ADS-B secure identity authentication method based on blockchain

Abstract

The present invention discloses a method for secure identity authentication of an ADS-B system based on blockchain, which belongs to the technical field of ADS-B systems and includes the following steps: a blockchain system setting phase, generating a genesis block and setting a smart contract and a consensus algorithm; a blockchain system registration phase, uploading a public key registration list to the blockchain; a blockchain system authentication phase, realizing ground station-to-aircraft authentication, aircraft-to-ground station authentication, and aircraft-to-aircraft authentication in the system; an on-chain public key update phase, ensuring real-time storage of the latest public key list on the chain; and an on-chain public key revocation phase, timely detecting and deleting illegal users. The present invention automatically realizes the registration, update, and revocation of user identity public keys. It not only solves the problem of dynamic identity legitimacy of ADS-B system members and ensures the integrity and non-repudiation of communication information, but also the PBFT consensus algorithm running at the same time better adapts to the proposed architecture and improves on-chain transaction efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of ADS-B systems, and in particular relates to an ADS-B security identity authentication method based on blockchain. Background Art

[0002] With the development of the economy and society, aircraft have become an essential means of transportation for both passenger travel and cargo transport. The US Federal Aviation Administration (FAA) predicts that the number of commercial air passengers will grow to 1.15 billion by 2033. To address this growing volume of air traffic, the FAA and the European Union have launched the Next Generation Air Transportation System (NextGen) and the Single European Sky Air Traffic Management Research (SESAR) projects. Automatic Dependent Surveillance-Broadcast (ADS-B) offers high accuracy and low cost compared to traditional primary and secondary radar surveillance technologies. Therefore, NextGen and SESAR consider ADS-B a key component of the next-generation air traffic surveillance system. ADS-B uses a fusion of Global Navigation Satellite System (GNSS) and inertial navigation data to determine an aircraft's position and broadcasts it periodically, which is then received by ground-based receivers. However, with the rapid development of radio broadcasting and information technologies, as well as the open nature of ADS-B, the vulnerability of ADS-B surveillance systems to radio frequency interference (RFI) and cyberattacks is increasing. Identifying anomalies and vulnerabilities in the ADS-B system helps improve the accuracy, integrity, continuity and availability of the surveillance system; reduces the required safety interval between aircraft and improves the ability to avoid collision threats; avoids the impact of severe weather and assists pilots and controllers in making correct strategic decisions.

[0003] Regarding ADS-B system security, research both domestically and internationally focuses on two key areas: secure broadcast authentication and secure position authentication. Secure broadcast authentication is a security enhancement method for the ADS-B data link that adds identity verification. It is achieved through encryption or non-encryption technologies such as embedded keys in the transmission device, the addition of identification codes, and fingerprint recognition. Secure position verification is a signal analysis method that uses geometric modeling and probabilistic analysis to verify the authenticity of aircraft position information. While verifying the accuracy of information, it also provides more positioning data, serving as an emergency alternative in the event of navigation system failure. Methods include multilateration, Kalman filtering, range bounds, and data fusion.

[0004] The encryption-based approach in secure broadcast identity authentication can achieve some success, but encryption involves key management issues, making centralized management susceptible to single points of failure. It also inevitably requires changes to existing message transmission protocols, making it challenging to implement. The openness of current and future civil aviation airspace and the proliferation of international routes also significantly increase the implementation complexity of encryption schemes. Non-encrypted schemes, however, employ techniques such as frequency spread hopping and fingerprinting for each signal. Adversaries can passively intercept and acquire large amounts of data, mimicking the signal and posing a threat to the system. Multi-lateration positioning in secure location verification can determine the target's true location and effectively identify false information caused by malicious interference. However, in practice, the precision and accuracy of TDOA measurements deteriorate or decrease dramatically with increasing distance and coverage, placing high demands on the number and spatial layout of deployed ADS-B IN base stations. The range boundary method uses a query-response method to determine the true location of the responding target, effectively identifying false information caused by malicious interference. However, it relies primarily on the delay between the query and reply signals to calculate distance. If a query is made to a hostile target, the enemy can modify the reply delay to mislead the interrogator. Kalman filtering can predict trajectory changes, but it can be misled by boiled frog attacks, misidentifying spoofed trajectories as true target trajectories. Group verification can obtain the target's true position through a multi-aircraft system in the air, effectively discerning false information caused by malicious jamming. However, deploying aircraft formations in civil aviation airspace is challenging. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide an ADS-B security identity authentication method based on blockchain, in view of the fact that ADS-B in the ADS-B system broadcasts information through open and unencrypted channels, which is vulnerable to various intentional intrusions and attacks and poses great security risks.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] A blockchain-based ADS-B secure identity authentication method includes the following steps:

