JP4879294B2 - Quantum cryptographic communication data processing method and quantum cryptographic communication device - Google Patents

Description

  The present invention generally relates to a secret key distribution technique used for cryptographic communication in the field of quantum cryptographic communication. More specifically, the present invention relates to a technique for suppressing bit errors in quantum cryptography communication and improving quantum key generation efficiency.

  Conventionally, quantum cryptography communication has attracted attention as a promising method for securely distributing a secret key required for a secret key cryptosystem. As typical quantum cryptography communication methods, a method called BB84 (see Non-Patent Document 1) and a method called B92 (see Non-Patent Document 2) of a quantum key distribution protocol are known.

  FIG. 1 is a diagram for schematically explaining the configuration of the quantum cryptography communication system. All quantum cryptography communication systems including the systems such as BB84 and B92 have the configuration shown in FIG.

  Referring to FIG. 1, the transmitter 100 randomly generates a bit value and modulates an optical pulse generated from a laser light source or a single photon source according to the value (that is, encodes a bit value). The optical pulse 130 is transmitted to the receiver 110 using a transmission line such as the optical fiber 120.

  On the other hand, the receiver 110 performs modulation (ie, decoding of the bit value) such that the modulation performed by the transmitter 100, that is, the bit value encoded by the transmitter 100 is read. The decoding of the bit value is performed by the modulator 111, the photon detector 112, and an electronic device that reads a signal output from the photon detector 112. After decoding, by using the public communication channel together, the transmitter 100 and the receiver 110 can obtain a raw bit string, respectively. In general, this raw bit string may not be safe due to the influence of noise and eavesdropping, and the bit string obtained by the transmitter 100 and the receiver 110 may contain bit errors. Here, “bit error” refers to an event in which the bit value transmitted by the transmitter 100 and the bit value received by the receiver 110 are different.

  The steps described above are commonly referred to as quantum communications, but additional steps described below must be performed to distill the secret key.

  First, some bit values of the raw bit string are disclosed. This disclosed bit string is called a test bit. By calculating the error rate in the test bit, the bit error rate of a bit string (referred to as a code bit string) other than the test bit is estimated.

  Next, based on the estimated bit error rate, a bit error correction protocol is first applied to the code bit string to convert the bit strings of the receiver and the transmitter into the same bit string. By performing a confidentiality enhancement protocol on the converted bit string, a secure secret key that is small enough to ignore information held by an eavesdropper is generated.

  In the sequence of steps for distilling the secret key, the parameter “bit error rate” plays an important role. The amount of information leaked to the eavesdropper can be estimated from this bit error rate, and if the bit error rate is large, the length of the secret key finally generated is shortened. If the bit error rate exceeds a certain value, a secret key cannot be generated at all. The “certain value” is a value depending on a specific bit error correction protocol, a confidentiality enhancement protocol, or the like.

  In general, the longer the distance, the higher the bit error rate due to the deterioration of the signal-to-noise ratio (SNR) of the signal. Therefore, in order to achieve safe communication over a long distance, the bit error rate needs to be as small as possible. Furthermore, even in the bit error rate area where the secret key can be distilled, if the bit error rate increases, the amount of communication consumed by the bit error correction protocol and the confidentiality enhancement protocol increases, so that the key generation rate decreases. . Therefore, it is necessary to reduce the bit error rate in order to achieve long distance in quantum cryptography communication and to improve the key generation speed.

C.H. Bennett, and G. Brassard, “Quantum cryptography: public key distribution and coin tossing”, Proceedings of IEEE International Conference of Computer Systems and Signal Processing, Bangalore, India (IEEE, New York) 175-179 (1984). C.H. Bennett, “Quantum cryptography using any two nonorthogonal states”, Physical. Review, Letters, 68, 3121 (1992).

Therefore, in order to achieve a long distance in quantum cryptography communication and to improve the key generation rate, the bit error rate must be reduced. In many quantum cryptography communications, it is known that the main cause of this bit error is a dark count at the detector. Here, the dark count refers to an event in which the detector emits an electrical signal even when no optical signal is input. While this dark count is thought to occur randomly in time, the electrical signal coming from the original photon signal occurs with higher probability as it is very close to time t _i . Here, t _i represents the time at which the receiver is supposed to receive the i-th signal.

