the scramble on the frequency axis based on the data of the input key number corresponding to the key number used for the key number, and receiving the secret speech signal, A QMF analyzer that obtains a divided baseband signal by QMF and a baseband signal of each band output from the QMF analyzer from the encryption key converter. A switcher that replaces and outputs the signal based on the signal, and a QMF that receives the signal from the switcher, synthesizes the signal by QMF, and substantially outputs the audio signal. It is characterized in that a formed unit.

  In this way, by changing the frequency spectrum division interval between the band with a large amount of information of the audio signal and the band with a small amount of information, the number of divisions of the band with a large amount of information is increased and the number of divisions of the small band is decreased. This is an improvement in secrecy with the same number of divisions.

JP-A-7-74731

  However, even in the conventional technique, although the frequency spectrum dividing interval is changed, the entire frequency spectrum divided is scrambled and FM-modulated in the sense that it is limited to double concealment processing. In light of recent advances in secret cryptanalysis technology, it was still not sufficient.

Also, when a wide audio band is digitized and scrambled, audio data is lost in the communication path, and even when such a signal is descrambled, the original audio cannot be restored.
Furthermore, if the voice decoded by any complicated encryption remains as data on the computer, the decoded voice may be stolen by hacking or the like.

  Therefore, the present invention provides an analog secret technology that can be used in a voice band (generally 200 to 3200 Hz), a scramble process for low-bit signal data that does not impose a burden on the arithmetic processing system, and a modulation technology that is extremely difficult to tune ( A secret transmission device, a secret reception device, a secret transmission method, and a secret reception method, which can realize a remarkable secrecy with a simple configuration by making multiple use of SBB modulation) and encrypting the voice itself, An object of the present invention is to provide a secret communication system.

  The secret transmission apparatus according to the present invention includes a band division filter that divides an analog audio signal into bands, an A / D converter that converts a plurality of signals divided into bands by the band division filter into digital signals, and the D A scramble processing circuit that scrambles each digital signal converted by the A / A converter, a D / A converter that converts each digital signal scrambled by the scramble processing circuit to an analog signal, and a conversion performed by the D / A converter And an SSB modulation circuit for performing SSB modulation and transmitting each analog signal as a single sideband with a carrier wave having a predetermined amplitude as a reference.

  The secret receiver according to the present invention includes an SSB demodulator for demodulating a plurality of received waves, which are single sideband modulated for each band, into analog signals, and converting the demodulated analog signals into digital signals. A / D converter, a descrambling circuit for descrambling each digital signal converted by the A / D converter, and a D / A converter for converting each digital signal descrambled by the descrambling circuit to an analog signal And an adder for adding the analog signals converted by the D / A converter.

In addition, the secret communication device according to the present invention includes a band division filter that divides an analog audio signal into bands, an A / D converter that converts a plurality of signals divided by the band by the band division filter into digital signals, and A scramble processing circuit that scrambles each digital signal converted by the D / A converter, a D / A converter that converts each digital signal scrambled by the scramble processing circuit into an analog signal, and the D / A converter An SSB modulation circuit for SSB-modulating and transmitting each analog signal converted by SSB as a single sideband with a carrier wave having a predetermined amplitude as a reference;
An SSB demodulating circuit for demodulating a plurality of received waves that are single-sideband modulated for each band into analog signals, an A / D converter for converting the demodulated analog signals into digital signals, and the A / D A descrambling circuit for descrambling each digital signal converted by the converter, a D / A converter for converting each digital signal descrambled by the descrambling circuit to an analog signal, and a signal converted by the D / A converter The apparatus is characterized in that it is composed of a secret message receiving device provided with an adder for adding each analog signal.

