JP2007215166A - Data transmitter and data receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a data communication apparatus which causes eavesdropper to take a significantly increased time to analyze a cipher text and provides high concealability. <P>SOLUTION: A multi-level code generation section 111a generates, based on predetermined key information 11, a multi-level code sequence 12 in which a signal level changes so as to be approximately random numbers. 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 to the information data 10. A modulator section 112 treats the multi-level signal by predetermined modulating processing and generates a modulated signal. The multi-level code generation section 111a generates the multi-level code sequence 12, based on a changed random number sequence which results from changing a bit series of a binary random number sequence generated based on the predetermined key information 11. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an apparatus that performs secret communication that prevents illegal eavesdropping and interception by a third party. More specifically, the present invention relates to an apparatus that performs data communication by selecting and setting a specific encoding / decoding (modulation / demodulation) scheme between authorized senders and receivers.

  Conventionally, in order to perform secret communication between specific persons, original information (key information) for encoding / decoding is shared between transmission / reception, and information data to be transmitted based on the original information ( A configuration for mathematically calculating / reversing the plaintext) is employed. FIG. 21 is a block diagram showing a configuration of a conventional data communication apparatus based on such a configuration. In FIG. 21, the conventional data communication device has a configuration in which a data transmission device 90001 and a data reception device 90002 are connected by a transmission line 913. The data transmission device 90001 includes an encoding unit 911 and a modulation unit 912. The data reception device 90002 includes a demodulation unit 914 and a decoding unit 915.

  The data transmission device 90001 and the data reception device 90002 share the same first key information 91 and second key information 96 in advance. Here, when the information data 90 and the first key information 91 are input to the encoding unit 911 and the second key information 96 is input to the decoding unit 915, the information data 98 is output from the decoding unit 915. Is done. Further, in order to explain an eavesdropping action by a third party, FIG. 21 includes an eavesdropper data receiving device 90003 including an eavesdropper demodulation unit 916 and an eavesdropper decryption unit 917. The eavesdropper decryption unit 917 receives third key information 99 different from the first key information 91 and the second key information 96. The operation of the conventional data communication apparatus will be described below with reference to FIG.

  In the data transmission device 90001, 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 encrypted by the encoding unit 911 into a modulation signal 94 in a predetermined modulation format and sends it to the transmission path 913. In the data receiving device 90002, the demodulating unit 914 demodulates the modulated signal 94 transmitted via the transmission path 913 by a predetermined demodulation method. Based on the second key information 96, the decryption unit 915 decrypts (decrypts) the signal demodulated by the demodulation unit 914 and outputs information data 98.

  Next, the operation of the eavesdropper data receiving apparatus 90003 when eavesdropping on the modulated signal 94 transmitted between the data transmitting apparatus 90001 and the data receiving apparatus 90002 will be described. In the eavesdropper data receiving device 90003, the eavesdropper demodulation unit 916 demodulates the modulation signal 94 propagating through the transmission path 913 by 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, since the eavesdropper decryption unit 917 attempts to decrypt the signal demodulated by the eavesdropper demodulation unit 916 based on the third key information 99 different from the first key information 91, the original information data 90 cannot be reproduced correctly. That is, since the eavesdropper decryption unit 917 does not share correct key information with the data transmission device 90001, the original information data 90 cannot be correctly reproduced.

  Such a mathematical encryption (or sometimes called a calculation encryption or software encryption) technique based on a mathematical operation can be applied to, for example, an access system described in Patent Document 1. Patent Document 1 discloses an access system having a PON (Passive Optical Network) configuration 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. Has been. In such an access system, an optical signal directed to another subscriber other than the desired optical signal is input to each optical receiver. Therefore, the optical transmitter encrypts the information data for each subscriber using different key information for each subscriber, thereby preventing leakage and eavesdropping of information data between subscribers, and secure data communication To realize.

Such mathematical cryptographic techniques are described in Non-Patent Document 1, Non-Patent Document 2, and the like.
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

  However, in a conventional data communication apparatus based on mathematical cryptography, an eavesdropper can consider all possible ciphertexts (modulated signals or encrypted information data) without sharing key information. In principle, cryptanalysis is possible by applying a brute force attack that performs operations using the key information of the combination or a special analysis algorithm. In particular, the processing speed of computers in recent years has improved remarkably, and if a computer based on a new principle such as a quantum computer is realized in the future, there is a possibility that the ciphertext can be easily wiretapped within a finite time. There was a problem.

  Therefore, an object of the present invention is to provide a highly confidential data communication device that significantly increases the time required for an eavesdropper to analyze a ciphertext.

  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, the data transmitting apparatus according to the present invention includes a multi-level code generation unit that generates a multi-level code sequence whose signal level changes substantially randomly based on predetermined key information, and a multi-level code generator. A multi-level processing unit that synthesizes the code sequence and the information data and generates a multi-level signal having a plurality of levels corresponding to the combination of the multi-level code sequence and the information data, and performs a predetermined modulation process on the multi-level signal. And a modulation unit for generating a modulation signal. The multi-level code generator generates a multi-level code sequence based on the changed random number sequence after changing the bit sequence of the binary random number sequence generated based on the predetermined key information.

  Preferably, the multi-level code generation unit generates a binary random number sequence that is a pseudo random number sequence from predetermined key information, and a predetermined bit sequence from the binary random number sequence generated by the random number sequence generation unit. A bit selection unit that selects and outputs the selected bit sequence as a post-change random number sequence, and a multi-value conversion unit that converts the post-change random number sequence into a multi-level code sequence.

  Preferably, the multilevel code generator further includes a random number generator that generates a predetermined pseudo-random number sequence. In such a case, the bit selection unit changes the bit sequence selected from the binary random number sequence generated by the random number sequence generation unit, based on the pseudo random number sequence generated by the random number generation unit.

  The multi-level code generation unit generates a binary random number sequence that is a pseudo-random number sequence from predetermined key information, and a predetermined random number that is fixed in advance from the binary random number sequence generated by the random number sequence generation unit. The remaining bit sequence from which the bit sequence is removed may be a changed random number sequence, and a multi-value conversion unit that converts the changed random number sequence into a multi-value code sequence may be used.

