JP5710521B2 - High security communication system and transmitter and receiver used therefor - Google Patents

Description

  The present invention relates to a high security communication system, and a transmitter and a receiver used therefor, and more particularly, to a communication system improved in safety in optical communication, and a transmitter and a receiver used therefor.

  Now that the world is connected by a network, safety (confidentiality) in communication is one of the important specifications required for communication systems. Based on this importance, research on quantum cryptography has been actively carried out (see, for example, Non-Patent Document 1). Quantum cryptography guarantees security in terms of physical laws and is considered the strongest from the viewpoint of security, but because its theoretical basis is based on quantum mechanics that dominates the microscopic world However, there are many restrictions for operation in a realistic environment, and it is difficult to introduce it into a normal optical communication system.

  In order to solve this problem, a “safe optical communication method using phase fluctuation” that balances safety and convenience has been devised (see, for example, Non-Patent Document 2). This method is characterized by the use of carrier light having a large phase fluctuation, and even if there is an eavesdropping by an unauthorized receiver due to the large phase fluctuation, information is not leaked sufficiently. It is assumed that the legitimate receiver shares a common key with the sender in advance, so that the legitimate receiver can extract a correct signal from a noisy signal.

  An authorized receiver can form a more advantageous situation than an unauthorized recipient by using a common key, but there is a bit error in the received signal even in the authorized receiver because a large fluctuation is introduced. Therefore, a parity check symbol is transmitted and received in addition to the signal, and error correction is performed at the receiver. Parity check symbols can be transmitted in addition to the signal sequence, or can be transmitted using a normal transmission path separately from the signal sequence (see, for example, Patent Document 1).

  "Safe optical communication method using phase fluctuation" uses the synergistic effect of common key and fluctuation. However, since the fluctuation is used as described above, error correction is an indispensable important technique. Therefore, the use of the parity check symbol, in other words, encoding / decoding is positioned as an important technique in this communication method. .

WO2010 / 103677 gazette

N. Gisin, G. Ribordy, W. Tittel and H. Zbinden, Rev. Mod. Phys. 74, 145-195 (2002) T. Tomaru, Jpn. J. Appl. Phys. 74, 074401 (2010)

  As described above, in a secure optical communication method using phase fluctuation, parity check symbols are transmitted and received for bit error correction. Since transmission / reception of signal sequences uses carrier light with large fluctuations, when transmitting / receiving parity check symbols in addition to the sequence of signals, there is a high possibility that a bit error will also occur in the parity check symbols. In this case, the error correction process in the receiver becomes complicated.

  On the other hand, when the parity check symbol is separated from the signal sequence and transmitted / received through a normal transmission path, it can be transmitted / received without error, but there is a possibility that information of the parity check symbol is surely known even to an unauthorized receiver This is not preferable from the viewpoint of improving communication safety. Ideally, it is desirable that the parity check symbols are transmitted and received accurately and that accurate information is not leaked to unauthorized recipients.

  Accordingly, an object of the present invention is to provide an optical communication method capable of achieving both signal processing ease and communication safety.

  The technical features of the transmitter and receiver of the present invention and the communication system using them are as follows.

  A parity check symbol is determined independently of the signal value using a common key shared between the sender and the receiver, and information on the parity check symbol is prevented from leaking to an unauthorized receiver. At this time, in order to determine the parity check symbol regardless of the signal value, an adjustment bit is added to the signal sequence so as to match the parity of the signal sequence so that the parity of the signal sequence matches the parity check symbol.

  Since the parity check symbol is determined using the common key, the parity check symbol can be shared between the sender and the receiver safely and reliably. This makes it possible to achieve both signal processing ease and communication safety.

The block diagram which showed the outline of the high security communication system by this invention. The block diagram which showed the outline of the protocol for performing high security communication. The figure which shows the signal state shown on the orthogonal coordinate (phase space). The figure which shows an example of the signal processing based on the high security communication system by this invention. The figure which shows the structural example for implement | achieving the high security communication system by this invention. The figure which shows an example of the signal processing based on the high security communication system by this invention. The figure which shows an example of the signal processing based on the high security communication system by this invention. The figure which shows an example of the signal processing based on the high security communication system by this invention. The figure which shows an example of the signal processing based on the high security communication system by this invention. The figure which shows an example of the signal processing based on the high security communication system by this invention.

