JP2014120931A - Communication system, transmitter, receiver, and cipher communication method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To protect transmission data with high probability from a bit inversion attack in the middle of a communication path of a Y-00 cipher communication system.SOLUTION: A Y-00 cipher communication system includes: a transmitter 101 comprising a first memory or first operation unit (lookup table 106) for switching mapping between input transmission data 102 and Z types of signals in two or more ways on the basis of an M value pseudo random number sequence generated by a pseudo random number generator 103; and a receiver 151 comprising a second memory or second operation unit (lookup table 156) for mapping output of a signal identification unit 154 with reception data 155 on the basis of an M value pseudo random number sequence generated by a pseudo random number generator 153.

Description

  The present invention relates to a communication system, a transmitter, a receiver, and an encrypted communication method, and in particular, a communication path in a Y-00 protocol (optical communication quantum cryptography) using multilevel intensity modulation or multilevel phase modulation. The present invention relates to a technology for enhancing security against a tampering attack on communication data by an attacker on the way.

  The Y-00 encryption protocol is a common key encryption that makes it impossible for an eavesdropper to identify communication data by using 2M types of signals that cannot be accurately identified due to noise, thereby making it impossible to decrypt data even with infinite computational power. is there. In particular, non-removable noise called quantum noise, which is possessed by a coherent optical signal such as a laser, is often used.

  In this common key cryptosystem, a legitimate receiver is affected by noise by selecting M pairs (called communication bases) sufficiently separated from each other from 2M types of optical signals according to a predetermined procedure. Binary data can be transmitted and received. This communication base is determined by a common key shared in advance and a pseudo random number generator. On the other hand, an attacker who does not have a common key must receive 2M types of signals that cannot be accurately identified as described above, making it virtually impossible to decrypt communication data between authorized recipients.

  As a communication system that implements the Y-00 encryption protocol, for example, an optical phase modulation system disclosed in Non-Patent Document 1 and an optical intensity modulation system disclosed in Non-Patent Document 2 are known. .

  FIG. 10 shows an outline of the configuration of the Y-00 encryption communication system. According to FIG. 10, in the Y-00 encryption communication system, for example, a transmitter 101 that transmits an optical signal and a receiver 151 that receives an optical signal communicate via a communication path 100 such as an optical fiber. . The transmitter 101 includes a pseudo-random number generator 103, a communication base selection unit 104, and a signal transmitter 105.

  The pseudo-random number generator 103 generates an M-value running key by inputting the common key and outputs it to the communication base selection unit 104. The communication base selection unit 104 selects a communication base composed of M pairs based on the M-value running key generated by the pseudo random number generator 103 and outputs the communication base to the signal transmitter 105. In addition, transmission data 102 is input to the signal transmitter 105. The signal transmitter 105 generates a coherent optical signal or the like based on the transmission data 102 and the value selected by the communication base selection unit 104 (communication base made up of M pairs) and outputs it to the communication path 100. For example, the signal transmitter 105 generates a 2M-value optical phase signal in the optical phase modulation method and a 2M-value optical intensity signal in the light intensity modulation method.

  The receiver 151 includes a signal detector 152, a pseudorandom number generator 153, and a signal identification unit 154. Specifically, the signal detector 152 receives an optical phase signal or an optical intensity signal and outputs it to the signal identification unit 154. In addition, the same M-value running key based on the same common key as that of the transmitter 101 generated by the pseudorandom number generator 153 is input to the signal identification unit 154. The signal identification unit 154 decrypts the signal with a threshold value set based on the M-value running key output from the pseudorandom number generator 153, and generates the received data 155. Specifically, the signal detector 152 is a heterodyne receiver or the like in the optical phase modulation method, and an inexpensive direct detection general-purpose receiver other than the heterodyne receiver is used in the light intensity modulation method. There is.

  With reference to FIG. 11, an outline when an attacker performs wiretapping on the Y-00 encryption communication system having the above configuration will be described. As shown in FIG. 11, the authorized user communicates between the transmitter 101 and the receiver 151 via the communication path 100. On the other hand, the eavesdropper branches the signal of the transmitter 101 from the communication path 100 and receives it by the eavesdropper 251 and tries to eavesdrop on the encryption expressed by the optical signal.

FIG. 12 illustrates a 2M = 14 value light intensity modulation communication method. As shown in FIG. 12A, the regular sender determines the communication base B (k _t ) using the M-value running key k _{t at} time t. At this time, the base B (k _t ) is composed of optical signals having intensities S _min + k _t ΔS and S _min + (k _t + M) ΔS. Here, S _min is the lowest intensity, ΔS is the signal interval, and when k _t is an even number, the optical signal of intensity level S _min + k _t ΔS is transmitted data x _t = 0, intensity S _min + (k _t + M) When the optical signal of ΔS corresponds to x _t = 1 and _kt is odd, the optical signal of intensity S _min + k _t ΔS is the light of transmission data x _t = 1 and intensity S _min + (k _t + M) ΔS. Let the signal correspond to x _t = 0. As shown in FIG. 12 (b), the authorized receiver knows which base B (k _t ) is used for communication because the common key is shared with the authorized sender. for example the intensity _{S min + (k t + M} / 2) by setting the threshold [Delta] S, the intensity _S min + _{k t} optical signal and the intensity _{S min + (k t + M} ) ΔS signal to distinguish the [Delta] S, the transmission data x Decode _t . If the communication path 100 has a light intensity attenuation rate η, the threshold value may be η (S _min + (k _t + M / 2) ΔS).

On the other hand, the eavesdropper because no common key, does not know any of the communication base B (k _t) was used. For this reason, as shown in FIG. 12C, it is necessary for the eavesdropper to identify a 2M-value intensity signal. However, as described above, since the signal level cannot be correctly identified by the noise of the optical signal, an eavesdropper cannot read data between authorized senders and receivers.

Although not shown, the same applies to the optical phase modulation method. Specifically, a legitimate transmitter by M values running key k _t at time t, determining the communication base B (k _t). At this time, the base B (k _t ) is composed of optical signals of phase k _t Δθ radians and phase (k _t + M) Δθ radians. Here, Δθ = π / M is the signal interval, and when k _t is an even number, the optical signal of phase k _t Δθ radians is the transmission data x _t = 0, and the optical signal of phase (k _t + M) Δθ radians is x Corresponding to _t = 1, when k _t is an odd number, the optical signal of phase k _t Δθ radians k _t is the transmission data x _t = 1, and the optical signal of phase (k _t + M) Δθ radians is x _t = 0. It shall correspond.