  The multi-level code generation unit generates a binary random number sequence that is a pseudo-random number sequence from predetermined key information, and converts the binary random number sequence generated by the random number sequence generation unit into a multi-level code sequence The structure provided with the multi-value conversion part to perform may be sufficient. In such a case, the multi-value conversion unit operates asynchronously with the random number sequence generation unit, thereby handling the binary random number sequence generated by the random number sequence generation unit as a post-change random number sequence.

  The multi-level code generation unit is a bit sequence in which a random number sequence generation unit that generates a binary random number sequence that is a pseudo-random number sequence from predetermined key information and a permutation of the binary random number sequence generated by the random number sequence generation unit are replaced. May be configured to include a bit replacement unit that outputs a random number sequence after change and a multilevel conversion unit that converts the random number sequence after change into a multilevel code sequence.

  Preferably, the multilevel code generator further includes a random number generator that generates a predetermined pseudo-random number sequence. In such a case, the bit replacement unit determines a rule for replacing the binary random number sequence generated by the random number sequence generation unit based on the pseudo random number sequence generated by the random number generation unit.

  Further, the multi-level code generation unit includes a random number sequence generation unit that generates a binary random number sequence that is a pseudo-random number sequence from predetermined key information, a memory unit that stores the binary random number sequence generated by the random number sequence generation unit, A configuration including a multi-value conversion unit that converts a binary random number sequence read from the memory unit into a multi-value code sequence may be used. In such a case, the multi-value conversion unit treats the binary random number sequence generated by the random number sequence generation unit as the changed random number sequence by changing the read address of the memory unit.

  Preferably, the random number sequence generation unit is configured by a linear feedback shift register including a plurality of shift registers and an exclusive OR element. The multi-level conversion unit includes a plurality of latches and a D / A conversion unit that converts a bit sequence output from the plurality of latches into a multi-level code string.

  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 in which the signal level changes from a predetermined key information in a substantially random manner, and received from the transmitting apparatus. A demodulator that demodulates the modulated signal by a predetermined demodulation method and outputs it as a multilevel signal having a plurality of levels corresponding to a combination of information data and a multilevel code sequence, and a multilevel signal based on the multilevel code sequence And an identification unit for identifying information data. The multi-level code generator generates a multi-level code sequence based on the changed random number sequence after changing the bit sequence of the binary random number sequence generated based on the predetermined key information.

  Each processing procedure performed by the data transmission device described above can also be regarded as a data transmission method for encrypting information data using predetermined key information and performing secret communication with the reception device. That is, 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, A multi-level code comprising: a multi-level processing step for generating a multi-level signal having a plurality of levels corresponding to a combination with information data; and a modulation step for performing a predetermined modulation process on the multi-level signal to generate a modulation signal. The generation step is a method of generating a multi-level code sequence based on the changed random number sequence after changing the bit sequence of the binary random number sequence generated based on predetermined key information.

  In addition, each processing procedure performed by the above-described data receiving apparatus can be regarded as a data receiving method for receiving information data encrypted using predetermined key information and performing secret communication with the transmitting apparatus. it can. That is, a multi-level code generation step for generating a multi-level code sequence in which the signal level changes from a predetermined key information in a substantially random manner, and a modulated signal received from the transmission device is demodulated by a predetermined demodulation method, and the information data and the multi-level code sequence are demodulated. A demodulation step for outputting as a multilevel signal having a plurality of levels corresponding to a combination with a value code string, and an identification step for identifying information data from the multilevel signal based on the multilevel code string, The generation step is a method of generating a multi-level code sequence based on the changed random number sequence after changing the bit sequence of the binary random number sequence generated based on predetermined key information.

  According to the data transmitting apparatus 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 appropriately set with respect to the amount of noise included in the received signal. By doing so, it is possible to give decisive degradation to the received signal quality at the time of eavesdropping by a third party, making it difficult for the third party to decode and decode the multilevel signal. In addition, even when a ciphertext is acquired by a third party, it is possible to easily provide a safer data communication device by generating a multi-value key so that the key information is not easily estimated. . In addition, the data receiving apparatus includes the same multilevel code generation unit as that of the data transmitting apparatus, so that information data can be acquired from the modulated signal received from the data transmitting 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.

(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 has a configuration in which a data transmission apparatus 10101 and a data reception apparatus 10201 are connected by a transmission path 110. The data transmission apparatus 10101 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 10201 includes a demodulation unit 211 and a multi-level decoding unit 212. The multi-level decoding unit 212 includes a second multi-level code generation unit 212a and a multi-level 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 multi-level processing unit 111b receives the multi-level code sequence 12 (FIG. 2B) and the information data 10 (FIG. 2A), synthesizes both signals according to a predetermined procedure, and multi-level code sequence 12 And a multilevel signal 13 (FIG. 2C) having a plurality of levels corresponding to the combination of the information data 10 and the information data 10. 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 biases the multilevel code sequence 12 By adding the information data 10 as a level, a multilevel signal 13 whose level changes to L1 / L8 / L6 / L4 is generated.

  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 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. 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 in advance the second key information 16 that is the same as the first key information 11, and corresponds to the multi-level code sequence 12 based on the second key information 16. A multi-level code sequence 17 is generated. 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 a signal obtained by modulating an electromagnetic wave (electromagnetic field) or a light wave with the multilevel signal 13. It is.

  As described above, the multi-level processing unit 111b generates the multi-level signal 13 using any method other than generating the multi-level signal 13 by the addition process of the multi-level code string 12 and the information data 10. It may be. For example, the multi-level processing unit 111 b may generate the multi-level signal 13 by amplitude-modulating the level of the multi-level 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. However, 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 multilevel 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 this regard, in FIGS. 2 and 3, each level (each bias level) of the multi-level code sequence 12 is arranged so as to be approximately the center between the levels of the multi-level signal 13. Each level of the code string 12 is not limited to this arrangement. For example, each level of the multilevel code string 12 may not be substantially the center between the levels of the multilevel signal 13, or may correspond to 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 may be asynchronous, and one change rate is the other. It may be faster (or slower) than the change rate.

