Multi-device communication key negotiation method based on V2X vehicle formation

Abstract

The invention provides a multi-device communication key negotiation method, and the method comprises the steps: generating a corresponding private key and a scalar multiplication point for each device, the scalar multiplication point being a product of the private key and an elliptic curve base point; each device broadcasts a scalar multiplication point corresponding to the device and receives scalar multiplication points of other devices, and each device calculates a shared key by using a private key of the device and the received scalar multiplication point based on a pairing strategy; encrypted communication between the devices is performed using the shared key. The method has the beneficial effects that the authenticity and integrity of the message are verified by fusing and using certificate signature, the confidentiality of the message is ensured by using the secret key negotiation based on the scalar multiplication point and the private key, the dynamic secret key updating is realized, and the communication security is ensured in multiple aspects.

Description

Technical Field

[0001] The present invention belongs to the field of information security, and particularly relates to a multi-device communication key negotiation method based on V2X vehicle platooning. Background Art

[0002] With the development of V2X communication technology, vehicles are interconnected with each other, as well as with pedestrians and traffic facilities, forming a new application scenario of vehicle, pedestrian and infrastructure interconnection. Intelligent connected vehicles and intelligent vehicle-road collaborative systems, which mainly focus on vehicle driving safety, traffic efficiency improvement and information services, have become the focus of this trend.

[0003] At present, the C-V2X standard has covered core technologies such as the access layer, network layer, message layer and security, and the standard system has been initially formed, and it has the conditions for large-scale deployment and industrialization. The current standards and application scenarios mainly focus on using V2X communication technology as a long-distance sensor for vehicles to obtain more surrounding information, such as vehicle speed, position, intention, etc., to achieve functions such as message warning and assisted autonomous driving. Typical application scenarios include: 18 scenarios in the first stage: forward collision warning, intersection collision warning, left turn assistance, blind spot warning, lane change assistance, reverse overtaking warning, emergency braking warning, abnormal vehicle reminder, vehicle out-of-control warning, road hazard condition reminder, speed limit warning, red light running warning, vulnerable road user collision warning, green wave speed guidance, forward congestion reminder, emergency vehicle reminder, in-vehicle signs, vehicle near-field payment;

[0004] 12 typical scenarios in the second stage: perception data sharing, cooperative lane change, cooperative vehicle merging, cooperative intersection communication, differential data service, dynamic lane management, cooperative priority vehicle passing, yard path guidance service, floating car data collection, vulnerable road user safety communication, cooperative vehicle platooning management, road toll service.

[0005] The main problems of the existing technical solutions are as follows:

[0006] Since the standard mainly considers large-scale interconnection and communication efficiency, the main current problem is that although these messages carry signature information, they are all broadcast in plain text, and there is a risk of message theft;

[0007] When a large number of vehicles need to negotiate keys, the current main negotiation method is still one-to-one negotiation, which has problems such as multiple negotiations and low time-consuming efficiency, and is not convenient for large-scale encrypted communication;

[0008] There is no convenient, effective and reliable encrypted communication and encrypted key management update mechanism. Encryption is usually processed in a simple way with a fixed symmetric key, and there is a risk of key leakage. Summary of the Invention

[0009] In view of this, the present invention aims to propose a multi-device communication key negotiation method based on V2X vehicle platooning, in order to solve at least one of the above-mentioned partial technical problems.

[0010] To achieve the above object, the technical solution of the present invention is realized as follows:

[0011] The first aspect of the present invention proposes a multi-device communication key negotiation method, and the method includes:

[0012] S1. Generate a corresponding private key and a scalar multiplication point for each device, where the scalar multiplication point is the product of the private key and the base point of the elliptic curve;

[0013] S2. Each device broadcasts its corresponding scalar multiplication point and receives the scalar multiplication points of the other devices. Each device calculates a shared key based on the pairing strategy, using its own private key and the received scalar multiplication points;

[0014] S3. Use the shared key to perform encrypted communication between each device.