For regular recipients shared with regular sender common key, knows whether the communication by using any of the base B (k _t) is performed, a phase _{(k t ± M / 2)} Δθ radians By setting a threshold value to, the signals of phase k _t Δθ radians and phase (k _t + M) Δθ radians are distinguished, and the transmission data x _t is decoded. On the other hand, the eavesdropper because no common key, does not know any of the communication base B (k _t) was used. For this reason, it is necessary for an eavesdropper to identify a 2M-value intensity signal. However, as described above, since the signal phase cannot be correctly identified due to the noise of the optical signal, an eavesdropper cannot read data between authorized senders and receivers.

  However, for example, in Non-Patent Document 3, the characteristics of an attack when an attacker in the middle of a communication path alters data by bit inversion of a signal were analyzed. In this attack, in the bit reversal attack, as shown in FIG. 13, the eavesdropper steals the signal of the transmitter 101 via the communication path 100a, and the bit reversal device 401 tries to invert the transmission data represented by the optical signal. After that, it is sent to the receiver 151 via the communication path 100b. When an eavesdropper such as a standard document can know transmission data in advance, the eavesdropper intends to send fake transmission data to an authorized receiver by this bit inversion attack. Although the light intensity modulation method can prevent bit inversion with a finite probability of 10% or less per bit of communication data, it is not sufficient to protect communication data from tampering by bit inversion. In addition, it is quite difficult to prevent bit reversal attacks in the optical phase modulation system.

S. Ozharar, DR Reilly, SX Wang, GS Kanter, and P. Kumar, “Two-dimensionaloptical code-division modulation with quantum-noise aided encryption for applications in key distribution,” IEEE. J. LightwaveTechnol. Vol. 29, No. 14, Jul. 15. 2011. K. Ohhata, O. Hirota, M. Honda, S. Akutsu, Y. Doi, K. Harasawa, and K. Yamashita, “10 Gb / s optical transceiver using the Yuen 2000 encryption protocol,” IEEE. J. Lightwave Technology , vol. 28, no. 18, pp2714-2723, Sep. 2010. Takehisa Iwakoshi, Osamu Hirota, “Examination of Tamper Resistance of Y-00 Quantum Stream Cipher”, IEICE Technical Report of IEICE Tech. Rep., Vol. 110, No. 281, ISEC2010-57 , pp 51-5, Nov. 2010

An outline of a bit reversal attack by an attacker is shown in FIG. Here, it is assumed that the signal attenuation in the communication channel 100a in FIG. 13 can be ignored, and the communication channel 100b has an attenuation factor η. In the optical phase modulation method shown in FIG. 14A, an eavesdropper successfully reverses communication data bits by rotating the signal phase by π radians in the middle of the communication path. On the other hand, in the light intensity modulation method shown in FIG. 14B, bit inversion is performed by amplifying only the intensity MΔS when the light intensity of the signal is less than or equal to the center intensity and attenuating only the intensity MΔS when the signal intensity is greater than or equal to the center intensity. Try. However, noise in the light intensity may cause the signal intensity to shift across the center intensity. For this reason, an error sometimes occurs in the attacker's signal inversion method, and as a result, the bit inversion of transmission data fails. However, even in the light intensity modulation method, if the 99.7% confidence interval of the probability distribution of noise is about 6ΓΔS in the intensity width, the eavesdropper fails in bit inversion because the intensity is S _min + (M ± It is only in the case of 3Γ) ΔS, and it is defenseless for most strengths.

  The present invention has been made to solve the above-described problems. For example, a communication system and a transmission that can protect transmission data with high probability from a bit reversal attack in the middle of a communication path of a Y-00 encryption communication system. It is an object to provide a receiver, a receiver, and an encrypted communication method.

  In order to solve the above-described problem, a communication system according to the first aspect of the present invention includes a communication base that forms a set of a common key and Z types of signals different from each other with respect to an integer Z of 3 or more, A pseudo-random number generator for outputting an M-value pseudo-random number sequence from the common key for an integer M greater than or equal to Z, and a signal transmitter for transmitting one signal from the communication base based on the output of the M-value pseudo-random number sequence A signal detector that receives the signal transmitted through a communication path, the common key, and a pseudorandom number that is the same as the M-value pseudorandom number sequence based on the common key A receiver comprising: a pseudo-random number generator that generates a sequence; and a signal identification unit that identifies which of the signals constituting the communication base is received based on the M-value pseudo-random sequence. It is a communication system. The communication system includes: a first memory that switches to the transmitter two or more correspondences between transmission data input based on the M-value pseudo-random number sequence and Z types of signals constituting the communication base; Alternatively, the apparatus further includes a first arithmetic unit, and the receiver further includes a second memory or a second arithmetic unit that associates an output of the signal identification unit with received data based on the M-value pseudorandom number sequence. It is characterized by.

  In the present invention, M of the M-value pseudorandom number sequence is at least equal to or greater than the factorial of Z, and the transmission data input to the transmitter is associated with the Z types of signals based on the M-value pseudorandom number sequence. The transmitter is provided with the first memory or the first arithmetic unit that switches to the Z factorial or less.

  In the present invention, M of the M-value pseudo-random number sequence is at least equal to or greater than the factorial of Z, and correspondence between transmission data input to the transmitter based on the M-value pseudo-random number sequence and a signal forming the communication basis 99.7% of the probability distribution of noise of the signal transmitted by the transmitter, wherein the transmitter includes the first memory or the first arithmetic unit that switches the z to the z-th order less than the factorial of Z. It is characterized in that z or more signals belong to the confidence interval.

  In the present invention, M of the M-value pseudo-random number sequence is at least equal to or greater than the factorial of Z, and the transmitter includes a Y-value pseudo-random number sequence for two or more Y different from the M-value pseudo-random number sequence, Based on the M-value pseudo-random number sequence and the Y-value pseudo-random number sequence, the correspondence between the transmission data input to the transmitter and the signal forming the communication basis is switched to z ways below the factorial of Z. 1 or a first arithmetic unit, and more than z / Y types of signals belong to a 99.7% confidence interval of a probability distribution of noise of a signal transmitted by the transmitter. .

  In the present invention, there are two or more signals corresponding to the same transmission data among the Z types of signals forming the communication base, and the first memory or the first arithmetic unit corresponds to the same transmission data. Selecting any one of the plurality of signals to be performed.

In the present invention, there are two or more signals corresponding to the same transmission data among the Z types of signals forming the communication base, and the maximum integer of Z / 2 or less is F, and the M-value pseudorandom number sequence M is at least _Z C _F or more, and the correspondence between the transmission data input to the transmitter and the Z types of signals forming the communication basis is switched to _Z C _F or more based on the M-value pseudorandom number sequence. The transmitter includes the first memory or the first arithmetic unit, and the first memory or the first arithmetic unit selects any one of a plurality of signals corresponding to the same transmission data. It is characterized by doing.