  Next, an eavesdropping operation by a third party will be described. A third party who is an eavesdropper decodes the modulated signal 14 using a configuration in accordance with the data receiving device 10201 provided by the legitimate receiver, or using a more advanced data receiving device (that is, an eavesdropper data receiving device). It is assumed that 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 10101, the multilevel code string 17 cannot be generated from the key information unlike the data receiving apparatus 10201. 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 conceivable in such a case, there is a method of identifying the multilevel signal 15 based on threshold values corresponding to all levels of the multilevel signal 15 and identifying the level of the multilevel signal 15. That is, the eavesdropper data receiving apparatus prepares thresholds corresponding to all signal points that can be taken by the multilevel signal 15, performs simultaneous determination of the multilevel signal 15, and analyzes the determination result to obtain the correct key. Attempt to extract information or information data. For example, the eavesdropper data receiving apparatus performs multi-level determination of the multi-level signal 15 using all levels c0 / c1 / c2 / c3 / c4 / c5 / c6 of the multi-level 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 signal to be determined (multilevel signal 15) determined by the authorized receiver (that is, the data reception device 10201) is 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 included in the signal to be determined is the same, the eavesdropper data receiving device has a relatively smaller SN ratio of the signal to be determined than the regular data receiving device, 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 against a decryption attack using all thresholds by a third party. 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 determined (multi-level signal 15 or modulation signal 14) is thermal noise generated by a space field, electronic parts, etc. when an electromagnetic wave such as a radio signal is used as the modulation signal 14. When (Gaussian noise) is used, in addition to thermal noise, photon number fluctuation (quantum noise) generated when a photon is generated or detected can be used. In particular, since signal processing such as recording or duplication cannot be applied to a signal accompanied by quantum noise, setting the step width of the multi-level signal 15 on the basis of the amount of quantum noise enables wiretapping by a third party. As impossible, the absolute safety of data communication can be ensured.

  As described above, according to the first embodiment of the present invention, when the information data 10 to be transmitted is encoded as the multi-level signal 13, the distance between the signal points of the multi-level signal 13 is determined as the received signal. By appropriately setting the amount of noise included in the signal, the third party decrypts / decodes the multi-level signal 13 by giving a decisive deterioration to the received signal quality at the time of eavesdropping by the third party. A difficult and safe data communication device can be provided.

(Second Embodiment)
FIG. 5 is a block diagram showing an example of the configuration of the data communication apparatus according to the second embodiment of the present invention. In FIG. 5, the data communication apparatus according to the second embodiment of the present invention is different from the data communication apparatus according to the first embodiment (FIG. 1) in that the data transmission apparatus 10102 includes the first data inversion unit 113. Except that the data receiving device 10202 further includes a second data inverting unit 213. The data communication apparatus according to the second embodiment will be described below. Since the configuration of the present embodiment conforms to that of the first embodiment (FIG. 1), the same reference numerals are assigned to blocks performing the same operations as those of the first embodiment, and the description thereof is omitted. To do.

  The first data inverting unit 113 does not fix the correspondence between “0/1” and “Low / High” included in the information data 10 illustrated in FIG. Change almost randomly. For example, the first data reversing unit 113 performs an exclusive OR of a random number sequence (pseudo-random number sequence) generated based on an initial key shared with the second data determination unit 213 and the information data 10 (Exclusive OR). The calculation result is output to the multi-level encoding unit 111. The second data inverting unit 213 uses the reverse procedure of the first data inverting unit 113 for the data output from the multi-level decoding unit 212, and the correspondence relationship between “0/1” and “Low / High”. To change. For example, the second data inversion unit 213 performs an exclusive OR operation between the random number sequence generated based on the initial key shared with the first data inversion unit 113 and the data output from the multi-level decoding unit 212. The calculation result is reproduced as information data 18.

  As described above, according to the second embodiment of the present invention, the complexity of the multi-level signal 13 as encryption can be increased by inverting the information data 10 to be transmitted substantially randomly. This makes it more difficult for a third party to decode / decode the multilevel signal 13 and provide a safer data communication apparatus.

(Third embodiment)
FIG. 6 is a block diagram showing an example of the configuration of a data communication apparatus according to the third embodiment of the present invention. In FIG. 6, in the data communication apparatus according to the third embodiment of the present invention, the data transmission apparatus 10103 further includes a noise control unit 114 as compared with the data communication apparatus according to the first embodiment (FIG. 1). . The noise control unit 114 includes a noise generation unit 114a and a synthesis unit 114b. The data communication apparatus according to the third embodiment of the present invention will be described below. Since the configuration of this embodiment conforms to that of the first embodiment (FIG. 1), the same reference numerals are assigned to blocks performing the same operations as those of the first embodiment, and the description thereof is omitted. .

  In FIG. 6, the noise generator 114 a generates a predetermined noise 21. The synthesizer 114 b synthesizes the noise generated by the noise generator 114 a with the multilevel signal 13, and outputs the multilevel signal 22 with the synthesized noise to the modulator 112. That is, the noise control unit 114 intentionally causes the level fluctuation of the multilevel signal 13 described with reference to FIG. 4 by synthesizing noise, and controls the SN ratio of the multilevel signal 13 to an arbitrary value. ing. Note that thermal noise, quantum noise, or the like is used as the noise generated by the noise generator 114a. In addition, the multilevel signal 22 in which noise is synthesized (superimposed) is referred to as a noise superimposed multilevel signal 22.

  As described above, according to the third embodiment of the present invention, when the information data 10 to be transmitted is encoded as the multilevel signal 13, the SN ratio of the multilevel signal 13 is appropriately controlled. Thus, the received signal quality at the time of eavesdropping by a third party is given decisive degradation, making it difficult for the third party to decode and decode the multilevel signal 13, and to provide a safer data communication apparatus. be able to.

(Fourth embodiment)
FIG. 7 is a diagram illustrating an example of a multilevel signal format used in the data communication apparatus according to the fourth embodiment of the present invention. Since the configuration of the data communication apparatus according to the fourth embodiment of the present invention is the same as that of the first to third embodiments, FIG. 1, FIG. 5 or FIG. 6 is used. The operation of the data communication apparatus according to the fourth embodiment of the present invention will be described below using FIG.

