Impersonation detection system

Abstract

To provide an impersonation detection system capable of reducing possibility of disrupting aviation control to improve aviation safety, using an ADS-B signal used in a secondary radar for aviation control.SOLUTION: An impersonation detection system causes: receiving devices 1, 2 to regularly receive responses to questions to a transponder mounted on an aircraft as ADS-B signals; a processing device 4 to obtain the difference between a prediction value obtained from the regularly received ADS-B signals and an actually measured value corresponding to the prediction value; and when the difference exceeds a certain threshold, determines the aircraft that sent the ADS-B signals to be an impostor.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a spoofing detection system using an ADS-B (Automatic Dependent Surveillance-Broadcast) signal used in secondary radar for air traffic control, and more particularly to a spoofing detection system that reduces the possibility of interfering with air traffic control and improves air safety.

Background Art

[0002] [Prior Art] In conventional air traffic control radio systems, it is important to accurately grasp the position of an aircraft. So far, the position of an aircraft has been grasped by irradiating a high-power signal with a primary radar and receiving the reflected wave.

[0003] However, with a primary radar, it is impossible to identify which aircraft the signal is from, and it is also impossible to obtain information about the aircraft such as altitude. Therefore, in recent years, it has been considered to obtain aircraft information by interrogating a transponder mounted on an aircraft with a secondary radar and receiving a response from the aircraft.

[0004] The mechanism for this signal exchange is ADS-B (Automatic Dependent Surveillance-Broadcast). ADS-B is a system in which an on-board device mounted on an aircraft broadcasts aircraft information including the position based on the positioning result obtained by the aircraft's navigation device.

[0005] Although there are many advantages to air traffic control using ADS-B, as a disadvantage, it is not encrypted and can be viewed by anyone. Therefore, there is a possibility that a malicious third party may spoof an aircraft and respond to a signal from ground equipment, causing interference with air traffic control. Hereinafter, the signal transmitted from an aircraft using the mechanism of ADS-B will be referred to as an "ADS-B signal".

[0006] [Related technologies] Furthermore, a related prior art is Japanese Patent Publication No. 2017-225107, "System and Method for Protecting the Privacy of ADS-B Messages" (Patent Document 1). Patent Document 1 describes a system that protects the privacy of broadcast automated dependent surveillance (ADS-B) messages transmitted by an aircraft by including a generator that determines whether the aircraft's position is genuine and generates a false aircraft position to calculate the position of a false aircraft. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2017-225107 [Overview of the project] [Problems that the invention aims to solve]

[0008] As explained in the section on conventional air traffic control, the use of ADS-B for aircraft positioning had a problem: malicious third parties could potentially disrupt air traffic control by impersonating aircraft using drones or other means.

[0009] The current ADS-B system lacks a mechanism to prevent spoofing, and since it's not practical to equip all aircraft transponders with encryption devices, it also has the problem of delaying the transition to air traffic control using secondary radar.

[0010] Furthermore, Patent Document 1 does not describe a configuration for ensuring the safety of air traffic control by detecting cases where a malicious third party, for example, uses a drone to impersonate an aircraft.

[0011] This invention has been made in view of the above circumstances, and aims to provide a spoofing detection system that can reduce the possibility of disrupting air traffic control and improve aviation safety by utilizing ADS-B signals used in secondary radar for air traffic control. [Means for solving the problem]

[0012] To solve the problems of the above-mentioned conventional example, the present invention provides a constant ADS-B signal for the response to a question sent to a transponder mounted on an aircraft. With the first receiving device and the second receiving device A spoofing detection system that receives and detects aircraft impersonation, and on a regular basis In the first receiving device Received ADS-B signal The data includes the aircraft's position, speed, and direction of travel. Obtained from The first Doppler shift amount Predicted values ​​and, First Corresponds to predicted values The first Doppler shift amount is calculated from the frequency of the ADS-B signal and the transmission frequency of the transponder. Compared to the measured value First Get the difference, The second difference is obtained between a second predicted value of the Doppler shift amount obtained from the aircraft's position, speed, and direction of travel contained in the ADS-B signal data received on a regular basis by the second receiving device, and a second measured value of the Doppler shift amount calculated from the frequency of the ADS-B signal and the transmission frequency of the transponder, corresponding to the second predicted value, and the second difference is obtained by subtracting the second difference from the first difference. The system is characterized by having a processing unit that determines that an aircraft that transmitted an ADS-B signal is a spoof if it exceeds a certain threshold.