  Hereinafter, embodiments will be described in detail with reference to the drawings.

  A basic form of the present invention is shown in FIG. The signal generated by the signal source 110 is transmitted from the transmitter 100 to the receiver 300 via the transmission path 200. In general, since a bit error occurs in the transmission path, an additional bit for error correction is necessary. This additional bit is called a parity check symbol. In the present invention, the common key 120 in the transmitter 100 and the common key 320 in the receiver 300 are shared in advance as a common key between the sender and the receiver, and a parity check symbol is generated using the common key. At that time, it is possible to use the common key as it is for the parity check symbol. It is also possible to generate a pseudo-random number based on the common key and use it as a parity check symbol.

  The parity check symbol is generated by the parity check symbol generator 125 using the common key 120 in the transmitter 100. In the receiver 300, the parity check symbol generator 325 generates a parity check symbol using the common key 320 that is the same as the common key 120. Since the parity check symbol is an additional bit for correcting a bit error of the signal, the parity check symbol should originally be generated based on the signal. However, in the present invention, the parity check symbol is generated by the signal source 110. Determined independently of

  For this purpose, adjustment bits relating the signal and the parity check symbol are added to the signal sequence. An introductory example is shown as Code Example 1 in the inset of FIG. Here, a case where a 1-bit adjustment bit is added to a 5-bit signal is shown. In the figure, the case where the first 5 bits of the signal sequence from the signal source 110 is “11010” is shown. The lower part of the signal of this code string 1 shows the value of the parity check symbol generated using the common key 120. In this example, it is “0”.

  Note that the parity of the target signal sequence is determined by the number of “1” appearing in the signal sequence. If the number of “1” is an even number, the parity is “0”, and if it is an odd number, the parity is “1”.

  In the example in the figure, since the first 5 bits of the signal sequence have three “1” s and become odd numbers, the parity is “1”. However, since the first value of the parity check symbol determined by the common key is “0”, the parity of both does not match.

  Therefore, an adjustment bit “1” is added to the sixth bit of the signal string. If a group of signal strings including the sixth bit is used, the number of “1” s is an even number and the parity is “0”, which matches the parity check symbol determined based on the common key. The same operation is repeated for the next signal “01010” after the first signal “11010”. Further, the same operation is performed every 5 bits of the signal train.

  After the above processing, the signal is transmitted from the transmitter to the receiver 300 through the transmission path 200. Any means such as an electric signal or an optical signal may be used as the transmission means. Also, it may be wired or wireless.

  In the receiver 300, the signal is received by the detector 310, and then the parity is calculated every 6 bits in the parity calculation unit. The same common key 320 as that in the transmitter 100 is prepared in advance in the receiver 300, and a parity check symbol is generated by the parity check symbol generation unit 325 through the same processing as in the transmitter 100 based on this common key. . This parity check symbol is compared with the previously calculated parity to determine whether there was a bit error during transmission. If the two parities do not match, one of the 6 bits of interest has a bit error.

  The above parity check symbol utilization method (encoding method) can detect up to a bit error but cannot correct it. In order to enable error correction, it is necessary to further increase the parity check symbols. One example is shown as Code Example 2 in another inset of FIG.

  The signal sequence is arranged in a matrix, a parity check symbol is assigned to each column in each row, and adjustment bits are added. This is a modification of encoding called horizontal / vertical code. If coded in this way, if there is a bit error in one place in each matrix, a bit error will occur in each of the row parity and column parity, and the error bit can be identified and corrected. become. Through this error correction, the signal is reproduced at the receiver.

  The use method (encoding method) of the above parity check code is a relatively rudimentary use method, and can be applied to the present invention if various encoding methods are similarly modified.

  In the first embodiment, the most rudimentary usage mode related to the present invention is described. However, the present invention related to the parity check symbol has various usage forms, and the effect of the present invention is exhibited particularly in the “safe communication method using fluctuation”. Therefore, in the following, an embodiment will be described mainly using optical communication as a specific example. Further, the phase fluctuation of the carrier light is taken up as the fluctuation. Of course, the present invention is applicable to intensity fluctuations, and is applicable not only to optical communication but also to general communication using an electric signal, and not only to wired communication but also to wireless communication.

