JP3009163B2 - Secret telephone device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a secure telephone device with improved eavesdropping prevention function, and in particular, a third party can intervene in a secure telephone line even if a third party uses the same type of secure telephone device. The present invention relates to a confidential telephone device that can prevent confidentiality of conversation between parties by preventing the telephone conversation from being performed.

(Prior art)

2. Description of the Related Art Conventionally, a so-called secret telephone apparatus has been proposed in which a voice signal is encrypted and transmitted / received in a telephone call,
It has been used recently.

[Problems to be solved by the invention]

However, according to the recently used confidential telephone device, there is a problem that a third party can intervene in the telephone line using the same confidential telephone device and eavesdrop on the confidential call between the parties. Was.

In addition, although an improved secret telephone device that encrypts voice with an encryption key negotiated between the callers has been proposed, even if an eavesdropper repeats the encryption key input by trial and error, the encryption key may be changed. Has been decrypted, and eavesdropping can be performed using the encryption key.

Therefore, in view of the above-described problems, the main object of the present invention is that even if a third party attempts to eavesdrop on a telephone line using a third secret telephone device of the same method, the third secret telephone It is an object of the present invention to provide a confidential telephone device in which the operating condition of the device is not satisfied, that is, the device does not operate and eavesdropping is impossible.

[Means for solving the problem]

According to the present invention, it is connected so as to be inserted between the telephone and the telephone line, encrypts and transmits the telephone voice, and decrypts the encrypted voice input from the telephone line to restore the voice, Line switching means for switching between a normal call and a secret call, a storage means for storing its own device code and a device code of a called party, and a device code of its own device and a called device A transmission / reception means for transmitting / receiving a code, a voice encryption / decryption means for encrypting / decoding a voice during a secret conversation, and controlling an operation of the storage means, the transmission / reception means, and a voice encryption / decryption means during a secret conversation. Control means for processing, when the destination device code received from the other party by the transmission / reception means coincides with the one registered in the storage means. The line switching means is switched to the secret conversation only when the own device code returned and transmitted from the other party is received by the transmitting / receiving means. , A secret telephone device for disconnecting the telephone line when there is a mismatch is provided.

[Action]

According to the above-mentioned secret telephone device, at the time of a secret call, voice transmission / reception is performed through the voice encryption / decryption by the line switching means, and the destination is confirmed using the device code and the secret code of the self and the destination. And encrypts and decrypts the call voice, so that even if a third party uses the same type of secret telephone device, the third party can intervene in the secret call due to a mismatch in the device code. It is not possible to perform a private conversation only between yourself and the other party.

Hereinafter, the present invention will be described in more detail based on embodiments shown in the accompanying drawings.

FIG. 1 is a block diagram of an embodiment of a secret telephone device according to the present invention, FIG. 2 is a block diagram showing a more detailed configuration of the secret telephone device, and a state where the telephone is connected to a telephone line.
FIG. 3 is a flowchart for explaining the operation of the secret talk apparatus.

Referring to FIG. 1, a secret telephone device 2 according to an embodiment of the present invention includes a voice encryption / decryption unit 22, a control unit 24, and a storage unit 2.
6, a transmission / reception unit 28, an input unit 291 and a display unit 292, and the respective units are mutually connected as shown in FIG. The voice encryption / decryption unit 22 is also connected to respective line switching units 31 and 32 for switching between the telephone side and the line side. Next, the function of each part will be described with reference to FIG.

First, referring to FIG. 2, a secret telephone device 2 according to the present invention will be described.
Is provided so as to be connectable to the telephone 1, and is also connectable to another secret telephone device 2a that can be connected to the other party's telephone 5 via the telephone line 3 and further through the exchange 6. The secret telephone device 2 has a low-pass filter 21. The low-pass filter 21 is connected to the telephone 1 via a relay 31, and cuts off unnecessary frequency components other than voice in a signal input from the telephone 1. Required frequency (for example, 300Hz to 3,100
Hz) only.

A voice encryption / decryption unit 22 connected to the low-pass filter 21 is provided for encrypting or decrypting a signal that has passed through the first low-pass filter 21 and another second low-pass filter 23. The filter 23 is provided as filter means for cutting unnecessary frequency components out of the signal encrypted by the voice decoding unit 22 and the voice signal received via the telephone line 3.

