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

Abstract

The application discloses a secret channel construction method based on OOK modulation NB-IoT amplitude, an electronic device and a medium. The application makes full use of OOK modulation NB-IoT amplitude, constructs a new secret channel, and can solve the problem that sensitive information may be leaked in the channel during information transmission of the NB-IoT network compared with a traditional method. On the other hand, under the premise of maintaining normal channel communication, the information is hidden in the subcarriers of the NB-IoT channel by utilizing the frequency domain channel characteristics of the NB-IoT, secret transmission of the information is realized, and the concurrent transmission capacity of the legal channel and the secret channel is further improved. The application can improve the capacity of the secret channel without affecting the legal communication, provides a train of thought for constructing the secret channel at the NB-IoT physical layer, and has a good popularization prospect.

Description

Technical Field

[0001] This invention relates to the field of low-power long-distance wide-area network technology, and more specifically, to a method, electronic device, and medium for constructing a covert channel based on OOK modulation of NB-IoT amplitude. Background Technology

[0002] Among numerous IoT technologies, Low Power Wide Area Network (LPWAN) is an emerging wireless IoT technology that supports long-distance communication of up to several kilometers, greatly increasing the connectivity and efficiency of the IoT. Narrowband Internet of Things (NB-IoT) communication technology is a low-power wide-area IoT technology based on cellular networks, boasting 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 and replay attacks, and impersonation attacks, but covert channel attacks have received little discussion.

[0003] Covert channels refer to methods of transmitting information through unconventional communication methods within a computer system. They are difficult to detect and employ attack techniques with extremely high potential for harm. Current NB-IoT uses symmetric encryption to protect the application and network layers; however, its security mechanisms do not check the communication parameters of the physical layer, making NB-IoT vulnerable to covert channel attacks. Therefore, designing covert channels for NB-IoT is necessary, as it can effectively improve device security and, to some extent, further enhance the communication efficiency of IoT devices. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing a method, electronic device, and medium for constructing covert channels based on OOK modulation of NB-IoT amplitude.

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

[0006] S1, in the transmitter, the NB-IoT signal amplitude is secretly modulated using OOK, carrying secret information and embedded into the legitimate channel as a secret channel, thus propagating the secret and legitimate information together, including:

[0007] Select a subcarrier, and use the OOK method to modulate the covert information onto the amplitude of the subcarrier. Design the covert channel amplitude A(t) = A c +A o A o =αAc A c For a fixed modulation amplitude of a legitimate channel, A o Let be the OOK modulation amplitude, α be the amplitude variation ratio, and satisfy . Where SNR is the signal-to-noise ratio;

[0008] A synchronization header containing subcarrier selection information and hidden information embedded in the location information is inserted into each OFDM symbol;

[0009] S2, In the legitimate receiver, after receiving the signal, NB-IoT demodulation is performed to obtain legitimate information;

[0010] S3, in the covert receiver, after receiving the signal, extracts the amplitude information of the signal, detects and separates the covert information embedded in the signal, including: performing NB-IOT demodulation on the received signal to obtain the original information; locating the subcarrier position and the embedding position of the covert information according to the information in the synchronization header, and then performing standard OOK amplitude demodulation.

[0011] Furthermore, the selection of subcarriers should satisfy the following requirements: the number of subcarriers should be sufficient to make the concealment and transmission of information more covert and stable; the selection of subcarriers should avoid affecting the performance and stability of the communication system.

[0012] Furthermore, the modulation process of the subcarrier is specifically as follows: two orthogonal signals I(t) and Q(t) are used, each symbol corresponding to a point on the I / Q plane, and the legitimate information data is mapped to four phase points on the complex plane. The subcarrier signal s0(t) is represented 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, and f c Given the subcarrier frequency, each symbol lasts for a period of time to form a QPSK signal; the NB-IoT channel obtains legitimate information data by determining the phase of the constellation diagram, requiring only phase conditions and having a fixed amplitude; the hidden information is embedded in the amplitude of the subcarrier, and 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 covert channel amplitude.

