JPS59107658A - Method and apparatus of private talk - Google Patents

Abstract

PURPOSE:To eliminate for a synchronizing circuit and to obtain almost infinite number of keys for the private talk by ciphering and transmitting discrete information being converted into private talk and applying private talk inversion to the said information by the information decoded at a receiving side. CONSTITUTION:An analog signal to be transmitted is inputted to a private talk converting circuit 2 where the signal is applied with private talk conversion. The private talk conversion is attained by dividing an input signal into plural bands and rearranging them, and as a signal selecting the combination of rearrangement, a signal from a discrete number generating circuit 4 inputting an output signal of a random number series generating circuit 3 is used. A part of an output of the circuit 3 is inputted to a ciphering circuit, where a ciphered output is obtained. A private talk analog signal and a ciphered discrete signal are obtained from a receiving signal at an input terminal 21 at a signal generating circuit 26, and the discrete signal is decoded at a deciphering circuit 25 and a random number series is obtained. This random number series is applied to a discrete number generating circuit 24, and its output becomes a control input to a private talk inverting circuit 22. On the other hand, the private talk analog signal is inputted to the circuit 22, where the said signal is subject to the control of an output of the circuit 24 and the original analog signal is reproduced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a confidential communication method and device for analog signals, and more particularly to a confidential communication method and device that facilitates confidential communication synchronization. Various confidential communication techniques have been developed to protect the confidentiality of communications.

In particular, there are many types of secret techniques for concealing analog signals. In order to achieve the purpose of secret speech, it is sufficient to perform some kind of conversion on the transmitted signal, but in order to increase the strength of secret speech, the conversion operation must be changed over time. In order to obtain a transmitted signal by inversely converting the confidential message on the receiving side, the inverse confidential conversion must be performed in synchronization with the conversion operation that changed over time on the transmitting side. I need to take it.

In conventional analog secret communication technology, signals for synchronization were transmitted independently of analog signals. for example,
There are separate random number generators on the transmitting and receiving sides, and a synchronization signal is sent prior to conversation to achieve synchronization.
A method is known in which a synchronization signal is always transmitted together with the transmitted analog information. Since the synchronization signal corresponds to the period of secret conversion, it is necessary to increase the period of secret conversion in order to increase the privacy strength. As a result, it takes a long time to establish synchronization, and at the same time, it requires a complicated synchronization circuit.

The object of the present invention is to provide a confidential method and device which does not have such drawbacks and allows synchronization to be established in a much shorter time, without the need to send any synchronization signals. .

According to the present invention, a first analog signal obtained by generating a random number sequence and performing secret conversion on an analog signal to be transmitted in accordance with the discrete values generated by the random number sequence;
A signal obtained by combining the random number sequence with a second discrete signal obtained by encrypting the random number sequence is transmitted, and on the receiving side, the inverse of the combination of the first and second signals performed on the transmitting side is transmitted. By performing an operation, the first analog signal and the second discrete signal are separated, and the second discrete signal is decrypted and the discrete value generated by the signal obtained is transmitted. The above purpose can be achieved by performing inverse transformation of the secret transformation performed on the side.

A detailed explanation will be given below using the drawings. FIG. 1 is a block diagram of an embodiment of the secret message transmitting device and FIG. 2 is a receiving device according to the present invention. An analog signal to be transmitted is input from an input terminal 1 and input to a confidential conversion circuit 2, where it is converted for confidential communication. Specifically, the secret conversion may be any type of conversion; for example, a band division/exchange method may be used in which the input signal is divided into a plurality of bands and exchanged. At this time, many combinations can be considered for the replacement method. As the signal (5) for selecting this combination, use the discrete number generation circuit 4 which receives the output signal of the random number sequence generation circuit 3 as input. This circuit, for example,
This can be achieved as shown in the figure. The random number sequence is input from the input terminal 31, and is input to each stage 32, 33 of the 11th order shift register.
, 34. Now, if we consider a binary signal as a random number series, this circuit uses a three-stage shift register, so a total of eight combinations can be obtained.

