Group key generation and management method based on position information in backscatter communication

Abstract

The invention discloses a group key generation and management method based on position information in backscatter communication, the generation method is applied to any backscatter device Ai in a backscatter communication system, and the generation method comprises the following steps: estimating coordinate information of each other backscatter device Aj according to a received radio frequency signal and a reflection signal, wherein the radio frequency signal is a signal emitted by a radio frequency source, the reflection signal is a radio frequency signal reflected by backscattering equipment, i and j belong to {1, 2,..., N}, i is not equal to j, and N is the total number of backscattering equipment in the system; extracting shared information from the coordinate information; and sequentially carrying out quantization, information negotiation and privacy amplification operation on the shared information to obtain a group key of the system. The group key generated by the method is good in performance and high in generation efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of backscatter communications, and in particular relates to a group key generation and management method based on position information in backscatter communications. Background Art

[0002] In today's rapidly developing digital age, security issues in wireless communications are becoming increasingly prominent. Secure key generation plays a crucial and irreplaceable role in ensuring secure communication between different backscatter devices. Encrypting communication content with secure keys creates a solid security barrier for communication between backscatter devices within a backscatter communication system, effectively ensuring the confidentiality and security of the communication process, effectively preventing information theft or tampering during transmission, and maintaining the integrity and reliability of communication. Currently, most academic research focuses on key generation between two legitimate backscatter devices in a backscatter communication system. In this area, researchers widely utilize lightweight cryptography and physical layer mechanisms to achieve secure key generation and exchange. While these studies address the security issues of two-to-one communication to some extent, practical application scenarios are often more complex. In many cases, generating a shared key is essential for securely exchanging confidential information between multiple legitimate backscatter devices. This key is used to encrypt and decrypt messages between them. Using a group key to encrypt communication data effectively ensures the security and safety of communications between backscatter devices within a backscatter communication group, creating a strong defense for information transmission.

[0003] While conventional technologies have made some progress in backscatter communications, they still suffer from significant shortcomings and limitations. Specifically, when generating group keys, conventional technologies cannot simultaneously meet the requirements of high key consistency, high key generation efficiency, strong robustness, and low complexity. Consequently, conventional methods cannot be deployed on resource-constrained backscatter devices, nor can they provide acceptable key generation efficiency. Summary of the Invention

[0004] The embodiment of the present invention provides a group key generation and management method based on location information in backscatter communication, which can solve the problems of poor performance and low efficiency of traditional key generation technology.

[0005] In a first aspect, an embodiment of the present invention provides a method for generating a group key based on location information in backscatter communication, wherein the method is applied to any backscatter device A in a backscatter communication system. i Above, the method includes:

[0006] Based on the received RF signal and the reflected signal, estimate the backscattering power of each other device A. j, wherein the radio frequency signal is the signal emitted by the radio frequency source, the reflected signal is the radio frequency signal reflected by the backscattering device, i, j∈{1,2,...,N}, and i≠j, N is the total number of backscattering devices in the system;

[0007] extracting shared information from the location information;

[0008] The shared information is sequentially subjected to quantization, information negotiation, and privacy amplification operations to obtain a group key of the system.

[0009] In a second aspect, an embodiment of the present invention provides a group key management method based on location information, the method being applied to a backscatter communication system, the system comprising a radio frequency source and a plurality of backscatter devices, the method comprising:

[0010] Initializing the radio frequency source and the backscattering device;

[0011] The backscatter device generates a group key according to the group key generation method according to the first aspect;

[0012] If any backscatter device leaves the system, or any backscatter device joins the system, the radio frequency source and the backscatter device update the group key to obtain an updated group key.

[0013] Compared with the prior art, the embodiments of the present invention have the following beneficial effects: the present invention calculates the location information of the device based on the signal strength and arrival angle, and uses the location information of all legitimate backscatter devices as shared information for key generation. There is no need to transmit other special detection signals for complex channel estimation, which can greatly reduce the computing cost of the device and the communication cost between devices, reduce the complexity of key generation, and improve the efficiency and robustness of key generation. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 A schematic structural diagram of a backscatter communication system provided in an embodiment of the present invention;

[0015] Figure 2 A flowchart of a method for generating a group key based on location information in backscatter communication provided by an embodiment of the present invention;

[0016] Figure 3 A schematic diagram of a scenario for extracting shared information provided by an embodiment of the present invention;

[0017] Figure 4 A schematic diagram of a scenario for generating a group key based on shared information provided by an embodiment of the present invention;

[0018] Figure 5A schematic diagram of a scenario for generating a private weight vector in a static environment provided by an embodiment of the present invention;

[0019] Figure 6 A flow chart of a group key management method based on location information in backscatter communication provided by an embodiment of the present invention;

[0020] Figure 7 A schematic diagram of a scenario for managing group keys provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0021] In the following description, specific details such as particular system structures and techniques are provided for purposes of illustration, not limitation, to facilitate a thorough understanding of the embodiments of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted so as not to obscure the description of the present invention with unnecessary detail.

