JP2006295338A - Data transmission apparatus, data reception apparatus, and data communications apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a data communications apparatus with high security that considerably increases a time required for a tapper to analyze an encrypted text resulting, in requiring astronomical computation amount. <P>SOLUTION: A data transmission apparatus uses a multi-value code sequence and information data, obtained by a predetermined first initial value (key information) to produce a multi-value signal, whose level changes almost randomly. The data transmission apparatus produces the multi-valued signal, by using a plurality of key information items and switching the key information items with a prescribed timing. The data transmission apparatus converts the multi-valued signal into a modulation signal with a prescribed modulation form and transmits the modulation signal. A data receiving apparatus demodulates the modulation signal to output the multi-value signal, receives a predetermined second initial value (key information) and the multi-value signal and reproduces the information data. Thus, even if the modulation signal is intercepted and the modulation signal can be reproduced into a multi-valued signal, it is possible to make it difficult for the information data to be decrypted from the multi-valued signal. <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 communication only among specific persons, original information (key information) for encoding / decoding is shared between transmission / reception, and information data (plaintext) to be transmitted based on the information. ) Is implemented mathematically / inversely to realize secret communication. FIG. 13 is a block diagram showing a configuration of a conventional data transmission apparatus based on the configuration. In FIG. 13, the conventional data communication apparatus includes a transmission unit 90001, a transmission path 913, and a reception unit 90002. The transmission unit 90001 includes an encoding unit 911 and a modulation unit 912. The receiving unit 90002 includes a demodulating unit 914 and a decoding unit 915. 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. . Further, in order to explain an eavesdropping action by a third party, FIG. 13 includes an eavesdropper receiving unit 90003 including an eavesdropper demodulation unit 916 and an eavesdropper decoding unit 917. The third key information 99 is input to the eavesdropper decryption unit 917. The operation of the conventional data communication apparatus will be described below with reference to FIG.

In the transmission unit 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 reception unit 90002, the demodulation unit 914 demodulates the modulated signal 94 transmitted via the transmission path 913 by a predetermined demodulation method. The decryption unit 915 performs decryption (decryption) based on the second key information 96 that is the same as the first key information 91 shared with the encoding unit 911, and outputs the original information data 98 To do.
In eavesdropping on a modulation signal (information data) transmitted between the transmission unit 90001 and the reception unit 90002, in the eavesdropper reception unit 90003, the eavesdropper demodulation unit 916 transmits a part of the modulation signal transmitted through the transmission path 913. The eavesdropper decrypting unit 917 tries to decrypt the data based on the third key information 99. Here, it is assumed that the eavesdropper decoding unit 917 does not share key information with the encoding unit 911. That is, since the eavesdropper decryption unit 917 performs decryption based on the third key information 99 different from the first key information 91, the original information data cannot be correctly reproduced.

Such mathematical encryption based on mathematical operations (also called calculation encryption or software encryption) can be applied to an access system or the like as described in, for example, Japanese Patent Application Laid-Open No. 9-205420. That is, in 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, each optical receiver has a desired A signal directed to other subscribers other than the optical signal is input. Therefore, by encrypting information data for each subscriber using different key information, it is possible to prevent leakage and eavesdropping on each other's information and realize safe data communication.
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 combine all possible combinations of ciphertext (modulated signal or encrypted information data) even if key information is not shared. In principle, cryptanalysis can be performed if an attempt is made to apply a calculation (brute force attack) using key information or a special analysis algorithm. Particularly, the processing speed of computers in recent years has been remarkably improved, and if a computer based on a new principle such as a quantum computer is realized in the future, there has been a problem that a ciphertext can be wiretapped within a finite time.

  Therefore, an object of the present invention is to provide a highly confidential data communication apparatus based on an astronomical calculation amount by significantly increasing the time required for an eavesdropper to analyze a ciphertext.

  The present invention is directed to a data transmission apparatus that performs encrypted communication. And in order to achieve the said objective, the data transmitter of this invention is equipped with a multi-value encoding part and a modulation | alteration part. The multi-level encoding unit inputs predetermined key information and information data determined in advance, and generates a multi-level signal whose signal level changes substantially in a random manner. The modulation unit generates a modulation signal of a predetermined modulation format based on the multilevel signal.

  Preferably, the multi-level encoding unit includes a multi-level code generation unit and a multi-level processing unit. The multi-level code generation unit generates a multi-level code string whose signal level changes in a substantially random manner from predetermined key information. The multi-level processing unit synthesizes the multi-level code sequence and the information data according to a predetermined process, and generates a multi-level signal having a signal level uniquely corresponding to the combination of the levels of the multi-level code sequence and the information data.

  Preferably, the multi-level encoding unit converts the multi-level code sequence into a converted multi-level code sequence having a bias level number different from the bias level number for determining the level interval of the multi-level code sequence using the conversion key information. It is preferable to further include a multi-level code string converting unit.

  The multi-level code generation unit outputs a multi-level code sequence whose bias level number changes every predetermined period, and the multi-level code sequence conversion unit responds to the change in the bias level number of the multi-level code sequence. It is preferable to change the number of bias levels of the converted multilevel code sequence.