In the present invention, there are two or more signals corresponding to the same transmission data among the Z types of signals forming the communication base, and the maximum integer of Z / 2 or less is F, and the M-value pseudorandom number sequence M is at least _Z C _F or more, and the correspondence between the transmission data input to the transmitter based on the M-value pseudorandom number sequence and the Z types of signals forming the communication basis is _Z C _F or more c The transmitter includes the first memory or the first arithmetic unit that switches between the first memory and the first arithmetic unit, and the first memory or the first arithmetic unit is one of a plurality of signals corresponding to the same transmission data. One or more signals are selected, and c or more types of signals belong to the 99.7% confidence interval of the noise probability distribution of the signal transmitted by the transmitter.

In the present invention, there are two or more signals corresponding to the same transmission data among the Z types of signals forming the communication base, and the maximum integer of Z / 2 or less is F, and the M-value pseudorandom number sequence M is at least _Z C _F or more, and the transmitter includes a Y value pseudo random number sequence for two or more Y different from the M value pseudo random number sequence, the M value pseudo random number sequence, and the Y value pseudo random number sequence. and associating the switch to c as described above as _Z C _F the first memory or said first computation unit and Z types of signals forming the communication base with transmission data input to the transmitter based on The first memory or the first calculation unit selects any one of a plurality of signals corresponding to the same transmission data, and a probability distribution of noise of a signal transmitted by the transmitter Of 99.7% confidence interval of c / Y types or more The signal belongs to.

  In the present invention, the signal transmitter is a coherent light generator, and the signal forming the communication base is expressed by at least one of the intensity and phase of coherent light.

  A transmitter according to a second aspect of the present invention includes a signal detector that receives a signal transmitted via a communication channel, a common key, and a pseudorandom number that is the same as an M-value pseudorandom number sequence based on the common key. A pseudo-random number generator for generating a sequence, a signal identification unit for identifying which of the signals constituting the communication base is received based on the M-value pseudo-random number sequence, and the M-value pseudo-random number sequence A receiver including a second memory or a second arithmetic unit that associates an output of the signal identification unit with received data is a transmitter that communicates via the communication path. The transmitter includes a communication base that constitutes a set of the common key, Z types of signals different from each other for an integer Z of 3 or more, and an M-value pseudorandom number sequence for the integer M of Z or more. A pseudo-random number generator that outputs from the common key, a signal transmitter that transmits one signal from the communication base based on the output of the M-value pseudo-random number sequence, and an input based on the M-value pseudo-random number sequence A first memory or a first arithmetic unit that switches the correspondence between the transmission data and the Z types of signals forming the communication basis to two or more types is provided.

  The receiver according to the third aspect of the present invention provides a communication base comprising a common key, Z types of signals different from each other for an integer Z of 3 or more, and an integer M of Z or more. A pseudo-random number generator for outputting an M-value pseudo-random number sequence from the common key, a signal transmitter for transmitting one signal from a communication base based on the output of the M-value pseudo-random number sequence, and the M-value pseudo-random number sequence. A transmitter having a first memory or a first arithmetic unit that switches the correspondence between transmission data input based on Z-type signals forming the communication basis to two or more types via a communication path It is a receiver that communicates. The receiver generates a pseudo random number sequence that is the same as the M-value pseudo random number sequence based on the signal detector that receives the signal transmitted through the communication path, the common key, and the common key. A pseudo-random number generator for identifying the signal constituting the communication base based on the M-value pseudo-random number sequence, and the signal based on the M-value pseudo-random number sequence. A second memory or a second arithmetic unit that associates the output of the identification unit with the received data.

  The encrypted communication method according to the fourth aspect of the present invention is based on a common key, a communication base comprising a set of Z signals different from each other for an integer Z of 3 or more, and an integer M of Z or more. A transmitter comprising: a pseudo-random number generator that outputs an M-value pseudo-random number sequence from the common key; and a signal transmitter that transmits one signal from a communication base based on the output of the M-value pseudo-random number sequence; And a signal detector that receives the signal transmitted through the communication path, a pseudo random number generator that generates the same pseudo random number sequence as the M-value pseudo random number sequence based on the common key and the common key And a signal identification unit for identifying which of the signals constituting the communication base is received based on the M-value pseudo-random number sequence, is there. In the encrypted communication method, the transmitter associates the transmission data input to the transmitter on the basis of the M-value pseudorandom number sequence and the Z types of signals forming the communication basis into two or more types. The step of encrypting the transmission data by the first memory or the first arithmetic unit to be switched and transmitting the encrypted data through the communication path, and the receiver outputs the output of the signal identification unit based on the M-value pseudorandom number sequence And decrypting the encrypted transmission data by a second memory or a second arithmetic unit corresponding to the received data.

  According to the present invention, for example, a communication system, a transmitter, a receiver, and an encrypted communication method capable of protecting transmission data with high probability from a bit inversion attack in the middle of a communication path of a Y-00 encryption communication system. Can be provided.

It is a block diagram which shows the structure of the communication system which concerns on embodiment of this invention. FIG. 3 is a diagram illustrating an example (first embodiment) of a data structure of the lookup table in FIG. 1. FIG. 7 is a diagram illustrating an example (Example 2) of a data structure of the lookup table in FIG. 1. FIG. 8 is a diagram illustrating an example (third embodiment) of a data structure of the lookup table in FIG. 1. It is a block diagram which shows the modification of the communication system which concerns on embodiment of this invention. FIG. 10 is a diagram illustrating an example (Example 4) of the data structure of the lookup table in FIG. 1. FIG. 10 is a diagram illustrating an example (Example 5) of the data structure of the lookup table in FIG. 1. It is the figure which showed typically the difference between the reception method of the transmission data of the communication system which concerns on embodiment of this invention, and an eavesdropping method. It is the figure which showed typically the alteration attack with respect to the transmission data of the communication system which concerns on embodiment of this invention, and its failure reason. It is a block diagram which shows the conventional Y-00 encryption communication system structure. It is the figure quoted in order to demonstrate the outline | summary of the form which an eavesdropper eavesdrops on FIG. 10 and the communication system of this invention. It is the figure which showed the example of communication of the communication system of FIG. 10 using light intensity modulation, and an example of an eavesdropper signal of an eavesdropper. It is the figure quoted in order to demonstrate the outline | summary of the bit inversion attack with respect to FIG. 10 and the communication system of this invention. It is the figure quoted in order to demonstrate the outline | summary of the bit inversion attack by the attacker with respect to the communication system of FIG.

  Hereinafter, an embodiment for carrying out the present invention (hereinafter simply referred to as an embodiment) will be described in detail with reference to the accompanying drawings.