Therefore, if only a signal very close to time t _i is selected, it is expected that the bit error rate is low, but the conventional method does not record the time when the electric signal is measured so accurately, and t _The signal received within _i ± Δt (Δt is a constant determined depending on the properties of the detector and the electric signal analyzer) was recorded as the signal of the i-th pulse. For this reason, the bit error rate has increased, and problems such as a decrease in key generation speed and a reduction in communication distance have occurred.

  Such a problem exists not only in the time but also in other parameters such as a signal intensity region and a signal waveform.

  As for the signal intensity region, for example, it is assumed that there is an electric signal analyzer that outputs a specific signal intensity when dark count occurs. In this case, since it is clear that the bit error rate of the signal that generated the specific signal strength is high, the bit value should be discarded, but the conventional method does not select the bit value based on the signal strength. For this reason, the bit error rate is also increased, causing problems such as a decrease in key generation speed and a reduction in communication distance.

  Similarly, assuming that there is an electrical signal analyzer that outputs a specific signal waveform when dark counting occurs, the same problem has occurred.

  The present invention has been made in order to improve the problems such as a decrease in key generation speed and a reduction in communication distance caused by the coarse graining of data processing as described above.

  In order to solve the above problems, a first method of quantum cryptography communication data processing between a transmitter and a receiver according to the present invention is as follows: (a) measuring a decrypted bit from signal light transmitted from a transmitter (B) determining which group the decoded bits belong to among groups generated according to predetermined parameters; and (c) a set including information of decoded bit values belonging to the same group. (D) dividing the set into two and transmitting a subset including bit values of one set to the transmitter; (e) a bit value set transmitted from the receiver; And calculating the bit error rate by comparing the bit value initially transmitted by the transmitter itself, selecting the bit value set for performing the key distillation process, and transmitting the bit value set to the receiver. It is characterized in.

  In order to solve the above problems, a second method of quantum cryptography communication data processing between a transmitter and a receiver according to the present invention is as follows: (a) Decryption bits from signal light transmitted from a transmitter And (b) determining which group of the groups generated according to the predetermined parameter the decoded bit belongs to; and (c) including information on decoded bit values belonging to the same group. Determining a set; (d) dividing the set into two and transmitting information on the position of a bit value in one set to the transmitter; and (e) bits transmitted from the receiver. Transmitting a bit value set corresponding to the position of the value to the receiver; and (f) comparing a bit value set transmitted from the transmitter with a bit value initially received by the receiver itself to detect a bit error. The rate was calculated, by selecting the bit value set to perform the key distillation process, characterized in that it comprises the steps of: transmitting the bit value set to the transmitter.

  A first quantum cryptography communication device including a transmitter and a receiver according to the present invention includes (a) means for measuring a decrypted bit from signal light transmitted from a transmitter, and (b) according to predetermined parameters. Means for determining which of the generated groups the decoded bits belong to; (c) means for determining a set including information of the decoded bit values belonging to the same group; and (d) the set Means for transmitting a subset including the bit values of one set to the transmitter, and (e) a subset including the bit values transmitted from the receiver and the transmitter itself Means for comparing the transmitted bit values to calculate a bit error rate, selecting a bit value set to be subjected to key distillation processing, and transmitting the bit value set to a receiver.

  A second quantum cryptography communication device including a transmitter and a receiver according to the present invention includes (a) means for measuring a decrypted bit from signal light transmitted from a transmitter, and (b) according to a predetermined parameter. Means for determining which of the generated groups the decoded bits belong to; (c) means for determining a set including information of decoded bit values belonging to the same group; and (d) the set Means for transmitting information on the position of the bit value in one set to the transmitter divided into two, and (e) receiving the bit value set corresponding to the position of the bit value transmitted from the receiver. (F) The bit value set transmitted from the transmitter and the bit value initially received by the receiver itself are compared to calculate the bit error rate, and the bit value set for performing the key distillation process is selected. The bit value collection Characterized in that it comprises a means for transmitting to the transmitter the.