  Further, the multi-level code sequence conversion unit converts the multi-level code sequence into the converted multi-level code sequence by using any one of the plurality of conversion key information for each predetermined key information use period. Good.

  Preferably, the multi-level code sequence conversion unit calculates at least one or more offset values for allocating the level of the multi-level code sequence to the level of the converted multi-level code sequence from the conversion key information, and for each predetermined allocation period The level of the multi-level code sequence may be assigned to the level of the converted multi-level code sequence using any one of the at least one offset value.

  Preferably, the conversion key information includes a first prime number and a multiplication value that is a product of a second prime number and a third prime number that are different from the first prime number. A power calculation unit is further provided that calculates a power value obtained by raising the number of bias levels of the value code string to the power of the first prime number, and uses a remainder obtained by dividing the power value by the multiplied value as the number of bias levels of the converted multi-level code string. Good.

  The present invention is also directed to a data receiving apparatus that performs cryptographic communication. And in order to achieve the said objective, the data receiver of this invention is equipped with a demodulation part and a multi-value decoding part. The demodulator demodulates a modulation signal in a predetermined modulation format and outputs a multilevel signal. The multi-level decryption unit inputs predetermined key information and a multi-level signal that are set in advance, and outputs information data.

  Preferably, the multi-level decoding unit includes a multi-level code string generation unit and a multi-level identification unit. The multi-level code sequence generating unit generates a multi-level code sequence whose signal level changes substantially randomly from the key information. The multi-level identifying unit identifies the multi-level signal based on the multi-level code string and outputs information data.

  Preferably, the multi-level encoding unit converts the multi-level code sequence into a converted multi-level code sequence having a bias level number different from the bias level number for determining the level interval of the multi-level code sequence using the conversion key information. It is preferable to further include a multi-level code string converting unit.

  The multi-level code generation unit outputs a multi-level code sequence whose bias level number changes every predetermined period, and the multi-level code sequence conversion unit responds to the change in the bias level number of the multi-level code sequence. It is preferable to change the number of bias levels of the converted multilevel code sequence.

  Further, the multi-level code sequence conversion unit converts the multi-level code sequence into the converted multi-level code sequence by using any one of the plurality of conversion key information for each predetermined key information use period. Good.

  Preferably, the multi-level code sequence conversion unit calculates at least one or more offset values for allocating the level of the multi-level code sequence to the level of the converted multi-level code sequence from the conversion key information, and for each predetermined allocation period The level of the multi-level code sequence may be assigned to the level of the converted multi-level code sequence using any one of the at least one offset value.

  Preferably, the conversion key information includes a first prime number and a multiplication value that is a product of a second prime number and a third prime number that are different from the first prime number. A power calculation unit is further provided that calculates a power value obtained by raising the number of bias levels of the value code string to the power of the first prime number, and uses a remainder obtained by dividing the power value by the multiplied value as the number of bias levels of the converted multi-level code string. Good.

  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, it is possible to significantly increase the time required to analyze the ciphertext and provide a highly confidential data communication apparatus based on the astronomical calculation amount.

  In addition, the data transmitting apparatus and data receiving apparatus of the present invention converts the multi-level code sequence into a converted multi-level code sequence having a bias level number different from the bias level number of the multi-level code sequence using other key information. By generating a multilevel signal using the converted multilevel code string and information data, the key information is included in the multilevel number of the multilevel signal. This makes it difficult to decode and decode the multilevel signal by a third party.

  Further, the data transmitting apparatus and data receiving apparatus of the present invention determine the number of bias levels of the converted multilevel code string by using the RSA public key method procedure, thereby determining the multilevel from the number of bias levels of the converted multilevel code string. Deriving the number of bias levels of the code string is extremely difficult. Therefore, it is very difficult for a third party to determine the multi-level number of the multi-level signal when decoding and decoding the multi-level signal.

(First embodiment)
FIG. 1 is a block diagram showing a configuration of a data communication apparatus according to the first embodiment of the present invention. In FIG. 1, the data communication apparatus includes a multi-level encoding unit 111, a modulation unit 112, a transmission path 110, a demodulation unit 211, and a multi-level decoding unit 212. The multi-level encoding unit 111 includes a first multi-level code generation unit 111a and a multi-level processing unit 111b. The multi-level decoding unit 212 includes a second multi-level code generation unit 212a and a multi-level identification unit 212b. The multi-level encoding unit 111 and the modulation unit 112 constitute a transmission unit 10101, and the demodulation unit 211 and the multi-level decoding unit 212 constitute a reception unit 10201. 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 that propagates a radio signal.
2 and 3 are schematic diagrams for explaining the modulation signal waveform output from the modulation unit 112. FIG. The operation of the first embodiment will be described below with reference to FIGS. 2 and 3.