  Referring to FIG. 1, FIG. 5, or FIG. 6, as shown in FIG. 7, the multi-level encoding unit 111 converts each step width (S 1 to S 7) of the multi-level signal 13 to the variation amount ( That is, it is set according to the noise intensity distribution superimposed on each level. Specifically, the multi-level encoding unit 111 makes the SN ratio between two adjacent signal points of the determination target signal (that is, the multi-level signal 15) input to the multi-level identification unit 212b substantially uniform. The distance between the signal points is allocated. For this reason, when the amount of noise superimposed on each level of the multilevel signal 15 is equal, the multilevel encoding unit 111 sets the step widths 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 signal depends on the level of the multilevel signal 13 input to the LD. The fluctuation range (noise amount) of 14 changes. This is due to the fact that LD emits light based on the principle of stimulated emission with spontaneous emission as “seed light”, and the amount of noise is defined by the relative ratio of the amount of spontaneous emission to the amount of induced emission. Yes. Here, the higher the excitation rate (corresponding to the bias current injected into the LD), the greater the ratio of the amount of stimulated emission light, so the amount of noise decreases. Conversely, the lower the excitation rate, the smaller the ratio of spontaneous emission light amount. Since it increases, the amount of noise increases. Therefore, as shown in FIG. 7, the multi-level encoding unit 111 sets the step width large in the region where the level of the multi-level signal 13 is small, and small in the region where the level of the multi-level signal 13 is large. That is, by setting the step width of the multilevel signal 13 to be non-linear, the SN ratio between adjacent signal points of the signal to be determined is set to be substantially uniform.

  Even when an optical modulation signal is used as the modulation signal 14, the S / N 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 for the optical receiver are sufficiently small. Will be. Under such conditions, the amount of noise included in the multilevel signal 15 increases as the level of the multilevel signal 13 increases. Therefore, contrary to the case of FIG. 7, the multilevel encoding unit 111 sets a small step width in a region where the level of the multilevel signal 13 is small and a large step width in a region where the level of the multilevel signal 13 is large. By doing so, the signal-to-noise ratio between adjacent signal points of the signal to be determined is set to be substantially uniform.

  As described above, according to the fourth embodiment of the present invention, when the information data 10 to be transmitted is encoded as the multi-level signal 13, the SN ratio between adjacent signal points of the signal to be determined is substantially equal. The distance between signal points of the multilevel signal 13 is set so as to be uniform. As a result, the quality of the received signal at the time of eavesdropping by a third party is decisively deteriorated, making it more difficult for a third party to decode and decode the multilevel signal 13 and providing a safer data communication device. can do.

(Fifth embodiment)
FIG. 8 is a block diagram showing an example of the configuration of the data communication apparatus according to the fifth embodiment of the present invention. In FIG. 8, the data communication apparatus according to the fifth embodiment of the present invention has a configuration in which a data transmission apparatus 25105 and a data reception apparatus 25205 are connected by a transmission line 110. Compared with the data communication devices according to the first to fourth embodiments described above, the data communication device according to the fifth embodiment includes a first multi-level code generation unit 111a and a second multi-level code generation unit. The configuration of 212a is characteristic. The first multilevel code generation unit 111 a includes a first random number sequence generation unit 171 and a first multilevel conversion unit 17. The second multi-level code generation unit 212a includes a second random number sequence generation unit 271 and a second multi-level conversion unit 272.

  The first random number sequence generation unit 171 generates a predetermined pseudo random number sequence using the first key information 11 as an initial value. The first multi-value conversion unit 172 extracts a bit sequence of p bits (p is an arbitrary integer) from the pseudo-random number sequence generated by the first random number sequence generation unit 171 and sets a level corresponding to the extracted bit sequence. The multi-value code string 12 is converted. Similarly, the second random number sequence generation unit 271 generates a pseudo random number sequence corresponding to the pseudo random number sequence output from the first random number sequence generation unit 171 using the second key information 16 as an initial value. The second multilevel conversion unit 272 extracts a bit sequence of p bits (p is an arbitrary integer) from the pseudo random number sequence, and converts it into a multilevel code sequence 17 having a level corresponding to the extracted bit sequence.

  FIG. 9 is a schematic diagram illustrating an example of a detailed configuration of the first multi-level code generation unit 111a according to the fifth embodiment of the present invention. Details of the first multi-level code generator 111a according to the fifth embodiment of the present invention will be described below with reference to FIG. However, the second multi-level code generation unit 212a has the same configuration as that of the first multi-level code generation unit 111a shown in FIG.

  In FIG. 9, the first multilevel code generation unit 111 a further includes a timing signal generation unit 173 in addition to a first random number sequence generation unit 171 and a first multilevel conversion unit 172. The timing signal generator 173 generates an initial value setting signal S21 and a read signal S22 using the externally supplied clock signal S20 as a reference timing. The first random number sequence generation unit 171 includes, for example, a linear feedback shift register including six shift registers 171a to 171f and one exclusive OR element 171g. In this example, the first random number sequence generation unit 171 includes the same number of shift registers 171 a to 171 f as the number of bits of the first key information 11. The first random number sequence generation unit 171 uses the input of the initial value setting signal S21 as a trigger to set the 6 bits (a0 to a5) constituting the first key information 11 in the corresponding shift registers 171a to 171f, A binary random number sequence is generated using the clock signal S20 as a reference timing.

The first multi-value conversion unit 172 includes, for example, six latches 172a to 172f and a D / A (digital / analog) conversion unit 172g. The first multi-value conversion unit 172 uses the input of the read signal S22 as a trigger to generate a bit of p = 6 bits from the binary random number sequence output from the first random number sequence generation unit 171 by the six latches 172a to 172f. The sequence is extracted, and the extracted bit sequence is converted into the multi-level code sequence 12 by the D / A conversion unit 172g. In FIG. 9, the shift registers 171a to 171f hold and output data D1 to D6, and the latches 172a to 172f hold and output data d1 to d6. As a method for converting such a bit sequence into the multi-level code sequence 12, for example, a 6-bit bit sequence (d1 to d6) is converted from binary to decimal, and a level (total level) corresponding to (Equation 1) is converted. There is a method of converting into a multi-level code sequence 12 having the number: 2 ⁶ ). The random number generation method / principle using the linear feedback shift register configuration is described in detail in Non-Patent Document 2 and the like, and thus the description thereof is omitted.
d6 × 2 ⁵ + d5 × 2 ⁴ + d4 × 2 ³ + d3 × 2 ² + d2 × 2 ¹ + d1 (Formula 1)

  In FIG. 9, the configuration of a linear feedback shift register having six shift registers is shown as the first random number sequence generation unit 171; however, the number of shift registers is not limited to this. Further, the first random number sequence generation unit 171 may have any configuration other than the linear feedback shift register as long as it can generate a binary random number sequence from the first key information 11. Further, the first multi-value conversion unit 172 includes six latches, but the number of latches is not limited to this. Further, the first multi-level conversion unit 172 may have any configuration other than the D / A conversion unit 172g as long as it can convert the binary bit sequence output from the latch into the multi-level code sequence 12. Absent.

