JPH0756975B2 - Confidential receiver - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a secret-speech receiver for analog signals, and more particularly to a secret-speech receiver that facilitates secret-secret synchronization.

[0002]

2. Description of the Related Art Various secret communication technologies have been developed so far in order to protect communication secrets. In particular, there are many types of secret talking technology for concealing analog signals. In order to achieve the purpose of the secret story, some kind of conversion may be performed on the transmitted signal, but in order to increase the secret story strength, the conversion operation must be changed with time. In order to obtain the transmission signal by performing the inverse transformation of the secret story on the receiving side, it is necessary to perform the inverse confidential transformation on the transmitting side in synchronization with the conversion operation changed with time on the transmitting side. Need to take.

In the conventional analog secret technology, a signal for synchronizing is transmitted independently of the analog signal. For example, there are methods to have a random number generator on the transmitting side and a receiving side, and to send a synchronization signal to synchronize before the conversation, or to always send a synchronization signal along with the transmitted analog information. Has been.

[0004]

However, in the above-mentioned technique, since the synchronizing signal corresponds to the cycle of secret-speech conversion, it is necessary to lengthen the cycle of secret-speech conversion in order to increase the secret-speech intensity. As a result, it takes a long time to establish the synchronization, and at the same time, there is a drawback that a complicated synchronization reply is required.

The object of the present invention is to eliminate these drawbacks,
It is an object of the present invention to provide a secret-speech receiver capable of establishing synchronization in a much shorter time even if there is no need to send a synchronization signal or if there is.

[0006]

According to the present invention, a random number sequence is generated, and an analog signal to be transmitted is subjected to a secret-talk conversion in accordance with a discrete value generated by the random number sequence. In a confidential communication receiver that receives a signal transmitted by synthesizing an analog signal and a second discrete signal obtained by encrypting the random number sequence using a self-synchronization method, Means for separating the first analog signal and the second discrete signal by performing an inverse operation of synthesizing the analog signal and the second discrete signal; and decryption of the second discrete signal. It has a decoder for performing and a means for generating a discrete signal by the signal obtained from the decoder and correspondingly performing a reverse operation of the secret-speech conversion performed on the transmitting side, and receiving the signal obtained from this. Characterized by analog signals Confidential reception device is obtained.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A detailed description will be given below with reference to the drawings. Figure 1
FIG. 2 is a block diagram of an embodiment of a confidential transmission device according to the present invention, and FIG. 2 is an embodiment of the confidential reception device according to the present invention. The analog signal to be transmitted is input from the input terminal 1 and then input to the confidential talk conversion circuit 2, where conversion for confidential talk is performed. The secret story conversion may be any conversion specifically, for example,
A band-division switching method in which an input signal is divided into a plurality of bands and replaced can be considered. At this time, many combinations can be considered for the replacement. As a signal for selecting this combination, the discrete numerical value generation circuit 4 that receives the output signal of the random number sequence generation circuit 3 is used. This circuit can be realized, for example, as shown in FIG. The random number sequence is input from the input terminal 31, and is sequentially input to each stage 32, 3 of the shift register.
3, 34. Now, considering a binary signal as a random number sequence, since this circuit uses a three-stage shift register, a total of eight combinations are possible. In the figure, the conversion circuit 35 generates a control signal for the confidential channel conversion circuit at the output terminal 36 according to the contents of the shift register, and inputs this to the control signal input to the confidential channel conversion circuit 2.

A part of the output signal of the random number sequence generation circuit 3 is
Input to the encryption circuit 5 and an encrypted output is obtained.
As an implementation method of the encryption circuit, for example, a self-synchronization encryption method as shown in FIG. 4A can be considered. The random number sequence is input from the input terminal 41, and in the case of an N-valued signal, the addition circuit 42 modulo N performs addition with the output signal of the function generating circuit 46, which will be described separately, and outputs from the output terminal 47. It At the same time, some of the output signals are shifted to the shift registers 43, 4
4 and 45 are sequentially input. The function generating circuit 46 generates a signal that is uniquely determined by the contents of each shift register. The detailed operation is well known in cryptographic technology and the like, and will not be described here. Here, the operation of the encryption / decryption circuit 25 (FIG. 2) will be described with reference to FIG. As will be described later, the output sequence of the encryption circuit is received by the input terminal 48 of the encryption / decryption circuit in the receiving device of the present invention. A part of the received signal sequence is sequentially input to the shift registers 43, 44, 45, and
The output of the function generating circuit 46 described above is added to the output of the adding circuit 42, and the same signal sequence as that input to the encryption circuit is obtained. This operation is easy to understand when considering a binary (0, 1) signal sequence that is the easiest to implement in the circuit.
Now, ignoring the signal delay, the same values are stored in the shift registers 43, 44, 45 of the encryption circuit and the encryption / decryption circuit, respectively. Therefore, the output of each function generating circuit 46 also generates the same value. The value of 0 or 1 is added twice in succession to the signal input to the input terminal 41 of the encryption circuit. As is well known in addition modulo 2, the value does not change even if 0 is added twice or 1 is added twice to the input signal. Therefore, the same signal sequence as the input signal of the encryption circuit is obtained at the output terminal 49 of the decryption circuit. Even if the person who wants to eavesdrop can know the output signal of the encryption circuit during the communication, if he / she does not know the operation of the encryption / decryption circuit, especially the operation of the function generation circuit 46, he / she will know the original signal. It is not possible. The operations of the encryption circuit and the decryption circuit described above are not different from those of the conventional encryption and decryption techniques, and the conventional techniques can be used as they are.

