JPS5862948A - Signal encryption processing system - Google Patents

Abstract

PURPOSE:To improve the performance of encryption for the content of communication, by making the frequency for encryption secret and changing the content, through the addition of a plurality of outputs of a sinusoidal wave generator switched at a switching circuit to an output of an information signal generator. CONSTITUTION:Sinusoidal waves of n-set different frequencies are generated from a sinusoidal wave generator 2 and applied to a switching circuit 6 and the sinusoidal waves are switched with the control of a control circui 10 and applied to an adder 3. The information signal generated at an information signal generator 1 is applied to the adder 31 and one sinusoidal wave selected at the adder 3 is summed with the information signal and transmitted via a transmission line interface device 4. The encrypted signal from the transmission line is applied to a band blocking filter 8 having n-set of frequency characteristics via a transmission line interface device 7, a switching circuit 11 is controlled with the output of a control circuit 12 to select one of reception signals from an output of a filter 8 and the decoded information signal is applied to an information signal processor 19, allowing to improve the confidentiality of the content of communication.

Description

Detailed Description of the Invention The present invention relates to a signal encryption processing method, particularly in a signal transmission system such as a pay television system, in which a signal is encrypted and transmitted from a signal transmitting station, and the encrypted signal is received at a receiving station. , a highly confidential transmission and reception system to be decoded.
The purpose of the present invention is to provide a signal encryption and decryption processing method suitable for configuring a signal encryption method.

In general, when transmitting information signals from a transmitting station to a specific receiving station or receiving stations by wireless or wire, if it is necessary to exclude receiving stations other than the receiving stations listed above or eavesdroppers, the transmission A station encrypts and transmits a signal, and only the specific receiving station has means for decoding the encrypted signal, and the signal transmission system must be configured to decode the encrypted signal.

Conventionally, one method that meets this requirement is to superimpose a sine wave on the signal to be transmitted, encrypt the signal, and then remove the sine wave using a band rejection filter at the receiving station to obtain the signal. There is.

FIG. 1 shows a conventional invincible pay television system in which television programs employing such a system are wirelessly provided only to subscribers for a fee.

In FIG. 1, a in the above system is a block diagram of the transmitting equipment of the transmitting station, and b is a block diagram of the receiving station.

In FIG. 1a, l is a television signal generator, 2 is a sine wave oscillation, 13 is an adder, 4 is a power amplifier,
5 is a transmitting antenna. A normal television audio signal is outputted from the video/audio signal generator 1 in a negative modulated state and applied to one input terminal of the adder 3. For shaky vibration-2, when the video carrier frequency of the television video and audio signal generator 1 is fv and the oscillation frequency of the oscillator 2 is fa, K is set so that Cfa-fq) is within the band of the video signal. A sine wave signal with a preset constant frequency fa is output and supplied to the other input terminal of the adder 3. :'::' Adder 3 adds the two signals and supplies it to power amplifier 4'K. The electric amplifier 4 amplifies the power of the input signal, supplies it to the transmitting antenna 5, and transmits it as a radio wave.

Level L and frequency f of the signal processed as described above
The frequency spectrum showing the relationship between Understanding is impossible.

In Fig. 1 b & C, 6 is a receiving antenna, 7 is an amplifier,
8 is a band rejection filter, and 19 is a normal television receiver. The encrypted television signal received by the receiving antenna 6 is supplied as it is in the radio frequency band to the amplifier 7, where it is amplified and input to the band rejection filter 8. Since the closing frequency of the band-elimination filter 8 is set to the oscillation frequency fs of the oscillator 2, it can be seen that the band-elimination filter 8 removes the encrypted signal. The frequency spectrum of the televisionsian signal outputted from the band-elimination filter 8 is as shown in FIG. 2 bVc, and does not have a frequency 'fs component, but the image deterioration caused by this cannot be ignored.

If such a signal is supplied to an ordinary television receiver 19, an ordinary television image can be obtained.

As mentioned above, it is possible to realize an encrypted signal transmission/reception system using the conventional method, but the band rejection filter used for decoding the encrypted signal can be easily constructed using commercially available electrical components. Therefore, since the signal can be easily intercepted, the transferability of the transmitted information is low.

