Safe and trusted access method combining equipment radio frequency fingerprint authentication and block chain

Abstract

The invention provides a secure and trusted access method combining equipment radio frequency fingerprint authentication and a block chain, which comprises the following steps: a registration stage: each equipment node receives a registration request, acquires an equipment signal from to-be-registered terminal equipment to generate a radio frequency fingerprint, and binds and stores the radio frequency fingerprint and identity information to the block chain; an authentication stage: generating a radio frequency fingerprint to be authenticated when each device node receives the authentication request, comparing the radio frequency fingerprint with the radio frequency fingerprint on the block chain, and storing the state of successful authentication to the block chain if the comparison succeeds; and a key generation stage: sending a pilot signal between each equipment node and the terminal equipment to obtain a channel estimation value, quantizing the channel estimation value into a binary sequence, negotiating to obtain a candidate key, and processing by using a privacy amplification technology to obtain a final key. According to the invention, the block chain with high security is combined with the radio frequency fingerprint capable of uniquely identifying the identity of the equipment, so that the security of the terminal equipment when accessing the network is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of wireless device network access, and in particular relates to a secure and trusted access method combining device radio frequency fingerprint authentication and blockchain. Background Art

[0002] Radio Frequency Fingerprinting (RFF) is a technology that realizes device identification based on transmitter-related signal characteristics. Its basic idea is to extract RF characteristics such as carrier frequency offset, IQ imbalance, and nonlinear offset of RF components in the transmitted signal, and establish a mapping from characteristics to device identity to uniquely identify the transmitting device. RF fingerprint technology has the advantages of low communication and computing overhead, no sense, and continuity, and has become one of the key technologies for wireless device identification.

[0003] As a radio identification technology based on radio signal characteristics, RF fingerprint technology has been widely used in device identification. The existence of RF fingerprint is due to some defects within the error range caused by problems such as insufficient manufacturing process of the device's RF transceiver. These defects are unique, unforgeable and environmentally independent, resulting in different characteristics of RF signals sent by different devices. RF fingerprint technology is to generate a unique identifier for the device node by collecting and analyzing the RF signal emitted by the device, which is used to identify and authenticate the source of the RF signal. Compared with traditional device identity authentication methods, such as authentication methods based on cryptographic algorithms, RF fingerprint technology has great advantages: first, RF fingerprint technology can realize the authentication of the signal emission source without third-party security facilities, while traditional cryptography-based authentication requires at least a secure server for identity storage or secure physical channel transmission of authentication keys; second, RF fingerprint technology has stronger concealment. RF fingerprint is based on the characteristics of the device's RF circuit itself, and does not require sending additional content to assist in identification, which reduces the energy consumption of the device, avoids the interference of attackers on specific authentication processes, and enhances the concealment of the identification process. Third, radio frequency fingerprint technology has strong real-time performance. When the device sends signals for communication, the identification process can be carried out in real time through the acquired communication signals, with a fast response speed, ensuring the security and efficiency of tracking and detecting the device.

[0004] Blockchain technology, also known as distributed ledger technology, is an emerging technology in which several nodes jointly participate in "bookkeeping" and jointly maintain a complete distributed database. Blockchain technology has become a potential solution to the identity authentication problem due to its decentralized, tamper-proof and transparent characteristics.

[0005] Current identity authentication technology has the following flaws:

[0006] (1) In most RFID fingerprint-based identity authentication methods, the fingerprint data is stored in a centralized database. Once the database is attacked and data is leaked, the security of the authentication will be lost.

[0007] (2) The distributed network access method based solely on blockchain cannot guarantee the authenticity and reliability of user identity information before it is uploaded to the chain. Even if the key generation method is used and the generated key is stored on the blockchain, it will rely on a third-party identity authentication system, making it difficult to achieve true decentralization. Summary of the invention

[0008] In order to solve the above problems existing in the prior art, the present invention provides a secure and trusted access method combining device radio frequency fingerprint authentication and blockchain. The technical problem to be solved by the present invention is achieved through the following technical solutions:

[0009] A secure and trusted access method combining device radio frequency fingerprint authentication and blockchain includes:

[0010] Registration stage:

[0011] Once each device node receives a registration request sent by a terminal device to be registered within its jurisdiction, it collects device signals from the terminal device to be registered, generates a radio frequency fingerprint of the device to be registered using the device signals, and binds the radio frequency fingerprint with the identity information of the device to be registered and stores it on the blockchain;

[0012] Certification stage:

[0013] Once each device node receives an authentication request sent by a terminal device to be authenticated within its jurisdiction, it collects a device signal from the terminal device to be authenticated, and uses the device signal to generate a radio frequency fingerprint to be authenticated; the radio frequency fingerprint is compared with the radio frequency fingerprint on the blockchain, and if the comparison is successful, the authentication success status is stored on the blockchain;

[0014] Key generation phase:

[0015] A pilot signal is sent between each device node and the terminal device to obtain a channel estimation value; the channel estimation value is quantized into a binary sequence, and then a candidate key is obtained through negotiation; the candidate key is processed using privacy amplification technology to obtain a final key, so that the final key can be used for encryption during mutual communication.

[0016] Beneficial effects:

[0017] 1. The present invention combines the RF fingerprint of the device with the blockchain technology to achieve secure and reliable access to the device in the distributed network. While ensuring the uniqueness and non-replicability of the terminal device identity, it also enhances the security of RF fingerprint storage, provides strong protection for transaction information such as RF fingerprint and authentication records, and prevents malicious tampering. After the node device completes the authentication of the terminal device, the terminal device also authenticates the legitimacy of the node device, achieving two-way authentication, which can effectively prevent pseudo nodes;

[0018] 2. In the registration and authentication stage, the present invention designs a smart contract, which automatically handles the device registration and authentication process, reduces human intervention, and improves the overall efficiency and reliability of the method;

[0019] 3. Any transaction information of the terminal device of the present invention in the network will be recorded on the blockchain, and each device node that maintains the blockchain can share this information. Due to the transparency and traceability of the blockchain, when the terminal device switches across zones, the current device node can reduce the amount of signal samples required to be collected and speed up the learning of the device fingerprint, and use all the transaction information of the device at the previous node to assist in authentication, thereby improving access efficiency while ensuring security.

[0020] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the distribution of node devices and terminal devices proposed in the present invention;

[0022] Figure 2 It is a flow chart of a secure and trusted access method combining device radio frequency fingerprint authentication and blockchain proposed by the present invention;

[0023] Figure 3 It is a detailed flow chart of the present invention at the registration stage;

[0024] Figure 4 is a differential constellation diagram obtained by processing the collected device signals in an embodiment of the present invention;

[0025] Figure 5 It is a framework diagram of the key generation performed by the device and the node in the key generation phase of the present invention;

[0026] Figure 6a-6b This is a diagram showing the result of key generation by both the terminal device and the node device according to an embodiment of the present invention;

[0027] Figure 7 This is a diagram showing the result of uploading transaction information to the blockchain in an embodiment of the present invention. DETAILED DESCRIPTION

[0028] The present invention is further described in detail below with reference to specific embodiments, but the embodiments of the present invention are not limited thereto.

[0029] Combination Figures 1 to 3 The present invention provides a secure and trusted access method combining device radio frequency fingerprint authentication and blockchain, including:

[0030] Registration stage:

[0031] Once each device node receives a registration request sent by a terminal device to be registered within its jurisdiction, it collects device signals from the terminal device to be registered, generates a radio frequency fingerprint of the device to be registered using the device signals, and binds the radio frequency fingerprint with the identity information of the device to be registered and stores it on the blockchain;

[0032] refer to Figure 2 The device nodes communicate with each other and share information on the chain through the blockchain. Each device node is responsible for the access services of multiple terminal devices within its jurisdiction.

[0033] In practical applications, the device node may be a satellite, or a control device or other electronic device, and the present invention does not limit this.

[0034] Certification stage:

[0035] Once each device node receives an authentication request sent by a terminal device to be authenticated within its jurisdiction, it collects a device signal from the terminal device to be authenticated, and uses the device signal to generate a radio frequency fingerprint to be authenticated; the radio frequency fingerprint is compared with the radio frequency fingerprint on the blockchain, and if the comparison is successful, the successful authentication status of the terminal device to be authenticated is stored on the blockchain;

[0036] The present invention can set up a comparison model, which can adopt a neural network model to determine whether the comparison is successful by calculating the similarity between the generated radio frequency fingerprint and the radio frequency fingerprint on the blockchain.

[0037] Key generation phase:

[0038] A pilot signal is sent between each device node and the terminal device to obtain a channel estimation value; the channel estimation value is quantized into a binary sequence, and then a candidate key is obtained through negotiation; the candidate key is processed using privacy amplification technology to obtain a final key, so that the final key can be used for encryption during mutual communication.