  A secure optical communication protocol using phase fluctuation comprises three steps, as shown in FIG. 2, random number transmission / reception (key distribution) in the first step, and random number sequence transmitted / received in the second step. From private key generation and actual data encryption communication using the private key generated in the third stage (Non-Patent Document 2: T. Tomaru, Jpn. J. Appl. Phys. 74, 074401 (2010) reference). The second stage “secret key generation from transmitted / received random number sequence” is a logical operation in the transmitter / receiver, and reduces the number of bits of the transmitted / received random number sequence, thereby enhancing the security of the secret key (the confidentiality (Enhanced) (see CH Bennett, G. Brassard, C. Crepeau, and UU Maurer, “Generalized privacy amplification,” IEEE Trans. Inf. Theory 41, 1915 (1995)). In this protocol, a secret key is generated through the processing of the first stage and the second stage, so that the security is ensured. Therefore, the “cipher communication of actual data using the generated secret key” in the third stage It takes the same form as encryption communication.

  Here, normal encryption communication means that actual data is encrypted with a secret key and transmitted / received in a state where fluctuations in the transmission path are eliminated as much as possible. The third stage “Cryptographic communication of actual data using the generated secret key” is normal cryptographic communication, and sufficient safety is ensured. However, in order to ensure further safety, as in the first stage It is also possible to use light with fluctuations.

Next, the first stage key distribution will be described including the effect of fluctuation. FIG. 3A schematically shows signal states of phase 0 and phase π on orthogonal coordinates (this orthogonal coordinate system is called a phase space). The signal value of (0, π) is supposed to be on the a ₁ axis. However, in the “safe optical communication method using phase fluctuation”, the signal value has a phase fluctuation δθ, and therefore the signal value is It is not exactly (0, π) but (0 + δθ, π + δθ). As a result, the signal range of (0, π) becomes a crescent-shaped region as shown in FIG. 1A (note that δθ can take a positive or negative value). FIG. 3B shows a case where a phase of (π / 2, 3π / 2) is used as a signal value.

In the first stage key distribution, random numbers “0” and “1” are transmitted as phases 0 and π or phases π / 2 and 3π / 2. Which phase combination is used is determined randomly. The case where the phase of (0, π) is used is defined as base 0 (FIG. 3 (a)), and the case of using the phase of (π / 2, 3π / 2) is defined as base 1 (FIG. 3 (b)). . The signal random number is a binary value of (0, 1), and the random base is also a binary value of (0, 1), so it becomes a total of 4 values (FIG. 3 (c)).
In FIG. 3C, crescent-shaped regions (fluctuation ranges) overlap, which is the cause of bit errors.

  In the “safe optical communication method using phase fluctuation”, this bit error is used to secure a safe amount of information. In general, in order to secure a safe amount of information, it is necessary to make a legitimate recipient advantageous for an unauthorized recipient. Here, it is assumed that the legitimate receiver can receive a signal with a lower bit error rate than the unauthorized receiver. For this purpose, a common key shared in advance by the sender and the authorized receiver is used. The legitimate receiver uses this common key to reduce the influence of phase fluctuation, and receives with a low bit error rate. The following is a process for realizing it.

  The common key is mainly used for two purposes. One is for determining a basis called “shared basis”, and the other is for determining a parity check symbol which is the subject of the present invention.

  First, the shared base will be described. As described above, in key distribution, random numbers are transmitted and received using random bases (hereinafter referred to as “random bases”). Here, with the aim of preventing meaningful information leakage to unauthorized recipients, half of the random numbers to be transmitted and received are not used for secret key generation, but half are discarded after reception as a dummy. As a result, unauthorized recipients do not know where there is meaningful information. Random numbers that are transmitted and received by key distribution are both random numbers and dummy numbers that are actually used for secret key generation. Therefore, a random number used for generating a secret key is called a “signal random number” to distinguish it from a dummy. Which random number to transmit / receive is a signal random number and which is a dummy is determined by collating a shared basis determined by a common key with a random basis.

  FIG. 4 illustrates such a situation. In the left column of the transmitter shown in FIG. 4, a shared basis (common key), a random basis, a signal random number, a dummy, a transmission signal, and a parity check symbol are shown, and a bit string corresponding to each is shown in the right column. Yes. Each bit string is referred to as a first bit, a second bit,... In order from left to right. The receiver shown in FIG. 4 follows the same description as the transmitter, but is described separately when there is no error in the basis determination (upper right) and when there is an error (lower right).

  Looking specifically at FIG. 4, the first bit of the shared basis is “1” and the first bit of the random basis is “0” on the transmitter side. Since both bits do not match, a dummy random number is sent. As for the second bit, both the shared basis and the random basis are “1”, and a signal random number is transmitted. Thereafter, whether the signal random number or the dummy is determined is determined in the same manner. Since the transmission signal is determined by 2 bits, that is, 1 bit for the base and 1 bit for the random number, FIG. The allocation of four values is shown in the inset of FIG.

  The receiver performs the reverse process of the transmitter. First, a four-value transmission signal is received. The item “received signal” on the right side of FIG. The quaternary received signal includes base information, and the base is first determined. If the received signal is “0” or “2”, it is determined as base 0, and if it is “1” or “3”, it is determined as base 1. This determined basis corresponds to a “random basis”. The receiver holds a common key, which determines the “shared base”. As in the case of the transmitter, the random base and the shared base are compared to determine whether the random number on each bit is a signal random number or a dummy. On the receiver side in FIG. 4, only the signal random number is shown as the random number determination result, and the dummy is not shown. In the above processing, if the receiver can receive without error, the signal random number can be shared between the transmitter and the receiver.

  However, an error may actually occur in the received signal. In particular, the “safe optical communication method using phase fluctuation” is set to increase this error. An example in which there is an error in the received signal is shown in the lower right part of FIG. The underlined bit is incorrect. The place that should be “1” in the four-value judgment is “0”. As a result, data that should be dummy is determined as a signal random number. A parity check symbol is used to correct a determination error between the dummy and the signal random number.

  The parity check symbol is determined by a common key shared between the transceivers. However, since the parity is determined based on the data, the parity determined from the data and the parity determined from the common key generally do not match. Therefore, adjustment bits are inserted into the signal random number sequence so that both parities match. As an rudimentary example, FIG. 4 shows an example in which 5 bits of signal random numbers are grouped and an adjustment bit is added to the 6th bit.

  On the transmitter side in FIG. 4, the first five bits of the signal random number are composed of three “1” s and two “0” s, and the parity is “1”. However, the parity check symbol determined by the common key is “0”. Since both parities do not match, the adjustment bit “1” is inserted into the sixth bit (italic bit) of the signal random number sequence. Thereafter, in accordance with the same rule, a 1-bit adjustment bit is added to a 5-bit random number to form a signal random number sequence with 6 bits as a unit.

  If the receiver can receive without error, the signal random number sequence is reproduced. In the signal processing example in the upper right part of FIG. 4, the signal random number sequence on the transmitter side is reproduced. However, if there is a determination error, the signal random number sequence and the dummy random number sequence are erroneously determined as shown in the lower right part of FIG. In the example at the lower right in FIG. 4, the signal random number sequence is one bit extra. If the rule for processing the signal random number sequence every 6 bits is followed, the bit that should originally be the fifth bit of the random number becomes the adjustment bit. As a result, in the example at the lower right in FIG. 4, the parity (“1” because there are three “1”) and the parity check symbol “0” do not match. Since the shift of the adjustment bit position also occurs in all subsequent bits, the parity mismatch occurs with a probability of 1/2 after the position where the determination error has occurred. Therefore, it can be generally understood at which position there is a determination error.

  Therefore, the determination value is corrected for one of the received signals in the vicinity of the bit position where it is considered that there is a determination error, and the parity is checked by repeating all of the determinations of the random base and the shared base. If this process is executed sequentially for all the bits near the suspicious bit position, a correction in which all the parities substantially match can be found. In this way, the basis determination error is corrected.

  Through this correction of the base, the base at the time of key distribution is determined at the receiver. In other words, a legitimate recipient who shares the common key needs to determine only the binary value of the signal random number “0” or “1” at this time. Since the unauthorized receiver does not have the common key, the signal random number sequence and the dummy cannot be identified, and the determination result of the quaternary signal must be used as it is in the signal analysis. An unauthorized receiver must process a quaternary signal with respect to a legitimate receiver that can ultimately be processed as a binary signal. This difference is the source of safety in this method.

  In the above processing, the method of using the parity check symbol has been described by adding one adjustment bit for every 5 bits of the signal random number. However, this is a rudimentary usage to show the principle, and in fact, a more advanced usage of the parity check symbol is applicable. For example, as shown in the first embodiment, signal random number sequences are arranged in a matrix, and parity is checked in both the horizontal direction and the vertical direction. Although the discussion has so far been limited to the basis correction, a bit error with respect to the signal random number remains even if the basis correction is completed. Therefore, it is also useful to use another error correction code for signal random numbers. By doing so, even if the basis correction is insufficient and a slight basis determination error remains, it can be processed as a bit error.

A block diagram of a transceiver based on the above principle is shown in FIG. Note that balloons in the figure are explanatory texts corresponding to each item name such as “shared base” in the transmitter or receiver shown in FIG.
The transmitter 100 includes two common keys, a common key 1 (121) and a common key 2 (122), and a random number generator 1 (111), a random number generator 2 (112), and a random number generator 3 (113). Prepare a random number generator. However, two common keys can be used by dividing one common key into two, and three random number generators can be used by dividing the output of one random number generator into three. It is.

  The random number generator 1 (111) is a signal random number generation source. Due to fluctuations (noise), the signal random number sequence has an error when it is received, and the error is classified into a base determination error and a bit value error. To cope with bit errors, the encoder 141 performs error correction coding. A parity check symbol determined by the common key 2 (122) is used for base error handling. Since the parity check symbol is determined independently of the signal random number sequence, the parity of the signal random number sequence generally does not match the parity check symbol.

  Therefore, the adjustment bit insertion unit 126 adds adjustment bits to match both parities. The common key 2 can be used as it is, but it is also possible to generate a pseudo random number using the common key 2 as a seed key and use it as a parity check symbol. The signal random number to which the adjustment bit is added stands by in the buffer 131. The dummy is generated by the random number generator 2 (112) and waits in the buffer 132. The random base is determined by the output of the random number generator 3 (113), compared with the shared base determined by the common key 1 (121), and whether to send a signal random number or a dummy depending on whether both bases match. Decide. When both bases match, a standby signal random number is transmitted to the buffer 131, and when both bases do not match, a standby dummy is transmitted to the buffer 132.

  The signal random number and the dummy value are superimposed on the output light from the fluctuation light source 151 by the modulator 161. The fluctuation light source 151 is a light source that generates light accompanied by fluctuation (noise). As a fluctuation generation method, a method of expanding phase fluctuation by operating a laser diode (LD) in the vicinity of a threshold (Patent Document 1, and WO2011 / 099325), a method using anti-squeezing (see JP 2008-003339 A), and the like. It is also possible to prepare a fluctuation source (noise source) separately and superimpose the output of the fluctuation source on the output of the LD light to obtain a pseudo fluctuation light source (see Patent Document 1 and WO 2011/099325). . As a fluctuation source, a method using the output of a random number generator or thermal fluctuation, or an LD other than the one for transmission are prepared, the phase fluctuation of the LD light is temporarily received, and the electrical output is used as the fluctuation source output. A method of superimposing on the output light of the transmission LD is conceivable. The method of determining the shared base using the common key 1 can use the common key 1 as it is, or can generate a pseudo-random number using the common key as a seed key and use it as a shared base. is there.

  The signal light on which the signal random number and the dummy are superimposed is transmitted to the receiver through the transmission path 201. In the receiver, first, four-value determination is performed by the detector 311. A random basis is determined based on the determination result. The common key 1 (321) is held in the receiver and the shared base is determined. The common key 1 (321) is the same as the common key 1 (121) in the transmitter, and the shared base is the same in both the transmitter and receiver. The shared basis and the random basis are compared and separated into a signal random number and a dummy based on whether the basis of each bit matches or does not match. For the signal random number sequence, the parity is calculated according to the same rule as in the transmitter, and is checked using the parity check symbol determined by the common key 2 (322). If the inspection result is correct, it is determined that the group of signal random number sequences subjected to the inspection can be correctly reproduced. If the test result is incorrect, it is assumed that there is an error in the quaternary determination at the detector 311, and the result of the quaternary determination is corrected for one bit in the vicinity of the bit considered to have had the determination error. Repeat the process up to parity check. This iterative process is performed one by one with respect to the bits in the area considered to have a determination error to find a correct random basis. As a result, the base of each bit is determined.