  The first multi-level code generator 111a generates a multi-level code sequence 12 (FIG. 2 (b)) whose signal level changes in a substantially random manner based on predetermined first key information 11 determined in advance. To do. The multilevel processing unit 111b receives the multilevel code string 12 and the information data 10 (FIG. 2A), synthesizes both signals according to a predetermined procedure, and sets a level uniquely corresponding to the combination of the signal levels. The multi-value signal 13 (FIG. 2 (c)) is generated and output. For example, in FIG. 2, the level of the multilevel code sequence 12 changes to c1 / c5 / c3 / c4 with respect to the time slot t1 / t2 / t3 / t4, and the information data 10 is added using this level as a bias level. Thus, the multilevel signal 13 that changes as 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 each bias level (level of the multilevel code string 12) c1 /. Corresponding to c2 / c3 / c4 / c5, a set of levels (L1, L4) / (L2, L5) / (L3, L6) / (L4, L7) / (L5, L8) that the multilevel signal 13 can take ) Are referred to as first to fifth “bases”, and the minimum signal point distance of the multilevel signal 13 is referred to as “step width”. The modulation unit 112 converts the multi-level signal 13 as original data into a modulation signal 14 having a predetermined modulation format, and sends it to the transmission line 110.

  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 212a shares in advance the second key information 16 that is the same as the first key information 11 and stores the second key information 16 in the multi-level code string 12 based on the second key information 16. A corresponding multi-level code string 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 of a predetermined modulation format transmitted and received by the modulation unit 112 and the demodulation unit 211 via the transmission line 110 is obtained by modulating an electromagnetic wave (electromagnetic field) or a light wave with the multilevel signal 13. It is.

  The generation of the multi-level signal 13 in the multi-level processing unit 111b is not limited to the method of adding the multi-level code sequence 12 and the information data 10 as described above. Any procedure may be used, such as a method of amplitude modulating / controlling the level or a method of sequentially reading out a multi-level signal level corresponding to a combination of both signal levels from a memory that stores them in advance according to both signal levels. Absent.

  In FIG. 2 and FIG. 3, the number of values of the multi-level signal is expressed as “8”, but is not limited to this, and may be larger or smaller. In addition, the information amplitude is expressed as three times or an integer multiple of the step width of the multilevel signal. However, the information amplitude is not limited to this and may be any odd or even multiple, or may not be an integral multiple. . Further, in this regard, in FIGS. 2 and 3, each level (each bias level) of the multilevel code string is arranged so as to be approximately the center between the levels of the multilevel signal, but the present invention is not limited to this. Instead, each level of the multilevel code string may not be substantially the center between the levels of the multilevel signal, or may correspond to each level of the multilevel signal. In addition, it is assumed that the change rates of the multi-level code sequence and the information data are equal and in synchronization with each other. However, the present invention is not limited to this, and one change rate may be faster (or slower) than the other. Asynchronous.

  Next, the wiretapping operation of the modulation signal by a third party will be described. It is assumed that the third party receives and decodes the modulated signal using a configuration according to the receiving unit 10201 provided by the authorized receiver, or a higher-performance receiving unit (an eavesdropper receiving unit). The demodulator (the eavesdropper demodulator) reproduces the multilevel signal by demodulating the modulated signal. However, since the multilevel decoding unit (the eavesdropper multilevel decoding unit) does not share the first key information 11 with the multilevel encoding unit 111 of the transmission unit 10101, as in the reception unit 10201. Binary determination based on the multi-level code sequence generated from the key information cannot be performed. As an eavesdropping operation that can be considered in such a case, there is a method of simultaneously identifying all levels of a multilevel signal (generally called “brute force attack”). In other words, threshold values for all signal points that can be taken by the multilevel signal are prepared, simultaneous determination is performed, and the determination result is analyzed to extract correct key information or information data. For example, the multilevel code sequence level c0 / c1 / c2 / c3 / c4 / c5 / c6 shown in FIG. 2 is used as a threshold value to identify the level by performing multilevel determination on the multilevel signal. .

  However, in an actual transmission system, noise is generated due to various factors, and this is superimposed on the modulation signal, whereby the level of the multilevel signal fluctuates temporally and instantaneously as shown in FIG. In such a case, the S / N ratio (signal-to-noise intensity ratio) of the signal to be determined in the binary determination operation by the authorized receiver (reception unit 10201) is determined by the ratio between the information amplitude and the noise amount in the multilevel signal. On the other hand, in the multilevel determination operation by the eavesdropper receiver, the SN ratio is determined by the ratio between the step width of the multilevel signal and the amount of noise. For this reason, when the noise level of the signal to be determined is the same, the SN ratio becomes relatively small, and the transmission characteristics (error rate) deteriorate. That is, it is possible for a third party to induce an identification error with respect to a brute force attack based on all thresholds, thereby making eavesdropping difficult. In particular, if the step width of a multi-level signal is set to the same order or smaller than the noise amplitude (the spread of the noise intensity distribution), multi-level determination by a third party is virtually impossible, making it ideal. Can be effectively prevented.

  Note that, as described above, the noise superimposed on the signal to be determined (multi-level signal or modulation signal) is the thermal noise possessed by the spatial field, electronic components, etc. when electromagnetic waves such as radio signals are used for the modulation signal. When (Gaussian noise) is used, in addition to thermal noise, fluctuation of the number of photons (quantum noise) when a photon is generated 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 a multi-level signal based on the amount of noise prevents wiretapping by a third party. It is possible to ensure absolute safety of data communication.

  As described above, according to the present embodiment, information data to be transmitted is encoded as a multi-level signal, and the distance between the signal points is appropriately set with respect to the amount of noise, thereby enabling a third party. It is possible to provide a safe data communication apparatus that gives definite degradation to the quality of a received signal at the time of eavesdropping and makes it difficult to decode and decode it.