[0039] Of course, the device node also sends its own RF fingerprint (also stored on the blockchain) to the terminal device. The terminal device calls the comparison model through the smart contract to compare whether the information is consistent with the node fingerprint information pre-stored on the blockchain to prevent the occurrence of pseudo device nodes.

[0040] If the authentication is successful, it proves that the device node is legitimate and not a fake device node, and both parties proceed to generate the subsequent key. If the authentication fails, the authentication phase is exited, and the terminal device can reselect a device node for access.

[0041] The present invention can deploy a blockchain model on the device node to record transaction information such as registration, authentication and communication of the terminal device. The data on the chain is jointly maintained by these device nodes, and each device node can share all transaction information on the chain through the blockchain. Record the transaction information such as registration, authentication and communication of the terminal device. The data on the chain is jointly maintained by these device nodes, and each device node can share all transaction information on the chain through the blockchain; the key generation module is deployed on all device nodes and the terminal device that wants to access the device node, and is used for the key generation of subsequent encrypted communication after the device authentication is successful, so as to ensure the security of communication.

[0042] In a specific embodiment of the present invention, reference Figure 3 , the step of generating a radio frequency fingerprint using the device signal includes:

[0043] a. Preprocessing and differential processing are performed on the device signal in sequence to obtain a differential constellation diagram;

[0044] b. clustering the trajectory points in the differential constellation diagram using a k-means clustering algorithm to obtain a plurality of clusters and a cluster center of each cluster;

[0045] c. The sum of the intra-class distances of each cluster and the average intra-class distance are combined into a feature vector as the RF fingerprint of the device; the sum of the intra-class distances is the sum of the distances between the sample points in each cluster and the cluster center point of the cluster, and the average intra-class distance is the average distance between the sample points in each cluster and the cluster center point of the cluster.

[0046] In a specific implementation manner of the present invention, the step of sequentially preprocessing and differentially processing the device signal to obtain a differential constellation diagram includes:

[0047] a1, performing down-conversion processing on the device signal to obtain a baseband signal of the device signal;

[0048] The terminal device may be a wireless device with a carrier frequency offset, and the signal transmitted by the terminal device may be expressed as:

[0049]

[0050] Where S(t) is the baseband signal of the transmitter on the terminal device, F(·) represents the signal amplitude distortion caused by the inherent defects of the transmitter hardware, X(t) represents the transmitted signal, and f cTx is the carrier frequency of the transmitter.

[0051] After down-converting the received device signal, the baseband signal representation of the received signal can be obtained:

[0052]

[0053] Among them, f cRx is the carrier frequency of the receiver on the node device, It is the phase error when the receiver receives the signal;

[0054] Due to different hardware damages of the transmitter and receiver, there are certain differences in the carrier frequency offset. cRx ≠f cTx When the receiver down-converts, the baseband signal obtained is expressed as:

[0055]

[0056] Where Δ = f cRx -f cTx Indicates the carrier frequency offset between the transmitter and the receiver.

[0057] a2, performing point-by-point differential processing on the baseband signal to obtain a differential processing signal;

[0058] Perform point-by-point differential processing on the baseband signal Y(t):

[0059]

[0060] Where D(t) is the difference result, (·) * is the conjugate operation, and n is the difference interval.

[0061] a3, the differential processing signal is plotted on the complex plane to obtain a differential constellation diagram, such as Figure 4 shown.

[0062] In a specific implementation of the present invention, clustering the trajectory points in the differential constellation diagram using a k-means clustering algorithm to obtain a plurality of clusters and a cluster center of each cluster includes:

[0063] b1, randomly selecting k sample points in the differential constellation diagram as initial cluster centers;

[0064] Assume that the set C contains K clusters, represented by x i , i ranges from 1 to K, and the mean points of each cluster are m1m2…m k , which is the cluster center of the cluster.

[0065] b2, calculate the distance from each sample point to each cluster center;

[0066] b3, according to the nearest neighbor principle, each sample point is divided into the cluster with the closest cluster center;

[0067] b4, based on the value of the error square sum criterion function for each cluster; where the error square sum criterion function is expressed as: m i For cluster x i The cluster center of , p is the sample point.

[0068] b5, calculate the mean coordinates of all sample points in each cluster, and use the mean coordinates to update the cluster center in the cluster;

[0069] b6, recalculate the value of the error square sum criterion function of each cluster after updating the cluster center. If the difference between the value and the value before updating is not greater than the threshold, output the clustering result; if it is greater than the threshold, return to b2 until the maximum number of iterations is reached, and output the clustering result; the clustering result includes multiple clusters and the cluster center of each cluster.