[0015] Further, the pairing strategy is:

[0016] Set a security parameter k and generate a prime number p with a length of k bits;

[0017] Use the base point P on the elliptic curve to generate a cyclic additive group G1 of order p and a cyclic multiplicative group G T , and obtain two integers a and b;

[0018] If e: G1*G1→G T , then for any g1∈G1, g2∈G2, there is

[0019] The second aspect of the present invention proposes a multi-device communication key negotiation method based on V2X vehicle platooning, applying the multi-device communication key negotiation method described in the first aspect. The method includes the following steps:

[0020] Create a vehicle platoon: The leading vehicle broadcasts a vehicle platoon creation command and a vehicle platoon information table, and updates the leading vehicle information to the vehicle platoon information table;

[0021] Join the vehicle platoon: The free vehicle sends a join application to the leading vehicle by broadcasting. The leading vehicle receives the application and updates the free vehicle information to the vehicle platoon information table, and the free vehicle becomes a following vehicle;

[0022] Key negotiation: All vehicles in the vehicle platoon obtain the information of the other vehicles in the vehicle platoon according to the vehicle platoon information table, and calculate a shared key using the multi-device communication key negotiation method, and use the last 16 bytes of the shared key as the communication key;

[0023] Encrypted communication: The leading vehicle encrypts and signs the information using the communication key and then broadcasts it.

[0024] Key update: When there are changes in the fleet members or the usage duration of the current communication key reaches the replacement threshold, the key is updated according to the content of the current fleet information table.

[0025] Fleet disbanding: When the fleet needs to be disbanded, the leading vehicle broadcasts a fleet disbanding request. All vehicles update the fleet information table and destroy the key to complete the disbanding of the fleet.

[0026] Furthermore, during the process of creating the fleet:

[0027] The broadcast contains the signature of the leading vehicle and the scalar multiplication point. The receiving vehicle verifies the signature of the broadcast according to the public key.

[0028] The fleet information table records the vehicle ID, fleet ID, vehicle role, vehicle status, open status, and scalar multiplication point list.

[0029] Furthermore, the process of joining the fleet includes:

[0030] The joining application contains the free vehicle scalar multiplication point and is signed using the free vehicle private key.

[0031] After receiving the joining request, the leading vehicle verifies the legality of the joining request. After passing the verification, it uses the scalar multiplication point to verify the signature. After passing the verification, it updates the free vehicle's scalar multiplication point to the fleet information table and updates the free vehicle's role to a following vehicle.

[0032] The following vehicle verifies the legality of the leading vehicle's broadcast and verifies the signature of the broadcast according to the public key of the leading vehicle in the broadcast. After passing the verification, it completes the operation of joining the fleet.

[0033] Furthermore, the process of encrypted communication includes:

[0034] The leading vehicle encrypts the original information using the communication key and the SM4 algorithm, signs the encrypted information using the private key of the leading vehicle through the SM2 algorithm, and broadcasts the signed information.

[0035] The following vehicle verifies the legality of the broadcast information and verifies the signature of the broadcast using the public key in the fleet information table. After passing the verification, it decrypts the encrypted information using the communication key and the SM4 algorithm to obtain the original information.

[0036] Furthermore, the process of key update includes:

[0037] The leading vehicle and the following vehicle perform a key negotiation operation through broadcast every 5 minutes to obtain a new communication key.

[0038] When the leading vehicle detects the joining of a free vehicle, it updates the information in the vehicle formation information table and broadcasts the updated vehicle formation information table. The following vehicle uses the updated vehicle formation information table to generate a new communication key.

[0039] Furthermore, the vehicle ID is assigned by the leading vehicle; the vehicle roles include leading vehicle, free vehicle, and following vehicle; the vehicle states include applying to join the formation and following; the open states include open formation and stopped formation.

[0040] Compared with the prior art, the multi-device communication key negotiation method based on V2X vehicle formation of the present invention has the following beneficial effects:

[0041] At the same time, it combines the use of certificate signatures to verify the authenticity and integrity of messages, uses a mechanism based on the scalar multiplication point key negotiation mechanism to ensure the confidentiality of messages, and a dynamic key update mechanism to ensure the security of communication in multiple aspects.

[0042] The key is renegotiated every 5 minutes, and when there is a new device joining or a device exiting, the key can be negotiated in a timely manner. This dynamic key update encryption mechanism effectively improves data security, effectively prevents the risk of the key being exposed due to long-term use, and reduces the possibility of brute force cracking.

[0043] The management of the key is updated in real time according to the state of the vehicle. The key state is divided into an initial state, a key update state, an encryption state, and a key destruction state as the vehicle formation disbands. Using this mechanism simplifies key management. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0045] Figure 1 is a schematic flowchart of the multi-device communication key negotiation method according to an embodiment of the present invention;

[0046] Figure 2 is a schematic flowchart of the multi-device communication key negotiation method based on V2X vehicle formation according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0047] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0048] In the description of the present invention, it should be understood that the orientation or positional relationships indicated by the terms "center", "longitudinal", "lateral", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise stated, the meaning of "plural" is two or more.

