JP2008005046A - Encryption communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an encryption communication system capable of reducing transmission line costs while performing quantum communication to key information for generating a decoding key and performing normal communication of other pieces of information. <P>SOLUTION: In the encryption communication system; a transmitter transfers time information related to quantum information, error correction information for correcting the inconsistency between an encryption key generated at a transmission side and a decoding key generated at a reception side, and a cryptogram to a receiver by normal communication, in addition to the quantum information (key information for generating a decoding key). In the transmitter, at least two kinds of time information, error correction information, and a cryptogram are multiplexed, and a frame is formed which has a period of the multiple of the bit rate of the quantum information to be transmitted, or that of 1/multiple. The frame is transmitted in synchronization with the transmission of the quantum information. In the receiver, a clock signal is extracted from a reception frame, and the reception frame is multiplexed and separated. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an encryption communication system, and can be applied to, for example, encryption communication using quantum optical communication (appropriately called quantum communication) technology.

  Recently, quantum cryptography communication techniques such as those disclosed in Patent Document 1 and Non-Patent Document 1 have attracted attention. Prior to the description of the quantum cryptography communication system described in Non-Patent Document 1, the background leading to this will be described.

  FIG. 6 shows the configuration of a basic quantum cryptography communication system. In this communication system, plaintext is encrypted by the optical quantum transmitter 1 and output to the transmission line, received by the optical quantum receiver 2, decrypted into plaintext, and output. What is characteristic about this encryption communication system is that different information is loaded on each photon.

  Therefore, when the eavesdropper sniffs a part of the signal, the arrival quantum decreases, so that eavesdropping can be detected. That is, in the case of eavesdropping, the communication safety can be ensured by immediately stopping the transfer of information. Even if an eavesdropper steals a part of the signal, obtains the information, and then tries to hide the fact of eavesdropping by putting light quantum again, the quantum state becomes It cannot be restored. As described above, since the sender / receiver can detect the fact of the wiretapping, it is said to be safe.

  However, the realization of the quantum cryptography communication system shown in FIG. 6 is extremely difficult at the present time.

  This is because information is lost on the transmission path, the photon detection rate of the receiver is less than 100%, or the error rate is large. As countermeasures, it is conceivable to perform error correction or add a redundant signal to the signal, but such a technique is vulnerable to an attack by an eavesdropper.

  As a quantum cryptography communication system improved in the above points, there is a quantum cryptography communication system described in Non-Patent Document 1, and its conceptual configuration is shown in FIG.

  In FIG. 7, the transmission side device 10 includes an optical quantum transmitter 11, a time information transmitter / receiver 12, an error correction information transmitter / receiver 13, a ciphertext transmitter 14, and a control device 15, while the reception side device 20 Machine 21, time information transmitter / receiver 22, error correction information transmitter / receiver 23, ciphertext receiver 24, and control device 25. An encryption key (or information of that kind) is exchanged between the photon transmitter 11 and the photon receiver 21, time information is exchanged between the time information transmitter / receiver 12 and the time information transmitter / receiver 22, and an error correction information transmitter / receiver 13 and Error correction information is exchanged between the error correction information transmitter / receiver 23, ciphertext is exchanged between the ciphertext transmitter 14 and the ciphertext receiver 24, and control devices 15 and 25 control transmission / reception of these information.

  The system shown in FIG. 6 described above attempts to send “encrypted plaintext = (ciphertext)” in the optical quantum transmitter, whereas in the system of FIG. 7, the optical quantum transmitter 11 uses the encryption key. Only the information is sent, and the ciphertext is sent by the ciphertext transmitter 14 through another transmission line that does not use the quantum cipher.

  In the cryptographic communication system of FIG. 7 as well, the case where a part of the cryptographic key transmitted by the quantum communication is lost on the transmission path or cannot be received by the receiver is the same as in the case of FIG.

  Therefore, a random number is sent from the transmission side to the reception side as encryption key creation information, and the reception side creates a decryption key (in this specification, the decryption key is also appropriately expressed as an encryption key) using only the received information. Then, only the received time information is sent from the reception side to the transmission side, and the transmission side forms a key from the transmission time information.

  The plaintext is encrypted using this key, and the created ciphertext is sent to the receiving side. Since the information sent from the receiving side to the transmitting side is only time information, there is no problem in safety even if it is wiretapped. The transmission / reception time information of the encryption key is transmitted / received using the time information transmitters / receivers 12 and 22.

  Further, when the encryption key is transmitted / received, there is a possibility that “1” and “0” are erroneously received by the receiving side device 20, but this is solved by performing error correction. In this error correction stage, part of the key information may be leaked due to eavesdropping. In order to avoid this, after error correction, a privacy amplification operation for discarding a part of the key information is performed to recover security in terms of information theory. The error correction information is exchanged between the error correction information transceivers 13 and 23.

  The ciphertext transmitter 14 encrypts the plaintext and transmits it to the ciphertext receiver 24, and the ciphertext receiver 24 returns the ciphertext to plaintext.

  As described above, the quantum communication method is applied only to the transmission / reception of the encryption key, and the classical communication method is used for other transmission / reception.

Since ciphertext is not quantum cryptography, there seems to be a question about its security, but if an encryption key with a length equal to the length of plaintext is used, it cannot be broken by information theory. Yes. This is impossible even with a computer having infinite computing power.
JP 2005-012631 A www.rcast.u-tokyo.ac.jp/en/research/meeting/2005/0413/pdf/01.pdf

  However, the cryptographic communication system using the quantum communication technique shown in FIG. 7 has the following two problems.

  The first problem is that the transmission / reception of the encryption key and the transmission / reception of other information are performed using different transmission paths, and other information such as synchronization time information, reception time information, error correction information, and ciphertext are , Could not be sent simultaneously on a common transmission line.

  Therefore, until now, the synchronization time information and the ciphertext could only be transmitted / received at different times or using different transceivers. However, this has been a factor that impairs the convenience of the apparatus and increases the cost.

  The second problem is that there is a possibility that “1” and “0” may be received in error when receiving the information of the encryption key. It was necessary to make corrections. Due to this complicated operation, there is a problem that it takes time to start transmission and reception of information after the apparatus is activated.

  Therefore, an encryption communication system and method using quantum optical communication technology that can reduce transmission line cost is desired, and encryption communication using quantum optical communication technology that can shorten the time until ciphertext transmission is started. Systems and methods are desired.

  The first aspect of the present invention transfers the decryption key generation key information used for generating the decryption key from the encryption transmission apparatus to the encryption reception apparatus as quantum information by quantum communication, and relates to the decryption key generation key information. Time correction information, error correction information for correcting a mismatch between the encryption key generated by the encryption transmitter and the decryption key generated by the encryption receiver based on the decryption key generation key information, and the encryption key In the cryptographic communication system that transfers the ciphertext obtained by encrypting the plaintext using the normal communication that is not quantum communication, (1) the cipher transmitting device includes (1-1) the time information, the error correction information, and the above Multiplexing / framing means for multiplexing at least two types of ciphertexts to form a frame having a period that is a multiple or a fraction of the bit rate of the quantum information to be transmitted, (1- A frame normal transmission means for transmitting the frame in synchronism with the transmission of the quantum information, and (2) the cipher receiver (2-1) a clock signal for extracting a clock signal from the received frame. And (2-2) frame synchronization / information extraction means for demultiplexing received frames.

  The second aspect of the present invention transfers the decryption key generation key information used for generating the decryption key from the encryption transmission apparatus to the encryption reception apparatus as quantum information by quantum communication, and relates to the decryption key generation key information. A cipher communication system that transfers time information and ciphertext obtained by encrypting plaintext using the cipher key by normal communication that is not quantum communication, and (1) the cipher transmitter uses the cipher key Provided with a code adding means for adding at least an error correction code to the plaintext, and (2) the cipher receiving apparatus encrypts the plaintext using the decryption key. Provided after the decoding means for decoding the text, and provided with plaintext error processing means for performing error correction on the decoded plaintext based on the added error correction code, and (3) decoding in the system key Characterized by not comprising an error correction function for the body.

  According to the first aspect of the present invention, it is possible to provide an encryption communication system using quantum optical communication technology that can reduce transmission line costs. In addition, according to the second aspect of the present invention, it is possible to provide an encryption communication system using a quantum optical communication technique that can shorten the time required to start transmission of ciphertext.

(A) First Embodiment Hereinafter, a first embodiment of a cryptographic communication system according to the present invention will be described in detail with reference to the drawings.

(A-1) Configuration of the First Embodiment FIG. 1 is a block diagram showing the configuration of the cryptographic communication system of the first embodiment.

  In FIG. 1, the cryptographic communication system 50 according to the first embodiment is configured by connecting a cryptographic transmission device 100 and a cryptographic reception device 200 via three transmission paths.

  The cryptographic transmission apparatus 100 includes a random number generation unit 101, a quantum transmission unit 102, a clock signal generation unit 103, a normal transmission unit 104, a time information generation unit 105, an encryption key creation information storage unit 106, an encryption key generation unit 107, an encryption Means 108, multiplexing / framing means 109 and normal receiving means 110, and encryption key generating means 107 has error correcting means 111 and privacy amplifying means 112.

