JP2022108576A - Optical secret communication system and optical secret communication device - Google Patents

Abstract

To provide an optical secret communication system and an optical secret communication device that are high in safety and capable of high-speed transmission by randomly spreading a QNSC signal, which is good at high-speed transmission, also on the time axis, and encrypting random number sequence information used to convert data amplitude and phase into multiple values.SOLUTION: An optical secret communication system uses QNSC that masks at least one of a phase or an amplitude level of an optical signal using quantum noise. The optical secret communication system is configured so that a QNSC signal generated by a transmitting unit is randomly spread on a time axis using a common key 1 and is transmitted, and a receiving unit receives the QNSC signal at correct timing using the common key 1 shared in advance with the transmitting unit.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to secure optical communication that transmits information to a receiver without being known by an eavesdropper, and relates to a secure and high-speed secure optical secure communication system and optical secure communication device.

In recent years, businesses using the Internet have developed rapidly, and optical communication networks have come to be used for the transmission of personal information and confidential information. Under such circumstances, it is becoming important to ensure the security of information as the speed and capacity of optical communication networks increase. Stream cryptography using quantum key distribution and optical quantum noise (hereinafter referred to as QNSC: Quantum Noise Stream Cipher) is well known as quantum cryptography used for optical secure communication. The former is said to be able to deliver keys unconditionally safely by transmitting the common key used in stream cipher transmission with single photons or weak coherent light (for example, Non-Patent Document 1 , 2). However, there is a problem that it is necessary to deliver a disposable common key of the same length as the original message to the recipient, and the speed of encrypted communication is limited by the key delivery speed (several 100 kbps).

On the other hand, QNSC is expected to be a common key quantum cryptography that can be put into practical use on the current optical network and can realize high-speed communication of several tens of Gbit/s (for example, Non-Patent Documents 3, 4, 5, 6, see Patent Documents 1, 2, and 3). In QNSC, pseudo-random numbers generated based on a common key are used to multi-level-modulate the phase and/or amplitude of an optical signal, and data is generated in the phase or amplitude fluctuations of the light (this is called quantum noise). The information embedding prevents an eavesdropper from correctly receiving the optical signal. Although perfect secrecy cannot be obtained in this method, the number of modulation levels is increased, and the intervals between changes in the amplitude and/or phase of the modulated optical signal can be controlled by the quanta given at the time of optical detection. By making it sufficiently small compared to noise, the probability that an eavesdropper can correctly determine the signal level can be lowered, and safety can be improved to a level that poses no practical problem.

C. H. Bennett and G. Brassard, “Quantum cryptography: Public key distribution and coin tossing”, Proc. IEEE Int. Conf. Computers, Systems and Signal Processing, 1984, pp.175-179 T. Hirano, H. Yamanaka, M. Ashikaga, T. Konishi, and R. Namiki, “Quantum cryptography using pulsed homodyne detection”, Phys. Rev. A 68, 2003, 042331 G. A. Barbosa, E. Corndorf, P. Kumar, H. P. Yuen, “Secure communication using mesoscopic coherent state”, Phys. Rev. Lett.,2003, vol.90, 227901 O. Hirota, K. Kato, M. Sohma, T. Usuda, K. Harasawa, “Quantum stream cipher based on optical communication”, SPIE Proc. on Quantum Communications and Quantum Imaging, 2004, vol-5551 Osamu Hirota, "Optical Communication Network and Quantum Cryptography", Transactions of the Institute of Electronics, Information and Communication Engineers B, 2004, vol. J87-B, pp.478-486 M. Nakazawa, M. Yoshida, T. Hirooka, and K. Kasai, “QAM quantum stream cipher using digital coherent optical transmission”, Opt. Express, 2014. vol. 22, pp.4098-4107

JP 2006-303927 A JP 2014-93764 A JP 2017-50678 A

Fig. 3 shows how the QNSC signal is generated in the reported QNSC transmission system. Here, the case of using a quadrature amplitude modulation (QAM) system as a modulating signal is taken as an example. In the commonly used optically secure communication method, the original binary data (original data) is mathematically encrypted by the exclusive OR operation using the random number sequence #1 generated with the common key #1, and then encrypted. A signal is mapped to a predetermined format (16 QAM in FIG. 3) and transmitted via an optical fiber. In this case, an eavesdropper applies bending loss to the optical fiber transmission line, detects the 16 QAM signal from the leaked light to the cladding with high sensitivity, and for example searches for information on the random number sequence #1 in a round-robin fashion. , it is possible to decipher the original data.