[0070] It is worth noting that the value of the recalculated error square sum criterion function is expressed as E′. If |EE′|≤α (where α is a preset threshold), it means that the clustering criterion function converges and the clustering result is output. Otherwise, b2 is returned.

[0071] In a specific implementation manner of the present invention, the sending of a pilot signal between each device node and the terminal device to obtain a channel estimation value includes: each device node and each terminal device performing the following process:

[0072] Using the channel to send a pilot signal to the other party;

[0073] A reception signal carrying channel information is received from the channel, and a channel estimation value is estimated using the reception signal.

[0074] This implementation manner adopts a lightweight and senseless channel detection method based on DM-RS to provide a formatted channel estimation matrix for channel key generation, that is, a matrix composed of channel estimation values.

[0075] When receiving a signal, the following model is established for the channel:

[0076] Y l,d =H l,d X l,d +Z l,d

[0077] Where, X l,d is a known signal, called the reference signal; Y l,d Indicates receiving signal; H l,d is the abstracted channel matrix; Z l,d is additive white Gaussian noise, Channel matrix H l,d Indicates the influence of the radio propagation environment during signal transmission. In the channel estimation process, the channel estimation based on the reference signal is performed using the following formula to obtain the channel estimation value:

[0078]

[0079] In the formula,

[0080]

[0081] In a specific embodiment of the present invention, reference Figure 5 , converting the channel estimation value into a binary sequence as a candidate key comprises:

[0082] Filtering the channel estimation value by using a moving mean filtering method to obtain a filtered channel estimation value;

[0083] This step uses the moving mean filter method as a preprocessing method to optimize the efficiency of the measurement during quantization and enhance the reciprocity of channel measurement. Taking the MAF processing on the device side as an example, use represents the channel detection result sequence of the device, where K represents the subcarrier function of the downlink signal. Then the filtering function is:

[0084]

[0085] In the formula, is the result of MAF, s is the step size, w is the window size of the moving average, M is the length of the result,

[0086] quantizing the filtered channel estimation value into a binary sequence based on a local increment and monotonicity quantization method;

[0087] Using the binary sequence as an initial key;

[0088] The initial key is negotiated using an improved Cascade protocol to obtain a candidate key.

[0089] In a specific implementation of the present invention, the quantization method based on local increment and monotonicity, quantizing the filtered channel estimation value into a binary sequence includes:

[0090] The difference between the channel estimation value at the current moment and the channel estimation value at the previous moment is taken as the forward difference;

[0091] The difference between the channel estimation value at the current moment and the channel estimation value at the next moment is taken as the backward difference;

[0092] According to the forward difference and the backward difference of the channel estimation value at the current moment, the channel estimation value is classified to obtain a classification result;

[0093] According to the quantization method corresponding to the classification result, the channel estimation value at the current moment is quantized into a binary sequence.

[0094] This implementation adopts a quantization method based on local increment and monotonicity to quantize the channel estimation value at the current moment, wherein the quantization function is as follows:

[0095]

[0096] in, and They represent the forward difference and backward difference of the channel estimation value, respectively, and are calculated as follows:

[0097]

[0098] From the quantization function, we can know that the classification results can classify the channel estimation values ​​into four categories: the channel estimation values ​​are locally monotonically increasing, locally monotonically decreasing, locally non-monotonic but its value increases, and locally non-monotonic but its value decreases. Therefore, according to the four categories, corresponding to different quantization methods, the binary number of 0 or 1 can be output, and finally a binary sequence can be obtained.

[0099] In a specific implementation manner of the present invention, the step of negotiating the initial key using the improved Cascade protocol to obtain the candidate key includes:

[0100] a. Group the initial key into groups of 3 bits, and perform a parity check on each group to obtain a check sequence; perform a parity check on each group, as shown in the following formula:

[0101] S C [p] = K C [3p-2]⊕K C [3p-1]⊕K C [3p]

[0102] In the formula, S C is the calculated group check code, K C Represents the binary sequence that needs to be calculated;

[0103] b. The device node and the terminal device exchange the verification sequence through wireless communication;

[0104] c. Delete the groups with different bits in its own check sequence and the exchanged check sequence, and connect the deleted binary sequences to form a new binary sequence;

[0105] d, permuting the new binary sequence to obtain a permuted binary sequence; the permutation function is as follows:

[0106]

[0107] In the formula, Q1-Q3 represents the set to which array number l belongs, and q represents the number of groups;

[0108] K′ C Represents a binary sequence after discarding different groups, and:

[0109]

[0110] e. Repeat steps a to c once for the replaced binary sequence to obtain the initial check binary sequence;

[0111] f, the initial check binary sequence is checked using CRC, and the initial check binary sequence that passes the check is used as a candidate key, such as Figure 6a-6b shown.