The present invention has been made in order to improve the drawbacks of the prior art, and includes a signal control means on the transmitting side, for example, to convert one sine wave signal from a plurality of sine wave signals of different frequencies. means for selecting a signal, or
A means for changing the frequency of the sine wave signal is provided, and the sine wave signal obtained from this means is superimposed on the information signal to be transmitted and encrypted. For example, means for selecting a band-elimination filter corresponding to the frequency of the selected sine wave signal, or means for changing the closing frequency of the band-elimination filter so as to correspond to the frequency of the sine wave signal, and by this means. The present invention is characterized in that the confidentiality of information is improved each time the information i is decoded from the received signal using a controlled band rejection filter.

The present invention will be described below with reference to the embodiments shown in the drawings. FIGS. 3a and 3b show the basic configurations of the transmitting side and receiving side, respectively. In Fig. 3a, 1 indicates information signal generation.

2 (1) to 2 (rL) are sine wave oscillators (rL is a positive integer) having nine different frequencies; 3 is an adder;
4 is a transmission line interface device, 9 is a switching circuit, 10
is a control circuit of the switching circuit 9. The information signal output from the information signal generation base l is input to one input terminal of the adder 3. Moreover, the switching circuit 9 is controlled by the control circuit 10 to
j is controlled so that only one of the nine (ll-2 (rL)) of the sine wave oscillator 2 is selected and its sine wave signal output is supplied to the other input terminal of the adder 3. The adder 3 adds the two input signals and outputs it to the transmission line interface device 4. The transmission line interface device outputs the input signal to the transmission line.

On the other hand, in FIG. 3, 7 is a transmission line interface device, 8 (X) to 8 (rL) are band rejection filters having one different rejection band, 11 is a switching circuit, 12 is a switching circuit 110 control circuit, and 19 is an information signal processing device. The encrypted information signal supplied from the transmission path is input to the transmission path interface device 7, and the output signal of the transmission path interface device 7 is passed through the (1) of the band rejection filter 8.
) to 8 (rLl) are supplied to all input terminals +K of band rejection filters 8 (11 to 8 (FL)), respectively. Since the frequencies fal to fonK are set, the switching circuit 11 selects the output frequency of the band rejection filter having the same prevention frequency as the frequency fam (- is a positive integer less than or equal to 1) used for encrypting the information signal at the transmitting station. If you choose,
It can be seen that the decoded information signal is obtained at the output terminal of the switching circuit 11. 1.99 is input. :1゜switching circuit 1] is controlled by a control circuit 12, and the control circuit 12 receives information from the transmitting side regarding the frequency of the positive i-wave signal used for encryption of each information transmission, whether it is wired transmission or wireless transmission. or other communication means, and the control circuit 12 selects a band-stopping filter that has the same stopping frequency as the frequency of the sine wave used by the transmitting side for encryption, according to the information. Then, the switch II is controlled.

In the information transmission system configured as described above, when the "unintended" receiving station on the provisional Ki receiving side receives the initiated encrypted signal and tries to use the gate code, the receiving station 9, the receiving station, If the received signal is within the previous mLE Confucian wave frequency s~fan,
Since it is not possible to know in advance which frequency of the sine wave is being used to encrypt the received signal, it is necessary to pass the received signal through all the band-stop filters whose stop bands are the above-mentioned station wave number f'ss' - fsn. . Moreover, the resulting output signal is also highly contaminated with information signals, making it difficult or impossible to decipher the information. On the other hand, the decoded information signal & text obtained at a regular receiving station always passes through only one band-stop filter.
Since the decryption process is not carried out and the information transmission tower is not corrupted, an example in which the above-described encrypted signal processing method of the present invention is applied to the above-mentioned wireless pay television system is shown in Fig. 4a. , b.

In FIG. 4a, on the Mizuko transmitting side □, the same reference numerals as in FIG. 3a indicate the same or similar items. As mentioned above, the transmitting side device operates to switch the sine wave signal applied to the television signal, but the timing of the switching is done in units of fields of the television signal or in units of horizontal lines. do. Moreover, the control information of the changeover switch 9 is transmitted from the control circuit 10 to the television signal generated □
The signal IK is supplied to the signal generator IK and superimposed on the video signal in the form of a binary signal or the like during the vertical blanking period. In addition, the sine wave oscillator 2
(1) to (rLl oscillation frequency fo '1 "" f
sn must also be at a sufficiently high frequency as the horizontal synchronization frequency so as not to corrupt the television broadcast synchronization signal when the signal is demodulated.