(Second Embodiment)
FIG. 5 is a block diagram showing a configuration of a data communication apparatus according to the second embodiment of the present invention. In this figure, the data communication apparatus includes a multi-level encoding unit 111, a modulation unit 112, a transmission path 110, a demodulation unit 211, a multi-level decoding unit 212, a first data inversion unit 113, 1 is different from the configuration of FIG. 1 in that a first data inversion unit 113 and a second data inversion unit 213 are newly provided. Further, the multilevel encoding unit 111, the modulation unit 112, and the first data inversion unit 113 constitute a transmission unit 10102, a demodulation unit 211, a multilevel decoding unit 212, and a second data inversion. The receiving unit 10202 is configured with the unit 213. The operation of this embodiment will be described below.

  Since the configuration of this example conforms to the above-described first embodiment (FIG. 1), the same number is assigned to the blocks performing the same operation, the description thereof is omitted, and only the differences are described. To do. In this configuration, the first data inversion unit 113 does not fix the correspondence between the information “0” and “1” and the low level and the high level that the information data has, and determines the correspondence in a predetermined procedure. Change almost randomly. For example, like the multi-level encoding unit 111, an exclusive OR operation with a random number sequence (pseudo-random number sequence) generated based on a predetermined initial value is performed, and the calculation result is multi-level encoded. Output to the unit 111. The second data inverting unit 213 corresponds to “0/1” and “Low / High” for the data output from the multi-level decoding unit 212 in the reverse procedure of the first data inverting unit 113. Change the relationship. For example, the initial value that is the same as the initial value included in the first data inversion unit 113 is shared, and an exclusive OR operation with a bit inversion sequence of a random number generated based on the initial value is performed, and the result is used as information data Reproduce.

  As described above, according to the present embodiment, the inversion of the information data to be transmitted is performed almost randomly, thereby increasing the complexity of the multilevel signal as a cipher and decryption / decryption by a third party. It is possible to provide a safer data communication apparatus.

(Third embodiment)
FIG. 6 is a block diagram showing a configuration of a data communication apparatus according to the third embodiment of the present invention. In this figure, the data communication apparatus includes a multilevel encoding unit 111, a modulation unit 112, a transmission path 110, a demodulation unit 211, a multilevel decoding unit 212, and a noise control unit 114. The difference from the configuration of 1 is that a noise control unit 114 is newly provided. Furthermore, the noise control unit 114 includes a noise generation unit 114a and a synthesis unit 114b. The multi-level encoding unit 111, the modulation unit 112, and the noise control unit 114 constitute a transmission unit 10103, and the demodulation unit 211 and the multi-level decoding unit 212 constitute a reception unit 10201. The operation of this embodiment will be described below.

  Since the configuration of the present embodiment conforms to that of the first embodiment (FIG. 1), the same number is assigned to blocks performing the same operation, the description thereof is omitted, and only the differences are described. To do. In the configuration, the noise generating unit 114 a generates predetermined noise, and the synthesizing unit 114 b synthesizes it with the multilevel signal and outputs it to the modulating unit 112. That is, the level fluctuation of the multi-level signal described with reference to FIG. 4 is intentionally generated, and the SN ratio of the multi-level signal is controlled to an arbitrary value, whereby the SN of the determination target signal input to the multi-level identification unit 212b. Control the ratio. As described above, thermal noise, quantum noise, or the like is used as the noise generated by the noise generator 114a. In addition, a multilevel signal in which noise is synthesized (superimposed) is referred to as a noise superimposed multilevel signal.

  As described above, according to the present embodiment, the information data to be transmitted is encoded as a multilevel signal, and the SN ratio is arbitrarily controlled, so that the received signal quality at the time of eavesdropping by a third party can be reduced. It is possible to provide a safer data communication apparatus that intentionally gives decisive deterioration and makes it more difficult to decode and decode it.

(Fourth embodiment)
The operation of the data communication apparatus according to the fourth embodiment of the present invention will be described. The configuration of the present embodiment conforms to the first embodiment (FIG. 1) or the third embodiment (FIG. 6). In the configuration, 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 into a variation amount of each level, that is, a noise intensity distribution superimposed on each level. Set and output according to Specifically, the distance between the signal points is distributed 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. When the amount of noise superimposed on each level is equal, the step widths are set equally.

  In general, when a light intensity modulation signal using a semiconductor laser (LD) as a light source is assumed as a modulation signal output from the modulation unit 112, the fluctuation width (noise amount) depends on the level of the multilevel signal input to the LD. ) Will change. This is due to the fact that a semiconductor laser emits light based on the principle of stimulated emission using 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. ing. 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 is smaller. Conversely, the lower the excitation rate, the larger the proportion of spontaneous emission light amount and the noise. The amount gets bigger. Therefore, as shown in FIG. 7, the SN ratio between adjacent signal points of the signal to be determined is set to be non-linear by setting the step width to be large in the region where the level of the multilevel signal is small and small in the region where the level is large. Match.