In order to avoid this risk, in the QNSC system, the 16 QAM signal is further encrypted in the M × M value super multilevel QAM format using the random number sequence #2 generated by the common key #2, and the encrypted signal Information is transmitted in a form in which the level is masked by quantum noise emitted from lasers and optical amplifiers. In other words, it is a two-dimensional physical code in which the amplitude and phase information of an optical signal are simultaneously diffused. For example, by setting M to 1024, the multilevel degree of the encrypted QAM signal becomes M ² ≈10 ⁶ . In this case, an eavesdropper must determine the true value from one million different signal levels, which makes decoding extremely difficult. However, since the QNSC system uses a strong optical signal consisting of about 10 ⁶ to 10 ⁷ photons, it is not possible to obtain a complete masking effect by quantum noise like QKD, which handles weak signals equivalent to single photons. . Therefore, part of the information of the random number sequence #2 contained in the transmitted signal is leaked to the eavesdropper, and although the probability is extremely low, the eavesdropper can decode the random number sequence #2 based on the information obtained from many signals. There was a problem that there was a possibility that it would be done.

The present invention has been made with a focus on such problems. The QNSC signal, which excels in high-speed transmission, is also spread on the time axis, and the information of the random number sequence used for multi-valued data amplitude and phase is also encrypted. It is an object of the present invention to provide an optically secure communication system and an optically secure communication device capable of high-speed transmission with higher security than the conventional QNSC.

In order to achieve such an object, an optical secure communication system according to the present invention is an optical secure communication transmission system using QNSC that masks at least one of the phase or amplitude level of an optical signal using quantum noise. The QNSC signal generated by the unit is randomly spread on the time axis using a common key and then transmitted, and in the receiving unit, using the common key shared in advance with the transmitting unit, correct timing to receive the QNSC signal.

An optically secure communication device according to the present invention is an optically secure communication device using quantum noise stream cryptography (QNSC) that masks at least one of the phase and amplitude level of an optical signal using quantum noise, and generates a The QNSC signal is randomly spread on the time axis using a common key and then transmitted, and in the receiving unit, the QNSC at the correct timing using the common key shared in advance with the transmitting unit It is characterized in that it is arranged to receive a signal.

The optically secure communication system and the optically secure communication device according to the present invention randomly insert the QNSC signal into the time series of dummy signals prepared to make eavesdropping difficult when spreading on the time axis. Alternatively, the order of the QNSC signals may be randomly changed.

The secure optical communication system and secure optical communication device according to the present invention preferably use optical intensity modulation, optical phase modulation, or quadrature amplitude modulation as a modulation method.

Moreover, it is preferable that the optically secure communication system and the optically secure communication device according to the present invention use a secret key that is safely distributed using a quantum key distribution technique as the common key. In this case, safety can be further enhanced.

According to the present invention, by double-encrypting the information of the random number sequence used for encrypting the QNSC signal, which is good at high-speed transmission, it is possible to realize optically confidential communication that combines high security and high speed. , an optically secure communication system and an optically secure communication system can be provided.

(a) A block diagram showing a transmission unit, (b) an explanatory diagram showing the state of spreading of a QNSC signal on the time axis, (c) of the optically secure communication system and the optically secure communication device according to the first embodiment of the present invention. It is a block diagram which shows a receiving part. (a) A block diagram showing a transmission unit, (b) an explanatory diagram showing the state of spreading of a QNSC signal on the time axis, (c) of the optically secure communication system and the optically secure communication device according to the second embodiment of the present invention. It is a block diagram which shows a receiving part. FIG. 4 is an explanatory diagram showing how a QNSC signal is generated using a conventional QAM scheme;

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below based on the drawings.
FIG. 1 shows the transmission section, the state of spreading of the QNSC signal on the time axis, and the reception section of the optically secure communication system and the optically secure communication device according to the first embodiment of the present invention.