The secret talk transmitting / receiving device according to the present invention has the following effects.
(1) To provide a transmission / reception apparatus with high confidentiality that is extremely difficult to tune to each transmission wave by passing SSBs having a plurality of carrier frequencies through a voice band of only a few kHz. Can do.
(2) Since bit scramble processing or encryption processing is performed for each divided voice band, for example, if separate keys are used for each band, decryption becomes more difficult, and the secrecy is further improved.
(3) Since the frequency band to be processed is a band of about several kHz assuming a human voice, it has the feature of significantly improving the secrecy as described above. The configuration of the apparatus and the processing system are simple.
(4) The configuration of the device according to the present invention is not limited to a specific layer (for example, IP layer) of the network and the infrastructure of the mobile communication network, and individual scramble keys and carrier frequencies can be agreed between users. The convenience is high.

It is explanatory drawing explaining one Embodiment of the secret story transmission / reception apparatus concerning this invention. It is explanatory drawing explaining the technical concept of the audio | voice processing in the secret transmission / reception apparatus concerning one Embodiment of this invention. It is explanatory drawing explaining the structural example of the secret transmission / reception apparatus concerning one Embodiment of this invention. It is explanatory drawing explaining the structural example of the secret transmission / reception apparatus concerning other embodiment of this invention. It is explanatory drawing explaining the structural example of the secret transmission / reception apparatus concerning other embodiment of this invention. It is explanatory drawing explaining the structural example of the secret transmission / reception apparatus concerning other embodiment of this invention. It is explanatory drawing explaining the structural example of the carrier generation circuit in the secret transmission / reception apparatus concerning this invention. It is explanatory drawing explaining the technical concept of the audio | voice processing in the secret transmission / reception apparatus concerning other embodiment of this invention. It is explanatory drawing explaining the technical concept of suppressed carrier wave single sideband modulation (SSB).

  Hereinafter, the form etc. for implementing the secret transmission / reception apparatus concerning this invention are explained in full detail.

  FIG. 1 shows an embodiment of a secret transmission / reception apparatus according to the present invention. The secret message transmission / reception device (secret message communication device) 100 receives a voice signal transmitted from the voice input / output terminal 112 of the mobile phone 110 via the cable 190, and performs a voice output signal via the cable 191 after processing to be described later. It transmits to the audio | voice input terminal (not shown) of the headphones 120. In addition, the voice of the speaker picked up from the microphone 121 attached to the headphone 120 is received from the voice output terminal (not shown) of the headphone 120 via the cable 192, and after the processing described later, via the cable 193. The data is transmitted to the voice input / output terminal 112 of the mobile phone 110.

  The headphone 120 is a general-purpose product that can be used by directly connecting to the voice input / output terminal 112 of the mobile phone via an input / output cable (not shown). In this case, the speech of the communication partner received by the mobile phone is transmitted from the input / output terminal 112 to the headphones 120 via the cable, and the speech of the speaker wearing the headphones 120 is transmitted from the mobile phone via the microphone 121 and the cable. Since it is transmitted to the input / output terminal 112, the speaker wearing the headphones 120 can talk with the communication partner in a so-called hands-free state. The mobile phone 110 may be of any model as long as it has a voice input / output terminal.

  Therefore, the secret transmission / reception device (secret communication device) 100 according to the present invention inputs / outputs analog speech that can be heard as an utterance to a speaker wearing the headphone 120, and to the mobile phone 110, This is an input / output of an analog voice that cannot be heard as an utterance. As can be easily understood in such an embodiment, the secret communication device according to the present invention inputs / outputs analog speech in the speech speech band, and thus is not limited to a specific communication infrastructure. Is extensive.

  Next, based on FIG. 2, the technical concept of the audio processing in the secret transmission / reception apparatus according to the embodiment of the present invention will be described. As described above, the secret message receiving apparatus according to the present invention is generally subject to processing of a speech voice band of 200 to 3200 Hz, and its spectrum (schematic diagram) is shown in FIG. In the present invention, the audio spectrum is divided into a plurality of bands for processing. As an example, as shown in FIG. 2 (b), it is divided into four parts at 200 to 400 Hz (band A), 400 to 800 Hz (band B), 800 to 1600 Hz (band C), and 1600 to 3200 Hz (band D). Can do. In the present embodiment, description will be made based on this four-division method for convenience of explanation, but the present invention is not limited to this, and may be divided into three or five divisions or other division numbers.