  As described above, according to the fifth embodiment of the present invention, the first multi-level code generator 111a and the second multi-level code generator 212a have a simple configuration, and the multi-level code strings 12, 17 Can be generated. Thereby, the data communication apparatus according to the fifth embodiment of the present invention can obtain the same effects as the data communication apparatuses according to the first to fourth embodiments.

(Sixth embodiment)
FIG. 10 is a block diagram showing an example of the configuration of the data communication apparatus according to the sixth embodiment of the present invention. In FIG. 10, the data communication apparatus according to the sixth embodiment of the present invention has a configuration in which a data transmission apparatus 25106 and a data reception apparatus 25206 are connected by a transmission line 110. Compared with the data communication apparatus according to the fifth embodiment described above, the data communication apparatus according to the sixth embodiment includes the first multilevel code generation unit 111a and the second multilevel code generation unit 212a. The configuration is different. The first multi-level code generation unit 111a includes a first random number sequence generation unit 171, a first bit selection unit 174, and a first multi-level conversion unit 172. The second multi-level code generation unit 212a includes a second random number sequence generation unit 271, a second bit selection unit 274, and a second multi-level conversion unit 272.

  The first random number sequence generation unit 171 generates a predetermined pseudo random number sequence using the first key information 11 as an initial value. The first bit selection unit 174 extracts a p-bit (p is an arbitrary integer) bit sequence from the pseudo-random number sequence generated by the first random number sequence generation unit 171, and q bits (q is A bit sequence of any integer less than or equal to p) is selected and output. The first multi-level conversion unit 172 converts the q-bit bit sequence output from the first bit selection unit 174 into a multi-level code sequence 12 having a level corresponding to the bit sequence. That is, the first multi-level code generation unit 111a uses the multi-level code sequence based on the changed random number sequence after the bit sequence of the binary random number sequence generated based on the first key information 11 is changed. 12 is generated.

  Similarly, the second random number sequence generation unit 271 generates a pseudo random number sequence corresponding to the pseudo random number sequence output from the first random number sequence generation unit 171 using the second key information 16 as an initial value. The second bit selection unit 274 extracts a bit sequence of p bits (p is an arbitrary integer) from the pseudo random number sequence generated by the second random number sequence generation unit 271, and q bits ( q is an arbitrary integer less than or equal to p) and outputs it. The second multi-level conversion unit 272 converts the q-bit bit sequence output from the second bit selection unit 274 into a multi-level code sequence 17 having a level corresponding to the bit sequence. That is, the second multi-level code generator 212a uses the multi-level code sequence based on the changed random number sequence after the bit sequence of the binary random number sequence generated based on the second key information 16 is changed. 12 is generated.

  FIG. 11 is a schematic diagram illustrating an example of a detailed configuration of the first multi-level code generation unit 111a according to the sixth embodiment of the present invention. In FIG. 11, as in FIG. 9, the shift registers 171a to 171f output / hold data D1 to D6, and the latches 172a to 172e output / hold data d1 to d5. Represents. FIG. 12A is a schematic diagram for explaining a third party's wiretapping act on the data communication apparatus according to the sixth embodiment of the present invention. FIG. 12B is a schematic diagram for explaining the effect of the data communication apparatus according to the sixth embodiment of the present invention. Hereinafter, a data communication apparatus according to the sixth embodiment of the present invention will be described in detail with reference to FIGS. 11, 12A, and 12B. However, the second multi-level code generation unit 212a has the same configuration as the first multi-level code generation unit 111a shown in FIG.

  First, an eavesdropping operation by a third party will be described. It is assumed that a third party who is an eavesdropper receives and decodes the modulated signal 14 using a configuration according to a data receiving device provided by a legitimate receiver or a higher performance data receiving device. As one of the basic methods of eavesdropping, information data 10 to be transmitted by the sender is set to known data (for example, all “0”, all “1”, etc.) in advance by some means. There is a “known plaintext attack” in which a ciphertext (multilevel code string 12) is directly obtained by acquiring ciphertext (multilevel signal 13 or modulated signal 14) obtained at that time. In response to such an attack, as described above, the data communication apparatus of the present invention can obtain the encryption key accurately by a third party by using, for example, quantum noise generated when an optical signal is detected. Can be disturbed.

  However, in the unlikely event that the quantum noise is not large enough, an encryption key is obtained by a third party, and as a result, the ciphertext may be easily decrypted. Such wiretapping operation by a third party will be described with reference to FIG. 12A. However, the first multi-level code generator 111a used in the description of FIG. 12A has a configuration according to the first multi-level code generator 111a (see FIG. 9) shown in the fifth embodiment. And In the following description, it is assumed that the first random number sequence generation unit 171 includes a linear feedback shift register having six shift registers as in the case of FIG.

The first random number sequence generation unit 171 uses the input of the initial value setting signal S21 as a trigger to set the 6 bits (a0 to a5) constituting the first key information 11 in the corresponding shift registers 171a to 171f, A binary random number sequence is generated using the clock signal S20 as a reference timing. The first multi-value conversion unit 172 takes out the binary random number sequence in parallel every p bits (p = 6 in FIG. 9) with the input of the read signal S22 as a trigger, for example, by binary-to-decimal conversion, The multi-level code string 12 having the total number of levels: 2 ^p (2 ⁶ ) is converted. A third party who is an eavesdropper acquires the multi-level code sequence 12 as it is, and acquires a binary random number sequence similar to that generated by the first random number sequence generation unit 171 by decimal-to-binary conversion.

  Here, it is generally known that a pseudo-random number sequence generated by a linear feedback shift register as shown in FIG. 9 can easily predict a subsequent bit string if a partial bit string can be obtained continuously. For example, in the Berlekamp-Massey method (hereinafter referred to as the BM method), a 2 k-bit pseudo random number is used for the number k of linear feedback shift registers used to generate the pseudo random number (k = 6 in FIG. 9). By acquiring continuously, the configuration (tap position, initial value) of the linear feedback shift register can be easily derived, and the subsequent random number sequence can be predicted.

  On the other hand, in the first multi-level code generator 111a (second multi-level code generator 212a) in the sixth embodiment of the present invention, the first bit selector 174 is as shown in FIG. Then, the remaining q = 5-bit binary random number sequence is output by removing predetermined one bit from the p = 6 bit binary random number sequence taken out in parallel from the first random number sequence generation unit 171. Then, the first multi-level conversion unit 172 converts the q = 5 bit binary random number sequence output from the first bit selection unit 174 into the multi-level code sequence 12.

