JPH03196731A - Scramble communication system - Google Patents

Abstract

PURPOSE:To prevent a random number generating pattern from being decoded by an illegal party and to improve the reliability by reproducing a key signal at a receiver side, selecting a random number signal generating pattern from plural predetermined patterns and generating the pattern. CONSTITUTION:A reception signal inputted from an antenna 41 is demodulated via a converter 42 and an FM demodulation circuit 43, expanded by a de- emphasis circuit 44 and a video signal is outputted from an output terminal 47 via an LPE 45, an energy disperser 46. Moreover, a scrambled signal outputted from the demodulator 43 is demodulated via a BPF 48 and a demodulator 49. Demodulated 2-bit data P, Q are converted into an original digital data by a converter 50 and a key signal multiplexed by a multiplex signal demultiplexer 51 is demultiplexed. The key signal is inputted to an address generator 62 via an error correction circuit 61 and an address in response to the key signal is inputted to a RAM 63 and an output data of the RAM 63 is inputted to a random number generator 64 as an initial value and a random signal pattern in response to the initial value is outputted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a scramble communication system used, for example, in a satellite broadcasting system.

(Prior Art) Satellite broadcasting systems using artificial satellites have been developed. In this system, for example, radio waves transmitted from a broadcasting center are relayed by a broadcasting satellite and transmitted to another broadcasting center or directly to a user's receiver.

Here, when operating pay broadcasting, a transmitting device at a broadcasting center scrambles a broadcast signal, and a receiving device receives the scrambled signal and performs descrambling. A system that performs such processing is called a scramble communication system.

In a conventional scramble communication system, a transmitting device adds a random number signal from a random number generator to a signal to be transmitted (for example, an audio signal) and scrambles it to create a scrambled signal, and a receiving device scrambles the signal (for example, an audio signal). It receives the signal, generates random numbers with the same pattern as the transmitter, and adds this random number signal to the scrambled signal.

Thereby, the scrambled signal is descrambled and reproduced as the original audio signal.

Here, the random number signal on the sending side and the random number signal on the receiving side are:
Must occur in exactly the same pattern. For this purpose, the initial value of the random number generator is transmitted from the transmitting side through another communication path, and the receiving side uses this initial value to obtain the generation pattern of the random number signal. In this way, the transmitting side and the receiving side each have a random number generator that generates the same random number generation pattern, and performs scrambling and descrambling processing.

(Problems to be Solved by the Invention) According to the conventional scramble communication system described above, eavesdropping is possible when the random number generation pattern of the random number generator is decoded. Since there is only one random number generation pattern in the conventional system, the generation pattern can be found by analyzing the pattern of the long-term scramble signal.

SUMMARY OF THE INVENTION An object of the present invention is to provide a highly reliable scramble communication system that can prevent random number generation patterns from being decoded by unauthorized persons.

[Structure of the Invention] (Means for Solving the Problems) The present invention provides that a signal transmitted by a transmitting device is scrambled by a random number signal from a transmitting side random number signal generating means and transmitted as a scrambled signal, and a signal transmitted by a transmitting device is transmitted as a scrambled signal. In a scrambled communication system in which the scrambled signal received by the receiver is restored to the original signal using a random number signal from a receiving side random number signal generating means, the transmitting device includes means for transmitting a key signal; The receiving side random number generating means of the receiving device includes means capable of generating a plurality of types of random number signal patterns, and means for selecting a random number signal pattern in correspondence with the key signal, a key signal reproducing means for reproducing a key signal to be generated; and a key signal reproducing means capable of selectively generating a plurality of random number signal patterns, the type of the random number signal pattern to be generated being determined according to the content of the reproduced key signal, and The random number signal pattern setting means is replaceable from the outside.