[0112] If the CRC checksum is the same, the symmetric key is generated successfully. Otherwise, the candidate key generation process needs to be restarted from channel detection.

[0113] In a specific implementation of the present invention, the step of processing the candidate key using the privacy amplification technology to obtain the final key includes:

[0114] The candidate key is processed using the Security Hash Algorithm 256 (SHA-256) to obtain the final key.

[0115] After the key generation is completed, it means that the terminal device has been successfully connected through the device node and can enjoy normal network services. Both parties can use the key to encrypt and transmit information. All information in this process will also be recorded on the blockchain. The blockchain uploads transaction information such as Figure 7 shown.

[0116] In reality, terminal devices are not always stationary. When a terminal device is moving, it may leave the coverage area of ​​the current device node and move to the coverage area of ​​another node. The method provided by the present invention can improve the handover efficiency of the terminal device while ensuring security. The following is a brief description of this process:

[0117] Step 1: When the terminal device is at the edge of the network signal coverage of the current device node, it automatically detects the signal strength of the neighboring device nodes, selects a device node with the strongest signal, and sends a switching authentication request;

[0118] Step 2: The device node that receives the authentication request first queries the blockchain for all previous transaction information of the terminal device to ensure the legitimacy of the device, and at the same time requires the device node to which the terminal device is currently connected to send the current location and status of the device node terminal;

[0119] Step 3: The device node that receives the authentication request collects the signal of the terminal device. Due to the stability of the RF fingerprint information and the security of the blockchain, the device node does not need to collect enough sample signals for fingerprint learning as when the device first accesses the network. It only needs to collect a small amount of samples and combine them with the fingerprint of the device and the transaction information on the blockchain for auxiliary authentication.

[0120] Step 4: After the device node that receives the authentication request successfully authenticates, it sends its own fingerprint information to the terminal device for two-way authentication.

[0121] Step 5: If the authentication is successful, the terminal device disconnects from the current device node and connects to the new device node. Both parties generate new keys for encrypted communication.

[0122] It is worth noting that the terms "first" and "second" in the present invention are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0123] Although the present application is described herein in conjunction with various embodiments, in the process of implementing the claimed application, those skilled in the art may understand and implement other variations of the disclosed embodiments by reviewing the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other components or steps, and "a" or "an" does not exclude a plurality of components or steps.

[0124] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the scope of protection of the present invention.

Claims

1. A secure and trusted access method combining device radio frequency fingerprint authentication and blockchain, characterized in that: include: Registration stage: Once each device node receives a registration request sent by a terminal device to be registered within its jurisdiction, it collects device signals from the terminal device to be registered, generates a radio frequency fingerprint of the device to be registered using the device signals, and binds the radio frequency fingerprint with the identity information of the device to be registered and stores it on the blockchain; Certification stage: Once each device node receives an authentication request sent by a terminal device to be authenticated within its jurisdiction, it collects a device signal from the terminal device to be authenticated and uses the device signal to generate a radio frequency fingerprint to be authenticated; The radio frequency fingerprint is compared with the radio frequency fingerprint on the blockchain. If the comparison is successful, the authentication success status is stored on the blockchain; Key generation phase: Each device node sends a pilot signal to the terminal device to obtain a channel estimation value; the channel estimation value is quantized into a binary sequence, and then a candidate key is obtained through negotiation; The candidate key is processed using privacy amplification technology to obtain a final key, so that the final key can be used for encryption during mutual communication.

2. The secure and trusted access method combining device radio frequency fingerprint authentication and blockchain according to claim 1 is characterized in that: The device nodes communicate with each other and share information on the blockchain through the blockchain. Each device node is responsible for access services for multiple terminal devices within its jurisdiction.