  According to the present invention, bit data decoded by a receiver is appropriately grouped based on certain parameters (eg, time, signal strength, signal pattern, etc.) other than bit values, thereby suppressing the bit error rate. be able to. As a result, according to the present invention, it becomes possible to generate a key even at a distance where a key could not be generated by the conventional method, and it is possible to increase the distance of quantum cryptography communication, or an error correction protocol or a confidentiality enhancing protocol. Two effects can be obtained that the key generation speed can be improved by saving the amount of communication necessary for the communication.

It is a figure which illustrates schematically the structure of a quantum cryptography. It is two flowcharts which show the flow of the quantum cryptography communication data processing method concerning embodiment of this invention. It is a figure which shows the flow of an example of the data processing which concerns on the 1st Embodiment of this invention. It is a figure which shows an example of the grouping based on the time which concerns on the 1st Embodiment of this invention. It is a figure which shows an example of grouping based on the signal strength which concerns on the 2nd Embodiment of this invention. It is a figure which shows an example of the grouping based on the signal waveform which concerns on the 3rd Embodiment of this invention.

  FIG. 2A is a flowchart for explaining an outline of the quantum cryptography communication data processing method according to the embodiment of the present invention. In the description of FIG. 2A, the description will be made on the assumption that the period time of the operation clock of the transmitter 100 is T and the receiver 110 is synchronized with the period time T.

In step S210, the transmitter 100 encodes a random bit value B _i ^(s) within the i-th (i = 1, 2,..., N) period as described in FIG. Light is transmitted to receiver 110 through a channel (such as optical fiber 120) between transmitter 100 and receiver 110.

In step S220, the receiver 110 obtains the i-th cycle (where i∈D⊆ {1, 2,..., N}) corresponding to the time when the bit information is obtained from the received signal light. In this embodiment, the time when the i-th pulse is received is measured as accurately as possible. This time is measured using, for example, a TIA (Time Interval Analyzer). This measured time is defined as t _i + Δt _i . Here, t _i represents a time at which the receiver 110 receives the i-th signal, and Δt _i represents a deviation from t _i .

At step S230, the post-measurement, the receiver 110 classifies the bit value received in accordance with the value of Delta] t _i as illustrated in FIG. 3 into a plurality of groups. That is, constants a _{0,..., A N} are determined in advance so that the cycle time T can be divided into a plurality of groups, and if a _k ≦ Δt _i <a _{k + 1} , the i-th received bit value Is included in group k.

In step S240, the receiver 110 obtains the kth (k∈ {1, 2,..., N}) of the subsection obtained by dividing the time domain within each i-th period obtained in step S220. After that, bit values B _{i, k} ^(r) obtained in the i-th period and the k-th subsection are obtained.

In step S250, the receiver 110 converts the set {(B _{i, k} ^(r) , i, k)} _{i, k} including the bit values into elements (B _{i, k} ^(r) , i, k) is decomposed into sets S _k = {(B _{i, k} ^(r) , i, k)} _i , and each S _k element is randomly divided into two sets S _k ^(C) and Further decomposition into S _k ^(T) , two sets S ^(C) = {S _k ^(C) } _{k = 1,2,... N} and S ^(T) = {S _k ^(T) } _{k = 1, 2, ... n} is calculated. Thereafter, the receiver 110 receives a subset of S ^(T)

To the transmitter 100 through the public channel.

In step S260, the bit error rate _Ek is estimated individually for each group k. More specifically, the bit value belonging to each group is compared with the bit value encoded by the transmitter 100 with respect to the signal from which the bit value is obtained, and the ratio at which the bit value is different is calculated for each group.

  That is, the transmitter 100 first received

B _{i, k} ^(r) and B _i ^(s) included in the elements of are compared. Then, for each k, a bit error rate E _k obtained by the following equation is calculated.