(Function) With the above means, even if the key signal is decoded, the random number signal generation pattern can be selectively generated from among a plurality of patterns predetermined by the sending side and the receiving side. The probability that the signal generation pattern will be decoded by an unauthorized person is extremely reduced.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a transmitting device according to an embodiment of the present invention,
FIG. 3 shows the receiving device. In FIG. 1, an input terminal 11 is supplied with a broadcast video signal, and an input terminal 12 is supplied with an audio signal. The video signal is band-compressed by a pre-emphasis circuit 13 and then supplied to an FM modulator 21 via a low-pass filter 14 . On the other hand, input terminal 12
The audio signal is digitized by an analog-to-digital converter 15 and input to a scrambler 16. This scrambler 16 is supplied with random number signals from an M-sequence random number signal generator. The scrambled audio signal is
The signal is input to the multiplexer 17.

In this multiplexing device 17, a key signal from a pattern setting section (a section instructing a random number signal generation pattern) is multiplexed onto a scrambled signal. The scrambled signal output from the multiplexer 17 is input to the differential converter 18.

The differential converter 18 performs preprocessing for performing quadrature phase modulation on the scrambled signal, and creates data P and Q indicating in which position of the four quadrants the scrambled signal is located. This data is.

It is input to a four-phase phase (QPSK) modulator 19,
After being modulated with different carrier waves, they are added together to form a serial signal and are output. The output of the QPSK modulator 19 is band-limited by a bandpass filter 20 and sent to an FM modulator 21.
is man-powered. The signal frequency modulated by the FM modulator 21 is converted into a 12 GHz band radio wave by the up converter 22, and is emitted from the antenna 23 toward the satellite.

Reference numeral 31 denotes a pattern setting section, which can change the generation pattern of the random number signal. When the pattern setting section 31 is operated, the address generator 32 outputs an address corresponding to the key operation, and is supplied to the read address input section of the ROM 33.

The data output from the ROM 33 is sent to the random number signal generator 3.
The initial value of 4 is supplied to the human power section. As a result, the random number signal generation pattern of the random number signal generator 34 is determined.

The ROM 33 has a plurality of data, and by selectively reading this data, the type of random number signal generation pattern in the random number signal generator 34 can be changed. This change information is also transmitted to the receiving side through the key signal.

FIG. 2 shows an example of the configuration of the random number signal generator 34 using the generating polynomial X'2+X'+1. That is, a latch circuit 34° and a unit delay element are used to latch the initial value.

- Dll, which has an exclusive OR circuit 342.

In the above device, there are currently 5 data for pattern setting.
If it is a bit, 32 patterns can be set. Further, the multiplexing device f17 receives as a key signal a signal obtained by adding an error correction code to the above 5 bits.

FIG. 3 shows a receiving apparatus, in which a received signal input from an antenna 41 is frequency-converted by a down converter 42 and input to an FM demodulator 43.

The video signal demodulated by the FM demodulator 43 is decompressed by a de-emphasis circuit 44 and sent to an energy disperser 46 via a low-pass filter 45 . The video signal output from the energy disperser 46 is sent to the output terminal 47.
is derived.

Furthermore, the scrambled signal output from the FM demodulator 43 is input to a four-phase phase demodulator 49 via a bandpass filter 48. The demodulated 2-bit data P, . . . Q is converted into original digital data in a differential converter 50. The output of the differential converter 50 is input to a multiplex signal demultiplexer 51. The multiplexed signal separation device 51 separates the multiplexed key signal, and the remaining scrambled signal is input to the descrambler 52.

A random number signal from a random number signal generator 64 is supplied to the descrambler 52, and a descrambled signal can be obtained at the output section. The descrambled signal is
The signal is input to a digital-to-analog converter 53 and converted into an analog audio signal.

This audio signal is led out to the output terminal 54.

The key signal separated by the multiplex signal separation device 51 is input to an error correction circuit 61, subjected to error correction, and then supplied to an address generator 62. This causes the address generator 62
An address corresponding to the contents of the key signal is generated from R.
Supplied to the addressing terminal of AM63. RAM63
The data output from the random number signal generator 64 is supplied as an initial value to the random number signal generator 64. As a result, the random number signal generator 64 generates a random number signal pattern according to the initial value. In other words, a random number signal exactly the same as that on the transmitting side is generated, and descrambling by the descrambler 52 is obtained. RAM6
When the data output from 3 is all "0", the NOR circuit 66 detects this and outputs the non-scrambled signal (
In other words, it detects that it is in a broadcasting state (free of charge). This detection signal is supplied to a display device and can inform that it is in a pay broadcast state (scrambled) or a free broadcast state (unscrambled). Note that at this time, the random number signal generator 6
4 always outputs "0", so the descrambler 52 does not perform a descrambling operation.