[Configuration of the embodiment]
FIG. 1 shows a configuration of a communication system according to the present embodiment. 10 differs from the conventional Y-00 encryption communication system shown in FIG. 10 in that the transmitter 101 has a lookup table 106 (first memory) and the receiver 151 has a lookup table 156 (second memory). It is in having added. The look-up tables 106 and 156 here refer to a data structure such as a memory array designed to improve efficiency by replacing the arithmetic processing with a simple array reference process. The data structure of these lookup tables 106 and 156 will be described later. Note that the look-up tables 106 and 156 may be replaced with calculations based on calculation formulas.

  Therefore, the transmitter 101 uses a common key, a communication base that constitutes a set of Z types of signals different from each other for an integer Z of 3 or more, and an M-value pseudorandom number sequence for an integer M of Z or more. A pseudo-random number generator 103 that outputs from the key, and a communication base selection unit 104 that selects a communication base composed of M pairs based on the M-value running key generated by the pseudo-random number generator 103 and outputs the communication base to the signal transmitter 105. , A signal transmitter 105 that transmits one signal from the communication base based on the output of the M-value pseudo-random number sequence, and Z types of signals that form a communication base with the transmission data 102 input based on the M-value pseudo-random number sequence, And a look-up table 106 for switching the correspondence between two or more. Here, the signal transmitter 105 is a coherent light generator, and the signal forming the communication base is expressed by at least one of the intensity and the phase of the coherent light.

  The receiver 151 communicates with the transmitter 101 via the communication path 100, receives a signal transmitted via the communication path 100, a common key, and a common key based on the common key. A pseudo-random number generator 153 that generates a pseudo-random number sequence that is the same as the M-value pseudo-random number sequence, and a signal identification unit that identifies which of the signals constituting the communication base is received based on the M-value pseudo-random number sequence 154 and a lookup table 156 that associates the output of the signal identification unit 154 with the received data based on the M-value pseudorandom number sequence. The received data is denoted by reference numeral 155.

[Operation of the embodiment]
The operation of the communication system according to this embodiment will be described in detail below. In the above configuration, the transmitter 101 determines the signal output from the signal transmitter 105 based on the output of the communication base selection unit 104 and the output of the lookup table 106. The output of the lookup table 106 is determined based on the transmission data 102 and the output of the pseudo random number generator 103. Further, the receiver 151 determines the output of the reception data output unit 155 based on the output of the lookup table 156. The output of the lookup table 156 is determined by the outputs of the signal identification unit 154 and the pseudorandom number generator 153. The data structure of the lookup table 106 held by the transmitter 101 and the look-up table 156 held by the receiver 151 determines the resistance against a bit reversal attack in the middle of the communication path 100 by an attacker. Below, the data structure is illustrated as Example 1-Example 5, and the tolerance with respect to each bit inversion attack is demonstrated.

Example 1
The data structures of the lookup table 106 and the lookup table 156 according to the first embodiment are shown in FIG. In the first embodiment, the same contents are stored in the lookup tables 106 and 156, and Z = 4 and M = 1024. First, what kind of signal the transmitter 101 used by a regular user outputs will be described by exemplifying a Y-00 encryption communication system using an intensity modulation method.

  The transmitter 101 is an encryption in which quaternary data is q as input transmission data 102, k is an M-value running key that is an output of the pseudorandom number generator 103, and LT (q, k) is an output of the lookup table 106. Data is generated and output to the signal transmitter 105. The notation of k mod 24 in the look-up table 106 indicates a remainder when k is divided by the factorial of 4 = 24. Receiving this, the signal transmitter 105 outputs a signal having the light intensity S (q, k) represented by the following arithmetic expression (1) to the receiver 151 via the communication path 100.

The receiver 151 uses the signal detector 152 to receive signal strength (RSSI: Received
Detect Signal Strength Indication. Moreover, the signal identification part 154 sets a threshold value using the following arithmetic expressions (2), (3), and (4), for example, and determines in which section RSSI exists.

  Then, the value of LT (q, k) is determined by comparing the RSSI detected by the signal detector 152 with the threshold value obtained by the calculation. If the value of k mod 24 of the lookup table 156 having the same data structure as that of the lookup table 106 of the transmitter 101 is referred to (compared) based on the LT (q, k) determined here, the receiver q The value can be restored immediately. Thus, by outputting the q value restored by the lookup table 156 as received data, the transmitter 101 of the authorized user and the receiver 151 of the authorized user can restore the q value without error. . Strictly speaking, since the signal strength attenuation rate η exists in the communication channel 100, the receiver 151 uses a value obtained by multiplying the equations (2), (3), and (4) by the attenuation factor η and the signal detector 152. Q is restored by comparing with the detected RSSI.

By the way, when an attacker tries to eavesdrop in accordance with the form shown in FIG. 11, the attacker does not know k, so the threshold values shown in the above arithmetic expressions (2), (3), and (4) cannot be set. Therefore, q cannot be restored. This is shown in FIG. FIG. 8 is a diagram schematically showing a difference between a transmission data reception method and an eavesdropping method. According to FIG. 8, for example, when q = 01 and k = 7, that is, when k mod 24 = 7, LT (q, k) = 0 is output. On the receiver 151 side, if the received signal strength is smaller than ηS ^Th1 (k), LT (q, k) = 0 is found, and therefore q = 01 is restored by referring to k mod 24 = 7. it can. Therefore, the authorized receiver can restore the value of q without error. On the other hand, since the eavesdropper does not know the value of k, the value of q cannot be restored.

  Next, FIG. 9 shows a case where an attacker receives a signal and manipulates the value of q according to the form shown in FIG. FIG. 9 is a diagram schematically showing a falsification attack on transmission data and the reason for the failure. Suppose that an attacker intends to invert q = 00 to q ′ = 01. Further, it is assumed that there is no signal attenuation rate of the communication path 100a and the signal intensity attenuation rate of the communication path 100b is η. In the case of k mod 24 = 8 or k mod 24 = 16, the attacker must use the bit inverter 401 to increase the signal strength by 3MΔS and send it to the communication path 100b. However, since the attacker does not know the value of k, when k mod 24 = 8 or k mod 24 = 16, the attacker must increase the signal strength by 3MΔS, but k mod 24 = 0, If k mod 24 = 12, the attacker must increase the signal strength by 1 MΔS, and if k mod 24 = 4 or k mod 24 = 20, q ′ = 01 is not obtained.

  As a result, the attacker has a high probability of failing to invert the bit from q = 00 to q ′ = 01. Especially when the 99.7% confidence interval of the noise probability distribution is 24ΔS or more, the attacker cannot specify the value of k mod 24, and the attacker fails to invert the bit with a probability of about 2/3. To do.