[0008] S1: During the blockchain system setup phase, ADS-B ground stations form a consortium chain. These ground stations serve as fully functional nodes on the chain, with block creation and verification capabilities. The Civil Aviation Administration (CAA) generates the genesis block, deploys smart contracts, and sets up the system's PBFT consensus algorithm.

[0009] S2: During the blockchain system registration phase, the aircraft or ground station user locally generates a public-private key pair and sends the public key and identity information to the CAA. The CAA sets a validity period for the user's public key and sends the user's identity information, public key, public key validity period, and related signature back to the user. The CAA compiles a registration list of user public key information over a period of time and sends it along with its signature to the ADS-B ground station node. After verification, the ground station node runs the PBFT consensus algorithm to trigger the smart contract to upload the public key information list to the blockchain.

[0010] S3: Blockchain system authentication phase. Before takeoff, the aircraft injects the latest public key list of the synchronized ground station. During the flight, the ground station authenticates the aircraft, the aircraft authenticates the ground station, and the aircraft authenticates each other. The authentication process involves parsing the message information and querying the corresponding public key on the chain or locally stored for hash signature verification. If the verification is successful, the corresponding information is accepted; otherwise, it is discarded.

[0011] S4: During the on-chain public key update phase, when a user loses their private key or a new member joins the system, they generate a new public-private key pair locally and send it to CAA. CAA sends the updated public key list to the ground station node. The ground station node signs the updated public key list and successfully verifies the consensus, triggering the public key update function of the smart contract and uploading the user's updated public key list to the chain.

[0012] S5: During the on-chain public key revocation phase, if CAA detects that the user's private key is lost or the user's public key expires, it will trigger the public key revocation function of the smart contract to delete the user's on-chain public key information; if illegal behavior is detected by a user of the alliance chain system, the user's illegal behavior will be accumulated, and if it exceeds the limit, the public key revocation function of the smart contract will be triggered.

[0013] Furthermore, in step S1, the ADS-B ground stations, as fully functional nodes, form a consortium chain with block creation and verification capabilities. The chain stores the public key PK for secure identity authentication of message transmission. The Aviation Administration creates a blockchain account for each ADS-B ground station block node, initiates the generation of a genesis block, deploys smart contracts, and sets up a Practical Byzantine Fault Tolerance (PBFT) consensus method.

[0014] (1) Genesis block generation: First, the Aviation Administration generates a message and signs it. The signed message is transmitted to all ground station nodes through a secure channel. After receiving the CAA's signed message, the ground station node verifies the signature. After the verification is passed, the witness node writes a new block under the PBFT mechanism. The witness node then immediately propagates the block. After consensus is completed, the message is written into the block. If the signature verification fails, the node issues a warning message about the CAA being hacked or a fake CAA attack. After consensus is reached, the block is written and the CAA is checked and restored through manual intervention. At this point, the genesis block is completed.

[0015] (2) Smart contract deployment: CAA sets the content of the smart contract and signs the contract, and then sends the contract to each node through P2P. The node verifies the content of the contract and runs the PBFT consensus protocol, writes the contract into the block and broadcasts it. After the contract deployment is successful, the blockchain automatically creates the contract address. Only the Aviation Administration and each node of the blockchain can send transactions to trigger the execution of the smart contract. The smart contract has the functions of registration, public key list update, and public key list revocation.

