JPH0514339A - Confidential telephone device - Google Patents

Abstract

PURPOSE:To make interception of a cipher call in the automatic mode completely impossibly by means of the manual mode by differentiating a ciphering key in use from the automatic mode and the manual mode. CONSTITUTION:A manual ciphering key section 3-1 makes generation of a ciphered key by an automatic ciphering key section 3-2 impossible. Thus, when the ciphering call between a talking party and an opposite party is implemented by using a ciphering key of the automatic ciphering key section 3-2, even when the interception party tries to intercept the call by using the manual ciphering key section 3-1, there is no possibility of successful interception. Even when key entry is repeated in a cut-and-try way in the manual mode, the ciphering key is not accidentally coincident. Thus, the cipher telephone set is made up of a ciphering/decoding section 1 comprising a ciphering processing LSI, a ciphering key setting section 2 commanding the sequence of the replacement of N sets of signals to be decomposed therein, and a key section 3, from which a ciphering code is supplied. In order to make the ciphering key different, identifiers of both the talking party and the opposite party are subject to function processing in a secret way based on a random number or number of digits of the identifiers in a CPU is made different.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a confidential telephone device for ensuring safety and confidentiality. In particular, the present invention aims to reduce the possibility of wiretapping using the confidential telephone device.

[0002]

2. Description of the Related Art FIG. 5 is a schematic view for explaining prevention of wiretapping in a conventional confidential telephone device. As shown in the figure, in the confidential telephone device, the voice of the caller is encrypted and transmitted, and the other party decrypts and voices it. Prior to this call, the caller sends the encryption key K _a , the other party receives it, and sends the encryption key K _b to the caller. As a result, the key K _a + K _b common to the caller and the other party is used by the caller as an encryption key and the other party as a decryption key. The above encryption keys are usually automatically generated (automatic mode). And wiretapping is performed as follows.

A third party eavesdropper records a call encrypted by a recorder on a line between the caller and the other party.
After that, a recorder is installed in the same confidential telephone device as above, and the eavesdropper manually inputs the encryption key to enter the encryption key K.
Repeat until it matches _a + K _b . Therefore, in order to reduce the probability that these encryption keys and the manually set encryption keys match, as many combinations of encryption keys as possible are set.

[0004]

In the conventional confidential telephone device, in order to improve the convenience of use as described above,
For example, an encryption key and a decryption key can be manually set using a ten-key or the like (manual mode). Also, since as many encryption keys as possible are set, there is little possibility of manual wiretapping using this device. However, this conventional type confidential telephone device has a problem in that it cannot prevent an eavesdropper from accidentally eavesdropping by repeatedly inputting the encryption key in the manual mode.

Therefore, the present invention has been made in view of the above problems.
An object of the present invention is to provide a secret-speaking telephone device which prevents the secret of the automatic mode from being deciphered by the manual mode.

[0006]

FIG. 1 is a diagram showing the principle configuration of the present invention. In order to solve the above problems, the present invention provides an encryption / decryption unit 1 for encrypting and decrypting a voice signal, a manually set encryption key, or an automatically generated caller's encryption key and the other party's. A secret telephone device is configured having an encryption key setting unit 2 which synthesizes encryption keys and sets the encryption / decryption unit 1 in the encryption / decryption unit 1, and an encryption key unit 3 including a large number of the encryption keys. The encryption key unit 3 is provided with a manual encryption key unit 3-1 and an automatic encryption key unit 3-2.

The manual encryption key section 3-1 has an encryption key for manual setting. The automatic encryption key unit 3-2 is different from the manual encryption key unit 3-1 and has an encryption key for automatically generating each.

[0008]

According to the confidential telephone device of the present invention shown in FIG. 1, the encryption key of the automatic encryption key unit 3-2 cannot be created by the manual encryption key unit 3-1. Therefore, when the secret talk between the caller and the other party is performed in the automatic mode, that is, the encryption key of the automatic encryption key unit 3-2, the secret talk is performed in the manual mode in which the eavesdropper creates the encryption key by the manual encryption key unit 3-1. There is no possibility of wiretapping.

