WiFi backscattering secure communication method and system based on distributed encryption

Abstract

A WiFi backscattering secure communication method based on distributed encryption comprises the following steps: a WiFi access point and a receiving end negotiate a key before communication starts, and generate a key stream through a generator; the method comprises the following steps: after a WiFi access point acquires a key stream, waking up a backscattering label, modulating data on a WiFi data packet through the backscattering label, completing distributed encryption, and sending the WiFi data packet subjected to distributed encryption to a receiving end; after receiving the encrypted WiFi data packet, the receiving end decrypts the encrypted WiFi data packet according to a decryption method specified by a protocol; and the receiving end decodes the decrypted data according to a preset decoding method to obtain decoded label data. Through a distributed encryption mode, the requirements for power consumption and capability of the backscattering tag are reduced, WiFi backscattering secure communication which is low in cost, low in power consumption and compatible with commercial equipment is realized on the premise that hardware of the commercial WiFi equipment does not need to be modified, and security support is provided for application and popularization of the WiFi backscattering communication technology in more fields.

Description

Technical Field

[0001] The present invention relates to the field of wireless communication technologies, and particularly to a WiFi backscatter secure communication method and system based on distributed encryption. Background Art

[0002] Backscatter communication technology has become one of the most promising technologies in the next-generation Internet of Things due to its characteristics such as ultra-low power consumption, miniaturization, and low cost. Backscatter tags achieve communication by reflecting ambient radio frequency signals and modulating data on the ambient radio frequency signals, such as GPS signals, LoRa signals, WiFi signals, etc. Compared with traditional active radio frequency links, backscatter tags do not require high-power consumption and high-cost radio analog components, including crystal resonators, radio frequency oscillators, and decoupling capacitors, etc. Therefore, it does not require a battery and has a low cost, and can be easily integrated into billions of daily objects and deployed on a large scale.

[0003] Among them, WiFi backscatter communication technology has attracted much attention because it can reuse the widely deployed WiFi infrastructure and is widely applied in fields such as smart homes, health monitoring, and smart factories. However, existing WiFi backscatter communication schemes directly transmit information in the wireless channel without any protection, and the broadcast nature and easy accessibility of the wireless channel pose a serious threat to the security of information transmission. For example, in the medical field, by stealing the health data transmitted by medical sensors or implantable medical devices, eavesdroppers can capture the user's vital signs and medical privacy; in addition, the data transmitted by a large number of wearable devices contains the user's location information and daily activity information; in a smart city, the exposure of the information of surveillance cameras using backscatter technology may lead to the infringement of the user's right to privacy. Therefore, it is of great practical significance to study low-cost, low-power consumption, and commercial device-compatible WiFi backscatter secure communication technology.

[0004] Traditional solutions for information transmission security are to encrypt data using complete encryption algorithms. However, this method cannot be applied to backscatter technology: 1. To ensure the security of encrypted data, the system needs to update the key frequently, which requires the backscatter tag to perform downlink demodulation frequently, which will greatly increase the power consumption overhead of the backscatter tag; 2. Traditional encryption algorithms often adopt complex encryption processes to ensure the effectiveness of the algorithm, and this process is difficult to implement on low-cost and low-computation-capability backscatter tags.

[0005] In the field of the Internet of Things, current research on secure communication mainly focuses on: 1) Beamforming: By using beamforming, signals are transmitted directionally to legitimate users, and eavesdroppers in other directions cannot receive the signals, thus achieving secure communication. 2) Physical layer security: Utilizing the reciprocity and randomness of the physical channel, signals are encrypted at the physical layer, including methods such as extracting keys from the physical channel and artificially injecting noise, so that eavesdroppers cannot demodulate the signals while legitimate users can correctly demodulate them. 3) Lightweight encryption algorithms: Simplifying the complex processes of traditional encryption algorithms and researching lightweight encryption algorithms to achieve encryption methods with low computational overhead. However, the above methods are not applicable to WiFi backscatter communication. Firstly, the beamforming method requires devices to be equipped with large antenna arrays or intelligent reflecting surfaces to be pre-deployed in the environment. Among them, large antenna arrays are not suitable for low-power and low-cost backscatter tags; pre-deploying intelligent reflecting surfaces increases the deployment overhead of the infrastructure and limits the large-scale deployment of backscatter tags. Secondly, physical layer security requires devices to have functions such as channel estimation and noise injection, which are also difficult to implement on backscatter tags. Finally, although lightweight encryption algorithms achieve data encryption in a low-overhead manner, this method is not compatible with standard communication protocols and commercial WiFi devices and is currently mainly used in RFID systems with strong self-defined functions and is not applicable to WiFi backscatter communication.