[0016] Furthermore, in step S2, the aircraft and ground station are collectively referred to as users. First, they confirm the identity information ID and generate a public-private key pair locally. Then, they send their identity information and public key secure channel to CAA. CAA queries the identity information. If it has not been applied for before, it assigns a public key validity period to the user, and then signs it and sends it to the user. CAA can form a registration list of user public keys for a period of time. register Send it to the ground station, the ground station will verify the signature of the registration list and reach a consensus. If the consensus is successful, the registration transaction will be triggered. register Added to the blockchain.

[0017] Furthermore, in step S3, before the aircraft takes off, aircraft i first synchronizes the public key list information of the ground station to facilitate query and use during the flight; during the flight, system authentication includes ground station authentication to aircraft, aircraft authentication to ground station authentication, and aircraft authentication to aircraft;

[0018] The ground station authenticates the aircraft: The aircraft embeds the current timestamp, broadcast information, and signature of the broadcast information into the ME field of the ADS-B message, and the identity information into the AA field, and then broadcasts the message. The ADS-B ground station that first receives the message parses the message, queries the corresponding public key and public key validity period based on the aircraft's identity information chain, and verifies the signature information. If the PBFT consensus is passed, the message from aircraft i is accepted; otherwise, it is discarded.

[0019] Aircraft to ground station authentication: If the ADS-B ground station receives the public key list of the user updated by CAA After verification, it is signed and the current timestamp is generated. The ground station's identity information, current timestamp, updated public key list, and its corresponding signature are transmitted to the aircraft. The aircraft queries the corresponding public key and public key validity period stored locally based on the ground station's identity information, verifies the timestamp and the ground station's signature, and synchronizes the updated public key list to the local storage if passed. Otherwise, the information is discarded.

[0020] Aircraft-to-aircraft authentication: Aircraft A embeds the generated current timestamp, message information, and signature of the message information into the ME field of the ADS-B message, embeds the identity information into the AA field, and then broadcasts the message; if aircraft B receives the message information from aircraft A, it parses the message and queries the locally stored public key list based on aircraft A's identity information to find the corresponding public key and public key validity period; it verifies the timestamp and signature of aircraft A. If they pass, it receives the message information from aircraft A; otherwise, it determines that aircraft A is an illegal user and discards its information.

[0021] Furthermore, in step S4, when the private key of an aircraft or ground station user is lost, a new public-private key pair (NewPK, NewSK) needs to be generated, and the identity information and the new public key are sent to the Aviation Administration Center CAA through a secure channel. The CAA queries the corresponding previous public key information based on the identity information and deletes it, and stores the new public key information locally. When a new member user joins, a new public-private key pair (NewPK, NewSK) is generated locally, and the identity information and the new public key are also sent to the CAA through a secure channel. The CAA confirms whether the application has been made based on the identity information. If not, the new public key information is stored locally. The CAA sets a new validity period for the new public key, and sends the user identity, the corresponding new public key, the validity period of the new public key, and the corresponding signature to the user through a secure channel.

[0022] CAA signs the public key update list for a period of time, and sends the updated public key list and the corresponding signature to the ground station node. The ground station node verifies the signature. After successful verification, it runs the consensus protocol to trigger the public key update function of the smart contract and add the user's new public key information list to the blockchain.

[0023] Furthermore, in step S5, when the user's private key is lost or the public key expires, if the CAA queries it, it will trigger the public key revocation function of the blockchain smart contract and revoke the corresponding public key on the user chain; when any ground station detects that an aircraft has malicious behavior, if it is verified that it is not a legitimate aircraft, no communication will be carried out. If it is a legitimate user in the system, the aircraft's malicious behavior will be recorded on the chain. If the aircraft's on-chain malicious behavior record exceeds a certain limit, it will trigger the public key revocation function of the blockchain smart contract and revoke the aircraft's on-chain public key.

