JP2007241256A - Data transmission apparatus, data receiving apparatus and data communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-confidentiality data communication apparatus, based on astronomical complexity and causes an eavesdropper to take a significantly increased time to analyze a cipher text. <P>SOLUTION: In a multi-level code generation section 111a, a random number sequence generation section 141 generates, based on predetermined key information 11, a plurality of modulation pseudo-random number sequences. The plurality of modulation pseudo-random number sequences are inputted to a multi-level conversion section 142, as a part of an input bit sequence which is converted into a multi-level code sequence 12. A multi-level processing section 111b combines the multi-level code sequence 12 and information data 10, and generates a multi-level signal 13, having a plurality of levels corresponding to the combination of the multi-level code sequence 12 and the information data 10. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an apparatus and method for performing cryptographic communication to prevent illegal eavesdropping and interception by a third party, and more specifically, a specific encoding / decoding (modulation / demodulation) scheme between authorized senders and receivers. The present invention relates to a data transmission device, a data reception device, and a data communication method that perform data communication by selecting and setting the.

  Conventionally, in order to communicate only with specific persons, key information for encoding / decoding is shared between transmission / reception, and information data (plain text) to be transmitted is mathematically calculated based on the key information. In other words, a configuration is adopted in which secret communication is realized by performing computation / reverse computation. FIG. 17 is a block diagram showing a configuration of a conventional data communication apparatus based on such a configuration.

  In FIG. 17, the conventional data communication apparatus has a configuration in which a data transmission apparatus 9001 and a data reception apparatus 9002 are connected by a transmission path 913. The data transmission apparatus 9001 includes an encoding unit 911 and a modulation unit 912. The data reception device 9002 includes a demodulation unit 914 and a decoding unit 915.

  In the data transmission device 9001, information data 90 and first key information 91 are input to the encoding unit 911. The encoding unit 911 encodes (encrypts) the information data 90 based on the first key information 91. The modulation unit 912 converts the information data 90 encoded by the encoding unit 911 into a modulation signal 94 having a predetermined modulation format, and sends the modulation signal 94 to the transmission path 913.

  In the data receiving device 9002, the demodulator 914 demodulates the modulated signal 94 transmitted via the transmission path 913 by a predetermined demodulation method. The decryption unit 915 receives second key information 96 that is the same as the first key information 91. The decrypting unit 915 decrypts (decrypts) the modulated signal 94 based on the second key information 96 and outputs information data 98.

  Here, an eavesdropping action by a third party will be described using the eavesdropper receiving device 9003. In FIG. 17, an eavesdropper receiving device 9003 includes an eavesdropper demodulation unit 916 and an eavesdropper decoding unit 917. The eavesdropper demodulation unit 916 demodulates the modulation signal 94 propagating through the transmission path 913 using a predetermined demodulation method. Based on the third key information 99, the eavesdropper decoding unit 917 attempts to decode the signal demodulated by the eavesdropper demodulation unit 916. Here, the eavesdropper decryption unit 917 attempts to decrypt the signal demodulated by the eavesdropper demodulation unit 916 on the basis of the third key information 99 different from the first key information 91. It cannot be played correctly. That is, since the eavesdropper decryption unit 917 does not share correct key information with the data transmission device 9001, the information data 98 cannot be reproduced correctly.

Such mathematical encryption (or also called calculation encryption or software encryption) technology based on mathematical operations can be applied to an access system or the like as described in Patent Document 1, for example. That is, in a PON (Passive Optical Network) system in which an optical signal transmitted from one optical transmitter is branched by an optical coupler and distributed to optical receivers at a plurality of optical subscriber houses, each optical receiver includes: In addition to the desired optical signal, a signal directed to another subscriber is input. Therefore, in the PON system, by using different key information for each subscriber and encrypting the information data for each subscriber, leakage and wiretapping of each other's information is prevented, and safe data communication is realized.
JP-A-9-205420 Translated by Keiichiro Ishibashi, “Cryptography and Network Security: Theory and Practice”, Pearson Education, 2001 Mayumi Adachi et al., "Encryption Technology Encyclopedia", Softbank Publishing, 2003

  Among mathematical ciphers, a method called stream cipher has a simple configuration in which a ciphertext is generated by performing an XOR operation on a pseudorandom number sequence output from a pseudorandom number generator and information data (plaintext) to be encrypted. Therefore, there is an advantage that it is advantageous for speeding up. On the other hand, the security of stream ciphers has the drawback of relying only on pseudo-random number generators. That is, if an eavesdropper can obtain a combination of plaintext and ciphertext by some method, the pseudorandom number sequence can be accurately known (this is generally called a known plaintext attack). Furthermore, since the initial value of the pseudo random number generator, that is, the key information and the pseudo random number sequence are uniquely associated, the key information can be reliably obtained by applying some kind of decryption algorithm. Furthermore, since the processing speed of computers has been remarkably improved in recent years, there has been a problem that the danger of decrypting ciphertexts in a realistic time has increased.

  Therefore, an object of the present invention is to introduce an indeterminate element into the mutual relationship between the key information, the pseudo random number sequence, and the ciphertext, so that an eavesdropper can analyze the ciphertext compared to the conventional stream cipher. It is to provide a highly confidential data communication device that increases the labor required, that is, the amount of calculation.

  The present invention is directed to a data transmitting apparatus that encrypts information data using predetermined key information and performs secret communication with a receiving apparatus. In order to achieve the above object, a data transmission apparatus according to the present invention includes a multi-level code generation unit that generates a multi-level code sequence whose signal level changes in a substantially random manner based on predetermined key information, A multi-level processing unit that synthesizes the value code string and the information data and generates a multi-level signal having a plurality of levels corresponding to the combination of the multi-level code string and the information data, and a predetermined modulation process on the multi-level signal And a modulation unit that outputs the signal as a modulation signal. The multi-level code generation unit includes a random number sequence generation unit configured to generate a plurality of modulation pseudo-random number sequences based on predetermined key information, and a plurality of bit sequences including at least a part of the plurality of modulation pseudo-random number sequences. Is input as an input bit string, and includes a multi-value conversion unit that converts the input bit string into a multi-value code string. However, it is assumed that the number of input bit strings to the multi-value conversion unit is larger than the number of modulation pseudo random sequences generated by the random number sequence generation unit.

  Preferably, the multilevel processing unit assigns different values of information data to adjacent multilevel levels of the multilevel signal.

  At least one of the plurality of modulation pseudo-random number sequences is input to the multilevel conversion unit as the least significant bit of the input bit sequence.

  Preferably, the multi-level code generation unit further includes a physical random number generation unit that generates one or more physical random number sequences. In such a case, one or more physical random number sequences are input to the multilevel conversion unit as the remaining bit sequences excluding the pseudo random number sequence for modulation from the input bit sequence.

  In addition, a fixed value may be input to the multi-value conversion unit as the remaining bit string excluding the modulation pseudo-random number sequence from the input bit sequence.

  Preferably, the multi-level code generation unit further includes a physical random number generation unit that generates one or more physical random number sequences. In such a case, one or more physical random number sequences are input to the multilevel conversion unit as a part of the input bits excluding the pseudo random number sequence for modulation, and a fixed value is input as the remaining bit sequence. The

  In addition, a signal generated based on a predetermined rule may be input to the multi-level conversion unit as the remaining bit sequence excluding the modulation pseudo-random number sequence from the input bit sequence. A signal generated based on a predetermined rule can be generated by delaying a part or all of a plurality of modulation pseudo-random number sequences by a predetermined time.

  However, it is necessary to satisfy the condition that the ratio between the information amplitude corresponding to the amplitude of the information data and the fluctuation range of the multilevel signal corresponding to the physical random number sequence is larger than the signal-to-noise ratio that can be accepted by the authorized receiver. is there.

  Preferably, the random number sequence generation unit serial-parallel converts the pseudo random number generation unit that generates a binary pseudo random number sequence based on predetermined key information, and the pseudo random number sequence generated by the pseudo random number generation unit, A serial / parallel converter that outputs a plurality of pseudo-random number sequences for modulation.