[0006] At the same time, since commercial WiFi devices perform a series of transformation operations on the data to be sent: scrambling, forward error correction coding, interleaving, and perform corresponding reverse operations on the receiving device. None of the previous WiFi backscatter communication schemes can decode backscatter tag data at the single OFDM symbol level while ensuring compatibility with the WiFi protocol and devices. The solutions adopted by these schemes are to decode tag data before the receiving device performs reverse operations or after performing the deinterleaving operation, which are not compatible with the WiFi protocol and cannot be implemented on commercial WiFi devices. Therefore, there is an urgent need for a WiFi backscatter secure communication method and system based on distributed encryption to achieve low-cost, low-power, and commercial device-compatible WiFi backscatter secure communication without modifying the hardware of commercial WiFi devices, providing security support for the application and promotion of WiFi backscatter communication technology in more fields. Summary of the Invention

[0007] In view of the above problems, the present invention is proposed to provide a WiFi backscatter secure communication method and system based on distributed encryption that overcomes the above problems or at least partially solves the above problems.

[0008] To solve the above technical problems, the embodiments of the present application disclose the following technical solutions:

[0009] In a first aspect, an embodiment of the present invention discloses a WiFi backscatter secure communication method based on distributed encryption, including:

[0010] S100. The WiFi access point and the receiving end negotiate a key before the communication starts, and obtain a key stream through a generator;

[0011] S200. After obtaining the key stream, the WiFi access point wakes up the backscatter tag, modulates data on the WiFi data packet through the backscatter tag, completes distributed encryption, and sends the distributed encrypted WiFi data packet to the receiving end;

[0012] S300. After receiving the encrypted WiFi data packet, the receiving end decrypts it according to the decryption method specified in the protocol;

[0013] S400. The receiving end decodes the decrypted data according to a preset decoding method to obtain the decoded tag data.

[0014] Further, in S200, after obtaining the key stream, the WiFi access point wakes up the backscatter tag, and modulates data on the WiFi data packet through the backscatter tag. The specific method includes: The WiFi access point generates a key stream x(n) of the same length as the data through a rolling key generator according to the encryption algorithms WEP or WAP specified in the WiFi protocol. The WiFi access point performs scrambling, forward error correction coding, and interleaving operations on the data in sequence, and sends it to the backscatter tag in the form of a radio frequency signal.

[0015] Further, the backscatter tag performs phase modulation on the received signal, and the backscattered signal is expressed as:

[0016] H1*I{F{S[x(n)]}}*e jθ

[0017] where H1 is the wireless channel from the AP to the backscatter tag, and I, F, S respectively correspond to the interleaving, forward error correction coding, and scrambling operations at the AP, and e jθ is the phase modulation performed by the backscatter tag; when the backscatter tag sends data 1, θ = π; when the backscatter tag sends data 0, θ = 0.

[0018] Further, the signal received at the receiving end is:

[0019] H1*H4*I{F{S[x(n)]}}*e jθ

[0020] Among them, H4 is the wireless channel from the backscatter tag to the receiving end. After channel equalization, the wireless channels H1 and H4 are eliminated; the signal received by the receiving end is regarded as the result of XOR operation between the data of the backscatter tag and the key stream; the receiving device processes the signal I{F{S[x(n)]}}*e jθ Map it to a point on the constellation diagram to obtain the binary data r x (n): Among them, d(n) is the data sent by the tag.

[0021] Furthermore, the receiving end successively performs deinterleaving, Viterbi decoding, and descrambling operations on the binary data r x (n), which are respectively represented as I -1 , F -1 , S -1 ; The specific methods include:

[0022] Utilize the characteristic that the deinterleaving operation satisfies the distributive law for the XOR operation. The data after deinterleaving is:

[0023]

[0024] The data after Viterbi decoding is:

[0025]

[0026] Among them, r x (n) is the binary data, x(n) is the pre-shared key stream, d(n) is the data sent by the tag, and d'(n) is the data satisfying the above equation.