Next, the transmitter 100 selects E _k for k, that is, discards a group having a bit error rate E _k that is so large that a key cannot be generated even if key distillation processing is performed. The threshold value (the above “certain value”) serving as a reference for this selection is a value depending on a specific bit error correction protocol, a confidentiality enhancement protocol, or the like. In other words, as described in the “Background Art” section, when the bit error rate is large, the length of the secret key that is finally generated is shortened, and when the bit error rate exceeds a certain value, the secret key is completely removed. Since it cannot be generated, a process of discarding a group having a bit error rate that is too large to generate a key is performed. After this selection, let F be the set of remaining groups. Thereafter, the transmitter 100 transmits the set F of k to be adopted to the receiver 110 through the public channel.

  Then, as shown in FIG. 3, a key distillation process, that is, a bit error correction protocol and a confidentiality enhancement protocol is performed for each group in F.

A secret key is generated individually for each k.

From another point of view, this embodiment will be described with reference to the length of each group, that is, the constant a _0, so that the sum of secret keys to be finally generated is maximized, as shown in FIG. _..., a _N is determined. That is, the length of each group in the time domain is determined so that the key generation rate is maximized. Note that the grouping shown in FIG. 4 is merely a conceptual diagram, and the length shown in FIG. 4 can be determined by specific experimental results. In FIG. 4, the times when the first and second pulses are supposed to be received are written as t ₁ and t ₂ , respectively, and six groups are formed.

  As described above, according to the present embodiment, instead of obtaining the bit error rate by simple coarse-graining, it is possible to select the elite selection from each group, that is, the one with a higher key generation rate. Distance and key generation speed can be improved.

  FIG. 2B is a flowchart explaining an outline of the quantum cryptography communication data processing method according to the embodiment of the present invention. The difference between the above embodiment and the present embodiment is that the type of information that the receiver 110 sends to the transmitter 100 in step S250 in FIG. 2 and the transmitter 100 sends bit information to the receiver 110 after receiving this information. The receiver 110 calculates the bit error rate and performs elite selection, and the others are the same. Therefore, step S240 and subsequent steps will be described below.

In step S250b, the receiver 110 converts the set {(B _{i, k} ^(r) , i, k)} _{i, k} including bit values into elements (B _{i, k} ^(r) , i, k) is decomposed into sets S _k = {(B _{i, k} ^(r) , i, k)} _i , and each S _k element is randomly divided into two sets S _k ^(C) and Further decomposition into S _k ^(T) , two sets S ^(C) = {S _k ^(C) } _{k = 1,2,... N} and S ^(T) = {S _k ^(T) } _{k = 1, 2, ... n} is calculated. Thereafter, the receiver 110

To the transmitter 100 through the public channel.

  In step S260b, the set received from the receiver 110

Bit information corresponding to

Is transmitted to the receiver 110 through the public channel.

To estimate the individual bit error rate _{E k} relative to step S270b in each group k. More specifically, the bit value belonging to each group is compared with the bit value encoded by the transmitter 100 with respect to the signal from which the bit value is obtained, and the ratio at which the bit value is different is calculated for each group.

  That is, the receiver 110 first received

B _i ^(s) and B _{i, k} ^(r) included in the elements of are compared. Then, for each k, a bit error rate E _k obtained by the following equation is calculated.

Next, the receiver 110 selects E _k for k, that is, discards a group having a bit error rate E _k that is so large that a key cannot be generated even if key distillation processing is performed. The threshold value (the above “certain value”) serving as a reference for this selection is a value depending on a specific bit error correction protocol, a confidentiality enhancement protocol, or the like. In other words, as described in the “Background Art” section, when the bit error rate is large, the length of the secret key that is finally generated is shortened, and when the bit error rate exceeds a certain value, the secret key is completely removed. Since it cannot be generated, a process of discarding a group having a bit error rate that is too large to generate a key is performed. After this selection, let F be the set of remaining groups. Thereafter, the receiver 110 transmits the set F of k to be adopted to the transmitter 100 through the public channel.

  Then, as shown in FIG. 3, a key distillation process, that is, a bit error correction protocol and a confidentiality enhancement protocol is performed for each group in F.

A secret key is generated individually for each k.