[0024] The beneficial effects of the present invention are as follows: based on the distributed, transparent, traceable, and tamper-proof security features of the blockchain itself, the present invention proposes a fusion alliance blockchain architecture solution, which solves the problem that ADS-B information is open and vulnerable to attacks such as interception and tampering, fills its privacy loopholes, and ensures the reliable operation of the ADS-B system network and the security of communications between members. It gets rid of the reliance of the traditional ADS-B key management solution on the Public Key Infrastructure (PKI) and has stronger robustness against single point failures. By adopting smart contract technology, the user public key is automatically registered, updated, and revoked on the blockchain, which improves the efficiency of key management. At the same time, the identity authentication method in the blockchain architecture adopts the digital signature method, and the message is signed to ensure the integrity and authentication of the information, thereby ensuring the security authentication between the members of the ADS-B system, preventing illegal users from committing evil and joining, and ultimately ensuring the safety and efficiency of air traffic operations.

[0025] Other advantages, objectives and features of the present invention will be described in the following description and will be apparent to those skilled in the art to some extent, or those skilled in the art can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to make the purpose, technical solutions and beneficial effects of the present invention more clear, the present invention provides the following drawings for illustration:

[0027] Figure 1 This is a security architecture diagram of the ADS-B system based on blockchain;

[0028] Figure 2 ADS-B message data block and modification diagram;

[0029] Figure 3 Schematic diagram of the system authentication stage. DETAILED DESCRIPTION

[0030] Figure 1 This invention incorporates the highly open, real-time, and multi-node requirements of the ADS-B system, designing a consortium blockchain-based ADS-B system security architecture. The high-performance blockchain consensus algorithm and inter-node smart contract execution safeguard the ADS-B system's blockchain-based security performance. This architecture comprises five phases: blockchain system setup, blockchain system registration, blockchain system authentication, on-chain public key updates, and on-chain public key revocation.

[0031] Step 1: Blockchain system setup phase

[0032] Blockchain is a specific data structure that combines data blocks in a chain in chronological order, and is a decentralized shared ledger that is cryptographically guaranteed to be tamper-proof and non-forgeable. The security requirements of the ADS-B system coincide with the technical characteristics of blockchain (decentralization, tamper-proofing, and traceability). All nodes in the system have equal rights and good fault tolerance. Using blockchain technology to establish trust relationships between distributed nodes can solve problems such as centralized inefficiency and data insecurity. The alliance chain is a blockchain between public and private chains, and is jointly maintained by an alliance composed of all parties corresponding to each node. In order to strengthen the secure transmission of ADS-B messages and prevent malicious deception of ADS-B message information, the ADS-B ground station in the present invention forms an alliance chain. The ground station on the chain serves as a full-function node with block creation and verification functions. The blockchain technology is integrated with the security requirements of ADS-B message transmission into one, which is called the ADS-B message consortium chain. In order to achieve real-time and secure transmission between aircraft and ground stations, and between aircraft, and prevent interference from malicious users, the relevant public key PK for secure identity authentication of message transmission is realized by blockchain technology.

[0033] The Aviation Administration creates a blockchain account for each ground station node using an account generation tool (the public key information is the user's address on the blockchain). The CAA initiates the generation of the genesis block, and then deploys the smart contract and sets the PBFT consensus algorithm. The ground station genesis block is formed and the smart contract is deployed as follows.

[0034] (1) Genesis block generation: CAA generates a message m C , signed as α C =sig C H(m C ), and x={m C , α C} is sent to all nodes, and the nodes use pk after receiving it C To verify the signature, if the verification is successful, run a round of PBFT protocol to reach a consensus, and {m C , α C}Write the block and broadcast it. If the signature verification fails, the node will send a message m g = {CAA is hacked or fake CAA is attacked} warning, run a round of PBFT protocol and send the message m g ={CAA is hacked or fake CAA is attacked} is written into the block and broadcast. At this time, CAA requires manual intervention for inspection and recovery.

[0035] (2) Smart Contract Arrangement: To run the ADS-B message consortium chain, the CAA sets the contract content. To ensure the validity of the contract, the CAA signs the contract and then sends the contract to each node via P2P. The node verifies the contract content and runs the PBFT consensus protocol, writes the contract into the block, and broadcasts it. After the contract is successfully arranged, the blockchain automatically creates the contract address. Only the Aviation Administration and each node of the blockchain can send transactions to trigger the execution of the smart contract. The smart contract has functions such as registration, public key list update, and public key list revocation.