[0049] In the description of the present invention, it should be noted that unless otherwise clearly defined and limited, the terms "installed", "connected", "coupled" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood through specific situations.

[0050] The present invention will be described in detail below with reference to the drawings and in conjunction with embodiments.

[0051] A multi-device communication key negotiation method, the method comprising:

[0052] Generating a corresponding private key and a scalar multiplication point for each device, where the scalar multiplication point is the product of the private key and the base point of the elliptic curve;

[0053] Each device broadcasts its corresponding scalar multiplication point and receives the scalar multiplication points of the other devices, and each device calculates a shared key based on a pairing strategy using its own private key and the received scalar multiplication points;

[0054] Performing encrypted communication between each device using the shared key.

[0055] In some embodiments, assume there are three vehicles with V2X communication capabilities, CAR1(a, aP), CAR2(b, bP), CAR3(c, cP), where P is the base point on the elliptic curve, and a, b, c are the private keys of the vehicles respectively. aP, bP, cP become the scalar multiplication points.

[0056] Each vehicle broadcasts its own scalar multiplication point through V2X, and the other vehicles perform the following operations on the received scalar multiplication points:

[0057] CAR1: keyA = e(bP, cP)^a = e(P, P)^(abc)

[0058] CAR2: keyB = e(aP, cP)^b = e(P, P)^(abc)

[0059] CAR3: keyC = e(aP, bP)^c = e(P, P)^(abc)

[0060] Due to the properties of bilinear pairing, these three expressions will ultimately result in e(P, P)^(abc). Each participating party uses its own private key (a, b, or c) and the scalar multiplication points of the other two parties for calculation. Although the paths are different, the final results are the same.

[0061] An actual calculation example is shown in the following table:

[0062]

[0063] For more vehicles that need to negotiate, by analogy with the above formula, for the states of creating, joining, leaving, and disbanding a vehicle fleet, the implementation mechanism of existing standards can be referred to. On this basis, we conduct key negotiation among multiple devices for encrypted communication. This mechanism can be extended to many similar scenarios, such as encrypted communication in multi-party walkie-talkies and so on.

[0064] The pairing strategy is as follows: Set a security parameter k and generate a prime number p with a length of k bits;

[0065] Use the base point P on the elliptic curve to generate a cyclic additive group G1 of order p and a cyclic multiplicative group G T , and obtain two integers a and b;

[0066] If e: G1 * G1 → G T , then for any g1 ∈ G1, g2 ∈ G2, there is

[0067] A multi-device communication key negotiation method based on V2X vehicle formation. Applying the above multi-device communication key negotiation method, the method includes the following steps:

[0068] Create a vehicle fleet: The leading vehicle broadcasts a vehicle fleet creation command and a vehicle fleet information table, and updates the leading vehicle information to the vehicle fleet information table;

[0069] Join the vehicle fleet: The free vehicle sends a join application to the leading vehicle via broadcast. The leading vehicle receives the application and updates the free vehicle information to the vehicle fleet information table, and the free vehicle becomes a following vehicle;

[0070] Key negotiation: All vehicles within the convoy obtain information of the remaining vehicles in the convoy according to the convoy information table, and use the multi-device communication key negotiation method to calculate the shared key, and use the last 16 bytes of the shared key as the communication key;

[0071] Encrypted communication: The lead vehicle encrypts and signs the information and then sends it via broadcast;

[0072] Key update: When there are changes in convoy members or the usage duration of the current communication key reaches the replacement threshold, update the key according to the content of the current convoy information table;

[0073] Convoy disbanding: When the convoy needs to be disbanded, the lead vehicle broadcasts a convoy disbanding request, and all vehicles update the convoy information table and destroy the key to complete the convoy disbanding.

[0074] During the process of creating the convoy:

[0075] The broadcast is set with the signature of the lead vehicle and the scalar multiplication point, and the receiving vehicle verifies the signature of the broadcast according to the public key;

[0076] The convoy information table records vehicle ID, convoy ID, vehicle role, vehicle status, open status, and scalar multiplication point list.

