JP5029815B2 - Descrambler, communication device, identification method and program - Google Patents

Description

  The present invention relates to a descrambler, a communication device, a communication system, a generator polynomial, and an initial value identification method and program.

  The scrambler plays two main roles in communication. One is to stir the 0 and 1 bit strings to be transmitted, reduce the continuity of the 0 and 1 bit strings, and increase the transmission efficiency. The other is a role as a so-called encryption method for preventing interception by a malicious third party.

  In recent years, information leakage typified by eavesdropping has become a social problem, and it has become common for communication data to have some confidentiality. In this respect, the scrambler can encrypt at a higher speed than a cipher such as AES (Advanced Encryption Standard).

  However, the scrambler is easier to decipher than an encryption method such as AES. Therefore, when scrambler decoding is detected, the scrambler generation polynomial and the initial value are changed. This change must be made at both the transmitter and receiver. A conventional method is shown in FIG.

  As shown in FIG. 4, the transmitter 14 and the receiver 15 set the same generator polynomial and initial value pair in the synchronous scrambler 1 and the synchronous descrambler 8, scramble the information data to be transmitted, Descramble on the receiving side.

  As a method for changing the generator polynomial and initial value of the scrambler 1 from the outside of the apparatus for security preservation or the like, information relating to the generator polynomial and the initial value is inserted into the information to be transmitted and output from the receiver 15. The information is extracted from the decoded data, and the descrambler generating polynomial and initial value are changed.

  However, in the above-described method, it is necessary to always transmit data only for the scrambler generating polynomial and the initial value, and there is a problem that the information transmission efficiency is deteriorated.

  In addition, as a method of not inserting information related to the generator polynomial and the initial value into the information data, there is a method of transmitting the information related to the generator polynomial and the initial value by another transmission means. There was a problem in terms of.

  Accordingly, the present invention has been invented in view of the above problems, and its purpose is to insert information that the transmitter side has changed the generator polynomial and initial value of the scrambler into the information data to be transmitted. It is another object of the present invention to provide a technique capable of identifying a set of generator polynomials and initial values without transmission from the transmitter side to the receiver side by other means.

The present invention that solves the above-described problem is a descrambler that uses a storage means that stores a plurality of pairs of generator polynomials and initial values, and uses the generator polynomials and initial values stored in the storage means to input data. Descrambling means for descrambling and outputting decoded data, calculating an entropy value of the decoded data, comparing the entropy value with a predetermined threshold, and if the entropy value exceeds the predetermined threshold, Determination means for changing a set of generator polynomial and initial value used by the descrambling means to the next generator polynomial and initial value stored in the storage means until an entropy value becomes smaller than the predetermined threshold. It is characterized by that.

The present invention for solving the aforementioned problems is a descrambler, and storage means for plurality storing a set of generator polynomials and the initial value, based on the instruction, the generator polynomial and the initial value stored in said storage means Using any generator polynomial and initial value of the set, descrambling means for descrambling the input data and outputting decoded data, calculating an entropy value of the decoded data, and calculating the entropy value and a predetermined threshold value comparison, if the entropy value exceeds the predetermined threshold, the set of changes of the generator polynomial and the initial value used by the descrambling means possess a determining means for instructing said descrambling means, said descrambling means When receiving an instruction to change the generator polynomial and the initial value, to set the following generator polynomial and the initial value stored in said storage means And butterflies.

  The present invention for solving the above-described problems is a communication device having the descrambler.

The present invention for solving the aforementioned problem is a communication system, the first storage means, said first generating polynomial and an initial value stored in the memory means for a plurality storing a set of generator polynomials and the initial value A scrambler that scrambles and outputs data using any of the generator polynomials and initial values of the set, a second storage unit that stores the same generator polynomial and initial value pair as the scrambler, and instructions Based on this, the generator polynomial and initial value of one of the generator polynomial and initial value sets stored in the second storage means are used to descramble the scrambled data and output decoded data. The scramble means calculates an entropy value of the decoded data, compares the entropy value with a predetermined threshold value, and the entropy value exceeds the predetermined threshold value. If the set of changes of the generator polynomial and the initial value said descrambling means is used possess a determination means for instructing said descrambling means, said descrambling means, receiving an instruction to change the generator polynomial and the initial value And the next generator polynomial and initial value stored in the second storage means are set .