[0027] Furthermore, in S300, after the receiving end receives the encrypted WiFi data packet, it decrypts it according to the decryption method specified by the protocol. The specific method includes: performing an XOR operation on the received data and the pre-shared key stream x(n) to obtain the data finally transmitted to the MAC layer, where the received data is binary data The XOR operation is expressed as:

[0028]

[0029] is the received binary data, and x(n) is the pre-shared key stream.

[0030] Furthermore, in S400, the receiving end decodes the decrypted data according to the preset decoding method to obtain the decoded tag data. The specific method includes: successively performing forward error correction coding and interleaving operations on the data at the MAC layer to obtain the data I{F{F -1 {I -1[d'(n)]}}} = d'(n), where the obtained d'(n) is not the same as the data d(n) sent by the tag. The frequencies of d'(n) being bit 0 and bit 1 within a symbol are counted, and the bit with the larger frequency is taken as the finally decoded tag data.

[0031] Further, when there are multiple eavesdroppers collaborating during the process of the backscatter tag modulating data on the WiFi data packet, by reusing the key stream x(t) shared by the transceiver, the long training sequence LTS of the WiFi data packet is encrypted to obtain the encrypted long training sequence LTS':

[0032]

[0033] So that only legitimate users can correctly perform channel estimation based on LTS', thus ensuring communication security in the case of multiple collaborating eavesdroppers.

[0034] Further, when the pilot information is leaked during the process of the backscatter tag modulating data on the WiFi data packet, by reusing the key stream x(t) shared by the transceiver, the polarization control sequence P of the WiFi data packet i is encrypted to obtain p i ':

[0035]

[0036] So that only legitimate users can correctly obtain the pilot signal p i ', thus avoiding the problem of information leakage of the pilot signal.

[0037] In a second aspect, an embodiment of the present invention discloses a WiFi backscatter secure communication system based on distributed encryption, including:

[0038] A key stream generation unit, configured to negotiate a key between the WiFi access point and the receiving end before communication starts, and generate a key stream through a generator;

[0039] A data packet distributed encryption unit, configured to, after the WiFi access point obtains the key stream, wake up the backscatter tag, modulate data on the WiFi data packet through the backscatter tag to complete distributed encryption, and send the distributed encrypted WiFi data packet to the receiving end;

[0040] A data packet decryption unit, configured to, after the receiving end receives the encrypted WiFi data packet, decrypt it according to the decryption method specified by the protocol;

[0041] A data packet decoding unit, configured to decode the decrypted data by the receiving end according to a preset decoding method to obtain the decoded tag data.

[0042] The beneficial effects of the above technical solutions provided by the embodiments of the present invention at least include:

[0043] The present invention discloses a WiFi backscatter security communication method based on distributed encryption, including:

[0044] Before the communication starts, the WiFi access point and the receiving end negotiate a key, and generate a key stream through a generator; after obtaining the key stream, the WiFi access point wakes up the backscatter tag, modulates data on the WiFi data packet through the backscatter tag to complete distributed encryption, and sends the distributedly encrypted WiFi data packet to the receiving end; after receiving the encrypted WiFi data packet, the receiving end decrypts it according to the decryption method specified by the protocol; the receiving end decodes the decrypted data according to a preset decoding method to obtain the decoded tag data.

[0045] Through the method of distributed encryption, the present invention reduces the requirements for the power consumption and capabilities of the backscatter tag, and realizes low-cost, low-power, and WiFi backscatter security communication compatible with commercial devices; in view of the fact that existing backscatter communications cannot decode backscatter signals at the single OFDM symbol level in a manner compatible with the WiFi protocol, a tag data decoding scheme compatible with the WiFi protocol and commercial devices is proposed; and effective solutions are proposed for the situation of multiple eavesdroppers and the information leakage problem of pilot signals in backscatter communication, providing security support for the application and popularization of WiFi backscatter communication technology in more fields.