[0015] This invention provides a constant ADS-B signal for the response to a question sent to a transponder mounted on an aircraft. With the first receiving device and the second receiving device A spoofing detection system that receives and detects aircraft impersonation, wherein the processing unit is In the first receiving device Received ADS-B signal The reception time of the radio waves and the aircraft's position information contained in the ADS-B signal data are obtained, and the reception time of the ADS-B signal radio waves received by the second receiving device and the aircraft's position information contained in the ADS-B signal data are obtained, and the reception time From the time difference Based on the aircraft's position information acquired by the first and second receivers The aircraft's hyperbola is calculated to obtain a predicted position, and the predicted position on the hyperbola is compared with the aircraft's position included in the ADS-B signal. information When the actual value is used as the measured value, the difference between the predicted value and the actual value. However, if a certain threshold is exceeded, the aircraft that transmitted the ADS-B signal is considered to be impersonating another aircraft. It is characterized by making a determination.

[0016] This invention provides a constant ADS-B signal for the response to a question sent to a transponder mounted on an aircraft. With the first receiving device and the second receiving device A spoofing detection system that receives and detects aircraft impersonation, wherein the processing unit is In the first receiving device Received ADS-B signal data The location of the aircraft included information and speed and direction of travel Information predict a specific position in the direction of travel and calculate a predicted value, and at the specific position aircraft receive an ADS-B signal from an aircraft at the time when it is predicted to have reached, and for the signal In a second receiving device near a specific location obtain the position of the aircraft included in data as the measured value, and determine the difference information between the predicted value and the measured value However, if a certain threshold is exceeded, the aircraft that transmitted the ADS-B signal is considered to be impersonating another aircraft. It is characterized by doing so.

[0017] The present invention is characterized in that in the forgery detection system, a plurality of the above forgery detection systems are combined.

Advantages of the Invention

[0018] According to the present invention, a processing device constantly receives a response to a query to a transponder mounted on an aircraft as an ADS-B signal, and in the processing device, constantly With the first receiving device and the second receiving device received ADS-B signal In the first receiving device obtains a predicted value obtained from The data includes the aircraft's position, speed, and direction of travel. and, The first Doppler shift amount a difference between the predicted value and First a measured value corresponding to the predicted value The first Doppler shift amount is calculated from the frequency of the ADS-B signal and the transmission frequency of the transponder. is obtained, and First if it exceeds a specific threshold value, it is determined that the aircraft that transmitted the ADS-B signal is a forgery. As a forgery detection system, there is an effect that it is possible to reduce the possibility of causing an obstacle to air traffic control and improve air safety. The second difference is obtained between a second predicted value of the Doppler shift amount obtained from the aircraft's position, speed, and direction of travel contained in the ADS-B signal data received on a regular basis by the second receiving device, and a second measured value of the Doppler shift amount calculated from the frequency of the ADS-B signal and the transmission frequency of the transponder, corresponding to the second predicted value, and the second difference is obtained by subtracting the second difference from the first difference.

Brief Description of the Drawings

[0019] [Figure 1] It is a schematic configuration diagram of this system. [Figure 2] It is a schematic configuration diagram of the first system. s [Figure 3] [[ID=,54]]It is a schematic explanatory diagram of the second system. [Figure 4] It is a schematic explanatory diagram of the third system. [[ID=,60]]

Modes for Carrying Out the Invention

[0020] Embodiments of the present invention will be described with reference to the drawings. [Summary of the Embodiment] The impersonation detection system according to an embodiment of the present invention (this system) includes a receiving device that continuously receives responses to questions sent to a transponder mounted on an aircraft as ADS-B signals, and a processing device that obtains the difference between a predicted value obtained from the continuously received ADS-B signals and the measured value corresponding to the predicted value. If the difference exceeds a certain threshold, it is determined that the aircraft that transmitted the ADS-B signal is an impersonator. This reduces the possibility of disrupting air traffic control and improves aviation safety. Furthermore, the following three systems are specific embodiments of this system.

[0021] [This system: Figure 1] The configuration of this system will be explained with reference to Figure 1. Figure 1 is a schematic diagram of the system's configuration. As shown in Figure 1, this system basically consists of receiving devices 1 and 2, a transmitting device 3, a processing device 4, and a display device 5.

[0022] [Overview of each device in this wireless system] In this wireless system, receiving devices 1 and 2 receive ADS-B signals from the aircraft and transmit them to the processing device 4, which is a higher-level device, along with information about the reception time assigned by an internal high-precision time server. Furthermore, receiving devices 1 and 2 receive response signals to the interrogation signals transmitted from transmitting device 3 to the aircraft, and transmit the response signals to processing device 4, which then detects the impersonation.

[0023] Furthermore, if the processing unit 4 determines that an aircraft is impersonating another aircraft, it can change the aircraft icon displayed on the map on the display device 5 for the aircraft identified as impersonating another aircraft. It can also remove the aircraft icon altogether.

[0024] Transmitter 3 transmits an interrogation signal to the aircraft using an ADS-B signal. Furthermore, the transmitter 3 controls the output beam of the interrogation signal, and by adjusting the beam direction and beam output strength, the beam range is made variable. Specifically, as will be described later, the system detects spoofing by adjusting the direction and size of the main lobe of the transmitted beam, as well as the size of the side lobes.

[0025] The processing unit 4 receives ADS-B signals from the receiving devices 1 and 2, obtains the difference between the predicted value obtained from the ADS-B signal and the measured value corresponding to that predicted value, and if the difference exceeds a certain threshold, it determines that the aircraft that transmitted the ADS-B signal is a spoof and detects the spoofing. Furthermore, the processing unit 4 stores the ADS-B signals and information related to impersonation received from the receiving devices 1 and 2 in the external storage device 42. Furthermore, the processing unit 4 outputs aircraft information and impersonation information to the display device 5.

[0026] The display device 5 displays aircraft information and impersonation information, as well as instructs the control of the transmission beam in the transmission device 3 and displays information related to said control.

[0027] [Details of each part of this wireless system] This section will provide a detailed explanation of each component of this wireless system. [Receiving devices 1, 2] Receivers 1 and 2 have the same configuration but are installed in different locations. To measure the aircraft's position, it is desirable for the two receivers 1 and 2 to be far apart, ideally several kilometers to 100 kilometers apart. Since receivers 1 and 2 have the same configuration, the following description will focus on receiver 1, and the description of receiver 2 will be omitted.

[0028] The receiving device 1 comprises an omnidirectional antenna 11, a high-frequency unit 12, a signal processing unit 13, a high-precision time server 14, and a network device 15. The omnidirectional antenna 11 receives the ADS-B signal, the high-frequency section 12 removes unwanted signals using a filter and amplifies the received signal, and the signal processing section 13 demodulates the mode S signal of the ADS-B signal.

[0029] The signal processing unit 13 detects information about the aircraft's position, speed, and direction of travel from the response signal. The high-precision time server 14 distributes time information, enabling the signal processing unit 13 to synchronize time with high precision. The network device 15 transmits the demodulated result from the signal processing unit 13 to the higher-level processing unit 4. In receiver 1, an omnidirectional antenna 11 was used, but as shown in receiver 2, a directional antenna 21 may be used instead. Alternatively, receiver 2 may also use an omnidirectional antenna.