From another point of view, this embodiment will be described with reference to the length of each group, that is, the constant a _0, so that the sum of secret keys to be finally generated is maximized, as shown in FIG. _..., a _N is determined. That is, the length of each group in the time domain is determined so that the key generation rate is maximized. Note that the grouping shown in FIG. 4 is merely a conceptual diagram, and the length shown in FIG. 4 can be determined by specific experimental results. In FIG. 4, the times when the first and second pulses are supposed to be received are written as t ₁ and t ₂ , respectively, and six groups are formed.

  As described above, according to the present embodiment, instead of obtaining the bit error rate by simple coarse-graining, it is possible to select the elite selection from each group, that is, the one with a higher key generation rate. Distance and key generation speed can be improved.

  The only difference between the above two embodiments and this embodiment is the grouping method performed in step S230. That is, in the above embodiment, time is grouped as a parameter, but in this embodiment, grouping is performed using a pulse signal intensity as a parameter. In the following description, differences from the above-described embodiment will be mainly described.

In step S220, the receiver 110 measures the signal intensity (light intensity) of the i-th pulse as accurately as possible. This measured signal strength is defined as A _i . In step S230, the receiver 110 divides the signals into a plurality of groups according to the value of A _i as shown in FIG. That is, constants a _{0,..., A N} are determined in advance, and if a _k ≦ A _i <a _{k + 1} , the i-th signal is included in group k. FIG. 5 is a diagram illustrating an example in which grouping is performed based on signal strength, and b _i represents an i-th obtained bit value.

Thereafter, as described in step S260 in FIG. 2 and step 270b in FIG. 2B, the bit error rate E _k is individually estimated for each group k, and after elite selection, a key is set for each group. By performing the distillation process, it is possible to select those having a higher key generation rate. As a result, according to the present embodiment, it is possible to increase the distance of quantum cryptography communication and improve the key generation speed.

  The only difference between the above three embodiments and the present embodiment is the grouping method performed in step S230. That is, in the above embodiment, time and signal intensity are grouped as parameters, but in this embodiment, pulse signal waveforms are grouped as parameters. In the following description, differences from the above-described embodiment will be mainly described.

In step S220, the receiver 110 first records the signal waveform of the i-th pulse. This signal waveform is expressed as a function of time, and the function is A _i (t). Here, it is assumed that the function A _i (t) is defined over 0 ≦ t ≦ T, where 0 is the time when the i-th signal starts to be measured and T is the time when the measurement ends. The signal waveform obtained is divided into a plurality of blocks according to the function form. That is, signal waveforms a ₀ (t) _{,..., A N} (t) are determined in advance, and A _i (t) is any of the signal waveforms from a ₀ (t) to a _N (t). Calculate the closest.

The definition of “closeness” may be any definition, but as an example, the closeness d _ik between A _i (t) and a _k (t) can be defined as the following equation.

If A _i (t) is closest to a _k (t), in step S230, a process of including the i-th signal in group k is performed. FIG. 6 shows an example in which grouping is performed based on signal waveforms. b _i represents the i-th obtained bit value.

Then, as described in step S260 and step 270b in FIG. 2B, the bit error rate E _k is individually estimated for each group k, and after performing elite selection, a key distillation process is performed for each group. By doing so, it is possible to select those having a higher key generation rate. As a result, according to the present embodiment, it is possible to increase the distance of the quantum cryptography communication and improve the key generation speed.

DESCRIPTION OF SYMBOLS 100 Transmitter 110 Receiver 111 Modulator 112 Photon detector 120 Optical fiber 130 Optical pulse

Claims (12)

