JPH08293915A - Telephone set with cryptographic function - Google Patents

Abstract

PURPOSE: To shorten data length set as the target of encipherment, to simplify a ciphering device and to facilitate miniaturization by ciphering the specific bit of a digital audio signal. CONSTITUTION: An analog audio signal is inputted to a transmitter 1 and it is converted into the digital audio signal by an A/D converter 2 on a transmission side. The digital audio signal is divided into the data to be cryptography- coded and the one not being cryptography-coded by a data divider 9. The data to be cryptography-coded is inputted to a cryptographic encoder 3, then, cryptography-coded. The cryptography-coded data and the data not being cryptography-coded are inputted to a data coupler 10, then, the data are coupled with each other, and this coupled data is transmitted. The data received by a reception side is divided by a data divider 11, and the cryptography-coded data is decoded by a cryptographic decoder 6. The data decoded in such way and the data not being cryptography-coded are coupled with each other by a data coupler 12, then, the digital audio signal is generated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a telephone with an encryption function having a secret talking function.

[0002]

2. Description of the Related Art In order to prevent the contents of communication from being heard over a telephone line, a confidential communication device is used. A secret communication device is provided corresponding to each telephone terminal, a voice signal is converted to an encrypted signal by this secret communication device, and encrypted communication is performed between the confidential communication devices of the telephone terminals to perform secret communication.

In a conventional analog communication system having a confidential communication function, a frequency spectrum array of a voice signal is arranged on the transmitting side according to a predetermined rule, and the obtained encrypted voice signal is passed through a communication line. A cryptographic communication system using voice scrambling has been put into practical use, in which the encrypted voice signal is transmitted to the receiving side, and the received encrypted voice signal is reversely arranged based on the same rules as the transmitting side to restore the original voice signal. There is.

Also in a digital communication system,
A system that encrypts and transmits voice has been proposed.
FIG. 7 is a block diagram showing a circuit configuration of a conventional telephone with a confidential communication function. On the transmitting side, the analog voice signal is input to the transmitter 1. The input analog audio signal is A
It is converted into a digital audio signal by the D converter 2. The digital audio signal is converted into an encryption code by the encryption encoder 3. The data for cryptographic encoding by the cryptographic encoder 3 is controlled by the control unit 4. The encrypted digital voice signal is connected to a switch (not shown) via the interface 5.

On the receiving side, data is received from the exchange through the interface 5. The received data is
It is encrypted and decrypted by the encryption / decryption device 6 and converted into a digital audio signal. The data for encryption / decryption by the encryption / decryption device 6 is controlled by the control unit 4. The decoded data is converted into an analog voice signal by the DA converter 7 and output by the receiver 8.

[0006]

However, in the above communication system, in order to realize the confidential communication function, the voice scrambled voice used in the above analog communication system is transmitted by the voice scramble device by the analog circuit. Therefore, there is a problem that the device scale becomes large. Further, there is a problem that the encryption device becomes complicated when the encoded voice is encrypted.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a telephone with an encryption function that solves the above problems.

In order to achieve the above object, the present invention provides an AD conversion means for converting an analog voice signal input from a transmitter into a digital voice signal in a telephone having an encryption function for encrypting and transmitting a voice signal. A data dividing unit that divides the digital audio signal into data that is cryptographically encoded and data that is not cryptographically encoded, cryptographic encoding unit that only encrypts specific data, and cryptographically encoded data and cryptographically encoded data. Data combining means for combining the non-encrypted data, an interface for connecting the combined data to the exchange, and a data dividing means for dividing the received data into the encrypted data and the non-encrypted data. , Encryption / decryption means for decrypting encrypted data, and encrypted / decrypted data And data combining means combining the have data, and the combined digital audio signal constitute a cryptographic function telephone and a DA conversion means for converting an analog audio signal.

[0009]

With the above construction, the transmitting side converts the analog voice signal into a digital voice signal and divides the digital voice signal into cryptographically encoded data and cryptographically unencoded data. Cryptographically encode data to be cryptographically encoded. The division of data and the cryptographic encoding of data are controlled. The data to be cryptographically encoded changes at any time, and the pattern for encryption is also controlled. The data is transmitted by combining the encrypted data and the non-encrypted data. The receiving side receives the data that has passed through the communication channel, divides the received data into encrypted coded data and unencrypted data, and decrypts the encrypted coded data. I do. The encrypted data and the non-encoded data are combined. The combined data becomes a digital voice signal, and the digital voice signal is converted into an analog voice signal and sent to the handset.

