Secret channel construction method based on OOK modulation NB-IoT amplitude, electronic equipment and medium

Abstract

The invention discloses a secret channel construction method based on OOK modulation NB-IoT amplitude, an electronic device and a medium. On one hand, OOK is fully utilized to modulate the NB-IoT amplitude and construct a new secret channel, so that compared with a traditional method, the problem that a channel for leaking sensitive information possibly exists in information transmission of an NB-IoT network can be solved, and on the other hand, on the premise that normal channel communication is kept through the secret channel, the frequency domain channel characteristics of the NB-IoT are utilized, and therefore the information transmission efficiency of the NB-IoT network is improved. And the information is hidden in the subcarrier of the NB-IoT channel, so that secret transmission of the information is realized, and the concurrent transmission capacity of the legal channel and the secret channel is further improved. According to the method, the capacity of the secret channel can be improved on the premise that legal communication is not affected, an idea is provided for constructing the secret channel on the NB-IoT physical layer, and the method has a good popularization prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of low-power long-distance wide area networks, and more specifically, to a method for constructing a covert channel based on OOK modulation of NB-IoT amplitude, an electronic device, and a medium. Background Art

[0002] Among many Internet of Things technologies, low-power wide area network (LPWAN) is an emerging wireless Internet of Things technology that supports long-distance communication up to several kilometers, greatly increasing the connectivity and efficiency of the Internet of Things. Among them, narrowband Internet of Things (NB-IoT) communication technology is a low-power wide area Internet of Things technology based on cellular networks, with advantages such as wide coverage, high connection density, long transmission distance, and high security. However, the security of NB-IoT is also a key research issue. Wireless communication faces common threats such as interference, replay attacks, and impersonation attacks, but covert channel attacks are rarely discussed.

[0003] A covert channel is a method of transmitting information by using abnormal communication methods in a computer system. It is an attack technology that is difficult to detect and has extremely high potential harmfulness. Currently, NB-IoT uses symmetric encryption to protect the security of the application layer and network layer. However, its security mechanism does not check the communication parameters of the physical layer, which makes NB-IoT vulnerable to covert channel attacks. Therefore, it is necessary to design a covert channel for NB-IoT, which can effectively improve the security of the device and also further improve the communication efficiency of Internet of Things devices to a certain extent. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for constructing a covert channel based on OOK modulation of NB-IoT amplitude, an electronic device, and a medium in view of the deficiencies of the prior art.

[0005] According to the first aspect of this specification, a method for constructing a covert channel based on OOK modulation of NB-IoT amplitude is provided, and the method includes:

[0006] S1. In a transmitter, by performing covert OOK modulation on the signal amplitude of NB-IoT, embedding the covert information as a covert channel into a legitimate channel, and propagating the covert information and the legitimate information together, including:

[0007] Select subcarriers, modulate the covert information onto the amplitude of the subcarriers by the OOK method, and design the covert channel amplitude A(t) = A c +A o where A o = αAc , where A c is the fixed modulation amplitude of the legal channel, and A o is the OOK modulation amplitude, α is the amplitude change ratio, and it satisfies where SNR is the signal-to-noise ratio;

[0008] Insert a synchronization header containing subcarrier selection information and the location information of the steganographic information embedding in each OFDM symbol;

[0009] S2. In the legal receiver, after receiving the signal, perform NB-IOT demodulation to obtain the legal information;

[0010] S3. In the steganographic receiver, after receiving the signal, extract the amplitude information of the signal, detect and separate the steganographic information embedded in the signal, including: perform NB-IOT demodulation on the received signal to obtain the original information; according to the information in the synchronization header, locate the subcarrier position and the steganographic information embedding position, and then perform standard OOK amplitude demodulation.

[0011] Furthermore, the selected subcarriers should satisfy: the number of subcarriers is large enough to make the hiding and transmission of information more secret and stable; the selection of subcarriers should avoid affecting the performance and stability of the communication system.