[0017] Furthermore, to avoid bit errors and ensure the reliability of the covert channel, the amplitude variation ratio α is set between 1% and 5%.

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

[0019] Furthermore, in the covert receiver, standard OOK amplitude demodulation requires first extracting discrete carrier frequency components from the subcarrier to recover the original subcarrier. Specifically, this involves using the local carrier cos(2πf) c t) and sin(2πfc c The I / Q components are multiplied by the received subcarrier s(t) and low-pass filtered to remove high-frequency components, leaving only the I / Q signals. Hidden information is then extracted by amplitude analysis of the I / Q signals.

[0020] Furthermore, considering the balance between security and reliability of covert channels, encryption algorithms are used to encrypt covert information.

[0021] According to a second aspect of this specification, an electronic device is provided, including a memory and a processor, the memory being 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 covert channel construction method based on OOK modulation NB-IoT amplitude as described in the first aspect.

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

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

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] 1. This invention fully utilizes the frequency domain channel characteristics of NB-IoT in concurrent transmission scenarios within low-power long-distance wide-area networks, thereby improving the parallel transmission capacity of covert information. This invention leverages the complete orthogonality of amplitude-modulated (AM) and frequency-modulated (FM) channels, modulating the NB-IoT amplitude using the OOK method to construct a covert channel, which can further enhance the parallel transmission capacity of the covert channel.

[0026] 2. This invention designs a covert channel that utilizes the characteristics of NB-IoT, which can increase the capacity of the covert channel without affecting legitimate communication, and provides a way to build a covert channel at the NB-IoT physical layer.

[0027] 3. Based on the orthogonal frequency division multiplexing (OFDM) modulation technology of NB-IoT, this invention proposes a method for subcarrier selection and information extraction, providing ideas for the construction of covert channels and showing good prospects for promotion. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a flowchart of a covert channel construction method based on OOK modulation NB-IoT amplitude implementation provided in an embodiment of the present invention;

[0030] Figure 2 This is a schematic diagram of the covert channel construction method based on OOK modulation NB-IoT amplitude implementation provided in an embodiment of the present invention;

[0031] Figure 3 This is a schematic diagram of the electronic device structure provided in an embodiment of the present invention. Detailed Implementation

[0032] To better understand the technical solution of this application, the embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0033] It should be understood that the described embodiments are merely some, not all, of the embodiments in this application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application.

[0034] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0035] Before introducing the covert channel construction method based on OOK modulation NB-IoT amplitude provided by this invention, we will briefly introduce the concepts of NB-IoT, OOK amplitude modulation and covert channel.

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

[0037] On-off keying (OOK) is a special case of amplitude shift keying (ASK). ASK is a commonly used modulation technique where a higher carrier amplitude is transmitted when a "1" needs to be transmitted, and a lower carrier amplitude is transmitted in the simplest way when a "0" needs to be transmitted. OOK modulation is a simpler form of ASK where no carrier signal is output when a "0" is transmitted.

[0038] A covert channel is a communication method typically used to conceal the transmission of information to prevent detection or discovery. This channel utilizes subtle changes in parameters or communication paths that are not frequently monitored within the communication system to transmit hidden information. In NB-IoT communication, the primary reason for the existence of covert channels is that the NB-IoT security mechanism does not check physical layer communication parameters (such as signal amplitude, phase, and waveform). This allows attackers to construct covert channels at the physical layer (PHY), leading to the risk of information leakage.

[0039] In constructing covert channels for the NB-IoT communication physical layer, ordinary NB-IoT channels are often used as legitimate channels, and most commercially deployed NB-IoT devices are already integrated with these channels. This invention addresses the security vulnerabilities existing in the NB-IoT physical layer and proposes a novel method for constructing covert channels based on OOK modulation of NB-IoT amplitude. This method primarily enhances device security and improves the communication efficiency of NB-IoT devices through the OOK-modulated NB-IoT covert channel.