In FIG. 4, the same reference numerals as those in FIG. The encrypted television signal received by the receiving antenna 6 is amplified by the amplifier 7, band-stopped, filters 8 (1) to 8 (r+J) and the detector 13 The output of the detector 13 is input to a low-pass filter 14.The low-pass filter passes a frequency around the horizontal synchronization frequency, and the frequency fsl- of the sine wave is passed through the low-pass filter.
Frequencies such as fsn are set to be blocked, so that the control signal of the changeover switch 9 and the corrupted video signal appear at the output terminal of the low-pass filter 14. The information reader 15 reads the control signal for the changeover switch 9 from the signal and supplies it to the control circuit 12.
2 controls the changeover switch l] according to the signal.

FIG. 5a shows the embodiment described above. FIG. 5 shows the frequency spectrum of the encrypted television signal transmitted from the transmitting side, and FIG. 5 shows the frequency spectrum of the television signal decoded at the receiving station in this embodiment.

In the above embodiment, the receiving station performs signal processing in the radio frequency band, but the decoding process can be performed in the intermediate frequency band after converting the received signal to an intermediate frequency. It is also possible to perform decoding processing in the baseband after detecting the received signal.

6a and 6b show a modification of the configuration shown in FIGS. 3a and 3b. The sine wave oscillator 2' on the transmitting side has a variable frequency, and its frequency is controlled by the control pressure of the control circuit 10'. It can change.

Further, the band rejection filter 8 on the receiving side has a variable rejection band, and its rejection frequency can be changed by the control @ic of the control circuit 11'.

On the transmitting side shown in FIG. 6aK, the control circuit 10' controls the oscillation frequency fa of the sine wave oscillator 2', which is added to the information signal from the information signal generator l in the adder 3 and encrypted. The encrypted signal is output to the transmission line by the transmission line interface device 4.

The encrypted information signal transmitted by the above-mentioned 5KL is received by the receiving station shown in FIG. is input. The rejection frequency of the band rejection filter 8 is controlled by a control circuit 11'IC, and the rejection frequency of the band rejection filter 8 is controlled by the control circuit 11' so that the rejection frequency is the same as the oscillation frequency fa of the sine wave oscillator 2 on the transmitting side. ', so that the output signal of the band-stop filter 8' becomes a decoded information signal. The transmitted information signal is input to the information signal processing device 9.

The control circuit 11' is provided with information regarding one frequency f, K of the sine wave signal used for encrypting the information signal from the transmitting station by wire transmission, wireless transmission, or other communication means.

In FIG. 7 &, a T/C company delay circuit 12 is provided between the variable frequency sine wave oscillator 2' and its control port j810. Further, the television video and audio signal generator 1 is controlled by a control circuit 10.

In FIG. 7, the rejection frequency of the band rejection filter 81 is controlled by the control circuit 11'.

゛ On the transmitting side of FIG. 7, the control circuit 10 supplies a control signal of oscillation frequency 9 of the variable frequency sine wave oscillator 2' to the circuit 12', and also supplies the same control signal to the Tecivision video and audio signal generator. Supply lI/c. The television video and audio signal generator 1 FM modulates the audio subcarrier (frequency fso) using the control signal, and #FM modulates it! 11g! An adder 3 modulates the audio carrier wave with the signal and the normal audio signal, and outputs it as a television audio signal together with the television video signal.
is supplied to one input terminal of the

The delay circuit 12 delays the phase of the control signal inputted from the control circuit IO and supplies it to the variable S-wave number sine wave oscillator 2', but the amount of delay is related to the operation of the receiving station and will be described later. Variable frequency sine wave oscillator 2'+1. :The oscillation frequency k is changed according to the voltage of the delayed suppression signal supplied from the il extension circuit 12, and the oscillation output is supplied to the other input terminal of the adder 3. The adder 3 adds the two input signals and supplies the result to the power amplifier 4 , and the power amplifier 4 increases the power of the input signal and transmits it from the transmitting antenna 5 . The frequency spectrum of the encrypted television video/audio signal obtained by the operation of the apparatus as described above is shown in FIG. 8a.