That is, even if a third party repeats key input in the manual mode by trial and error using the same confidential telephone device, the encryption key happens to coincide with the confidential key in the automatic mode. Is completely gone.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a diagram showing a confidential telephone device according to an embodiment of the present invention. The configuration of this figure will be described. The confidential telephone device 10 of this figure is a cryptographic processing LSI for decomposing signals into N frequency bands by, for example, a frequency scrambling method, replacing the decomposed N signals, and then synthesizing them.
And an encryption / decryption unit 1 including the
The encryption key setting unit 2 for instructing the order of replacing the N signals decomposed into the above, and the encryption key unit 3 supplied to the encryption key setting unit 2 for manually setting the encryption key when the manual mode is selected. CPU including the manual encryption key unit 3-1 of FIG. 3, an automatic encryption key unit 3-2 for automatically generating an encryption key, which is different from the manual encryption key unit 3-1 and the encryption key setting unit 2. 4, the system program section 5 for ensuring the overall operation of the confidential telephone device 10, the operation contents of the CPU 4 are displayed, and operations such as reading of an encryption key are performed on the manual encryption key section 3-1. And a display / operation unit 6 for performing the operation, a handset 7 including a voice codec for converting an audio signal into, for example, a digital electric signal and vice versa, which are connected to the encryption / decryption unit 1, and the encryption unit. Decoding / decoding unit 1
It includes a modem 8 that converts the signal encrypted by the above into an analog signal, modulates the signal, transmits the signal to the other party's confidential telephone device 20, and demodulates the signal in reverse. The other party's secret telephone device 20
Has the same configuration as the caller's device.

Further, a large number of encryption keys are provided in the manual encryption key section 3-1.
And an automatic encryption key unit 3-2, which are stored in, for example, a ROM. Manual encryption key section when manual mode is selected
The encryption key is read from 3-1 and when the automatic mode is selected, the encryption key is read from the automatic encryption key section 3-2. That is, if the signal is divided into N frequency bands, this permutation is N! And, in the past, this N! Out of n
Although the individual pieces are stored in the encryption key and are commonly read out in the manual mode and the automatic mode, according to the present embodiment, N!
Of the permutations of, the automatic encryption key part 3-2 has n encryption keys A
K1, AK2, ..., AKn are created and the manual encryption key unit 3-1
Then, n MK1, MK2 different from the encryption key
..., MKn is created.

The CPU 4 is composed of the codec, the modem,
In order to control data transmission and reception between the cryptographic processing LSIs, 6
It is realized by using 8000 series CPU. The encryption processing LSI of the encryption / decryption unit 1 is composed of a dedicated gate array.
A stream encryption process of Mbps or more can be realized. The APC-MLQ method is used as the codec to secure a high quality call that is resistant to transmission errors.

In the above description, the manual encryption key unit 3-1 and the automatic encryption key unit 3-2 are the encryption processing LSI of the encryption / decryption unit 1.
Although it was separated from the
It is also possible to generate a different encryption key for each communication by using a secret function process based on the identifier (ID) of both parties and a random number. In this case, regarding the registers in CPU 4,
The number of digits may be different between the manual mode and the automatic mode for the same function, or different secret functions may be used in the manual mode and the automatic mode.