Here, the data stored in the RAM 63 is, for example, data transferred from the IC card 65, and is mailed from the broadcasting center based on a contract or fee payment. This IC card 65 stores multiple types of initial values of random number signals used to scramble the signal of the program when the user subscribes to a pay program or pays for the program. has been done.

In this embodiment, confidentiality is further enhanced by making the initial value different for each user. Then, it is transferred to the RAM by the card reading device. Similar initial values are also stored in the ROM 33 of the transmitter.

FIG. 4 shows the correspondence between the data content of the key signal and the random number signal generation pattern. If the data is 5 bits,
32 initial values can be set, and 32 random number signal generation patterns can be obtained. Note that if one of these random number generation patterns is all aO#, it can be shown that the non-scrambled signal is being broadcast.

According to the scramble communication system described above, the IC card 65 is mailed to the user here. Therefore,
The random number signal generation pattern for descrambling is
It is selectively determined from among a plurality of signals at the receiving terminal here. The determining factor is the key signal transmitted from the transmitting device. Therefore, only the key signal exists during signal transmission, and even if the key signal is decoded by an unauthorized person, a random number signal cannot be generated. Even if you receive a descramble code in the middle of transmission and try to decipher the generation pattern of the random number signal, the system of this embodiment allows you to change the generation pattern of the random number signal in multiple ways, so you can easily decipher it. difficult to do.

Moreover, if there is a possibility that the generation pattern of the random number signal has been decoded by an unauthorized person, the broadcasting center can change the generation pattern using a key signal, thereby ensuring extremely high secrecy.

[Effects of the Invention] As explained above, the present invention can prevent a random number generation pattern from being decoded by an unauthorized person, and can improve the reliability of confidentiality.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a transmitting device according to an embodiment of the present invention, FIG. 2 is a diagram showing an example of the random number signal generator of FIG. 1, and FIG.
FIG. 4 is a diagram showing a receiving apparatus according to an embodiment of the present invention, and FIG. 4 is a diagram showing the correspondence between the data contents of a key signal and a random number signal generation pattern. 13... Pre-emphasis circuit, 14... Low-pass filter, 15... Analog-to-digital converter, 16...
Scrambler, 17... Multiplexer, 18... Differential converter, 19... Four-phase phase modulator, 20... Bandpass filter, 21... FM modulator, 22... Up Converter, 23.41...Antenna, 31...Pattern setting section, 32...Address generator, 33...R
OM, 34... Random number signal generator, 42... Down converter, 43... FM demodulator, 44... De-emphasis, 46... Low pass filter, 48... Bandpass filter, 49... ... Four-phase phase demodulator, 50 ... Differential converter, 51 ... Multiplex signal separation device, 52 ... Descrambler, 53 ... Digital-to-analog converter, 6
1...Error correction circuit, 62...Address generator, 6
3...RAM, 64...Random number signal generator, 65...
・IC card, 66...NAND circuit.

Claims (1)

[Claims] A signal transmitted by a transmitting device is scrambled by a random number signal from a random number signal generating means on the transmitting side and transmitted as a scrambled signal, and the scrambled signal received by the receiving device is transmitted to the receiving side. In a scrambled communication system in which the original signal is restored using a random number signal from a random number signal generation means, the transmitter includes means for transmitting a key signal, means capable of generating a plurality of types of random number signal patterns, means for selecting a random number signal pattern corresponding to the key signal, and the receiving side random number signal generating means of the receiving device includes key signal reproducing means for reproducing the key signal transmitted from the transmitting device. , random number signal pattern setting means capable of selectively generating a plurality of random number signal patterns, the type of the random number signal pattern to be generated being determined according to the content of the reproduced key signal, and exchangeable from the outside; A crumble communication system characterized by comprising: