CN215990829U - Quantum key distribution equipment capable of defending Trojan light attack - Google Patents
Quantum key distribution equipment capable of defending Trojan light attack Download PDFInfo
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- CN215990829U CN215990829U CN202121587571.1U CN202121587571U CN215990829U CN 215990829 U CN215990829 U CN 215990829U CN 202121587571 U CN202121587571 U CN 202121587571U CN 215990829 U CN215990829 U CN 215990829U
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Abstract
The utility model discloses quantum key distribution equipment capable of defending Trojan light attack. Wherein the low damage threshold optical device comprises a fused optical fiber. The optical transmission element is arranged between the attenuation unit and the low-damage threshold optical device, and is provided with a first port, a second port and a third port, and the first port, the second port and the third port are respectively connected with the attenuation unit, the low-damage threshold optical device and the first optical detection element. Therefore, the defense for various Trojan light attacks can be realized only based on the conventional optical device without a high-power optical device.
Description
Technical Field
The utility model relates to the field of quantum secret communication, in particular to quantum key distribution equipment which is realized based on a conventional optical device and can defend Trojan light attack.
Background
Quantum Key Distribution (QKD) is based on the quantum mechanics principle, and is a key distribution system that can be theoretically proven unconditionally safe due to the quantum unclonable and inaccurate measurement principle. In an actual quantum key distribution device, due to the imperfect characteristics of devices, corresponding protection measures are required to prevent information leakage.
For example, at present, a modulator is generally required to be used at a transmitting end of quantum key distribution equipment, and reflection is inevitable in an optical path, so that if an eavesdropper inputs trojan light from the outside, the trojan light is modulated as same as output light of the quantum key distribution equipment when reaching the modulator, carries modulation information, is detected by the eavesdropper after being reflected and then output, and information leakage is caused. The Trojan light is generated by an eavesdropper, and theoretically, the eavesdropper can control the intensity of the Trojan light input into the quantum key distribution equipment, namely the Trojan light can be strong all the time to reach the degree of damaging devices; the Trojan light can be very weak, and can be detected only after being reflected and output; the horse light may also be strong to damage the device before being adjusted to a lower light intensity level.
In order to defend attack light injected from the outside, two basic defense ideas of a passive defense type and an active defense type are provided in the prior art.
In passive defense, the optical isolator is often introduced to reduce the intensity of external input light entering the internal optical path. Because the optical isolator generally has a narrow bandwidth of only tens of nanometers, an optical filter is usually used in cooperation with the optical isolator to achieve a wide-spectrum optical isolation effect. Meanwhile, the optical isolator and the optical filter used are generally required to have higher power so as to prevent the device from being damaged by strong light and then losing the defense effect even if the defense effect is reduced.
In active monitoring defense, an optical circulator is often designed at an outlet of quantum key distribution equipment, wherein a first port of the optical circulator is connected with a light path of the quantum key distribution equipment, a second port of the optical circulator is connected with an external optical fiber link, and a third port of the optical circulator is connected with a single-photon detector or a photodiode to implement attack light monitoring. For example, fig. 1 illustrates an active defense scheme for defending against a strong light attack. As shown in fig. 1, a first port of the optical circulator 38 is connected to the single photon detector 37, a second port 39 and a third port 40 are respectively connected to the internal encoding optical path and the external optical fiber link, and an optical band-pass filter 41 is disposed on a connection optical path between the optical circulator and the internal encoding optical path. The coded signal light output by the internal coded optical path can be output to an external optical fiber link through ports 39 and 40 of the optical circulator 38, and the attack light input to the quantum key distribution equipment through the external optical fiber link enters the single photon detector 37 through the third port 40 and the first port of the optical circulator to obtain monitoring.
The inventors have discovered, by studying the above prior defense schemes, that the prior passive defense schemes require the use of high power devices to ensure that the devices do not fail under high light, and that such optical devices are generally composed of multiple components, and that if one of the components is damaged under high light, it is possible to cause failure of the entire device. At present, the damage threshold of common optical filters and optical isolators is not high, special customization is needed, and the problems of high technical difficulty and high cost are faced.