In the figure, the conversion circuit 35 generates a control signal for the secret conversion circuit at an output terminal 36 in accordance with the contents of the shift register, and uses this as a control signal input to the secret conversion circuit 2.

A part of the output signal of the random number sequence generation circuit 3 is sent to the encryption circuit 5.
is input and the encrypted output is obtained.

A possible method for implementing the encryption circuit is, for example, a self-synchronized encryption method as shown in FIG. 4(a). Random number series is input terminal 41
In the case of the NgLM number, an addition circuit 42 modulo N performs addition with an output signal of a function generation circuit 46, which will be described separately, and output from an output terminal 47. At the same time, part of the output signal is transferred to the shift register 43.
, 44, and 45 in sequence.

(6) The function generating circuit 46 generates a signal uniquely determined by the contents of each shift register.

The detailed operation is well known in cryptographic technology, etc., so it will not be explained here. Here, the encryption/decryption circuit 2
5 (FIG. 2) will be explained using fR4 diagram (b). As explained later, the sequence of encryption circuits is
On the receiving side, it is received at the input terminal 48 of the encryption/decryption circuit. Part of the received signal sequence is transferred to shift registers 43 and 4.
4 and 45, and is added to the output of the function generating circuit 46 described earlier by the adder circuit 42 to obtain the same signal sequence as that input to the encryption circuit. This operation is the easiest to implement in a circuit, which is binary (0, 1
) is easy to understand by considering the signal sequence. Now, if signal delays are ignored, the same values are stored in the shift registers 43, 44, and 45ζ of the encryption circuit and the encryption/decryption circuit, respectively. Therefore, each function generating circuit 46
The output of will also produce the same value. A 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,
Even if 0 is added twice to the input signal, or 1 is added twice to the input signal, the value does not change. 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 trying to eavesdrop on the output signal of the encryption circuit during the communication, if he does not know the operation of the encryption/decryption circuit, especially the operation of the function generator circuit A6, he will not be able to retrieve the original signal. It's impossible to know. The operations of the encryption circuit and decryption circuit described above are no different from conventional encryption and decryption techniques, and the conventional techniques can be used to their full potential.

Return to Figure 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 a synthesis circuit 6, and then transmitted from an output terminal 7. Here, it is conceivable that the synthesis circuit 6 separates and synthesizes on the frequency axis, as shown in FIG. 5, for example. The same figure (a
) is the electric cassette vector of the confidential analog signal, and in the same figure (bl is the spectrum of the signal modulated with the encrypted discrete signal. Here, the modulation was performed to separate the frequency bands. However, it is not necessarily necessary, and simple frequency conversion may be used.Other methods of synthesis such as separation on the time axis can be considered, and in any case, any method that allows the two signals to be separated again on the receiving side is possible. Any method is fine.

FIG. 2 is a block diagram showing an embodiment of the confidential message receiving device according to the present invention. The signal received at the input terminal 21 is processed by the signal separation circuit 26 into a confidential analog signal combined on the transmitting side and an encrypted discrete signal. Specifically, for example, when the signals are separated and synthesized on the frequency axis as shown in FIG. 5, separation can be easily performed using a low-pass filter and a high-pass filter. If modulation is performed using a discrete signal, demodulation is also performed.

The encrypted discrete signal is decoded by the decryption circuit 25 to obtain the transmitted random number sequence. This random number sequence is applied to the discrete number generation circuit 24, and its output becomes the control input of the confidential speech inverse conversion circuit 22.

(9) Here, the discrete numerical value generating circuit operates in the same manner as shown in FIG.
The contents of 4 are the same as the contents of the register when secret conversion was performed on the transmitting side. Therefore, for the same register contents, the contents of the discrete numerical value generation circuits on the transmitting side and the receiving side may be determined to be such numerical values that the secret conversion returns to the original value by inverse conversion. The transmitted analog signal is obtained at the output terminal 27 as the output of the private speech inverse conversion circuit 22.