  The operation of the first multi-level code generator 111a at this time will be described in detail with reference to FIG. 12B. As illustrated in FIG. 12B, for example, the first bit selection unit 174 outputs, for example, the second bit (D2) among the 6 bits (D1 to D6) output from the first random number sequence generation unit 171. The remaining 5 bits removed are selected and output to the first multi-value conversion unit 172. That is, the first multilevel code generation unit 111a according to the sixth embodiment of the present invention does not convert the binary random number sequence output from the first random number sequence generation unit 171 into the multilevel code sequence 12 as it is. Rather, some bits of the binary random number sequence are intentionally lost or concealed, and then converted to the multilevel code sequence 12.

  The first multi-level code generation unit 111a (second multi-level code generation unit 212a) according to the sixth embodiment of the present invention may be configured as shown in FIG. FIG. 13 is a block diagram illustrating another configuration example of the first multi-level code generation unit 111a according to the sixth embodiment of the present invention. That is, as shown in FIG. 13, the first multi-level code generation unit 111a removes predetermined bits fixed in advance from the p-bit binary random number sequence taken out in parallel from the first random number sequence generation unit 171. The remaining q bits (remaining output signal from which an output signal of a predetermined shift register is removed) may be output to the first multi-value conversion unit 172. In the example of FIG. 13, the remaining output signal from which the output signal D2 of the shift register 171b has been removed is output to the first multi-level code converter 172.

  More desirably, the first multi-level code generator 111a (second multi-level code generator 212a) according to the sixth embodiment of the present invention may be configured as shown in FIG. . FIG. 14 is a block diagram showing another configuration example of the first multi-level code generation unit 111a according to the sixth embodiment of the present invention. That is, as shown in FIG. 14, the first multi-level code generator 111a removes arbitrarily selected bits from the p-bit binary random number sequence taken out in parallel from the first random number sequence generator 171. The remaining q bits (the remaining output signals excluding the output signal of any shift register) may be output to the first multi-value conversion unit 172. Specifically, the first bit selection unit 174 removes bits from the p-bit binary random number sequence extracted in parallel from the first random number sequence generation unit 171 in accordance with the pseudo random number output from the random number generation unit 175. And the remaining q bits from which the selected bits have been removed are output to the first multi-value conversion unit 172.

  Furthermore, the first multi-level code generator 111a (second multi-level code generator 212a) according to the sixth embodiment of the present invention may be configured as shown in FIG. FIG. 15 is a block diagram showing another configuration example of the first multi-level code generation unit 111a according to the sixth embodiment of the present invention. That is, as shown in FIG. 15, the first multi-level code generation unit 111a newly includes a second timing signal generation unit 173b that supplies the read signal S22 to the first multi-level conversion unit 172. The second timing signal generator 173b operates asynchronously with the first random number sequence generator 171 using the second clock signal S23 as a reference timing.

  As a result, the output signals (for example, D1 to D6) from the shift registers 171a to 171f constituting the first random number sequence generator 171 are accurately received by the latches 172a to 172f constituting the first multi-value converter 172. For example, as shown in FIG. 16, predetermined bits (Dc, D2, D12 in FIG. 16) are missing, and the same bits (Db, D1, D10 in FIG. 16) are read twice. . That is, the first multi-level code generator 111a shown in FIG. 15 does not convert the binary random number sequence output from the first random number sequence generator 171 into the multi-level code sequence 12 as it is, but a binary random number. A part of the bits of the sequence is intentionally omitted or concealed, and then converted into a multi-level code sequence 12. With this configuration, 2k-bit pseudorandom numbers are intentionally acquired continuously even in situations where the quantum fluctuation is not large enough and a ciphertext is easily acquired by a third party. This makes it difficult to decode and analyze the pseudo-random number sequence by the BM method or the like.

  With the above configuration, 2k-bit pseudorandom numbers are intentionally acquired continuously even under circumstances where the quantum fluctuation is not sufficiently large and the ciphertext is easily acquired by a third party. Therefore, it is difficult to decode and analyze the pseudo random number sequence by the BM method as described above.

  As described above, according to the sixth embodiment of the present invention, when the information data 10 to be transmitted is encoded as the multilevel signal 13, the distance between the signal points of the multilevel signal 13 is determined as the received signal. By appropriately setting the amount of noise included in the signal, the third party decrypts / decodes the multi-level signal 13 by giving a decisive deterioration to the received signal quality at the time of eavesdropping by the third party. Can be difficult. In addition, even when a ciphertext is acquired by a third party, it is possible to easily provide a safer data communication device by generating a multi-value key so that the key information is not easily estimated. .

(Seventh embodiment)
FIG. 17 is a block diagram showing an example of the configuration of the data communication apparatus according to the seventh embodiment of the present invention. In FIG. 17, the data communication apparatus according to the seventh embodiment of the present invention has a configuration in which a data transmission apparatus 25107 and a data reception apparatus 25207 are connected by a transmission line 110. Compared with the data communication devices according to the fifth to sixth embodiments described above, the data communication device according to the seventh embodiment includes a first multi-level code generation unit 111a and a second multi-level code generation unit. The configuration of 212a is different. The first multi-level code generation unit 111a includes a first random number sequence generation unit 171, a first bit replacement unit 176, and a first multi-level conversion unit 172. The second multi-level code generation unit 212a includes a second random number sequence generation unit 271, a second bit replacement unit 276, and a second multi-level conversion unit 272.

  The first random number sequence generation unit 171 generates a predetermined pseudo random number sequence using the first key information 11 as an initial value. The first bit replacement unit 176 extracts a bit sequence of p bits (p is an arbitrary integer) from the pseudo random number sequence generated by the first random number sequence generation unit 171 and outputs the permutation of the extracted bit sequence. To do. The first multi-level conversion unit 172 converts the q-bit (p = q in this example) bit sequence output from the first bit replacement unit 176 into a multi-level code sequence 12 having a level corresponding to the bit sequence. Convert to Similarly, the second random number sequence generation unit 271 generates a predetermined pseudo random number sequence using the second key information 16 as an initial value. The second bit replacement unit 276 extracts a bit sequence of p bits (p is an arbitrary integer) from the pseudo random number sequence generated by the second random number sequence generation unit 271, and outputs the sequence of the extracted bit system. To do. The second multilevel conversion unit 272 converts the bit sequence of q bits (p = q in this example) output from the second bit replacement unit 276 into a multilevel code sequence 17 having a level corresponding to the bit sequence. Convert to

  FIG. 18 is a schematic diagram illustrating an example of a detailed configuration of the first multi-level code generation unit 111a according to the seventh embodiment of the present invention. FIG. 19 is a schematic diagram for explaining the effect of the data communication apparatus according to the seventh embodiment of the present invention. Hereinafter, a data communication apparatus according to the seventh embodiment of the present invention will be described in detail with reference to FIG. 18 and FIG.

