JPH03187555A - Telephony device for secret call - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a confidential telephone device with an improved eavesdropping prevention function, and in particular, even if a third party uses a confidential telephone device of the same type, it will not interfere in the confidential telephone line. This invention relates to a confidential telephone device which can strictly protect the confidentiality of conversations between parties.

(Prior Art) Hitherto, so-called secret telephone devices have been proposed and have recently been put into practical use, which transmit and receive encrypted audio signals during telephone calls.

[Problem to be solved by the invention]

However, with the confidential telephone devices that have been used recently, there is a problem in that a third party can use the same type of confidential telephone device to intervene in the telephone line and eavesdrop on the confidential telephone calls between the parties. was there.

In addition, an improved confidential telephone device has been proposed that encrypts voice using an encryption key agreed upon between callers.
Even with this, there is a problem in that if the eavesdropper repeatedly enters the encryption key by trial and error, the encryption key will be decrypted and the eavesdropper will be able to use the encryption key to eavesdrop.

Therefore, in view of the above-mentioned 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 confidential telephone device of the same type, It is an object of the present invention to provide a secret telephone device that makes eavesdropping impossible even when the operating conditions of the device are met, that is, the device does not operate.

[Means to solve the problem]

According to the present invention, the device is connected to be inserted between a telephone and a telephone line, and encrypts and transmits the telephone voice, and also decrypts the encrypted voice input from the telephone line to restore the voice. A confidential phone device for making confidential calls includes a line switching means for switching between normal calls and confidential calls, a storage means for storing own device code and the device code of the destination, and own device code and the device of the destination. A transmitting/receiving means for transmitting and receiving a code, a voice encrypting/decoding means for encrypting and decoding the voice during a confidential call, and controlling the functions of the storage means, transmitting/receiving means, and voice encrypting/decoding means during a confidential call. and a control means for processing, when the destination equipment code received from the other party by the transmitting/receiving means matches the one registered in the storage means, the control unit is configured to process the other party's equipment code. There is provided a confidential telephone device comprising means for transmitting the telephone number back to the telephone number, and for switching and setting the line switching means to a confidential telephone call when the transmitting/receiving means receives the own device code transmitted back from the other party. be done.

[Effect]

According to the above-mentioned confidential phone device, when making a confidential call, the line switching means passes voice encryption and decoding to transmit and receive the voice, and the device code and the confidential code of the device itself and the destination are used to confirm the destination. The system also encrypts and decrypts the voice calls, so even if a third party uses the same type of confidential phone device, it is impossible for a third party to intervene in the confidential phone call due to a mismatch in the device code. This means that a confidential call can only be made between you and the other party you are talking to.

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

FIG. 1 is a block diagram of an embodiment of a confidential telephone device according to the present invention, FIG. 2 is a block diagram showing a more detailed configuration of the confidential telephone device and the state in which the telephone is connected to a telephone line, and FIG. It is a flowchart explaining the operation of the confidential communication device.

Referring to FIG. 1, the confidential telephone device 2 according to the embodiment of the present invention includes a voice encryption/decryption section 22, a control section 24, a storage section 26, a transmitting/receiving section 28, an input section 291, and a display section 292. The various parts are connected to each other as shown in FIG. The voice encryption/decryption section 22 is connected to each line switching section 31. which performs switching to the telephone side and the line side.
The functions of each part of the 0th order also connected to 32 will be explained with reference to FIG.

First, in FIG. 2, a confidential telephone device 2 according to the present invention is provided so as to be connectable to a telephone 1, and another confidential telephone device connectable to a counterpart telephone 5 via a telephone line 3 and further via an exchange 6. It is provided so that it can be connected to 2a. The confidential phone device 2 has a low-pass filter 21, which is connected to the telephone 1 via a relay 31, and cuts unnecessary frequency components other than voice from the signal input from the telephone 1. the required frequency (e.g. 300
Hz to 3,100 Hz).

The audio encryption/decryption unit 22 connected to this low-pass filter 21 is connected to the first low-pass filter 21 and the other second
The second low-pass filter 23 is provided for encrypting or decoding the signal that has passed through the low-pass filter 23 of It is provided as a filter means to cut out unnecessary frequency components.

