CN112615670A - Method for judging terahertz communication eavesdropping - Google Patents

Abstract

The invention discloses a method for judging that a terahertz communication is eavesdropped, comprising: using a backscattering parameter in a terahertz communication system to determine whether there is eavesdropping; firstly defining a backscattering parameter S ₁₈₀ to quantify the size of the change, When there is no small object within the transmission beam, S ₁₈₀ =0, the channel is considered to be safe. When there is a small object in the beam of line-of-sight transmission, S ₁₈₀ >0, and a threshold value is preset according to the specific situation of the communication system. Once the backscatter parameter is higher than the threshold value, it is considered that the communication system has eavesdropping. The advantage of the present invention is: as an index for judging whether the terahertz communication environment is safe or not. Greatly improve the security of terahertz communication systems.

Description

A method for judging that terahertz communication has been eavesdropped

technical field

The invention relates to the technical field of terahertz communication anti-eavesdropping, in particular to a method for judging that terahertz communication is eavesdropped.

Background technique

The openness of the wireless channel easily leads to the easy interception of the key in the process of key distribution and exchange, which makes the method of adopting key encryption technology to maintain information security face a huge challenge.

As one of the key technologies of 6G mobile communication, terahertz communication has important national strategic significance. It is foreseeable that in the near future, data such as personal privacy, financial data, business information and even data related to national security can be transmitted through terahertz communication systems, which makes its confidentiality one of the key issues to be solved urgently in future wireless communication. one. There are few research work on the physical layer security of terahertz communication at home and abroad, and there is no relevant existing technology proposed.

Compared to traditional bands used for communications, millimeter-wave bands with narrow beams and high directional characteristics are generally considered more secure and less prone to eavesdropping. However, the research of an international team led by Professor Edward Knightly of Rice University in the United States shows that if there is a small object that can reflect the signal in the transmission beam, the physical layer security of the millimeter wave communication link will be seriously threatened. The eavesdropping receiver will be able to successfully decode the transmitted information from part of the signal reflected by the object.

Faced with potential security threats, the team proposed to use the signal occlusion rate of the receiver to detect whether there is eavesdropping, which is defined as follows:

where S _receiver is the actual signal strength received by the receiver, and S _optimal is the ideal received signal strength. From the expression of the signal occlusion rate, when there is no occlusion in the transmission beam, the signal occlusion rate is 0; when there is an occlusion, the signal occlusion rate is greater than zero; when the signal is completely blocked, the signal occlusion rate will be 1 . According to actual needs, an occlusion rate threshold value can be preset manually (the threshold value should be in the (0,1) interval). Once the detected signal occlusion rate is greater than the threshold value, it can be considered that the chain The road is not safe, that is, there is eavesdropping.

In the face of a complex communication link environment, it is not enough to simply use the signal blocking rate detected by the receiving end to conduct eavesdropping detection, because the signal blocking rate is only related to the signal strength of the receiving end. In many cases, such as: small objects are effective The occlusion area is much smaller than the beam transmission area, the transmittance of small objects to electromagnetic waves in the transmission frequency band is high, and the small objects have diffraction phenomena at the edges due to their own shapes, etc. Even if eavesdropping exists, the signal occlusion rate is still lower than the preset door. limit, this single indicator will not be able to successfully detect eavesdropping.

SUMMARY OF THE INVENTION

Aiming at the defects of the prior art, the present invention provides a method for judging that a terahertz communication is eavesdropped, and solves the defects existing in the prior art.

In order to realize the above purpose of the invention, the technical scheme adopted by the present invention is as follows:

A method for judging that a terahertz communication is eavesdropped, comprising: using a backscatter parameter in a terahertz communication system to determine whether there is eavesdropping;

First, the backscattering parameter _S180 is defined to quantify the magnitude of the change. The expression of the backscattering parameter ( _S180 ) is as follows:

是没有小物体存在时发射机处接收到的信号信噪比，

是有小物体时的发射机处的信噪比。in,

is the signal-to-noise ratio of the signal received at the transmitter when no small objects are present,

is the signal-to-noise ratio at the transmitter when there is a small object.

When there are no small objects in the beam of line-of-sight transmission, S ₁₈₀ =0, the channel is considered to be safe.

When there is a small object in the beam of line-of-sight transmission, S ₁₈₀ >0, a threshold value is preset according to the specific situation of the communication system, and the threshold value ranges from 0 to 1. Once the backscattering parameter is higher than the threshold value , it is considered that the communication system has eavesdropping.

Compared with the prior art, the advantages of the present invention are:

The backscattering parameter is affected by the scattering phenomenon of small objects, and can be used as an indicator to judge whether the terahertz communication environment is safe or not. Because its principle is different from the signal occlusion rate, the backscattering parameters can be applied simultaneously with the signal occlusion rate to make up for the lack of the signal occlusion rate and greatly improve the security of the terahertz communication system.