A quantum cryptography communication data processing method between a transmitter and a receiver,
(A) measuring a decoded bit from signal light transmitted from a transmitter;
(B) determining which of the groups generated according to the predetermined parameter the decoded bit belongs to;
(C) obtaining a set including information of decoded bit values belonging to the same group;
(D) dividing the set into two and transmitting a subset including bit values of one set to the transmitter;
(E) A bit error rate is calculated by comparing a subset including a bit value transmitted from a receiver with a bit value initially transmitted by the transmitter, and a bit value set for performing a key distillation process is selected and the bit is selected. Transmitting a set of values to a receiver. The transmitter and the receiver are synchronized with a period time T of an operation clock of the transmitter,
Before the step (a), the transmitter transmits a signal light including a random bit value B _i ^(s) encoded within the i-th (i = 1, 2,..., N) period. Further comprising transmitting to the receiver;
The group is generated by dividing the periodic time based on a predetermined time interval;
In the step (b), when the time when the decoded bit is received belongs to the k-th group (kε {1, 2,..., N}) among the groups in the i-th period, Further comprising determining the value of the decoded bit as a bit value B _{i, k} ^(r) ,
In step (d), a set {(B _{i, k} ^(r) , i, k)} _{i, k} including bit values is _converted into elements (B _{i, k} ^(r) , i, k) is decomposed into sets S _k = {(B _{i, k} ^(r) , i, k)} _i
Each S _k element is randomly further broken down into two sets S _k ^(C) and S _k ^(T) ,
Two sets _{^{S (C) = {S k}} (C)} k = 1,2, ... n and _{^{S (T) = {S k}} (T)} k = 1,2, calculate the _{... n,} S ^{( A} subset of ^T)

Transmitting to the transmitter via the channel, and
The step (e) includes the set transmitted from the receiver.

The B _{i, k} ^(r) and B _i ^{(s) included in} are compared, and a bit error rate E _k is calculated for each k based on the following equation:

Further comprising: selecting E _k for k, and transmitting the selected set of k F to the receiver over the channel;
The method
Using the set F transmitted from the transmitter, set

2. The quantum cryptography communication data processing method according to claim 1, further comprising the step of individually generating a secret key for each k. The transmitter and the receiver are synchronized with a period time T of an operation clock of the transmitter,
Before the step (a), the transmitter transmits a signal light including a random bit value B _i ^(s) encoded within the i-th (i = 1, 2,..., N) period. Further comprising transmitting to the receiver;
The group is generated based on a predetermined signal strength,
In the step (b), when the signal strength of the decoded bit measured in the step (a) belongs to the k-th group (kε {1, 2,..., N}) among the groups, Further comprising determining the value of the decoded bit as a bit value B _{i, k} ^(r) ,
In step (d), a set {(B _{i, k} ^(r) , i, k)} _{i, k} including bit values is _converted into elements (B _{i, k} ^(r) , i, k) is decomposed into sets S _k = {(B _{i, k} ^(r) , i, k)} _i
Each S _k element is randomly further broken down into two sets S _k ^(C) and S _k ^(T) ,
Two sets _{^{S (C) = {S k}} (C)} k = 1,2, ... n and _{^{S (T) = {S k}} (T)} k = 1,2, calculate the _{... n,} S ^{( A} subset of ^T)

Transmitting to the transmitter via the channel, and
The step (e) includes the set transmitted from the receiver.

The B _{i, k} ^(r) and B _i ^{(s) included in} are compared, and a bit error rate E _k is calculated for each k based on the following equation:

Further comprising: selecting E _k for k, and transmitting the selected set of k F to the receiver over the channel;
The method
Using the set F transmitted from the transmitter, set

2. The quantum cryptography communication data processing method according to claim 1, further comprising the step of individually generating a secret key for each k. The transmitter and the receiver are synchronized with a period time T of an operation clock of the transmitter,
Before the step (a), the transmitter transmits a signal light including a random bit value B _i ^(s) encoded within the i-th (i = 1, 2,..., N) period. Further comprising transmitting to the receiver;
The group is generated based on a predetermined signal waveform pattern,
In the step (b), the signal waveform pattern of the decoded bits measured in the step (a) belongs to the kth group (k∈ {1, 2,..., N}) of the groups. Further comprising determining the value of the decoded bit as a bit value B _{i, k} ^(r) ,
In step (d), a set {(B _{i, k} ^(r) , i, k)} _{i, k} including bit values is _converted into elements (B _{i, k} ^(r) , i, k) is decomposed into sets S _k = {(B _{i, k} ^(r) , i, k)} _i
Each S _k element is randomly further broken down into two sets S _k ^(C) and S _k ^(T) ,
Two sets _{^{S (C) = {S k}} (C)} k = 1,2, ... n and _{^{S (T) = {S k}} (T)} k = 1,2, calculate the _{... n,} S ^{( A} subset of ^T)

Transmitting to the transmitter via the channel, and
The step (e) includes the set transmitted from the receiver.