By encrypting a specific bit of the digital voice signal, even if the encrypted signal is an analog signal, the voice becomes completely different from the original voice, and the effect of encryption can be obtained. For this reason, when the telephone line is intercepted, normal voice cannot be reproduced, and the confidential communication function can be realized even for a third party.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

In the drawings, the same parts are designated by the same reference numerals.

FIG. 1 is a block diagram showing a circuit configuration of a telephone with an encryption function which is an embodiment of the present invention. 2 is a waveform diagram of the original voice signal, FIG. 3 is a waveform diagram of the voice signal in which the most significant bit is coded, FIG. 4 is a diagram of the envelope of the original voice signal, and FIG. 5 is the most significant 1 bit of the voice signal. FIG. 6 is a diagram of an envelope in which the most significant 2 bits of the audio signal are encrypted.

Specific bits of the digital audio signal, eg P
If several bits are wrong from the most significant bit in the CM signal,
When it is decoded into an analog voice signal, the voice becomes completely different. The voice is encrypted by making use of such characteristics. FIG. 2 shows the original waveform of the digital audio signal, and FIG. 3 shows the waveform in which the most significant bit is coded. It can be seen that if the most significant bit is coded, the waveform becomes completely different from the original waveform, making it difficult to eavesdrop.

On the transmitting side, an analog voice signal is input to the transmitter 1, and the analog voice signal is converted into a digital voice signal by the AD converter 2. The digital audio signal is
The data divider 9 divides the data into cryptographically encoded data and non-cipherally encoded data. Here, the data to be cryptographically encoded is the most significant bit in the PCM signal.
The data to be cryptographically encoded is input to the cryptographic encoder 3, and the control unit 4 controls the cryptographic data to be cryptographically encoded. The data encrypted by the encryption encoder 3 and the non-encrypted data output from the data divider 9 as they are are input to the data combiner 10 to combine the data.

The combined data is interface 5
Is connected to an exchange (not shown) and is transmitted.

On the receiving side, the data received from the exchange through the interface 5 is divided by the data divider 11 into encrypted data and unencrypted data. The encrypted data is input to the encryption / decryption device 6 and the encryption is decrypted. The encryption / decryption device 6 is controlled by the control unit 4. Encryption / decryption device 6
The data decrypted by the code and the data not encrypted are combined by the data combiner 12 into a digital audio signal. Digital audio signal is D
The analog audio signal is converted by the A converter 7 and output from the handset 8. Since the data dividers 9 and 11 and the data combiners 10 and 12 process data of only the most significant bit, they can be easily configured.

As a result of the above embodiment, the encrypted voice signal retains the envelope information of the original voice. FIG. 4 is a diagram of the envelope of the original audio signal, and FIG. 5 is a diagram of the envelope in which the most significant 1 bit of the audio signal is encrypted.

In the above embodiment, the envelope information can be hidden by making the bits to be encrypted from the most significant bit to several bits, for example, 2 bits. FIG.
It is a figure of the envelope which encrypted the most significant 2 bits of an audio | voice signal.

[0020]

As described above, according to the configuration and method of the present invention, a specific bit of a digital audio signal is encrypted, so that the entire audio coded signal is encrypted, The data length to be encrypted is short,
The encryption device is simplified and the scale of the encryption device can be easily reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a telephone with a secret talking function of the present invention.

FIG. 2 is a waveform diagram of an original audio signal.

FIG. 3 is a waveform diagram of a voice signal in which the most significant bit is cryptographically encoded.

FIG. 4 is a diagram of the envelope of the original audio signal.

FIG. 5 is a diagram of an envelope in which the most significant 1 bit of an audio signal is encrypted.

FIG. 6 is a diagram of an envelope in which the most significant 2 bits of an audio signal are encrypted.

FIG. 7 is a block diagram showing a configuration of a conventional telephone with a confidential communication function.

[Explanation of symbols]

 1 transmitter 2 AD converter 3 encryption encoder 4 controller 5 interface 6 encryption / decryption device 7 DA converter 8 receiver 9 data divider 10 data combiner 11 data divider 12 data combiner

Claims (1)

[Claims] 1. A telephone having an encryption function for encrypting and transmitting a voice signal, AD conversion means for converting an analog voice signal input from a transmitter into a digital voice signal, and the digital voice signal is cryptographically encoded. Data dividing means for dividing the data into non-encrypted data, encryption encoding means for encrypting only specific data, and data combining means for combining the encrypted data and the non-encrypted data, An interface for connecting the combined data to the exchange, a data dividing means for dividing the received data into encrypted coded data and non-encrypted coded data, and encrypted coded data. An encryption / decryption means for decryption, a data combining means for combining the encrypted data and the non-encrypted data, Cryptographic function telephone, characterized in that the digital audio signal together comprising a DA converter for converting an analog audio signal.