[0012] Furthermore, the modulation process of the subcarriers is specifically as follows: Two orthogonal signals I(t) and Q(t) are used. Each symbol corresponds to a point on the I / Q plane. The legal information data is mapped to four phase points on the complex plane. The subcarrier signal s0(t) is expressed as:

[0013] s0(t) = I(t)cos(2πf c t) + Q(t)sin(2πf c t)

[0014] where I(t) is the in-phase signal, Q(t) is the quadrature signal, f c is the subcarrier frequency, and each symbol lasts for a period of time to form a QPSK signal; The legal information data is obtained by discriminating the phase of the constellation diagram in the NB-IoT channel, and only the phase condition is required while the amplitude is fixed; The steganographic information is embedded in the amplitude of the subcarrier. The subcarrier signal s(t) after OOK amplitude modulation is expressed as:

[0015] s(t) = A(t)(I(t)cos(2πf c t) + Q(t)sin(2πf c t))

[0016] where A(t) is the designed amplitude of the steganographic channel.

[0017] Further, to avoid error codes and ensure the reliability of the covert channel, the value of the amplitude change ratio α is set between 1% and 5%.

[0018] Further, the legitimate receiver is a standard NB-IoT terminal device. After the legitimate receiver receives the signal, although the amplitude of the signal carries the covert information, the legitimate receiver only checks the frequency information of the signal and does not check the amplitude information, and the signal on the legitimate channel is demodulated as usual.

[0019] Further, in the covert receiver, to perform standard OOK amplitude demodulation, it is necessary to first extract the discrete carrier frequency components from the subcarriers and restore the original subcarriers. Specifically: use the local carrier cos(2πf c t) and sin(2πfc c t) to multiply with the received subcarrier s(t), extract the I / Q components, perform low-pass filtering to filter out the high-frequency components and only retain the I / Q signals, and extract the covert information by analyzing the amplitude of the I / Q signals.

[0020] Further, considering the balance between the security and reliability of the covert channel, an encryption algorithm is used to encrypt the covert information.

[0021] According to the second aspect of this specification, an electronic device is provided, including a memory and a processor, and the memory is coupled to the processor; wherein, the memory is used to store program data, and the processor is used to execute the program data to implement the method for constructing a covert channel based on OOK modulation NB-IoT amplitude as described in the first aspect.

[0022] According to the third aspect of this specification, a computer-readable storage medium is provided, on which a computer program is stored, and when the program is executed by a processor, it implements the method for constructing a covert channel based on OOK modulation NB-IoT amplitude as described in the first aspect.

[0023] According to the fourth aspect of this specification, a computer program product is provided, including a computer program / instructions, and when the computer program / instructions are executed by a processor, it implements the method for constructing a covert channel based on OOK modulation NB-IoT amplitude as described in the first aspect.

[0024] The present invention has the following beneficial effects compared with the prior art:

[0025] 1. The present invention makes full use of the NB-IoT frequency-domain channel characteristics in the concurrent transmission scenario of the low-power long-range wide-area network, and improves the parallel transmission capacity of covert information. The present invention utilizes the fact that the amplitude modulation covert channel and the frequency modulation channel are completely orthogonal, modulates the NB-IoT amplitude by the OOK method, and constructs a covert channel, which can further improve the parallel transmission capacity of the covert channel.

[0026] 2. The present invention designs a method to construct a covert channel by utilizing the characteristics of NB-IoT, which can improve the capacity of the covert channel without affecting legitimate communication, providing an idea for constructing a covert channel at the physical layer of NB-IoT.

[0027] 3. Based on the orthogonal frequency division multiplexing (OFDM) modulation technology of NB-IoT, the present invention proposes a method for subcarrier selection and information extraction, providing an idea for the construction of a covert channel and having good promotion prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0029] Figure 1 It is a flowchart of a method for constructing a covert channel based on the amplitude implementation of NB-IoT with OOK modulation provided by an embodiment of the present invention;

[0030] Figure 2 It is a schematic diagram of the principle of a method for constructing a covert channel based on the amplitude implementation of NB-IoT with OOK modulation provided by an embodiment of the present invention;

[0031] Figure 3 It is a schematic diagram of the structure of an electronic device provided by an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] In order to better understand the technical solutions of the present application, the following will describe the embodiments of the present application in detail with reference to the drawings.

[0033] It should be clear that the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present application.

[0034] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms of "a", "the", and "said" used in the embodiments of the present application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0035] Before introducing the method for constructing a covert channel based on the amplitude implementation of NB-IoT with OOK modulation provided by the present invention, the concepts of NB-IoT, OOK amplitude modulation, and covert channel will be briefly introduced.