[0036] Step 2: Blockchain system registration phase

[0037] Blockchains generally use a Proof of Work (POW) consensus mechanism to reach consensus, which is unsuitable for the real-time, fast authentication requirements of the ADS-B system. This invention, which uses a Practical Byzantine Fault Tolerance (PBFT) algorithm consensus mechanism, integrates ADS-B ground stations into a consortium blockchain network. This shortens block generation time to meet the ADS-B system's requirement for rapid consensus, while also tolerating less than one-third of invalid or malicious nodes.

[0038] The aircraft and the ground station (collectively referred to as user U) first determine the identity information ID. The aircraft's identity information is the globally unique 24-bit address assigned to the aircraft by the International Civil Aviation Organization (ICAO). User U locally generates a public-private key pair (PK U , SK U ), (ID U , PK U ) is sent to the Aviation Administration through a secure channel, and CAA first confirms the ID U Has it been applied for? If not, set the validity period for the public key. U And for the user (ID U , PK U , VP U ) to sign α C =sig C H(ID U , PK U , VP U ), and replace {ID U , PK U , VP U , α C}Sent to the user through a secure channel.

[0039] CAA will contain the user's public key PK within a period of time U The message list that makes up the registration list l register ={l,sig CH(l)} is sent to all ground station nodes, and the ground station nodes first verify the CAA signature message list after receiving it. register If the verification is successful, a round of PBFT algorithm is run to reach a consensus, triggering the register function of the smart contract and registering the user public key information list l <register,l,sig C H(l)> is added to the blockchain.

[0040] Step 3: Blockchain system authentication stage

[0041] The authentication process stores ADS-B system messages and other related data on the blockchain based on the one-way nature of the blockchain's hash function and the non-repudiation of digital signatures. If an attacker attempts to tamper with the data, they must not only modify the hash value of the current block, but also the hash values ​​of all blocks, greatly increasing the difficulty and cost of the attack.

[0042] 1 Before takeoff

[0043] Before the aircraft takes off, it is necessary to synchronize the latest public key list of the ground station to obtain the list newes t={l newest Due to the large amount of data, fiber-optic communication is used. Fiber-optic communication, with its fast transmission speeds, low energy consumption, and large bandwidth, has found widespread application in airport communication networks. Fiber-optic network technology is now relatively mature, and its cost and transmission efficiency are superior to those of cables, making it widely used in airport communication networks.

[0044] 2 During the flight

[0045] 1) Ground station certification of aircraft

[0046] Aircraft i generates the current timestamp t i , and sign the broadcast message m with α(m), and timestamp t i , message information m and signature α(m) are embedded in the ME field of the ADS-B message, and the aircraft ID i Embedded in the AA field of the ADS-B message, and then broadcast the message, Figure 2 The message format of the present invention is modified.

[0047] The earliest ADS-B ground station to receive the message parses the message and obtains {ID i ,α(m),m,t i}, according to the aircraft's ID i Query the stored public key list on the chain and obtain the corresponding public key and validity period VP i First determine the message time t iIs VP valid? i When the message time t i ∈VP i When the public key corresponding to aircraft i is used Verify the signature α(m). After verification, the ground station node generates an authentication message Auth-i = (ID i ,α(m),t i ) and broadcast the execution of PBFT consensus. After the consensus is reached, the aircraft is considered to be a legitimate user to receive the ADS-B message information of aircraft i and can make corresponding feedback. Otherwise, the aircraft i is judged to be an illegal user and its message information is discarded.

[0048] 2) Aircraft certification of ground stations

[0049] ADS-B airborne systems have both ADS-B IN and ADS-B OUT transceiver functions. Currently, the ADS-B OUT function is fully functional. In actual use, the ADS-B IN function has been verified between aircraft, but it is not yet perfect when receiving ADS-B ground station messages. However, the IN function is already under planning and implementation. We assume that the ADS-B IN function is complete and can realize the transmission of information from the ground station to the aircraft in the blockchain-based ADS-B architecture. Therefore, the aircraft can obtain the latest user public key list in the architecture, improving the efficiency of real-time identity authentication between aircraft. Figure 3 This is a system authentication block diagram of the present invention.