  In addition, the random number sequence generation unit is configured to generate a pseudo-random number sequence that generates a binary pseudo-random number sequence based on predetermined key information, and to convert the pseudo-random number sequence generated by the pseudo-random number generation unit from serial to parallel. Based on the speed switching signal, either the multiple serial-to-parallel converters that output the pseudo-random number sequence for modulation and the output destination of the pseudo-random number sequence generated by the pseudo-random number generator The configuration includes a first switch that switches to one side, and a second switch that selects and outputs a plurality of modulation pseudo-random number sequences output from a plurality of serial / parallel converters based on a speed switching signal. May be. However, the plurality of serial / parallel converters output different numbers of modulation pseudo-random number sequences.

  The present invention is also directed to a data receiving apparatus that receives information data encrypted using predetermined key information and performs secret communication with the transmitting apparatus. In order to achieve the above object, the data receiving apparatus of the present invention receives a multi-level code generation unit that generates a multi-level code sequence whose signal level changes substantially randomly from predetermined key information, and a transmission apparatus. A demodulator that demodulates the modulated signal using a predetermined demodulation method and outputs a multi-level signal having a plurality of levels corresponding to a combination of information data and a multi-level code sequence, and a multi-level based on the multi-level code sequence And an identification unit for identifying information data from the signal. Further, the multi-level code generation unit includes a random number sequence generation unit that generates a plurality of demodulation pseudo-random number sequences based on predetermined key information, and a plurality of bit sequences including at least some of the plurality of demodulation pseudo-random number sequences Is input as an input bit string, and includes a multi-value conversion unit that converts the input bit string into a multi-value code string. However, it is assumed that the number of input bit strings to the multi-value conversion unit is larger than the number of pseudo random sequences for demodulation generated by the random number sequence generation unit.

  Preferably, a fixed value is input to the multi-value conversion unit as the remaining bit string excluding the demodulated pseudo-random number sequence from the input bit sequence.

  In addition, a signal generated based on a predetermined rule may be input to the multi-level conversion unit as the remaining bit string excluding the demodulated pseudo-random number sequence from the input bit sequence. A signal generated based on a predetermined rule can be generated by delaying a part or all of a plurality of demodulated pseudo-random number sequences by a predetermined time.

  However, the ratio between the information amplitude corresponding to the amplitude of the information data and the fluctuation range of the multi-level signal corresponding to the bit string excluding the demodulated pseudo-random number sequence in the input bit sequence to the multi-level conversion unit is It is necessary to satisfy the condition that it is larger than an acceptable signal-to-noise ratio.

  Preferably, the random number sequence generation unit serial-parallel converts the pseudo random number generation unit that generates a binary pseudo random number sequence based on predetermined key information, and the pseudo random number sequence generated by the pseudo random number generation unit, A serial-parallel converter that outputs a plurality of demodulated pseudo-random number sequences.

  In addition, the random number sequence generation unit is configured to generate a pseudo-random number sequence that generates a binary pseudo-random number sequence based on predetermined key information, and to convert the pseudo-random number sequence generated by the pseudo-random number generation unit from serial to parallel. The multiple serial-to-parallel converters that output the demodulated pseudo-random number sequence and the output destination of the pseudo-random number sequence generated by the pseudo-random number generator are either the multiple serial-to-parallel converters based on the speed switching signal The configuration includes a first switch that switches to one side, and a second switch that selects and outputs a plurality of demodulation pseudo-random number sequences output from a plurality of serial / parallel converters based on a speed switching signal. May be. However, it is assumed that the plurality of serial / parallel conversion units output different numbers of pseudorandom numbers for demodulation.

  In addition, each processing procedure performed by the multi-level code generation unit, the multi-level processing unit, and the modulation unit included in the data transmission device described above can also be regarded as a data transmission method that provides a series of processing procedures. That is, in the data transmission method, based on predetermined key information, a multi-level code generation step for generating a multi-level code sequence whose signal level changes in a substantially random manner, a multi-level code sequence and information data are combined, The method includes a step of generating a multilevel signal having a plurality of levels corresponding to a combination of the multilevel code string and the information data, and a modulation step of performing a predetermined modulation process on the multilevel signal and outputting it as a modulation signal. Further, the multi-level code generation step includes a random number sequence generation step for generating a plurality of modulation pseudo-random number sequences based on predetermined key information, and a plurality of bit sequences including at least a part of the plurality of modulation pseudo-random number sequences Is input as an input bit string, and a multi-value conversion step of converting the input bit string into a multi-value code string. However, it is assumed that the number of input bit sequences is larger than the number of modulation pseudo random sequences.

  In addition, each processing procedure performed by the multilevel code generation unit, the demodulation unit, and the identification unit included in the above-described data reception apparatus can be regarded as a data reception method that provides a series of processing procedures. In other words, the data receiving method includes a multi-level code generation step for generating a multi-level code sequence whose signal level changes almost randomly from predetermined key information, and a modulated signal received from a transmitting device is demodulated by a predetermined demodulation method. A demodulation step of outputting as a multi-level signal having a plurality of levels corresponding to a combination of information data and a multi-level code sequence, and an identification step for identifying information data from the multi-level signal based on the multi-level code sequence Prepare. The multi-level code generation step includes a random number sequence generation step for generating a plurality of demodulation pseudo-random number sequences based on predetermined key information, and a plurality of bit sequences including at least a part of the plurality of demodulation pseudo-random number sequences Is input as an input bit string, and a multi-value conversion step of converting the input bit string into a multi-value code string. However, it is assumed that the number of input bit sequences is larger than the number of demodulated pseudo random sequences.

  The data communication device of the present invention encodes and modulates information data into a multilevel signal based on the key information, transmits the multilevel signal, and demodulates and encodes the received multilevel signal based on the same key information. By optimizing the signal-to-noise power ratio, an error is given to the ciphertext obtained by the eavesdropper. As a result, the eavesdropper needs to perform decryption processing in consideration of the possibility that the correct ciphertext is different from the one obtained by the eavesdropper. The amount of calculation increases, and safety against eavesdropping can be improved. Furthermore, by appropriately setting the signal point arrangement of the multilevel signal, it is possible to minimize the increase in the speed of the pseudo random number generator used inside the apparatus.

  These and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a block diagram showing an example of the configuration of a data communication apparatus according to the first embodiment of the present invention. In FIG. 1, the data communication apparatus according to the first embodiment of the present invention has a configuration in which a data transmission apparatus 1101 and a data reception apparatus 1201 are connected by a transmission line 110. The data transmission device 1101 includes a multi-level encoding unit 111 and a modulation unit 112. The multi-level encoding unit 111 includes a first multi-level code generation unit 111a and a multi-level processing unit 111b. The data reception device 1201 includes a demodulation unit 211 and a multilevel decoding unit 212. The multilevel decoding unit 212 includes a second multilevel code generation unit 212a and a multilevel identification unit 212b. The transmission line 110 can be a metal line such as a LAN cable or a coaxial cable, or an optical waveguide such as an optical fiber cable. The transmission path 110 is not limited to a wired cable such as a LAN cable, and may be a free space capable of propagating a radio signal.

  FIG. 2 is a schematic diagram for explaining a transmission signal waveform of the data communication apparatus according to the first embodiment of the present invention. FIG. 3 is a schematic diagram for explaining the names of transmission signal waveforms of the data communication apparatus according to the first embodiment of the present invention. FIG. 4 is a schematic diagram for explaining the transmission signal quality of the data communication apparatus according to the first embodiment of the present invention. The operation of the data communication apparatus according to the first embodiment of the present invention will be described below with reference to FIGS.

  The first multi-level code generator 111a generates a multi-level code string 12 (FIG. 2 (b)) whose signal level changes substantially randomly based on the predetermined first key information 11. The multilevel processing unit 111b receives the multilevel code string 12 (FIG. 2B) and the information data 10 (FIG. 2A). The multi-level processing unit 111b synthesizes the multi-level code sequence 12 and the information data 10 according to a predetermined procedure, and multi-level signal 13 (having a plurality of levels corresponding to the combination of the multi-level code sequence 12 and the information data 10). FIG. 2 (c)) is generated. For example, when the level of the multilevel code sequence 12 changes to C1 / C5 / C3 / C4 for the time slot t1 / t2 / t3 / t4, the multilevel processing unit 111b changes the level of the multilevel code sequence 12 to As the bias level, the information data 10 is added to the multi-level code sequence 12 to generate a multi-level signal 13 whose level changes to L1 / L8 / L6 / L4. The modulation unit 112 modulates the multilevel signal 13 in a predetermined modulation format, and sends the modulated signal 14 to the transmission line 110 as the modulation signal 14.