  Even when an optical modulation signal is used as the modulation signal, the S / N ratio of the received signal is mainly determined by shot noise under the condition that the noise due to spontaneous emission and the thermal noise used in the optical receiver are sufficiently small. The Under such conditions, the greater the level of the multilevel signal, the greater the amount of noise. Therefore, contrary to the case of FIG. 7, in the region where the level of the multilevel signal is small, the step width is small, and in the region where the level is large. By setting it large, the signal-to-noise ratio between adjacent signal points of the signal to be determined is matched.

  As described above, according to the present embodiment, the information data to be transmitted is encoded as a multi-level signal, and the signal points are arranged substantially uniformly within the multi-level signal amplitude, or regardless of the instantaneous level. A safer data communication device that constantly degrades the received signal quality at the time of eavesdropping by a third party by making the signal-to-noise ratio between adjacent signal points substantially uniform, making it more difficult to decode and decode Can be provided.

(Fifth embodiment)
FIG. 8 is a block diagram showing a configuration of a data communication apparatus according to the fifth embodiment of the present invention. The data communication apparatus illustrated in FIG. 8 includes a transmission unit 20105 and a reception unit 20205. The transmission unit 20105 includes a multi-level encoding unit 111 and a modulation unit 112. The reception unit 20205 includes a demodulation unit 211 and a multi-level decoding unit 212. The multilevel encoding unit 111 includes a first multilevel code generation unit 111a, a first multilevel code string conversion unit 137, and a multilevel processing unit 111b. The multi-level decoding unit 212 includes a second multi-level code generation unit 212a, a second multi-level code string conversion unit 238, and a multi-level identification unit 212b. In the data communication apparatus shown in FIG. 8, the multi-level encoding unit 111 newly includes a first multi-level code sequence conversion unit 137, and the multi-level decoding unit 212 is a second multi-level code sequence conversion unit 238. Is different from the first data communication apparatus shown in FIG. In the data communication apparatus shown in FIG. 8, blocks that perform the same operations as those of the data communication apparatus shown in FIG.

  In the transmission unit 20105, the first multi-level code sequence conversion unit 137 uses the third key information 68 to convert the multi-level code sequence 12 having the bias level number M (M is an integer of 2 or more) to the bias level. Conversion into a converted multilevel code sequence 69 having a number N (N is an integer equal to or greater than 2 and N ≠ M). The number of bias levels is a parameter that determines the level interval of the multilevel code sequence. The level interval of the multilevel code sequence can be obtained from the number of bias levels and the maximum amplitude of the multilevel code sequence. Note that the first multi-level code sequence conversion unit 137 may determine the maximum amplitude of the converted multi-level code sequence 69 using the third key information 68. The first multi-level code sequence conversion unit 137 may output the maximum amplitude of the converted multi-level code sequence 69 substantially equal to the maximum amplitude of the multi-level code sequence 12 or output it as a different amplitude. Also good. In the following description, it is assumed that the maximum amplitude of the converted multilevel code sequence 69 and the maximum amplitude of the multilevel code sequence 12 are substantially equal.

  The multilevel processing unit 111 b generates the multilevel signal 13 using the converted multilevel code string 69 and the information data 10. The modulation unit 112 modulates the multilevel signal 13 into the modulation signal 14. The modulation unit 112 transmits the modulated signal 14 to the reception unit 20205 via the transmission path 110.

  In the reception unit 20205, the second multi-level code sequence conversion unit 238 uses the fourth key information 70 to convert the multi-level code sequence 17 having the bias level number M and the conversion multi-level code having the bias level number N. Convert to column 71. The fourth key information 70 is the same key information as the third key information 68. The demodulating unit 211 demodulates the received modulated signal 14 and outputs the multilevel signal 15 to the multilevel identifying unit 212b. The multi-level identifying unit 212 b reproduces the multi-level signal 15 into the information data 18 using the converted multi-level code sequence 71.

  The reception unit 20205 generates the same converted multi-level code sequence 71 as the converted multi-level code sequence 69 by sharing the same fourth key information 70 as the third key information 68 used by the transmission unit 20105. Can do. The third key information 68 and the fourth key information 70 are conversion key information for converting the multilevel code sequence 12 with the bias level number M into the converted multilevel code sequence 69 with the bias level number N. Therefore, the receiving unit 20205 can reproduce the information data 18 from the multilevel signal 15. On the other hand, since the third party who is an eavesdropper does not share the third key information 68 with the transmission unit 20105, the third party cannot reproduce the information data 18 from the multilevel signal 15.

  The conversion process of the multilevel code sequence 12 in the first multilevel code sequence conversion unit 137 in the transmission unit 20205 will be described in detail. The first multi-level code string conversion unit 137 determines the bias level number N based on the third key information 68. The first multi-level code sequence converter 137 calculates the maximum offset value from the difference value (N−M) of the number of bias levels between the multi-level code sequence 12 and the converted multi-level code sequence 69. The offset value is a parameter for assigning the bias level of the multilevel code sequence 12 to the bias level of the converted multilevel code sequence 69. The offset value changes every predetermined period. The first multi-level code sequence converter 137 generates a converted multi-level code sequence 69 having N bias levels by giving an offset value to the multi-level code sequence 12. The second multi-level code sequence converter 238 in the reception unit 20205 operates in the same manner as the first multi-level code sequence converter 137 and generates the converted multi-level code sequence 69, and thus the description thereof is omitted.