[0077] In some embodiments, the process of creating a convoy is as follows:

[0078] The lead vehicle broadcasts a "create convoy" command, puts the scalar multiplication point into the lead vehicle information table. In the V2X scenario, the message is signed, and the public key in the broadcast message is attached in the certificate for verifying the authenticity of the message. At the same time, the scalar multiplication point is put into the lead vehicle information table to form a more flexible way of storing shared information.

[0079] The public key is the product of the private key and the base point on the ECC curve.

[0080] The lead vehicle information table is as follows:

[0081]

[0082] The specific steps are as follows:

[0083] The lead vehicle pre-assigns all vehicle IDs in the convoy for subsequent verification of vehicle IDs;

[0084] The lead vehicle broadcasts a create convoy command. The content includes: vehicle id, information sending time, convoy id, vehicle grouping status as being in the process of grouping, and open status as open;

[0085] The scalar multiplication point information list is a lead vehicle scalar multiplication point.

[0086] The process of joining the convoy includes:

[0087] The joining application is set with a free vehicle scalar multiplication point, and the joining application is signed using the private key of the free vehicle;

[0088] After receiving the joining request, the leading vehicle verifies the legality of the joining request. After passing the verification, it uses the public key to verify the signature. After the verification passes, it updates the scalar multiplication point of the free vehicle to the convoy information table, and updates the vehicle angle of the free vehicle to a following vehicle;

[0089] The following vehicle verifies the legality of the broadcast from the leading vehicle and verifies the signature of the broadcast according to the public key of the leading vehicle in the broadcast. After the verification passes, the operation of joining the convoy is completed.

[0090] In some embodiments, the process of joining the convoy is as follows:

[0091] Free vehicle B sends a command to apply to join the convoy, broadcasts the free vehicle information table, adds its own scalar multiplication point to the table. After the leading vehicle agrees, the leading vehicle updates the leading vehicle information table, adds the free vehicle ID to the joining member list in the leading vehicle information table, (also adds the free vehicle scalar multiplication point). As other vehicles join, the leading vehicle continuously updates the convoy information list. The leading vehicle can close the open state and no longer receive new free vehicles to join.

[0092] The free vehicle information table is as follows:

[0093] Data Remarks Vehicle ID Message sending time Target convoy ID Vehicle role Free vehicle / Following vehicle Vehicle driving status Application to join the convoy / Joining the convoy / Following Scalar multiplication point

Optional

[0094] The specific steps are as follows:

[0095] The free vehicle assembles the free vehicle information table, the vehicle role is free vehicle, the vehicle driving state is applying to join the team, and the scalar multiplication point information uses the certificate scalar multiplication point corresponding to the signature;

[0096] The free vehicle signs the above free vehicle information table using its own private key, and assembles the corresponding scalar multiplication point certificate in the security message;

[0097] The free vehicle broadcasts the security message. The structure of the security message is as follows:

[0098]

[0099] After receiving the security messages of each free vehicle applying to join the team, the leading vehicle first verifies whether the certificate is legal, and then uses the public key in this certificate to verify the security message. After the verification passes, it extracts the corresponding scalar multiplication point information and updates the leading vehicle information table. The message structure of the certificate is as follows:

[0100]

[0101] After all free cars have been added, the pilot car updates the open status in the pilot car information table to closed.

[0102] At this point, the role of all free car information tables is switched to follower cars. First, verify whether the certificate in the safety message sent by the pilot car is legal, and then use the corresponding certificate in the safety message to verify the legitimacy of the pilot car's safety message. The algorithm used is the SM2 algorithm for signature verification.

[0103] After the following vehicle verifies that the safety message broadcast by the pilot vehicle is legitimate, it retrieves the scalar multiplication points of other vehicles in the pilot vehicle information table to prepare for subsequent negotiation calculations.

[0104] In some embodiments, the key negotiation process is as follows:

[0105] All vehicles in the team are added to the member list according to the information table of the pilot vehicle, matched according to the vehicle ID in the broadcast information table of the follower vehicle, verified the certificate, and obtained all scalar multiplication points. According to the key negotiation formula in the previous article, all vehicles will obtain a unified negotiation key KS, split KS, and use the last 16 bytes as the communication key KC.

[0106] The process of encrypted communication includes:

[0107] The pilot car uses the communication key and SM4 algorithm to encrypt the original information, uses the pilot car's private key and SM2 algorithm to sign the encrypted information, and broadcasts the signed information;

[0108] The following vehicle verifies the legitimacy of the broadcast information and uses the public key in the fleet information table to verify the broadcast signature. After the verification is passed, the communication key and SM4 algorithm are used to decrypt the encrypted information to obtain the original information.