The secret telephone apparatus 2 includes a control unit 24 formed by a well-known CPU, which performs various control operations to be described later, and a device code DC assigned to each secret telephone apparatus that can be connected to each telephone.
And a ROM 2 storing a control program of the control unit 24 and the like.
5. A RAM 26 for storing a personal code ID assigned to each individual who is permitted to use the secret telephone device and a device code DC of the secret telephone device of the other party who makes the secret telephone call in advance, and a modem (hereinafter referred to as MODEM) 28. An interface 27 composed of an SIO for serially transmitting each code information such as a personal code and a device code via the NET, a MODEM 28 for transmitting and receiving data such as a device code, an input / output interface 29, a numeric keypad and a card reader, etc. An input unit 291 for inputting a personal code and the like; a display unit 29 composed of liquid crystal display means and the like for displaying a telephone mode, providing guidance on a call operation, and the like.
2. A driver 30 which is provided as a means for driving the relay and sends a drive signal to the relays 31 and 32 by a signal from the CPU 24, is driven by a drive signal from the driver 30, and is connected to the telephone line 3 and the secret telephone device 2; Relays 31 and 32 for switching connection with telephone 1, clock generator 33
And so on.

The secret telephone device 2a in FIG.
And is provided so as to be connectable to the telephone 5. Therefore, the same components of the secret telephone apparatus 2 as those of the secret telephone apparatus 2 are indicated by the reference numerals of the apparatus 2 with the suffix “a” added thereto.

Next, the operation when the secret telephone device 2 of the present embodiment is used will be described with reference to the flowchart of FIG.

Here, how the confidential telephone device 2 is used when the caller A uses the telephone 1 and the caller B uses the telephone 5 to make a secret call will be described.

By the way, the telephone 1 and the telephone line 3 are connected to the secret telephone device 2 of the caller A via terminals 34 and 35. Caller B
In the same way as the A side, the telephone 5 and the line 3
Are connected via terminals 34a and 35a. The caller A and the caller B have previously entered the input unit 291 of the secret telephone device 2 or 2a.
Alternatively, the secret telephone device 2 or 2a is set to the registration mode using 291a (step). Using the input units 291 and 291a, the caller registers a personal code ID (for example, a 4-digit number) predetermined by the caller, and the device code DCB of the secret telephone device 2a of the caller B, which is the call partner, on the A side ( Step), the caller B registers the device code DCA of A. Then, the confidential code SC between the caller A and the caller B
(For example, a four-digit number).

Talker A and Talker B first have their respective telephones 1 and 5
Performs a normal telephone call operation at.

Here, since the relays 31 and 32 of the secret telephone device 2 and the relays 31a and 32a of the secret telephone device 2a are off (open position), the telephone 1 is directly connected to the telephone 5 via the telephone line 3. And can make normal calls and calls.

If you need to make a confidential call during a call, that is, you don't want someone else to eavesdrop on it,
The caller A and the caller B use the input keys 291 and 291a of the confidential telephone devices 2 and 2a, for example, to operate the devices using ten keys (step). For this, for example, # 1 is depressed by a ten key. by this,
The secret telephone devices 2 and 2a are activated. Then, the caller A and the caller B input the secret code SC (code indicating the state of performing the secret talk) between the personal code ID and AB from the input units 291 and 291a (step). In the secret telephone device 2,
When the personal code ID and secret code SC are input, the control unit
24 and 24a perform a checking operation to check whether or not the personal code ID input to the RAMs 26 and 26a is registered (step). If the personal code ID is registered, it is determined that the caller is qualified to use the secret talk device. If the entered personal code ID is not registered in the RAM 26, 26a, the process returns to the step. Next, on the side of the caller A, the control unit 24 reads the device code D of the secret telephone 2 from the ROM 25.
The CA is read out, and the equipment code DCA of the telephone A of the caller A is transmitted to the telephone line 3 by the MODEM 28 via the interface 27, and the telephone B of the talker B is also transmitted to the telephone B.
The device code DCB of a is transmitted to the talker A side (step).

Next, when the device code DCB transmitted from the party B is received via the MODEM 28 (step S), the control unit 24 stores the secret phone device 2a in the RAM 26.
A check is performed to confirm whether or not the device code DCB is registered (step). Here, if the device code DCB is registered, the received device code DCB is
The data is retransmitted to the party B via the DEM 28 (step).