  Here, as shown in FIG. 3, the amplitude of the information data 10 is “information amplitude”, the total amplitude of the multilevel signal 13 is “multilevel signal amplitude”, and the level c1 / c2 / c3 / c4 of the multilevel code sequence 12 The levels (L1, L4) / (L2, L5) / (L3, L6) / (L4, L7) / (L5, L8) that can be taken by the multilevel signal 13 corresponding to / c5 The fifth “base”, the minimum signal point distance of the multilevel signal 13 is called “step width”.

  The demodulator 211 demodulates the modulated signal 14 transmitted via the transmission path 110 and reproduces the multilevel signal 15. The second multi-level code generation unit 212 a shares the second key information 16 that is the same as the first key information 11 in advance, and generates the multi-level code sequence 17 based on the second key information 16. . The multilevel identifying unit 212b identifies the multilevel signal 15 (binary determination) using the multilevel code string 17 as a threshold value, and reproduces the information data 18. Here, the modulation signal 14 in a predetermined modulation format transmitted and received by the modulation unit 112 and the demodulation unit 211 via the transmission path 110 is obtained by modulating an electromagnetic wave (electromagnetic field) or a light wave with the multilevel signal 13. Is.

  Note that, as described above, the multi-level processing unit 111b uses any method other than the method of generating the multi-level signal 13 by the addition process of the multi-level code string 12 and the information data 10 to generate the multi-level signal 13. It may be generated. For example, the multilevel processing unit 111 b may generate the multilevel signal 13 by amplitude-modulating the level of the multilevel code sequence 12 based on the information data 10. Alternatively, the multilevel processing unit 111b sequentially reads the levels of the multilevel signal 13 corresponding to the combination of the information data 10 and the multilevel code sequence 12 from a memory in which the levels of the multilevel signal 13 are stored in advance. A value signal 13 may be generated.

  2 and 3, the level of the multilevel signal 13 is expressed in eight stages, but the level of the multilevel signal 13 is not limited to this notation. Further, although the information amplitude is expressed as three times or an integer multiple of the step width of the multi-level signal 13, the information amplitude is not limited to this notation. The information amplitude may be any integer multiple of the step width of the multilevel signal 13 or may not be an integer multiple. Further, in FIGS. 2 and 3, each level of the multilevel code sequence 12 is arranged so as to be approximately the center of each level of the multilevel signal 13. However, each level of the multilevel code sequence 12 is limited to this arrangement. Is not to be done. For example, each level of the multilevel code string 12 may not be substantially the center of each level of the multilevel signal 13, or may match each level of the multilevel signal 13. In the above description, it is assumed that the multi-level code sequence 12 and the information data 10 have the same change rate and are in a synchronous relationship, but one change rate is faster than the other change rate ( (It may be low speed) or may be asynchronous.

  Next, the wiretapping operation of the modulated signal 14 by a third party will be described. A third party who is an eavesdropper uses the configuration in conformity with the data receiving device 1201 provided by an authorized receiver or a higher performance data receiving device (hereinafter, referred to as an eavesdropper data receiving device) to output the modulated signal 14. It is assumed that it will be deciphered. The eavesdropper data receiving apparatus reproduces the multilevel signal 15 by demodulating the modulated signal 14. However, since the eavesdropper data receiving apparatus does not share key information with the data transmitting apparatus 1101, unlike the data receiving apparatus 1201, the multilevel code string 17 cannot be generated from the key information. For this reason, the eavesdropper data receiving device cannot perform binary determination of the multilevel signal 15 with the multilevel code string 17 as a reference.

  As an eavesdropping operation that can be considered in such a case, there is a method of simultaneously identifying all levels of the multilevel signal 15 (generally called “brute force attack”). That is, the eavesdropper data receiving apparatus prepares threshold values for all signal points that can be taken by the multilevel signal 15, performs determination of the multilevel signal 15, and analyzes the determination result to obtain correct key information or information. Attempt to extract data. For example, the eavesdropper data receiving apparatus performs multilevel determination on the multilevel signal 15 with each level C0 / C1 / C2 / C3 / C4 / C5 / C6 of the multilevel code sequence 12 shown in FIG. Therefore, it tries to extract correct key information or information data.

  However, in an actual transmission system, noise is generated due to various factors, and this noise is superimposed on the modulation signal 14 so that the level of the multi-level signal 15 is temporally and instantaneously shown in FIG. fluctuate. In such a case, the SN ratio (signal-to-noise intensity ratio) of the determination target signal (multilevel signal 15) determined by the authorized receiver (data receiving apparatus 1201) is the difference between the information amplitude and the noise amount of the multilevel signal 15. It depends on the ratio. On the other hand, the SN ratio of the determination target signal (multilevel signal 15) determined by the eavesdropper data receiving apparatus is determined by the ratio between the step width of the multilevel signal 15 and the amount of noise.

  For this reason, when the noise level of the determined signal is the same, the eavesdropper data receiving device has a relatively smaller SN ratio than the data receiving device 1201, and transmission characteristics (error rate) ) Will deteriorate. That is, the data communication apparatus of the present invention can make eavesdropping difficult by using this characteristic to induce an identification error with respect to a brute force attack using all third-party thresholds. In particular, if the data communication apparatus sets the step width of the multilevel signal 15 to the same order or smaller than the noise amplitude (the spread of the noise intensity distribution), the multilevel determination by a third party is practically impossible. This makes it possible to prevent ideal eavesdropping.

  The noise superimposed on the signal to be judged (multi-level signal 15 or modulated signal 14) is a thermal noise (Gaussian property) possessed by a spatial field or electronic parts when electromagnetic waves such as radio signals are used for the modulated signal 14. When light waves are used, in addition to thermal noise, fluctuations in the number of photons (quantum noise) when photons are generated can be used. In particular, since a signal using quantum noise cannot be subjected to signal processing such as recording or duplication, the data communication apparatus sets the step width of the multilevel signal 15 based on the amount of noise. Therefore, it is impossible to eavesdrop on a third party, and the absolute safety of data communication can be ensured.

  As described above, according to the data communication apparatus according to the first embodiment of the present invention, when the information data to be transmitted is encoded as a multilevel signal, the distance between the signal points of the multilevel signal is determined with respect to the noise amount. To prevent eavesdropping by a third party. This provides a safer data communication device that gives decisive degradation to the received signal quality at the time of eavesdropping by a third party and makes it difficult for the third party to decode and decode the multilevel signal. be able to.

  As shown in FIG. 5, the multi-level encoding unit 111 converts each step width (S1 to S7) of the multi-level signal 13 into the fluctuation amount of each level, that is, the noise intensity distribution superimposed on each level. It may be varied accordingly. Specifically, the distance between the signal points is allocated so that the SN ratio determined between two adjacent signal points of the determination target signal input to the multi-level identifying unit 212b substantially matches. In addition, when the noise amount superimposed on each level is equal, each step width is set equally.

  In general, when a light intensity modulation signal using a semiconductor laser (LD) as a light source is assumed as the modulation signal 14 output from the modulation unit 112, the modulation depends on the level of the multilevel signal 13 input to the semiconductor laser. The fluctuation range (noise amount) of the signal 14 changes. This is because the semiconductor laser emits light based on the principle of stimulated emission using spontaneous emission light as “seed light”, and the amount of noise included in the modulation signal output from the semiconductor laser is the amount of induced emission light. It is defined by the relative ratio with the amount of spontaneous emission. That is, the higher the pumping rate of the semiconductor laser (the pumping rate of the semiconductor laser corresponds to the injected bias current), the smaller the amount of noise because the proportion of the amount of stimulated emission light increases. Conversely, the lower the pumping rate of the semiconductor laser, the greater the amount of spontaneous emission, and the greater the amount of noise. Therefore, as shown in FIG. 5, the multi-level encoding unit 111 sets the step width to be large in a region where the level of the multi-level signal is small, and to set the step width to be nonlinear in a region where the level of the multi-level signal is large. The signal-to-noise ratio between adjacent signal points of the signal to be judged can be made substantially uniform.