[0040] Amplitude modulation (AM) covert channels are 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 a high-frequency signal, thereby achieving information hiding and transmission. In the design of an AM covert channel based on NB-IoT, this invention utilizes the frequency domain channel characteristics of NB-IoT to hide information within the subcarriers of the NB-IoT channel, achieving covert transmission. Since NB-IoT uses frequency modulation, the covert channel should be completely orthogonal to the frequency modulation channel to ensure that normal data transmission is not affected during the use of the covert channel. This invention chooses to use OOK modulation to modulate the low-frequency information signal. The OOK modulation method uses a unipolar non-return-to-zero code sequence to control the on / off state of the sinusoidal carrier. By using the OOK modulation method to modulate the NB-IoT covert channel, covert communication based on the covert channel can be achieved.

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

[0042] Step one: In the transmitter, the normal NB-IoT signal amplitude is secretly modulated using OOK, carrying secret information and embedded into the legitimate channel as a secret channel. Embedding the secret information does not modify the original data packet format of the legitimate channel. The secret channel propagates both the secret and legitimate information together by being embedded into the legitimate channel. The specific process of embedding the secret information is as follows:

[0043] 1.1 Subcarrier Selection: The NB-IoT channel employs Orthogonal Frequency Division Multiplexing (OFDM) modulation technology, allocating spectrum resources to multiple subcarriers. Each subcarrier has a bandwidth of 15kHz. 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 one symbol period. This invention selects several subcarriers to hide the secret information within them. The selected subcarriers should meet the following conditions: Firstly, the number of subcarriers should be sufficient to make the information hiding and transmission more covert and stable; secondly, the selection of subcarriers should avoid affecting the performance and stability of the communication system.

[0044] 1.2 Amplitude Modulation: After selecting a subcarrier, the covert information is modulated onto the subcarrier's amplitude using the OOK method. In amplitude-modulated covert channels, information can be modulated onto the amplitude of a specific subcarrier by changing the amplitude of a high-frequency signal. During the modulation of a subcarrier, two orthogonal signals I(t) and Q(t) are used, with each symbol corresponding to a point on the I / Q plane. Thus, legitimate information data is mapped to four phase points on the complex plane.

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

[0046] Where s0(t) is the subcarrier signal, I(t) is the in-phase signal, Q(t) is the quadrature signal, and f c The subcarrier frequency is used, and each symbol (2 bits) lasts for a period of time, forming a QPSK signal. The NB-IoT channel obtains legitimate information data by determining the constellation phase, requiring only phase conditions and a fixed amplitude. This invention embeds hidden information into the subcarrier amplitude:

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

[0048] Where s(t) is the subcarrier signal after OOK amplitude modulation, and A(t) is the designed covert channel amplitude. The design of A(t) should meet the following requirements:

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

[0050] A o =αA c

[0051] Among them, A c For a fixed modulation amplitude of a legitimate channel, A o α represents the OOK modulation amplitude, and α is the amplitude variation 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 bandwidth B is as follows:

[0053] C = Blog2(1 + SNR)

[0054] SNR is directly related to signal power (or amplitude). When α is too large, the signal power will change significantly, which may cause legitimate receivers to misinterpret the original signal, resulting in a decrease in the signal-to-noise ratio (SNR) and consequently a decrease in the data transmission rate (C). At the same time, an excessively large α will lead to a decrease in channel stealth.

[0055] At the same time, the value of α cannot be too small to avoid the amplitude changes of the covert channel being masked by noise. o It must satisfy a value greater than the noise standard deviation σ. noise ,in:

[0056]

[0057] Simplifying, we get:

[0058]

[0059] For example, when SNR = 30dB, the amplitude variation ratio α should be at least greater than 3.16%. In practical applications, to avoid bit errors and ensure the reliability of the covert channel, α is usually kept between 1% and 5%, especially in low SNR environments where α needs to be appropriately increased. As SNR increases, α can be decreased accordingly to further ensure channel covertness.