The transmission unit of the optically secure communication system illustrated in FIG. A CW light source 3 that emits light used as a carrier wave for optical distribution, an optical modulator 4 that optically modulates the light from the CW light source 3, and a noise source that generates a noise signal to be added to the optically modulated optical signal. 5 and an optical multiplexer 6 for multiplexing the optical signal and the noise signal.

The QNSC transmitter 2 includes a key distribution circuit 7 that distributes the common key 1, random number sequence generation circuits 8-1, 8-2, and 8-3 that generate random number sequences based on the distributed key, and binary data generation. and exclusive logic used when encrypting n-bit binary data output from the data signal generation circuit 9 with the n-bit random number sequence output from the random number sequence generation circuit 8-1. A sum circuit 10, a random mapping circuit 11 that randomly changes the order of the m-bit random number sequence output from the random number sequence generation circuit 8-2, and a random mapping with the n-bit data encrypted by exclusive OR. and an m-bit random number sequence to generate an n + m-bit encrypted signal, and a dummy signal generation circuit 13 that generates dummy binary data used to make eavesdropping difficult. , a selector 14 that selects and outputs a true encrypted signal and a dummy signal based on the l-bit random number sequence output from the random number sequence generation circuit 8-3, and the n+m-bit binary output from the selector 14 It consists of an encoder 15 that converts a signal into a modulated signal of a desired format, and a high-speed D/A converter 16 that converts the digital signal output from the encoder 15 into an analog signal.

For example, when quadrature amplitude modulation (QAM) is used as the modulation format of the encrypted signal, random number sequence generation circuits 8-1 and 8-2, data signal generation circuit 9, exclusive OR circuit 10, random mapping circuit 11 and adder circuit 12 may be provided two each for generating I (in-phase) and Q (quadrature) signals. Also, in accordance with this, two sets of high-speed D/A converters 16 are provided, and a QAM modulator can be used as the optical modulator 4 . On the other hand, when optical phase modulation or optical intensity (amplitude) modulation is used as the modulation format of the encrypted signal, random number sequence generation circuits 8-1 and 8-2, data signal generation circuit 9, exclusive OR circuit 10, random mapping circuit 11, an adder circuit 12 and a high-speed D/A converter 16 may be provided respectively, and an optical phase modulator or an optical intensity modulator may be used as the optical modulator 4 .

As the light emitted from the CW light source 3, for example, a narrow linewidth semiconductor laser or fiber laser can be used. Examples of the noise signal generated by the noise source 5 include spontaneous emission light output from an erbium-doped optical fiber amplifier or a Raman optical amplifier, or an irregular pattern light signal.

FIG. 1(b) shows how the QNSC signal is spread on the time axis in the transmitting section of FIG. 1(a). In the conventional QNSC transmission system, an encrypted signal obtained by converting n-bit I or Q data into a multi-valued m-bit random number sequence is added with quantum noise and then continuously transmitted over time. Here, since the encrypted signal is strong light consisting of approximately 10 ⁶ to 10 ⁷ photons, quantum noise cannot obscure all the information. Therefore, we eliminate the possibility that m-bit random number sequence information is leaked little by little from the eavesdropped signal for each symbol, and the random number sequence pattern is decoded by arranging the information obtained from consecutive multiple symbols. I couldn't cut it. To solve this problem, a dummy symbol containing no data is prepared in each time slot on the time axis, and an encrypted signal (real symbol) is spread in it. At this time, one true symbol is inserted into the dummy signal of N−1 symbols at the timing determined by the information of the l-bit random number sequence (N=2 ^l patterns). This random number sequence is shared in advance between the transmitter and receiver, and the positional information of the true symbol is shared. The larger N is, the lower the detection probability of the true symbol is and the higher the security against eavesdropping can be. On the other hand, since the data speed is in a relationship of decreasing to 1/N, the N value should be set in consideration of both safety and high speed.

The receiving unit of the optically secure communication system illustrated in FIG. 1(c) includes a local light source 17 and a coherent detection circuit 18 for homodyne or heterodyne detection of the received QSNC signal spread on the time axis, and a transmitting unit. A QNSC receiver 19 for decoding data signals using the same common key 1 as a seed key.