  Even when an optical modulation signal is used as the modulation signal 14, the SN ratio of the reception signal is mainly determined by shot noise under the condition that the noise due to the spontaneous emission light and the thermal noise used in the optical receiver are sufficiently small. Will be. Under such conditions, the amount of noise included in the multilevel signal increases as the level of the multilevel signal increases. Therefore, contrary to the case of FIG. 5, the multi-level encoding unit 111 sets a small step width in a region where the level of the multi-level signal is small and a large step width in a region where the level of the multi-level signal is large. Thus, the S / N ratio between adjacent signal points of the signal to be determined can be set substantially uniformly. By setting in this way, it is possible to uniformly give a decisive deterioration to the received signal quality at the time of eavesdropping by a third party, so that it becomes more difficult for the third party to decode and decode the multilevel signal. be able to.

(Second Embodiment)
The overall configuration of the data communication apparatus according to the second embodiment of the present invention is the same as that of the data communication apparatus shown in FIG. The data communication apparatus according to the second embodiment is different from the first embodiment only in the configurations of the first multi-level code generator 111a and the second embodiment 212a. FIG. 6 is a block diagram illustrating an example of a detailed configuration of the first multi-level code generator 111a according to the second embodiment of the present invention. In FIG. 6, the first multi-level code generation unit 111 a includes a first random number sequence generation unit 141 and a first multi-level conversion unit 142. The first random number sequence generation unit 141 includes a pseudo random number generation unit 1411 and a serial / parallel conversion unit 1412. Here, an example in which the number of bits of the multilevel code sequence 12 is 8 bits (m = 8) is shown.

The pseudo random number generation unit 1411 generates a binary pseudo random number sequence 31 based on the input first key information 11. The serial / parallel converter 1412 performs serial / parallel conversion on the pseudo random number sequence 31 and outputs first to eighth modulation pseudo random number sequences 32a to 32h. The first to eighth modulation pseudo-random number sequences 32 a to 32 h are input to the first multi-value conversion unit 142. The first modulation pseudo-random number sequence 32a is input to the multi-value processing unit 111b. The first multi-level conversion unit 142 converts the first to eighth modulation pseudo-random number sequences 32a to 32h into the multi-level code sequence 12 having 2 ^m multi-levels, and outputs the multi-level code sequence 12 to the multi-level processing unit 111b. To do.

  FIG. 7 is a block diagram showing an example of a detailed configuration of the second multi-level code generation unit 212a according to the second embodiment of the present invention. In FIG. 7, the configuration of the second multi-level code generator 212a is basically the same as that of the first multi-level code generator 111a. However, in the second multi-level code generation unit 212a, the outputs of the serial / parallel conversion unit 2412 are referred to as first to eighth demodulation pseudo-random number sequences 42a to 42h. The second multi-level code generation unit 212a outputs the multi-level code sequence 17 and the first demodulated pseudo-random number sequence 42a to the multi-level identification unit 212b.

  FIG. 8 is a diagram for explaining a signal format used in the data communication apparatus according to the second embodiment of the present invention. Referring to FIG. 8, the value of multilevel code sequence 12 used in the present embodiment is determined by first to eighth modulation pseudo-random number sequences 32a to 32h. The multilevel signal level is determined by the value of the multilevel code string 12 and the value of the information data 10. Further, the step width of the multilevel signal is set equal to or less than the noise level.

  The multi-value processing unit 111b alternately assigns adjacent multi-level signal levels to different values ("0" or "1") of the information data 10. For example, in the multilevel signal level included in the upper half shown in FIG. 8, the multilevel processing unit 111 b displays information data “0” when the multilevel code sequence 12 is odd, and the multilevel code sequence 12 is even. In this case, information data “1” is assigned. Further, the multi-level processing unit 111b, when the multi-level code sequence 12 included in the lower half shown in FIG. In the case of an even number, information data “0” is assigned. In other words, the multi-level processing unit 111b determines whether each level of the multi-level signal is associated with “0” or “1” according to the first modulation pseudo-random number corresponding to the least significant bit of the multi-level code sequence 12. Determined by the value in column 32a. In this way, it becomes impossible for an eavesdropper who does not have key information to directly identify data, and in order for an eavesdropper to eavesdrop, first, the key information of all multilevel signal levels is determined by multilevel determination. Forced to try to identify.

  On the other hand, in the data receiving apparatus, the identification level of the received multilevel signal is determined based on the values of the first to eighth demodulation pseudo-random number sequences 42a to 42h. The multi-level identifying unit 212b identifies the value of the information data based on the received multi-level signal level, the multi-level signal identification level, and the first demodulation pseudo-random number sequence 42a.

  Specifically, the multi-level identifying unit 212b “when the received multi-level signal level is higher than the identification level and the value of the first demodulated pseudo-random number sequence 42a is“ 0 ”” and “received When the multilevel signal level is smaller than the identification level and the value of the first demodulated pseudorandom number sequence 42a is “1”, the value of the information data is identified as “1”. On the contrary, the multi-level identifying unit 212b determines that “the received multi-level signal level is higher than the identification level and the value of the first demodulated pseudorandom number sequence 42a is“ 1 ”” and “the received multi-level When the signal level is lower than the identification level and the value of the first demodulating pseudo-random number sequence 42a is “0”, the value of the information data is identified as “0”.

  In the example of FIGS. 6 and 7, the case where the number of pseudo random number sequences for modulation is 8 has been described as an example, but the number of pseudo random number sequences for modulation is not limited to this and can be arbitrarily set.

  As described above, according to the present embodiment, when an eavesdropper attempts multilevel determination of a multilevel signal for specifying key information, the step width of the multilevel signal is set to be equal to or less than the noise level. Therefore, as in the first embodiment, a multilevel signal identification error occurs. For this reason, the data communication device according to the second embodiment provides safe data that decisively degrades the received signal quality at the time of eavesdropping by a third party and makes it difficult to decode and decode the data. A communication device can be provided.

(Third embodiment)
The data communication apparatus according to the second embodiment (see FIGS. 6 and 7) uses the values of the first to eighth modulation pseudo-random number sequences 32a to 32h and the multilevel code sequence 12 as bits of the information data 10. It needs to change at the same rate as the rate. At this time, the speed of the pseudo random number sequence 31 (that is, the random number generation speed of the pseudo random number generation unit 1411) is obtained by the product of the bit rate of the information data 10 and the number of bits of the multi-level code string 12. Therefore, the random number generation speed of the pseudo random number generation unit 1411 increases as the multi-level number of the multi-level code string 12 increases. On the other hand, since the reception SN ratio of the eavesdropper deteriorates as the multi-value number increases, the identification error given to the eavesdropper can be increased as the multi-value number increases. Therefore, from the viewpoint of safety, the larger the multi-value number, the higher the random number generation speed required for the pseudo random number generation unit 1411, and there is a problem that it becomes difficult to realize such a pseudo random number generation unit 1411. The present embodiment is for addressing such problems.

  The overall configuration of the data communication apparatus according to the third embodiment of the present invention is the same as that of the data communication apparatus shown in FIG. The data communication apparatus according to the third embodiment is different from the second embodiment only in the configuration of the first multi-level code generator 111a and the second embodiment 212a. Hereinafter, the same components as those of the second embodiment are denoted by the same reference numerals, and the description thereof is omitted. The data communication apparatus according to the third embodiment will be described focusing on the different components.

  FIG. 9 is a block diagram showing an example of a detailed configuration of the first multi-level code generator 111a according to the third embodiment of the present invention. In FIG. 9, the first multi-level code generation unit 111 a includes a first random number sequence generation unit 141 and a first multi-level conversion unit 142. The first random number sequence generation unit 141 includes a pseudo random number generation unit 1411 and a serial / parallel conversion unit 1412. Here, an example in which the number of bits of the multilevel code sequence 12 is 8 bits (m = 8) is shown.