[0050] If the ADS-B ground station receives the latest user (new or revoked) public key list updated by CAA First verify the CAA signature sig C (H(l update )), after verification, run PBFT consensus. After consensus is completed, the ADS-B ground station will update the public key list list update Sign it And generate the current timestamp t G , then the message Transmitted to aircraft i, aircraft i receives First, according to the ID G Traverse the local storage list to obtain its corresponding public key and VP G , judgment time t G ∈VP G Is it valid? Then verify the corresponding signature sig G (H(l update)), after the verification is passed, the updated public key list will be synchronized to the local storage. If the verification fails, the ADS-B ground station will be judged as an illegal ground station and its information will be discarded.

[0051] 3) Aircraft-to-aircraft certification

[0052] Aircraft A also generates the current timestamp t A , and sign the broadcast message m with α(m), and timestamp t A , message information m and signature α(m) are embedded in the ME field of the ADS-B message, and the aircraft ID A It is embedded in the AA field of the ADS-B message and then broadcasts the message.

[0053] If aircraft B receives the message, it first parses the message to obtain {ID A ,α(m),m,t A}, according to the aircraft's ID A Query the locally stored public key identity list list and obtain the corresponding public key and validity period VP A First determine the message time t A Is VP valid? A When the message time t A ∈VP A When the public key corresponding to aircraft A is used Verify the signature α(m). After verification, receive the ADS-B message information of aircraft A and make corresponding flight feedback (avoidance, high flying, low flying, etc.). Otherwise, judge aircraft A as an illegal user and discard its message information.

[0054] Step 4: Update public key on the chain

[0055] Since the public key is broadcasted by the blockchain, it is easy for users outside the alliance chain to obtain it. In order to prevent information from being stolen or attacked, user U (aircraft or ground station) can regenerate a new public-private key pair (NewPK u , NewSK U ), (ID U , NewPK U ) is sent to CAA through a secure channel, and CAA queries the user's ID U and the corresponding previous public key, delete the user's previous public key from its own database, and save the new public key. Similarly, when a new member joins, he / she will add his / her own public key (ID U , NewPK U ) is also sent to CAA through a secure channel, and CAA first confirms the user ID UCheck if it has been applied for. If not, save the new public key. Then set a new validity period NewVP U , and for the user (ID U 、NewPK U 、NewVP U ) to sign α C ′=sig C H(ID U , NewPK U , NewVP U ), and replace {ID U 、NewPK U 、NewVP U , α C ′} is sent to the user through a secure channel.

[0056] CAA updates the user identity public key list l' information list New ′={l′, sig C H(l′)} is sent to the ground station node, and the ground station node first verifies the CAA signature message list after receiving it. New ′, if the verification is successful, a round of PBFT protocol will be run. After reaching a consensus, the updatePK function of the smart contract will be triggered to update the user's identity public key information list l′ <updatePK,l′,sig C H(l′)> is added to the blockchain.

[0057] Step 5: On-chain public key revocation

[0058] If a user's private key is lost or stolen, or if a user on the blockchain engages in illegal behavior, the corresponding public key needs to be revoked in a timely manner to ensure the security of system communications.

[0059] If the private key of a legitimate user is lost or the VP is invalid, if CAA finds out, CAA will trigger the revokePK of the blockchain smart contract and cancel the user's transaction r= <revokePK,ID U , PK U , VP U >Added to the blockchain.

[0060] If any ground station G detects malicious behavior of aircraft i, it will not communicate if it is an illegal aircraft. If it is a legitimate user in the system, it will send a malicious behavior transaction to aircraft i. The PBFT protocol is run, and after reaching a consensus, a malicious behavior of aircraft i is recorded on the blockchain. If the malicious behavior of aircraft i exceeds N (a set threshold), that is, n(r′) ≥ N is added to the blockchain, the revokePK of the smart contract is triggered, and the cancellation transaction of aircraft i is recorded on the blockchain. Added to the blockchain.