  On the other hand, the cryptographic receiving apparatus 200 includes a quantum receiving unit 201, an encryption key creation information storage unit 202, a normal receiving unit 203, a clock signal extraction unit 204, a frame synchronization / information extraction unit 205, an encryption key generation unit 206, and a decryption unit. 207 and normal transmission means 208, and the encryption key generation means 206 has error correction means 209 and privacy amplification means 210.

  The functions of the units 101 to 112 of the encryption transmitting apparatus 100 and the units 201 to 210 of the encryption receiving apparatus 200 will be clarified in the description of the operation.

(A-2) Operation of the First Embodiment Next, the operation of the cryptographic communication system 50 of the first embodiment will be described.

  In the cryptographic transmitting apparatus 100, the random number generating means 101 generates a random number that becomes a seed of the cryptographic key. The quantum transmission unit 102 transmits the random number to the reception device 200 side in synchronization with the clock generated by the clock signal generation unit 103. The quantum transmission unit 102 performs quantum transmission, for example, according to a differential phase shift method. That is, the random numbers “0” and “1” are transmitted in association with the phases “0” and “π” of the optical signal by the built-in phase modulator, respectively.

  The time information generation unit 105 generates information on the time when the random number is transmitted based on the clock generated by the clock signal generation unit 103. The transmitted random number (encryption key seed information) is stored as generated time information in the encryption key generation information storage unit 106 as information for generating an encryption key.

  The time information generated by the time information generation means 105 is also given to the multiplexing / framing means 109, and is framed by the multiplexing / framing means 109 together with error correction information and ciphertext described later. The generated frame is transmitted to the receiving apparatus 200 side by the normal transmission unit 104 in synchronization with the clock generated by the clock signal generation unit 103.

  The multiplexing / framing means 109, for example, time-division multiplexes time information, error correction information, and ciphertext. Also, the multiplexing / framing means 109 framing according to, for example, an SDH (Synchronous Digital Hierarchy) system. At the time of framing, a mark is added to the time information, error correction information, and ciphertext delimiter so that the cipher receiving apparatus 200 can recognize where the demultiplexed information is delimited. The frame period is a multiple (or a multiple of a multiple) of the bit rate of quantum transmission synchronized with the same clock, and frame transmission and quantum transmission are synchronized. The normal transmission unit 104 transmits the frame according to any existing communication method (for example, an existing optical communication method) other than the quantum communication method.

  Here, time information, error correction information, and ciphertext need not be inserted in one frame, and some information may be blank (all 1 or all 0). For example, the error correction information and ciphertext fields of the frame in which the time information is inserted may be blank, and for example, the time information and ciphertext fields of the frame in which the error correction information is inserted are blank. For example, the time information and error correction information fields of the frame in which the ciphertext is inserted may be blank.

  Further, when the random number is regenerated at a predetermined cycle, the time information, error correction information, and / or ciphertext inserted in one frame may be related to different random number generation cycles.

  The encryption key generation unit 107 generates an encryption key based on a random number stored in the encryption key creation information storage unit 106 and gives it to the encryption unit 108. As will be described later, the error correction unit 111 built in the encryption key generation unit 107 may generate error correction information, and this error correction information is given to the multiplexing / frame forming unit 109.

  The encryption means 108 encrypts the plaintext to be transmitted using the encryption key given from the encryption key generation means 107, and the obtained ciphertext is given to the multiplexing / framing means 109.

  In the cipher receiving apparatus 200, the normal receiving means 203 receives the above-described frame (multiplex information). The clock signal extraction unit 204 extracts a clock signal based on the received frame, and provides the frame signal to the frame synchronization / information extraction unit 205, the quantum reception unit 201, and the encryption key creation information storage unit 202.

  The frame synchronization / information extraction unit 205 separates the time information, error correction information, and ciphertext multiplexed in the frame, gives the time information to the encryption key generation information storage unit, and supplies the error correction information to the encryption key generation unit 206. And the ciphertext is given to the decryption means 207.

  The quantum receiving unit 201 receives the quantum information transmitted by the quantum transmitting unit 102 of the encryption transmitting apparatus 100 (the above-described random number if received correctly) based on the clock signal extracted by the clock signal extracting unit 204. is there. The quantum reception unit 201 detects, for example, that the phase of the time slot differs by π from the detector that detects that the phase of the time slot (1 bit period of random number) of the received optical signal is in phase with each other. The quantum information is regenerated based on the outputs of both detectors. Therefore, the reproduced quantum signal may be a random number that the cryptographic transmission device 100 is attempting to transmit, or may be a series (inverted random number) obtained by inverting each bit value of the random number.