Further, the display operation unit 6 may share the input of an identifier (ID), the setting of various modes and the ten-key for dialing, and the display is performed by the LED and the LCD. Next, a series of operations of this embodiment will be described. FIG. 3 is a diagram showing an operation flowchart of the caller's confidential telephone device. As shown in the figure, when the mode is set to the automatic mode (step 1), the CPU 4 causes the random number generator (not shown) to generate a random number, and based on this random number, the automatic encryption key unit 3-2 causes the encryption key AK. read the _a (step 2). AK _a
Means the caller's encryption key. This encryption key AK _a
The encryption key is stored in a register (not shown) in the CPU 4, and is transmitted to the other party's secret telephone device 20 via the modem 8 (step 3). When the other party's confidential telephone device 20 receives this encryption key AK _a (step 4), it stores it.
In the same manner as above, the encryption key AK _b is automatically generated, and A
A decryption key is formed by K _a + AK _b , and the generated encryption key AK _b is transmitted to the caller. Caller's secret telephone device 10
Then, the encryption key AK _b is received via the modem 8, and CP
The encryption key AK _a + AK _b is formed in the register in U 4 (step 5). When the encryption key and the decryption key are set in this way, the fact is displayed on the display unit 6, the voice input is permitted from the handset (step 6), and the electric signal from the voice is encoded by the codec. (Step 7), encryption / decryption unit 1 of encryption key AK _a + AK _b
Is encrypted (step 8) by the modem 8, analogized by the modem 8 and further modulated (step 9), and the confidential call is transmitted to the other party's confidential call telephone device 20 via the line 9 (step 10). When setting the manual mode, an encryption key is negotiated in advance between the calling party and the other party.
Manual mode is selected (step 1), manually encryption key portion 3-1 encryption key and decryption key MK _a is read out (step 11), the other party also similar input as described above, the encryption key and The decryption key MK _a is set. As described above, as the encryption method, the common key encryption method in which the encryption key and the decryption key are the same is adopted.

FIG. 4 is a diagram showing an operation flowchart of the other party's confidential talking telephone device. In steps 12 to 16 of this figure, in response to steps 1 to 5 of FIG.
Set _a + AK _b . In the following, in the reverse order of the operation shown in FIG. 3, when input from the line 9 (step 17), it is demodulated by the modem (step 18) and decrypted (step 1).
9) It is decoded by the codec (step 20) and output as voice from the handset (step 21). Note the case of the manual mode in the step 12, it sets the decryption key MK _a via step 22. On the contrary, when voice is output from the other party's confidential telephone device, the decryption key is used as the encryption key, and the caller's encryption key is used as the decryption key. Therefore, in the secret eavesdropping telephone device for wiretapping, it is completely impossible to eavesdrop in the manual mode as in the conventional case when the caller or the other party is secretly talking in the automatic mode. Although the digital type has been described in the present embodiment, an analog type is also applicable. It is also applicable to data communication such as personal computer communication.

[0016]

As described above, according to the present invention,
Since the encryption key used is different between the automatic mode and the manual mode, the manual mode can completely prevent the eavesdropping of the secret story of the automatic mode.

[Brief description of drawings]

FIG. 1 is a diagram showing a principle configuration of the present invention.

FIG. 2 is a diagram showing a confidential telephone device according to an embodiment of the present invention.

FIG. 3 is a diagram showing an operation flowchart of a caller's confidential telephone device.

FIG. 4 is a diagram showing an operation flowchart of the other party's confidential telephone device.

FIG. 5 is a schematic diagram for explaining prevention of wiretapping in a conventional confidential telephone device.

[Explanation of symbols]

 1 ... Encryption / decryption unit 2 ... Encryption key setting unit 3 ... Encryption key unit 3-1 ... Manual encryption key unit 3-2 ... Automatic encryption key unit

Claims (1)

Claim: What is claimed is: 1. An encryption / decryption unit (1) for encrypting and decrypting a voice signal, and an encryption key of a caller and an encryption key of the other party are combined to automatically generate or In a secret telephone device having an encryption key setting unit (2) for manually setting an encryption key and an encryption key unit (3) including a large number of the encryption keys, the encryption key unit (3) is an encryption key. And a manual encryption key unit (3-1) for manually setting the automatic encryption key unit (3-2) for automatically generating an encryption key different from the manual encryption key unit (3-1). And a secret phone device.