  If the base is fixed, the signal random number can be determined by binary determination. However, it is expected that some determination errors remain in the base determination and that there are errors in the signal random number determination result. Therefore, error correction coding is performed by the encoder 141 on the transmitter side. In the receiver, the error correction code is decoded by the decoder 341.

  With the above processing, the signal random number output from the random number generator 1 (111) in the transmitter is reproduced in the receiver. As a result, the transmitter and the receiver hold the same random number. An object of the present invention is to transmit actual data safely. For this purpose, a secret key (encryption key) is required, and random numbers were transmitted and received in accordance with the above procedure in order to generate the secret key. When generating the secret key, a process of reducing the number of bits of the transmitted / received random number (reducing the amount of information) is performed. This is to enhance the security of the secret key (referred to as “enhancement of confidentiality”). For example, consider a process of generating a 1-bit secret key from 5 bits of 011010. One method is to take a 5-bit parity, in which case the secret key is “0”. The secret key generation process is performed according to the same rules for the transmitter and the receiver. As a result, the same secret key is generated in the transceiver.

  The actual data is encrypted with the secret key generated by the secret key generation unit 171 in the encryptor 181 in the transmitter. The encrypted actual data is converted into an optical signal by the optical transmission unit 182 and transmitted to the receiver 300 through the transmission path 202. In the receiver, the signal is converted into an electric signal by the detector 381, and converted into plaintext of actual data using the secret key generated by the secret key generation unit 371 in the decoder 382. This completes secure communication.

  In the second embodiment, an example of signal processing has been described with reference to FIG. There, signal random numbers and dummies were classified according to the match / mismatch of the shared basis and the random basis.

  However, there is a method for comparing the shared basis and the random basis other than the method shown in FIG. 4 (see Patent Document 1 and WO2011 / 099325). An example is shown in FIG. In this case, the signal random number and the dummy are classified according to the coincidence / mismatch of the shared basis and the random basis, but the difference is that the shared basis of the bit is reused in the next bit in the case of the mismatch.

  In FIG. 6, the first bit of the shared basis is “1” and the random basis is “0”. This bit is dummy because of mismatch. In determining the second bit, the first bit “1” of the shared basis is used again and compared with the second bit “1” of the random basis. Here, since they match, signal random numbers are used. If it is a signal random number, the shared base also advances to the next bit, and the second bit “0” of the shared base is compared with the third bit “0” of the random base. Since both bases match, this bit is also used as a signal random number. Proceed in the same manner.

  FIG. 6 shows an example in which one adjustment bit is added for every 5 bits of the signal random number, as in FIG.

  In the receiver, the signal random number and the dummy are classified by performing processing reverse to that of the transmitter as in the second embodiment. An example of the processing is shown in the upper right part of FIG. If there is no error in the quaternary determination in the receiver, the signal random number can be reproduced in this way, but if there is an error in the quaternary determination, the signal random number cannot be reproduced as shown in the processing example in the lower right part of FIG. In the example of FIG. 6, the determination is wrong with the second underlined bit. In this example, after the second bit, the signal random number sequence is completely different from the correct signal random number sequence. In the same manner as in the second embodiment, the change of the result of quaternary determination and the parity check are repeated for the neighboring bits estimated to have an error in the same manner as in the second embodiment to reproduce the random base.