In the first multilevel code generation unit 111a, the pseudorandom number generation unit 1411 generates a binary pseudorandom number sequence 31 based on the first key information 11 as in the second embodiment (see FIG. 6). Generate. The serial / parallel converter 1412 performs serial / parallel conversion on the pseudo-random number sequence 31 and outputs the first to fourth modulation pseudo-random number sequences 32a to 32d. Here, the number of pseudo-random number sequences for modulation output from the serial / parallel converter 1412 is set to be smaller than the number of bits in the bit sequence (that is, input bit sequence) input to the first multi-value converter 142. The first to fourth modulation pseudo-random number sequences 32a to 32d are input to the first multi-value conversion unit 142 as part of the input bit sequence. For example, as shown in FIG. 9, among the 8-bit input bit string, the modulation pseudo-random number sequences 32a and 32b are input to the lower 2 bits, and the modulation pseudo-random number sequences 32c and d are input to the upper 2 bits. Fixed values are input to the remaining input bit strings. The first multi-level conversion unit 142 converts the input bit string into the multi-level code string 12 having 2 ^m multi-levels, and outputs the multi-level code string 12 to the multi-level processing unit 111b.

  FIG. 10 is a block diagram showing an example of a detailed configuration of the second multi-level code generation unit 212a according to the third embodiment of the present invention. In FIG. 10, the second multi-level code generation unit 212 a includes a second random number sequence generation unit 241 and a second multi-level conversion unit 242. The second random number sequence generation unit 241 includes a pseudo random number generation unit 2411 and a serial / parallel conversion unit 2412.

  In the second multilevel code generator 212a, the pseudorandom number generator 2411 generates and outputs a binary pseudorandom number sequence 41 based on the input second key information 21. The serial / parallel converter 2412 performs serial / parallel conversion on the pseudo-random number sequence 41 and outputs the first to fourth demodulated pseudo-random number sequences 42a to 42d. Here, the number of pseudo-random numbers for demodulation output from the serial / parallel converter 2412 is made smaller than the number of bits of the bit string (that is, input bit string) input to the second multi-value converter 242. Part of the pseudorandom number for demodulation output from the serial / parallel converter 2412 is input to the second multilevel converter 242 as part of the input bit string.

For example, as shown in FIG. 10, the third and fourth demodulating pseudo-random number sequences 42c and 42d are input to the second multilevel conversion unit 242 as the upper bits of the input bit sequence. Here, the input bit string of the second multi-value conversion unit 242 to which the demodulation pseudo-random number sequence is input is an upper bit among the input bits of the first multi-value conversion unit 142 to which the modulation pseudo-random number sequence is input. It is desirable to be the same. Of the input bit string of the second multi-value conversion unit 242, a fixed value is input to the remaining bit string to which the demodulation pseudo-random number string is not input. The second multi-level conversion unit 242 converts the input bit string into a multi-level code string 22 having 2 ^m multi-levels and outputs it.

  FIG. 11 is a diagram for explaining a signal format used in the data communication apparatus according to the third embodiment of the present invention. Referring to FIG. 11, when 4 bits in the input bit string to first multi-level conversion unit 142 are fixed values, the number of levels that multi-level code string 12 can actually take is 16. Since the multilevel signal level is determined by the multilevel code string 12 and the value of the information data 10 (“0” or “1”), the number of levels that the multilevel signal 13 can take is 32. These levels are divided into eight groups of four levels each having a close value. The step width of the multilevel signal in each group is set equal to or less than the noise level. Furthermore, it is desirable that the difference between the highest level and the lowest level in each group is equal to or less than the noise level.

  Further, the multi-level processing unit 111b alternately allocates adjacent multi-level signal levels to different values ("0" or "1") of the information data 10 in each group. For example, in the multilevel signal level included in the upper half shown in FIG. 11, the multilevel processing unit 111 b displays information data “0” when the multilevel code sequence 12 is odd, and the multilevel code sequence 12 is even. In this case, information data “1” is assigned. Further, the multi-level processing unit 111b displays the information data “1” when the multi-level code sequence 12 is odd at the multi-level signal level included in the lower half shown in FIG. In the case of an even number, information data “0” is assigned. In other words, the multi-level processing unit 111b determines whether each level of the multi-level signal is associated with “0” or “1” according to the first modulation pseudo-random number corresponding to the least significant bit of the multi-level code sequence 12. Determined by the value in column 32a.

  On the other hand, in the data receiving apparatus, the identification level of the received multilevel signal is determined based on the values of the third and fourth demodulating pseudorandom numbers 42c and d. The data receiving apparatus may use the values of the first and second demodulation pseudo-random number sequences 42a and 42b when determining the identification level. However, since the corresponding fluctuations in the identification level are small, this is ignored. Even if the discrimination level is determined, the error rate after discrimination does not deteriorate greatly. The multi-level identifying unit 212b identifies the value of the information data based on the received multi-level signal level, the multi-level signal identification level, and the first demodulation pseudo-random number sequence 42a.

  Specifically, the multi-level identifying unit 212b “when the received multi-level signal level is higher than the identification level and the value of the first demodulated pseudo-random number sequence 42a is“ 0 ”” and “received When the multilevel signal level is smaller than the identification level and the value of the first demodulated pseudorandom number sequence 42a is “1”, the value of the information data is identified as “1”. On the contrary, the multi-level identifying unit 212b determines that “the received multi-level signal level is higher than the identification level and the value of the first demodulated pseudorandom number sequence 42a is“ 1 ”” and “the received multi-level When the signal level is lower than the identification level and the value of the first demodulating pseudo-random number sequence 42a is “0”, the value of the information data is identified as “0”.

  The random number generation speed of the pseudo random number generation unit 1411 required in the configuration of FIG. 9 is the bit rate of the information data 10 because the number of output bits (the number of modulation pseudo random number sequences) of the serial / parallel conversion unit 1412 is 4. Compared with the configuration of FIG. 6 (8 times the bit rate of the information data 10), the random number generation speed of the pseudo random number generation unit 1411 can be reduced to half.

Note that fluctuations in the multi-level signal level corresponding to the first and second demodulating pseudo-random number sequences 42a and 42b that are not used for generation of the identification level affect signal level deterioration, that is, SN ratio deterioration during identification. However, if the deteriorated S / N ratio is set so as to satisfy the required value of the data receiving apparatus 1201, the authorized receiver can identify the multilevel signal without error. That is, the ratio between the information amplitude and the fluctuation range of the multilevel signal corresponding to the lower bits of the demodulating pseudorandom number sequence is set so as to satisfy the condition that it is larger than the allowable SN ratio of the regular receiver. . The signal-to-noise ratio that can be accepted by a legitimate receiver is determined by the bit error rate of data that the legitimate receiver needs. For example, in optical communication, a value of 10 ⁻¹² or less is generally used as an allowable bit error rate. In this case, an allowable SN ratio is 23 dB or more.

  In the example of FIG. 9, the number of input bits of the first multi-value conversion unit 142 is 8 bits, the number of modulation pseudo-random number sequences is 4, and the modulation pseudo-random number sequence is the first multi-value conversion unit 142. Although an example in which the upper 2 bits and the lower 2 bits of the input bit string are input is shown, this is merely an example. The number of input bits of the first multi-value conversion unit 142 is arbitrary, and the number of the pseudo random number sequence for modulation and the pseudo random number sequence for demodulation depends on the ratio between the realizable random number generation speed and the required bit rate, It can be set arbitrarily. Also, the number of modulation pseudo random number sequences to be allocated to the upper bits and lower bits of the input bits of the first multi-value conversion unit 142 is always one of the modulation pseudo random number sequences input to the least significant bit of the input bit sequence. As long as even the condition of being satisfied is satisfied, it can be set arbitrarily.

  As described above, according to the present embodiment, when an eavesdropper attempts multilevel determination of a multilevel signal for specifying key information, the step width of the multilevel signal in the same group is equal to or less than the noise level. Since it is set, a multilevel signal identification error occurs as in the first embodiment. In addition, by appropriately setting the signal point arrangement of the multilevel signal, it is possible to improve safety while suppressing an increase in the random number generation speed required for the pseudo random number generator. For this reason, the data communication apparatus according to the third embodiment provides safe data that makes it difficult to decode and decode the received signal quality at the time of eavesdropping by a third party. A communication device can be provided.