As described above, in the present invention, the discrete information obtained when secret conversion is performed is encrypted and transmitted, and the receiving side performs secret conversion inversely using the information obtained by decoding the code. Therefore, there is no need to transmit any synchronization information. Therefore, there is an effect that the time required to establish synchronization or the synchronization circuit as in the prior art is not required. Furthermore, since there is no need for synchronization, there is no limit to the random number sequences that can be used; for example, random number sequences generated from physical noise can be used, which has the effect of making it possible to obtain an almost infinite number of private keys.

(10) In addition to the method described here, a synchronous encryption method is also known as a method for encrypting a discrete signal, and this can be used in the present invention as well. At this time, however, it is necessary to synchronize for encryption and decryption. However, even in this case, no restrictions are placed on the random number sequence for secret conversion, and the number of secret keys does not change. Since the input signal to the encryption circuit is a random number sequence, the cycle for encryption can be short, so the synchronization time is shorter than in the conventional synchronous secret communication method.

The random number sequence generation circuit used in the present invention does not need to be limited in any way, and may use, for example, a data signal to be transmitted or a signal obtained by encrypting the data signal.

At this time, since the transmitted data signal is obtained as the output of the decryptor on the receiving side, there is also the effect that data transmission can be performed while having a conversation. In the traditional secret method,
For example, since a synchronization signal is being sent to the part shown in Figure 5(b), the band for this part is wasted, but in this case, this band can also be used effectively for data transmission. It turns out.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the confidential message receiving device of the present invention, FIG. 2 is a block diagram showing an embodiment of the confidential message receiving device of the present invention, and FIG. 3 is an example of the circuit used in the present invention. FIG. 5 is a spectral diagram showing the operation of an example of the signal synthesis circuit used in the present invention. In these figures, 1, 31, 41 are signal input terminals,
7, 27, 36, 47, 49 are signal output terminals,
2 is a secret conversion circuit, 3 is a random number generation circuit, 4.24 is a discrete number generation circuit, 5 is an encryption circuit, 6 is a synthesis circuit, 26
25 is a separation circuit, 25 is an encryption/decryption circuit, 22 is a confidential inverse conversion circuit, 32, 33, 34, 43, old, 45 is a register, 35 is a conversion circuit, 42 is an addition circuit, 46 is a leap number generation circuit No. 1 Figure 2 C1 Figure 3 1 (Figure 4) 0-

Claims (5)

[Claims] (1) Generating a random number sequence, and encrypting the first analog signal obtained by performing secret conversion on the analog signal to be transmitted in accordance with the discrete values generated by the random number sequence, and the random number sequence. The signal obtained by combining the obtained second discrete signal is transmitted, and the receiving side performs the inverse operation of combining the first and second signals performed on the transmitting side. The first analog signal and the second discrete signal are separated, and the second discrete signal is decrypted to generate a discrete value. A confidential communication method characterized by performing inverse conversion and obtaining a transmitted analog signal. (2) means for generating a random number sequence; means for performing secret conversion into an analog signal to be transmitted in accordance with the discrete values generated by the random number sequence; and an encoder for encrypting the random number sequence (1). and a discrete signal obtained from the encoder and an analog signal obtained from the means for performing the secret speech conversion, and transmits a signal obtained by combining the discrete signal and the analog signal obtained from the means for performing secret speech conversion. (3) The confidential message transmission device according to claim (2), which uses self-synchronized encryption as a method of encrypting the random number sequence. (4) A confidential message transmitting device in which the discrete values generated for performing confidential conversion are continuous without dividing the random number sequence into blocks. (5) Generating a random number sequence, and encrypting the first analog signal obtained by encrypting the analog signal to be transmitted and encrypting the random number sequence in accordance with the discrete values generated by the random number sequence. In a confidential reception device that receives a signal transmitted by combining a second discrete signal, by performing a reverse operation of combining the first analog signal and the second discrete signal performed on the transmitting side. means for separating a first analog signal and a second discrete signal; a decoder for decoding the second discrete signal; and a signal obtained from the decoder to generate a discrete signal. What is claimed is: 1. A confidential communication receiving device, comprising means for generating a confidential communication and correspondingly performing a reverse operation of the confidential conversion performed on the transmitting side, and using a signal obtained from this as a received analog signal.