  One of the features of the audio processing in the present invention is that the SSB modulation processing is performed on each of the four divided audio bands shown in FIG. For example, as shown in FIG. 2 (c), for each of the four divided bands, SSB modulation is performed using a carrier wave of 600 Hz for the band A of 200 to 400 Hz, and for the band B of 400 to 800 Hz. SSB modulation is performed using a carrier wave of 1200 Hz, SSB modulation is performed using a carrier wave of 2400 Hz for a band C of 800 to 1600 Hz, and SSB modulation is performed using a carrier wave of 4800 Hz for a band D of 1600 to 3200 Hz.

Although not limited to this due to the nature of the present invention, the reference frequency (carrier frequency) for performing SSB modulation is approximately [600 Hz] for the 200 to 400 Hz band, respectively.
For the 400-800Hz band, approximately "1200Hz"
For the 800-1600Hz band, approximately "2400Hz"
For the 1600-3200Hz band, approximately "4800Hz"
Something is used. In addition, it is also characterized by using a carrier frequency close to each target band (in general terms, the carrier frequency for the A _{1 to} B ₁ [Hz] band is approximately A ₁ + B ₁ [ Hz], and the relationship between A _{1 to} B ₁ and the next target bands A _{2 to} B ₂ is A ₂ = 2A ₁ and B ₂ = 2A ₂ ). For this reason, in order to cut out the target band sharply, it is desirable to have a multi-stage filter configuration (digital processing with a DSP is also possible) so that time delay does not become a problem.

  In other words, it can be said that the secrecy is improved by applying SSB having a plurality of carrier frequencies in a voice band having only a few kHz.

  Note that SSB refers to a suppressed carrier single sideband (and its modulation scheme), and is a scheme for suppressing a carrier and one sideband in amplitude-amplitude modulation. The specific technical concept will be described with reference to FIG. First, FIG. 9A shows a spectrum (schematic diagram) in amplitude modulation. In FIG. 9A, since the signal level of the carrier wave is transmitted as it is as in general AM radio monaural broadcasting, the carrier wave is 50%. , And both sidebands (upper sideband: USB, lower sideband: LSB) each require 25% power. On the other hand, FIG. 9B shows a transmission spectrum of a suppressed carrier double sideband (DSB). Since DSB cancels the carrier wave, only transmission in both sidebands is required, and the transmission power is only half that of amplitude modulation. Further, FIG. 9 (c) shows a transmission spectrum of a suppressed carrier single sideband (SSB). In SSB, either one of the upper sideband or the lower sideband is used in the DSB. Therefore, half the power is required for the DSB. As described above, when transmission of the same baseband information is assumed, the SSB has a characteristic that only half of the occupied frequency band and one quarter of the high-frequency power are required for the amplitude-modulated wave.

  FIG. 3 shows a configuration example of the secret transmission / reception apparatus according to an embodiment of the present invention. As described above, in the embodiment of the present invention, the case where the speech band (approximately 200 to 3200 Hz) is divided into four is taken as an example, and therefore, the configuration in FIG. 3 is also divided into four bands. This configuration is merely an example for carrying out the present invention, and the band to be divided and the number of divisions are not limited thereto. The secret transmission / reception device 100 is roughly divided into a secret speech demodulation module 101 that demodulates a secret speech (transmission wave) transmitted from the mobile phone 110 via a cable, and a speaker's voice input from the microphone 121 attached to the headphones 120. And the secret voice modulation module 102 for modulating the voice to the secret voice.