The present invention for solving the above problems is a method of identifying a generator polynomial and initial value of a scrambler, wherein the descrambler scrambles by a scrambler on the transmission side using one of a set of a plurality of generator polynomials and initial values. the input data, using either set of the plurality of generator polynomials and the initial values stored in the memory, and descrambling, the descrambler calculates the entropy value of the decoded data obtained by descrambling The calculated entropy value is compared with a predetermined threshold value, and when the calculated entropy value exceeds the predetermined threshold value, a set of generator polynomial and initial value used for descrambling is stored in the memory. change to the following generator polynomial and the initial value is, if the calculated entropy value is smaller than the predetermined threshold , A set of generator polynomials and the initial value used in descrambling, and identifying as a set of generator polynomials and the initial value used in the scrambling by the scrambler of the sender.

The present invention for solving the above-described problems is a descrambler program, which uses a generator polynomial and an initial value stored in a memory to descramble input data and output decoded data; and the decoded data The entropy value is calculated, and the entropy value is compared with a predetermined threshold value. When the entropy value exceeds the predetermined threshold value, the entropy value is used for the descrambling until the entropy value becomes smaller than the predetermined threshold value. The descrambler executes a process of changing a set of generator polynomial and initial value to the next generator polynomial and initial value stored in the memory .

  The present invention inserts information that the transmitter side has changed the generator polynomial and initial value of the scrambler into the information data to be transmitted, or transmits the information from the transmitter side to the receiver side by another means. Even if not, it has an excellent effect that a set of generator polynomials and initial values can be identified.

  An embodiment of the present invention will be described.

  FIG. 1 is a block diagram showing the configuration of the embodiment of the present invention. In addition, the same code | symbol was attached | subjected about the thing similar to FIG. 4 which showed the prior art.

  The embodiment of the present invention includes a transmitter 12 and a receiver 13.

  The transmitter 12 includes a frame synchronization scrambler 1, a modulator 2, a control circuit 3, a memory 4, and an antenna 5.

  The frame-synchronized scrambler 1 sets a generator polynomial and an initial value by external control, and scrambles an input 0,1 bit string with the generator polynomial and the initial value. The scrambled 0, 1 bit string is output with a unique word added for each scramble period.

  The modulator 2 demodulates the input 0, 1 bit string by a digital modulation method such as QPSK, and outputs an RF signal.

  The control circuit 3 controls the change of the generator polynomial and the initial value according to an instruction from the outside.

The memory 4 stores a plurality of generator polynomial and initial value data sets (G _j , I _j ) (j is a natural number), and the generator polynomial and initial value data are transferred to the frame synchronous scrambler 1 by external control. Output.

  The antenna 5 radiates the input RF signal into the air.

  The receiver 13 includes an antenna 6, a demodulator 7, a frame synchronization descrambler 8, an entropy determination circuit 9, a memory 10, and a control circuit 11.

  The antenna 6 receives radio waves radiated into the air and outputs an RF signal.

  The demodulator 7 receives the RF signal, demodulates it with QPSK, etc., and outputs 0 and 1 bit strings.

  The frame synchronous descrambler 8 removes the unique word from the input 0 and 1 bit strings, and descrambles with the same generator polynomial and initial value as the frame synchronous scrambler 1 set in advance.

  The entropy determination circuit 9 calculates the entropy value of the input 0 and 1 bit string data by the arithmetic circuit 15.

  The memory 10 stores the same set of generator polynomials and initial values as in the memory 4, and outputs the generator polynomials and initial values under external control.

  The control circuit 11 controls the change of the generator polynomial and the initial value when the change instruction signal is input.

  Next, details of the entropy determination circuit 9 are shown in FIG.

  The entropy determination circuit 9 includes a distributor 13, a memory 14, an arithmetic circuit 15, a determination circuit 16, and a memory 17.

  The distributor 13 distributes the input 0 and 1 bit strings equally and outputs the result.

  The memory 14 accumulates a certain amount of the input 0 and 1 bit strings and outputs a certain amount.

  The arithmetic circuit 15 calculates entropy and outputs an entropy value for a certain amount of 0 and 1 bit strings inputted.