[0046] The technical solutions of the present invention will be further described in detail below through the drawings and embodiments. Description of the Drawings

[0047] The drawings are used to provide a further understanding of the present invention, and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention, and do not constitute a limitation to the present invention. In the drawings:

[0048] Figure 1 It is a flowchart of a WiFi backscatter security communication method based on distributed encryption in Embodiment 1 of the present invention;

[0049] Figure 2 It is a logical schematic diagram of a WiFi backscatter security communication method based on distributed encryption in Embodiment 1 of the present invention;

[0050] Figure 3 It is a logical schematic diagram of distributed encryption of tag data in Embodiment 1 of the present invention;

[0051] Figure 4 It is a phase modulation schematic diagram of the backscatter tag under binary modulation in Embodiment 1 of the present invention;

[0052] Figure 5 This is the phase modulation schematic diagram of the backscatter tag under QAM modulation in Embodiment 1 of the present invention;

[0053] Figure 6 This is the logic schematic diagram of the decoding scheme for the data of the backscatter tag in Embodiment 1 of the present invention;

[0054] Figure 7 This is the schematic diagram of the communication model for the case of multiple eavesdroppers collaborating in Embodiment 1 of the present invention;

[0055] Figure 8 This is the schematic diagram of the solution for the case of multiple eavesdroppers and the solution for the information leakage problem of the pilot signal in Embodiment 1 of the present invention. Detailed implementation manners

[0056] Hereinafter, exemplary embodiments of the present disclosure will be described in more detail with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided so that the present disclosure can be more thoroughly understood and the scope of the present disclosure can be fully conveyed to those skilled in the art.

[0057] In order to solve the problems existing in the prior art, an embodiment of the present invention provides a WiFi backscatter secure communication method and system based on distributed encryption.

[0058] Embodiment 1

[0059] The present invention discloses a WiFi backscatter secure communication method based on distributed encryption, as Figure 1 , including:

[0060] S100. Before the communication starts, the WiFi access point and the receiving end negotiate a key, and a key stream is generated through a generator; specifically, as Figure 2 , in this embodiment, the WiFi access point is the transmitting end, and the mobile phone device is the receiving end. At the beginning of the communication, the transceiver negotiates the key according to the WiFi standard protocol. Since both the transceiver ends are powerful commercial WiFi devices, after the transceiver ends negotiate the key according to the WiFi protocol, the transceiver ends respectively save the key for subsequent backscatter communication.

[0061] S200. After the WiFi access point obtains the key stream, it wakes up the backscatter tag, modulates data on the WiFi data packet through the backscatter tag, completes distributed encryption, and sends the distributed encrypted WiFi data packet to the receiving end;

[0062] Among them, the step S200 disclosed in this embodiment is used to solve two problems of traditional encryption algorithms applied to backscatter communication: 1. In order to ensure the security of encrypted data, the system needs to frequently update the key, requiring the backscatter tag to frequently demodulate the downlink, which will greatly increase the power consumption of the backscatter tag; 2. In order to ensure the effectiveness of the algorithm, traditional encryption algorithms often adopt a complex encryption process, which is difficult to implement on low-cost, low-computing-power backscatter tags. Specifically, Figure 3 As shown in the figure, through distributed encryption, the computationally expensive key stream generation process and the key update process requiring frequent demodulation are transferred to powerful commercial equipment WiFi APs. The backscatter tag only needs to modulate the data on the RF signal. Finally, the signal modulated by the backscatter tag is the encrypted data packet using the standard encryption algorithm.

[0063] Specifically, the security protocols widely used in WiFi devices are WEP and its upgraded version WAP, the core of which is stream encryption. The essence of stream encryption is to perform an XOR operation on the plaintext data and the key stream. Since the eavesdropper does not know the key stream, he cannot decrypt the information, while the legitimate user has the same key stream as the transmitter and can therefore correctly decrypt the plaintext. Distributed encryption takes advantage of this feature of stream encryption to transfer the key stream and plaintext data to the WiFi AP and backscatter tag respectively, and finally completes the encryption operation directly in the air through the RF domain, thereby greatly reducing the demand for backscatter tag computing resources and power consumption. In addition, if Figure 4 As shown in the figure, when the backscatter tag is modulated by 1, the phase is shifted by π, otherwise the phase is not shifted. When the OFDM symbol sent by the AP is BPSK modulated, this process can be regarded as performing an XOR operation on the RF signal and the backscatter signal. At the same time, when the OFDM symbol is high-order QAM modulation, such as Figure 5 As shown in Figure 1, this process can be considered as performing an XOR operation on the first digit of the original I and Q signals with the backscatter signal. This allows for in-flight encryption of tag data streams and secure WiFi backscatter communication based on distributed encryption.