(Fourth embodiment)
The overall configuration of the data communication apparatus according to the fourth embodiment of the present invention is the same as that of the data communication apparatus shown in FIG. The data communication apparatus according to the fourth embodiment is different from the third embodiment only in the configuration of the first multi-level code generator 111a. Hereinafter, the same components as those in the third embodiment are denoted by the same reference numerals, description thereof is omitted, and the data communication apparatus according to the fourth embodiment will be described focusing on different components.

  FIG. 12 is a block diagram showing an example of a detailed configuration of the first multi-level code generation unit 111a according to the fourth embodiment of the present invention. In FIG. 12, the first multi-level code generation unit 111a includes a first random number sequence generation unit 141, a first multi-level conversion unit 142, and a physical random number generation unit 143. The first random number sequence generation unit 141 includes a pseudo random number generation unit 1411 and a serial / parallel conversion unit 1412. Here, an example in which the number of bits of the multilevel code sequence 12 is 8 bits (m = 8) is shown. As in the second embodiment, the second multi-level code generation unit 212a in the present embodiment has the configuration shown in FIG.

Subsequently, the operation of the data communication apparatus according to the present embodiment will be described. The operations of the pseudo-random number generator 1411 and the serial / parallel converter 1412 are the same as those in the second embodiment. The physical random number generation unit 143 generates and outputs one or a plurality of physical random number sequences. In the example of FIG. 12, the physical random number generation unit 143 outputs the first to fourth physical random number sequences 33a to 33d. Here, the number of modulation pseudo-random number sequences 32a to 32d output from the serial / parallel conversion unit 1412 is made smaller than the number of bits of the input bit sequence of the first multi-value conversion unit 142. The first to fourth modulation pseudo-random number sequences 32a to 32d are input to the first multi-value conversion unit 142 as part of the input bit sequence. The first to fourth physical random number sequences 33a to 33d are input to the remaining input bit sequences. The first multi-level conversion unit 142 converts the input bit string into the multi-level code string 12 having 2 ^m multi-levels and outputs the multi-level code string 12.

  FIG. 13 is a diagram for explaining a signal format used in the data communication apparatus according to the fourth embodiment of the present invention. The signal format shown in FIG. 13 corresponds to the configuration of the first multi-level code generator 111a shown in FIG. Referring to FIG. 13, the first multi-level code generator 111a determines upper 2 bits and lower 2 bits of the 8 bits of the multi-level code sequence 12 by using the modulation pseudo-random number sequences 32a to 32d, The intermediate 4 bits are determined by the physical random number sequences 33a to 33d. Therefore, there are 16 levels of multilevel code sequences corresponding to the first to fourth modulation pseudo-random number sequences 32a to 32d. The step width of the multilevel signal is set equal to or less than the noise level. Also, adjacent multilevel signal levels are assigned to different information data values.

  On the other hand, in the data receiving apparatus, the identification level of the received multilevel signal is determined based on the values of the third and fourth demodulated pseudorandom number sequences 42c and d, as in the second embodiment. The multi-level identifying unit 212b identifies the value of the information data based on the received multi-level signal level, the multi-level signal identification level, and the first demodulated pseudo-random number sequence 42a.

  Specifically, the multi-level identifying unit 212b “when the received multi-level signal level is higher than the identification level and the value of the first demodulated pseudo-random number sequence 42a is“ 0 ”” and “received When the multilevel signal level is smaller than the identification level and the value of the first demodulated pseudorandom number sequence 42a is “1”, the value of the information data is identified as “1”. On the contrary, the multi-level identifying unit 212b determines that “the received multi-level signal level is higher than the identification level and the value of the first demodulated pseudorandom number sequence 42a is“ 1 ”” and “the received multi-level When the signal level is lower than the identification level and the value of the first demodulating pseudo-random number sequence 42a is “0”, the value of the information data is identified as “0”.

  Note that the fluctuation of the multi-level signal level corresponding to the first to fourth physical random number sequences that are not used for the generation of the identification level affects the deterioration of the signal level, that is, the SN ratio, during the identification. If the S / N ratio is set so as to satisfy the required value of the data receiving apparatus 1201, the authorized receiver can identify the multi-level signal without error. That is, the ratio between the information amplitude and the fluctuation range of the multilevel signal corresponding to the physical random number sequence needs to be set so as to satisfy the condition that it is larger than the SN ratio that can be accepted by the authorized receiver.

  By the way, as a configuration capable of obtaining the same effect as that of the first multi-level code generation unit 111a illustrated in FIG. 12, the configuration illustrated in FIG. FIG. 14A is a block diagram illustrating an example of another configuration of the first multi-level code generation unit 111a according to the fourth embodiment of the present invention. The functional blocks included in the configuration of FIG. 14A and the operations thereof are basically the same as those of FIG. 12, except that modulation pseudo-random number sequences 32a to 32c and physical random number sequences are used as input bit sequences of the first multi-value conversion unit 142. The difference is that not only 33a-b but also a bit string to which a fixed value is input exists. FIG. 15 shows a multilevel signal format in this configuration example. In this case, since 2 bits of the input bit string to the first multi-level conversion unit 142 are fixed values, the number of levels that the multi-level code string 12 can actually take is 64. Since the level of the multilevel signal corresponds to the multilevel code string 12 and the value of the information data 10 (“0” or “1”), the number of possible levels is 128. These levels are divided into eight groups of 16 levels each having a close value. The step width of the multilevel signal in each group is set equal to or less than the noise level. Further, in each group, adjacent multilevel signal levels are assigned to different information data values. On the other hand, the identification level is determined based on the values of the third and fourth demodulation pseudo-random number sequences 42c and d, as in the case of FIG.

  Further, as a configuration capable of obtaining the same effect as that of the first multi-level code generation unit 111a illustrated in FIG. 12, the configuration illustrated in FIG. 14B is also conceivable. FIG. 14B is a block diagram showing an example of another configuration of the first multi-level code generator 111a according to the fourth embodiment of the present invention. The functional blocks included in the configuration of FIG. 14B and the operations thereof are basically the same as those of FIG. 12, but a predetermined rule is used instead of the physical random number sequences 33a to 33d as the input bit sequence of the first multi-value conversion unit 142. The difference is that a signal generated based on is input. In the example shown in FIG. 14B, as a signal generated based on a predetermined rule, a signal generated by giving a predetermined delay time to the modulation pseudo-random number sequences 32 a to 32 c is sent to the first multi-value conversion unit 142. Have been entered.

  9 and 10, the number of input bits of the first multi-value conversion unit 142 is 8 bits, the number of the pseudo random number sequence for modulation and the pseudo random number sequence for demodulation is 4, and the pseudo random number sequence for modulation Has been shown as an example of being input to the upper and lower 2 bits of the input bit string of the first multi-value conversion unit 142, but this is merely an example. The number of input bits of the first multi-value conversion unit 142 is arbitrary, and the number of the pseudo random number sequence for modulation and the pseudo random number sequence for demodulation depends on the ratio between the realizable random number generation speed and the required bit rate, It can be set arbitrarily. The number of physical random number sequences can be arbitrarily set as long as it is equal to or smaller than the difference between the number of input bits of the first multi-value conversion unit 142 and the number of modulation pseudo-random number sequences. In addition, whether to input a modulation pseudo-random number sequence or physical random number sequence or a fixed value to each input bit sequence, the modulation pseudo-random number sequence is always input to the least significant bit of the input bit sequence. As long as even the condition of being satisfied is satisfied, it can be set arbitrarily.

  As described above, according to the present embodiment, since the number of multilevel signal levels that can be taken is larger than that in the third embodiment, a multilevel signal that may be erroneously identified in multilevel identification by an eavesdropper. The number of levels also increases, making wiretapping more difficult. In addition, as in the third embodiment, safety can be improved while suppressing an increase in the random number generation speed required for the pseudo random number generation unit. For this reason, the data communication apparatus according to the third embodiment provides safe data that makes it difficult to decode and decode the received signal quality at the time of eavesdropping by a third party. A communication device can be provided.

(Fifth embodiment)
The fifth embodiment of the present invention is for transmitting information data 10 at different bit rates while keeping the pseudorandom number generation speed constant. The overall configuration of the data communication apparatus according to the fifth embodiment of the present invention is the same as that of the data communication apparatus shown in FIG. The data communication apparatus according to the fifth embodiment is different from the third embodiment only in the configuration of the first random number sequence generator 141 and the second random number sequence generator 241. Hereinafter, the same components as those of the third embodiment are denoted by the same reference numerals and description thereof is omitted, and the data communication apparatus according to the fifth embodiment will be described focusing on the different components.