  The secret speech demodulating module 101 divides a transmission wave (for example, a secret speech by a modulation module 102 described later) transmitted from the mobile phone 110 via a cable for each divided band (200 to 400 Hz in the example of FIG. 3). , 400 to 800 Hz, 800 to 1600 Hz, and 1600 to 3200 Hz) on a carrier wave (carrier), and SSB demodulation for each divided band of the transmission wave carried on the carrier For example, when 4-bit A / D sampling is performed for each divided band on the SSB demodulated transmission wave, 4-bit A / D sampler circuits 303a to 303d, and SSB demodulation circuits 302a to 302d for processing, Each band is a 4-bit digital signal sequence by the sampler circuits 303a to 303d. The descrambling circuits (decoding processing circuits) 304a to 304d that perform descrambling processing (decoding processing) on the signals of the scrambled signals and the signals descrambled by the descrambling circuits (decoding processing circuits) 304a to 304d for each band It comprises D / A converters 305a to 305d that perform A conversion, and an adder 306 that adds signals for each band output from the D / A converters 305a to 305d. The signal added by the adder 306 is sent to the headphones 120, for example, as a voice that can be easily heard by humans.

  Here, operation timings of SSB demodulation circuits 302a to 302d provided for each band, 4-bit A / D sampler circuits 303a to 303d, descrambling circuits (decoding processing circuits) 304a to 304d, and D / A converters 305a to 305d. Will be described. In this embodiment, since the band is divided into four bands of 200 to 400 Hz, 400 to 800 Hz, 800 to 1600 Hz, and 1600 to 3200 Hz, the SSB demodulating circuit 302a that processes the band of 200 to 400 Hz, 4-bit A / D Assuming that the operation cycle of the sampler circuit 303a, descrambling circuit (decoding processing circuit) 304a, and D / A converter 305a is 1, an SSB demodulating circuit 302b that processes a band of 400 to 800 Hz in the same cycle, 4-bit A / D The operation cycle of the sampler circuit 303b, the descrambling circuit (decoding processing circuit) 304b, and the D / A converter 305b is 2 (operates in twice the cycle). Similarly, the SSB demodulating circuit 302c that processes the band of 800 to 1600 Hz, the 4-bit A / D sampler circuit 303c, the descrambling circuit (decoding processing circuit) 304c, and the D / A converter 305c operate in a fourfold cycle, The SSB demodulating circuit 302d that processes the band of 1600 to 3200 Hz, the 4-bit A / D sampler circuit 303d, the descrambling circuit (decoding processing circuit) 304d, and the D / A converter 305d operate in 8 times the cycle.

  The secret speech modulation module 102, for example, uttered speech input from the microphone 121 and transmitted via a cable for each band (in the example of FIG. 3, four bands of 200 to 400 Hz, 400 to 800 Hz, 800 to 1600 Hz, and 1600 to 3200 Hz). Digital filters 307a to 307d, 4-bit A / D quantization circuits 308a to 308d for performing 4-bit A / D sampling on the audio signal divided for each band, and a quantization circuit Scramble processing circuits (encryption processing circuits) 309a to 309d that perform scramble processing (encryption processing) on the signals for each band that have become a 4-bit digital signal sequence by 308a to 308d, and a scramble processing circuit (encryption processing circuit) 309a The signal scrambled by ~ 309d D / A converters 310a to 310d for D / A conversion every time, and carrier generation for placing each band signal output from the D / A converters 310a to 310d on a carrier wave (carrier) for each band A circuit 301, SSB modulation circuits 311a to 311d for performing SSB modulation processing on each band carried by the carrier, and an adder 312 for adding signals for each band output from the SSB modulation circuits 311a to 311d It is composed of

  Operation timings of digital filters 307a to 307d, 4-bit A / D quantization circuits 308a to 308d, scramble processing circuits 309a to 309d, D / A converters 310a to 310d, and SSB modulation circuits 311a to 311d provided for each band. As in the case of the secret speech demodulation module 101, in the period in which the operation cycle of the 200 to 400 Hz band is 1, the one that processes the 400 to 800 Hz band is doubled and the 800 to 1600 Hz band is processed. The one that operates 4 times and the one that processes the 1600-3200 Hz band will operate at 8 times.

  FIG. 4 shows a configuration example of the secret transmission / reception apparatus according to another embodiment of the present invention. In the first embodiment, the number of band divisions is 4, and the case where all the module circuits assumed by the present invention are provided has been described. The second embodiment shows a configuration example that is not limited to the number of band divisions. Further, it will be described that the present invention can function without necessarily providing all of the module circuits described in the first embodiment.