  The determination circuit 16 compares the two input values to determine whether to output a change instruction output.

  Next, the operation of the above configuration will be described. FIG. 3 is a flowchart showing the operation of the embodiment.

Usually, the transmitter 12 and the receiver 13 are scrambled by the control circuit 3, the memory 4 controlled by the control circuit 11, and the same generator polynomial and initial value set (G _j , I _j ) output from the memory 10, Descramble is performed and communication is performed.

  On the other hand, in the present invention, the operation when the generator polynomial and the initial value of the synchronous scrambler 1 are changed for security protection and the like will be described below.

When an instruction to change the set of generator polynomial and initial value of the frame synchronous scrambler 1 is sent from the outside to the control circuit 3 (Step 100), the control circuit 3 sends a set of generator polynomial and initial value to the memory 4 ( G _j , I _j ) is set to (G _k , I _k ) (k is a natural number, k ≠ j), and a set of generator polynomials and initial values (G _k , I _k ) is output to the frame synchronous scrambler 1 Control to do.

As a result, a set of generator polynomials and initial values (G _k , I _k ) is set in the frame synchronous scrambler 1 (Step 101). The information data of the 0 and 1 bit strings input to the frame synchronous scrambler 1 is a set of generator polynomials and initial values (G _k , I _k ) from where the setting of the frame synchronous scrambler 1 is changed. It will be scrambled by (Step 102).

  The scrambled 0 and 1 bit string data is modulated into a digital signal such as QPSK by the modulator 2 and output to the aerial 5, and the aerial 5 radiates the digitally modulated signal into the air (Step 103).

  The antenna 6 receives the radio wave radiated from the antenna 5 (Step 104), and outputs the received digital modulation signal to the demodulator 7. The demodulator 7 demodulates the received digital modulation signal into 0 and 1 bit string data. Bit string data of 0 and 1 is input to the descrambler 8.

Here, since the frame synchronous descrambler 8 is still set to the generator polynomial and initial value pair (G _j , I _j ), the input 0,1 bit string data is not correctly decoded and remains agitated. Is output to the entropy determination circuit 9 (Step 105).

  The entropy determination circuit 9 calculates the entropy value of the input 0, 1 bit string data by the arithmetic circuit 15 (Step 106), and compares this entropy value with a predetermined threshold value (Step 107).

  Here, since the input 0 and 1 bit string data is not correctly decoded, the entropy value exceeds the threshold value stored in the memory 17 (Step 108). Therefore, the determination circuit 16 instructs the control circuit 11 to change the combination of the generator polynomial and the initial value (Step 109).

When receiving the change instruction, the control circuit 11 controls to delete the generator polynomial and the initial values (G _j , I _j ) set for the frame synchronous descrambler 8. Further, the memory 10 is controlled to output the stored next generation polynomial and initial value pair (G _{j + 1} , I _{j + 1} ) to the frame synchronous scrambler 8.

  The frame synchronization scrambler 8 sets the generator polynomial and initial value pair (Gj + 1, Ij + 1) output from the memory 10, and descrambles the 0 and 1 bit string data in this combination from the next synchronization point (Step 105). ).

The entropy determination circuit 9 again calculates the entropy value of the changed 0, 1 bit string data (Step 106), and the comparison with the threshold is performed (Step 107). If the entropy value seems to exceed the threshold (Step 108), it is set to the next set of generator polynomial and initial value (G _{j + 2} , I _{j + 2} ) (Step 109).

In this way, the set of generator polynomials and initial values is changed sequentially. When the entropy value of the descrambled 0, 1 bit string data falls below the threshold (Step 108), it is correctly descrambled. At this time, the set of generator polynomial and initial value is (G _k , I _k ) Thus, the identification of the set of generator polynomials and initial values set in the crambler 1 is completed (Step 110).

  As described above, according to the present invention, the information that the transmitter side has changed the generator polynomial and initial value of the scrambler is inserted into the information data to be transmitted or received from the transmitter side by another means. A set of generator polynomials and initial values can be identified without transmission to the machine side.

  The present invention is not limited to the above-described embodiment, and for example, the digital modulation method can be applied to other digitally modulated wireless communications such as 8PSK and 16QAM methods. Further, the communication method is not limited to wireless communication, but can be applied to transmission communication using a transmission path.