[0061] Malicious aircraft behavior includes self-destruction, attacks, eavesdropping, forgery, and vulnerabilities. Different malicious behaviors may cause different degrees of consequences. These malicious behaviors can be classified and graded according to the severity of the consequences. They can be roughly divided into the following three levels: Level 1, damage to information integrity; Level 2, damage to information validity; and Level 3, damage to information privacy. Classifying and grading malicious behaviors facilitates effective management and proactive prevention of malicious behaviors.

[0062] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present invention.

Claims

1. A blockchain-based ADS-B secure identity authentication method, characterized by: The following steps are involved: S1: During the blockchain system setup phase, ADS-B ground stations form a consortium chain. These ground stations serve as fully functional nodes on the chain, with block creation and verification capabilities. The Civil Aviation Administration (CAA) generates the genesis block, deploys smart contracts, and sets up the system's PBFT consensus algorithm. S2: During the blockchain system registration phase, the aircraft or ground station user locally generates a public-private key pair and sends the public key and identity information to the CAA. The CAA sets a validity period for the user's public key and sends the user's identity information, public key, public key validity period, and related signature back to the user. The CAA compiles a registration list of user public key information over a period of time and sends it along with its signature to the ADS-B ground station node. After verification, the ground station node runs the PBFT consensus algorithm to trigger the smart contract to upload the public key information list to the blockchain. S3: Blockchain system authentication phase: Before takeoff, the aircraft injects the latest public key list of the synchronized ground station. During the flight, this includes: ground station authentication to aircraft, aircraft authentication to ground station, and aircraft authentication to aircraft. The authentication process is to perform hash signature verification on the corresponding public key on the query chain or locally stored for message information parsing. If the verification is successful, the corresponding information will be received, otherwise it will be discarded. S4: During the on-chain public key update phase, when a user loses their private key or a new member joins the system, they generate a new public-private key pair locally and send it to CAA. CAA sends the updated public key list to the ground station node. The ground station node signs the updated public key list and successfully verifies the consensus, triggering the public key update function of the smart contract and uploading the user's updated public key list to the chain. S5: During the on-chain public key revocation phase, if CAA detects that the user's private key is lost or the user's public key expires, it will trigger the public key revocation function of the smart contract to delete the user's on-chain public key information; if illegal behavior is detected by a user of the alliance chain system, the user's illegal behavior will be accumulated, and if it exceeds the limit, the public key revocation function of the smart contract will be triggered.

2. The blockchain-based ADS-B secure identity authentication method according to claim 1, characterized in that: In step S1, the ADS-B ground station, as a fully functional node, forms a consortium chain with block creation and verification capabilities. The chain stores the public key PK for secure identity authentication of message transmission. The Aviation Administration creates a blockchain account for each ADS-B ground station block node, initiates the generation of the genesis block, deploys smart contracts, and sets up a practical Byzantine Fault Tolerance (PBFT) consensus method. (1) Genesis block generation: First, the Aviation Administration generates a message and signs it, and transmits the signed message to all ground station nodes through a secure channel. After receiving the CAA's signed message, the ground station node verifies the signature. After the verification is passed, the witness node writes a new block under the PBFT mechanism, and then the witness node immediately propagates the block. After the consensus is completed, the message is written into the block; if the signature verification fails, the node issues a warning message about the CAA being hacked or a fake CAA attack. After the consensus is completed, the block is written and the CAA is checked and restored through manual intervention. At this point, the genesis block is completed; (2) Smart contract deployment: CAA sets the content of the smart contract and signs the contract, and then sends the contract to each node through P2P. The node verifies the content of the contract and runs the PBFT consensus protocol, writes the contract into the block and broadcasts it. After the contract deployment is successful, the blockchain automatically creates the contract address. Only the Aviation Administration and each node of the blockchain can send transactions to trigger the execution of the smart contract. The smart contract has the functions of registration, public key list update, and public key list revocation.