[0030] [Transmitter 3] The transmitting device 3 comprises a directional antenna 31, a high-frequency unit 32, a signal processing unit 33, and a network device 35. The network device 35 receives the interrogation signal from the processing unit 4 and modulates it in the signal processing unit 33. The high-frequency unit 32 controls the beam formation according to the direction and size (strength) of the transmission beam that transmits the ADS-B signal specified by the display device 5, and transmits the ADS-B signal including the interrogation signal towards the aircraft using the formed transmission beam from the directional antenna 31.

[0031] [Processing device 4] The processing unit 4 comprises a central processing unit 41, an external storage device 42, and a network device 43. The central processing unit 41 processes the aircraft information received from the receiving devices 1 and 2, and also performs detection of aircraft impersonation. Specifically, if the difference between the estimated position and the measured position is appropriate, it is determined that it is not an impersonation; if it is inappropriate, it is determined that it is an impersonation. Furthermore, the central processing unit 41 generates parameters for transmission beamforming in the transmitting device 3 based on settings from the display device 5 and transmits them to the transmitting device 3.

[0032] The external memory device 42 stores aircraft information, including information about impersonation, which is then used for analysis and other purposes. Network device 43 connects to network devices 15 and 25 of receiving devices 1 and 2, and further connects to network device 35 of transmitting device 3 to send and receive data.

[0033] Next, I will explain the first to third systems in detail. [System 1: Figure 2] The first system involves receiving devices 1 and 2 calculating a predicted value of the Doppler shift amount from the aircraft's position, speed, and direction of travel included in the received ADS-B signal, and calculating a measured value of the Doppler shift amount from the frequency of the received ADS-B signal. The processing device 4 then obtains the predicted and measured values ​​from the receiving devices 1 and 2, and if the difference between the predicted and measured values ​​exceeds a certain threshold, it determines that the aircraft that transmitted the ADS-B signal is a spoof. This reduces the possibility of disrupting air traffic control and improves aviation safety.

[0034] The first system will be explained with reference to Figure 2. Figure 2 is a schematic diagram of the first system. The first system, as shown in Figure 2, uses two receiving devices 1 and 2 to obtain the aircraft's position, speed, and direction of travel from the received ADS-B signal.

[0035] Receiving devices 1 and 2 calculate the estimated Doppler shift amount from the acquired aircraft's position, speed, and direction of travel, and use this as a predicted value. Next, they calculate the Doppler shift amount from the ADS-B signal itself that was actually received, and use this as a measured value.

[0036] The processing unit 4 corrects for the frequency shift of the aircraft's transponder based on the difference in Doppler shift amounts calculated by two or more receiving devices 1,2, and compares this to a specific threshold to determine whether or not it is a spoof. At this time, it is assumed that the frequency accuracy of each receiving device is sufficiently high relative to the aircraft's transponder.

[0037] This section provides a detailed explanation of impersonation detection using Doppler shift. The receiving device 1 calculates and estimates the Doppler shift amount ΔFa from the aircraft's position, speed, and direction of travel information contained in the received ADS-B signal, and obtains a predicted value (ΔFa). Similarly, the receiving device 2 calculates and estimates the Doppler shift amount ΔFb from the aircraft's position, speed, and direction of travel information contained in the received ADS-B signal, and obtains a predicted value (ΔFb).

[0038] Furthermore, since each transponder installed on an aircraft has a frequency difference (α), the measured Doppler shift amount calculated from the ADS-B signal itself by receiving devices 1 and 2 is calculated from the frequency of the ADS-B signal and the transponder transmission frequency, and therefore the measured Doppler shift amount will include the frequency difference (α). In other words, the Doppler shift of the measured value at receiver 1 is "ΔFa'+α", and the Doppler shift of the measured value at receiver 2 is "ΔFb'+α". Here, ΔFa' and ΔFb' are measured Doppler shift amounts that do not include the frequency shift (α).