  FIG. 9 is a diagram for specifically explaining the conversion of the number of bias levels of the multi-level code sequence by the first multi-level code sequence converting unit 137. FIG. 9A is a diagram illustrating an example of the multilevel code sequence 12 with M = 128. FIG. 9B is a diagram illustrating an example of the converted multilevel code string 69 with N = 512. The unit of time in FIGS. 9A and 9B is a time slot. In the example shown in FIG. 9, the maximum value of the level of the offset signal is NM = 384. The first multi-level code string converter 137 generates an offset value whose value changes every predetermined period based on the maximum value 384 of the level of the offset signal. In the example shown in FIG. 9B, the offset value is 384 in the period A, 256 in the period B, 128 in the period C, and 0 in the period D. The first multi-level code sequence converter 137 changes the bias level of the multi-level code sequence 12 assigned to the bias level of the converted multi-level code sequence 69 by using different offset values for each period. In the example shown in FIG. 9A, the first multi-level code sequence converter 137 gives an offset value to the multi-level code sequence 12 with M = 128, and A converted multi-level code sequence 69 of N = 512 is generated. Although FIG. 9B shows an example in which the offset value decreases monotonously, the offset value in each period may be random. In the example illustrated in FIG. 9, the maximum amplitude of the multilevel code sequence 12 and the maximum amplitude of the converted multilevel code sequence 69 are substantially equal. For this reason, the level interval of the converted multilevel code sequence 69 is a quarter of the level interval of the multilevel code sequence 12.

  Since the multi-level processing unit 111b generates the multi-level signal 15 using the converted multi-level code string 69 and the information data 10, the multi-level signal 15 has the number of levels that can be taken by the multi-level signal (hereinafter referred to as the multi-level number). That is, the third key information 68 is included. For this reason, even if the third party intercepts the multi-level signal 15, the third party cannot determine the multi-level number of the multi-level signal 15, and therefore cannot decode it.

  FIG. 10 specifically shows the processing of the first multi-level code sequence converter 137 when the first multi-level code sequence generator 111a outputs the multi-level code sequence 12 by changing the number of bias levels. It is a figure explaining. FIG. 10A is a diagram illustrating an example of the multilevel code sequence 12 with M = 128. FIG. 10B is a diagram illustrating an example of the multilevel code sequence 12 with M = 12. FIG. 10C is a diagram illustrating an example of the N = 512 conversion multilevel code string 69. FIG. 10D is a diagram illustrating an example of the converted multilevel code string 69 with N = 24.

  FIGS. 10A and 10B show a state in which the first multi-level code sequence generator 111a outputs the multi-level code sequence 12 with the number of bias levels switched from 128 to 12 at time 20. FIG. Yes. 10 (c) and 10 (d) show that the first multi-level code sequence converter 137 converts the multi-level code sequence 69 at time 20 in accordance with the switching of the bias level number M of the multi-level code sequence 12. The state of changing the number of bias levels from 512 to 24 is shown. As described above, the first multi-level code sequence converter 137 changes the number of bias levels of the converted multi-level code sequence 69 in accordance with the change of the bias level number of the multi-level code sequence 12.

  As described above, according to the fifth embodiment, by using key information different from the key information used for generating the multi-level code sequence, the multi-level code sequence is changed to a bias level different from the number of bias levels of the multi-level code sequence. By converting the number into a converted multi-level code sequence and generating a multi-level signal using the converted multi-level code sequence and information data, the key information is included in the multi-level number of the multi-level signal. This makes it difficult to decode and decode the multilevel signal by a third party.

  In the fifth embodiment, the first multi-level code string converter 137 uses one key information (third key information 68) to determine the number of bias levels of the multi-level code string 12 and the conversion level. The description has been made assuming that conversion is performed in a one-to-one correspondence with the number of bias levels of the value code string 69. However, the first multi-level code sequence converter 137 uses two pieces of key information to convert a multi-level code sequence with a bias level number N1 (N1 is an integer of 2 or more) and a bias level N2 (N1 is 2 or higher). And N1 ≠ N2) may be alternately output. For example, when the multi-level code sequence 12 with M = 64 is input, the first multi-level code sequence conversion unit 137 converts the converted multi-level code sequence 69 with N = 128 or N = 256 every predetermined period. May be alternately output. Also, the number of key information used may be three or more. This makes it more difficult for a third party to select the multi-level number when multi-level identification of the multi-level signal, and thus makes it more difficult to decode and decode the multi-level signal.

(Sixth embodiment)
FIG. 11 is a block diagram showing a configuration of a data communication apparatus according to the sixth embodiment of the present invention. The data communication apparatus illustrated in FIG. 11 includes a transmission unit 20106 and a reception unit 20206. The transmission unit 20106 includes a multi-level encoding unit 111, a modulation unit 112, and a first power residue calculation unit 138. The reception unit 20206 includes a demodulation unit 211, a multi-level decoding unit 212, and a second power residue calculation unit 239. The multilevel encoding unit 111 includes a first multilevel code generation unit 111a, a first multilevel code string conversion unit 137, and a multilevel processing unit 111b. The multi-level decoding unit 212 includes a second multi-level code generation unit 212a, a second multi-level code string conversion unit 238, and a multi-level identification unit 212b. In the data communication apparatus shown in FIG. 11, the multi-level encoding unit 111 has a new first power residue calculation unit 138, and the multi-level decoding unit 212 has a second power residue calculation unit 239. This is different from the data communication apparatus shown in FIG. In the data communication apparatus shown in FIG. 11, blocks that perform the same operations as those of the data communication apparatus shown in FIG.