Additionally, the confidential telephone device 2 includes a control unit 24 formed by a well-known CPU that performs various control functions to be described later, a device code DC assigned to each confidential telephone device that can be connected to each telephone, and a control unit. The ROM 25 stores 24 control programs, etc., the personal code ID assigned to each individual who is permitted to use the confidential telephone device, and the equipment code DC of the confidential telephone device of the party with whom the confidential telephone call is to be made in advance. A RAM 26 for sending and receiving data such as a personal code and a device code via a modem (hereinafter referred to as MODEM) 2B, an interface 27 for sending and receiving code information such as a personal code and a device code serially, an input/output interface for the MODEM 28 that sends and receives data such as device codes, etc. 29. Input unit 29 formed of a numeric keypad, card reading device, etc., for inputting a personal code, etc.
1. A display section 292 consisting of a liquid crystal display means, etc., which displays the mode of the telephone, provides guidance for call operation, etc., is provided as a means for driving a relay, and sends a driving signal to the relays 31 and 32 in response to a signal from the CPU 24. A driver 30, a relay 31, 32, a clock generator 33, etc., which is driven by a drive signal from the driver 30 and switches the connection between the telephone line 3, the secret telephone device 2, and the telephone 1. .

The confidential phone device 2a in FIG. 2 is also the confidential phone device 2.
It has the same configuration as , and is provided so as to be connectable to the telephone set 5 . Therefore, in each component of the secret telephone device W12, the same components as those in the secret telephone device 2 are indicated by adding the suffix "a" to the reference number in the device 2.

Next, with reference to the flowchart of FIG. 3, the operation of the secret telephone device 2 of this embodiment when used will be explained.

Here, a description will be given of how to use the confidential phone device 2 when party A uses telephone 1 and party B uses telephone 5 to make a confidential call.

Now, the confidential telephone device 2 on the party A's side is connected to the telephone 1 and the telephone line 3 via terminals 34 and 35. On party B's side, telephone 5 and line 3 are connected to confidential telephone device 2a via terminals 34a and 35a, similarly to party A.
setting the secret telephone device 2 or 2a to registration mode using the input section 291 or 291a (step ■);
A step in which the caller registers a predetermined personal code ID (for example, a 4-digit number) by the input section 291.291a and the device code DCB of the confidential telephone device 2a of the caller B side who is the other party on the A side. ■), and A on caller B's side.
The side device code DCA is registered, and a confidential code SC (for example, a 4-digit number) is agreed upon between caller A and caller 8.

Caller A and caller B first perform a normal telephone calling operation using their respective telephones 1 and 5.

Here, the relay 31.3 of the confidential telephone device 11ffi2 is
2 and the relays 31a and 32a of the confidential telephone device 2a are off (open position), so the telephone 1 is directly connected to the telephone 5 via the telephone line 3, and normal calls and conversations cannot be made. I can do it.

Here, when it becomes necessary to make a confidential call during a call, that is, to prevent other third parties from eavesdropping, callers A and B use their respective secret phone devices 2 and 2a. The device is activated by using, for example, a numeric keypad constituting the input means 291 and 291a of the device (step 2). As a result, the confidential telephone devices 2 and 2a are activated. Then, caller A and caller B input the personal code ID and the secret code SC between AB (a code indicating the state of secret talk) from the input sections 291 and 291a (step 2).

In the secret phone device 2, the personal code ID and the secret code S
When there is an input of C, the control unit 24.24a controls the RAM 26.
A check operation is performed to determine whether or not the personal code [D inputted in 26a is registered (step 2). If the personal code ID is registered, it is determined that the caller is qualified to use the confidential telephone device.

If the input personal code ID is not registered in the RAM 26.26a, the process returns to step (2). Next, on the caller A side, the control unit 24 reads the device code DCA of the secret telephone device W2 from the ROM 25,
MODEM 2 B sends the device code DCA of the confidential phone device 2 of the caller A side to the telephone line 3, and the device code DCB of the confidential phone device 2a of the text talker B side is similarly sent to the caller A side (step ■).

Next, when the confidential phone device 2 of the caller A receives the device code DCB sent from the caller B side via the MODEM 28 (step ■), the control unit 24 stores the device code DCB of the confidential phone device 2a in the RAM 26. Check to see if it is registered (step ■)
Here, if the device code DCB is registered, the received device code DCB is retransmitted to the party B side via MODEM2B (step [phase]).