Returning to FIG. 1 again. The secret-speech signal output from the secret-speech conversion circuit 2 is combined with the output signal from the encryption circuit 5 by the combining circuit 6, and then transmitted from the output terminal 7. Here, it is conceivable that the synthesizing circuit 6 separates and synthesizes on the frequency axis as shown in FIG. 5, for example.
The figure (a) is the power spectrum of a secret analog signal, and the figure (b) is the spectrum of the signal modulated by the encrypted discrete signal. Here, the modulation is performed in order to separate the frequency bands, and is not always necessary and may be mere frequency conversion. As the combining method, a method of separating them on the time axis may be considered, and in any case, any method may be used as long as the two signals can be separated again on the receiving side.

FIG. 2 is a block diagram showing an embodiment of a confidential talk receiving apparatus according to the present invention. The signal received by the input terminal 21 is obtained by the signal separation circuit 26 as a discrete signal encrypted with the confidential analog signal synthesized on the transmission side. Specifically, as shown in FIG. 5, when they are separated and combined on the frequency axis, they can be separated by a low pass filter and a high pass filter. When the modulation is performed by the discrete signal, the demodulation is also performed.

The encrypted discrete signal is the encryption / decryption circuit 2
The random number sequence decoded and transmitted by 5 is obtained. This random number sequence is applied to the discrete numerical value generation circuit 24, and the output thereof becomes the control input of the confidential story inverse transformation circuit 22. here,
The discrete numerical value generating circuit operates, for example, in the same manner as that shown in FIG. 3, and the contents of the registers 32, 33, and 34 are the same as the contents of the register when the confidential conversion is performed on the transmitting side. Therefore, it suffices to set the contents of the transmitting side and receiving side discrete numerical value generation circuits to the same register content so that the confidential conversion returns to the original value by the inverse conversion. The transmitted analog signal is obtained at the output terminal 27 as the output of the confidential reversal conversion circuit 22.

[0012]

As described above, according to the present invention, a signal transmitted from the secret-speech transmitting apparatus according to the present invention by encrypting the discrete information when the secret-speech conversion is performed is transmitted by the receiving apparatus of the present invention. The secret story inverse conversion is performed by the information obtained by decrypting the code, and it is not necessary to transmit any synchronization information. Therefore, there is an effect that the time required for establishing synchronization or the synchronization circuit becomes unnecessary unlike the prior art. Further, since there is no need to synchronize, there is no limit to the random number sequence that can be used, and for example, a random number sequence generated from physical noise can be used.

As a method for encrypting a discrete signal, a synchronous encryption method other than the one described here is also known.
It can also be used in the confidential transmission device relating to the present invention. In this case, however, the confidential communication receiver of the present invention needs to be synchronized for encryption / decryption. However, also in this case, no limitation is placed on the random number sequence for the secret-key conversion, and the number of secret-keys does not change. Since the input signal of the encryption circuit is a random number sequence, the cycle for encryption can be short, so compared to the conventional synchronous confidential communication method,
The synchronization time will be shorter.

The random number sequence generation circuit used in the confidential transmission apparatus according to the present invention does not need to be limited at all, and for example, a data signal to be transmitted or an encrypted signal thereof may be used. At this time, since the transmitted data signal can be obtained at the output of the encryption / decryption device of the confidential communication receiver of the present invention, there is also an effect that data transmission can be performed while talking. In the conventional confidential communication method, for example, since the synchronization signal is sent to the part of FIG. 5B, the band of this part is lost, but in this case, this band is also effective for data transmission. It will be used for.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a confidential transmission device according to the present invention.

FIG. 2 is a block diagram showing an embodiment of a confidential communication receiver of the present invention.

FIG. 3 is a block diagram showing an embodiment of a discrete numerical value generation circuit used in the present invention.

FIG. 4A is a block diagram showing an embodiment of an encryption circuit used in the confidential transmission apparatus according to the present invention, and FIG. 4B is an embodiment of an encryption / decryption circuit used in the confidential reception apparatus of the present invention.

FIG. 5 is a spectrum diagram showing an operation of an example of a signal synthesizing circuit used in the confidential transmission apparatus according to the present invention.

[Explanation of symbols]

 1, 31, 41 Signal input terminal 7, 27, 36, 47, 49 Signal output terminal 2 Confidential conversion circuit 3 Random number generation circuit 4, 24 Discrete numerical value generation circuit 5 Encryption circuit 6 Synthesis circuit 26 Separation circuit 25 Decryption Circuit 22 Confidential inverse conversion circuit 32, 33, 34, 43, 44, 45 Register 35 Conversion circuit 42 Adder circuit 46 Function generation circuit

Claims (1)

[Claims] 1. A random number sequence is generated, and a first analog signal obtained by subjecting an analog signal to be transmitted to secret-talk conversion to correspond to a discrete value generated by the random number sequence and the random number sequence are self-generated. The second encrypted by using the synchronous method
In a secret-speech receiver that receives the transmitted signal by combining the discrete signal of the first discrete signal and the second discrete signal by performing a reverse operation of the synthesis of the first analog signal and the second discrete signal performed on the transmitting side. Means for separating the analog signal from the second discrete signal, a decoder for cryptographically decrypting the second discrete signal, and a discrete signal generated by the signal obtained from the decoder, And a means for performing an inverse operation of the secret-speech conversion performed on the transmitting side, and a signal obtained from the means is used as a reception analog signal.