The B _{i, k} ^(r) and B _i ^{(s) included in} are compared, and a bit error rate E _k is calculated for each k based on the following equation:

Further comprising: selecting E _k for k, and transmitting the selected set of k F to the receiver over the channel;
The method
Using the set F transmitted from the transmitter, set

2. The quantum cryptography communication data processing method according to claim 1, further comprising the step of individually generating a secret key for each k. A quantum cryptography communication data processing method between a transmitter and a receiver,
(A) measuring a decoded bit from signal light transmitted from a transmitter;
(B) determining which of the groups generated according to the predetermined parameter the decoded bit belongs to;
(C) obtaining a set including information of decoded bit values belonging to the same group;
(D) dividing the set into two and transmitting information on the position of bit values in one set to the transmitter;
(E) transmitting a bit value set corresponding to the position of the bit value transmitted from the receiver to the receiver;
(F) The bit value set transmitted from the transmitter and the bit value initially received by the receiver are compared to calculate the bit error rate, and the bit value set for performing the key distillation process is selected and the bit value set is selected. A quantum cryptography communication data processing method comprising: transmitting to a transmitter. The transmitter and the receiver are synchronized with a period time T of an operation clock of the transmitter,
Before the step (a), the transmitter transmits a signal light including a random bit value B _i ^(s) encoded within the i-th (i = 1, 2,..., N) period. Further comprising transmitting to the receiver;
The group is generated by dividing the periodic time based on a predetermined time interval;
In the step (b), when the time when the decoded bit is received belongs to the k-th group (kε {1, 2,..., N}) among the groups in the i-th period, Further comprising determining the value of the decoded bit as a bit value B _{i, k} ^(r) ,
In step (d), a set {(B _{i, k} ^(r) , i, k)} _{i, k} including bit values is _converted into elements (B _{i, k} ^(r) , i, k) is decomposed into sets S _k = {(B _{i, k} ^(r) , i, k)} _i
Each S _k element is randomly further broken down into two sets S _k ^(C) and S _k ^(T) ,
Two sets _{^{S (C) = {S k}} (C)} k = 1,2, ... n and _{^{S (T) = {S k}} (T)} k = 1,2, calculate the _{... n,} S ^{( A} subset of ^T)

Transmitting to the transmitter via the channel, and
In step (e), the set transmitted from the transmitter

Bit value information corresponding to

Transmitting to the receiver via the channel, and
The step (f) includes the set transmitted from the transmitter.

The B _i ^(s) and B _{i, k} ^{(r) included} in each are compared, and a bit error rate E _k is calculated for each k based on the following equation:

Further comprising: selecting E _k for k, and transmitting the selected set F of k over the channel to the transmitter;
The method
Using the set F transmitted from the receiver, set

The quantum cryptography communication data processing method according to claim 5, further comprising the step of individually generating a secret key for each k from the list. The transmitter and the receiver are synchronized with a period time T of an operation clock of the transmitter,
Before the step (a), the transmitter transmits a signal light including a random bit value B _i ^(s) encoded within the i-th (i = 1, 2,..., N) period. Further comprising transmitting to the receiver;
The group is generated based on a predetermined signal strength,
In the step (b), when the signal strength of the decoded bit measured in the step (a) belongs to the k-th group (kε {1, 2,..., N}) among the groups, Further comprising determining the value of the decoded bit as a bit value B _{i, k} ^(r) ,
Wherein step (d) sets including the bit values ^{_{{(B i, k (r}} ), i, k)} i, elements with the same value of the k a ^{_{k (B i, k (r}} ), i, k ) Set S _k = {(B _{i, k} ^(r) , i, k)} _i
And each element of S _k is randomly further divided into two sets S _k ^(C) and S _k ^(T) , and two sets S ^(C) = {S _k ^(C) } _{k = 1 , 2, ... n} and S ^(T) = {S _k ^(T) } _{k = 1,2, ... n} , and a subset of S ^(T)

Transmitting to the transmitter via the channel, and
In step (e), the set transmitted from the transmitter

Bit value information corresponding to

Transmitting to the receiver via the channel, and
The step (f) includes the set transmitted from the transmitter.

