JP2940298B2 - Secret communication method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scrambling / descrambling system, and more particularly to a scrambling / descrambling system for countering weak electric fields.

[0002]

2. Description of the Related Art As shown in FIG. 2, a conventional scrambler 100 (hereinafter, referred to as an encoder) on a sending side is shown in FIG.
It comprises a receiving-side descrambler 200 (hereinafter, referred to as a decoder). The encoder and the encryption circuit 1 for encrypting individual information c, an encryption circuit 2 for encrypting the program information b, or scramble circuit 3 for scrambling communications signals a, a key generation circuit for generating a scramble key k _s 6
A timing signal generating circuit 4 for generating a scrambled timing signal;
It is possessed and SHF modulator 7 for modulating the signal of 2GHz band
You. Here, the scramble obtained by the key generation circuit 6
The key k _S is used as a part of the individual information in addition to the scramble circuit 3.
Is also input to the encryption circuit 2. The decoder has 12
SHF receiver 8 for demodulating a GHz band signal into communication signal a
And a decryption circuit 10 for decrypting the encrypted individual information c
And a decryption circuit 11 for decrypting the encrypted program information b
And a matching circuit 12 for matching the contents of the program information b and the individual information c, a descrambling circuit 14 for decoding the scrambled communication signal a, and a descrambling operation control circuit 13 for turning on / off the descrambling operation. . In the encoder, the master key k shared by the decoder and
_m , the individual information c including the work key k _W is encrypted by the encryption circuit 1, and the encryption circuit 2 encrypts the program information b including the scramble key k _s by the work key k _W , and the scramble circuit 3
Perform the scramble of the communication signal a scramble key k _s is. Scramble key k _s is updated in a short time according to the timing signal generated by the timing signal generating circuit 4.
The encrypted individual information c and the program information b are multiplexed on the communication signal a scrambled by the scramble circuit 3,
The signal is modulated by the SHF modulator 7 into a signal in the 12 GHz band. The decoder converts the transmitted 12 GHz band signal into an SHF
The receiver 8 demodulates and extracts the individual information c and the program information b multiplexed and encrypted with the communication signal a. The encrypted individual information c is decrypted using the master key k _m which have in common with the encoder in the decoding circuit 10, the workpiece is encrypted program information b included in the individual information in the decoding circuit 11 It is decoded using the key k _W. The contents of the decrypted individual information c and program information b are collated by the collation circuit 12 and sent. When it is determined that the communication signal a can be viewed, the descramble control circuit 13 is turned on,
Descrambling the encrypted communication signals a using the scramble key k _s that in the descramble circuit 14 included in the program information b.

[0003]

SUMMARY OF THE INVENTION A communication signal subjected to SHF modulation is affected by rainfall in a transmission path and the like, and C / N is deteriorated.
May scramble key k _s can not be correctly decoded when an error in the program information multiplexed occurred,
At that time, there was a disadvantage that the descrambling operation stopped.

An object of the present invention is to eliminate such a drawback, and an object of the present invention is to provide a secret communication system having means capable of continuing descrambling even when C / N deteriorates.

[0005]

SUMMARY OF THE INVENTION The present invention provides a scramble key generating means for generating a scramble key which is updated in a short time according to a given timing signal, and a pseudo random noise which generates the scramble key as an initial value. A scrambling device including scrambling means for scrambling a data signal using a signal, extracting means for extracting a scramble key arriving together with a scrambled data signal from the scramble device, and initializing the scramble key extracted by the extracting means. A descrambling device including a descrambler for descrambling the data signal scrambled by the scrambler using a pseudo-random noise signal generated as a value. Incoming signal Detecting means for generating an error signal when it is detected that the transmission error rate exceeds a predetermined value, a terminal on a separate line for feeding back the error signal generated by the detecting means to the scrambler, and the scrambler comprises: And a control circuit for stopping supply of a timing signal to the scramble key generating means in response to an error signal arriving via the terminal of the separate line and stopping updating of the scramble key.

Here, the control circuit may include means for restoring the supply of the timing signal to the scramble key generation means when the error signal arriving via the terminal of the separate line is cut off.

[0007]

When the transmission signal arriving at the descrambling device starts deteriorating due to the deterioration of the C / N, a signal indicating the occurrence of the error is fed back to the scrambling device via the telephone line, and the updating of the scramble key is stopped.
Scrambling and descrambling are performed using the scramble key fixed at the time of this stop. As a result, it is possible to prevent the scramble key from being decrypted correctly and the descrambling from being disabled.