  In any case, the quantum information received by the quantum reception unit 201 is stored in the encryption key creation information storage unit 202 together with the received time information. That is, the stored time information is transmitted by the normal transmission unit 104 of the cryptographic transmission device 100.

  The encryption key generation unit 206 generates an encryption key based on the quantum information of the encryption key generation information storage unit 202 and gives it to the decryption unit 207.

  However, since there is a possibility that the quantum information received by the cipher receiving apparatus 200 has an error, the cipher transmitting apparatus 100 and the cipher receiving apparatus 200 may receive error correction information between the error correcting units 111 and 209 provided respectively. And time information, etc., and error correction of the received quantum information. Both error correction means 111 and 209 are the random numbers and transmission time information stored in the encryption key creation information storage means 106 on the transmission side and the received quantum stored in the encryption key creation information storage means 202 on the reception side. Information and reception time information are indirectly collated, and if there is an error, communication for error correction is performed.

  The error correction information is transferred from the cipher transmitting apparatus 100 to the cipher receiving apparatus 200 by the frame as described above. The normal transmission means 208 of the encryption receiver 200 is given error correction information from the encryption key generation means 206, and appropriately receives the reception time information stored from the encryption key generation information storage means 202 to correct the error. The information and / or the reception time information are transmitted to the normal reception device 110 on the encryption transmission device 100 side according to any existing communication method (for example, an existing optical communication method). The normal receiving apparatus 110 gives the received error correction information and / or reception time information to the error correction means 111.

  In the communication process for error correction as described above, information leakage may occur and safety may be impaired. Therefore, the encryption key generating means 107 and 206 of the encryption transmitting apparatus 100 and the encryption receiving apparatus 200 are respectively generated from the encryption keys generated by the built-in privacy amplifying means 112 and 210 based on the random numbers and the received quantum information after error correction processing. , A part thereof is discarded and given to the corresponding encryption means 108 and decryption means 207 as the final encryption key. Thereby, the safety from the leakage of information during communication for error correction is recovered. For example, both privacy amplifying means 112 and 210 have the same partial discard rule.

  The decryption means 207 decrypts the ciphertext given from the frame synchronization / information extraction means 205 using the encryption key given from the encryption key generation means 206, and outputs the obtained plaintext.

  The characteristic feature of the first embodiment is that the conventional system shown in FIG. 7 requires a transmission path for acquiring time information separately from the transmission path for ciphertext. By using and transmitting, time information can be transmitted and received together with other information such as ciphertext.

  The ideas here are: (a) multiplexing is performed by framing, (a) the clock synchronization function in the frame is used for the clock signal of quantum communication, (c) the period of the frame is the bit of the quantum transmission By making it a multiple of the rate (or a fraction of a multiple), slipping between the transmission time information and the bit position is prevented. Here, if there is a difference in the transmission time between the quantum information and the frame due to the difference in the transmission path length and the wavelength used, a delay line that performs delay equalization on at least one transmission path so as to absorb this difference. Should be provided.

(A-3) Effects of First Embodiment According to the first embodiment, in addition to quantum information that is information on the type of encryption key, time information that needs to be transmitted from the transmitter to the receiver, Error correction information and ciphertext can be transmitted in parallel on a single transmission path. In addition, a clock synchronization function and an anti-slip function for associating time information with quantum information can be easily realized.

(B) Second Embodiment Next, a second embodiment of the cryptographic communication system according to the present invention will be described with reference to the drawings. Below, it demonstrates centering around difference with 1st Embodiment.

  FIG. 2 is a block diagram showing the configuration of the cryptographic communication system according to the second embodiment. The same and corresponding parts as those in FIG. 1 according to the first embodiment are indicated by the same and corresponding reference numerals. Yes.

  In the cryptographic communication system 50A of the second embodiment, the cryptographic transmission device 100A includes the wavelength multiplexing unit 113 in addition to the same constituent elements 100 to 112 as those of the first embodiment, and the opposing cryptographic reception device 200A is In addition to the same constituent elements 200 to 210 as in the first embodiment, wavelength demultiplexing means 211 is provided.

  The wavelength multiplexing means 113 is supplied with a transmission signal of quantum information output from the quantum transmission means 102 and a transmission signal of frames output from the multiplexing / framing means 109. In the case of the second embodiment, the carrier wavelength (λ1) in the transmission signal from the quantum transmission means 102 and the carrier wavelength (λ2) in the transmission signal from the multiplexing / framing means 109 are different from each other. The means 113 combines both transmission signals and sends them to a common transmission line.