  The same applies not only to the above-described intensity modulation method but also to a phase modulation Y-00 encryption communication system. A phase modulation Y-00 encryption communication system will be described below. First, what kind of signal the transmitter 101 used by the authorized user outputs will be described. Here, it is assumed that the four-value data of the input transmission data 102 is q, the M-value running key that is the output of the pseudorandom number generator 103 is k, and the output of the lookup table 106 is LT (q, k). Further, Z = 4 and M = 1024. For example, when q = 00 and k = 32, that is, k mod 24 = 8, the lookup table 106 outputs LT (q, k) = 0. Assuming that the signal interval is Δθ = π / (2M), the signal transmitter 105 outputs a signal having a strong light phase θ (q, k) represented by the following arithmetic expression (5).

  Next, the receiver 151 detects the phase of this signal using the signal detector 152. Further, the signal identification unit 154 sets a threshold value represented by the following arithmetic expressions (6), (7), (8), and (9), and determines in which section the received signal phase exists.

Here, if the received signal phase is between θ ^Th4 (k) and θ ^Th1 (k), LT (q, k) = 0 is found. Further, a lookup table 156 that is the same as the lookup table 106 is obtained in advance based on the measured LT (q, k) value.
Compared with the case of mod 24 = 8, the value of q = 00 can be uniquely restored.

  On the other hand, when the attacker attempts to eavesdrop according to the form of FIG. 11, the attacker does not know k, so the threshold values shown in the above arithmetic expressions (6), (7), (8), and (9) are set. Therefore, q cannot be restored.

Next, consider a case where an attacker receives a signal and manipulates the value of q according to the form of FIG. Suppose now that the attacker wants to bit-shift q = 00 to q ′ = 01. In the case of k mod 24 = 8 or k mod 24 = 16, the attacker must use the bit inverter 401 to increase the signal phase by 3MΔθ and send it out to the communication path 100b. However, since the attacker does not know the value of k, in the case of k mod 24 = 8 or k mod 24 = 16, the attacker must increase the signal phase by 3MΔθ, but k mod
If 24 = 0 or k mod 24 = 12, the attacker must increase the signal phase by 1MΔθ, and if k mod 24 = 4 or k mod 24 = 20, the attacker must increase it by 2MΔθ. q ′ = 01 is not obtained. Therefore, the attacker will fail with high probability to bit-reverse q = 00 to q ′ = 01. If the 99.7% confidence interval of the noise probability distribution is greater than or equal to 24Δθ, in particular, the attacker will fail bit reversal with a probability of about 2/3.

(Example 2)
A communication system using the lookup table 106 (156) shown in FIG. According to the lookup table 106 (156) having the data structure shown in FIG. 3, for example, when q = 00 is inverted to q ′ = 11 or q ′ = 10, the probability of failure is halved. . However, if the bit is inverted from q = 00 to q ′ = 01, it will definitely succeed. Therefore, Example 1 is more suitable. That is, it is desirable that the 4th order permutation is arranged so that the values of LT (q, k) for the transmission signal q are all covered in the lookup tables 106 and 156. For example, when q is Z-value transmission data, it is preferable to cover Z factorials.

(Example 3)
When the additional binary pseudorandom number b is shared between the transmitter 101 and the receiver 151, the lookup table 106 (156) shown in FIG. 4 may be used. A communication system using the lookup table 106 (156) shown in FIG. 4 will be described below as a third embodiment. In the first embodiment, a 99.7% confidence interval of the probability distribution of noise is required by ΔS in the case of intensity modulation (Z factorial) ΔS and in the case of phase modulation (Z factorial) Δθ. In Example 3, the intensity modulation (Z factorial / 2) ΔS and the phase modulation (Z factorial / 2) Δθ are obtained, and therefore can be easily realized even when the quantum noise is small.

  In general, when b is a pseudo-random number of Y value, the intensity distribution (Z factorial / Y) ΔS and the phase modulation (Z factorial / Y) Δθ are necessary for the probability distribution of noise. It becomes a 99.7% confidence interval and can be realized more easily. At this time, the additional pseudo-random number b is supplied from the pseudo-random number generators 103 and 153 or, as shown in FIG. 5, the pseudo-random number generator 107 that generates a pseudo-random number from a common initial value and the pseudo-random number generator You may supply from the device 157.

  FIG. 5 is a block diagram showing a modification of the communication system according to the present embodiment. 1 is different from the embodiment of FIG. 1 in that a Y-value pseudo-random number sequence for two or more Y is generated in the transmitter 101 and the receiver 151 separately from the pseudo-random number generators 103 and 153 that generate an M-value pseudo-random number sequence. The Y-value pseudorandom number generators 107 and 157 are provided respectively. The pseudo random number generator 107 and the pseudo random number generator 157 generate pseudo random numbers from a common initial value and input the pseudo random numbers into the lookup tables 106 and 156, respectively. For this reason, for example, the lookup table 106 sets the correspondence between the transmission data 102 input to the transmitter 101 based on the M-value pseudo-random number sequence and the Y-value pseudo-random number sequence and the Z types of signals according to the factorial of Z. Switch to the following. The initial values of the Y-value pseudorandom number generators 107 and 157 may be a part of the common key.

  In the first, second, and third embodiments described above, it is effective when an attacker intends to bit-invert a specific q value to another specific q ′. If it is desired to bit-invert the value of q to a different q ′, this cannot be handled. In the following, methods that can cope with this case will be described in Embodiments 4 and 5.

Example 4
FIG. 6 shows the structure of the lookup table 106 (156) according to the fourth embodiment. In FIG. 6, x is binary transmission data, and r is a binary pseudorandom number that only the transmitter 101 has. Here, it is assumed that Z = 4 and M = 1024. In this case, the look-up tables 106 and 156 may be different as shown in FIG. 6A and FIG. 6B, respectively, but the communication device in which the transmitter 101 and the receiver 151 are integrated. In this case, it is preferable to unify the lookup table shown in FIG.

First, what kind of signal the transmitter 101 used by the authorized user outputs will be described by exemplifying the case of the intensity modulation Y-00 encryption communication system. Assume that the output of the lookup table 106 is LT (x, r, k). For example, when (x, r) = (0, 0) and k = 6, that is, k mod ₄ C ₂ = 0, the lookup table 106 outputs LT (x, r, k) = 0. (The notation of ₄ C ₂ is the number of combinations when selecting two from four.) Therefore, the signal transmitter 105 has a light intensity S (x, r, k) is output.

Next, the receiver 151 detects the RSSI of this signal using the signal detector 152. Further, for example, the signal identification unit 154 sets the threshold value indicated by the above-described arithmetic expressions (2), (3), and (4), and determines in which section the RSSI exists. If RSSI is smaller than S ^Th1 (k), LT (x, r, k) = 0 is found. As a result, in the lookup table 156 of FIG. 6A or FIG. 6B, k = 0, that is, x = 0 is immediately restored as compared with the case of k mod ₄ C ₂ = 0. it can. Therefore, the lookup table 156 of the receiver 151 outputs x = 0 to the reception data output unit 155. In this manner, the transmitter 101 of the authorized user and the receiver 151 of the authorized user can restore the value of x without error. Strictly speaking, since the signal strength attenuation rate η exists in the communication channel 100, the receiver 151 compares the value obtained by multiplying the arithmetic expressions (2), (3), and (4) by η with RSSI. Restore x.