  FIG. 16 is a block diagram showing an example of a detailed configuration of the first random number sequence generation unit 141 according to the fifth embodiment of the present invention. In FIG. 16, the first random number sequence generator 141 includes a pseudo-random number generator 1411, a first switch 1413, a first serial / parallel converter 1414, a second serial / parallel converter 1415, A second switch 1416.

  Subsequently, the operation of the data communication apparatus according to the present embodiment will be described. The pseudorandom number generator 1411 generates a binary pseudorandom number sequence 31 based on the first key information 11 as in the second embodiment. The first switch 1413 sets the output destination of the pseudo random number sequence 31 to either the first serial / parallel converter 1414 or the second serial / parallel converter 1415 based on the input speed switching signal 36. Switch. The first serial / parallel converter 1414 performs serial / parallel conversion on the pseudo-random number sequence 31 and outputs it as first to eighth modulation pseudo-random number sequences 34a to 34h. The number of modulation pseudo-random number sequences output from the first serial / parallel converter 1414 is the same as the number of input bits of the first multi-value converter 142. The second serial / parallel converter 1415 serial / parallel converts the pseudo-random number sequence 31 and outputs the first to fourth modulation pseudo-random number sequences 35a to 35d. The number of modulation pseudo-random number sequences output from the second serial / parallel converter 1415 is set to be smaller than the number of input bits of the first multi-value converter 142.

  The second switch 1416 outputs the first to eighth modulation pseudo-random number sequences 34a to 34h output from the first serial / parallel converter 1414 and the second serial / parallel converter 1415. First to fourth modulation pseudo-random number sequences 35a to 35d are input. Based on the speed switching signal 36, the second switch 1416 inputs one of the first serial / parallel converter 1414 or the second serial / parallel converter 1415 to the first multi-value converter 142. Select whether to output. Here, a fixed value is input to the vacant bits, together with the first to fourth modulation pseudo-random number sequences 35a to 35d, to the second serial / parallel converter 1415. The configuration and operation of the second random number sequence generator 241 are the same as those of the first random number sequence generator 141 although not shown.

  When the first switch 1413 and the second switch 1416 are switched to the first serial / parallel converter 1414 side, the data communication apparatus according to the present embodiment performs the same operation as in the second embodiment. The bit rate at this time is 1/8 of the random number generation speed in the pseudo random number generation unit 1411. On the other hand, when the first switch 1413 and the second switch 1416 are switched to the second serial / parallel converter 1415 side, the data communication apparatus according to the present embodiment performs the same operation as that of the third embodiment. . The bit rate at this time is 1/4 of the random number generation speed in the pseudo random number generation unit 1411. In this way, by preparing a plurality of serial / parallel converters with different numbers of modulation pseudo-random number sequences to be output and switching them, it is possible to cope with different bit rates even if the pseudo-random number generation speed is the same. . That is, since the product of the number of modulation pseudo-random number sequences and the bit rate is the pseudo-random number generation speed, the bit rate can be made variable by switching the number of modulation pseudo-random number sequences. However, all the other constituent blocks not shown in FIG. 16 can handle all the bit rates that can be transmitted.

  Note that the configuration example in FIG. 16 is merely an example, and any configuration may be used as long as the bit rate can be switched by switching the number of modulation pseudo-random number sequences while keeping the pseudo-random number generation speed constant. Absent. Further, the value of the bit rate to be switched is not limited to two, and can be arbitrarily set as necessary.

  As described above, according to the present embodiment, it is possible to support a plurality of bit rates while keeping the random number generation speed of the pseudo random number generation unit constant.

  In addition, the data communication apparatus according to the first to fifth embodiments described above can be configured to combine the features of the embodiments. Each of the processes performed by the data transmission device, the data reception device, and the data communication device according to the first to fifth embodiments described above includes a data transmission method, a data reception method, and data communication that provide a series of processing procedures. It can also be understood as a method.

  In the data communication method, the data reception method, and the data communication method described above, predetermined program data stored in a storage device (ROM, RAM, hard disk, etc.) that can execute the processing procedure described above is interpreted and executed by the CPU. May be realized. In this case, the program data may be introduced into the storage device via the storage medium, or may be directly executed from the storage medium. Note that the storage medium refers to a semiconductor memory such as a ROM, a RAM, or a flash memory, a magnetic disk memory such as a flexible disk or a hard disk, an optical disk memory such as a CD-ROM, a DVD, or a BD, and a memory card. The storage medium is a concept including a communication medium such as a telephone line or a conveyance path.

  Although the present invention has been described in detail above, the above description is merely illustrative of the present invention in all respects and is not intended to limit the scope thereof. It goes without saying that various improvements and modifications can be made without departing from the scope of the present invention.

  The data communication device according to the present invention is useful as a secure secret communication device that does not receive eavesdropping and interception.

The block diagram which shows an example of a structure of the data communication apparatus which concerns on the 1st Embodiment of this invention. FIG. 4 is a schematic diagram for explaining a waveform of a transmission signal of the data communication apparatus according to the first embodiment of the present invention. FIG. 3 is a schematic diagram for explaining names of transmission signal waveforms of the data communication apparatus according to the first embodiment of the present invention. Schematic diagram illustrating transmission signal quality of the data communication apparatus according to the first embodiment of the present invention. Schematic diagram illustrating another transmission signal quality of the data communication apparatus according to the first embodiment of the present invention. The block diagram which shows an example of a detailed structure of the 1st multi-level code generation part 111a which concerns on the 2nd Embodiment of this invention. The block diagram which shows an example of a detailed structure of the 2nd multi-level code generation part 212a which concerns on the 2nd Embodiment of this invention. The figure explaining the signal format used with the data communication apparatus which concerns on the 2nd Embodiment of this invention. The block diagram which shows an example of a detailed structure of the 1st multi-level code generation part 111a which concerns on the 3rd Embodiment of this invention. The block diagram which shows an example of a detailed structure of the 2nd multi-level code generation part 212a which concerns on the 3rd Embodiment of this invention. The figure explaining the signal format used with the data communication apparatus which concerns on the 3rd Embodiment of this invention. The block diagram which shows an example of a detailed structure of the 1st multi-level code generation part 111a which concerns on the 4th Embodiment of this invention. The figure explaining the signal format used with the data communication apparatus which concerns on the 4th Embodiment of this invention. The block diagram which shows an example of the other structure of the 1st multi-level code generation part 111a which concerns on the 4th Embodiment of this invention. The block diagram which shows an example of the other structure of the 1st multi-level code generation part 111a which concerns on the 4th Embodiment of this invention. The figure explaining the other signal format used with the data communication apparatus which concerns on the 4th Embodiment of this invention. The block diagram which shows an example of a detailed structure of the 1st random number sequence generation part 141 which concerns on the 5th Embodiment of this invention. Block diagram showing the configuration of a conventional data communication device

Explanation of symbols

1101 Data transmission device 1201 Data reception device 110 Transmission path 111 Multi-level encoding unit 111a First multi-level code generation unit 111b Multi-level processing unit 112 Modulation unit 141 First random number sequence generation unit 1411 Pseudo random number generation units 1412 and 1414 , 1415 S / P converter 1413 1st switch 1415 2nd switch 142 1st multi-value converter 143 physical random number generator 211 demodulator 212 multi-level decoder 212a second multi-level code generator 212b multi Value identification unit 241 Second random number sequence generation unit 2411 Pseudo random number sequence generation unit 2412 S / P conversion unit 242 Second multi-value conversion unit 10, 18 Information data 11, 16, 91, 96, 99 Key information 12, 17 Multi-level code sequence 13, 15 Multi-level signal 14, 94 Modulated signal 31 Pseudo random sequence 32a-h, 34a-h, 35a-d Pseudo random number 33 for modulation ~d physical random number sequence 42a~h demodulation pseudo random number

Claims (20)