  The wavelength demultiplexing unit 211 demultiplexes the optical signal that has arrived from such a common transmission path into a wavelength component (λ1) related to the transmission signal of quantum information and a wavelength component (λ2) related to the transmission signal of the frame. Then, the quantum information transmission signal obtained by the demultiplexing is given to the quantum receiving means 201, and the frame transmission signal obtained by the demultiplexing is given to the normal receiving means 203.

  Except for the quantum information and the wavelength division multiplexing transmission of frames as described above, the configuration and function of each unit are the same as those in the first embodiment.

  According to the second embodiment, the same effect as that of the first embodiment can be obtained. Furthermore, according to the second embodiment, there is an effect that a single transmission optical fiber can be used, and the utilization efficiency of the transmission path to be used can be increased.

(C) Third Embodiment Next, a third embodiment of the cryptographic communication system according to the present invention will be described with reference to the drawings. Below, it demonstrates centering around difference with 2nd Embodiment.

  FIG. 3 is a block diagram showing the configuration of the cryptographic communication system according to the third embodiment. The same corresponding parts as those in FIG. 1 according to the first embodiment are indicated by the same reference numerals. .

In the second embodiment described above, quantum information and a frame are to be wavelength-multiplexed. In the third embodiment, quantum information and a frame are to be time-division multiplexed. Therefore, in the cryptographic communication system 50B according to the third embodiment, the cryptographic transmission device 100B includes a two-input one-output optical switch (SW) 114 instead of the wavelength multiplexing unit 113 according to the second embodiment, The receiving device 200B includes a 1-input 2-output optical switch (SW) 212 instead of the wavelength demultiplexing unit 211 of the second embodiment. The optical switch 114 receives the control signal from the multiplexing / framing unit 109. Accordingly, the quantum information output from the quantum transmission means 102 and the frame output from the multiplexing / framing means 109 are alternatively selected and transmitted to a common transmission line. In response to the control signal from the frame synchronization / information extraction unit 205, the optical switch 212 sends the received signal of the quantum information period in the signal arriving from the common transmission path to the quantum reception unit 201 and arrives from the common transmission path. The received signal of the frame period in the received signal is sent to the normal receiving means 203.

  4A1 and 4A2 are explanatory diagrams of control signals output from the multiplexing / framing means 109. FIG. The quantum transmission means 102 periodically outputs quantum information as shown in FIG. 4 (A1). On the other hand, as shown in FIG. 4 (A2), the multiplexing / framing means 109 sets the period during which quantum information is output as a null area (null period), and includes frame overhead and time between adjacent null areas. A frame including information, error correction information and ciphertext is transmitted. Further, the multiplexing / framing unit 109 selects a control signal for selecting the output signal from the quantum transmission unit 102 in the null region and selecting the output signal from the multiplexing / framing unit 109 in a region other than the null region. To the optical switch 114.

  Since the control of the optical switch (SW) 212 of the encryption receiver 200B is symmetrical to the above, the description thereof is omitted.

  FIGS. 4B1 and 4B2 are explanatory diagrams of other examples of control signals output from the multiplexing / framing means 109. FIG. In this example, frames are transmitted in every other period among periods between successive quantum information.

  According to the third embodiment, the same effects as those of the first and second embodiments can be obtained. Furthermore, according to the third embodiment, optical signals having the same wavelength can be used for communication of quantum information and frames, and there is an effect that interference between the two is reduced.

(D) Fourth Embodiment Next, a fourth embodiment of the cryptographic communication system according to the present invention will be described with reference to the drawings. Note that, unlike the first to third embodiments, the fourth embodiment does not perform error correction of the encryption key.

  FIG. 5 is a block diagram showing the configuration of the cryptographic communication system according to the fourth embodiment. The same and corresponding parts as those in FIG. 1 according to the first embodiment are assigned the same and corresponding reference numerals. Show.

  The cryptographic communication system 50C of the fourth embodiment also includes a cryptographic transmission device 100C and a cryptographic reception device 200C.

  The cryptographic transmission apparatus 100C according to the fourth embodiment includes a random number generation unit 101, a quantum transmission unit 102, a clock signal generation unit 103, a normal transmission unit 104, a time information generation unit 105, an encryption key creation information storage unit 106, and an encryption key. A generation unit 107C, an encryption unit 108, a normal reception unit 110, an error correction / detection code addition unit 115, and a normal transmission unit 116 are included.