  First, wiretapping by a third party will be described. Similar to the above-described sixth embodiment, a third party who is an eavesdropper uses a configuration according to a data reception device provided by a legitimate receiver, or uses a higher performance data reception device, and “known plaintext attack”. It is assumed that the received modulated signal 14 is decoded by “ That is, as shown in FIG. 12A, if the quantum noise is not sufficiently large, an encryption key is obtained by a third party, and as a result, the ciphertext may be easily decrypted.

  On the other hand, in the first multi-level code generation unit 111a (second multi-level code generation unit 212a) in the seventh embodiment of the present invention, as shown in FIG. The p = 6 bit binary random number sequence taken out in parallel from the 1 random number sequence generation unit 171 is temporarily input, and the q = 6 bit binary random number sequence in which the permutation of the input binary random number sequence is replaced is output. . Then, the first multi-level conversion unit 172 converts the q = 6 bit binary random number sequence output from the first bit replacement unit 176 into the multi-level code sequence 12. For example, as shown in FIG. 19, the bit replacement unit 176 replaces the permutation of 6 bits (D1, D2, D3, D4, D5, D6) output from the first random number sequence generation unit 171 and obtains the result. The obtained 6 bits (D5, D3, D1, D6, D2, D4) are output to the first multi-value conversion unit 172. That is, the first multilevel code generation unit 111a according to the seventh embodiment of the present invention converts the binary random number sequence output from the first random number sequence generation unit 171 into the multilevel code sequence 12 as it is. Instead, the permutation of the binary random number sequence is intentionally replaced and then converted to the multi-level code sequence 12.

  As described with reference to FIG. 4, the third party who is an eavesdropper does not share the key information 11 and 16, and thus erroneously identifies the bits of the multilevel signal by the noise component superimposed on the modulation signal 14. It is assumed that As such a multilevel signal identification error, an eavesdropper is particularly likely to erroneously identify information corresponding to the low-order bits of the multilevel signal, and thereby information on a specific location in the binary signal after identification. There is a high probability that only mistakes occur periodically. The first multi-level code generation unit 111a according to the seventh embodiment of the present invention replaces the bit permutation of the binary random number sequence generated by the first random number sequence generation unit 171 to thereby identify the binary after identification. In the signal, it is possible to diffuse the identification error not only with information corresponding to the lower bits of the multilevel signal but also with information corresponding to the upper bits. That is, the first multi-level code generator 111a can make the position of the multi-level signal identification error unpredictable.

  More preferably, the first multi-level code generation unit 111a changes the bit replacement procedure by the first bit replacement unit 119 at any time without fixing. Specifically, as illustrated in FIG. 18, the bit replacement unit 176 generates a binary value generated by the first random number sequence generation unit 171 in accordance with the pseudo random number output from the second random number generation unit 175 b. Replace the bit permutation of the random number sequence almost randomly.

  Further, the first multi-level code generator 111a (second multi-level code generator 212a) according to the seventh embodiment of the present invention may be configured as shown in FIG. FIG. 20 is a block diagram showing another configuration example of the first multi-level code generation unit 111a according to the seventh embodiment of the present invention. In FIG. 20, the first multi-level code generation unit 111 a includes a memory unit 177, a second timing signal generation unit 173 b, and a third timing signal generation unit 173 instead of the timing signal generation unit 173 and the first bit replacement unit 176. Timing signal generator 173c, a third random number generator 175c, and an address converter 178.

  The second timing signal generator 173b generates and outputs the write address S24 together with the clock signal S20 and the initial value setting signal S21 supplied to the first random number sequence generator 171. The third timing signal generator 173c generates a read address S25 together with the read signal S22 supplied to the first multi-value converter 172 using the clock signal S20 as a reference timing. The address conversion unit 178 converts the read address S25 according to the value of the pseudo random number output from the third random number generation unit 175c, and outputs it as the second read address S26. The memory unit 177 writes (records) the p = 6 bit binary random number sequence taken out in parallel from the first random number sequence generation unit 171 to the address specified by the write address S24, and also performs the second reading. A binary random number sequence of p = 6 bits is read from the address designated by the address S26 and is output to the first multi-value conversion unit 172. The first multilevel conversion unit 172 converts the input binary random number sequence into the multilevel code sequence 12.

  With the above configuration, 2k-bit pseudorandom numbers are intentionally acquired continuously even under circumstances where the quantum fluctuation is not sufficiently large and the ciphertext is easily acquired by a third party. This makes it difficult to decode and analyze the pseudo-random number sequence by the BM method as described above.

  As described above, according to the seventh embodiment of the present invention, when the information data 10 to be transmitted is encoded as the multi-level signal 13, the distance between the signal points of the multi-level signal 13 is determined as the received signal. By appropriately setting the amount of noise included in the message, it is possible to give decisive deterioration to the quality of the received signal at the time of eavesdropping by a third party, making it difficult to decode and decode it. In addition, even when a ciphertext is acquired by a third party, it is possible to easily provide a safer data communication device by generating a multi-value key so that the key information is not easily estimated. .