The QNSC receiver 19 includes a high-speed A/D converter 20 that converts the analog signal received by the coherent receiving circuit 18 into a digital signal, and a decoder 21 that converts the A/D-converted decimal encrypted digital signal into a binary signal. , a selector 22 for selecting and extracting only the true encrypted signal from the dummy signals, and a decryption circuit for decrypting the encrypted signal based on the common key 1 . The decryption circuit has the same configuration as the encryption circuit in the transmission section except for the subtraction circuit 23 .

For example, when the QSNC signal using QAM as the modulation format of the encrypted signal is homodyne-detected using the local light source 17, the coherent receiving circuit 18 uses a 90-degree hybrid and two balanced PDs. Also, the high-speed A/D converter 20, the subtraction circuit 23, the random number sequence generation circuits 24-1 and 24-2, the exclusive OR circuit 25, and the random mapping circuit 26 are provided for demodulating the I and Q signals, respectively. Two types should be provided. On the other hand, when optical phase modulation or optical amplitude modulation is used as the modulation format of the encrypted signal, a single balanced PD is used for the coherent receiving circuit 18, a high-speed A/D converter 20, a subtraction circuit 23, and a random number sequence. One set each of the generation circuits 24-1 and 24-2, the exclusive OR circuit 25, and the random mapping circuit 26 is sufficient. Furthermore, when optical intensity modulation without code information is used as the modulation format of the encrypted signal, the local light source 17 is unnecessary, and the coherent receiving circuit 18 can use a normal photodiode.

An example of a technique for synchronizing the optical phase of the local light source 17 with the optical phase of the transmitted QSNC signal is a phase control method using an optical phase-locked loop circuit or an optical injection locking circuit. Further, when the QSNC signal is generated in the transmission unit, a tone signal phase-synchronized with the CW light source 3 is generated in a polarized wave orthogonal to the signal, and the reception unit separates the polarization of this tone signal and extracts it. , which is used instead of the local light source 17, a self-delayed homodyne detection system can also be employed.

A wavelength multiplexing circuit and a wavelength demultiplexing circuit are provided in the transmitter and receiver shown in Figs. It is also possible to increase the transmission capacity.

A polarization multiplexing circuit and a polarization separation circuit are provided in the transmission unit and the reception unit shown in FIGS. can also

FIG. 2 shows the transmitting section, the state of spreading of the QNSC signal on the time axis, and the receiving section of the optically secure communication system and the optically secure communication apparatus according to the second embodiment of the present invention.

The transmitter of the optically secure communication system illustrated in FIG. 2(a) differs from that of the first embodiment only in the QNSC transmitter 2'.

The QNSC transmitter 2' includes a key distribution circuit 7 that distributes the common key 1, random number sequence generation circuits 8-1, 8-2, and 8-3 that generate random number sequences based on the distributed key, and binary data. The data signal generation circuit 9 to be generated and the exclusion used when encrypting the n-bit binary data output from the data signal generation circuit 9 with the n-bit random number sequence output from the random number sequence generation circuit 8-1 A logical sum circuit 10, a random mapping circuit 11 that randomly changes the order of the m-bit random number sequence output from the random number sequence generation circuit 8-2, and a random mapping with the n-bit data encrypted by exclusive OR. An addition circuit 12 that generates an encrypted signal of n+m bits by adding the m-bit random number sequence obtained by adding the 1-bit random number sequence output from the random number sequence generation circuit 8-3. A sequence switching circuit 31 for switching the order of signals, an encoder 15 for converting the n+m-bit binary signal output from the sequence switching circuit 31 into a modulated signal of a desired format, and a digital signal output from the encoder 15 as an analog signal. It consists of a high-speed D/A converter 16 that converts to

FIG. 2(b) shows how the QNSC signal is spread on the time axis in the transmitting section of FIG. 2(a). Based on the information of the l-bit random number sequence, the sequence change circuit 31 is used to randomly change the order of the encrypted signals within the block with N′ symbols as one block. Specifically, information for N' symbols is stored in a memory in the order permutation circuit 31, and the order of the stored N' symbols is permuted based on a table that defines the relationship between random number sequence numbers and arrangement order. N' is set in a range that satisfies the relation of factorial of N'< 2 ^l so that all the permutation methods (factorial of N') can be selected with an l-bit random number sequence (up to 2 ^l patterns) do it. Furthermore, in memory, it is possible not only to change the order of information according to random numbers, but also to determine the order according to a certain mathematical rule (software encryption). Unlike the first embodiment, the feature is that the encrypted signal can be spread on the time axis without lowering the data rate.

The receiver of the optically secure communication system illustrated in FIG. 2(c) differs from the first embodiment only in the QNSC receiver 19'.

The QNSC receiver 19' includes a high-speed A/D converter 20 that converts the analog signal received by the coherent receiving circuit 18 into a digital signal, and a decoder that converts the A/D-converted decimal encrypted digital signal into a binary signal. 21, an order restoration circuit 32 for restoring the order-reversed encrypted signals to the normal order, and a decryption circuit for decrypting the encrypted signals based on the common key 1. FIG. The decryption circuit has the same configuration as the encryption circuit in the transmission section except for the subtraction circuit 23 .

In addition, in the first or second embodiment, optical intensity modulation, optical phase modulation, or quadrature amplitude modulation can be used as the modulation method used in the QNSC transmission system.

Further, in the first or second embodiment, security can be further improved by using a secret key distributed using quantum key distribution technology as the common key 1 .

1 common key 2 QNSC transmitter 3 CW light source 4 optical modulator 5 noise source 6 optical multiplexer 7 key distribution circuit 8-1, 8-2, 8-3 random number sequence generation circuit 9 data signal generation circuit 10 exclusive OR circuit 11 Random Mapping Circuit 12 Addition Circuit 13 Dummy Signal Generation Circuit 14 Selector 15 Encoder 16 High Speed D/A Converter

17 local light source 18 coherent receiving circuit 19 QNSC receiver 20 high-speed A/D converter 21 decoder 22 selector 23 subtraction circuit 24-1, 24-2, 24-3 random number sequence generation circuit 25 exclusive OR circuit 26 random mapping circuit

2' QNSC transmitter 31 order permutation circuit 19' QNSC receiver 32 order restoration circuit

Claims (10)

An optical secure communication system using quantum noise stream cryptography (QNSC) that masks at least one of the phase or amplitude level of an optical signal using quantum noise,
The QNSC signal generated by the transmitting unit is randomly spread on the time axis using a common key and then transmitted, and in the receiving unit, using the common key shared in advance with the transmitting unit, the correct An optically secure communication system configured to receive the QNSC signal with timing. 2. The QNSC signal according to claim 1, wherein the QNSC signal is randomly inserted into a time series of dummy signals prepared to make eavesdropping difficult when spreading on the time axis. optical secure communication system. 2. An optically secure communication system according to claim 1, wherein the order of said QNSC signals is randomly changed when spreading them on said time axis. 4. An optically secure communication system according to claim 1, wherein optical intensity modulation, optical phase modulation, or quadrature amplitude modulation is used as a modulation method. 5. The optically secure communication system according to any one of claims 1 to 4, wherein a private key that is securely distributed using quantum key distribution technology is used as the common key. An optical secure communication device using quantum noise stream cryptography (QNSC) that masks at least one of the phase or amplitude level of an optical signal using quantum noise,
The QNSC signal generated by the transmitting unit is randomly spread on the time axis using a common key and then transmitted, and in the receiving unit, using the common key shared in advance with the transmitting unit, the correct An optically secure communication device configured to receive the QNSC signal with timing. 7. The QNSC signal according to claim 6, wherein the QNSC signal is randomly inserted into a time series of dummy signals prepared to make eavesdropping difficult when spreading on the time axis. Optical secret communication device. 7. The optically secure communication device according to claim 6, wherein the order of the QNSC signals is randomly changed when the QNSC signals are spread on the time axis. 9. An optical secure communication device according to claim 6, wherein optical intensity modulation, optical phase modulation, or quadrature amplitude modulation is used as a modulation method. 10. An optically secure communication device according to any one of claims 6 to 9, wherein a private key that is securely distributed using quantum key distribution technology is used as the common key.

Images