A data transmitting device that encrypts information data using predetermined key information and performs secret communication with a receiving device,
Based on the predetermined key information, a multi-level code generator for generating a multi-level code sequence whose signal level changes in a substantially random manner;
A multi-level processing unit that combines the multi-level code sequence and the information data, and generates a multi-level signal having a plurality of levels corresponding to a combination of the multi-level code sequence and the information data;
A modulation unit that performs predetermined modulation processing on the multilevel signal and outputs the modulated signal,
The multi-level code generator is
Based on the predetermined key information, a random number sequence generation unit that generates a plurality of modulation pseudo-random number sequences,
A plurality of bit sequences including at least a part of the plurality of modulation pseudo-random number sequences are input as an input bit sequence, and a multi-level conversion unit that converts the input bit sequence into the multi-level code sequence,
The data transmission apparatus according to claim 1, wherein the number of input bit strings to the multi-value conversion unit is larger than the number of modulation pseudo random sequences generated by the random number sequence generation unit.   The data transmission apparatus according to claim 1, wherein the multilevel processing unit assigns different values of information data to adjacent multilevel levels of the multilevel signal.   2. The data transmission device according to claim 1, wherein at least one of the plurality of modulation pseudo-random number sequences is input to the multilevel conversion unit as the least significant bit of the input bit sequence. The multi-level code generation unit further includes a physical random number generation unit that generates one or more physical random number sequences,
The one or more physical random number sequences are input to the multi-value conversion unit as the remaining bit sequences excluding the pseudo random number sequence for modulation from the input bit sequence. The data transmission device described.   The data transmission apparatus according to claim 1, wherein a fixed value is input to the multi-value conversion unit as a remaining bit string excluding the modulation pseudo-random number sequence from the input bit string. The multi-level code generation unit further includes a physical random number generation unit that generates one or more physical random number sequences,
The multi-value conversion unit receives the one or more physical random number sequences as a part of the input bits excluding the pseudo random number sequence for modulation, and receives a fixed value as the remaining bit sequence. The data transmission device according to claim 1, wherein:   The multi-level conversion unit receives a signal generated based on a predetermined rule as the remaining bit string excluding the pseudo random number sequence for modulation from the input bit sequence. The data transmission apparatus according to 1.   The signal generated based on the predetermined rule is generated by delaying a part or all of the plurality of modulation pseudo-random number sequences by a predetermined time. Data transmission device.   The ratio between the information amplitude corresponding to the amplitude of the information data and the fluctuation range of the multi-level signal corresponding to the physical random number sequence is larger than the signal-to-noise ratio that can be accepted by the authorized receiver. Item 5. The data transmission device according to Item 4. The random number sequence generator
A pseudo-random number generator that generates a binary pseudo-random number sequence based on the predetermined key information;
The serial-parallel conversion part which carries out the serial-parallel conversion of the pseudo-random number series produced | generated by the said pseudo-random number production | generation part, and outputs as said some pseudo-random number sequence for modulation | alteration, It is characterized by the above-mentioned. Data transmission device. The random number sequence generator
A pseudo-random number generator that generates a binary pseudo-random number sequence based on the predetermined key information;
A plurality of serial / parallel converters that serial-parallel convert the pseudo-random number sequence generated by the pseudo-random number generator and output as a plurality of pseudo-random numbers for modulation;
A first switch that switches an output destination of the pseudo-random number sequence generated by the pseudo-random number generator to one of the plurality of serial / parallel converters based on a speed switching signal;
A second switch for selecting and outputting a plurality of modulation pseudo-random number sequences output from the plurality of serial / parallel converters based on the speed switching signal;
The data transmitting apparatus according to claim 1, wherein the plurality of serial / parallel converters output different numbers of pseudo random numbers for modulation. A data receiving device that receives information data encrypted using predetermined key information and performs secret communication with a transmitting device,
A multi-level code generation unit that generates a multi-level code sequence in which the signal level changes in a substantially random manner from the predetermined key information;
A demodulator that demodulates the modulated signal received from the transmission device by a predetermined demodulation method, and outputs a demodulated signal having a plurality of levels corresponding to a combination of the information data and the multilevel code sequence;
An identification unit for identifying the information data from the multilevel signal based on the multilevel code sequence;
The multi-level code generator is
Based on the predetermined key information, a random number sequence generator that generates a plurality of demodulated pseudo-random number sequences,
A plurality of bit sequences including at least a part of the plurality of demodulating pseudo-random number sequences are input as an input bit sequence, and a multi-level conversion unit that converts the input bit sequence into the multi-level code sequence,
The data receiving apparatus according to claim 1, wherein the number of bit strings input to the multi-value conversion unit is larger than the number of demodulated pseudo random sequences generated by the random number sequence generation unit.   The data receiving apparatus according to claim 12, wherein a fixed value is input to the multi-level conversion unit as a remaining bit string excluding the demodulated pseudo-random number sequence from the input bit sequence.   The multi-level conversion unit is inputted with a signal generated based on a predetermined rule as the remaining bit string excluding the demodulated pseudo-random number sequence from the input bit sequence. 12. The data receiving device according to 12.   15. The signal generated based on the predetermined rule is generated by delaying a part or all of the plurality of demodulating pseudo-random number sequences by a predetermined time. Data receiving device.   The ratio between the information amplitude corresponding to the amplitude of the information data and the fluctuation range of the multi-level signal corresponding to the bit string excluding the pseudo random number sequence for demodulation from the input bit string to the multi-level conversion unit is 13. The data receiving device according to claim 12, wherein the data receiving device is larger than an allowable signal-to-noise ratio. The random number sequence generator
A pseudo-random number generator that generates a binary pseudo-random number sequence based on the predetermined key information;
The data according to claim 12, further comprising: a serial / parallel converter that serial-parallel converts the pseudo-random number sequence generated by the pseudo-random number generator and outputs the pseudo-random number sequence as a plurality of pseudo-random numbers for demodulation. Receiver device. The random number sequence generator
A pseudo-random number generator that generates a binary pseudo-random number sequence based on the predetermined key information;
A plurality of serial / parallel converters that serial-parallel convert the pseudo-random number sequence generated by the pseudo-random number generator and output as a plurality of demodulated pseudo-random numbers,
A first switch that switches an output destination of the pseudo-random number sequence generated in the pseudo-random number generation unit to one of the plurality of serial / parallel conversion units based on a speed switching signal;
A second switch for selecting and outputting a plurality of demodulated pseudo-random number sequences output from the plurality of serial / parallel converters based on the speed switching signal;
The data receiving apparatus according to claim 12, wherein the plurality of serial / parallel converters output different numbers of demodulated pseudo-random number sequences. A data transmission method for encrypting information data using predetermined key information and performing secret communication with a receiving device,
A multi-level code generation step for generating a multi-level code sequence in which the signal level changes substantially randomly based on the predetermined key information;
Combining the multilevel code sequence and the information data, and generating a multilevel signal having a plurality of levels corresponding to a combination of the multilevel code sequence and the information data;
A modulation step of performing a predetermined modulation process on the multi-level signal and outputting as a modulation signal,
The multi-level code generation step includes:
A random number sequence generating step for generating a plurality of modulation pseudo-random number sequences based on the predetermined key information;
A plurality of bit sequences including at least a part of the plurality of modulation pseudo-random number sequences as an input bit sequence, and a multi-value conversion step of converting the input bit sequence into the multi-value code sequence,
The data transmission method according to claim 1, wherein the number of the input bit sequences is larger than the number of the pseudo random sequences for modulation. A data reception method for receiving information data encrypted using predetermined key information and performing secret communication with a transmission device,
A multi-level code generation step of generating a multi-level code sequence in which the signal level changes substantially randomly from the predetermined key information;
A demodulating step of demodulating the modulated signal received from the transmitting device by a predetermined demodulation method, and outputting as a multi-level signal having a plurality of levels corresponding to a combination of the information data and the multi-level code sequence;
An identification step for identifying the information data from the multilevel signal based on the multilevel code sequence,
The multi-level code generation step includes:
Based on the predetermined key information, a random number sequence generating step for generating a plurality of demodulation pseudo-random number sequences,
A plurality of bit sequences including at least a part of the plurality of demodulating pseudo-random number sequences are input as an input bit sequence, and a multi-level conversion step of converting the input bit sequence into the multi-level code sequence,
The data receiving method according to claim 1, wherein the number of the input bit strings is larger than the number of the pseudo random sequences for demodulation.

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