[0060] Step two: 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 hidden information, the legitimate receiver only checks the frequency information of the signal and not the amplitude information. The signal of the legitimate channel is demodulated as usual.

[0061] Specifically, NB-IoT's security mechanism protects layers above the physical layer, checking only the signal frequency information and not the amplitude information. This makes NB-IoT vulnerable to covert channel attacks. Meanwhile, legitimate agents can use "covert" channels to enhance communication for legitimate applications.

[0062] Step 3: Design a covert receiver to extract the amplitude information of the received signal and detect and separate the covert information embedded in the signal.

[0063] Step four: Through signal processing, the covert receiver can accurately extract the signal amplitude information, 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 before performing standard demodulation. This specifically includes the following sub-steps:

[0064] 4.1 Extracting subcarrier channels;

[0065] 4.2 Locating the embedding location of hidden information in the subcarrier channel;

[0066] 4.3 Standard demodulation is performed on the hidden information of the target location.

[0067] During modulation, a synchronization header is inserted into each OFDM symbol for synchronization and information extraction. The synchronization header contains information such as subcarrier selection and the location of the hidden information embedding, enabling the covert receiver to correctly extract the information. In the covert receiver, the received signal is first demodulated using standard NB-IoT methods to obtain the raw information. Then, based on the information in the synchronization header, the subcarrier where the hidden information is embedded and its specific embedding location are located, followed by standard OOK amplitude demodulation.

[0068] To perform standard OOK amplitude demodulation on the hidden information of the target location, it is necessary to first extract discrete carrier frequency components from the subcarriers to recover the original subcarriers. Specifically, this involves using the local carrier cos(2πf) c t) and sin(2πf c The received subcarrier s(t) is multiplied by the received subcarrier s(t) to extract the I / Q components. After low-pass filtering to remove high-frequency components, only the I / Q signals are retained. Hidden information is extracted through amplitude analysis of the I / Q signals. Specifically, for the in-phase signal I(t):

[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 hidden information. Specifically, for the quadrature signal Q(t):

[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 orthogonal signal demodulated after embedding the hidden information.

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

[0078] The security of amplitude modulation (AM) covert channels is not absolute and can be eavesdropped on or cracked. Therefore, if they are to be used in practice, a balance between security and reliability must be considered, for example, by using encryption algorithms to encrypt confidential information.

[0079] Accordingly, this application also provides an electronic device, comprising: one or more processors; a memory for storing one or more programs; and, when the one or more programs are executed by the one or more processors, causing the one or more processors to implement the covert channel construction method based on OOK modulation NB-IoT amplitude as described above. Figure 3 The diagram shown is a hardware structure diagram of any device with data processing capabilities for the covert channel construction method based on OOK modulation NB-IoT amplitude implementation provided in this embodiment of the invention, except... Figure 3 In addition to the processor, memory, and network interface shown, any data processing device in the embodiment may also include other hardware depending on the actual function of the data processing device, which will not be described in detail here.

[0080] Accordingly, this application also provides a computer-readable storage medium storing computer instructions, which, when executed by a processor, implement the covert channel construction method based on OOK modulation NB-IoT amplitude as described above. The computer-readable storage medium can be an internal storage unit of any data processing device as described in any of the foregoing embodiments, such as a hard disk or memory. The computer-readable storage medium can also be an external storage device, such as a plug-in hard disk, smart media card (SMC), SD card, flash card, etc., equipped on the device. Furthermore, the computer-readable storage medium can include both internal storage units of any data processing device and external storage devices. The computer-readable storage medium is used to store the computer program and other programs and data required by the data processing device, and can also be used to temporarily store data that has been output or will be output.

[0081] Other embodiments of this application will readily occur to those skilled in the art upon consideration of the specification and practice of the disclosure herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein. The specification and embodiments are to be considered exemplary only.