On the other hand, the confidential telephone device 2a on the caller B side also modifies the device code DCA sent from the caller A side in the same way as described above.
24a, the control unit 24a stores the RAM 2
Whether the device code DCA is registered in 6a?fil
Here, the device code DC
If A is registered, the received device code DCA is
It is retransmitted to the confidential telephone device 2 of the party A through the ODEM 28a.

When the confidential telephone device 2 receives its own device code DCA, it compares it with its own device code OCA stored in the ROM 25 (step ①@).

If the two match, the secret phone device W2 itself is set to the secret phone mode (step @).

Therefore, the control unit 24 starts the driver 30 and turns on (closes) the relays 31 and 32, that is, this relay 3
1.32 is turned on, the voice signal input from the telephone 1 and the telephone line 3 is input to the low-pass filter 21 or 23 of the secret telephone device 2 (step 0).

At the same time, the control section 24 displays on the display section 292 via the input/output interface 29 that the secret telephone mode has been set.

On the other hand, the confidential telephone device 2a of the party B side similarly receives its own device code DCB, and if it is confirmed that it is the same as its own device code stored in advance in the ROM 25a, the confidential telephone device 2a Set itself to confidential phone mode (step @).

Note that the confidential telephone device 2 on the party A's side does not receive the device code of the party B and the device code of the party A from the confidential telephone device 2a within a certain period of time after the input operation to start the confidential telephone call. , the line will be forcibly disconnected if another device code is received.

Here, suppose a third party C uses a confidential telephone device using the same system on the telephone line! 2c (not shown) and try to eavesdrop directly on the telephone line.

When attempting to set the confidential telephone device 2C to the confidential mode in order to intervene and connect the confidential telephone device C to the line 3 between the confidential telephone devices 2.2a and eavesdrop, the device code DCC of the confidential telephone device 2C is set to the line 3. Therefore,
The device code DCC of the confidential phone device 2c is also received on the parties A and B, and therefore the operating conditions according to the above-mentioned operation flow are not satisfied for both the confidential telephone devices 2.2a of parties A and B. , the telephone line between telephone 1 and telephone 5 is disconnected. Therefore, the third party C cannot eavesdrop even if he uses the confidential telephone device 2c.

Furthermore, even if the device code of third party C is registered in the RAM 26.26a of the confidential telephone devices 2.2a of parties A and B, the confidential telephone devices 2 and 2a
If a device code other than one is received, the line will be disconnected.
In this case, for example, the confidential telephone device 2 has the device code DCB of the confidential telephone device 2a and the device code DC of the confidential telephone device 2C.
1. It receives its own device code DCA returned from C and the re-devices 2b and 2C. Due to the duplication of received data, the call is disconnected and therefore eavesdropping can be detected.

Next, the encryption and decryption of voice by the confidential telephone device 2.2a etc. will be explained.

FIG. 4 is a functional configuration diagram of the audio encryption/decryption section 22 or 22a.

The secret code SC manually generated in step (3) in FIG. 3 reads out the encryption conversion pattern stored in the ROM 25, which has been set in advance to correspond to the secret code, and inputs it to the clock generator block 33 (FIG. 2). be done. The audio transmitted from the telephone 1 is passed through a low-pass filter 21
Each bandpass filter (hereinafter, in FIG. 4, the bandpass filter is simply referred to as BPF) 2
It is input from 21A to 221E. Then, the band pass filter 221^ selects only the frequency components from 300 Hz to 860 Hz, and inputs them to a frequency modulator (hereinafter, this modulator will be referred to as MOD together with the illustration in FIG. 4) 222A. In the MOD 222A, the frequency pattern is converted from 1980 Hz to 1420 Hz, for example, according to the modulation frequency manually input by the clock generator block 33. In other words, the frequency of 300Hz is 14
20Hz, the 860Hz frequency is converted to 1980Hz. Bandpass filter 221B and MOD22
2B is 860Hz to 1420) (z frequency is 19
The frequency is converted from 80Hz to 2540Hz.