[0036] NB-IoT communication technology is a low-power wide-area Internet of Things technology based on cellular networks. The NB-IoT communication technology uses narrowband modulation technology, that is, it uses narrowband carriers to achieve data transmission. Compared with traditional cellular communication, the NB-IoT communication technology has a narrower bandwidth and a slower transmission rate, but a higher connection density and a longer transmission distance. The NB-IoT communication technology adopts some new modulation and coding technologies at the physical layer, such as single-carrier frequency-domain equalization (SC-FDE), cyclic prefix (CP), etc., to improve the stability and reliability of communication.

[0037] On-off keying (OOK) is a special case of amplitude-shift keying (ASK). ASK is a commonly used modulation technology. When transmitting "1", the transmitter sends a higher carrier amplitude; when transmitting "0", the simplest way is to send a lower carrier amplitude. OOK modulation is a simpler ASK method. When transmitting "0", no carrier signal is output.

[0038] A covert channel is a communication method usually used to hide the transmission of information to prevent detection or discovery. This channel uses parameters in the communication system that are not often monitored or subtle changes in the communication path to transmit hidden information. In NB-IoT communication, the main reason for the existence of covert channels is that the NB-IoT security mechanism does not check the physical layer communication parameters (such as signal amplitude, phase, and waveform). This enables attackers to construct covert channels at the physical layer (PHY), resulting in the risk of information leakage.

[0039] In constructing a covert channel for the NB-IoT communication physical layer, ordinary NB-IoT channels are often used as legitimate channels. The vast majority of commercial NB-IoT devices in use are already integrated devices. This invention focuses on the security vulnerability problems existing in the NB-IoT physical layer and proposes a brand-new method for constructing a covert channel based on the amplitude of NB-IoT implemented by OOK modulation. It mainly improves the security of devices through the NB-IoT covert channel modulated by OOK, and at the same time improves the communication efficiency of NB-IoT Internet of Things devices.

[0040] An amplitude modulation covert channel is a communication method that hides information by modulating the amplitude of the original information. In this channel, low-frequency information signals are embedded by modulating the amplitude of high-frequency signals, thus achieving information hiding and transmission. In the design of an amplitude modulation covert channel based on NB-IoT, the present invention will utilize the frequency-domain channel characteristics of NB-IoT to hide information in the subcarriers of the NB-IoT channel, realizing the covert transmission of information. Since NB-IoT uses frequency modulation, in order not to affect the transmission of normal data during the use of the covert channel, the covert channel should be completely orthogonal to the frequency modulation channel. The present invention selects the OOK modulation method to modulate the low-frequency information signal. The OOK modulation method controls the turning on and off of a sine carrier with a unipolar non-return-to-zero code sequence. Through the NB-IoT covert channel method modulated by the OOK modulation method, covert communication based on the covert channel can be achieved.

[0041] As Figure 1 、 Figure 2 shown, the covert channel construction method based on OOK modulation NB-IoT amplitude provided by the present invention specifically includes the following steps:

[0042] Step 1, in the transmitter, through the covert OOK modulation of the signal amplitude of normal NB-IoT, the covert information is carried and embedded into the legal channel as a covert channel without modifying the data packet format of the original legal channel. The covert channel propagates the covert information and the legal information together by being embedded into the legal channel. The specific process of embedding the covert information is as follows:

[0043] 1.1 Select subcarriers: The NB-IoT channel adopts orthogonal frequency division multiplexing (OFDM) modulation technology, which allocates spectrum resources to multiple subcarriers. The bandwidth of each subcarrier is 15 kHz. The OFDM modulation technology modulates multiple subcarriers to transmit information simultaneously, decomposing the high-speed serial input into multiple lower-rate information streams for transmission. These subcarriers are orthogonal to each other within a symbol period. The present invention selects several of these subcarriers to hide the covert information in these subcarriers. The selected subcarriers should meet the following conditions: on the one hand, the number of subcarriers should be large enough to make the hiding and transmission of information more covert and stable; on the other hand, the selection of subcarriers should avoid affecting the performance and stability of the communication system.