[0109] In some embodiments, the process of encrypted communication is as follows:

[0110] The pilot car uses the communication key KC to encrypt and sign the confidential messages it sends, which can solve the problem of multi-device key negotiation and encrypted communication.

[0111] The specific steps are as follows:

[0112] The pilot car uses the communication key KC to encrypt private information based on the SM4 algorithm, and then uses the corresponding certificate based on the SM2 algorithm to sign the encrypted information, and finally assembles it into a secure message and broadcasts it;

[0113] The following vehicle first verifies whether the certificate in the security message is legitimate, and then uses the certificate in it to verify whether the security message is legitimate;

[0114] After verification, use the previously negotiated communication key KC to decrypt the encrypted information based on the SM4 algorithm;

[0115] The process of the following vehicle sending encrypted information is the same as that of the leading vehicle;

[0116] Thus, the encrypted communication process is completed.

[0117] The process of the key update includes:

[0118] The leading vehicle and the following vehicle perform a key negotiation operation via broadcast every 5 minutes to obtain a new communication key;

[0119] When the leading vehicle detects that a free vehicle joins, it updates the information in the vehicle fleet information table and broadcasts the updated vehicle fleet information table, and the following vehicle uses the updated vehicle fleet information table to generate a new communication key.

[0120] In some embodiments, the process of key update is as follows:

[0121] The member list in the leading vehicle information table remains unchanged: Since in the V2X scenario, the vehicle broadcasts itself 10 times per second, broadcasts its own certificate, and then updates the certificate every 5 minutes. This mechanism can be used to perform key negotiation every 5 minutes to complete the key update.

[0122] There are newly added members: The leading vehicle updates the member list in the leading vehicle information table and broadcasts the information. The received members compare it. If it is inconsistent with the previous one, re-negotiation is performed.

[0123] There is a vehicle leaving: The leading vehicle updates the member list in the leading vehicle information table, and then the members, according to the received information table, if it is inconsistent with the originally stored one, re-negotiation is performed.

[0124] This key update mechanism is relatively flexible and convenient without changing the existing business logic implementation.

[0125] The vehicle ID is assigned by the leading vehicle; the vehicle roles include leading vehicle, free vehicle, and following vehicle; the vehicle states include applying to join the team and following; the open states include open teaming and stop teaming.

[0126] In some embodiments, the process of disbanding the vehicle fleet is as follows:

[0127] The leading vehicle broadcasts a request to disband the vehicle fleet, updates the driving status bit in the leading vehicle information table to the disbanded state. After receiving the broadcast information, the following vehicle updates its own information table driving status to the state of leaving the vehicle fleet, and the key status becomes the destroyed state.

[0128] In this way, the entire process of multi-device key negotiation communication encryption and the management of the entire life cycle of the key are completed.

[0129] The above technical solution simultaneously combines the use of a certificate signature to verify the authenticity and integrity of messages, uses a mechanism based on a scalar multiplication point key agreement mechanism to ensure the confidentiality of messages, and a dynamic key update mechanism to ensure the security of communication in multiple aspects.

[0130] The technical effects of the above technical solution are as follows:

[0131] Based on the scalar multiplication point key agreement mechanism

[0132] A mechanism for key agreement between multiple devices can well solve the problems of key generation and efficiency in encrypted communication between multiple devices.

[0133] As shown in the following table:

[0134]

[0135] By comparing the efficiency of obtaining shared keys through the ECDH algorithm one by one for 8 devices and the time efficiency of negotiating shared keys through this solution, the technical effects of the present invention are demonstrated. In addition to the efficiency improvement, this mechanism can be widely applied to the application scenarios of key negotiation among multiple devices, expanding the encrypted application scenarios.

[0136] Re-negotiation dynamic encryption update mechanism:

[0137] The key is re-negotiated every 5 minutes, and when there are new devices joining or devices exiting, the key can be negotiated in a timely manner. This dynamic key update encryption mechanism effectively improves data security, effectively prevents the risk of the key being exposed due to long-term use, and reduces the possibility of brute force cracking.

[0138] Key lifecycle management mechanism based on vehicle status:

[0139] The management of the key is updated in real time according to the status of the vehicle. The key status is divided into an initial state, a key update state, an encryption state, and a destruction state as the fleet disbands. Using this mechanism simplifies key management.