The existing active defense scheme needs to monitor externally input light through a single-photon detector or a photodiode. In fact, when external strong light is very strong, the single-photon detector is damaged by the strong light, and the condition that normal alarm cannot be given is caused. Even if the single-photon detector uses a conventional photodiode, the situation that the normal alarm cannot be given after the single-photon detector is damaged by strong light exists, and particularly the attack mode of strong light and weak light is difficult to deal with. This would make the system at great risk, causing the key information to be revealed. In addition, the single photon detectors used in the prior art are high in cost. Even if a conventional photodiode is used, the situation that the alarm cannot be normally given after being attacked by strong light exists, so that the system has great risk and information leakage is caused.
Moreover, none of these defense schemes fully satisfies the defense requirements of complex trojan light attacks.
SUMMERY OF THE UTILITY MODEL
Aiming at the problems in the prior art, the utility model discloses quantum key distribution equipment which can realize the defense against various Trojan light attacks without a high-power optical device and only based on a conventional optical device, thereby providing safety guarantee for the quantum key distribution process in an economic, stable and reliable manner.
Specifically, the quantum key distribution device capable of defending Trojan light attack may include a sending end and a receiving end;
the transmitting end comprises a light source, a coding unit and an attenuation unit;
the receiving end comprises a decoding unit;
the optical transmission device is characterized in that the transmitting end further comprises an optical transmission element, a low-damage threshold optical device and a first optical detection element;
the low damage threshold optical device comprises a fused optical fiber; and the number of the first and second electrodes,
the optical transmission element is arranged between the attenuation unit and the low-damage threshold optical device and is provided with a first port, a second port and a third port;
the optical transmission element is further configured to: the optical signal input through the first port is at least partially output by the second port, and the optical signal input by the second port is at least partially output by the third port; and the first port, the second port and the third port are respectively connected with the attenuation unit, the low damage threshold optical device and the first optical detection element.
Further, the optical transmission element is a circulator.
Further, the optical transmission element is an optical beam splitter, which also has a fourth port; wherein, the optical signal input through the first port is respectively output from the second port and the fourth port according to a certain proportion, and the optical signal input through the second port is respectively output from the first port and the third port according to a certain proportion.
Preferably, the optical splitter is a 50:50 optical splitter.
Preferably, a second optical detection element is connected to the fourth port.
Further, the optical detection element is a photodiode.
Further, the damage threshold of the fused optical fiber is 400-600 mW. Preferably, the damage threshold of the fused optical fiber is 500 mW.
Further the optical transmission element is a 50:50 optical beam splitter and the first optical detection element is a photodiode having a sensitivity of-60 dBm.
Still further, the internal impairments of the quantum key distribution device are such that the trojan light experiences an attenuation of at least 80dB from entering the quantum key distribution device to the reflected output.
Drawings
The following describes embodiments of the present invention in further detail with reference to the accompanying drawings.
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 shows a schematic diagram of a prior art active defense glare attack scenario;
fig. 2 shows an exemplary embodiment of a quantum key distribution device that can protect against trojan light attacks implemented based on conventional optical devices according to the present invention.
Detailed Description
Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following examples are provided by way of illustration in order to fully convey the spirit of the utility model to those skilled in the art to which the utility model pertains. Accordingly, the present invention is not limited to the embodiments disclosed herein.
Fig. 2 shows an exemplary embodiment of a quantum key distribution device that can protect against trojan light attacks implemented based on conventional optical devices according to the present invention.
As shown in fig. 2, the quantum key distribution device includes a transmitting end and a receiving end.
The transmitting end may include a light source, an encoding unit, an attenuation unit, a low damage threshold light device, an optical transmission element, and a first optical detection element.
The receiving end may include a decoding unit.
In the transmitting end, a light source is used to provide an optical signal, which may be, for example, a continuous optical signal or a pulsed optical signal. As an example, the light source may be in the form of a laser, such as a semiconductor laser, as shown in fig. 2.
The encoding unit is used for encoding the optical signal according to a quantum coding protocol to obtain signal light carrying encoded information. For example, quantum encoding protocols may include, but are not limited to, polarization encoding, phase encoding, time phase encoding, MDI encoding, and the like.
The attenuation unit is used for carrying out intensity attenuation on the signal light. As an example, the attenuation unit may comprise a variable optical attenuator.
The optical transmission element is arranged between the attenuation unit and the low-damage threshold optical device and is provided with a first port, a second port and a third port, wherein the first port is connected with the output end of the attenuation unit, the second port is connected with the input end of the low-damage threshold optical device, and the third port is connected with the first optical detection element.