[0044] 1.2 Amplitude modulation: After selecting the subcarriers, the covert information is modulated onto the amplitude of the subcarriers by the OOK method. In the amplitude modulation covert channel, information can be achieved by changing the amplitude of the high-frequency signal, and the information is modulated onto the amplitude of a certain subcarrier. During the modulation of a certain subcarrier, two orthogonal signals I(t) and Q(t) are used. Each symbol corresponds to a point on the I / Q plane. In this way, the legal information data is mapped to 4 phase points on the complex plane.

[0045] s0(t) = I(t)cos(2πf c t) + Q(t)sin(2πf c t)

[0046] Wherein, s0(t) is the sub - carrier signal, I(t) is the in - phase signal, Q(t) is the quadrature signal, and f c is the sub - carrier frequency. Each symbol (2 bits) lasts for a period of time to form a QPSK signal. The NB - IoT channel obtains legal information data by discriminating the phase of the constellation diagram, and only requires the phase condition while the amplitude is fixed. The present invention embeds the hidden information into the amplitude of the sub - carrier:

[0047] s(t) = A(t)(I(t)cos(2πf c t) + Q(t)sin(2πfc c t))

[0048] Wherein, s(t) is the sub - carrier signal after OOK amplitude modulation, A(t) is the designed amplitude of the hidden channel, and the design of A(t) should meet the following requirements:

[0049] A(t) = A c + A o

[0050] A o = αA c

[0051] Wherein, A c is the fixed modulation amplitude of the legal channel, A o is the OOK modulation amplitude, and α is the amplitude change ratio.

[0052] Specifically, the value of α needs to be controlled within a reasonable range. The value of α cannot be too large. According to the Shannon - Hartley theorem, the relationship between the maximum data transmission rate C of a communication system and the signal - to - noise ratio SNR and the bandwidth B is as follows:

[0053] C = Blog2(1 + SNR)

[0054] Wherein, SNR is directly related to the power (or amplitude) of the signal. When α is too large, the power of the signal will change significantly, which may cause the legal receiver to misjudge the original signal, equivalently resulting in a decrease in the signal - to - noise ratio SNR, and thus a decrease in the data transmission rate C. At the same time, when α is too large, the secrecy of the channel will decrease.

[0055] At the same time, the value of α cannot be too small to avoid the amplitude change of the hidden channel being masked by noise. A o must satisfy being greater than the noise standard deviation σ noise , wherein:

[0056]

[0057] Simplification results in:

[0058]

[0059] For example, when SNR = 30 dB, the amplitude change ratio α should be at least greater than 3.16%. In practical applications, in order to avoid bit errors and ensure the reliability of the covert channel, α usually remains between 1% and 5%. Especially in a low SNR environment, α needs to be appropriately increased. As SNR increases, α can be correspondingly decreased to further ensure the secrecy of the channel.

[0060] Step 2: The legitimate receiver is a standard terminal device, usually a commercial NB-IoT node. After the legitimate receiver receives the signal, although the amplitude of the signal carries the covert information, the legitimate receiver only checks the frequency information of the signal and does not check the amplitude information, and the signal on the legitimate channel is demodulated as usual.

[0061] Specifically, the security mechanism of NB-IoT protects the upper layers except the physical layer and only checks the frequency information of the signal without checking the amplitude information, which makes NB-IoT vulnerable to covert channel attacks. At the same time, legitimate agents can use the "covert" channel to increase the communication of legitimate applications.

[0062] Step 3: Design a covert receiver for extracting the amplitude information of the signal after receiving the signal, detecting and separating the covert information embedded in the signal.

[0063] Step 4: Through signal processing, the covert receiver can accurately extract the amplitude information of the signal, which contains the covert information. The covert receiver needs to first locate the subcarrier position and the target position of the covert information on the subcarrier, and then perform standard demodulation. Specifically, it includes the following sub-steps:

[0064] 4.1 Extract the subcarrier channel;

[0065] 4.2 Find the embedding position of the covert information in the subcarrier channel;

[0066] 4.3 Perform standard demodulation on the covert information at the target position.

[0067] During modulation, a synchronization header is inserted into each OFDM symbol for synchronization and information extraction. In the synchronization header, information such as subcarrier selection and the position of embedded covert information is included so that the covert receiver can correctly extract the information. In the covert receiver, first, the received signal needs to be demodulated by conventional NB-IoT to obtain the original information. Then, according to the information in the synchronization header, the subcarrier where the covert information is embedded and the specific embedding position need to be found, and then standard OOK amplitude demodulation is performed.