[0022] It should be understood that when used in the present specification and the appended claims, the term "comprising" indicates the presence of described features, integers, steps, operations, elements and / or components, but does not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof.

[0023] It will also be understood that the term "and / or" used in the present description and appended claims refers to and includes any and all possible combinations of one or more of the associated listed items.

[0024] As used in the present specification and the appended claims, the term "if" may be interpreted as "when" or "upon" or "in response to determining" or "in response to detecting," depending on the context. Similarly, the phrase "if it is determined" or "if [described condition or event] is detected" may be interpreted as meaning "upon determination" or "in response to determining" or "upon detection of [described condition or event]" or "in response to detecting [described condition or event]," depending on the context.

[0025] In addition, in the description of the present specification and the appended claims, the terms "first", "second", "third", etc. are only used to distinguish the descriptions and cannot be understood as indicating or implying relative importance.

[0026] References to "one embodiment" or "some embodiments" in the present specification mean that a particular feature, structure, or characteristic described in conjunction with that embodiment is included in one or more embodiments of the present invention. Thus, phrases such as "in one embodiment," "in some embodiments," "in other embodiments," and "in yet other embodiments" appearing in various places in this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "including," "comprising," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized.

[0027] The present invention will be further described in detail below with reference to specific examples, but the embodiments of the present invention are not limited thereto.

[0028] Example 1

[0029] Figure 1 A schematic structural diagram of a backscatter communication system provided by an embodiment of the present invention.

[0030] In one possible implementation, see Figure 1 , a backscatter communication system can include two legal entities: a radio frequency source (such as a WiFi access point) and a backscatter device. The radio frequency source can transmit radio frequency signals to all backscatter devices within the coverage area in a time-division manner. The backscatter device can have two working modes, one is a listening mode and the other is a backscatter mode. In the listening mode, the backscatter device can receive signals (radio frequency signals or composite signals composed of radio frequency signals and reflected signals from other backscatter devices); in the backscatter mode, it can receive signals and change the phase or amplitude of the signal after reflecting the radio frequency signal.

[0031] In one example, a backscatter device may include: a modulator, an information receiver, a communication module, a backscatter module, a computing module, an energy harvester, a battery, and other modules (such as sensors).

[0032] For example, the backscatter device may be stationary or mobile.

[0033] In one example, a backscatter device may measure the strength and angle of arrival of a received signal.

[0034] For example, the strength of the received signal may be represented by the average power of the received signal over a period of time.

[0035] In one possible implementation, see Figure 1 ,There may also be illegal entities intervening in the backscatter ,communication system, such as the passive eavesdropper Eve and the active attacker Mallory.

[0036] For example, the passive eavesdropper Eve can intercept all communications between the backscatter device and the RF source in the system, receive the RF signal transmitted by the RF source, and estimate the channel information based on the intercepted signal, attempting to infer the information of the generated group key based on the channel information.

[0037] For example, the active attacker Mallory can intentionally launch two active attacks: a channel manipulation attack and a signal manipulation attack. A channel manipulation attack, also known as a "man-in-the-middle" attack, manipulates the channel between the transmitter and receiver by strategically changing the position of an intermediary object (e.g., the passive eavesdropper Eve), thereby changing the channel gain. In a signal manipulation attack, the active attacker Mallory injects a manipulated signal into legitimate backscatter devices. Each legitimate backscatter device uses the injected signal as part of the shared information used to generate the key. This allows Mallory to manipulate a portion of the valid key bits.

[0038] In one example, since backscatter communication systems are often deployed in crowded environments (such as warehouses), there is usually no direct communication channel between the signal transmitter and the signal receiver due to the deep shadow effect. The main transmission channel is often blocked by obstacles. Therefore, the complex interaction between the RF source and the backscatter device can be modeled as an independent Rayleigh fading channel. Let h i Indicates the RF source and backscatter device A i Or the downlink channel between the eavesdropper Eve. i,j Indicates backscatter device A i With A j Inward channel between (i,j∈{1,2,...,N}, and i≠j), N is the total number of backscattering devices, the eavesdropper Eve can pretend to be a legitimate device to participate in the communication process; and h i h i,j represents the cascaded backscatter channel, which connects the downlink channel h i and inward channel h i,j .

[0039] The method provided in the embodiment of the present invention can be applied to electronic devices such as mobile terminals, personal notebook computers, supercomputers, etc. The embodiment of the present invention does not impose any restrictions on the specific type of electronic devices.

[0040] Example 2

[0041] Figure 2 The figure shows a flow chart of a method for generating a group key based on location information in backscatter communication according to an embodiment of the present invention. As an example and not a limitation, the method can be applied to any backscatter device A in the system.i The method may include steps S201-S205, each of which is described below.

[0042] S201, estimate the number of each other backscattering device A based on the received RF signal and the reflected signal. j coordinate information.

[0043] In some embodiments, the backscatter device A i Each other backscattering device A can be estimated based on the following steps S2011-S2013 j coordinate information.

[0044] S2011: Estimate location information of the radio frequency source according to the strength of the radio frequency signal transmitted by the radio frequency source.

[0045] For example, the location information of the radio frequency source may include the location of the radio frequency source relative to the backscattering device A. i Angle and distance (ie downlink channel h i distance).

[0046] In one possible implementation, all backscatter devices A i It can work in listening mode, receive RF signals from RF sources, estimate the average power of RF signals (used to characterize the strength of RF signals), and then send backscatter signals to other backscatter devices in the system. j The average power calculated by broadcasting; finally, the average power of each h can be estimated based on the average power of the RF signal calculated by oneself or received i The distance matrix of the downlink channel is obtained. At the same time, the arrival angle of the RF signal is used as the distance of the RF source relative to A. i Angle AoA i,RFS .

[0047] In an example, the average signal power of the RF signal in a time slot can be calculated using the following formula:

[0048]

[0049] in, Backscatter device A i The average signal power of the received RF signal during the measurement time T of the t1th time slot, h i distance, a(·) is the power attenuation function, P is the transmission power, ω i (t) is bandpass additive white Gaussian noise.

[0050] Exemplarily, the R2D(·) function may be used to convert the received signal strength matrix of the downlink channel into a distance matrix of the downlink channel, thereby obtaining the distance information of each downlink channel.

[0051] Specifically, the backscatter device A i The distance matrix of the downlink channel can be calculated by the following formula:

[0052]

[0053] in, Backscatter device A i The distance matrix of the downlink channel is obtained, A i The received signal strength matrix of the downlink channel is obtained.

[0054] S2012, estimate the other backscattering devices A based on the location information of the RF source and the strength and arrival angle of the composite signal j Relative A i location information.

[0055] Similarly, other backscatter devices A j Relative A i The location information may include A j Relative A i distance and angle.

[0056] In one possible implementation, the backscatter device A i The reflection distance and reflection angle can be estimated based on the strength of the composite signal and the signal arrival angle; the reflection distance and reflection angle are respectively subtracted from the relative value of the RF source to the backscattering device A. i The distance of the inward channel h i,j distance) and angle, and get the other backscattering device A j Relative backscatter device A i distance and angle.

[0057] In one example, different backscatter devices can be made to work in backscatter mode in different time slots, and only one backscatter device is allowed to backscatter in each time slot, ensuring that the device in listening mode can accurately estimate the distance of the cascaded backscatter channel. i At time slot t j A j The composite signal composed of the reflected signal and the RF signal. After that, the backscatter device A i The reflection distance can be estimated based on the average power of the composite signal; after N time slots, the backscattering device A iThe reflection distance matrix can be obtained.

[0058] For example, other backscatter devices A j Relative backscatter device A i The distance can be calculated by the following formula:

[0059]

[0060] in, A i The distance matrix of the inward channel is calculated by A j Relative A i The distance composition, is the reflection distance matrix.

[0061] Among them, the average power of the reflected signal The following formula can be satisfied:

[0062]

[0063] in, A i The data received by A in time slot t2 j The average power of the reflected signal generated, α j A j The backscatter coefficient, h is the inward channel i,j distance.

[0064] Alternatively, if the system includes N backscatter devices, there are a total of N(N-1) / 2 inbound channels in the group. Can be a The matrix of .

[0065] In one example, similarly, backscatter device A i The reflection angle matrix can be obtained based on the composite signal AoA i,j It is the signal arrival angle of the composite signal consisting of the RF signal and the reflected signal, which is composed of the reflection angle.

[0066] For example, backscatter device A i It can be obtained by the formula: AM 3 =AM 2 -AoA i,RFS =[AoA i,1 -AoA i,RFS ,AoA i,2 -AoA i,RFS ,…,AoA i,N -AoA i,RFS ], get Aj Relative A i angle.

[0067] S2013, according to other backscatter devices A j Relative A i The location information of other backscatter devices A is determined j coordinate information.

[0068] For example, other backscatter devices A j The coordinate information of other backscattering devices A j Local coordinates in the first coordinate system.

[0069] In one example, backscatter device A i You can use your own location as the origin and A i → The direction of the RF source is taken as the positive direction of the x-axis to establish the first coordinate system, based on other backscattering devices A j Relative A i The distance and angle of A j Local coordinates in the first coordinate system Get the local coordinate matrix

[0070] S202: Extract shared information from the coordinate information.

[0071] In some embodiments, see Figure 3 , the shared information can be extracted according to the following steps S2021 and S2012.

[0072] S2021, selecting a common reference point based on the local coordinates.

[0073] In one possible implementation, the center or centroid of the system can be selected as the common reference point. However, using the center as the reference point may lead to the risk of information leakage, as attackers may use the location information of backscatter devices to determine the center. Therefore, a weighted centroid calculation method can be used to select the common reference point.

[0074] In one example, after all backscatter devices in the system have completed mutual authentication, the RF source can assign a random weight to each backscatter device and cumulatively construct a private weight vector W = [W1; W2; ...; W N ] is sent to each backscatter device for storage. The backscatter device can be based on the local coordinate matrix Calculate the weight centroid with the private weight vector W and use the weight centroid as the public reference point RefPt i .

[0075] See also Figure 3, it is difficult for an attacker to obtain the private weight vector, and it is also difficult for him to infer the shared information.

[0076] For example, A i The formula can be Calculate the position of the common reference point.

[0077] Specifically, the two-dimensional coordinates of the common reference point can be expressed as

[0078] Optionally, the process of selecting the common reference point can be achieved by mapping function: Gen RefPt :P L →RefPt express.

[0079] S2022, other backscatter devices A j The local coordinates in the first coordinate system are converted into global coordinates in the second coordinate system to obtain the shared information.

[0080] In one possible implementation, a second coordinate system can be established with the common reference point as the origin and the direction from the common reference point to the RF source as the positive direction of the x-axis. Then, the local coordinate matrix Perform translation and rotation operations in different coordinate systems to obtain each A j Global coordinates in the second coordinate system Thus we get the global coordinate matrix

[0081] In one example, the process of transforming from the first coordinate system to the second coordinate system can be expressed as and They represent the left and right connections and the top and bottom connections of the two matrices respectively.

[0082] For example, the global coordinates can be calculated by the following formula:

[0083]

[0084] in, The rotation angle required to align the local coordinate system to the global coordinate system.

[0085] In a possible implementation, each backscatter device may perform the operations of extracting shared information shown in steps S201 and S202 multiple times, for example, K times, to obtain multiple sets of global coordinate matrices; and then combine the multiple sets of global coordinate matrices together as shared information. Wherein, k is a positive integer less than or equal to K, is the kth group of global coordinate matrix.

[0086] S203 , performing quantization, information negotiation, and privacy amplification operations on the shared information in sequence to obtain a group key for the backscatter communication system.

[0087] In some embodiments, see Figure 4 , the shared information can be quantized first, converting the analog signal into a binary digital signal; then, an information negotiation operation is performed on the digitized shared information to correct the erroneous information between the shared information generated by different backscattering devices; finally, a privacy amplification operation is performed to compress the negotiated shared information and generate the system's group key.

[0088] In one possible implementation, the quantization process may include two key stages: quantizer selection and sample allocation. These two steps may be performed based on the data type and user requirements.

[0089] In one example, quantizers can be broadly categorized into two types: amplitude quantizers and phase quantizers. Amplitude quantizers divide regions based on the amplitude of samples (i.e., the analog signals representing shared information), with boundaries defined by concentric circles. In contrast, phase quantizers divide regions based on the phase of samples, forming boundaries that radiate outward from the origin.

[0090] In one example, in the sample allocation stage, the sample space is divided into multiple quantization regions, and each sample is allocated to a corresponding region.

[0091] For example, the number of allocated regions may depend on the quantization level of the quantizer.

[0092] For example, if the quantization level of the quantizer is 1, the quantizer divides the coding space into 2 l When both amplitude and phase quantization are applied, the total number of regions is where l a and l p are the quantization levels of the amplitude and phase quantizers, respectively. Each sample receives an index corresponding to the region it belongs to; for example, the sample in the mth region has index m, meaning that samples within the same region have the same index. The device determines the sample index by assigning each bit of each global coordinate to its corresponding quantized region.

[0093] In one possible implementation, during the quantization phase, assigning the same bits of data to different quantization regions may lead to inconsistencies between key bits. To resolve these inconsistencies, various information coordination techniques can be implemented, including LDPC and Golay codes.

[0094] In one example, the Cascade technology may be selected for information coordination because the Cascade technology has the lowest information leakage and is less complex than the LDPC code.

[0095] In one possible implementation, privacy amplification aims to reduce the information an eavesdropper has about the key. This goal can be achieved by removing all potential information from the key sequence shared between legitimate communicators (such as backscatter devices). By using a universal hash function, the coordinated bit stream is converted into a highly random bit stream, thereby enhancing security.

[0096] The present invention calculates the location information of the device based on the signal strength and arrival angle, and uses the location information of all legitimate backscatter devices as shared information for key generation. There is no need to transmit other special detection signals for complex channel estimation, which can greatly reduce the computing cost of the device and the communication cost between devices, reduce the complexity of key generation, and improve the efficiency and robustness of key generation.

[0097] Furthermore, since an attacker cannot obtain the private weight vector, the present invention generates a public reference point based on the private weights and calculates shared information based on the public reference point, which can ensure that an attacker cannot obtain the true global position of the backscatter device, thereby improving the security performance of the system.

[0098] Example 3

[0099] Figure 5 The figure shows a schematic diagram of a scenario for generating a private weight vector in a static environment provided by an embodiment of the present invention.

[0100] In one possible implementation, see Figure 5 If the system is in a static state, the randomness of the group key cannot be guaranteed because the backscattering device remains stationary. Therefore, the first random parameter θ can be t Introducing the mapping function Gen RefPt In the modified mapping function Gen′ RefPt , based on the first random parameter θ t Generate random weights for each backscatter device to ensure the randomness of the random weights.

[0101] In one example, the first random parameter can be calculated based on the global coordinate matrix during the previous round of key generation.

[0102] At this point, the process of selecting the common reference point can be expressed by the mapping function as follows:

[0103]

[0104] For example, the first random parameter of dimension 1×N can be obtained by Calculate; where, is an N×dim matrix, dim represents the dimension, and O is a matrix with all 1s.

[0105] Therefore, the common reference point can be calculated by the following formula:

[0106]

[0107] Among them, RefPt t+1 is the public reference point selected for the key generation process in round t+1, is the local coordinate matrix of the t-th round key generation process, W t is the random weight of the t-th round key generation process, θ t is the first random parameter of the t-th round key generation process, W t+1 is the random weight of the key generation process in round t+1.

[0108] The new first random parameter of this round is generated by the position information during the previous round of key generation, thereby generating the common reference point of this round. This ensures that in a static environment, even if the position of the backscatter device in the group remains unchanged, the global position constructed in each round of key generation will also change randomly due to the random change of the reference point; thereby ensuring that the group key is still sufficiently random in a static environment and improving environmental adaptability.

[0109] Example 4

[0110] Because group membership frequently changes, attackers may exploit vulnerabilities in the network after these changes to launch attacks. For example, if an old device leaves a group and an attacker compromises it, they can use the group key saved before the old device left to decrypt messages encrypted with that key in existing groups. Therefore, implementing group key management, including key renewal and destruction, after generation is essential to reduce the risk of attackers gaining access to the key.

[0111] Figure 6 The figure shows a flow chart of a method for group key management based on location information in backscatter communication according to an embodiment of the present invention. By way of example and not limitation, this method can be used in the backscatter communication system described in Example 1. The method may include steps S601-S605, each of which is described below.

[0112] S601: Initialize the radio frequency source and backscatter device.

[0113] In one example, the RF source and each backscatter device in the system may first complete mutual authentication; thereafter, the RF source records the device information of each backscatter device, including its device characteristics c i, initialization is completed.

[0114] S602: The backscatter device generates a group key.

[0115] Exemplarily, the backscatter device may generate a group key based on the key generation method proposed in Embodiments 2 and 3.

[0116] Optionally, after the group key is generated, if there is a member change or the key has not been updated for a long time, the following step S604 may be performed.

[0117] Specifically, if the key has not been updated for a long time or a member has quit, the following step S604 can be performed; if a new member joins, the following step S603 must be performed first, and then the key is updated.

[0118] S603: The new backscatter device and the radio frequency source perform mutual authentication.

[0119] For example, when a new member (ie, a new backscatter device) joins the group, mutual authentication with the RF source is required to ensure that the legitimate backscatter device and the RF source can verify the identity of the new member and maintain the security and integrity of the group.

[0120] S604: The backscatter device updates the group key.

[0121] In some embodiments, group key update can adopt two methods: one is key regeneration and the other is partial key update.

[0122] Exemplarily, rekeying involves repeating step S602 to regenerate a new group key. Rekeying ensures a high degree of security and randomness because the new key is virtually unrelated to the old one; however, this process incurs significant communication and computational overhead. Partial rekeying involves modifying only a portion of the key, which has lower computational complexity but sacrifices security and randomness. Therefore, rekeying can be used to update the group key when the key has not been updated for an extended period of time; partial rekeying can be used to update the group key when membership changes occur.

[0123] In a possible implementation, the group key may be updated using a partial key update method based on the following steps S6041 to S6044.

[0124] S6041: The radio frequency source generates a second random parameter.

[0125] Exemplarily, the second random parameter may be a random number used to update the private weight vector.

[0126] S6042: The radio frequency source distributes a second random parameter to the backscatter device.

[0127] In a possible implementation, the radio frequency source may distribute the generated second random parameter to each backscatter device, enabling it to update the group key and the private weight vector.

[0128] In one example, since the system includes not only legitimate backscatter devices within the group but also illegitimate entities such as attackers, old members, and non-members, it is crucial to ensure that these illegitimate entities cannot obtain the second random parameter R. Using a two-end key to securely exchange random numbers between devices is inefficient and costly, as it requires the RF source to share a two-end with each legitimate backscatter device and involves multiple encryption and decryption processes between the RF source and the backscatter devices. Therefore, the device characteristics of the backscatter devices can be combined with the principle of secret sharing to broadcast R in a secure and efficient manner.

[0129] Specifically, the secret sharing principle means that during the secret sharing process, the 'distributor' (here, the RF source) distributes part of the secret to the 'participants' (here, the backscatter devices), but only when certain conditions are met can the 'participants' use their shares to reconstruct the complete secret information.

[0130] Therefore, the RF source can split the second random parameter according to the device characteristics of the backscatter device to obtain the broadcast information and send the broadcast information to the corresponding backscatter device. Since the RF source has the device characteristics of each backscatter device, and the backscatter device has its own device characteristics, the device characteristics c i Considered as part of the secret sent by the RF source to the backscatter device, R represents the complete secret. Unregistered entities cannot use their own device characteristics to recover the second random parameter.

[0131] Exemplarily, the broadcast information of the radio frequency source can be expressed as:

[0132]

[0133] Among them, b RFS is the set of broadcast information, G=[g1,g2,…,g N ] is a 0-1 vector that marks the legal backscatter devices in the group. If g i The value is 1, indicating that A i In the group; conversely, a value of 0 means A i Not in the group. For example, if A j Leave the group and notify the RF source, g j will be set to 0, making b RFS The jth item in becomes empty.

[0134] See also Figure 7When a new device wants to join a group or an old device wants to leave a group, it will send a join or leave notification to the RF source, and the RF source can obtain the information of the remaining legal backscatter devices in the system group. i Calculate b RFS , so that the backscattering device that has left the group, such as A j , you will not be able to use c j Recover the key R from the information broadcast by the RF source. Due to the uniqueness of the device characteristics, A j Unable to RFS The other terms in deduce R. Therefore, every legitimate backscatter device in the group can safely obtain R.

[0135] S6043: The backscatter device recovers the second random parameter.

[0136] For example, each legal backscatter device in the system can use b RFS The complete secret R is recovered by the corresponding entry in . For example, the backscatter device A1 in the group can recover the complete secret R according to Restore R.

[0137] S6044: The backscatter device updates the group key according to the second random parameter.

[0138] In one possible implementation, a bitwise operation can be performed on the original group key or private weight vector based on the second random parameter to obtain an updated group key or updated private weight vector. If the second random parameter is used to update the private weight vector, the updated group key must be subsequently determined based on the updated private weight vector using the methods of Embodiments 1 and 2 above.

[0139] In one example, the second random parameter may be used to flip or delete specific bits in the group key to obtain an updated group key.

[0140] For example, the group key updated using this method can be calculated using the following formula:

[0141] in

[0142] where GK′ is the updated group key, κ(R, GK) represents the bitwise operation on the group key GK using R, the function bin(·) is used to convert the number into binary form, and n represents the number of times the converted binary number should be repeated to ensure that the length of the resulting binary number is at least N bits.

[0143] In one example, to prevent departing members from obtaining updated private weight vectors, it is necessary to reduce the correlation between the new and old weight vectors. To reduce this correlation, methods such as feature construction and principal component analysis can be used. Although feature construction is particularly suitable for one-dimensional weight vectors, to reduce configuration costs, a method similar to that in Example 3 can be used to update the private weight vector based on a second random parameter.

[0144] For example, the private weight vector updated using this method can be calculated by the following formula:

[0145]

[0146] S605: A double-ended key is generated between the radio frequency source and the new backscatter device, and secure transmission is performed based on the double-ended key.

[0147] In one example, the RF source and the new backscatter device can generate a double-ended key, and then encrypt an updated group key or private weight vector using the double-ended key and transmit it to the new member so that it can participate in subsequent group key generation processes.

[0148] For example, a double-ended key may be used to protect the communication security between the new member and the radio frequency source.

[0149] The key management method provided by the present invention can improve distribution efficiency by distributing the second random parameter generated by the radio frequency source to each backscatter device based on the secret sharing principle; the second random parameter is used to update the key when a new member joins, and the updated key is sent to the new member after double-end encryption, which can ensure backward security; the second random parameter is used to update the key after the old member withdraws. Since the broadcast message of the second random parameter is calculated based on the device characteristics of the remaining backscatter devices in the group owner, the present invention can also ensure that the old member cannot obtain or generate a new group key, thereby ensuring forward security.

[0150] As an example, the backscatter communication system in this invention can be a multi-device collaborative smart home system. The backscatter devices in the system can be temperature and humidity sensors, security tags, smart lamps, smart door locks, and so on, and the RF source can be a central gateway. These devices rely on ambient RF energy for power and cannot support complex key negotiation protocols. Furthermore, in dynamic networking scenarios, frequent key updates are required to mitigate the risks associated with devices joining and leaving the system.

[0151] When a new smart home device is brought home, it needs to initialize its information and connect to the smart home network. To ensure the security of the existing home network, when a device initiates communication or requests to join the network, the gateway performs two-way authentication on each device to confirm its legitimacy. Once connected to the network, the device needs to exchange secure information with the gateway and other devices in the group. For example, a user issues a command in the bedroom. This command is encrypted and transmitted to the central processor, processed, and then forwarded to other devices in the home network to execute the corresponding operation. This command forwarding process relies on the group key to ensure the security of the information exchange.

[0152] To enable new devices to dynamically generate and update keys with the gateway or other devices after joining the network, the gateway broadcasts encrypted information over a backscatter link, providing key generation material for each device. The central gateway creates a group identifier for the home network and groups devices based on factors such as home usage and physical location.

[0153] To ensure the security of the entire home network and adapt to the dynamic addition of new devices, after a new device connects to the home network, it can use the new device joining protocol to efficiently and securely obtain the main group key, subgroup keys, and key update materials. At the same time, this protocol prevents new devices from obtaining previous versions of the key, thereby ensuring the forward security of information within the group. In a smart home, device locations may change frequently. Since location is one of the factors that determine device grouping, when a device's location changes, its group also changes, which can lead to scenarios where a device leaves the group. After an old device leaves, the old device leaving protocol is used to prevent the old device from knowing the group's future group keys, thereby ensuring the backward security of the original group information and keys.

[0154] As an example, the backscatter communication system in the invention can be an Industrial Internet of Things collaborative manufacturing system, and the backscatter devices in the system can be backscatter sensors, such as vibration monitoring tags and RFID material trackers. Because these devices are densely distributed and frequently mobile, the system must have low-latency group key distribution capabilities and strong resistance to man-in-the-middle attacks.

[0155] When a new sensor device joins the network, it must complete initialization and initiate a network access request. To ensure secure and stable network operation, the core gateway performs two-way authentication to verify the device's legitimacy. After successful network access, the new device exchanges encrypted data with the gateway and other devices in the group. The gateway broadcasts basic information, such as the encryption algorithm and initial key update materials, over a specific wireless link as the basis for secure communication between devices. The core gateway creates a dynamic group identifier based on factors such as production line layout, device functionality, and data interaction relevance. Group divisions are dynamically updated as production lines adjust or devices move, ensuring that devices are in the appropriate collaborative group. Sensor devices within the group jointly generate a group key using shared basic information and a specific key generation algorithm. This includes both large group keys and subgroup keys. Through a hierarchical key mechanism, secure transmission and refined management of production line data are achieved.

[0156] When a new device joins, the new device joining protocol is used to ensure that it can quickly and securely obtain the group key and key update materials. A key version management mechanism prevents new devices from obtaining expired keys, ensuring forward security. When a device's location changes, causing a group change, the system automatically triggers the group adjustment mechanism. When an old device leaves, the old device leaving protocol is activated to update the group key, ensuring backward security and preventing information leakage.

[0157] In the above embodiments, the description of each embodiment has its own focus. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant description of other embodiments.