  On the other hand, when the attacker attempts to eavesdrop according to the form of FIG. 11, the attacker does not know k, so the thresholds shown by the above-described arithmetic expressions (2), (3), and (4) cannot be set. x cannot be restored.

Next, consider a case where an attacker receives a signal and manipulates the value of x according to the case of FIG. Suppose that the attacker now wants to bit invert x = 0 to x ′ = 1. It is assumed that there is no signal attenuation rate of the communication channel 100a and the signal strength attenuation rate of the communication channel 100b is η. In this case, the attacker must use the bit inverter 401 to increase the signal strength by 2MΔS or 3MΔS and send it to the communication path 100b. However, this is true if the attacker knew k = 6. However, since the attacker does not know the value of k, in other cases the RSSI may have to be increased by 1MΔS or 3MΔS. In other cases, the signal strength may have to be increased by 1MΔS or 2MΔS. This makes the attacker with a high probability of bit-reversing x = 0 to x ′ = 1. Especially when the 99.7% confidence interval of the noise probability distribution is ₄ C ₂ ΔS or more, the attacker fails to invert the bit with a probability of about 1/3.

The same applies not only to the above-described intensity modulation method but also to a phase modulation Y-00 encryption communication system. First, what kind of signal the transmitter 101 used by the authorized user outputs will be described. Assume that the binary data of the input transmission data 102 is x, the M-value running key that is the output of the pseudorandom number generator 103 is k, and the output of the lookup table 106 is LT (x, r, k). For example, when x = 0 and k = 6, that is, when k mod ₄ C ₂ = 0, LT (q, k) = 0 is output. Assuming that the signal interval is Δθ = π / (2M), the signal transmitter 105 outputs a signal having a phase θ (x, r, k) represented by the following arithmetic expression (11).

Next, the receiver 151 detects the phase of this signal using the signal detector 152. Further, the signal identification unit 154 sets a threshold value represented by the above-described arithmetic expressions (6), (7), (8), and (9), and determines in which section the received signal phase exists. If the received signal phase is between θ ^Th4 (k) and θ ^Th1 (k), LT (x, r, k) = 0 is found. Further, if the look-up table 156 is compared with the previously known case of k mod ₄ C ₂ = 0, the value of x = 0 can be uniquely restored.

  On the other hand, when the attacker tries to eavesdrop according to the form of FIG. 11, since the attacker does not know k, the thresholds shown in the arithmetic expressions (6), (7), (8), and (9) can be set. Therefore, x cannot be restored.

  Next, consider a case where an attacker receives a signal and manipulates the value of x according to the form of FIG. Suppose an attacker intends to bit-invert x = 0 to x ′ = 1. In this case, the attacker must use the bit inverter 401 to increase the signal phase of the transmission data by 2MΔθ or 3MΔθ and send it to the communication path 100b. However, this is true if the attacker knew k = 6. However, since the attacker does not know the value of k, in other cases the signal phase may have to be increased by 1MΔθ or 3MΔθ. In still other cases, the signal strength may have to be increased by 1MΔθ or 2MΔθ.

This makes it highly probable that the attacker will bit flip x = 0 to x ′ = 1. Especially when the 99.7% confidence interval of the noise probability distribution is ₄ C ₂ Δθ or more, the attacker fails to invert the bit with a probability of about 1/3.

(Example 5)
However, when the additional binary pseudo-random number b is shared between the transmitter 101 and the receiver 151, the lookup tables 106 and 156 have the data structures shown in FIGS. 7A and 7B, respectively. May be. A communication system having the lookup tables 106 and 156 will be described below as a fifth embodiment.

The required noise width in the fourth embodiment is _Z C _F ΔS in the case of the intensity modulation method and _Z C _F Δθ in the case of the phase modulation method, whereas in the communication system according to the fifth embodiment, the width of the intensity modulation method is smaller. In the case of ( _Z C _F / 2) ΔS and in the case of the phase modulation method ( _Z C _F / 2) Δθ, it can be easily realized even when the 99.7% confidence interval of the noise probability distribution is small. In general, when b is a pseudo-random number of Y value, 99 ( _Z C _F / Y) ΔS in the case of the intensity modulation method and 99 ( _Z C _F / Y) Δθ in the case of the phase modulation method are required. .7% confidence interval, which can be realized more easily. At this time, the additional pseudo random number b is supplied from the pseudo random number generators 103 and 153, or, as shown in the modification of the communication system according to the present embodiment shown in FIG. May be supplied from the pseudo random number generator 107 and the pseudo random number generator 157. The initial values of the Y-value pseudorandom number generators 107 and 157 may be a part of the common key.

(Effect of embodiment)
As described above, according to the communication system according to the present embodiment, an attacker in the middle of the communication path fails to invert the bit of the signal with a probability of about 1/3. This is the same even if the attacker performs a bit flip without any special purpose. As described above, in the conventional optical phase modulation type Y-00 cryptographic communication system, since there is only one bit inversion method for an attacker, the bit inversion succeeds with a probability of almost 100%. On the other hand, in the conventional light intensity modulation type Y-00 encryption communication system, there are two methods of bit inversion for the attacker, so the attacker fails to invert the bit with a certain probability. Therefore, according to the communication system according to the embodiment of the present invention, it is possible to realize a Y-00 encryption communication system with enhanced resistance to a bit reversal attack by giving an attacker more options.

  In addition, according to the communication system according to the present embodiment, only the case where the quantum noise of the coherent light is used is illustrated, but the Y-00 encryption communication system using classical physical noise instead of the quantum noise is used. However, the same applies. For example, when the effect of quantum noise cannot be expected as in an electric circuit, a classical noise is superimposed by modulating a signal with a physical random number or a pseudo-random number, and a multivalue used in the Y-00 encryption communication system. The signal may be realized on an electronic circuit.