[0068] To perform standard OOK amplitude demodulation on the covert information at the target position, it is necessary to first extract the discrete carrier frequency components from the subcarrier and restore the original subcarrier. Specifically: Use the local carrier cos(2πf c t) and sin(2πf c t) to multiply with the received subcarrier s(t), extract the I / Q components, perform low-pass filtering to filter out the high-frequency components and only retain the I / Q signals, and extract the covert information through the amplitude analysis of the I / Q signals. For the in-phase signal I(t), specifically:

[0069] I′(t) = 2s(t)cos(2πf c t)

[0070] I(t) = 2s0(t)cos(2πf c t)

[0071] I′(t) = A(t)I(t)

[0072] where I′(t) is the in-phase signal demodulated after embedding the covert information. For the quadrature signal Q(t), specifically:

[0073] Q′(t) = 2s(t)sin(2πf c t)

[0074] Q(t) = 2s0(t)sin(2πfc c t)

[0075] Q′(t) = A(t)Q(t)

[0076] where Q′(t) is the quadrature signal demodulated after embedding the covert information.

[0077] Therefore, the covert information can be obtained by extracting the amplitude A(t). Through this step, the legitimate agent can increase the communication of the legitimate application program of the covert channel without affecting the legitimate channel.

[0078] The security of the amplitude modulation covert channel is not absolute and may be eavesdropped or cracked. Therefore, if it is to be used formally, the balance between the security and reliability of the covert channel also needs to be considered. For example, encryption algorithms are used to encrypt the covert information.

[0079] Correspondingly, the present application further provides an electronic device, including: one or more processors; a memory for storing one or more programs; when the one or more programs are executed by the one or more processors, the one or more processors implement the method for constructing a covert channel based on OOK modulation NB-IoT amplitude as described above. As Figure 3 shown, it is a hardware structure diagram of any device with data processing capabilities where the method for constructing a covert channel based on OOK modulation NB-IoT amplitude provided by an embodiment of the present invention is located. In addition to Figure 3 the processors, memory, and network interfaces shown, any device with data processing capabilities where the device in the embodiment is located usually further includes other hardware according to the actual functions of the device with data processing capabilities, which will not be elaborated here.

[0080] Correspondingly, the present application further provides a computer-readable storage medium, on which computer instructions are stored, and when the instructions are executed by a processor, the method for constructing a covert channel based on OOK modulation NB-IoT amplitude as described above is implemented. The computer-readable storage medium may be an internal storage unit of any device with data processing capabilities described in any of the foregoing embodiments, such as a hard disk or a memory. The computer-readable storage medium may also be an external storage device, such as a plug-in hard disk, a Smart Media Card (SMC), an SD card, a Flash Card, etc. equipped on the device. Further, the computer-readable storage medium may also include both an internal storage unit of any device with data processing capabilities and an external storage device. The computer-readable storage medium is used to store the computer program and other programs and data required by any device with data processing capabilities, and may also be used to temporarily store the data that has been output or will be output.

[0081] After considering the specification and practicing the content disclosed herein, those skilled in the art will readily think of other implementation manners of the present application. The present application is intended to cover any variations, uses, or adaptations of the present application, which follow the general principles of the present application and include the common general knowledge or conventional technical means in the technical field not disclosed in the present application. The specification and the embodiments are only regarded as exemplary.

[0082] It should be understood that the present application is not limited to the exact structure described above and shown in the drawings, and various modifications and changes can be made without departing from its scope.