The encrypted television video signal is received by the receiving antenna 6 of the receiving station, amplified by the amplifier 7, and input to the band rejection filter 8' and the television audio signal detector 13. Television audio signal detector 1
3 electrically detects only the television audio signal from the input signal 1 and supplies it to the band pass filter 14 . Bandpass filter 14 detects only the subcarrier component from the television audio signal and outputs it to detector 14 . The detector 15 performs FM detection on the input signal and sends it to the transmitting side control circuit 10'.
Obtain the control signal output by

When the control signal is applied to the control circuit 11', the control circuit 1]
adjusts the control signal to an appropriate amplitude and inputs it to the control terminal of the band rejection filter 8'. Band-stop filter B'
changes the rejection frequency according to the voltage value of the control signal, but whereas the television video and audio signal is directly input from the amplifier 7 to the input terminal of the band rejection filter 8', the control signal is The signal is delayed because it is obtained after passing through the audio detector 13, bandpass filter 14, detector 15, and control circuit 11'. The amount of delay due to the difference in paths and the delay circuit 12' (7) on the transmitting side
It is understood that if the delay amounts are set to be equal, the closing frequency and the frequency fa of the sine wave signal used for encoding the television video signal will always match in the band rejection filter 8' of the receiving station. be done. Therefore, at the output of the band rejection filter 8', a signal decoded into a television video signal is obtained. The frequency spectrum of the decoded television video and audio signal is shown in FIG. The decoded television video and audio signals are supplied to a conventional television receiver.

In this embodiment, the receiving station performs decoding processing in the radio frequency band, but this decoding processing is performed by first converting the received television video and audio signal to an intermediate frequency, and then converting it to the intermediate frequency band. It is also possible to decode the received television video and audio signals in the baseband band.

Further, the band rejection filter whose rejection frequency can be changed used in this embodiment is, for example, as shown in FIG. 9, in which the rejection frequency is changed using a variable capacitance diode. In the figure, the terminal is the input terminal for the encrypted television signal, the terminal O is the output terminal for the decoded television signal, C is the capacitor, VR is the variable resistor for attenuation adjustment, and Ll and L2 are mutual inductances. VC is a variable capacitance diode, E is a DC power supply for supplying bias voltage, and ■ is a sine wave signal source for controlling the stopping frequency.

As is clear from the above explanation, according to the present invention, 1f,
Compared to conventional signal encryption processing methods, the frequency of the sine wave signal for encryption can be kept secret (and can be changed easily), which significantly improves the confidentiality of communication contents and allows The deterioration of the information signal decoded by

[Brief explanation of the drawing]

1A and 1B are block diagrams showing a conventional signal encryption processing method, FIGS. 2A and 2B are frequency spectrum diagrams of signals in the conventional method, and FIG. 3A. 6b and 6a and 6b are block diagrams showing the basic configuration of the system of the present invention, and FIGS. 4a and 4b and 7a are block diagrams, respectively. b is a block diagram showing each embodiment of the present invention based on these basic configurations, FIGS. 5a, b, and 8a,
b is a frequency spectrum diagram of the signal in each example,
FIG. 9 is a circuit diagram showing a specific example of a variable frequency band rejection filter. l... Information signal generator, 2... Sine wave oscillator, 3...
...Adder, 4.7...Transmission line interface equipment, 8...Band rejection, filter, 9.11...Switching circuit, 10°12...Control circuit. Patent applicant Clarion Co., Ltd. Figure 4 Figure 5

Claims (1)

[Scope of Claims] (1) means for generating a sine wave signal; and encryption means for adding the sine i-wave signal to an information signal to be transmitted and transmitting the resultant signal;
first control means for controlling the sine wave' signal generation means;
band-stop filter means for decoding an information signal from the encrypted received signal;
A signal encryption processing method comprising: a control means; and a second control means for controlling in accordance with the control. (21) The sine wave signal generating means comprises a plurality of sine wave oscillators of different frequencies, and the first control means includes a first switching circuit for selecting the sine wave oscillator and a first switching circuit for controlling the switching circuit. a control circuit, wherein the band-elimination filter means is selected from a plurality of band #IL rejection filters having different stop frequencies; and a second switching circuit in which the second control means selects the band-elimination filter; and the switching circuit. ``The signal encryption processing method according to claim 1'', characterized in that the signal encryption processing method is constituted by a second control circuit that controls the sine wave oscillator. , and the first control means has a sine wave frequency control circuit that changes the frequency of the sine wave oscillator,
The band-elimination filter means is comprised of a band-elimination filter of variable rejection frequency type, and the second control means is further comprised of a rejection subwave number control circuit for controlling the rejection frequency of the band-elimination filter. The signal encryption processing method described in item 1. (4) - The signal encryption processing system according to claims 2 and 3, characterized in that information regarding the frequency of the excitation sine wave is configured to be provided to the second control means. (5) Signal encryption processing according to claims 2 and 3, characterized in that the frequency of the sine wave and the rejection frequency of the band rejection filter match. method.