Claims

1. A method for generating a group key based on position information in backscatter communication, characterized in that: The method is applied to any backscatter device A in a backscatter communication system. i Above, the method includes: Based on the received RF signal and the reflected signal, estimate the backscattering power of each other device A. j , wherein the radio frequency signal is the signal emitted by the radio frequency source, the reflected signal is the radio frequency signal reflected by the backscattering device, i, j∈{1,2,...,N}, and i≠j, N is the total number of backscattering devices in the system; extracting shared information from the coordinate information; The shared information is sequentially subjected to quantization, information negotiation, and privacy amplification operations to obtain a group key of the system.

2. The group key generation method according to claim 1, wherein: The method estimates the value of each other backscattering device A based on the received RF signal and the reflected signal. j Coordinate information, including: estimating the location information of the radio frequency source according to the strength and signal arrival angle of the radio frequency signal; According to the location information of the radio frequency source and the strength and signal arrival angle of the composite signal, the other backscattering device A is estimated. j coordinate information of the image processing unit, wherein the composite signal is composed of the radio frequency signal and the reflected signal.

3. The group key generation method according to claim 2, wherein: The position information of the radio frequency source includes the position information of the radio frequency source relative to the backscattering device A i Angle and distance; The estimating the location information of the radio frequency source according to the strength and signal arrival angle of the radio frequency signal includes: According to the average power of the radio frequency signal, it is estimated that the radio frequency source is relatively close to the backscattering device A. i distance; The signal arrival angle of the radio frequency signal is taken as the angle of arrival of the radio frequency source relative to the backscattering device A. i angle.

4. The group key generation method according to claim 3, wherein: The other backscatter device A j The coordinate information of the other backscattering device A j The local coordinates in the first coordinate system, wherein the first coordinate system is based on the backscattering device A i As the origin, the backscattering device A i The direction pointing to the radio frequency source is the positive direction of the x-axis of the first coordinate system; According to the location information of the radio frequency source and the strength and arrival angle of the composite signal, the other backscattering device A is estimated. j Coordinate information, including: estimating the reflection distance and reflection angle according to the intensity and signal arrival angle of the composite signal; The reflection distance and reflection angle are respectively subtracted from the value of the RF source relative to the backscattering device A. i The distance and angle of the other backscattering device A are obtained j Relative to the backscatter device A i distance and angle; According to the other backscatter device A j Relative to the backscatter device A i The distance and angle of the other backscatter device A are determined j Local coordinates in the first coordinate system.

5. The group key generation method according to claim 4, wherein: The extracting shared information from the location information includes: According to the other backscatter device A j The local coordinates in the first coordinate system determine the common reference point; The other backscatter device A j The local coordinates in the first coordinate system are converted into global coordinates in the second coordinate system to obtain the shared information, wherein the second coordinate system takes the common reference point as the origin, and the direction from the common reference point to the RF source is the positive x-axis direction of the second coordinate system.

6. The group key generation method according to claim 5, wherein: The common reference point is the weight center of mass of the system, which is obtained by multiplying the local coordinate matrix by the private weight vector. The local coordinate matrix is composed of the local coordinates of each backscatter device in the system, and the private weight vector is composed of random weights corresponding one-to-one to each backscatter device in the system.

7. The group key generation method according to claim 6, wherein: The random weight used in this round of key generation is the product of the random weight used in the previous round of key generation and a first random parameter, where the first random parameter is obtained based on the global coordinate matrix used in the previous round of key generation.

8. A group key management method based on location information in backscatter communication, characterized in that: The method is applied to a backscatter communication system, the system comprising a radio frequency source and a plurality of backscatter devices, and the method comprises: Initializing the radio frequency source and the backscattering device; The backscatter device generates a group key according to the group key generation method according to any one of claims 1 to 7; If any backscatter device leaves the system, or any backscatter device joins the system, the radio frequency source and the backscatter device update the group key to obtain an updated group key.

9. The group key management method according to claim 8, characterized in that: The radio frequency source and the backscatter device update the group key to obtain an updated group key, including: The radio frequency source generates a second random parameter, The radio frequency source generates a broadcast message according to the device characteristic of the backscatter device and the second random parameter, and sends the broadcast message to the backscatter device; The backscatter device recovers the second random parameter according to its own device characteristics and the broadcast message; The backscatter device updates the group key according to the second random parameter to obtain the updated group key.

10. The group key management method according to claim 9, characterized in that: Updating the group key according to the second random parameter to obtain the updated group key includes: Perform bit operations on the group key according to the second random parameter to obtain the updated group key: Alternatively, a random weight is generated according to the second random parameter, and shared information is updated based on the random weight, and the updated group key is determined according to the updated shared information; wherein the group key is obtained based on the shared information.

Images