In the present invention, the optical transmission element may be configured to: the optical signal input through the first port is at least partially output from the second port, and the optical signal input through the second port is at least partially output from the third port.
As an example, as shown in fig. 2, the optical transmission element may include an optical beam splitter, which also has a fourth port. The optical signal input through the first port is output from the second port and the fourth port according to a certain proportion, and the optical signal input through the second port is output from the first port and the third port according to a certain proportion.
For example, the beam splitter may employ a conventional 50:50 beam splitter. Therefore, after the optical signal is input into the optical beam splitter through the first port, the optical signal is divided into two equal parts and is output through the second port and the fourth port respectively; similarly, after the external trojan light is input into the optical beam splitter through the second port, the external trojan light is divided into two equal parts and is output through the first port and the third port respectively.
As another example, the optical transmission element may include a circulator. Wherein, the optical signal is output through the second port after being input through the first port; similarly, external trojan light may be input through the second port and output through the third port.
In the present invention, a low damage threshold optical device may be implemented by means of fused optical fibers. Since a smaller light guiding area and thus a higher power density can be achieved on the fused fiber than on a conventional fiber by fusion-drawing the fiber, a lower damage threshold can be achieved than on a conventional fiber.
Therefore, in the quantum key distribution device, the fused optical fiber with the appropriate damage threshold can be simply selected, so that the light path is allowed to be cut off when the light intensity of the externally input Trojan light exceeds the damage threshold, the Trojan light is prevented from further entering the interior of the sending end and forming strong light attack on other optical devices, and the key safety is ensured. Therefore, the light intensity of the Trojan light input into the quantum key distribution equipment can be ensured to be lower than the determined threshold value by virtue of the low-damage threshold value optical device, the optical devices in the quantum key distribution equipment do not need to select special devices with high damage threshold values, and the optical devices can be realized by adopting conventional optical devices, so that the cost of the quantum key distribution equipment is reduced, and the stability of the quantum key distribution equipment is improved.
In the quantum key distribution device of the present invention, the damage threshold of the low damage threshold optical device may be designed to be 400-600mW, preferably 500 mW. Therefore, if the light intensity of the trojan light exceeds 500mW, the low-damage threshold optical device will be damaged, thereby disconnecting the optical path from the output port of the quantum key distribution equipment to further enter the quantum key distribution equipment, and protecting the internal devices of the quantum key distribution equipment; meanwhile, the quantum key distribution process is interrupted, and the security of the key is ensured. The quantum key distribution device can be realized by using conventional optical devices without special high-power optical devices because the optical power entering the quantum key distribution device can be ensured not to be stronger than 500 mW.
According to the utility model, the optical transmission element is arranged to organically combine the low-damage threshold optical device with the first optical detection element, so that the weak Trojan horse light attack behavior can be detected by means of the first optical detection element while the strong Trojan horse light attack can be resisted, and an alarm can be provided when the weak Trojan horse light attack behavior is resisted. Thereby, the quantum key distribution equipment is allowed to have the capability of resisting various Trojan light attacks.
As mentioned before, due to the arrangement of the low damage threshold optics, the maximum value of the light intensity of the trojan light entering the quantum key distribution device is limited, thus allowing the first optical detection element to be implemented with conventional optics.
As an example, the first optical detection element may be realized by means of a conventional photodiode, which is sufficient to meet the requirements for protection against weak trojan light attacks.
For better understanding of the present invention, the operation of the quantum key distribution device will be described below by taking the specific embodiment shown in fig. 2 as an example, wherein the optical splitter is a 50:50 splitter.
Conventional photodiodes may have a sensitivity of-60 dBm, and therefore, when they detect a trojan with an optical power higher than-60 dBm, they will generate an alarm to interrupt the quantum key distribution process, ensuring key security.
At present, the repetition frequency of the quantum key distribution equipment is higher by about 1GHz, and the average photon number per pulse is required to be less than 1 photon, so that the output optical power of the quantum key distribution equipment is generally lower than-70 dBm.
