JPH07336329A - Signal ciphering system - Google Patents

Abstract

PURPOSE:To perform signal ciphering undecipherable for a third person without damaging original signals by directly ciphering input signals. CONSTITUTION:A cipher code 1100 is directly mixed into the input signal 1000 and a secret signal 1200 is obtained. To the input signal 1000, the secret signal 1200 is maintained as it is when the cipher code 1100 is '1' and is inverted when the cipher code 1100 is '-1.' That is, the secret signal 1200 is inverted in sections B1400 and D1600 and as a result, for the ciphered signals, a frequency band is widened and a noise proofing property is improved. The cipher code 1100 is calculated with the code of a certain series (code value: 1, -1) as the cipher code and infinite combinations are present for the code depending on a calculation method. Thus, since the pattern of a code string used for the cipher code 1100 can be inifinitely generated, the signals undecipherable for the third person are generated. On a reception side, when the same cipher code is mixed in again, the original signals are deciphered and the improved signals are obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal concealment system which is applicable to both the wireless and wired transmission lines for the purpose of concealing input signals.

[0002]

2. Description of the Related Art Conventionally, as a method for concealing a signal,
There are a method of randomly rearranging a spectrum obtained by applying FFT (Fast Fourier Transform) to an analog signal, a method of converting a digital signal for each code, and then encrypting it.

Each of these methods is a method aimed at "to be incorporated in a device for the purpose of concealment" and requires dedicated hardware or complicated software. Therefore, in order to apply the above-mentioned dedicated hardware and software to existing communication devices (including terminals) over a long development period, hardware /
Needed a major modification of the software.

[0004]

SUMMARY OF THE INVENTION According to the present invention, a signal concealment method in which an input signal is concealed with an infinite cryptographic code, is difficult to decipher, and causes little signal deterioration is proposed for a new or existing device. It is to provide a method that can be added without significantly changing the configuration.

[0005]

As a method for applying frequency spreading, there is a spread spectrum method, and in general, direct spread (DS: Direct Sequence) modulation,
Frequency hopping (FH: Frequency Hop)
ping) modulation and the like. For details, see "Latest spread spectrum communication method" (Jatec Publishing Co., Ltd.).

In this signal concealment method, the input analog signal is directly multiplied by the encryption code (code value: 1 or -1) to perform encryption, and the receiving side re-multiplies the same encryption code to obtain the original signal. Signal is decoded and a good signal is obtained at the receiving side.

In addition, since the former encryption code pattern can be generated infinitely, a third party can transmit and receive a signal that cannot be demodulated and decoded.

[0008]

With this signal concealment method, the signal input device outputs the input signal as an analog or digital signal.

The encryption code is a code of a certain series (code value:
1, -1) is calculated as an encryption code. There are infinite combinations of this code depending on the calculation method.

By multiplying the encryption code, the output signal is frequency spread and also has noise resistance.

The received signal can also be decrypted by multiplying it with the encryption code.

[0012]

EXAMPLE One example of the present invention will be described below.

FIG. 1 is a simulation of the encryption method in this signal concealment system.

In this signal concealment system, the input signal 1000 is directly multiplied by the encryption code 1100 to obtain the concealment signal 1200.

For input signal 1000, encryption code 11
While 00 is "1", the secret signal remains unchanged, while secret code 1200 is inverted while encryption code 1100 is "-1".

Taking FIG. 1 as an example, in the sections B1400 and D1600, the secret signal 1200 is inverted, and as a result, the encrypted signal has the effects of widening the frequency band and improving noise resistance.

The code string pattern used for the encryption code 1100 can be generated infinitely. Therefore, it is possible to generate a signal that cannot be decrypted by a third party.

FIG. 2 is a signal waveform diagram relating to the present embodiment. (A) The input signal is a composite wave of 1000 hz and 2000 hz, and (b) the secret signal is a signal obtained by multiplying the (a) input signal by an encryption code and performing encryption.
In the figure, the horizontal axis represents time and the vertical axis represents amplitude.

3A and 3B are frequency distribution diagrams of the present embodiment. (1) the frequency distribution of the input signal and (2) the frequency distribution of the secret signal are respectively the input signal of FIG.
(B) Corresponding to a secret signal. FIG. 3 shows the FFT (F) for the input signal (a) and the secret signal (b) of FIG.
ast Fourier Transform: fast Fourier transform).

The FFT signal processing technique is described in detail in "Introduction to Signal Processing" (Ohm Company).

(1) In the frequency distribution of the input signal, 100
Spectra appear at 0hz and 2000hz, and
It can be seen that the input signal is a composite wave of 1000 hz + 2000 hz. On the other hand, in (2) the frequency distribution of the secret signal,
It can be seen that the frequency band of the encrypted signal is expanded.

The frequency distribution of the decoded signal (I) in FIG. 4, (I
I) The decrypted signal is a frequency distribution chart of the signal obtained by demodulating and decrypting the secret signal shown in FIG. 2B by the encryption code, and a waveform chart of the signal. It can be seen that the frequency distribution is restored to the original signal of 1000hz + 2000hz.

If the input signal is an analog signal, the present invention can be concealed regardless of the type of data, voice, etc., and therefore can be applied to any of various communication devices, communication terminals, and communication systems.

[0024]

Industrial Applicability According to the present invention, a signal is prevented from deteriorating by applying a code and encryption while an analog signal is an analog signal, and the signal is protected against noise and is difficult to decipher. An existing communication device or communication system can be newly created or added.

[Brief description of drawings]

FIG. 1 is a diagram simulating an encryption method according to the present invention.

FIG. 2 is a signal waveform diagram according to the first embodiment.

FIG. 3 is a frequency distribution diagram regarding the first embodiment.

FIG. 4 is a frequency distribution diagram and a signal waveform diagram of a demodulated and decoded signal.

[Explanation of symbols]

 1000 ... Input signal, 1100 ... Cryptographic code, 1200 ... Secret signal, 1300 ... Section A, 1400 ... Section B, 1500 ... Section C, 1600 ... Section D, 1700 ... Section E.

Claims (3)

[Claims] 1. A signal concealment system characterized in that in a communication system in which a transmission path is wired / wireless, frequency spreading is directly performed on an input signal (analog signal). 2. A signal concealment system characterized by performing demodulation and decoding in a communication system whose transmission path is wired / wireless. 3. A transmission / reception device, comprising one or two or more of the signal concealment methods according to claim 1 and claim 2, respectively.