On the other hand, in the same manner as described above, when the device code DCA transmitted from the device A is received via the MODEM 24a, the control unit 24a also determines whether the device code DCA is registered in the RAM 26a. Check to make sure that
Here, if the device code DCA is registered, the received device code DCA is retransmitted to the secret telephone device 2 of the caller A via the MODEM 28a.

When the private telephone device 2 receives its own device code DCA, it compares with the own device code DCA stored in the ROM 25 (step).

If they match, the secret communication device 2 is set to the secret communication mode (step).

Therefore, the control unit 24 activates the driver 30 and
Turn on and close 31 and 32. That is, when the relays 31 and 32 are turned on, the audio signals input from the telephone 1 and the telephone line 3 are transmitted to the low-pass filter 21 or 23 of the private telephone 2.
(Step). Control unit 24
Displays on the display unit 292 via the input / output interface 29 that the secret talk mode has been set.

On the other hand, the secret telephone 2a on the side of the caller B also receives its own device code DCB in the same manner, and if it is confirmed that it is the same as its own device code stored in the ROM 25a in advance, the secret telephone 2a Set itself to secret talk mode (step).

In addition, after the input operation of the start of the confidential conversation, the confidential telephone device 2 of the caller A does not send the device code of the communicator B and the device code of the caller A from the confidential telephone device 2a within a predetermined time. When a device code or the like is received, the line is forcibly disconnected.

Here, it is assumed that a third party C uses a secret telephone device 2c (not shown) of the same system on a telephone line and attempts wiretapping directly from the telephone line. In order to intervene and connect the secret telephone device C to the line 3 between the secret telephone devices 2 and 2a to connect and wiretap, the device code DCC of the secret telephone device 2c is set to the line mode. Therefore, the callers A and B also receive the device code DCC of the secret telephone device 2c. Therefore, the secret telephone devices 2 and 2a of the callers A and B are also described above. Since the operating condition according to the operation flow is not satisfied, the telephone 1
The telephone line between the telephone and the telephone 5 is disconnected. Therefore, even if the third party C uses the secret telephone device 2c, it cannot be eavesdropped.

Further, even if the device codes of the third parties are registered in the RAMs 26 and 26a of the telephones 2 and 2a of the callers A and B, the telephones 2 and 2a will have a device code other than two at a given time. Is received, the line is disconnected. In this case,
For example, the secret telephone device 2 is the device code DC of the secret telephone device 2a.
B, the device code DCC of the secret telephone device 2c and its own device code DCA returned from both devices 2b and 2c will be received, and the duplication of the received data will cause the call to be cut off, so that eavesdropping can be known. .

Next, encryption and decryption of voice by the secret telephone devices 2 and 2a will be described.

FIG. 4 is a functional configuration diagram of the voice encryption / decryption unit 22 or 22a.