[0064] In S200 of this embodiment, after obtaining the key stream, the WiFi access point wakes up the backscatter tag and modulates data on the WiFi data packet through the backscatter tag. The specific method includes: the WiFi access point uses the encryption algorithm WEP or WAP specified in the WiFi protocol to generate a key stream x(n) of the same length as the data through a rolling key generator. The WiFi access point sequentially performs scrambling, forward error correction encoding, and interleaving operations on the data, and sends the data to the backscatter tag in the form of a radio frequency signal.

[0065] In some preferred embodiments, the backscatter tag performs phase modulation on the received signal, and the backscattered signal is expressed as:

[0066] H1*I{F{S[x(n)]}}*e jθ

[0067] where H1 is the wireless channel from the AP to the backscatter tag, and I, F, and S respectively correspond to the interleaving, forward error correction coding, and scrambling operations at the AP, and e jθ is the phase modulation performed by the backscatter tag; when the backscatter tag sends data 1, θ = π; when the backscatter tag sends data 0, θ = 0.

[0068] In some preferred embodiments, the signal received at the receiving end is:

[0069] H1*H4*I{F{S[x(n)]}}*e jθ

[0070] where H4 is the wireless channel from the backscatter tag to the receiving end. After channel equalization, the wireless channels H1 and H4 are eliminated; the signal received at the receiving end is regarded as the result of performing an exclusive OR operation on the data of the backscatter tag and the key stream; the receiving device maps the signal I{F{S[x(n)]}}*e jθ to a point on the constellation diagram to obtain the binary data r x (n): where d(n) is the data sent by the tag.

[0071] The receiving end sequentially performs deinterleaving, Viterbi decoding, and descrambling operations on the binary data r x (n), which are respectively denoted as I -1 , F -1 , S -1 ; The specific methods include:

[0072] Utilizing the characteristic that the deinterleaving operation satisfies the distributive law for the exclusive OR operation, the data after deinterleaving is:

[0073]

[0074] The data after Viterbi decoding is:

[0075]

[0076] where r x(n) is binary data, x(n) is a pre-shared key stream, d(n) is the data sent by the tag, and d'(n) is the data that satisfies the above equation. Specifically, although forward error correction coding satisfies the distributive law of exclusive OR operation F(A + B) = F(A) + F(B), only when A and B are both sequences encoded by forward error correction coding, the corresponding reverse operation - Viterbi decoding satisfies F -1 (A + B) = F -1 (A) + F -1 (B). However, the backscatter tag only modulates the phase once for an OFDM symbol, and the corresponding binary sequence remains unchanged within a symbol, that is, all AP data within a symbol is XORed with the same tag data. In this case, Viterbi decoding approximately satisfies the distributive law at a certain bit error rate, denoted by d'(n).

[0077] S300. After the receiving end receives the encrypted WiFi data packet, it decrypts it according to the decryption method specified by the protocol; since stream encryption of WEP or WAP is enabled, the receiving device will perform the decryption operation before transmitting the data to the MAC layer. In S300 of this embodiment, after the receiving end receives the encrypted WiFi data packet, it decrypts it according to the decryption method specified by the protocol. The specific method includes: performing an exclusive OR operation on the received data and the pre-shared key stream x(n) to obtain the data finally transmitted to the MAC layer, where the received data is binary data The exclusive OR operation is expressed as:

[0078]

[0079] is the received binary data, and x(n) is the pre-shared key stream.

[0080] S400. The receiving end decodes the decrypted data according to a preset decoding method to obtain the decoded tag data. Specifically, such as Figure 6As shown in the figure, for WiFi commercial devices, the physical layer includes a series of data transformation operations: scrambling, forward error correction coding, and interleaving operations of the transmitting device, as well as the corresponding reverse operations of the receiving device. The backscattered tag data is XORed with the signal after the transformation operations of the transmitting device in the air and will undergo a series of reverse operations at the receiving device. Traditional backscatter communication schemes cannot effectively decode the tag data in this case. To address this problem, the present invention proposes that after receiving the data at the MAC layer of the receiving device, by utilizing the characteristics that the tag data remains unchanged within a single OFDM symbol and the data transformation operations, forward error correction coding and interleaving operations are performed on the received MAC layer data again, and the bit with the highest frequency of occurrence within an OFDM symbol is taken as the finally decoded tag data. Through the above decoding scheme, while being compatible with the WiFi protocol and devices, the backscattered tag data can be effectively decoded at the single OFDM symbol level.