  In the data communication apparatus according to the sixth embodiment, the first power residue calculation unit 138 determines the bias level number N based on the third key information 68 and the multilevel code string 12. The first power residue calculation unit 138 outputs the determined bias level number N and the third key information 68 to the first multi-level code string conversion unit 137. The second power residue calculation unit 239 determines the bias level number N based on the fourth key information 70 and the multi-level code sequence 17, similarly to the first power residue calculation unit 138. The second power residue calculation unit 239 outputs the determined bias level number N and the fourth key information 70 to the second multi-level code string conversion unit 238. The first power residue calculation unit 138 and the second power residue calculation unit 239 perform the same operation. Therefore, in the following description, the operation of the first power residue calculation unit 138 will be described, and the description of the second power residue calculation unit 239 will be omitted.

（式１）において、ｅは第１の素数を表す。ｎは、第１の素数ｅと異なる２つの素数の積（以下、第１の積という）である。第１の素数ｅ及び第１の積は第３の鍵情報６８に格納されている。（式１）の演算について、図１１を用いて具体的に説明する。多値符号列１２のバイアスレベル数Ｍ（Ｍ＝１２８）を、第１の素数ｅ（ｅ＝７）でべき乗する。べき乗した結果を第１の積ｎ（ｎ＝５２７）で割った余りが、バイアスレベル数Ｎとなる。この結果、Ｎ＝５１２となる。第１の積（ｎ＝５２７）は、二つの素数“１７”と“３１”との積である。第１の多値符号列変換部１３７は、第１のべき乗剰余演算部１３８から出力されるバイアスレベル数Ｎと第３の鍵情報６８とに基づいて、多値符号列１２から変換多値符号列６９に変換する。 The first exponentiation remainder calculation unit 138 determines the bias level number N of the converted multilevel code sequence 69 based on (Equation 1).

In (Formula 1), e represents the first prime number. n is a product of two prime numbers different from the first prime number e (hereinafter referred to as the first product). The first prime number e and the first product are stored in the third key information 68. The calculation of (Expression 1) will be specifically described with reference to FIG. The bias level number M (M = 128) of the multilevel code string 12 is raised to the power of the first prime number e (e = 7). The remainder obtained by dividing the result of the exponentiation by the first product n (n = 527) is the number N of bias levels. As a result, N = 512. The first product (n = 527) is a product of two prime numbers “17” and “31”. The first multi-level code sequence conversion unit 137 converts the multi-level code sequence 12 from the multi-level code sequence 12 based on the bias level number N output from the first power residue calculation unit 138 and the third key information 68. Convert to column 69.

  FIG. 12 is a diagram illustrating a relationship between the number of bias levels M and the number of bias levels N based on the calculation result performed by the first power residue calculation unit 138. FIG. 12 shows a case where e = 7 and n = 527. As shown in FIG. 12, the number N of bias levels greatly depends on the number M of bias levels. In addition, the value of the bias level number N greatly depends on the value of the first prime number e and the value of the first product n. For this reason, the bias level number N changes in a complicated manner by switching the bias level number M and the prime numbers included in the third key information 68. Since the third party tries to identify the multilevel signal with respect to the multilevel signal generated by the converted multilevel code string having N bias levels, it becomes more difficult to select the multilevel number of the multilevel signal. The calculation shown in (Equation 1) uses a procedure of an encryption method called RSA public key cryptography, and from the public information (the number N of bias levels in (Equation 1)) to the secret information ((Equation 1) Therefore, it is mathematically derived that it is extremely difficult to derive the bias level number M).

  As described above, according to the sixth embodiment, by determining the number of bias levels of the converted multilevel code sequence using the procedure of the RSA public key method, the multilevel from the bias level number of the converted multilevel code sequence. Deriving the number of bias levels of the code string is extremely difficult. Therefore, it is very difficult for a third party to determine the multi-level number of the multi-level signal when decoding and decoding the multi-level signal. Therefore, a safer data communication device can be provided as compared with the data communication device according to the fifth embodiment.