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

[0083] The above description is merely a preferred embodiment of the present invention. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention using the methods and techniques disclosed above, or modify them into equivalent embodiments with equivalent changes, without departing from the scope of the technical solutions of the present invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall still fall within the protection scope of the technical solutions of the present invention.

Claims

1. A method for constructing a covert channel based on OOK modulation NB-IoT amplitude implementation, characterized in that, The method comprises the following steps: S1, in the transmitter, the secret information is embedded into the legal channel as a secret channel by secretly OOK modulating the signal amplitude of NB-IoT, and the secret information and the legal information are transmitted together, which comprises the following steps: Selecting sub-carrier, modulating secret information to the amplitude of sub-carrier by OOK method, designing secret channel amplitude , , wherein is the fixed modulation amplitude of legal channel, is the OOK modulation amplitude, is the amplitude change ratio, and satisfies , wherein is the signal-to-noise ratio; The physical layer signal of NB-IoT is composed of continuous OFDM symbols, and a synchronization header containing subcarrier selection information and secret information embedding position information is inserted in each OFDM symbol; S2, in the legal receiver, the legal information is obtained by NB-IOT demodulation after receiving the signal; S3, in the secret receiver, the secret information embedded in the signal is detected and separated by extracting the amplitude information of the signal after receiving the signal, which comprises the following steps: the original information is obtained by NB-IOT demodulation of the received signal; the subcarrier position and the secret information embedding position are located according to the information in the synchronization header, and then the standard OOK amplitude demodulation is carried out. 2.The method of claim 1, wherein, The selected subcarriers should meet the following conditions: the number of subcarriers should be 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. 3.The method of claim 1, wherein, The modulation process of the sub-carrier is specifically: two orthogonal signals are adopted and Each symbol corresponds to a point on the I / Q plane, and the legal information data is mapped to four phase points on the complex plane, and the sub-carrier signal is represented as: ； wherein, is an in-phase signal, is a quadrature signal, is a sub-carrier frequency, each symbol lasting a time period to form a QPSK signal; the NB-IoT channel obtains legal information data by judging the constellation phase, only needs the phase condition and the fixed amplitude; the secret information is embedded on the amplitude of the sub-carrier, and the sub-carrier signal after OOK amplitude modulation is represented as: ； wherein, is the designed covert channel amplitude. 4.The method of claim 1, wherein, To avoid bit errors and ensure the reliability of the covert channel, the value of the amplitude variation ratio is set between 1% and 5%.

5. The method of claim 1, wherein the method is characterized in that, The legal receiver is a standard NB-IoT terminal device, and after the legal receiver receives the signal, although the amplitude of the signal carries secret information, the legal receiver only checks the frequency information of the signal and does not check the amplitude information, and the signal of the legal channel is normally demodulated.

6. The method of claim 3, wherein the method is characterized in that, The standard OOK amplitude demodulation in the secret receiver needs to extract the discrete carrier frequency component from the sub-carrier, recover the original sub-carrier, specifically: use the local carrier With And the received sub-carrier Multiply, extract I / Q components, low-pass filter to filter out high-frequency components and only keep I / Q signals, extract secret information by analyzing the amplitude of I / Q signals. 7.The method of claim 1, wherein, Considering the balance between the security and reliability of the secret channel, an encryption algorithm is used to encrypt the secret information.

8. An electronic device comprising a memory and a processor, characterized in that The memory is coupled with the processor; wherein the memory is used for storing program data, and the processor is used for executing the program data to realize the secret channel construction method based on OOK modulation NB-IoT amplitude as claimed in any one of claims 1-7.

9. A computer-readable storage medium having stored thereon a computer program, characterized in that, The program is executed by the processor to realize the secret channel construction method based on OOK modulation NB-IoT amplitude as claimed in any one of claims 1-7.

10. A computer program product comprising computer programs / instructions, characterized in that, The computer program / instruction is executed by the processor to realize the secret channel construction method based on OOK modulation NB-IoT amplitude as claimed in any one of claims 1-7.

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