[0081] In S400 of this embodiment, the receiving end decodes the decrypted data according to a preset decoding method to obtain the decoded tag data. The specific method includes: sequentially performing forward error correction coding and interleaving operations on the data of the MAC layer to obtain data I{F{F -1 {I -1 [d'(n)]}}} = d'(n), where the obtained d'(n) is not the same as the data d(n) sent by the tag. The frequencies of d'(n) being bit 0 and 1 within a symbol are counted, and the bit with the higher frequency is taken as the finally decoded tag data.

[0082] In some preferred embodiments, as Figure 7 shown, when there are multiple eavesdroppers collaborating during the process of the backscattered tag modulating data on the WiFi data packet, the signals received by eavesdropper 1 and eavesdropper 2 are H3*F[x(t)] and H1*H2*F[x(t)]*e jθ , where H3 is the wireless channel from eavesdropper 2 to the AP, H1 is the wireless channel from the AP to the backscattered tag, and H2 is the wireless channel from eavesdropper 2 to the backscattered tag. When the eavesdropper can correctly estimate the channel and perform channel equalization, the eavesdropper can steal the data of the backscattered tag by comparing the downlink data from the AP to the backscattered tag and the uplink data from the backscattered tag to the receiving end:

[0083]

[0084] However, there is a key prerequisite for this collaboration method: eavesdroppers can correctly perform channel estimation on data packets and eliminate the influence of the wireless channel, so as to ensure that the difference between the uplink and downlink signals is completely caused by the backscatter tag. When multiple eavesdroppers collaborate during the process of the backscatter tag modulating data on the WiFi data packet, by reusing the key stream x(t) shared by the transceiver, the long training sequence LTS of the WiFi data packet is encrypted to obtain the encrypted long training sequence LTS':

[0085]

[0086] So that only legitimate users can correctly perform channel estimation based on LTS', thus ensuring communication security in the case of multiple collaborating eavesdroppers.

[0087] In some preferred embodiments, as Figure 8 shown, the symbols of the WiFi data packet are composed of 64 subcarriers, among which 4 subcarriers are used as pilot signals, denoted as p i , i = 1, 2, 3, 4. When the backscatter tag performs phase modulation, not only the data subcarriers are modulated, but also the pilot signals are modulated, so that eavesdroppers can steal the data of the backscatter tag according to the information leaked by the pilot signals:

[0088]

[0089] To address this issue, when the pilot information leaks during the process of the backscatter tag modulating data on the WiFi data packet, by reusing the key stream x(t) shared by the transceiver, the polarization control sequence P i of the WiFi data packet is encrypted to obtain p i ':

[0090]

[0091] So that only legitimate users can correctly obtain the pilot signal p i ', thus avoiding the problem of pilot signal information leakage.

[0092] This embodiment discloses a WiFi backscatter secure communication method based on distributed encryption, including: the WiFi access point and the receiving end negotiate a key before the communication starts, and generate a key stream through a generator; after the WiFi access point obtains the key stream, it wakes up the backscatter tag, modulates data on the WiFi data packet through the backscatter tag, completes distributed encryption, and sends the distributed encrypted WiFi data packet to the receiving end; after receiving the encrypted WiFi data packet, the receiving end decrypts it according to the decryption method specified by the protocol; the receiving end decodes the decrypted data according to a preset decoding method to obtain the decoded tag data. Through the method of distributed encryption, this embodiment reduces the requirements for the power consumption and capabilities of the backscatter tag, and realizes low-cost, low-power, and WiFi backscatter secure communication compatible with commercial devices; aiming at the problem that existing backscatter communications cannot decode backscatter signals at the single OFDM symbol level in a manner compatible with the WiFi protocol, a tag data decoding scheme compatible with the WiFi protocol and commercial devices is proposed; and an effective solution is proposed for the situation of multiple eavesdroppers and the information leakage problem of pilot signals in backscatter communication, providing security support for the application and promotion of WiFi backscatter communication technology in more fields.

[0093] Embodiment 2

[0094] Based on the same inventive concept, this embodiment of the present disclosure also provides a WiFi backscatter secure communication system based on distributed encryption, including:

[0095] A key stream generation unit, configured to negotiate a key between the WiFi access point and the receiving end before the communication starts, and generate a key stream through a generator;

[0096] A data packet distributed encryption unit, configured to wake up the backscatter tag after the WiFi access point obtains the key stream, modulate data on the WiFi data packet through the backscatter tag, complete distributed encryption, and send the distributed encrypted WiFi data packet to the receiving end;

[0097] A data packet decryption unit, configured to decrypt the encrypted WiFi data packet received by the receiving end according to the decryption method specified by the protocol;

[0098] A data packet decoding unit, configured to decode the decrypted data by the receiving end according to a preset decoding method to obtain the decoded tag data.