  In Examples 2 and 3, the signal random number and the dummy were determined by comparing the shared basis and the random basis. This classification is one of the ways to use the common key, because it is a disadvantage for unauthorized recipients compared to legitimate recipients. In the second and third embodiments, the dummy is simply discarded, but the dummy is a random number similar to the signal random number, and this can also be used as a random number data group. That is, it is also possible to transmit the signal random number in the second and third embodiments as the signal random number 1 and the dummy as the signal random number 2 as a two-sequence signal random number sequence (see WO2011 / 099325). Examples of signal processing in that case are shown in FIGS. In FIG. 4 and FIG. 6, “signal random number” is rewritten as “signal random number 1” and “dummy” is rewritten as “signal random number 2”. 7 and 9, there are two signal random number sequences, but a parity check symbol is prepared only for the signal random number sequence 1. This is because the signal sequences 1 and 2 can be classified only by the parity check symbol for the signal random number sequence 1. However, a parity check symbol is also prepared for the signal random number sequence 2 for the purpose of improving the correction capability of the base and for the purpose of providing this parity check symbol with an error correction function for not only the base determination error but also the signal random value. There is also a way to do this. Examples of signal processing in that case are shown in FIGS. 8 is an extension of FIG. 7, and FIG. 10 is an extension of FIG.

  In the above, the specific example was described regarding the present invention which determines a parity check symbol using a common key. It is clear that this method is highly effective when applied to a safe optical communication method using fluctuations. In Examples 2, 3, and 4, it is assumed that a “safe optical communication method using phase fluctuations” is assumed. Examples have been described. However, the point of the present invention is that the parity check symbol is determined by the common key, and is not limited to application to a safe optical communication method using phase fluctuation. Further, the signal superimposing method is not limited to the phase modulation method, and can be applied to various methods such as an amplitude modulation method and a method combining amplitude modulation and phase modulation. However, in the case of the amplitude modulation method, the target fluctuation is amplitude fluctuation. Further, although the embodiments have been described assuming optical communication, the present invention can also be applied to various communication methods such as wireless communication.

100: transmitter,
110: signal source,
111, 112, 113: random number generator,
120, 121, 122: a common key,
125: Parity check symbol generator,
126: Adjustment bit insertion part,
131, 132: buffer,
141: Encoder,
151: Fluctuating light source,
161: modulator
171: Secret key generation unit,
181: Encryptor, 182: Optical transmitter,
200, 201, 202: transmission path,
300: Receiver,
310, 311: detector,
320, 321, 322: common key,
325: Parity check symbol generator,
341: decoder;
371: Secret key generation unit,
381: Detector, 382: Decoder.

Claims (15)