Description of drawings

FIG. 1 is a diagram of a terahertz communication link according to an embodiment of the present invention.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below according to the accompanying drawings and examples.

Figure 1 shows a terahertz communication link with eavesdropping. The link consists of a transmitter, two receivers, and a small object. The transmitter and receiver transmit information through the line-of-sight link, in the transmission beam memory. In a small object that can reflect or flash part of the signal to the eavesdropping receiver, a non-line-of-sight eavesdropping channel will be created, through which the eavesdropping receiver can obtain the transmission information.

The transmitter part consists of a waveguide-coupled horn antenna and a dielectric lens (5cm in diameter and 7.5cm in focal length). The carrier frequency of the transmitter is 200GHz, and the measured far-field beam pattern has a directivity of 34dBi, which corresponds to the transmitter. The divergence angle is about 4°. The transmitter signal is modulated using an amplitude shift keying (ASK) pulse generator with a transmission rate of 1 Gbit/s. The technical solution requires that the transmitting end device is a terahertz signal source with both transmitting and receiving functions. Legitimate reception and eavesdropping receivers use the exact same horn antenna and dielectric lens, so they have the same sensitivity. The signal detected by the receiver is amplified and analyzed in real time using a bit error rate tester.

According to the above communication model, small objects in the transmission beam will block part of the signal, which will reduce the signal strength of the receiver. In the terahertz frequency band (0.1–10 THz), the scattering phenomenon plays a dominant role, and its important feature is that the terahertz waves scattered by small objects propagate to all directions in space. Once the eavesdropping party adopts this periscope eavesdropping method, some signals must be scattered towards the direction of the transmitter by small objects. At the same time, the surface of the receiver horn antenna will also reflect part of the signal back to the direction of the receiver along the line-of-sight link. If there are small objects in the beam that work together with the eavesdropping receiver, then this part of the reflected signal will also be affected to a certain extent. degree of occlusion. Considering the above two factors, the existence of eavesdropping will cause the change of the received signal strength at the transmitter location. When the scattered signal is strong, the received signal strength at the transmitter will increase. Intensity will decrease.

Based on the change in signal strength at the transmitter, we define a backscatter parameter (S ₁₈₀ ) to quantify the magnitude of the change as an effective indicator for eavesdropping detection. The expression of the scattering parameter (S ₁₈₀ ) is as follows:

是没有小物体存在时发射机处接收到的信号信噪比，

是有小物体时的发射机处的信噪比。当视距传输的波束内没有小物体时，S₁₈₀＝0，可以认为该信道是安全的。当视距传输的波束内存在小物体时，S₁₈₀>0，我们可以根据通信系统的具体情况预先设定一个门限值(如：S₁₈₀>0.5)，一旦后向散射参数高于门限值，我们将认为该通信系统存在窃听。in,

is the signal-to-noise ratio of the signal received at the transmitter when no small objects are present,

is the signal-to-noise ratio at the transmitter when there is a small object. When there are no small objects in the beam of line-of-sight transmission, S ₁₈₀ =0, the channel can be considered safe. When there is a small object in the beam of line-of-sight transmission, S ₁₈₀ >0, we can preset a threshold value according to the specific situation of the communication system (eg: S ₁₈₀ >0.5), once the backscattering parameter is higher than the threshold value, we will consider this communication system to be eavesdropping.

Taking the scattering phenomenon in the terahertz band into account, the backscattering parameter is an effective indicator for detecting eavesdropping.

Those of ordinary skill in the art will appreciate that the embodiments described herein are intended to help readers understand the implementation method of the present invention, and it should be understood that the protection scope of the present invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific modifications and combinations without departing from the essence of the present invention according to the technical teachings disclosed in the present invention, and these modifications and combinations still fall within the protection scope of the present invention.

Claims (1)

1. A method for judging that terahertz communication is intercepted comprises the following steps: judging whether eavesdropping exists or not by utilizing backscattering parameters in a terahertz communication system;

first a backscattering parameter S is defined₁₈₀To quantify the magnitude of the change, the backscattering parameter (S)₁₈₀) The expression of (a) is as follows:

wherein,

is the signal-to-noise ratio of the signal received at the transmitter in the absence of a small object,

is the signal-to-noise ratio at the transmitter with a small object;

when there is no small object in the line-of-sight transmitted beam, S₁₈₀When the channel is equal to 0, the channel is considered to be safe;

when there is a small object in the line-of-sight transmitted beam, S₁₈₀>And 0, presetting a threshold value according to the specific condition of the communication system, wherein the threshold value range is 0-1, and once the backscattering parameter is higher than the threshold value, the communication system is determined to have wiretapping.

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