3. The blockchain-based ADS-B secure identity authentication method according to claim 1, characterized in that: In step S2, the aircraft and ground station are collectively referred to as users. First, they confirm their identity information ID and generate a public-private key pair locally. They then send their identity information and public key secure channel to CAA. CAA queries the identity information and if it has not been applied for before, it assigns a public key validity period to the user, then signs it and sends it to the user. CAA can form a registration list of user public keys for a period of time. register Send it to the ground station, the ground station will verify the signature of the registration list and reach a consensus. If the consensus is successful, the registration transaction will be triggered. register Added to the blockchain.

4. The blockchain-based ADS-B secure identity authentication method according to claim 1, characterized in that: In step S3, before the aircraft takes off, aircraft i first synchronizes the public key list information of the ground station to facilitate query and use during the flight; During the flight, system certification includes ground station to aircraft certification, aircraft to ground station certification, and aircraft to aircraft certification; The ground station authenticates the aircraft: The aircraft embeds the current timestamp, broadcast information, and signature of the broadcast information into the ME field of the ADS-B message, and the identity information into the AA field, and then broadcasts the message. The ADS-B ground station that first receives the message parses the message, queries the corresponding public key and public key validity period based on the aircraft's identity information chain, and verifies the signature information. If the PBFT consensus is passed, the message from aircraft i is accepted; otherwise, it is discarded. Aircraft to ground station authentication: If the ADS-B ground station receives the public key list of the user updated by CAA After verification, it is signed and the current timestamp is generated. The ground station's identity information, current timestamp, updated public key list, and its corresponding signature are transmitted to the aircraft. The aircraft queries the corresponding public key and public key validity period stored locally based on the ground station's identity information, verifies the timestamp and the ground station's signature, and synchronizes the updated public key list to the local storage if passed. Otherwise, the information is discarded. Aircraft-to-aircraft authentication: Aircraft A embeds the generated current timestamp, message information, and signature of the message information into the ME field of the ADS-B message, embeds the identity information into the AA field, and then broadcasts the message; if aircraft B receives the message information from aircraft A, it parses the message and queries the locally stored public key list based on aircraft A's identity information to find the corresponding public key and public key validity period; it verifies the timestamp and signature of aircraft A. If they pass, it receives the message information from aircraft A; otherwise, it determines that aircraft A is an illegal user and discards its information.

5. The blockchain-based ADS-B secure identity authentication method according to claim 1, characterized in that: In step S4, when the private key of an aircraft or ground station user is lost, a new public-private key pair (NewPK, NewSK) needs to be generated, and the identity information and the new public key are sent to the Aviation Administration Center (CAA) through a secure channel. The CAA queries the corresponding previous public key information based on the identity information and deletes it, and stores the new public key information locally. When a new member user joins, a new public-private key pair (NewPK, NewSK) is generated locally, and the identity information and the new public key are also sent to the CAA through a secure channel. The CAA confirms whether the application has been made based on the identity information. If not, the new public key information is stored locally. The CAA sets a new validity period for the new public key and sends the user identity, the corresponding new public key, the validity period of the new public key, and the corresponding signature to the user through a secure channel. CAA signs the public key update list for a period of time, and sends the updated public key list and the corresponding signature to the ground station node. The ground station node verifies the signature. After successful verification, it runs the consensus protocol to trigger the public key update function of the smart contract and add the user's new public key information list to the blockchain.

6. The blockchain-based ADS-B secure identity authentication method according to claim 1, characterized in that: In step S5, when the user's private key is lost or the public key expires, if the CAA queries it, it will trigger the public key revocation function of the blockchain smart contract and revoke the corresponding public key on the user chain; when any ground station detects that an aircraft has malicious behavior, if it is verified that it is not a legitimate aircraft, no communication will be carried out. If it is a legitimate user in the system, the aircraft's malicious behavior will be recorded on the chain. If the aircraft's on-chain malicious behavior record exceeds a certain limit, it will trigger the public key revocation function of the blockchain smart contract and revoke the aircraft's on-chain public key.

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