  On the other hand, the cryptographic receiving device 200C includes a quantum receiving unit 201, an encryption key creation information storage unit 202, a normal receiving unit 203, a clock signal extraction unit 204, a time information extraction unit 205C, an encryption key generation unit 206C, a decryption unit 207, A normal transmission unit 208, a normal reception unit 213, and an error correction / detection unit 214 are included.

  As described above, in the case of the fourth embodiment, the error correction of the encryption key is not performed. Therefore, the error correction units 111 and 209 and the privacy amplification unit 112 are included in the encryption key generation units 107C and 206C. 210 are not provided.

  Hereinafter, the operation of the cryptographic communication system 50C according to the fourth embodiment will be described focusing on differences from the first to third embodiments described above.

  In the case of the fourth embodiment, quantum information (random number), time information, and ciphertext are transmitted from the cipher transmitting apparatus 100C to the cipher receiving apparatus 200C through separate transmission paths. Therefore, the cryptographic transmission apparatus 100C according to the fourth embodiment does not include the multiplexing / framing unit 109, and the normal transmission unit 104 uses the time information generated by the time information generation unit 105 as the quantum information from the quantum transmission unit 102. Synchronize with the transmission of information and send it to the transmission line.

  On the other hand, the cryptographic receiving apparatus 200C of the fourth embodiment includes a time information extracting unit 205C that extracts only time information instead of the frame synchronization / information extracting unit 205, and the time information extracting unit 205C extracts (receives) the time information. The time information is given to the encryption key creation information storage unit 202, and the encryption key creation information storage unit 202 stores the quantum information given from the quantum reception unit 201 in association with the time information from the time information extraction unit 205C. To do. After storing, the encryption key creation information storage unit 202 gives the received time information to the normal transmission unit 208 for transmission.

  In the cryptographic transmission apparatus 100C of the fourth embodiment, the cryptographic key generation unit 107A confirms that the time information has arrived at the normal reception unit 110 (in other words, that the random number has been reached at the receiving side). ), A random number corresponding to the time information is taken out from the encryption key creation information storage means 105 to generate an encryption key and give it to the encryption means 108.

  In the fourth embodiment, the error correction / detection code adding unit 115 and the error correction / addition unit 115 are configured so that highly accurate communication can be performed without performing error correction of the encryption key generated in the encryption receiving device 200C. Detection means 214 is provided. The normal transmission unit 208 and the normal reception unit 110 of the fourth embodiment are for performing communication for reflecting on the transmission side the results of error correction and error detection for the ciphertext on the reception side.

  The error correction / detection code adding means 115 adds an error correction code and / or an error detection code to the plaintext (plaintext data) to be transmitted, and gives it to the encryption means 108. The encryption means 108 The plaintext with the correction code and / or error detection code added is converted into a ciphertext using the encryption key given from the encryption key generation means 107A, and this ciphertext is sent to the ciphertext transmission path by the normal transmission means 116. To do.

  The normal reception unit 213 gives the received ciphertext to the decryption unit 207, and the decryption unit 207 converts the ciphertext into plaintext using the encryption key given from the encryption key generation unit 206A. The plaintext obtained by the decoding means 207 is added with an error correction code and / or an error detection code. The error correction / detection means 214 determines whether an error has occurred in the plaintext body output from the decryption means 207 or whether the error can be corrected if an error has occurred, and the plaintext in which no error was detected (error correction) A plaintext body from which codes and error detection codes are excluded) and plaintext with corrected errors are output.

  The error correction / detection unit 214 gives error information (for example, error rate information, a retransmission request, etc.) for reflecting the error correction and error detection results on the transmission side to the normal transmission unit 208. The error correction / detection unit 214 obtains statistical information such as an error rate as appropriate.

  The normal transmission unit 208 of the fourth embodiment transmits the error information given from the error correction / detection unit 214. For example, when the error rate is higher than a predetermined threshold, the normal transmission unit 208 may capture the reception time information and transmit it together with the error rate so that it can be used for error analysis on the transmission side. .

  The normal receiving unit 110 provides the received information or information obtained by processing the received information to the error correction / detection code adding unit 115 and / or the encryption key generating unit 107C.

  For example, the error correction / detection code adding unit 115 changes the strength of the error correction code in accordance with the error rate. In order to recover a sentence with a high error rate, encoding with high redundancy must be performed rather than applying to a sentence with a low error rate, so that the actual transmission rate is lowered. Therefore, the strength of the error correction code is dynamically changed according to the error rate, and the relationship between the error rate and the redundancy in the error correction coding is optimized.