Most quantum key distribution devices employ semiconductors for communicationThe laser is used as a light source and typically has a power of about +10dBm at continuous light output. Therefore, in pulse modulation, even though the very conservative estimation of the monopulse temporal width is 10ps, the optical power is larger than-10 dBm at a repetition frequency of 1GHz, whose equivalent duty cycle is estimated to be 1/100. Generally speaking, Trojan horse light experiences an attenuation of at least 80dB from entering the quantum key distribution device to the reflected output without the use of an optical isolator. Therefore, when the Trojan light entering the quantum key distribution equipment is weaker than-60 dBm, the reflected light which can be obtained by an attacker is at least 70dB weaker than the signal light carrying information of the quantum key distribution equipment, namely 1/10 of original information of the information obtained by the Trojan light by the attacker7Hereinafter, it has been almost impossible to obtain effective information. Therefore, in the quantum key distribution equipment, the conventional photodiode is adopted to detect and early warn Trojan light, and Trojan light attack can be effectively prevented under the condition of not using an isolator and a filter.
In summary, in the utility model, the traditional active or passive defense idea which needs to be realized by means of a high-power device is abandoned, a Trojan horse light defense scheme which is realized by means of organic combination of a light transmission element, an optical detection element and a low-damage threshold light device is originally provided, various Trojan horse light attack modes (such as strong light, weak light or strong-first weak attack and weak-second attack) can be resisted without any high-power device and only by means of a conventional light device, the safety of the light device in the quantum key distribution equipment is ensured in a simple, stable and effective mode, and finally the safety of the quantum key is ensured. In addition, the utility model further provides a method for realizing the low-damage threshold optical device by melting the optical fiber, thereby providing a simple and accurate implementation scheme of the low-damage threshold optical device.
Compared with the prior scheme using a high-power device, the utility model does not need to use a high-damage threshold device; compared with the existing scheme of monitoring externally input light by using a single-photon detector or a photodiode, the quantum key distribution device has no risk of abnormal alarm, so that more economic, stable and safe defense can be realized, quantum key distribution equipment is protected, and the key safety is ensured.
Further, as shown in fig. 2, when the optical transmission element is implemented by using the optical splitter, a second optical detection element (e.g., a second conventional photodiode) may be connected to the fourth port of the optical splitter for monitoring the light intensity of the device or calibrating other parameters.
Although the present invention has been described in connection with the embodiments illustrated in the accompanying drawings, it will be understood by those skilled in the art that the embodiments described above are merely exemplary for illustrating the principles of the present invention and are not intended to limit the scope of the present invention, and that various combinations, modifications and equivalents of the above-described embodiments may be made by those skilled in the art without departing from the spirit and scope of the present invention.
Claims (10)
1. A quantum key distribution device capable of defending Trojan light attack comprises a sending end and a receiving end;
the transmitting end comprises a light source, a coding unit and an attenuation unit;
the receiving end comprises a decoding unit;
the optical transmission device is characterized in that the transmitting end further comprises an optical transmission element, a low-damage threshold optical device and a first optical detection element;
the low damage threshold optical device comprises a fused optical fiber; and the number of the first and second electrodes,
the optical transmission element is arranged between the attenuation unit and the low-damage threshold optical device and is provided with a first port, a second port and a third port;
the optical transmission element is further configured to: the optical signal input through the first port is at least partially output by the second port, and the optical signal input by the second port is at least partially output by the third port; and the first port, the second port and the third port are respectively connected with the attenuation unit, the low damage threshold optical device and the first optical detection element.
2. A quantum key distribution device as claimed in claim 1 wherein the optical transmission element is a circulator.
3. A quantum key distribution device as claimed in claim 1 wherein the optical transmission element is an optical beam splitter further having a fourth port;
wherein, the optical signal input through the first port is respectively output from the second port and the fourth port according to a certain proportion, and the optical signal input through the second port is respectively output from the first port and the third port according to a certain proportion.
4. A quantum key distribution device as claimed in claim 3 wherein the optical splitter is a 50:50 optical splitter.
5. A quantum key distribution device according to claim 3, wherein a second optical detection element is connected to the fourth port.
6. The quantum key distribution device of any of claims 1-5, wherein the optical detection element is a photodiode.
7. The quantum key distribution device of claim 1, wherein the fused optical fiber has a damage threshold of 400-600 mW.
8. A quantum key distribution device as claimed in claim 7 wherein the damage threshold of the fused optical fibre is 500 mW.
9. A quantum key distribution device according to claim 1, wherein the optical transmission element is a 50:50 optical beam splitter and the first optical detection element is a photodiode having a sensitivity of-60 dBm.
10. A quantum key distribution device as claimed in claim 9 wherein the internal insertion loss is such that the trojan light experiences an attenuation of at least 80dB from entering the quantum key distribution device to the reflected output.
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