  Note that the transmitter 101 according to the present embodiment includes, for example, a signal detector 152 that receives a signal transmitted via the communication path 100, a common key, and an M based on the common key, as illustrated in FIG. A pseudo-random number generator 153 that generates the same pseudo-random number sequence as the value pseudo-random number sequence, and a signal identification unit 154 that identifies which of the signals constituting the communication base is received based on the M-value pseudo-random number sequence , And a receiver 151 including a second memory or a second arithmetic unit (lookup table 156) that associates the output of the signal identification unit 154 with the received data 155 based on the M-value pseudorandom number sequence. A transmitter 101 that communicates via a path 100. Then, the transmitter 101 transmits a M-value pseudorandom number sequence to an integer M greater than or equal to an integer M equal to or greater than Z, and a communication base that constitutes a set of Z types of signals different from each other for an integer Z greater than or equal to 3. Pseudorandom number generator 103 that is output from the common key, signal transmitter 105 that transmits one signal from the communication base based on the output of the M-value pseudorandom number sequence, and transmission data that is input based on the M-value pseudorandom number sequence And a first memory or a first arithmetic unit (lookup table 106) that switches the correspondence between the Z-type signal and two or more types.

According to the transmitter 101 according to the above-described embodiment, for example, transmission data can be protected with high probability from a bit reversal attack in the middle of a communication path of the Y-00 encryption communication system, and resistance to the bit reversal attack is enhanced. The transmitter 101 can be provided. For example, as shown in FIG. 5, an additional pseudo-random number generator 107 is further provided, and an additional Y-value pseudo-random number sequence is generated from an initial value common to the pseudo-random number generator 157 of the receiver 151 and looked up. Is input to the up-table 106, and the look-up table 106 associates the transmission data 102 input based on the M-value pseudo-random number sequence and the additional Y-value pseudo-random number sequence with the Z types of signals (Z floor). By switching to (multiplier / Y) or more, or switching to ( _{ZC F} / Y) or more, resistance to bit inversion attacks can be enhanced even when the quantum noise is small.

  In addition, the receiver 151 according to the present embodiment, for example, in FIG. 1, includes a common base, a communication base that forms a set of Z types of signals different from each other with respect to an integer Z of 3 or more, and an integer of Z or more. A pseudo-random number generator 103 that outputs an M-value pseudo-random number sequence from a common key to M, a signal transmitter 105 that transmits one signal from a communication base based on the output of the M-value pseudo-random number sequence, and an M-value pseudo A transmitter 101 including a first memory or a first arithmetic unit (lookup table 106) that switches the correspondence between transmission data input based on a random number sequence and Z types of signals to two or more types; Is a receiver 151 that receives a signal via the communication path 100. The receiver 151 receives a signal transmitted via the communication channel 100, a common key, and a pseudo-random number sequence that generates the same pseudo-random number sequence as the M-value pseudo-random number sequence based on the common key. A random number generator 153, a signal identification unit 154 for identifying which of the signals constituting the communication base is received based on the M-value pseudo-random number sequence, and a signal identification unit 154 based on the M-value pseudo-random number sequence A second memory or a second arithmetic unit (look-up table 156) that associates output with received data.

  According to the receiver 151 according to the above-described embodiment, for example, received data can be protected with high probability from a bit inversion attack in the middle of the communication path of the Y-00 encryption communication system, and the resistance to the bit inversion attack is enhanced. The receiver 151 can be provided. For example, as shown in FIG. 5, a pseudo random number generator 157 is further provided to generate an additional Y value pseudo random number b from a common initial value together with the pseudo random number generator 107 of the transmitter 101 to look up the table. The transmission data may be input to 156 and decoded. In the communication system according to the present embodiment, the transmitter 101 and the receiver 151 have been described as separate units. However, the present invention can be similarly applied to a communication device in which a transceiver is integrated.

  In addition, the encrypted communication method according to the present embodiment, for example, in FIG. 1, a communication base that forms a set with a common key and Z types of signals different from each other for an integer Z of 3 or more, A pseudo-random number generator 103 that outputs an M-value pseudo-random number sequence from a common key to an integer M; and a signal transmitter 105 that transmits one signal from a communication base based on the output of the M-value pseudo-random number sequence. Transmitter 101, signal detector 152 that receives a signal transmitted via communication channel 100, a common key shared with transmitter 101, and the same M-value pseudorandom number sequence based on this common key A receiver 151 including a pseudo random number generator 153 that generates a pseudo random number sequence, and a signal identification unit 154 that identifies which of the signals constituting the communication base is received based on the M-value pseudo random number sequence. Communication system consisting of It is a method. In the encrypted communication method, the transmitter 101 uses the first memory or the first calculation to switch the correspondence between the transmission data input based on the M-value pseudorandom number sequence and the Z-type signal to two or more. The transmission data is encrypted by the transmission unit (lookup table 106) and transmitted via the communication path 100, and the receiver 151 associates the output of the signal identification unit 154 with the received data based on the M-value pseudorandom number sequence. And decrypting the transmission data encrypted by the second memory or the second arithmetic unit (lookup table 156).

  According to the above-described encrypted communication method according to the present embodiment, an attacker in the middle of the communication path 100 fails to invert the bit of the signal with a high probability. This is the same even if the attacker performs a bit flip without any special purpose. Therefore, for example, it is possible to protect transmission data from a bit reversal attack in the middle of a communication path of a Y-00 cryptographic communication system with a high probability, and provide a Y-00 encrypted communication method with enhanced resistance to a bit reversal attack. be able to.

  As mentioned above, although preferred embodiment of this invention was explained in full detail, it cannot be overemphasized that the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above-described embodiments. Further, it is apparent from the scope of the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention.

  DESCRIPTION OF SYMBOLS 100, 100a, 100b ... Communication channel, 101 ... Transmitter, 102 ... Transmission data, 103 ... Pseudorandom number generator, 104 ... Communication base selection part, 105 ... Signal transmitter, 106 ... Look-up table (1st memory) , 107 ... pseudo random number generator, 151 ... receiver, 152 ... signal detector, 153 ... pseudo random number generator, 154 ... signal identification unit, 155 ... received data, 156 ... look-up table (second memory), 157 ... Pseudo random number generator, 251 ... Wiretap, 401 ... Bit reversal machine

Claims (12)