[0140] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the present practical embodiments, and they should all be covered by the scope of the claims and the description of the present invention.

[0141] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A multi-device communication key negotiation method, characterized in that, The method includes: Generating a corresponding private key and a scalar multiplication point for each device, where the scalar multiplication point is the product of the private key and the base point of the elliptic curve; Each device broadcasts its corresponding scalar multiplication point and receives the scalar multiplication points of the other devices. Each device calculates a shared key based on a pairing strategy, using its own private key and the received scalar multiplication points; Performing encrypted communication between the devices using the shared key.

2. The multi-device communication key negotiation method according to claim 1, wherein The pairing strategy is: Setting a security parameter k and generating a prime number p of k bits in length; Generate a cyclic additive group G1 of order p and a cyclic multiplicative group G using the base point P on the elliptic curve, T and obtain two integers a and b; If e: G1 * G1 → G T , then for any g1 ∈ G1 and g2 ∈ G2, we have 3. A multi-device communication key negotiation method based on V2X vehicle formation, applying the multi-device communication key negotiation method according to any one of claims 1-2, characterized in that, The method includes the following steps: Creating a convoy: The lead vehicle broadcasts a convoy creation command and a convoy information table, and updates the lead vehicle information to the convoy information table; Joining the convoy: The free vehicle sends a join application to the lead vehicle via broadcast. The lead vehicle receives the application and updates the free vehicle information to the convoy information table, and the free vehicle becomes a following vehicle; Key negotiation: All vehicles in the convoy obtain the information of the other vehicles in the convoy according to the convoy information table, and calculate a shared key using the multi-device communication key negotiation method, and use the last 16 bytes of the shared key as the communication key; Encrypted communication: The lead vehicle encrypts and signs the information using the communication key and broadcasts it; Key update: When there is a change in the convoy members or the usage duration of the current communication key reaches the replacement threshold, the key is updated according to the content of the current convoy information table; Convoy dissolution: When the convoy needs to be dissolved, the lead vehicle broadcasts a convoy dissolution request, and all vehicles update the convoy information table and destroy the key to complete the convoy dissolution.

4. The multi-device communication key negotiation method based on V2X vehicle formation according to claim 3, wherein, During the process of creating the convoy: The broadcast is set with the signature and scalar multiplication point of the lead vehicle, and the receiving vehicle verifies the signature of the broadcast according to the public key; The convoy information table records vehicle ID, convoy ID, vehicle role, vehicle status, open status, scalar multiplication point list.

5. The multi-device communication key negotiation method based on V2X vehicle formation according to claim 3, wherein The process of joining the convoy includes: The join application is set with the free vehicle scalar multiplication point, and the join application is signed using the free vehicle private key; After receiving the join request, the lead vehicle verifies the legality of the join request. After passing the verification, it verifies the signature using the public key. After passing the verification, it updates the free vehicle scalar multiplication point to the convoy information table and updates the vehicle role of the free vehicle to a following vehicle; The following vehicle verifies the legality of the lead vehicle broadcast and verifies the signature of the broadcast according to the public key of the lead vehicle in the broadcast. After passing the verification, it completes the operation of joining the convoy.

6. The multi-device communication key negotiation method based on V2X vehicle formation according to claim 3, characterized in that The process of encrypted communication includes: The lead vehicle encrypts the original information using the communication key and the SM4 algorithm, signs the encrypted information using the private key of the lead vehicle and the SM2 algorithm, and broadcasts the signed information; The following vehicle verifies the legality of the broadcast information and verifies the signature of the broadcast using the public key in the convoy information table. After passing the verification, it decrypts the encrypted information using the communication key and the SM4 algorithm to obtain the original information.

7. The multi-device communication key negotiation method based on V2X vehicle platooning according to claim 3, wherein, The process of key update includes: The lead vehicle and the following vehicle perform a key negotiation operation via broadcast every 5 minutes to obtain a new communication key; When the lead vehicle detects that a free vehicle has joined, it updates the information in the convoy information table and broadcasts the updated convoy information table, and the following vehicle generates a new communication key using the updated convoy information table.

8. The multi-device communication key negotiation method based on V2X vehicle formation according to claim 4, wherein: The vehicle ID is assigned by the leading vehicle; the vehicle roles include the leading vehicle, the free vehicle, and the following vehicle; the vehicle states include applying to join the team and following; the open states include open team formation and stop team formation.

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