  Regarding the error that cannot be recovered, as described above, the cryptographic receiving apparatus 200C can also issue a retransmission request. Here, the retransmission may be a retransmission using only the ciphertext, or a retransmission of quantum information (random number) and ciphertext. In the former case, the error correction / detection code adding means 115 may increase the strength of the error correction code from the previous time. Also, reception time information is used as time information related to retransmission. In the case of retransmitting the quantum information, in FIG. 5, the image is sent from the normal receiving means 110 to the encryption key generating means 107C, and the encryption key generating means 107C instructs the quantum transmitting means 102 to retransmit. However, a control unit (for example, see FIG. 7) that controls each unit of the cryptographic transmission device 100C may control the retransmission of the quantum information. The same applies to retransmission of ciphertext. In the above description, the reception side performs retransmission determination. However, the transmission side may perform retransmission determination according to the arrival error rate or the like.

  In the first to third embodiments described above, the error of the reception key information in the quantum communication means is dealt with by error correction for the reception key information, and the information leaks out in the communication for error correction. It was compensated by the privacy amplification function.

  On the other hand, in the fourth embodiment, errors in quantum information (random numbers) or encryption keys are not corrected, and encryption and decryption are performed using non-corresponding encryption keys on the transmission side and the reception side. Allow the state to do. Since the decryption is performed using the incorrect encryption key, the received information (plain text) naturally includes an error. However, before encryption, redundant information is added by error correction coding (or error correction, detection coding), and the information error due to the encryption key error is recovered. Even if the encryption key is transmitted correctly, there may be an error in the decrypted plaintext due to noise mixed in the transmission path of the ciphertext. This error can also be corrected by the error correction code correction function. it can. In addition, errors that cannot be corrected for plain text are dealt with by retransmission.

  According to the fourth embodiment, the transmission side can perform encryption and transmission immediately after obtaining the reception time information of the random number, and the time until transmission can be made shorter than the prior art shown in FIG. it can. Further, in the prior art shown in FIG. 7, it is necessary to perform communication for error correction of random numbers (or encryption keys) and an operation for improving privacy. In the fourth embodiment, such processing is performed. It becomes unnecessary.

(E) Other Embodiments Although various modified embodiments have been mentioned in the description of each of the above embodiments, further modified embodiments as exemplified below can be given.

  In the description of each of the above embodiments, the encryption key generated on the transmission side and the encryption key (decryption key) generated on the reception side have been described with the same image. However, if the public key cryptosystem is adopted, The encryption key generated on the transmission side and the encryption key (decryption key) generated on the reception side may be different. Further, if a public key cryptosystem is adopted, what is transmitted as quantum information may be an encryption key generated on the transmission side instead of a random number.

  In the first to third embodiments, the three types of information other than the quantum information are all inserted into the frame. However, only two of the three types are multiplexed into the frame, One type of information may be handled separately. Also in this case, wavelength multiplexing using three wavelengths may be performed, or time division multiplexing by switching with a frame as one element may be performed.

  In the fourth embodiment, the random number and the time information are transmitted in parallel. However, they may be transmitted by wavelength multiplexing or may be transmitted by time division multiplexing by switching. A ciphertext obtained by encrypting plaintext to which an error correction / detection code is added may be included as an element of wavelength multiplexing or time division multiplexing.

  In the fourth embodiment, the time information and the ciphertext are transmitted in parallel. However, the time information and the ciphertext may be transmitted in a frame.

It is a block diagram which shows the structure of the encryption communication system of 1st Embodiment. It is a block diagram which shows the structure of the encryption communication system of 2nd Embodiment. It is a block diagram which shows the structure of the encryption communication system of 3rd Embodiment. It is explanatory drawing of the time division multiplexing of the quantum information and frame of 3rd Embodiment. It is a block diagram which shows the structure of the encryption communication system of 4th Embodiment. It is a block diagram which shows the structure of the basic conventional encryption communication system using a quantum communication technique. It is a block diagram which shows the structure of the conventional encryption communication system which carries out the quantum communication of only the information for a generation of a decoding key.