[0099] Among them, the specific working methods of the key stream generation unit, the data packet distributed encryption unit, the data packet decryption unit, and the data packet decoding unit have been described in detail in Embodiment 1, and will not be repeated in this embodiment.

[0100] It should be understood that the specific order or hierarchy of steps in the disclosed process is an example of an exemplary method. Based on design preferences, it should be understood that the specific order or hierarchy of steps in the process can be rearranged without departing from the scope of the present disclosure. The appended method claims present the elements of the various steps in an exemplary order and are not intended to be limited to the specific order or hierarchy recited.

[0101] In the above detailed description, various features are combined in a single embodiment to simplify the present disclosure. This method of disclosure should not be interpreted as reflecting an intention that the embodiments of the claimed subject matter require more features than are expressly recited in each claim. Rather, as reflected in the appended claims, the invention lies in less than all of the features of a single disclosed embodiment. Accordingly, the appended claims are hereby expressly incorporated into the detailed description, with each claim standing on its own as a separate preferred embodiment of the invention.

[0102] Those skilled in the art should also understand that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the embodiments herein can be implemented as electronic hardware, computer software, or combinations thereof. To clearly illustrate the interchangeability of hardware and software, the various illustrative components, blocks, modules, circuits, and steps have been generally described in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as departing from the scope of the present disclosure.

[0103] The steps of a method or algorithm described in connection with the embodiments herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination thereof. The software module may be located in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium well known in the art. An exemplary storage medium is coupled to the processor such that the processor can read information from, and write information to, the storage medium. Of course, the storage medium may also be integral to the processor. The processor and the storage medium may be located in an ASIC. The ASIC may be located in a user terminal. Of course, the processor and the storage medium may also exist as discrete components in a user terminal.

[0104] For software implementation, the techniques described in this application can be implemented by modules (e.g., procedures, functions, etc.) that perform the functions described in this application. These software codes can be stored in a memory unit and executed by a processor. The memory unit can be implemented within the processor or outside the processor. In the latter case, it is communicatively coupled to the processor via various means, which are well known in the art.

[0105] The above description includes examples of one or more embodiments. Of course, it is not possible to describe all possible combinations of components or methods for the purpose of describing the above embodiments, but those of ordinary skill in the art should recognize that the various embodiments can be further combined and arranged. Therefore, the embodiments described herein are intended to cover all such changes, modifications, and variations that fall within the scope of the appended claims. In addition, with respect to the term "comprising" used in the specification or claims, this term is covered in a manner similar to the term "including," as interpreted when "including" is used as a transitional word in a claim. In addition, any use of the term "or" in the specification or claims of a patent is to mean "non-exclusive or."

Claims

1. A WiFi backscatter secure communication method based on distributed encryption, characterized in that, Including: S100. The WiFi access point and the receiver negotiate a key before communication starts, and generate a key stream through a generator. S200. After the WiFi access point obtains the key stream, it wakes up the backscatter tag, modulates data on the WiFi data packet through the backscatter tag, completes distributed encryption, and sends the distributed encrypted WiFi data packet to the receiver. S300. After the receiver receives the encrypted WiFi data packet, it decrypts it according to the decryption method specified by the protocol. S400. The receiver decodes the decrypted data according to a preset decoding method to obtain the decoded tag data.

2. The method for secure WiFi backscatter communication based on distributed encryption according to claim 1, wherein, In S200, after the WiFi access point obtains the key stream, it wakes up the backscatter tag, and modulates data on the WiFi data packet through the backscatter tag. The specific method includes: The WiFi access point generates a key stream x(n) of the same length as the data through a rolling key generator according to the encryption algorithms WEP or WAP specified by the WiFi protocol. The WiFi access point performs scrambling, forward error correction coding, and interleaving operations on the data in sequence, and sends it to the backscatter tag in the form of a radio frequency signal.