  Furthermore, in the present embodiment, each unit of the transmitter and the receiver is configured by hardware. However, each unit may be configured by a program that causes the CPU to operate as described above.

FIG. 1 is a block diagram showing the configuration of the embodiment of the present invention. FIG. 2 is a diagram showing details of the entropy determination circuit 9. FIG. 3 is a flowchart showing the operation of the embodiment of the present invention. FIG. 4 is a diagram for explaining the prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Frame synchronous scrambler 2 Modulator 3 Control circuit 4 Memory 5 Antenna 6 Aerial 7 Demodulator 8 Frame synchronous descrambler 9 Entropy determination circuit 10 Memory 11 Control circuit 13 Divider 14 Memory 15 Operation circuit 16 Determination circuit

Claims (6)

A descrambler,
Storage means for storing a plurality of sets of generator polynomials and initial values;
Descrambling means for descrambling input data and outputting decoded data using a generator polynomial and an initial value stored in the storage means ;
An entropy value of the decoded data is calculated, and the entropy value is compared with a predetermined threshold value. When the entropy value exceeds the predetermined threshold value, the detropy value is reduced until the entropy value becomes smaller than the predetermined threshold value. A descrambler, comprising: a determining polynomial that changes a set of generator polynomials and initial values used by the scrambler to a next generator polynomial and initial value stored in the storage unit . A descrambler,
Storage means for storing a plurality of sets of generator polynomials and initial values ;
A descrambling unit that descrambles input data and outputs decoded data using a generator polynomial and an initial value of a set of generator polynomials and initial values stored in the storage unit based on an instruction;
The entropy value of the decoded data is calculated, the entropy value is compared with a predetermined threshold value, and when the entropy value exceeds the predetermined threshold value, the generator polynomial used by the descrambling means and the initial value set are changed. It possesses a determination means for instructing said descramble means,
The descrambler, wherein the descrambler sets a next generator polynomial and initial value stored in the storage unit when receiving an instruction to change the generator polynomial and initial value .   A communication device comprising the descrambler according to claim 1. A communication system,
First storage means for storing a plurality of sets of generator polynomials and initial values;
Scramble means for scrambling and outputting data using a generator polynomial and an initial value of a set of generator polynomial and initial value stored in the first storage means ;
Second storage means for storing the same generator polynomial and initial value set as the scramble means;
Based on the instruction, the scrambled data is descrambled and the decoded data is output using one of the generator polynomial and the initial value of the generator polynomial and initial value set stored in the second storage unit. Descrambling means to perform,
The entropy value of the decoded data is calculated, the entropy value is compared with a predetermined threshold value, and when the entropy value exceeds the predetermined threshold value, a set of generator polynomial and initial value used by the descrambling means It possesses a determination means for instructing a change to the descrambling means,
The descrambling means sets a next generating polynomial and initial value stored in the second storage means when receiving an instruction to change the generating polynomial and initial value. . A method for identifying a generator polynomial and initial values of a scrambler,
The descrambler selects one of a plurality of generator polynomials and initial value pairs stored in memory from the input data scrambled by the scrambler on the transmission side using one of a plurality of generator polynomials and initial value pairs. To descramble,
When the descrambler calculates the entropy value of the decoded data obtained by descrambling, compares the calculated entropy value with a predetermined threshold, and when the calculated entropy value exceeds the predetermined threshold Changes the set of generator polynomial and initial value used for descrambling to the next generator polynomial and initial value stored in the memory, and when the calculated entropy value is smaller than the predetermined threshold, Identification of generator polynomial and initial value of scrambler characterized by identifying generator polynomial and initial value pair used for descrambling as generator polynomial and initial value set used for scramble by transmitting side scrambler Method. A descrambler program,
Using the generator polynomial and initial value stored in the memory, the process of descrambling the input data and outputting the decoded data;
An entropy value of the decoded data is calculated, and the entropy value is compared with a predetermined threshold value. When the entropy value exceeds the predetermined threshold value, the detropy value is reduced until the entropy value becomes smaller than the predetermined threshold value. A program for causing a descrambler to execute processing for changing a set of generator polynomials and initial values used for scrambling to the next generator polynomial and initial values stored in the memory .

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