Explanation of symbols

50, 50A ... cryptographic communication system,
DESCRIPTION OF SYMBOLS 100, 100A, 100B, 100C ... Encryption transmission device, 101 ... Random number generation means, 102 ... Quantum transmission means, 103 ... Clock signal generation means, 104 ... Normal transmission means, 105 ... Time information generation means, 106 ... For encryption key creation Information storage means 107, 107C ... encryption key generation means 108 ... encryption means 109 ... multiplexing / framing means 110 ... normal reception means 111 ... error correction means 112 ... privacy amplification means 113 ... wavelength combination Wave means 114 ... Optical switch 115 ... Error correction / detection code addition means 116 ... Normal transmission means
200, 200A, 200B, 200C ... encryption receiving apparatus, 201 ... quantum receiving means, 202 ... encryption key creation information storage means, 203 ... normal reception means, 204 ... clock signal extraction means, 205 ... frame synchronization / information extraction means, 205C ... Time information extraction means, 206, 206C ... Encryption key generation means, 207 ... Decryption means, 208 ... Normal transmission means, 209 ... Error correction means, 210 ... Privacy amplification means, 211 ... Wavelength demultiplexing means, 212 ... Light Switch, 213... Normal reception means, 214... Error correction / detection means.

Claims (10)

The key information for generating the decryption key used for generating the decryption key is transferred as quantum information from the cipher transmitting apparatus to the cipher receiving apparatus by quantum communication, and the time information related to the key information for generating the decryption key, The plaintext is encrypted using the error correction information for correcting the mismatch between the encryption key generated in step 1 and the decryption key generated based on the decryption key generation key information in the encryption receiver, and the encryption key. In the cipher communication system that transfers the ciphertext that has been transferred by normal communication that is not quantum communication,
The cipher transmitter is
Multiplexing that multiplexes at least two of the time information, the error correction information, and the ciphertext to form a frame having a cycle that is a multiple or a fraction of the bit rate of the transmitted quantum information・ Framed means;
Frame normal transmission means for transmitting the frame in synchronization with the transmission of the quantum information,
The above encryption receiver is
Clock signal extracting means for extracting a clock signal from the received frame;
An encryption communication system comprising: frame synchronization / information extraction means for demultiplexing received frames. In the cipher transmitting apparatus, the encryption key generating means for generating the encryption key includes a privacy amplifying means for generating a final encryption key used for creating the cipher text by excluding a part of the generated encryption key,
In the above encryption receiver, the decryption key generating means for generating the decryption key includes a privacy amplifying means for generating a final decryption key used for decrypting the ciphertext by excluding a part of the generated decryption key. The cryptographic communication system according to claim 1, wherein: The cryptographic transmission device includes wavelength multiplexing means for wavelength-multiplexing the quantum information and the frame and transmitting them to a wavelength multiplexing transmission line,
The cryptographic communication system according to claim 1 or 2, wherein the cryptographic receiving device includes wavelength demultiplexing means for demultiplexing the wavelength multiplexed signal from the wavelength multiplexing transmission line. The cryptographic transmission device includes a transmission-side optical switch that time-division-multiplexes the quantum information and the frame by switching and sends them to a time-division multiplexing transmission line,
The cryptographic communication system according to claim 1 or 2, wherein the cryptographic reception device includes a reception-side optical switch that demultiplexes the time division multiplexed signal from the time division multiplexing transmission line by switching. The decryption key generation key information used for generating the decryption key is transferred as quantum information by quantum communication from the encryption transmission apparatus to the encryption reception apparatus, and the time information related to the decryption key generation key information and the encryption An encryption communication system for transferring a ciphertext obtained by encrypting a plaintext using a key by a normal communication that is not quantum communication,
The cipher transmitter is
Provided before the encryption means for encrypting the plaintext by using the encryption key, comprising code addition means for adding at least an error correction code to the plaintext,
The above encryption receiver is
Provided after decryption means for decrypting the ciphertext using the decryption key, comprising plaintext error processing means for performing error correction based on the error correction code added to the decrypted plaintext,
An encryption communication system characterized in that the system does not have an error correction function for the decryption key itself. The code adding means of the cipher transmitting apparatus also has a function of adding an error detecting code, and the plaintext error processing means of the cipher receiving apparatus is based on an error detecting function based on the error detecting code and a detected error. Has a function to obtain statistical information related to errors
6. The cryptographic receiving apparatus includes error statistical information transmitting means for transmitting error statistical information, and the cryptographic transmitting apparatus includes error statistical information receiving means for receiving error statistical information. Cryptographic communication system.   The code addition means of the encryption transmitting apparatus dynamically changes the strength of the error correction code based on the received error statistical information.   8. The cryptographic communication system according to claim 5, wherein the time information and the ciphertext are framed and transferred from the cipher transmitting apparatus to the cipher receiving apparatus.   9. The cryptographic communication system according to claim 5, wherein the quantum information and the frame are wavelength-multiplexed and transferred from the cryptographic transmission device to the cryptographic reception device. 9. The cryptographic communication system according to claim 5, wherein the quantum information and the frame are time-division multiplexed by switching and transferred from the cryptographic transmission device to the cryptographic reception device.

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