3. The method for secure communication of WiFi backscattering based on distributed encryption according to claim 2, wherein, The backscatter tag performs phase modulation on the received signal, and the backscattered signal is expressed as: H1*I{F{S[x(n)]}}*e jθ Among them, H1 is the wireless channel from the AP to the backscatter tag, and I, F, and S respectively correspond to the interleaving, forward error correction coding, and scrambling operations at the AP, and e jθ is the phase modulation performed by the backscatter tag; when the backscatter tag sends data 1, θ = π; when the backscatter tag sends data 0, θ = 0.

4. The WiFi backscatter security communication method based on distributed encryption according to claim 3, characterized in that The signal received at the receiver is: H1*H4*I{F{S[x(n)]}}*e jθ Among them, H4 is the wireless channel from the backscatter tag to the receiver. After channel equalization, the wireless channels H1 and H4 are eliminated; the signal received by the receiver is regarded as the result of performing an exclusive OR operation on the data of the backscatter tag and the key stream; the receiving device processes the signal I{F{S[x(n)]}}*e jθ Map it to the points on the constellation diagram to obtain the binary data r x (n): where d(n) is the data sent by the tag.

5. The method for secure communication of WiFi backscattering based on distributed encryption according to claim 4, characterized in that, The receiving end successively performs deinterleaving, Viterbi decoding, and descrambling operations on the binary data r x (n), which are respectively represented as I -1 , F -1 , S -1 ; The specific method includes: Using the characteristic that the deinterleaving operation satisfies the distributive law for the exclusive OR operation, the data after deinterleaving is: The data after Viterbi decoding is: where r x (n) is binary data, x(n) is a pre-shared key stream, d(n) is the data sent by the tag, and d'(n) is the data that satisfies the above equation.

6. The method for secure communication of WiFi backscattering based on distributed encryption according to claim 5, wherein, In S300, after the receiving end receives the encrypted WiFi data packet, it decrypts it according to the decryption method specified in the protocol. The specific method includes: performing an exclusive OR operation on the received data and the pre-shared key stream x(n) to obtain the data finally transmitted to the MAC layer, where the received data is binary data The exclusive OR operation is expressed as: Let \(y(n)\) be the received binary data and \(x(n)\) be the pre-shared key stream.

7. The method for secure communication of WiFi backscattering based on distributed encryption according to claim 6, characterized in that, In the S400, the receiving end decodes the decrypted data according to a preset decoding method to obtain the decoded tag data. The specific method includes: performing forward error correction coding and interleaving operations on the data at the MAC layer in sequence to obtain data I{F{F -1 {I -1 [d'(n)]}}} = d'(n), where the obtained d'(n) is not the same as the data d(n) sent by the tag. The frequencies of d'(n) being bit 0 and bit 1 within a symbol are counted, and the bit with the larger frequency is taken as the finally decoded tag data.

8. The method for secure communication of WiFi backscattering based on distributed encryption according to claim 1, wherein, When multiple eavesdroppers collaborate during the process of the backscatter tag modulating data on the WiFi data packet, by reusing the key stream x(t) shared by the transceiver, the long training sequence LTS of the WiFi data packet is encrypted to obtain the encrypted long training sequence LTS': So that only legitimate users can correctly perform channel estimation based on LTS', thus ensuring communication security in the case of multiple collaborating eavesdroppers.

9. The method for secure communication of WiFi backscattering based on distributed encryption according to claim 1, wherein When the pilot information leaks during the process of modulating data on the WiFi data packet by the backscatter tag, the polarization control sequence P of the WiFi data packet is encrypted by reusing the key stream x(t) shared by the transceiver to obtain p i '. i ' Only legal users can correctly obtain the pilot signal p i ', thus avoiding the problem of information leakage of the pilot signal.

10. A WiFi backscatter security communication system based on distributed encryption, adopting the security communication method described in any one of the above claims 1-9, characterized in that, Including: A key stream generation unit, which is used for the WiFi access point and the receiver to negotiate a key before communication starts, and generate a key stream through a generator. A data packet distributed encryption unit, which is used for the WiFi access point to wake up the backscatter tag after obtaining the key stream, modulate data on the WiFi data packet through the backscatter tag, complete distributed encryption, and send the distributed encrypted WiFi data packet to the receiver. A data packet decryption unit, which is used for the receiver to decrypt the received encrypted WiFi data packet according to the decryption method specified by the protocol. A data packet decoding unit, which is used for the receiver to decode the decrypted data according to a preset decoding method to obtain the decoded tag data.

Images