  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 apparatus according to the present invention is useful as a secure secret communication apparatus that does not receive eavesdropping / 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. 3 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 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. The block diagram which shows an example of a structure of the data communication apparatus which concerns on the 2nd Embodiment of this invention. The block diagram which shows an example of a structure of the data communication apparatus which concerns on the 3rd Embodiment of this invention. The figure which shows an example of the multi-value 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 structure of the data communication apparatus which concerns on the 5th Embodiment of this invention. The schematic diagram which shows an example of a detailed structure of the 1st multi-level code generation part 111a which concerns on the 5th Embodiment of this invention. The block diagram which shows an example of a structure of the data communication apparatus which concerns on the 6th Embodiment of this invention. The schematic diagram which shows an example of a detailed structure of the 1st multi-level code generation part 111a which concerns on the 6th Embodiment of this invention. Schematic diagram for explaining a third party's wiretapping act on the data communication apparatus according to the sixth embodiment of the present invention. The schematic diagram for demonstrating the effect of the data communication apparatus which concerns on the 6th Embodiment of this invention. The block diagram which shows the other structural example of the 1st multi-level code generation part 111a which concerns on the 6th Embodiment of this invention. The block diagram which shows the other structural example of the 1st multi-level code generation part 111a which concerns on the 6th Embodiment of this invention. The block diagram which shows the other structural example of the 1st multi-level code generation part 111a which concerns on the 6th Embodiment of this invention. Schematic diagram for explaining the effect of the first multi-level code generator 111a shown in FIG. The block diagram which shows an example of a structure of the data communication apparatus which concerns on the 7th 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 7th Embodiment of this invention. The schematic diagram for demonstrating the effect of the data communication apparatus which concerns on the 7th Embodiment of this invention. The block diagram which shows the other structural example of the 1st multi-level code generation part 111a which concerns on the 7th Embodiment of this invention. Block diagram showing the configuration of a conventional data communication device

Explanation of symbols

10, 18 Information data 11, 16, 91, 96, 99 Key information 12, 17 Multi-level code string 13, 15 Multi-level signal 14, 94 Modulation signal S20, S23 Clock signal S21 Initial value setting signal S22 Read signal S24 Write Address S25, S26 Read address 110 Transmission path 111 Multi-level encoding unit 111a First multi-level code generation unit 111b Multi-level processing unit 112, 912 Modulation unit 113 First data inversion unit 114 Noise control unit 114a Noise generation unit 114b Combining unit 171 First random number sequence generating unit 171a to 171f Shift register 171g Exclusive OR element 172 First multi-value converting unit 171a to 172f Latch 172g D / A converting unit 173 Timing signal generating unit 174 First bit selection Unit 175 Random number generator 176 First bit replacement unit 211, 9 14, 916 Demodulator 212, 915, 917 Multi-level decoder 212a Second multi-level code generator 212b Multi-level identifier 213 Second data inversion unit 271 Second random number sequence generator 10101-10103, 25105 25107 Data transmitting device 10201-10202, 25205-25207 Data receiving device

Claims (13)

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 that generates a multi-level code sequence in which the 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 a predetermined modulation process on the multilevel signal and generates a modulation signal;
The multi-level code generation unit generates the multi-level code sequence based on a changed random number sequence after changing a bit sequence of a binary random number sequence generated based on the predetermined key information. A data transmission device as a feature. The multi-level code generator is
A random number sequence generation unit that generates a binary random number sequence that is a pseudo-random number sequence from the predetermined key information;
A bit selection unit that selects a predetermined bit sequence from the binary random number sequence generated by the random number sequence generation unit, and outputs the selected bit sequence as the changed random number sequence;
The data transmission device according to claim 1, further comprising: a multilevel conversion unit that converts the random number sequence after change into the multilevel code sequence. The multi-level code generator further includes a random number generator that generates a predetermined pseudo-random number sequence,
The bit selection unit changes a bit sequence selected from a binary random number sequence generated by the random number sequence generation unit based on a pseudo-random number sequence generated by the random number generation unit. The data transmission device described. The multi-level code generator is
A random number sequence generation unit that generates a binary random number sequence that is a pseudo-random number sequence from the predetermined key information;
A remaining bit sequence obtained by removing a predetermined bit sequence fixed in advance from the binary random number sequence generated by the random number sequence generation unit is used as the changed random number sequence, and the changed random number sequence is converted into the multi-level code sequence. The data transmission device according to claim 1, further comprising a multi-value conversion unit. The multi-level code generator is
A random number sequence generation unit that generates a binary random number sequence that is a pseudo-random number sequence from the predetermined key information;
A multi-value conversion unit that converts the binary random number sequence generated by the random number sequence generation unit into the multi-value code sequence;
The multi-value conversion unit operates asynchronously with the random number sequence generation unit, and handles the binary random number sequence generated by the random number sequence generation unit as the changed random number sequence, according to claim 1, The data transmission device described. The multi-level code generator is
A random number sequence generation unit that generates a binary random number sequence that is a pseudo-random number sequence from the predetermined key information;
A bit replacement unit that outputs a bit sequence obtained by replacing the permutation of the binary random number sequence generated by the random number sequence generation unit as the changed random number sequence;
The data transmission device according to claim 1, further comprising: a multilevel conversion unit that converts the random number sequence after change into the multilevel code sequence. The multi-level code generator further includes a random number generator that generates a predetermined pseudo-random number sequence,
The bit replacement unit determines a rule for replacing the binary random number sequence generated by the random number sequence generation unit based on the pseudo random number sequence generated by the random number generation unit. Data transmission device. The multi-level code generator is
A random number sequence generation unit that generates a binary random number sequence that is a pseudo-random number sequence from the predetermined key information;
A memory unit for storing a binary random number sequence generated by the random number sequence generation unit;
A multi-value conversion unit that converts a binary random number sequence read from the memory unit into the multi-level code sequence,
The multi-value conversion unit treats the binary random number sequence generated by the random number sequence generation unit as the post-change random number sequence by changing a read address of the memory unit. Data transmission device.   The data transmission device according to claim 2, wherein the random number sequence generation unit includes a linear feedback shift register including a plurality of shift registers and an exclusive OR element.   The multi-level conversion unit includes a plurality of latches, and a D / A conversion unit that converts a bit sequence output from the plurality of latches into the multi-level code sequence. Data transmission device. 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 generation unit generates the multi-level code sequence based on a changed random number sequence after changing a bit sequence of a binary random number sequence generated based on the predetermined key information. A data receiving device. 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 in a random manner based on the predetermined key information;
A multi-level processing step of combining the multi-level code sequence and the information data to generate 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 step of performing a predetermined modulation process on the multilevel signal and generating a modulation signal,
The multi-level code generation step generates the multi-level code sequence based on the changed random number sequence after changing the bit sequence of the binary random number sequence generated based on the predetermined key information. A data transmission method as a feature. 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 generates the multi-level code sequence based on the changed random number sequence after changing the bit sequence of the binary random number sequence generated based on the predetermined key information. A method for receiving data.

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