[0083] The above are only the preferred embodiments of the present invention. Although the present invention has been disclosed above in preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make many possible changes and modifications to the technical solution of the present invention, or modify it into equivalent embodiments with equivalent changes, without departing from the scope of the technical solution of the present invention. Therefore, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for constructing a covert channel based on the amplitude of NB-IoT implemented by OOK modulation, characterized in that, Including: S1. In a transmitter, by performing covert OOK modulation on the signal amplitude of NB-IoT, the covert information is carried as a covert channel and embedded into the legitimate channel, and the covert information and the legitimate information are propagated together, including: Select subcarriers and modulate the secret information onto the amplitude of the subcarriers by the OOK method. Design the amplitude of the covert channel \(A(t)=A\) c +A o , \(A\) o =\(\alpha A\) c , where \(A\) c is the fixed modulation amplitude of the legitimate channel, \(A\) o is the OOK modulation amplitude, \(\alpha\) is the amplitude change ratio, and it satisfies where SNR is the signal-to-noise ratio; Inserting a synchronization header containing subcarrier selection information and covert information embedding position information in each OFDM symbol; S2. In a legitimate receiver, after receiving the signal, perform NB-IOT demodulation to obtain the legitimate information; S3. In a covert receiver, after receiving the signal, extract the amplitude information of the signal, detect and separate the covert information embedded in the signal, including: performing NB-IOT demodulation on the received signal to obtain the original information; according to the information in the synchronization header, locate the subcarrier position and the covert information embedding position, and then perform standard OOK amplitude demodulation.

2. The method for constructing a covert channel based on the amplitude of NB-IoT implemented by OOK modulation according to claim 1, wherein The selected subcarriers should satisfy: the number of subcarriers is large enough to make the hiding and transmission of information more covert and stable; the selection of subcarriers should avoid affecting the performance and stability of the communication system.

3. The method for constructing a covert channel based on the amplitude of NB-IoT implemented by OOK modulation according to claim 1, wherein The modulation process of the subcarriers is specifically as follows: Two orthogonal signals I(t) and Q(t) are used. Each symbol corresponds to a point on the I / Q plane. The legitimate information data is mapped to four phase points on the complex plane. The subcarrier signal s0(t) is expressed as: s0(t) = I(t)cos(2πf c t) + Q(t)sin(2πf c t) where I(t) is the in-phase signal, Q(t) is the quadrature signal, and f c is the subcarrier frequency, and each symbol lasts for a period of time to form a QPSK signal; the NB-IoT channel obtains legal information data by discriminating the phase of the constellation diagram, only requires the phase condition while the amplitude is fixed; the hidden information is embedded on the amplitude of the subcarrier, and the subcarrier signal s(t) after OOK amplitude modulation is expressed as: s(t) = A(t)(I(t)cos(2πf c t)+Q(t)sin(2πf c t)) where A(t) is the designed amplitude of the covert channel.

4. The method for constructing a covert channel based on the amplitude of NB-IoT implemented by OOK modulation according to claim 1, wherein To avoid error codes and ensure the reliability of the covert channel, the value of the amplitude change ratio α is set between 1% and 5%.

5. The method for constructing a covert channel based on the amplitude of NB-IoT implemented by OOK modulation according to claim 1, wherein The legitimate receiver is a standard NB-IoT terminal device. After the legitimate receiver receives the signal, although the amplitude of the signal carries the covert information, the legitimate receiver only checks the frequency information of the signal and does not check the amplitude information, and the signal of the legitimate channel is demodulated as usual.

6. The method for constructing a covert channel based on the amplitude of NB-IoT implemented by OOK modulation according to claim 3, wherein In the described covert receiver, for standard OOK amplitude demodulation, it is necessary to first extract discrete carrier frequency components from the subcarrier to recover the original subcarrier. Specifically: Multiply the local carrier cos(2πf c t) and sin(2πf c t) with the received subcarrier s(t), extract the I / Q components, perform low-pass filtering to filter out the high-frequency components and only retain the I / Q signals, and extract the covert information by analyzing the amplitudes of the I / Q signals.

7. The method for constructing a covert channel based on the amplitude implementation of NB-IoT with OOK modulation according to claim 1, wherein Considering the balance between the security and reliability of the covert channel, an encryption algorithm is used to encrypt the covert information.

8. An electronic device, comprising a memory and a processor, characterized in that, The memory is coupled to the processor; wherein, the memory is used to store program data, and the processor is used to execute the program data to implement the method for constructing a covert channel based on OOK modulation NB-IoT amplitude as described in any one of claims 1-7.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it implements the method for constructing a covert channel based on OOK modulation NB-IoT amplitude as described in any one of claims 1-7.

10. A computer program product comprising a computer program / instructions, characterized in that, When the computer program / instructions are executed by the processor, it implements the method for constructing a covert channel based on OOK modulation NB-IoT amplitude as described in any one of claims 1-7.

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