Similarly, bandpass filter 22IC and MOD
In 222C, the frequency from 1420Hz to 1980Hz is converted to the frequency from 300Hz to 860Hz, and the BPF
221D and MOD222D from 1980Hz to 25
Frequency up to 40Hz is 2540Hz to 3100Hz
BPF221E and MOD2
In 22E, frequencies from 2540Hz to 3100Hz are converted to frequencies from 860Hz to 1420Hz. And each BPF221A to 221E
When the audio signals converted by the MODs 222A to 222E are combined by the mixer 223, they become encrypted audio signals. The frequency components of this audio signal are divided into five and replaced, so even if this is extracted and played back, it will only sound different from the original audio. This audio signal is transmitted to the telephone set 5 via the telephone line 3. telephone 5
On the side, the audio signal is manually input to the audio encryption/decryption unit 22a via the low-pass filter 23a. At this time, the low-pass filter 23a filters the necessary 30% of the audio signal.
Only frequency components from 0Hz to 3100Hz are allowed to pass, and other frequency components are cut.

Then, the audio signal that has passed through the low-pass filter 23a is transmitted to each band-pass filter 22 as shown in FIG.
It is input from 6A to 226E. At this time, each bandpass filter 226^ selects a frequency from 300H2 to 860Hz and inputs it to the MOD 225A. MOD2
25A, frequency components from 300 Hz to 860 Hz are converted from 1420 Hz to 1980 Hz according to the decoding conversion pattern set by the secret code SC. Similarly, the band pass filter 226B and MO0225B convert frequency components from 860H2 to 1420Hz to 2540H.
Convert from z to 3100Hz and bandpass filter
226C and MOD225C from 1420Hz to 19
Convert the 80Hz frequency component from 300Hz to 860Hz and use the bandpass filter 226D and MOD22
The 5D converts frequency components from 1980Hz to 2540Hz from 860Hz to 1420Hz, and the bandpass filter 226E and MOD225E convert frequency components from 2540Hz to 3100Hz from 1980Hz to 254Hz.
Convert to 0Hz.

In this way, each bandpass filter 226A to 226
The frequency components converted by E and MOD 2258 to 225E are combined in a mixer 224, and sent to the telephone 5 side, so that the voice input by the elderly person on the phone is reproduced on the telephone diary 5.

Encryption and decoding of the voice signal from the telephone 5 side to the telephone l side is also performed in the same manner as described above.

Note that the voice encryption and decryption methods used in the secret telephone device according to the present invention are not limited to the above embodiments, and other encryption and decryption methods may be used.

〔Effect of the invention〕

As can be understood through the description of the above embodiments, according to the confidential telephone device according to the present invention, even if an eavesdropper attempts to eavesdrop using a confidential telephone device of the same type, the conditions for setting the confidential mode are not satisfied. Therefore, the confidentiality of the confidential phone calls between the parties can be ensured without fail.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of a confidential telephone device according to the present invention, FIG. 2 is a block diagram showing a more detailed configuration of the confidential telephone device and the state in which the telephone is connected to a telephone line, and FIG. A flowchart explaining the operation of the confidential speech device, and FIG. 4 is a functional configuration diagram of the voice encryption/decryption section 22 or 22a. 1.5...Telephone, 2.2a...Secret telephone device, 2
2... Audio encryption/decryption unit, 24... Control unit, 26
...Storage unit, 28...Transmission/reception unit, 31.32...
Line switching section.

Claims (1)

[Claims] 1. Connected to be inserted between a telephone and a telephone line, it encrypts and transmits telephone voice and also decrypts encrypted voice input from the telephone line to restore voice. In a confidential telephone device for making confidential telephone calls, a line switching means for switching between a normal telephone call and a private telephone call, a storage means for storing the own device code and the device code of the destination of the call, and the own device code and the destination of the communication are provided. a transmitting/receiving means for transmitting and receiving a device code; a voice encrypting/decoding means for encrypting and decoding voice during a confidential call; and operations of the storage means, transmitting/receiving means, and voice encrypting/decoding means during a confidential call. and control means for controlling the other party, when the equipment code of the other party received by the transmitting/receiving means from the other party matches the one registered in the storage means. It is characterized by comprising means for transmitting the device code back to the called party, and for switching and setting the line switching means to a confidential call when the transmitting/receiving means receives the own device code sent back from the called party. Confidential telephone device. 2. The voice encryption/decoding means is characterized by comprising a group of bandpass filters and a group of modulators that separate the frequency of the voice into a plurality of bands, encrypt each band by frequency modulation, and decode the same. The secret telephone device according to claim 1. 3. The voice encryption/decoding means is characterized by consisting of a group of bandpass filters and a group of modulators that separate the frequency of the voice into a plurality of bands, encrypt each band by frequency modulation, and decode the same. The secret telephone device according to claim 1.