[0039] Next, the processing unit 4 performs the following calculations based on the predicted values ​​and measured values. (ΔFa-(ΔFa'+α))-(ΔFb-(ΔFb'+α))=γ Here, γ is the difference; if γ > a specific threshold, there is a possibility of impersonation, and if γ ≤ a specific threshold, it is determined to be normal. The specific threshold is determined through simulation. In the above formula, the frequency shift (α) cancels out, so the frequency shift is corrected.

[0040] The processing unit 4 groups the Doppler shift amount information transmitted from each receiving device by the same time and target. Aircraft are assigned identification numbers, so they can be grouped together according to these numbers.

[0041] [Second system: Figure 3] The second system involves a processing unit 4 that calculates an aircraft hyperbola from the time differences of ADS-B signals received at multiple locations to obtain a predicted value for the aircraft's position. If the difference between the predicted value on the hyperbola and the measured value of the aircraft's position included in the ADS-B signal exceeds a certain threshold, the system determines that the aircraft that transmitted the ADS-B signal is a spoof. This reduces the possibility of disrupting air traffic control and improves aviation safety.

[0042] The second system will be explained with reference to Figure 3. Figure 3 is a schematic diagram of the second system. The second system, specifically as shown in Figure 3, is a spoofing detection mechanism using the TDOA (Time Difference Of Arrival) method. For the ADS-B signal received by receiving station a (receiving device 1), the time of reception and the location information of the transmitting station (aircraft) are transmitted to the processing device 4. For the ADS-B signal received by receiving station b (receiving device 2), the time of reception and the location information of the transmitting station (aircraft) are also transmitted to the processing device 4. Here, we assume that receiving station a and receiving station b are synchronized with sufficient precision.

[0043] The processing unit 4 then calculates the expected position of the aircraft (on the hyperbola if there are two stations, or the aircraft's position if there are three or more stations) based on the time difference between the two receiving devices. The processing unit 4 uses the calculated aircraft position as a predicted value and the aircraft position included in the ADS-B signal as an actual value. If the difference between the predicted value and the actual value exceeds a certain threshold, it determines that the aircraft that transmitted the ADS-B signal is a spoof. In Figure 3, a transmitting station moving along hyperbola a is determined to be a legitimate airplane, while a transmitting station moving along hyperbola b is determined to be a spoof.

[0044] [Third system: Figure 4] The third system involves a processing unit 4 that calculates a predicted value by predicting a specific position in the direction of travel from the aircraft's position, speed, and direction of travel included in the received ADS-B signal. It then receives an ADS-B signal from the aircraft at the time it is predicted to have reached the specific position and obtains the aircraft's position included in the signal as an actual value. If the difference between the predicted value and the actual value exceeds a certain threshold, it determines that the aircraft that transmitted the ADS-B signal is a spoof. This reduces the possibility of disrupting air traffic control and improves aviation safety.

[0045] The third system will be explained with reference to Figure 4. Figure 4 is a schematic diagram of the third system. The third system, specifically as shown in Figure 4, is a flight path-based spoofing detection mechanism that utilizes the fact that the aircraft's position information is updated over time. The receiving device 1 acquires information on the aircraft's position (point A), speed, and direction of travel contained in the ADS-B signal received, and the processing device 4 predicts the aircraft's position (point B) after a specific time has elapsed. The predicted position of point B is taken as the predicted value.

[0046] Then, the receiving device 2 near point B receives the ADS-B signal from the aircraft, obtains the aircraft's position, speed, and direction of travel information contained in the ADS-B signal, and sets the aircraft's position near point B as the measured value. If the difference between the predicted value and the measured value exceeds a certain threshold, the processing unit 4 determines that the aircraft is a spoof.

[0047] [Application Examples] This system is implemented using one of the first to third systems, but it may also be equipped with both the first and second systems and perform spoofing detection on both to make a determination, or it may be a combination of the first and third systems, or the second and third systems, or it may be equipped with all of the first to third systems and perform spoofing detection on all of them to make a determination. Furthermore, although the system is described as having three separate systems, the hardware configuration is common to all of them, and the receiving devices 1 and 2 and the processing device 4 each contain a program for software-based impersonation detection.