3. The secure and trusted access method combining device radio frequency fingerprint authentication and blockchain according to claim 1 is characterized in that: The generating of the radio frequency fingerprint by using the device signal comprises: a. Preprocessing and differential processing are performed on the device signal in sequence to obtain a differential constellation diagram; b. clustering the trajectory points in the differential constellation diagram using a k-means clustering algorithm to obtain a plurality of clusters and a cluster center of each cluster; c. The sum of the intra-class distances of each cluster and the average intra-class distance are combined into a feature vector as the RF fingerprint of the device; the sum of the intra-class distances is the sum of the distances between the sample points in each cluster and the cluster center point of the cluster, and the average intra-class distance is the average distance between the sample points in each cluster and the cluster center point of the cluster.

4. The secure and trusted access method combining device radio frequency fingerprint authentication and blockchain according to claim 3 is characterized in that: The step of sequentially preprocessing and differentially processing the device signal to obtain a differential constellation diagram includes: a1, performing down-conversion processing on the device signal to obtain a baseband signal of the device signal; a2, performing point-by-point differential processing on the baseband signal to obtain a differential processing signal; a3, plotting the differential processed signal on a complex plane to obtain a differential constellation diagram.

5. The secure and trusted access method combining device radio frequency fingerprint authentication and blockchain according to claim 3 is characterized in that: The clustering of the trajectory points in the differential constellation diagram using the k-means clustering algorithm to obtain multiple clusters and the cluster center of each cluster includes: b1, randomly selecting k sample points in the differential constellation diagram as initial cluster centers; b2, calculate the distance from each sample point to each cluster center; b3, according to the nearest neighbor principle, each sample point is divided into the cluster with the closest cluster center; b4, the value of the error sum of squares criterion function calculated for each cluster; b5, calculate the mean coordinates of all sample points in each cluster, and use the mean coordinates to update the cluster center in the cluster; b6, recalculate the value of the error square sum criterion function of each cluster after updating the cluster center. If the difference between the value and the value before updating is not greater than the threshold, output the clustering result; if it is greater than the threshold, return to b2 until the maximum number of iterations is reached, and output the clustering result; the clustering result includes multiple clusters and the cluster center of each cluster.

6. The secure and trusted access method combining device radio frequency fingerprint authentication and blockchain according to claim 1 is characterized in that: The sending of a pilot signal between each device node and the terminal device to obtain a channel estimation value includes: each device node and each terminal device performs the following process: Using the channel to send a pilot signal to the other party; A reception signal carrying channel information is received from the channel, and a channel estimation value is estimated using the reception signal.

7. The secure and trusted access method combining device radio frequency fingerprint authentication and blockchain according to claim 1 is characterized in that: The converting the channel estimation value into a binary sequence as a candidate key comprises: Filtering the channel estimation value by using a moving mean filtering method to obtain a filtered channel estimation value; quantizing the filtered channel estimation value into a binary sequence based on a local increment and monotonicity quantization method; Using the binary sequence as an initial key; The initial key is negotiated using an improved Cascade protocol to obtain a candidate key.

8. The secure and trusted access method combining device radio frequency fingerprint authentication and blockchain according to claim 7 is characterized in that: The quantization method based on local increment and monotonicity, quantizing the filtered channel estimation value into a binary sequence includes: The difference between the channel estimation value at the current moment and the channel estimation value at the previous moment is taken as the forward difference; The difference between the channel estimation value at the current moment and the channel estimation value at the next moment is taken as the backward difference; According to the forward difference and the backward difference of the channel estimation value at the current moment, the channel estimation value is classified to obtain a classification result; According to the quantization method corresponding to the classification result, the channel estimation value at the current moment is quantized into a binary sequence.

9. The secure and trusted access method combining device radio frequency fingerprint authentication and blockchain according to claim 7 is characterized in that: The adopting the improved Cascade protocol to negotiate the initial key to obtain the candidate key comprises: a. Grouping the initial key into groups of 3 bits, and performing a parity check on each group to obtain a check sequence; b. The device node and the terminal device exchange the verification sequence through wireless communication; c. Delete the groups with different bits in its own check sequence and the exchanged check sequence, and connect the deleted binary sequences to form a new binary sequence; d, permuting the new binary sequence to obtain a permuted binary sequence; e. Repeat steps a to c once for the replaced binary sequence to obtain the initial check binary sequence; f. Use CRC to verify the initial verification binary sequence, and use the initial verification binary sequence that passes the verification as a candidate key.

10. The secure and trusted access method combining device radio frequency fingerprint authentication and blockchain according to claim 1 is characterized in that: The step of processing the candidate key by using the privacy amplification technology to obtain the final key includes: The candidate key is processed using the secure hash 256 algorithm to obtain a final key.

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