The encryption conversion pattern stored in the ROM 25 set in advance corresponding to the secret code is read out by the secret code SC input in the step of FIG. 3 and input to the clock generator block 33 (FIG. 2). You. The voice transmitted from the telephone 1 is passed through a low-pass filter 21 to each band-pass filter (hereinafter, the band-pass filter is abbreviated as BPF in FIG. 4) 221A to 221.
Entered in E. And the bandpass filter 221A is 3
Only the frequency components from 00 Hz to 860 Hz are selected and input to a frequency modulator (hereinafter, this modulator is described as MOD together with FIG. 4) 222A. In the MOD 222A, for example, it is converted into a frequency pattern from 1980 Hz to 1420 Hz according to the modulation frequency input from the clock generator block 33. That is, a frequency of 300 Hz is converted to 1420 Hz, and a frequency of 860 Hz is converted to 1980 Hz. Bandpass filter 221B
And MOD222B, the frequency from 860Hz to 1420Hz is changed from 1980Hz
Converted to frequencies up to 2540 Hz. Similarly, for the bandpass filters 221C and MOD222C, 1420Hz to 1980Hz
Is converted from 300 Hz to 860 Hz, and the BPF221
For D and MOD222D, the frequency from 1980 Hz to 2540 Hz is 2540
Hz to 3100Hz, BPF221E and MOD
For 222E, the frequency from 2540Hz to 3100Hz is from 860Hz to 142
It will be converted to a frequency up to 0 Hz. And each B
The audio signals converted by the PFs 221A to 221E and the MODs 222A to 222E are encrypted by the mixer 223 to become encrypted audio signals. Since the frequency component of this audio signal is divided into five parts and exchanged, even if this audio signal is taken out and reproduced, it can only be heard as a sound different from the original audio. This audio signal is transmitted to the telephone 5 via the telephone line 3. On the telephone 5 side, the voice signal is input to the voice encryption / decryption unit 22a via the low-pass filter 23a. At this time, the low-pass filter 23 a
Pass only 3100Hz frequency components and cut other frequency components. Then, the audio signal that has passed through the low-pass filter 23a is input to each of the band-pass filters 226A to 226E as shown in FIG. At this time, each band-pass filter 226A selects a frequency from 300 Hz to 860 Hz and inputs it to the MOD 225A. In MOD225A, the secret story code
The frequency component from 300 Hz to 860 Hz is converted from 1420 Hz to 1980 Hz according to the decoding conversion pattern set by the SC.
Similarly, 860Hz for bandpass filter 226B and MOD225B
To convert the frequency component of 1420Hz from 2540Hz to 3100Hz,
1 from 1420Hz for bandpass filter 226C and MOD225C
Converts 980Hz frequency component from 300Hz to 860Hz, and bandpass filters 226D and MOD225D from 1980Hz to 2540Hz
Is converted from 860 Hz to 1420 Hz, and the bandpass filters 226E and MOD225E convert the frequency component from 2540 Hz to 3100 Hz from 1980 Hz to 2540 Hz.

Thus, each bandpass filter 226A to 226E and
The frequency components converted by MOD225A to 225E are
The call is synthesized at 24 and sent to the telephone 5 side to make the caller A
Will be reproduced in the telephone book 5.

The encryption / decryption of the audio signal from the telephone 5 to the telephone 1 is performed in the same manner as described above.

It should be noted that the method of encrypting and decrypting the voice used in the secret telephone device according to the present invention is not limited to the above-described embodiment, but may be another encryption or decryption method.

〔The invention's effect〕

As can be understood from the above description of the embodiment, according to the secret telephone apparatus according to the present invention, even if an eavesdropper tries to eavesdrop using the secret telephone apparatus of the same system, the setting condition of the secret mode is not satisfied. Therefore, it is impossible to eavesdrop, so that the confidentiality of the call by the confidential telephone call between the parties can be surely secured.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of a secret telephone apparatus according to the present invention, FIG. 2 is a block diagram showing a more detailed configuration of the secret telephone apparatus and a state in which the telephone is connected to a telephone line, and FIG. FIG. 4 is a flow chart for explaining the operation of the secret talk apparatus, and FIG. 4 is a functional block diagram of the voice encryption / decryption unit 22 or 22a. 1, 5, telephone, 2, 2a secret telephone device, 22 voice encryption / decryption unit, 24 control unit, 26 storage unit, 28
... Transceiving unit, 31, 32 ... Line switching unit.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-64-54849 (JP, A) JP-A-49-119502 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04M 1/68

Claims (3)

(57) [Claims] 1. A telephone system which is connected so as to be inserted between a telephone and a telephone line, encrypts and transmits telephone voice, and decrypts encrypted voice inputted from the telephone line to restore the voice. A line switch means for switching between a normal call and a secret call, a storage means for storing its own device code and a device code of a called party, and a device code of its own device and a called device. Transmission / reception means for transmitting / receiving data, encryption / decryption means for voice for encrypting / decoding voice during a secret talk call, control processing of the storage means, transmission / reception means, and voice encryption / decryption means during a secret talk call Control means, and the control means only controls when the called device code received from the called party by the transmitting / receiving means matches the code registered in the storage means. Sending the other party's device code back to the other party, and setting the line switching means to be a secret conversation only when the own device code returned and transmitted from the other party is received by the transmitting / receiving means, A secret telephone device that disconnects the telephone line when there is a mismatch. 2. The secret telephone device according to claim 1, wherein said control means disconnects the telephone line when receiving a plurality of the same device code within a predetermined time. 3. The voice encryption / decryption means comprises a band-pass filter group and a modulator group for separating a voice frequency into a plurality of bands, encrypting each frequency band by frequency modulation, and decoding. 2. The method according to claim 1, wherein
Or the secret telephone device according to claim 2.