[0008]

An embodiment of the present invention will be described below with reference to the drawings. This embodiment, as shown in FIG. 1, a scramble key generating means for generating a scramble key k _s to be updated in a short time according to a given timing signal the timing signal generating circuit 4 and the key generating circuit 6, and a scrambler 100 that includes a scrambling circuit 3 for scrambling a communications signal using a pseudo-random noise signal for generating the scramble key k _s as the initial value, the scramble key coming with scrambled communications signals from the scrambler 100 SHF receiver 8, which is extraction means for extracting k _s , decryption circuit 10 and decryption circuit 11, and scrambling using a pseudo-random noise signal generated using scramble key k _s extracted by this extraction means as an initial value. Communication signal scrambled by device 100 is descrambled That descramble circuit 1
4 including a descrambling device 200,
As a characteristic feature of the present invention, the descrambling device 2
00 is provided with an error detection circuit 9 which is a detection means for generating an error signal when it detects that the transmission error rate of a signal arriving at its own device exceeds a predetermined value, and converts the error signal generated by this detection means into a scramble device. 100 is provided with telephone line terminals 15 and 16 returning to
0 stops the supply of the timing signal to the scramble key generating means in response to the error signal arriving via the telephone line terminals 15 and 16, stops updating the scramble key, and stops the update of the scramble key. And a timing signal on / off circuit 5 which is a control circuit for restoring the supply of the timing signal to the scramble key generation means when the error signal arriving via the interface is cut off. Where the key
The scramble key k _S obtained by the raw circuit 6 is
The encryption circuit 2 as part of the individual information in addition to the encryption circuit 3
Is also entered.

Next, the operation of this embodiment will be described. In the encoder side, encrypted by the encryption circuit 1 the agreement and the work key k _W individual information c that contains the decoder by the master key k _m which have in common with each decoder, the program in the work key k _W It is encrypted by the encryption circuit 2 program information b that contain the classification and the scramble key k _s. The scramble key k _s is updated in a short time by the scramble timing signal obtained from the timing signal generation circuit 4, and the communication signal a is scrambled by the pseudo random noise signal PN generated using the scramble key k _s as an initial value in the scramble circuit 3, The encrypted individual information c and the program information b are multiplexed, and the SHF modulator 7
Modulated into bands. On the decoder side, the communication signal a modulated in the 12 GHz band is demodulated to the base band by the SHF receiver 8, the multiplexed digital signal is taken out, the error detector 9 detects the error of the frame synchronization, and is encrypted. The individual information c and the program information b are extracted. Master key k shared by the encoder with the decryption circuit 10
_m , the individual information c is decrypted, and the decryption circuit 11 uses the work key k _W included in the individual information c to program information b.
Is decrypted. The contents of the decrypted individual information c and the program information b are collated by the collation circuit 12, and when it is determined that the transmitted communication signal a is viewable, the descrambling control circuit 13 is turned on and the program information b is added. The included scramble key k _s is sent to the descrambling circuit 14. Communication signal a is descrambled by the descramble circuit 14 by a pseudo-random noise signal PN for generating a scramble key k _s as an initial value in contrast to the time of scrambling. here,
If the C / N deteriorates due to the influence of rain or the like during the propagation of the 12 GHz band modulated wave on the transmission line, the number of errors occurring in the frame synchronization error detection circuit 9 on the decoder side increases, and the number of errors increases to a predetermined level or more. Then, an error signal is output and sent to the encoder through the telephone line terminals 15 and 16. Error signal is input to the timing signal input switching circuit 5 in the encoder, and prevents the output of the scramble timing signal to stop the updating of the scramble key k _s, scramble key was last pass to C / N is restored A scrambling and descrambling operation is performed using a pseudo random noise signal generated using _ks as an initial value.

[0010]

According to the present invention, As described above, an error occurs in the program information multiplexed in the communication signal at C / N degradation due to rain or the like, the scramble key k _s is descrambling not be decoded correctly If it becomes impossible, the delivery of the scramble key is suspended, so that there is an effect that a system resistant to C / N deterioration can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a conventional example.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 encryption circuit 2 encryption circuit 3 scramble circuit (SC circuit) 4 timing signal generation circuit 5 timing signal on / off circuit 6 key generation circuit 7 SHF modulator 8 SHF receiver 9 error detection circuit 10 decryption circuit 11 decryption circuit REFERENCE SIGNS LIST 12 verification circuit 13 descrambling control circuit (DSC control circuit) 14 descrambling circuit (DSC circuit) 15 telephone line terminal 16 telephone line terminal 100 scrambler 200 descrambler

Claims (2)

(57) [Claims] 1. A scramble key generating means for generating a scramble key which is updated in a short time according to a given timing signal, and a data signal is scrambled by using a pseudo random noise signal generated by using the scramble key as an initial value. Device for extracting a scramble key arriving with the scrambled data signal from the scramble device, and a pseudo-random noise signal generated using the scramble key extracted by the extractor as an initial value. In a secret communication system including a descrambling device including descrambling means for descrambling the data signal scrambled by the scrambling device, the descramble device has a transmission error rate of a signal arriving at its own device. Predetermined value Detecting means for generating an error signal when detecting that the error signal has been received, a terminal on a separate line for returning the error signal generated by the detecting means to the scrambler, and the scrambler via the terminal on the separate line. A secret communication system, comprising: a control circuit for preventing a timing signal from being supplied to the scramble key generation means in response to an error signal arriving at the terminal and stopping updating of the scramble key. 2. The control circuit according to claim 1, wherein said control circuit includes means for restoring supply of a timing signal to said scramble key generation means when an error signal arriving via a terminal of said another line is cut off. Secret communication system.