  The secret message transmitting / receiving apparatus 400 converts, for example, a transmission wave (secret voice) transmitted from the mobile phone 110 via a cable into an SSB demodulation circuit 401 for performing SSB demodulation processing for each of a plurality of divided bands, and an SSB demodulated transmission wave. On the other hand, A / D conversion circuit 402 for performing A / D conversion of a plurality of bits for each divided band, and band synthesis for band-combining a signal for each band converted to a digital signal string of a plurality of bits by A / D conversion circuit 402 A secret speech demodulation module including a circuit 403 and a D / A conversion circuit 404 that performs D / A conversion on the output of the band synthesis circuit 403 and transmits it to a headphone 120 or a speaker (not shown), and is input from, for example, a microphone 121. A band dividing circuit 405 for dividing the speech voice transmitted through the cable into a plurality of bands and a voice signal divided into the bands. A / D conversion circuit 406 for performing A / D sampling of a plurality of bits, and D / A for performing D / A conversion on a signal for each band that has become a digital signal string of a plurality of bits by the A / D conversion circuit 406 A secret speech modulation module including an A conversion circuit 407 and an SSB modulation circuit 408 for performing SSB modulation processing on a signal for each band output from the D / A conversion circuit 407.

  Note that the SSB demodulator circuit 401, the A / D converter circuit 402, the A / D converter circuit 406, the D / A converter circuit 407, and the SSB modulator circuit 408 are separated for each band and operate so that the consistency of each band can be obtained. This is as described in the first embodiment.

  FIG. 5 shows a configuration example of a secret transmission / reception apparatus according to another embodiment of the present invention. Basically, the same component numbers are assigned to the same components as those in the secret transmission / reception apparatus shown in FIG. The difference from the secret message transmitting / receiving apparatus 400 shown in FIG. 4 is that a decryption circuit 501 is added in the secret voice demodulation module, and an encryption circuit 502 is added in the secret voice modulation module.

  For the decryption circuit 501 and the encryption circuit 502, for example, a sequential processing circuit using an M-sequence pseudo-random number generator that operates in an asynchronous manner can be used. That is, the bit string extracted from the M-sequence pseudo-random number generator updated at a constant cycle can be encrypted by performing an XOR (exclusive OR) operation on the original (original) bit string. At the time of decryption, the original bit string can be restored by subjecting the encrypted bit string to an XOR operation on the same bit string used at the time of encryption (taken from the M-sequence pseudorandom number generator). For example, in the case of processing 4 bits at a time as the original bit string, if the original bit string is “0110” and the bit string extracted from the M-sequence pseudorandom number generator is “1011”, it is obtained by the XOR operation process. The encrypted bit string is “1100”. On the other hand, when this encrypted bit string “1100” is subjected to an XOR operation using the same bit string (taken from the M-sequence pseudorandom number generator) “1011” used at the time of encryption, the original bit string “0110” is obtained. Can be restored.

  The decryption circuit 501 can be used as the descrambling circuits (decryption processing circuits) 304a to 304d in the first embodiment, and the encryption circuit 502 can be used as the scramble processing circuits (encryption processing circuits) 309a to 309d in the first embodiment. . In this case, in the first embodiment, since it is divided into four bands and digitized into a 4-bit bit string for each band, the M-sequence pseudo-random numbers generated and generated by the random number generator at a constant period are 16 bits. A long one is adopted, and for example, the upper 4 bits are extracted from the 16-bit random number and used as a key for encrypting each band.

  In the encryption process (scramble process), it is desirable to use random numbers generated in the same random number generation unit for each divided band. In other words, for typical encryption (bit scrambling), an exclusive OR operation process using the M-sequence pseudo-random number as described above can be considered. In this way, a scramble process based on a certain rule is performed. In updating the random number, the random number is not updated for one cycle (for example, four clocks) of the lowest frequency sound used in the band. By doing this, it is possible to prevent the occurrence of singular events that cannot be processed such that the bit values for each band after scrambling become all zero by chance, and the random numbers are updated frequently according to this rule. It is possible to realize encryption that is difficult for a third party to decipher.

  In addition, by inserting a signal that makes a meaningful signal between the sender and receiver in the vacant band, it can also be used for signals such as random number update signals, initialization signals when the motives are disrupted due to noise, etc. Good.

  FIG. 6 shows a configuration example of the secret transmission / reception apparatus according to another embodiment of the present invention. Basically, the same component numbers are assigned to the same components as those of the secret transmission / reception device 400 shown in FIG. 4 and the secret transmission / reception device 500 shown in FIG. The difference between the secret transmission / reception device 400 and the secret transmission / reception device 500 is that a carrier generation circuit 602 is added in the secret speech demodulation module.

  As the carrier generation circuit 602, for example, the circuit 700 shown in FIG. 7 can be used. As shown in FIG. 7, the carrier generation circuit 700 generates a carrier for each divided band by dividing the frequency by one half with respect to an oscillator that oscillates at 4800 Hz. This can also be adopted in the first embodiment. In this embodiment, the frequency of each carrier is in a multiplying relationship, but is not limited to the multiplying relationship, and the carrier frequency is arbitrarily set by providing an oscillator of each frequency. May be.

  The carrier generation circuit 700 includes a reference oscillator 701, 1/2 frequency dividers 702 to 704, VCOs (Voltage Controlled Oscillators) 705 to 708, and analog output circuits 709 to 712 for each band. Become.

  In the carrier generation circuit 700, the 4800 Hz clock transmitted from the reference oscillator 701 is sequentially divided by half by the 1/2 dividers 702 to 704 and input to the VCOs 705 to 708 as digital clocks. The As is clear from the figure, the VCO1 (705) has a 4800 Hz clock, the VCO2 (706) has a 2400 Hz clock, the VCO3 (707) has a 1200 Hz clock, and the VCO4 (708) has a 600 Hz clock. Each is entered. An analog sine wave is extracted from each VCO and input to analog output circuits 709 to 712, respectively. The analog output circuit 709 outputs a 4800 Hz carrier wave, the output circuit 710 outputs a 2400 Hz carrier wave, the output circuit 711 outputs a 1200 Hz carrier wave, and the output circuit 712 outputs a 600 Hz carrier wave.

  Although not shown in detail, in each of the voltage controlled oscillators 705 to 708, a phase comparator, an analog variable oscillator, and a comparator are connected in a feedback manner, and an analog sine wave having a desired frequency is extracted for each band. It is configured as follows.

  FIG. 7 shows a technical concept of voice processing in the secret transmission / reception apparatus according to another embodiment of the present invention. For example, in Example 1, when generating a plurality of carrier waves, ones of 600 Hz, 1200 Hz, 2400 Hz, and 4800 Hz were generated. However, in the present invention, the frequency of these carriers may be changed while being in a multiplying relationship, or a specific frequency may be allocated individually. FIG. 7 shows a method of making it difficult to analyze the carrier wave by shifting a certain value with respect to the carrier wave. The carrier frequency for carrying the 200 to 400 Hz divided band is 600 ± α. Further, the carrier frequency for carrying the divided band of 400 to 800 Hz is 1200 ± β, the carrier frequency for carrying the divided band of 800 to 1600 Hz is 2400 ± γ, and the carrier frequency for carrying the divided band of 1600 to 3200 Hz is 4800 ±. It is set as δ. This can be realized by using an oscillator of each frequency, and the shift widths α, β, γ, and δ of these bands are set in, for example, VCO1 (705) to VCO4 (708) in the carrier generator 700, respectively. be able to. Note that the multiplication relationship may be maintained and a configuration such as β = 2α, γ = 4α, and δ = 8α may be employed. Then, the shift widths α, β, γ, and δ of each band are shared as a secret key, for example, for each pair of secret transmission / reception devices. If comprised in this way, it will become more difficult to estimate the frequency of a carrier wave for every zone | band by a third party, and the confidential transmission / reception apparatus with higher confidentiality can be implement | achieved.

  As a reminder, all technical elements described in the claims, specification, abstract, and drawings are combinations in which at least some of these elements are mutually exclusive. Any combination other than the above can be a constituent element of the secret transmission / reception apparatus according to the present invention.

  Further, the present invention is not limited to any individual specific detailed description of the above-described embodiments. Further, the technical scope of the present invention is not limited only to the above description, but the extension thereof is specified by the description of the scope of claims, and substitutions or modifications equivalent to the scope of the claims are also included in the scope of the present invention. It is within the technical scope.

100 Secret voice transmission / reception device (Secret voice communication device)
DESCRIPTION OF SYMBOLS 101 Secret speech demodulation module 102 Secret speech modulation module 110 Mobile phone 120 Headphone with microphone 121 Microphone 190, 191, 192, 193 Signal cable 301 Carrier generation circuit 302a to 302d SSB demodulation circuit 303a to 303d 4-bit A / D sampler circuit 304a to 304d Descramble circuit (decoding circuit)
305a to 305d D / A converters 306 and 312 Adders 307a to 307d Digital filters 308a to 308d 4-bit A / D quantization circuits 309a to 309d Scramble processing circuits (encryption circuits)
310a to 310d D / A converters 311a to 311d SSB modulation circuit

Claims (9)

A band division filter that divides the analog audio signal into bands;
An A / D converter that converts each of a plurality of signals divided into bands by the band dividing filter into digital signals;
A scramble processing circuit that scrambles each digital signal converted by the D / A converter;
A D / A converter that converts each digital signal scrambled by the scramble processing circuit into an analog signal;
A secret talk transmitting apparatus comprising: an SSB modulation circuit for SSB-modulating and transmitting each analog signal converted by the D / A converter as a single sideband with a carrier wave having a predetermined amplitude as a reference . An SSB demodulating circuit for demodulating a plurality of received waves that are single-sideband modulated for each band into analog signals;
An A / D converter that converts each demodulated analog signal into a digital signal;
A descrambling circuit for descrambling each digital signal converted by the A / D converter;
A D / A converter that converts each digital signal descrambled by the descrambling circuit into an analog signal;
And a adder that adds the analog signals converted by the D / A converter.   A secret communication device comprising the transmission device according to claim 1 and the reception device according to claim 2. The band dividing filter is composed of digital filters 307a to 307d that divide an analog audio signal into 200 to 400 Hz band, 400 to 800 Hz band, 800 to 1600 Hz band, and 1600 to 3200 Hz band, respectively.
At the time of the SSB modulation, for each band, a carrier wave of 600 Hz for the 200 to 400 Hz band, 1200 Hz for the 400 to 800 Hz band, 2400 Hz for the 800 to 1600 Hz band, and 4800 Hz for the 1600 to 3200 Hz. The secret story transmitting apparatus according to claim 1, further comprising a carrier generating circuit for generating a message.   At the time of the SSB demodulation, for each band, a carrier wave of 600 Hz for the 200 to 400 Hz band, 1200 Hz for the 400 to 800 Hz band, 2400 Hz for the 800 to 1600 Hz band, and 4800 Hz for the 1600 to 3200 Hz. The secret story transmitting apparatus according to claim 2, further comprising a carrier generating circuit for generating a message.   A secret communication device comprising the transmission device according to claim 4 and the reception device according to claim 5. The band-splitting filter sets the carrier frequency for the A _{1 to} B ₁ [Hz] band to approximately A ₁ + B ₁ [Hz], and further includes the A _{1 to} B ₁ [Hz] band and the next target band. _2. The secret transmission device according to claim 1, wherein the relationship between A _{2 and} B ₂ [Hz] is designed so that A ₂ = 2A ₁ and B ₂ = 2A ₂ . At the time of the SSB demodulation, a carrier generation circuit is further provided for generating a carrier wave so that the carrier frequency is approximately A ₁ + B ₁ [Hz] for the A _{1 to} B ₁ [Hz] band for each band. The secret story transmitting apparatus according to claim 2, wherein   A secret communication device comprising the transmission device according to claim 7 and the reception device according to claim 8.

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