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

1 is a block diagram showing a configuration of a data communication apparatus according to a first embodiment of the present 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 the structure of the data communication apparatus which concerns on the 2nd Embodiment of this invention. The block diagram which shows the structure of the data communication apparatus which concerns on the 3rd Embodiment of this invention. Schematic diagram illustrating transmission signal parameters of a data communication apparatus according to a fourth embodiment of the present invention. The block diagram which shows the structure of the data communication apparatus which concerns on the 5th Embodiment of this invention. It is a figure explaining concretely conversion of the number of bias levels of a multi-level code sequence. The figure which demonstrates the process of the 1st multi-value code sequence conversion part 137 concretely The block diagram which shows the structure of the data communication apparatus which concerns on the 6th Embodiment of this invention. The figure which shows the relationship between the bias level number M and the bias level number N Block diagram showing the configuration of a conventional data communication device

Explanation of symbols

10, 18 Information data 11, 16, 68, 70 Key information 12, 17 Multi-level code sequence 13, 15 Multi-level signal 14, 94 Modulated signal 69, 71 Conversion multi-level code sequence 110 Transmission path 111 Multi-level encoding unit 111a First multi-level code generation unit 111b Multi-level processing unit 112 Modulation unit 113 First data inversion unit 114 Noise control unit 137, 238 Multi-level code string conversion unit 138, 239 Power residue calculation unit 136 Key information selection unit 211 Demodulation Unit 212 multi-level decoding unit 212a second multi-level code generation unit 212b multi-level identification unit 213 second data inversion units 10101, 10102, 10103, 20105, 20106, 90001 data transmission devices 10201, 10202, 10205, 20205, 20206, 90002, 90003 Data receiving apparatus

Claims (14)

A data transmission device that performs encrypted communication,
A multi-level encoding unit that inputs predetermined predetermined key information and information data, and generates a multi-level signal whose signal level changes in a substantially random manner;
A data transmission apparatus comprising: a modulation unit that generates a modulation signal of a predetermined modulation format based on the multilevel signal. The multi-level encoding unit is
From the key information, a multi-level code generator that generates 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 string and the information data according to a predetermined process and generates a multi-level signal having a level uniquely corresponding to a combination of both signal levels. The data transmission device according to claim 1.   The multi-level encoding unit converts the multi-level code sequence into a converted multi-level code sequence having a bias level number different from the bias level number that determines the level interval of the multi-level code sequence, using conversion key information. The data transmission device according to claim 2, further comprising a multi-level code string conversion unit. The multi-level code generation unit outputs the multi-level code sequence in which the number of bias levels changes every predetermined period,
4. The data according to claim 3, wherein the multi-level code sequence conversion unit changes the number of bias levels of the converted multi-level code sequence in accordance with a change in the number of bias levels of the multi-level code sequence. Transmitter device.   The multi-level code sequence conversion unit converts the multi-level code sequence from the multi-level code sequence to the converted multi-level code sequence by using any one of the conversion key information for each predetermined key information use period. The data transmission device according to claim 3, wherein the data transmission device converts the data into the data transmission device.   The multi-level code sequence converting unit calculates at least one offset value for allocating the level of the multi-level code sequence to the level of the converted multi-level code sequence from the conversion key information, and for each predetermined allocation period 4. The level of the multi-level code sequence is assigned to the level of the converted multi-level code sequence by using any one of the at least one offset value. The data transmission device according to any one of 5. The conversion key information includes a first prime number and a multiplication value that is a product of a second prime number and a third prime number that are different from the first prime number, respectively.
The multi-level encoding unit calculates a power value obtained by raising the number of bias levels of the multi-level code string to a power of a first prime number, and a remainder obtained by dividing the power value by the multiplication value is calculated as the converted multi-level code string. The data transmission device according to claim 3, further comprising a modular exponentiation unit that should have the number of bias levels. A data receiving device for performing encrypted communication,
A demodulator that demodulates a modulated signal in a predetermined modulation format and outputs a multi-level signal;
A data receiving apparatus comprising: a multi-level decoding unit that inputs predetermined key information determined in advance and the multi-level signal and outputs information data. The multi-level decoding unit
From the key information, a multi-level code generator that generates a multi-level code sequence whose signal level changes in a substantially random manner,
The data receiving apparatus according to claim 8, further comprising: a multi-level identifying unit that identifies the multi-level signal based on the multi-level code sequence and outputs the information data.   The multi-level decoding unit converts the multi-level code sequence into a converted multi-level code sequence having a bias level number different from the bias level number for determining the level interval of the multi-level code sequence by using conversion key information. The data receiving device according to claim 9, further comprising a multi-level code string converting unit. The multi-level code generation unit outputs the multi-level code sequence in which the number of bias levels changes every predetermined period,
The data according to claim 10, wherein the multi-level code sequence converter changes the number of bias levels of the converted multi-level code sequence in accordance with a change in the number of bias levels of the multi-level code sequence. Receiver device.   The multi-level code sequence conversion unit converts the multi-level code sequence from the multi-level code sequence to the converted multi-level code sequence by using any one of the conversion key information for each predetermined key information use period. The data receiving device according to claim 10, wherein the data receiving device is converted into a data receiving device.   The multi-level code sequence converting unit calculates at least one offset value for allocating the level of the multi-level code sequence to the level of the converted multi-level code sequence from the conversion key information, and for each predetermined allocation period The multi-level code sequence level is assigned to the level of the converted multi-level code sequence using any one of the at least one offset value. The data receiving device according to any one of 12. The conversion key information includes a first prime number and a multiplication value that is a product of a second prime number and a third prime number that are different from the first prime number, respectively.
The multi-level encoding unit calculates a power value obtained by raising the number of bias levels of the multi-level code string to a power of a first prime number, and a remainder obtained by dividing the power value by the multiplication value is calculated as the converted multi-level code string. The data receiving apparatus according to claim 10, further comprising: a modular exponentiation unit that should have the number of bias levels.

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