The B _i ^(s) and B _{i, k} ^{(r) included} in each are compared, and a bit error rate E _k is calculated for each k based on the following equation:

Further comprising: selecting E _k for k, and transmitting the selected set F of k over the channel to the transmitter;
The method
Using the set F transmitted from the receiver, set

The quantum cryptography communication data processing method according to claim 5, further comprising the step of individually generating a secret key for each k from the list. The transmitter and the receiver are synchronized with a period time T of an operation clock of the transmitter,
Before the step (a), the transmitter transmits a signal light including a random bit value B _i ^(s) encoded within the i-th (i = 1, 2,..., N) period. Further comprising transmitting to the receiver;
The group is generated based on a predetermined signal waveform pattern,
In the step (b), the signal waveform pattern of the decoded bits measured in the step (a) belongs to the kth group (k∈ {1, 2,..., N}) of the groups. Further comprising determining the value of the decoded bit as a bit value B _{i, k} ^(r) ,
In step (d), a set {(B _{i, k} ^(r) , i, k)} _{i, k} including bit values is _converted into elements (B _{i, k} ^(r) , i, k) is decomposed into sets S _k = {(B _{i, k} ^(r) , i, k)} _i
Each S _k element is randomly further broken down into two sets S _k ^(C) and S _k ^(T) ,
Two sets _{^{S (C) = {S k}} (C)} k = 1,2, ... n and _{^{S (T) = {S k}} (T)} k = 1,2, calculate the _{... n,} S ^{( A} subset of ^T)

Transmitting to the transmitter via the channel, and
In step (e), the set transmitted from the transmitter

Bit value information corresponding to

Transmitting to the receiver via the channel, and
The step (f) includes the set transmitted from the transmitter.

The B _i ^(s) and B _{i, k} ^{(r) included} in each are compared, and a bit error rate E _k is calculated for each k based on the following equation:

Further comprising: selecting E _k for k, and transmitting the selected set F of k over the channel to the transmitter;
The method
Using the set F transmitted from the receiver, set

The quantum cryptography communication data processing method according to claim 5, further comprising the step of individually generating a secret key for each k from the list. The signal waveform pattern is a function of time A _i (t) (0 ≦ t ≦ T), where 0 is a time when measurement of a decoded bit starts and T is a time when measurement ends.
The closeness of the waveform of the signal waveform pattern a _k (t) corresponding to each of the groups and the A _i (t)

The quantum cryptography communication data processing method according to claim 4 or 8, characterized in that the quantum cryptography communication data processing method is obtained based on: The selection is performed based on whether or not the bit error rate E _k has a length capable of generating a secret key. The quantum cryptography communication data processing method described in 1. A quantum cryptography communication device including a transmitter and a receiver,
(A) means for measuring the decoded bit from the signal light transmitted from the transmitter;
(B) means for determining to which group the decoded bits belong among groups generated according to predetermined parameters;
(C) means for obtaining a set including information of decoded bit values belonging to the same group;
(D) means for dividing the set into two and transmitting a subset including bit values of one set to the transmitter;
(E) A bit error rate is calculated by comparing a subset including a bit value transmitted from a receiver with a bit value initially transmitted by the transmitter, and a bit value set for performing a key distillation process is selected and the bit is selected. Means for transmitting a set of values to a receiver. A quantum cryptography communication device including a transmitter and a receiver,
(A) means for measuring the decoded bit from the signal light transmitted from the transmitter;
(B) means for determining to which group the decoded bits belong among groups generated according to predetermined parameters;
(C) means for obtaining a set including information of decoded bit values belonging to the same group;
(D) means for dividing the set into two and transmitting information on the position of the bit value in one set to the transmitter;
(E) means for transmitting a bit value set corresponding to the position of the bit value transmitted from the receiver to the receiver;
(F) The bit value set transmitted from the transmitter and the bit value initially received by the receiver are compared to calculate the bit error rate, and the bit value set for performing the key distillation process is selected and the bit value set is selected. Means for transmitting to a transmitter.

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