[0048] [Effects of the embodiment] According to this system, receiving devices 1 and 2 continuously receive responses to questions sent to transponders installed on aircraft as ADS-B signals. Processing device 4 obtains the difference between a predicted value obtained from the continuously received ADS-B signals and the actual measured value corresponding to the predicted value. If this difference exceeds a certain threshold, it is determined that the aircraft that transmitted the ADS-B signal is a spoof. This reduces the possibility of disrupting air traffic control and improves aviation safety. [Industrial applicability]

[0049] The present invention is suitable for a spoofing detection system that can improve aviation safety by utilizing ADS-B signals used in secondary radar for air traffic control, thereby reducing the possibility of disrupting air traffic control. [Explanation of Symbols]

[0050] 1...Receiving device, 2...Receiving device, 3...Transmitting device, 4...Processing device, 5...Display device, 11...Omnidirectional antenna, 12,22,32...High-frequency section, 13,23,33...Signal processing unit, 14,24...High-precision time server, 15,25,35,43...Network device, 21,31...Directional antenna, 41...Central processing unit, 42...External storage device

Claims

1. An aircraft impersonation detection system that continuously receives responses to questions sent to an aircraft-mounted transponder as ADS-B signals using a first receiver and a second receiver, and detects aircraft impersonation. An impersonation detection system characterized by having a processing device that obtains a first difference between a first predicted value of the Doppler shift amount obtained from the position, speed, and direction of travel of an aircraft included in the data of the ADS-B signal received on a regular basis by the first receiving device and a first measured value of the Doppler shift amount calculated from the frequency of the radio waves of the ADS-B signal and the transmission frequency of the transponder, corresponding to the first predicted value; a second difference between a second predicted value of the Doppler shift amount obtained from the position, speed, and direction of travel of an aircraft included in the data of the ADS-B signal received on a regular basis by the second receiving device and a second measured value of the Doppler shift amount calculated from the frequency of the radio waves of the ADS-B signal and the transmission frequency of the transponder, corresponding to the second predicted value; and if the value obtained by subtracting the second difference from the first difference exceeds a certain threshold, it determines that the aircraft that transmitted the ADS-B signal is an impersonator.

2. An aircraft impersonation detection system that continuously receives responses to questions sent to an aircraft-mounted transponder as ADS-B signals using a first receiver and a second receiver, and detects aircraft impersonation. The processing device acquires the reception time of the ADS-B signal radio waves received by the first receiving device and the aircraft's position information included in the ADS-B signal data, the reception time of the ADS-B signal radio waves received by the second receiving device and the aircraft's position information included in the ADS-B signal data, calculates the aircraft's hyperbola from the time difference of the reception times based on the aircraft's position information acquired by the first and second receiving devices to obtain a predicted value of the aircraft's position, and determines that the aircraft that transmitted the ADS-B signal is a spoof if the difference between the predicted value and the actual value of the position on the hyperbola exceeds a certain threshold.

3. An aircraft impersonation detection system that continuously receives responses to questions sent to an aircraft-mounted transponder as ADS-B signals using a first receiver and a second receiver, and detects aircraft impersonation. The processing device predicts a specific position in the direction of travel from the aircraft's position information, speed, and direction of travel information contained in the ADS-B signal data received by the first receiving device and calculates a predicted value; receives the ADS-B signal from the aircraft at the time when the aircraft is predicted to have reached the specific position with the second receiving device near the specific position and obtains the aircraft's position information contained in the signal data as an actual value; and determines that the aircraft that transmitted the ADS-B signal is a spoof if the difference between the predicted value and the actual value exceeds a certain threshold.

4. An impersonation detection system characterized by comprising the impersonation detection system according to claim 1 and the impersonation detection system according to claim 2.

5. An impersonation detection system characterized by comprising the impersonation detection system according to claim 1 and the impersonation detection system according to claim 3.

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