A signal source;
A parity check symbol generation unit that determines a parity check symbol using a common key shared between a transmitter including the signal source as a component and a receiver that receives a signal from the transmitter;
A transmitter comprising: an adjustment bit insertion unit that generates a signal sequence by adding an adjustment bit to the output sequence so that the parity of the output sequence from the signal source matches the parity check symbol.   The transmitter according to claim 1, wherein the signal source is a random number generator. A process for reducing the information amount of the random number sequence output by the random number generator, and outputting a random number sequence with the reduced information amount as a secret key;
An encryption device for encrypting real data with the secret key,
The transmitter according to claim 2, wherein the encrypted actual data is transmitted.   The transmitter according to claim 1, wherein fluctuation is superimposed on the signal sequence. The signal source comprises a random number generator;
The common key shared in advance with the receiver is divided into two to be a first common key and a second common key,
Dividing the random number generator into a first random number generator, a second random number generator, and a third random number generator;
Determining a shared basis based on the first common key;
A parity check symbol is determined by a parity check symbol generator using the second common key;
A signal sequence 1 is generated by the first random number generator;
A signal sequence 2 is generated by the second random number generator;
A random basis is determined by the output of the third random number generator;
By comparing the shared basis and the random basis, it is determined whether the value at each position of the signal sequence belongs to the signal sequence 1 or the signal sequence 2;
An adjustment bit is added to the at least one signal sequence so that the parity of at least one of the signal sequence 1 and the signal sequence 2 matches the parity check symbol;
The transmitter according to claim 1, wherein a combined signal sequence of the signal sequence 1 and the signal sequence 2 is transmitted by the random basis. A secret key generation unit that performs a process of reducing the amount of information of at least one of the signal sequence 1 and the signal sequence 2 and outputs the reduced signal sequence as a secret key;
An encryption device for encrypting real data with the secret key,
6. The transmitter according to claim 5, wherein the encrypted actual data is transmitted. A signal detector for detecting a signal train transmitted from the transmitter;
A parity calculator that calculates the parity of the signal detected by the signal detector;
A parity check symbol generator that determines a parity check symbol using a common key shared between a receiver that receives the signal sequence and the transmitter;
And a parity check unit that checks the parity calculated by the parity calculation unit using the parity check symbol. The common key shared in advance with the transmitter is divided into two as a first common key and a second common key,
Determining a shared basis based on the first common key;
A parity check symbol is determined by the parity check symbol generation unit using the second common key;
A random basis is determined from the reception result of the signal sequence obtained by the signal detection unit,
Classification of the signal sequence 1 and the signal sequence 2 is performed by comparing the random basis and the shared basis,
The parity check unit collates at least one parity of the signal sequence 1 and the signal sequence 2 with the parity check symbol,
If there is a parity error in the parity, the determination of the random basis is corrected,
Again, check the parity and repeat the correction of the random basis and the parity check until the correct parity is obtained,
The receiver according to claim 7, wherein a correct random basis and a correct signal sequence 1 and signal sequence 2 are obtained. A secret key generation unit that performs a process of reducing the amount of information of at least one of the signal sequence 1 and the signal sequence 2 and outputs the reduced signal sequence as a secret key;
The receiver according to claim 8, further comprising: a decrypting unit that decrypts actual data transmitted from the transmitter by using the secret key. A transmitter, a receiver, and a transmission path for transmitting a signal from the transmitter to the receiver;
The transmitter and the receiver share a common key;
The transmitter is
A signal source, a parity check symbol generation unit that determines a parity check symbol using the common key, and an adjustment bit in the output sequence so that the parity of the output sequence from the signal source matches the parity check symbol An adjustment bit insertion unit for adding and generating a signal sequence;
The receiver
A signal detector for detecting a signal transmitted from the transmitter;
A parity calculator that calculates the parity of the signal detected by the signal detector;
A parity check symbol generator that determines a parity check symbol using the common key;
And a parity check unit that checks the calculated parity using the parity check symbol. The signal source comprises a random number generator;
The common key shared in advance between the transmitter and the receiver is divided into two as a first common key and a second common key,
In the transmitter,
Dividing the random number generator into a first random number generator, a second random number generator, and a third random number generator;
Determining a shared basis based on the first common key;
A parity check symbol is determined by a parity check symbol generator using the second common key;
A signal sequence 1 is generated by the first random number generator;
A signal sequence 2 is generated by the second random number generator;
A random basis is determined by the output of the third random number generator;
By comparing the shared basis and the random basis, it is determined whether the value at each position of the signal sequence belongs to the signal sequence 1 or the signal sequence 2;
An adjustment bit is added to the at least one signal sequence so that the parity of at least one of the signal sequence 1 and the signal sequence 2 matches the parity check symbol;
Transmitting the combined signal sequence of the signal sequence 1 and the signal sequence 2 using the random basis;
In the receiver,
Determining a shared basis based on the first common key;
A parity check symbol is determined by a parity check symbol generator using the second common key;
A random basis is determined from the reception result of the signal sequence obtained by the signal detection unit,
Classification of the signal sequence 1 and the signal sequence 2 is performed by comparing the random basis and the shared basis,
The parity check unit collates at least one parity of the signal sequence 1 and the signal sequence 2 with the parity check symbol,
If there is a parity error in the parity, correct the determination of the random basis,
Again, the parity check is performed, and the correction of the random basis and the parity check are repeated until the correct parity is obtained,
The communication system according to claim 10, wherein a correct random basis and a correct signal sequence 1 and signal sequence 2 are obtained. In the transmitter and the receiver,
Performing a process of reducing the amount of information of at least one of the signal sequence 1 and the signal sequence 2, and using the reduced signal sequence as a secret key;
In the transmitter, the actual data is encrypted with the secret key and transmitted,
12. The communication system according to claim 11, wherein the receiver decrypts the actual data transmitted from the transmitter by using the secret key.   The communication system according to claim 10, wherein the signal source is a random number generator. A process for reducing the information amount of the random number sequence output by the random number generator, and outputting a random number sequence with the reduced information amount as a secret key;
An encryption device for encrypting real data with the secret key,
Communication system according to claim 13, wherein the signal to you route dark Goka signal.   The communication system according to claim 10, wherein fluctuation is superimposed on an output signal sequence from the transmitter.

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