A common base, a communication base that forms a set of Z types of signals different from each other with respect to an integer Z of 3 or more, and a pseudo-value that outputs an M-value pseudorandom number sequence for the integer M of Z or more from the common key A transmitter comprising a random number generator, and a signal transmitter for transmitting one signal from the communication base based on the output of the M-value pseudo-random number sequence, and the signal transmitted via a communication path A signal detector to receive; a pseudo-random number generator that generates the same pseudo-random number sequence as the M-value pseudo-random number sequence based on the common key; and the communication based on the M-value pseudo-random number sequence In a communication system comprising a receiver comprising a signal identification unit for identifying which of the signals constituting the base is received,
To the transmitter,
A first memory or a first arithmetic unit that switches the correspondence between the transmission data input based on the M-value pseudo-random number sequence and the Z type signals to two or more,
In the receiver,
A second memory or a second arithmetic unit that associates an output of the signal identification unit with received data based on the M-value pseudo-random number sequence;
A communication system characterized by the above. M of the M-value pseudorandom number sequence is at least the factorial of Z;
The first memory or the first arithmetic unit that switches the correspondence between the transmission data input to the transmitter and the Z types of signals based on the M-value pseudorandom number sequence to the factorial of the Z or less. Providing the transmitter;
The communication system according to claim 1. M of the M-value pseudorandom number sequence is at least the factorial of Z;
The first memory or the first memory which switches the correspondence between the transmission data input to the transmitter and the Z types of signals based on the M-value pseudo-random number sequence to z ways below the factorial of Z The transmitter is provided with the transmitter,
The z or more types of signals belong to a 99.7% confidence interval of the probability distribution of noise of the signal transmitted by the transmitter;
The communication system according to claim 1. M of the M-value pseudo-random number sequence is at least the factorial of Z,
The transmitter is
Y value pseudo random number sequence for two or more Y different from the M value pseudo random number sequence,
Based on the M-value pseudo-random number sequence and the Y-value pseudo-random number sequence, the correspondence between the transmission data input to the transmitter and the Z types of signals is switched to the z-th order below the factorial of Z. 1 memory or the first arithmetic unit,
Z / Y or more types of signals belong to the 99.7% confidence interval of the noise probability distribution of the signal transmitted by the transmitter,
The communication system according to claim 1. There are two or more signals corresponding to the same transmission data among the Z types of signals forming the communication basis,
The first memory or the first arithmetic unit is
Selecting one of a plurality of signals corresponding to the same transmission data;
The communication system according to claim 1. There are two or more signals corresponding to the same transmission data among the Z types of signals forming the communication basis,
Let F be the largest integer less than or equal to Z / 2.
The M of the M-value pseudorandom number sequence is at least _Z C _F or more,
Based on the M-value pseudorandom number sequence, the first memory or the first arithmetic unit that switches the correspondence between transmission data input to the transmitter and Z types of signals to _Z C _F or more is transmitted. Ready for the machine,
The first memory or the first arithmetic unit is
Selecting one of a plurality of signals corresponding to the same transmission data;
The communication system according to claim 1. There are two or more signals corresponding to the same transmission data among the Z types of signals forming the communication basis,
Let F be the largest integer less than or equal to Z / 2.
The M of the M-value pseudorandom number sequence is at least _Z C _F or more,
The first memory or the first arithmetic unit that switches the correspondence between the transmission data input to the transmitter and the Z types of signals based on the M-value pseudo-random number sequence to c ways more than _Z C _F ways Provided in the transmitter,
The first memory or the first arithmetic unit is
Select one of multiple signals corresponding to the same transmission data,
C or more types of signals belong to the 99.7% confidence interval of the probability distribution of noise of the signal transmitted by the transmitter;
The communication system according to claim 1. There are two or more signals corresponding to the same transmission data among the Z types of signals forming the communication basis,
Let F be the largest integer less than or equal to Z / 2.
The M of the M-value pseudorandom number sequence is at least _Z C _F or more,
The transmitter is
Y value pseudo random number sequence for two or more Y different from the M value pseudo random number sequence,
Based on the M-value pseudo-random number sequence and the Y-value pseudo-random number sequence, the first to switch the correspondence between the transmission data input to the transmitter and Z types of signals to _Z C _F or more c ways or more. A memory or the first arithmetic unit,
The first memory or the first arithmetic unit is
Select one of multiple signals corresponding to the same transmission data,
C / Y or more types of signals belong to the 99.7% confidence interval of the probability distribution of noise of the signal transmitted by the transmitter;
The communication system according to claim 1. The signal transmitter is a coherent light generator;
The signal forming the communication basis is represented by one or more of the intensity or phase of coherent light;
The communication system according to any one of claims 1 to 8. A signal detector that receives a signal transmitted via a communication path; a common key; a pseudo-random number generator that generates a pseudo-random number sequence identical to an M-value pseudo-random number sequence based on the common key; and the M value A signal identifying unit for identifying which of the signals constituting the communication basis is received based on the pseudo-random number sequence, and a signal identifying unit that associates the output of the signal identifying unit with the received data based on the M-value pseudo-random number sequence. A receiver having two memories or a second arithmetic unit, and a transmitter that communicates via the communication path,
The common key;
A communication base constituting a set of Z types of signals different from each other for an integer Z of 3 or more;
A pseudorandom number generator that outputs an M-value pseudorandom number sequence from the common key for an integer M equal to or greater than Z;
A signal transmitter for transmitting one signal from the communication base based on the output of the M-value pseudorandom number sequence;
A first memory or a first arithmetic unit that switches the correspondence between transmission data input based on the M-value pseudorandom number sequence and the Z type signals to two or more,
A transmitter characterized by comprising: A common base, a communication base that forms a set of Z types of signals different from each other with respect to an integer Z of 3 or more, and a pseudo-value that outputs an M-value pseudorandom number sequence for the integer M of Z or more from the common key A random number generator, a signal transmitter for transmitting one signal from a communication base based on the output of the M-value pseudo-random number sequence, transmission data input based on the M-value pseudo-random number sequence, and Z types of signals A transmitter including a first memory or a first arithmetic unit that switches the correspondence between two or more types is a receiver that communicates via a communication path,
A signal detector for receiving the signal transmitted through the communication path;
The common key;
A pseudo-random number generator for generating a pseudo-random number sequence identical to the M-value pseudo-random number sequence based on the common key;
A signal identifying unit for identifying which of the signals constituting the communication base is received based on the M-value pseudorandom number sequence;
A second memory or a second arithmetic unit that associates the output of the signal identification unit with received data based on the M-value pseudorandom number sequence;
A receiver characterized by comprising. A communication base that forms a set of Z-type signals different from each other for a common key, an integer Z of 3 or more, and a pseudo-random number that outputs an M-value pseudo-random number sequence from the common key for an integer M of Z or more A transmitter including a generator and a signal transmitter that transmits one signal from a communication base based on an output of the M-value pseudo-random number sequence; and the signal transmitted through a communication path is received. A signal detector, the common key, a pseudo random number generator that generates the same pseudo random number sequence as the M value pseudo random number sequence based on the common key, and the communication base based on the M value pseudo random number sequence An encryption communication method of a communication system comprising a receiver including a signal identification unit that identifies which of signals constituting a signal is received,
The transmitter is
Based on the M-value pseudo-random number sequence, the transmission data is encrypted by the first memory or the first arithmetic unit that switches the correspondence between the transmission data input to the transmitter and the Z type signals to two or more. Transmitting via the communication path;
The receiver is
Decrypting the encrypted transmission data by a second memory or a second arithmetic unit that associates the output of the signal identification unit with received data based on the M-value pseudorandom number sequence;
An encrypted communication method characterized by comprising: