Motorcade group key efficient distribution method based on improved multi-receiver signcryption technology

Abstract

The invention provides a motorcade group key efficient distribution method based on an improved multi-receiver signcryption technology, and belongs to the technical field of car networking safety. The technical problems of low group key distribution efficiency and poor security caused by fast topology change and poor stability in the motorcade ad hoc network are solved. According to the technical scheme, the method comprises the following steps that S1, system public parameters are generated; s2, vehicle registration; s3, carrying out leader vehicle pushing and selection and group key distribution preprocessing; s4, the leader vehicle generates and safely distributes a group key; and S5, other legal vehicles of the motorcade safely obtain the group key. The method has the beneficial effects that in order to solve the problems of efficiency and safety of group key distribution in an Internet of Vehicles fleet environment, a group key generation and distribution algorithm based on an improved multi-receiver signcryption technology is designed, and the problems of safety and efficiency of group key distribution caused by fast topology change and poor stability in a fleet ad hoc network are solved; and the requirement of establishing the safe communication channel of the motorcade is ensured.

Description

Technical Field

[0001] The present invention relates to the field of vehicle networking security technology, and in particular to a method for efficiently distributing a fleet group key based on an improved multi-receiver signcryption technology. Background Art

[0002] As an important part of the intelligent transportation system, the Internet of Vehicles (IOV) is developing rapidly and is widely used in many fields such as intelligent driving and traffic management. In IOV, Vehicular Ad Hoc Networks (VANETs) are an important infrastructure that allows vehicles to achieve efficient information sharing and collaboration without pre-configured infrastructure through self-organizing communication between vehicles. This network architecture has played an important role in improving traffic efficiency, reducing accident rates, and improving driving experience. However, the communication characteristics of VANETs also make it face many security challenges. Since messages between vehicles are transmitted through insecure wireless channels, attackers may tamper with, intercept or delete communication content through means such as message tampering or replay attacks, resulting in user privacy data leakage, communication interruption, and even serious traffic safety accidents. At the same time, the high dynamics of VANETs, ​​namely the frequent movement of vehicles and the rapid changes in network topology, make it difficult to complete security authentication and key exchange in a timely manner, increasing the risk of man-in-the-middle attacks. Frequent connections and disconnections make the network vulnerable to denial of service attacks, affecting the reliability and security of vehicle communications. In addition, the dynamically changing network environment also provides more attack opportunities for malicious nodes, allowing them to exploit vulnerabilities in the network to carry out various security threats.

[0003] In response to the above security issues of the Internet of Vehicles, current solutions usually improve communication security by encrypting transmitted messages. However, how to ensure that all vehicles participating in group communication share the same session key (group key) remains an important research problem. Especially in VANETs, ​​vehicle connections change frequently and some vehicles may be out of the coverage of the roadside unit (RSU), making it impossible to achieve effective authentication and key distribution. At the same time, factors such as limited on-board equipment resources further increase the complexity of group key establishment. If there is a lack of an effective group key establishment mechanism, communication between vehicles may fail due to key asynchrony, and the collaboration efficiency and security within the group are difficult to guarantee. In addition, attackers may maliciously interfere with communications by stealing or forging keys, thereby threatening the security of the entire Internet of Vehicles. Therefore, designing a group key establishment algorithm optimized for the vehicle ad hoc network environment is not only a necessary means to ensure the security of group communications, but also the key to improving communication efficiency and reducing computing and communication overhead.

[0004] The famous Diffie-Hellman key exchange protocol was proposed in the paper "New directions in cryptography", which provides an important theoretical basis for establishing secure session keys in one-to-one communication scenarios. However, this protocol is limited to key generation between two users and cannot meet the needs of multi-user group communication. To solve this problem, various group key generation schemes have been proposed one after another. These schemes can be technically divided into two categories: group key agreement schemes and group key distribution schemes. The core feature of the group key agreement scheme is that all participants in the group work together to generate keys without relying on a trusted third party. Since the Diffie-Hellman protocol was extended to multi-user scenarios in the paper "A conference key distribution system", related research has made significant progress. For example, in the paper “A provably secure cluster-based hybrid hierarchical group key agreement for large wireless ad hoc networks”, a cluster-based hybrid hierarchical group key agreement scheme is proposed, which provides a scalable solution for secure communication in wireless self-organizing networks. In the paper “Anonymous dynamic group authenticated key agreements using physical unclonable functions for internet of medical things”, a lightweight anonymous dynamic group authenticated key agreement scheme is designed, which enables sensor devices in the medical Internet of Things to securely negotiate session keys, and is used to solve the data transmission security problem in the medical Internet of Things. Although the single-round asymmetric group key agreement protocol (Asymmetric Group Key Agreement, ASGKA) has improved negotiation efficiency, it cannot resist active attacks and is only applicable to static groups whose members do not change dynamically. In the paper “Identity-based authenticated asymmetric group key agreement protocol”, an asymmetric group key protocol for the Internet of Vehicles is developed based on blockchain technology, which has certain advantages in security, but does not fully consider the resource-constrained characteristics of the terminal devices of the Internet of Vehicles, and its high computational overhead may lead to insufficient efficiency.

[0005] Although group key agreement schemes can solve the group key generation problem, they have some drawbacks that cannot be ignored. In such schemes, all communicating members need to participate in the key agreement process, which requires each member to perform computing tasks, which may lead to high computing overhead and time delay. At the same time, the frequent interactions between members increase the communication burden, further causing network delay and resource consumption problems. If a member cannot participate in the negotiation for some reason, the entire key generation process may be interrupted. Therefore, the group key agreement scheme is not ideal in VANETs environments with high dynamics and limited computing power.

[0006] In contrast, the group key distribution scheme avoids the above disadvantages by generating keys through a trusted third party called the Group Key Manager (GKM) and distributing them securely to group members. This approach does not require all members to participate in the calculation and avoids frequent interactions between members, thereby effectively reducing the computational and communication overheads and reducing the overall delay. In the paper "Self-healing group key distribution protocol in wireless sensor networks for secure IoT communications", a self-healing group key distribution protocol is proposed to improve the communication security and efficiency of unreliable wireless networks in the Internet of Things; in the paper "A computation-efficient group key distribution protocol based on a new secretsharing scheme", a computationally efficient dynamic group key distribution protocol is designed, which reduces the computational cost by optimizing the algorithm; in the paper "BAGKD: A batch authentication and group key distribution protocol for VANETs", a protocol combining batch message authentication and group key distribution is proposed for VANETs to ensure that each authenticated vehicle can obtain the same group key. Although the scheme improves the efficiency of key management, it relies on the roadside unit (RSU) as the key manager and does not fully consider the constraints of the limited communication range of the RSU. Once the vehicle is out of the RSU coverage, key distribution will be difficult to carry out in real time. In addition, after detecting an illegal vehicle, the scheme fails to provide an effective mechanism to ensure that the group key is only distributed to legal vehicles.

[0007] Based on a thorough investigation of the defects of the current group key distribution related technologies in the fleet environment, this paper proposes an innovative solution that adapts to the communication characteristics of the fleet. The solution uses the multi-receiver signcryption algorithm and online / offline signcryption and other related technologies in cryptography. In order to clearly explain the principles and steps of the present invention, the relevant cryptography background knowledge is first explained:

[0008] (1) Elliptic Curve Cryptography

[0009] Elliptic curve definition: Choose two prime numbers p and q, and choose a, b∈F p , in the finite field F p The elliptic curve E on can be defined as: E:y 2 =x 3 +ax+b(mod p), and Δ=4a 3 +27b 2 ≠0(modp).

[0010] Elliptic curve addition: P = (x1, y1) ∈ E, where P is a point on the elliptic curve E, the symmetric point is -P = (x1, -y1) (modp), Q = (x2, y2) ∈ E, Q ≠ -P. Define a line l passing through P and Q and intersecting the elliptic curve at point R' = (x3, y3), the symmetric point of R' about the x-axis is R = (x3, -y3), then we can define R = P + Q.

[0011] Elliptic curve point multiplication: From the point doubling formula, we can know that P+P+P+…+P=KP. The point multiplication operation in the elliptic curve is also called the point doubling operation. The mathematical description is: Q=kP, where P, Q are points on the elliptic curve, k is an integer, and k cannot be greater than the order of P.

[0012] (2) Related Difficult Problems and Their Assumptions

[0013] Computational Diffie-Hellman (CDH) problem on elliptic curves: In an elliptic curve group G, given the generator P and point Q∈G, and two points aP and bP, the problem of computing abP is called the Computational Diffie-Hellman problem (CDH problem).

[0014] The CDH hypothesis states that for all probabilistic polynomial-time adversaries The probability of successfully calculating abP satisfies: Pr[A(P,aP,bP)=[abP]≤∈, where ∈ is an extremely small probability.

[0015] (3) Formal Definition of Certificateless Multi-recipient Signcryption Scheme

[0016] The certificateless multi-recipient signcryption algorithm designed by the present invention mainly includes four entities: a trusted authority (TA), a key generation center (KGC), a signer (identified as ID s ) and the receiver (identified by ID i ). A complete certificateless multi-recipient signcryption algorithm usually includes five stages, namely: system initialization, vehicle key generation, signcryption, and decryption.

[0017] 1) System Setup: With the system security parameter λ as input, KGC runs this algorithm to obtain the system public parameter params and the system master key. Then, KGC publishes params.

[0018] 2) Vehicle key generation (Set-Private-Key): KGC outputs vehicle V i The vehicle receives a partial private key, verifies the validity of the partial private key, inputs the partial private key, and outputs the complete key.

[0019] 3) Signcryption: The signer takes the private key, public key, recipient public key and the message M to be signed as input, and the vehicle executes the algorithm to obtain the signed ciphertext σ:

[0020] 4) Designcryption: With the signcrypted ciphertext σ, params and the recipient’s private key as input, each recipient runs the algorithm to obtain the plaintext message M. Summary of the invention

[0021] In view of the above-mentioned technical problems, the present invention provides a method for efficiently distributing fleet group keys based on improved multi-receiver signcryption technology.

[0022] The inventive concept of the present invention is: comprehensively consider the two elements of security and efficiency, respond to the anonymous, efficient, secure and recipient-specified group key distribution requirements in the fleet environment, adopt a certificateless signcryption scheme based on the elliptic curve cryptography system, solve the public key certificate management or user key escrow problem, and use a pseudonym mechanism to protect the true identity of both parties in communication. The certificateless multi-receiver signcryption technology is innovatively introduced into the group key distribution in the fleet scenario. Through this technology, the encryption and distribution of the group key are efficiently realized in one signcryption operation, which significantly reduces the communication and computing overhead. The present invention fully considers the characteristics of the limited communication range of RSU in the vehicle network fleet environment, adopts the leader vehicle as the group key manager (Group Key Manager, GKM), has the need to quickly respond to the dynamic joining or leaving of the vehicle fleet, combines the online / offline signature technology with the certificateless multi-receiver signcryption scheme, and reduces the encryption calculation burden required in the online stage through the pre-calculation method in the offline stage, significantly improving the overall efficiency of the group key distribution. The specific implementation steps are given below.

[0023] For ease of understanding, the symbols and their meanings involved in the present invention are first given as shown in the following table:

[0024]

[0025] The present invention is achieved by the following measures: A method for efficiently distributing a fleet group key based on an improved multi-receiver signcryption technology, comprising the following steps:

[0026] S1. Generate system common parameters;

[0027] S2. Vehicle registration;

[0028] S3, leader vehicle selection and group key distribution preprocessing;

[0029] S4, the leader vehicle generates and securely distributes the group key;

[0030] S5. Other legal vehicles in the fleet safely obtain the group key.

[0031] Furthermore, the S1 step includes:

[0032] S11. Input security parameter λ, and the Key Generation Center (KGC) generates two prime numbers p and q, and p In, select parameters a, b to generate elliptic curve E: y 2 =x 3 +ax+b(mod p), where Δ=4a 3 +27b 2 ≠0(mod p);

[0033] S12, KGC multiplication group modulo prime number p In the example, a random number s is selected as the master private key, and the master public key P is calculated based on the doubling operation of the elliptic curve. pub =s·P;

[0034] S13. Select four secure hash functions:

[0035] H1:

[0036] H2:

[0037] H3:

[0038] H4:

[0039] S14, public system parameters params = {P pub ,H1,H2,H3,H4}.

[0040] Furthermore, the S2 step includes:

[0041] S21. Real identity is ID i Vehicle V i Random Selection i ∈Z p * , calculate the partial pseudonym PID i 1 =γ i ·P, V i The identity information M1 = {ID i ,PID i 1}Transmit to the trusted authority TA;

[0042] S22. The trusted institution TA receives the vehicle V i After obtaining the identity information M1, select a random number α∈Z p * , calculate the public key P TA =α·P. At the same time, V i Another part of the pseudonym:

[0043] S23, the trusted institution TA sends the vehicle's complete pseudonym PID i ={PID i 1 ,PID i 2}Sent to vehicle V via secure channel i .

[0044] S24, Vehicle Vi Choose a random number x i ∈Z p * As a secret value, calculate X i =x i P, then the full pseudonym PID i and X i Send to KGC via secure channel;

[0045] S25, KGC for vehicle V i Generate partial private key psk i ;

[0046] S251, KGC receives PID i and X i Then, first calculate u i =H1(PID i ,X i ,s), then calculate the vehicle V i Part of the private key y i =s·u i , and then calculate

[0047] S252, KGC will part of the private key y i and K i Sent to vehicle V via secure channel i ;

[0048] S26, the vehicle verifies the validity of the partial private key and generates a complete key;

[0049] S261, Vehicle V i Received partial private key y i and K i After that, the partial private key is verified by: If the equation y i ·K i = =P pub If established, then some private keys are valid;

[0050] S262, Vehicle V i The complete private key is composed of sk i ={x i ,y i}, the public key is X i .

[0051] Furthermore, the S3 step includes:

[0052] S31. Select the team leader vehicle;

[0053] S311, when the vehicle enters the effective communication range of the road side unit RSU (Road Side Unit), after the identity legitimacy authentication, the RSU dynamically generates a legal vehicle set List = {element1, element2, ..., element n}, each element in the collection contains the pseudonym and public key information of the legal vehicle;

[0054] S312, Legal Vehicle V i Send resource information to RSU i ={PID i ,X i ,Loc i ,C i ,Comp i ,B i}, where PID i Indicates vehicle pseudonym, X i Indicates public key information, Loc i Indicates location information, C i Indicates available bandwidth resources, Comp i represents computing resources, B i Indicates battery status;

[0055] S313, RSU receives vehicle V i Source i After that, the vehicle V i To perform a performance evaluation:

[0056] 1. Calculate vehicle V i Distance to RSU: Where P t is the vehicle’s transmission power, G t is the transmitting antenna gain, G r is the receiving antenna gain, RSSI is the received signal strength, and α is the distance attenuation factor;

[0057] 2. Calculate vehicle V i Communication capabilities: Among them C i is the available bandwidth resource of the vehicle, C max It is the largest available bandwidth resource within the fleet;

[0058] 3. Evaluate computing resource advantages: Among themComp i is the computing resource of the current vehicle, Comp max It is the largest computing resource for the fleet;

[0059] 4. Advantages of calculating battery status: Among them Bi is the battery capacity of the vehicle, B max The largest battery capacity in the fleet;

[0060] 5. Calculate vehicle V i Overall performance score Where: w1+w2+w3+w4=1;

[0061] S314, RSU selects the vehicle with the highest score as the leader vehicle V s ;

[0062] S315, RSU will other legal vehicles in the fleet V j The public key X j Sent to leader vehicle V s , and broadcast the election results;

[0063] S316, RSU periodically updates C based on the resource information of the newly certified vehicle max 、Comp max and B max The comprehensive score of each vehicle is recalculated according to step S313, and the leader vehicle is updated to timely adapt to the dynamic changes of the team, ensuring that the vehicle with the highest score in the team can serve as the leader;

[0064] S32, the leader vehicle performs offline preprocessing for group key generation;

[0065] S321, Team Leader Vehicle V s Choose a random number r∈Z p * , calculate R = rP, L j =ry j X j and α j =H2(R,L j );

[0066] S322, Team Leader Vehicle V s Randomly choose a number θ∈Z p * , construct an n-order polynomial: where a j ∈Z p * ;

[0067] S323, Team Leader Vehicle V s Pre-generate offline ciphertext σ off =(R,L j ,θ,a n-1 ,...,a1,a0).

[0068] Furthermore, the S4 step includes:

[0069] S41, Team Leader Vehicle V s Generate the signcrypted ciphertext σ=(Z,R,h,a n-1 ,...,a1,a0);

[0070] S411, Team Leader Vehicle V s Generate the group key K using a secure random number generator (CSPRNG) g , which is 256 bits long and can provide security equivalent to 128-bit symmetric encryption, in line with current mainstream cryptography standards (such as NIST SP800-57). The randomness of the group key is guaranteed by CSPRNG to ensure its unpredictability, thereby avoiding malicious speculation or reproduction;

[0071] S412, Team Leader Vehicle V s Calculate and generate the symmetric encryption key t=H3(θ,R);

[0072] S413, Team Leader Vehicle V s Select the secure AES-128 symmetric encryption function Enc(), use the key t, and encrypt the group key K g Encrypt and obtain the ciphertext Z=Enc t (K g );

[0073] S414, Team Leader Vehicle V s Execute hash calculation and obtain h = H4 (PID s ,K g ,R,θ,a n-1 ,...,a1,a0);

[0074] S415, Team Leader Vehicle V s Generate the signcrypted ciphertext σ=(Z,R,h,a n-1 ,...,a1,a0), and broadcast the signature σ to other vehicles in the team.

[0075] Furthermore, the step S5 includes:

[0076] S51、Other legally received vehicles in the fleet V j Decrypt the signcryption to obtain the group key K g ;

[0077] S511、Legal acceptance of vehicles within the fleet V j Calculate L j =y j x j R, the correctness proof is:

[0078]

[0079] S512, legally receiving vehicle V j Calculate α j =H2(R,L j ), using the coefficient a in σ n-1 ,...,a1,a0 restore n-order polynomial

[0080]

[0081] S513, legally receiving vehicle V j Calculate θ = f(α j ) and t = H3(θ,R);

[0082] S514, legally receiving vehicle V j Decrypt the ciphertext Z using the key t and the AES-128 symmetric decryption function Dec() to obtain the group key K g =Dec t (Z);

[0083] S515, legally receiving vehicle V j Execute hash calculation and obtain h′=H4(PID s ,K g ,R,θ,a n-1 ,...,a1,a0), and verify whether the equation h′=h holds. If it holds, extract the group key K g ; Otherwise, return the termination symbol ⊥.

[0084] Compared with the prior art, the present invention has the following beneficial effects:

[0085] (1) The present invention provides an efficient method for distributing fleet group keys based on improved multi-receiver signcryption technology, designs a group key distribution mechanism based on multi-receiver signcryption technology, and innovatively introduces this technology into the group key distribution in the fleet scenario. Through the multi-receiver signcryption technology, the encryption and distribution of the group key are efficiently realized in one signcryption operation, which significantly reduces the communication and computing overhead. This solution fully considers the characteristics of the limited communication range of RSU in the vehicle network fleet environment, adopts the leader vehicle as the group key manager (GKM), and has the ability to quickly respond to the needs of vehicles dynamically joining or leaving the fleet, significantly improving the overall efficiency of group key distribution.

[0086] (2) The present invention provides an efficient method for distributing fleet group keys based on improved multi-receiver signcryption technology, which combines online / offline signature technology with a certificateless multi-receiver signcryption scheme. Through pre-calculation in the offline phase, the efficiency of group key distribution is greatly improved, while reducing the encryption calculation burden required in the online phase. At the same time, a pseudonym mechanism is introduced to implement conditional privacy protection to ensure user privacy security. A comprehensive security analysis and security proof are carried out under the random oracle model (ROM), which effectively resists various attack scenarios and ensures the confidentiality and unforgeability of the group key distribution process.

[0087] (3) The present invention provides an efficient method for distributing group keys of a fleet based on an improved multi-receiver signcryption technology. Performance analysis shows that the scheme has advantages over other schemes in terms of security, computational complexity, and communication overhead. The scheme not only meets multiple security requirements such as confidentiality of group keys, unforgeability of group keys, identity anonymity, traceability of real identities, unlinkability of pseudonyms, and elimination of key escrow, but also has low computational and communication overhead, reflecting high performance and practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0088] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. They are used to explain the present invention together with the embodiments of the present invention and do not constitute a limitation of the present invention.

[0089] Figure 1 The present invention provides an overall flow chart of a method for efficiently distributing fleet group keys based on an improved multi-receiver signcryption technology.

[0090] Figure 2 Schematic diagram of the system architecture of the present invention.

[0091] Figure 3 A framework diagram of an efficient method for distributing fleet group keys based on an improved multi-receiver signcryption technology provided by the present invention.

[0092] Figure 4 A comparison chart of the computational overhead of the signcryption phase as the number of receivers increases provided by the present invention.

[0093] Figure 5 A comparison chart of the total computational overhead as the number of receivers increases provided by the present invention. DETAILED DESCRIPTION

[0094] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. Of course, the specific embodiments described here are only used to explain the present invention and are not used to limit the present invention.

[0095] Example 1

[0096] This embodiment 1 provides a method for efficiently distributing fleet group keys based on an improved multi-receiver signcryption technology. Figure 1 As shown, the following steps are included:

[0097] S1. Generate system common parameters;

[0098] S2. Vehicle registration;

[0099] S3, leader vehicle selection and group key distribution preprocessing;

[0100] S4, the leader vehicle generates and securely distributes the group key;

[0101] S5. Other legal vehicles in the fleet safely obtain the group key.

[0102] like Figure 2 As shown, the vehicle network architecture in the group key distribution method based on the improved multi-receiver signcryption includes: a trusted authentication center (TA), a roadside infrastructure (RSU) and an on-board unit (OBU).

[0103] like Figure 3 As shown, the specific contents of S1 include the following steps:

[0104] S11. Input security parameter λ, and the Key Generation Center (KGC) generates two prime numbers p and q, and p In, select parameters a, b to generate elliptic curve E: y 2 =x 3 +ax+b(mod p), where Δ=4a 3 +27b 2 ≠0(mod p);

[0105] S12, KGC multiplication group modulo prime number p In the example, a random number s is selected as the master private key, and the master public key P is calculated based on the doubling operation of the elliptic curve. pub =s·P;

[0106] S13. Select four secure hash functions:

[0107] H1:

[0108] H2:

[0109] H3:

[0110] H4:

[0111] S14, public system parameters params = {P pub ,H1,H2,H3,H4}.

[0112] like Figure 3 As shown, the specific contents of S2 include the following steps:

[0113] S21. Real identity is ID i Vehicle V i Random Selection i ∈Z p * , calculate the partial pseudonym PID i 1 =γ i ·P, V i The identity information M1 = {ID i ,PID i 1}Transmit to the trusted authority TA;

[0114] S22. The trusted institution TA receives the vehicle V i After obtaining the identity information M1, select a random number α∈Z p * , calculate the public key P TA =α·P. At the same time, V i Another part of the pseudonym:

[0115] S23, the trusted institution TA sends the vehicle's complete pseudonym PID i ={PID i 1 ,PID i 2}Sent to vehicle V via secure channel i .

[0116] S24, Vehicle V i Choose a random number x i ∈Z p * As a secret value, calculate X i =x i P, then the full pseudonym PID i and X i Send to KGC via secure channel;

[0117] S25, KGC for vehicle V i Generate partial private key psk i ;

[0118] S251, KGC receives PID i and X i Then, first calculate ui =H1(PID i ,X i ,s), then calculate the vehicle V i Part of the private key y i =s·u i , and then calculate

[0119] S252, KGC will part of the private key y i and K i Sent to vehicle V via secure channel i ;

[0120] S26, the vehicle verifies the validity of the partial private key and generates a complete key;

[0121] S261, Vehicle V i Received partial private key y i and K i After that, the partial private key is verified by: If the equation y i ·K i = =P pub If established, then some private keys are valid;

[0122] S262, Vehicle V i The complete private key is composed of sk i ={x i ,y i}, the public key is X i .

[0123] like Figure 3 As shown, the specific contents of S3 include the following steps:

[0124] S31. Select the team leader vehicle;

[0125] S311, when the vehicle enters the effective communication range of the road side unit RSU (Road Side Unit), after the identity legitimacy authentication, the RSU dynamically generates a legal vehicle set List = {element1, element2, ..., element n}, each element in the collection contains the pseudonym and public key information of the legal vehicle;

[0126] S312, Legal Vehicle V i Send resource information to RSU i ={PID i ,X i ,Loc i ,C i ,Comp i ,B i}, where PIDi Indicates vehicle pseudonym, X i Indicates public key information, Loc i Indicates location information, C i Indicates available bandwidth resources, Comp i represents computing resources, B i Indicates battery status;

[0127] S313, RSU receives vehicle V i Source i After that, the vehicle V i To perform a performance evaluation:

[0128] 1. Calculate vehicle V i Distance to RSU: Where P t is the vehicle’s transmission power, G t is the transmitting antenna gain, G r is the receiving antenna gain, RSSI is the received signal strength, and α is the distance attenuation factor;

[0129] 2. Calculate vehicle V i Communication capabilities: Among them C i is the available bandwidth resource of the vehicle, C max It is the largest available bandwidth resource within the fleet;

[0130] 3. Evaluate computing resource advantages: Among themComp i is the computing resource of the current vehicle, Comp max It is the largest computing resource for the fleet;

[0131] 4. Advantages of calculating battery status: Among them B i is the battery capacity of the vehicle, B max The largest battery capacity in the fleet;

[0132] 5. Calculate vehicle V i Overall performance score Where: w1+w2+w3+w4=1;

[0133] S314, RSU selects the vehicle with the highest score as the leader vehicle V s ;

[0134] S315, RSU will be other legal vehicles in the fleet V j The public key X j Sent to leader vehicle V s , and broadcast the election results;

[0135] S316, RSU periodically updates C based on the resource information of the newly certified vehicle max 、Comp max and B max The comprehensive score of each vehicle is recalculated according to step S313, and the leader vehicle is updated to timely adapt to the dynamic changes of the team, ensuring that the vehicle with the highest score in the team can serve as the leader;

[0136] S32, the leader vehicle performs offline preprocessing for group key generation;

[0137] S321, Team Leader Vehicle V s Choose a random number r∈Z p * , calculate R = rP, L j =ry j X j and α j =H2(R,L j );

[0138] S322, Team Leader Vehicle V s Randomly choose a number θ∈Z p * , construct an n-order polynomial: where a j ∈Z p * ;

[0139] S323, Team Leader Vehicle V s Pre-generate offline ciphertext σ off =(R,L j ,θ,a n-1 ,...,a1,a0).

[0140] like Figure 3 As shown, the specific contents of S4 include the following steps:

[0141] S41, Team Leader Vehicle V s Generate the signcrypted ciphertext σ=(Z,R,h,a n-1 ,...,a1,a0);

[0142] S411, Team Leader Vehicle V s Generate the group key K using a secure random number generator (CSPRNG) g , which is 256 bits long and can provide security equivalent to 128-bit symmetric encryption, in line with current mainstream cryptography standards (such as NIST SP800-57). The randomness of the group key is guaranteed by CSPRNG to ensure its unpredictability, thereby avoiding malicious speculation or reproduction;

[0143] S412, Team Leader Vehicle Vs Calculate and generate the symmetric encryption key t=H3(θ,R);

[0144] S413, Team Leader Vehicle V s Select the secure AES-128 symmetric encryption function Enc(), use the key t, and encrypt the group key K g Encrypt and obtain the ciphertext Z=Enc t (K g );

[0145] S414, Team Leader Vehicle V s Execute hash calculation and obtain h = H4 (PID s ,K g ,R,θ,a n-1 ,...,a1,a0);

[0146] S415, Team Leader Vehicle V s Generate the signcrypted ciphertext σ=(Z,R,h,a n-1 ,...,a1,a0), and broadcast the signature σ to other vehicles in the team.

[0147] like Figure 3 As shown, the specific contents of S5 include the following steps:

[0148] S51、Other legally received vehicles in the fleet V j Decrypt the signcryption to obtain the group key K g ;

[0149] S511、Legal acceptance of vehicles within the fleet V j Calculate L j =y j x j R, the correctness proof is:

[0150]

[0151] S512, legally receiving vehicle V j Calculate α j =H2(R,L j ), using the coefficient a in σ n-1 ,...,a1,a0 restore n-order polynomial

[0152] S513, legally receiving vehicle V j Calculate θ = f(α j ) and t = H3(θ,R);

[0153] S514, legally receiving vehicle V j Decrypt the ciphertext Z using the key t and the AES-128 symmetric decryption function Dec() to obtain the group key Kg =Dec t (Z);

[0154] S515, legally receiving vehicle V j Execute hash calculation to obtain h′=H4(PID s ,K g ,R,θ,a n-1 ,...,a1,a0), and verify whether the equation h′=h holds. If it holds, extract the group key K g ; Otherwise, return the termination symbol ⊥.

[0155] In order to verify the feasibility of the present invention, the security of this embodiment 1 is analyzed:

[0156] Security goals and attack models:

[0157] 1. The security objectives of the program are as follows:

[0158] a) Confidentiality and unforgeability: Ensure that it is computationally infeasible for an attacker to obtain any plaintext information from a ciphertext during the group key distribution phase, and be able to check whether the group key has been forged or tampered with.

[0159] b) Conditional privacy protection: Under normal communication conditions, the Internet of Vehicles needs to provide anonymous privacy protection to protect the personal privacy information of vehicle users and ensure that attackers cannot obtain personal privacy information from intercepted messages. However, when a malicious vehicle exhibits illegal behavior, the trusted institution TA can promptly trace and revoke the real identity of the vehicle to prevent it from continuing to endanger system security.

[0160] c) Unlinkability of pseudonyms: The pseudonyms generated by the trusted authority TA for each vehicle need to be unrelated to each other, ensuring the forward and backward security of the pseudonyms. This makes it impossible for an attacker to infer other pseudonyms from the current pseudonym.

[0161] 2. The attack model is defined as follows:

[0162] In the security model of certificateless multi-recipient signcryption scheme, two types of attackers are considered: type 1 attacker A1 and type 2 attacker A2.

[0163] Type 1 attacker (A1): Attacker A1 simulates a malicious user and is a malicious user who can replace the user's public key, but he / she does not know the system's master key.

[0164] Type 2 attacker (A2): Attacker A2 simulates the situation of a malicious KGC. He / she knows the system's master key, but is not allowed to replace the user's public key.

[0165] Security Analysis:

[0166] Lemma 1: This embodiment can achieve confidentiality protection for the group key.

[0167] Proof in Type 1 attacker Under the attack, in polynomial time, if the attacker does not have a non-negligible probability to win the following game, then there exists an algorithm B that can solve the DL hard problem in polynomial time with at least a non-negligible probability. The proof process is as follows: Algorithm B is a solver of the CDH hard problem, the goal is to win the following game in polynomial time.<P,aP,bP> ,in, And calculate abP when unknown. Algorithm B takes the adversary is a subroutine and acts as the challenger of the game. When the game starts, B runs the system initialization algorithm and sends params to Maintenance list L1, L2, L3, L4, L C Used to track the adversary In the queries to the oracles H1, H2, H3, H4 and the query to create a user, the lists are initially empty.

[0168] Ask: Rival Perform the following polynomial bounded query

[0169] H1 query: When receiving the adversary Inquiries about H1 <PID k ,X k ,s>, if there is <PID k ,X k ,s,u k >, then return u k Give Otherwise, B randomly selects Adding Tuples <PID k ,X k ,s,u k > to L1 and return to u k

[0170] H2 query: When receiving the adversary Inquiries to H2 <PID k ,R k ,L k >, if L2 exists <PID k ,R k ,L k ,α k >, then return α k Give Otherwise, B randomly selects Adding Tuples <PID k ,R k ,L k ,αk > into L2, and return α k Give

[0171] H3 query: When B receives the adversary Inquiry to H3 <PID k ,θ k ,R k >, if L3 exists <PID k ,θ k ,R k ,t k >, then return t k Give Otherwise, B randomly selects Adding Tuples <PID k ,θ k ,R k ,t k > to L3 and return to t k Give

[0172] H4 query: When B receives the adversary Inquiries about H4 <PID k ,K g ,R k ,θ k ,a n-1 ,...,a1,a0>, if L4 exists <PID k ,K g ,R k ,θ k ,a n-1 ,...,a1,a0,h k >, then return h k Give Otherwise, B randomly selects Adding Tuples <PID k ,K g ,R k ,θ k ,a n-1 ,...,a1,a0> to L4 and return h k Give

[0173] Phase 1: Ask B a question, and B responds according to the situation:

[0174] Create a user query: Request a query to B. After receiving the request, B checks the tuple <PID k ,(x k ,y k ),X k> Is it in list L C If yes, B keeps the tuple. Otherwise, B does the following:

[0175] If PID i =PID k , B randomly selects Setting sk k = <x k ,⊥>,X k =x k P, and update the list L C Tuples in <PID k ,(x k ,⊥),X k > and the tuple in L1 <PID k ,X k ,s,u i >.

[0176] If PID i ≠PID k , B randomly selects Setting sk k = <x k ,y k >, X k =x k P, and update the list L C Tuples in <PID k ,(x k ,y k ),X k > and the tuple in L1 <PID k ,X k ,s,u i >.

[0177] Set secret value query: When B receives PID i When asked to set a secret value, if it exists <PID k ,(x k ,y k ),X k >, then return x k Give Otherwise, B requests to create a user query to obtain <PID k ,(x k ,y k ),X k >, then x k Return to

[0178] Partial private key extraction query: When B receives PID kWhen asked for a partial private key, B responds as follows:

[0179] 1) If PID i =PID k , then B stops executing the protocol.

[0180] 2) If PID i ≠PID k , B checks the tuple <PID k ,(x k ,y k ),X k > Is it in list L C If yes, then B will k Return to Otherwise, B requests to create a user query to obtain <PID k ,(x k ,y k ),X k >, then y k Return to

[0181] Set public key query: When B receives PID k When querying the public key, B checks the tuple <PID k ,(x k ,y k ),X k > Is it in list L C If so, then B will X k Return to Otherwise, B requests to create a user query to obtain <PID k ,(x k ,y k ),X k >, then X k Return to

[0182] Set private key query: When B receives PID k When B queries for the private key, B responds as follows:

[0183] 1) If PID i =PID k , then B stops executing the protocol.

[0184] 2) If PID i ≠PID k , B checks the tuple <PID k ,(x k ,y k ),Xk > Is it in list L C If so, then B will sk k =(x k ,y k )Return to Otherwise, B requests to create a user query to obtain <PID k ,(x k ,y k ),X k >, then sk k =(x k ,y k )Return to

[0185] Public key replacement query: for PID k , You can choose any new public key X k 'Replace the original public key X k , and update the list L C Tuples in <PID k ,(x k ,y k ),X k >.

[0186] Signcryption query: Choose the group key K g and identity PID k Request a signcryption query from B. After B receives the query, B checks the tuple <PID k ,(x k ,y k ),X k > Is it in list L C If yes, B performs the following steps to generate the ciphertext σ * Otherwise, B executes the create user query to obtain the private key sk S and public key X S , and then perform the following steps to generate the ciphertext σ * :

[0187] (a) Select a random number r∈Z p * , calculate R=rP.

[0188] (b) Calculate L i =ry i X i .

[0189] (c) Calculation of α i =H2(R,L i ).

[0190] (d) Randomly select a number θ∈Zp * , construct an n-order polynomial: where a i ∈Z p * .

[0191] (e) Calculate h = H4 (PID s ,K g ,R,θ,a n-1 ,...,a1,a0)

[0192] (f) Generate the signcryption σ=(Z,R,h,a n-1 ,...,a1,a0) is returned to

[0193] Decryption query: Construct ciphertext σ=(Z,R,h,a n-1 ,...,a1,a0) and select a set of receivers {PID1,PID2,…,PID n}, and then send them to B, requesting a decryption query. After receiving the query, B performs the following operations:

[0194] 1) Search for the tuple in list L4 <PID k ,K g ,R k ,θ k ,a n-1 ,...,a1,a0,h k >, if there is no such tuple, B outputs failure and terminates the game. Otherwise, B obtains the group key K from the tuple g ;

[0195] 2) Search in list L2 <PID k ,R k ,L k ,α k >, and set the polynomial

[0196] 3) Search in list L1 <PID k ,X k ,s,u k >, if there is no such tuple, B outputs failure and terminates the game. Otherwise, B obtains <PID k ,X k ,s>;

[0197] 4) Search in list L2 <PID k ,R k ,L k ,α k > and check <R k,L k >Whether it is a tuple;

[0198] 5) Calculate θ′=f(α i ) and t′=H3(θ,R), and obtain the group key K g ′=Dec t (Z).

[0199] 6) Test equation K g ′=K g Is it true? If so, B will K g Return to Otherwise, return failure and terminate the game.

[0200] Challenge: Rival Choose a pair of challenge messages of equal length And send it to B. B randomly selects β∈{0,1} and uses the selected plaintext Calculate the final signcryption σ * , as shown below:

[0201] Calculate R = b·P, V i =b(X i +P pub ) and α i =H2(R,L i );

[0202] Randomly choose θ∈Z p * , construct an n-order polynomial: where a i ∈Z p * ;

[0203] Calculate t = H3 (θ, R), Z = Enc t (K g ), h=H4(PID s ,K g ,R,θ,a n-1 ,...,a1,a0);

[0204] The ciphertext σ=(Z,R,h,a n-1 ,...,a1,a0) is returned to

[0205] Phase 2: B is required to perform a series of queries as described in Phase 1, but cannot perform secret value queries, partial private key extraction queries, private key setting queries, and signcryption decryption queries on users whose public keys have been replaced.

[0206] guess: Guess β′∈{0,1}. If β′=β, then To win the game, B outputs abP=V i -K is used as the solution for CDH. Otherwise, B fails.

[0207] Through the above steps, if the opponent If the confidentiality of this scheme is broken with a non-negligible probability, then B can at least output a valid solution to the CDH difficulty problem with a non-negligible probability. The proof is complete.

[0208] Lemma 2: This embodiment can achieve unforgeability protection for the group key, and the proof method is similar to the above proof.

[0209] Theorem 1 This embodiment can achieve conditional privacy protection of the vehicle.

[0210] Prove that the trusted institution TA in this scheme can track the real identity of the malicious vehicle sender. The method is: submit the pseudonym PID i =(PID i 1 ,PID i 2 ) after which the trusted institution TA can Track the vehicle's real ID i Therefore, the scheme satisfies the conditional privacy protection, and the proof is complete.

[0211] Theorem 2 This embodiment can achieve the unlinkability of member vehicle pseudonyms.

[0212] When the vehicle generates a PID, the trusted institution TA will generate a timestamp Tur for each vehicle. Based on the anti-collision property of the secure hash function, the generated pseudonyms are not related to each other. Therefore, the scheme provides unlinkability between pseudonyms. The proof is complete.

[0213] Example 2

[0214] To verify the feasibility of the present invention, Example 2 compares the functionality and feasibility of the present invention with other multi-recipient signcryption schemes, including Scheme 1 proposed by Yang et al. in An efficient identity-based aggregate signcryption scheme with blockchain for IoT-enabled maritime transportation system,

[0215] This paper analyzes Scheme 2 proposed in "Privacy-preserving aggregation-authentication scheme for safety warning system in fog-cloud based VANET", Scheme 3 proposed by Deng et al. in "Anonymous certificateless multi-receiver en-cryption scheme for smart community management systems", Scheme 4 proposed by Wang et al. in "Multi-receiver signcryption scheme with multiple key generation centers through public channel in edge computing", and Scheme 5 proposed by Wang Lipeng et al. in "Multi-receiver multi-message signcryption scheme using blockchain".

[0216] 1. Functional comparison

[0217] Functional comparison includes: whether the sender anonymity is supported, whether the receiver anonymity is supported, and whether it is traceable:

[0218]

[0219] All the schemes studied support receiver anonymity, but only schemes 1 and 3 fail to achieve sender anonymity. Specifically, scheme 1 is an identity-based cryptographic system, which has a key escrow problem at its core and is difficult to avoid single-point trust risks. Schemes 2 to 4 and this embodiment are all based on certificateless cryptographic systems, which successfully avoid the certificate management and key escrow problems in traditional schemes. However, scheme 3 relies on bilinear pairings as its theoretical basis, and its computational complexity is significantly higher than that of schemes based on elliptic curves.

[0220] In terms of functional implementation, Schemes 2 to 4 and this embodiment all have the traceability of the sender, but Scheme 2 cannot support the one-to-many communication mode of multi-receiver signcryption. In contrast, this embodiment can not only achieve the anonymity of the sender and receiver, but also show superior performance in reducing user communication and computing overhead.

[0221] 2. Performance Analysis

[0222] (1) Computational Cost Analysis and Comparison

[0223] 1) Relevant preparation

[0224] The experiment uses the general cryptographic library MIRACL and the cryptographic library PBC based on bilinear mapping pairs. The experimental environment is as follows: Windows 11 operating system, i7-10700 2.90GHz processor and 16GB memory. The average value of 50 experiments is taken as the final result, and the results are shown in the following table:

[0225]

[0226]

[0227] 2) Comparison and analysis

[0228] The following table shows the comparison of each stage and total time cost of this embodiment and solutions 3-5.

[0229]

[0230] The above is an analysis of the various stages and total time costs of Schemes 3-5 and this embodiment, where n represents the number of receivers. By comparison, it can be seen that the signcryption of this embodiment requires n elliptic curve multiplication operations, while the decryption only requires one elliptic curve multiplication operation, with a total time cost of (1.073+1.073)ms. The same is true for other similar schemes. In Scheme 3, the signcryption requires (2n+3)T m Multiplication operations and n bilinear pairing operations are required, and the total cost of the signcryption phase is (3.293n+0.111)ms. Decryption requires 1 multiplication operation and 1 bilinear pairing operation, and the total cost of the decryption phase is T m +T b =3.256ms, and the total time cost is approximately (3.293n+3.367)ms. In Scheme 4, the signcryption requires 2n+1 elliptic multiplication operations and n multiplication operations, and the total cost of the signcryption stage is (2n+1)T pm +nT m =(2.183n+1.073)ms, decryption requires 4 elliptic curve multiplication operations, and the total time cost is about (2.183n+5.365)ms. In scheme 5, signcryption requires 2n+1 elliptic curve multiplication operations, decryption requires 7 elliptic curve multiplication operations, and the total time cost is about (2.146n+8.584)ms.

[0231] In summary, the number of operations in the decryption phase of each scheme is a constant value, but the computational complexity of the signcryption phase will change with the increase of the number of receivers n. The signcryption time and the total time cost are proportional to the growth of n, where the smaller the coefficient of n, the lower the time cost. Compared with other schemes, this embodiment shows the best performance in terms of time overhead and total time cost in the signcryption phase, and has significant advantages.

[0232] Figure 4 It is a comparison of the time overhead required by the sender in the signcryption process as the number of receivers increases in each scheme. As can be seen from the figure, the signcryption time increases with the increase in the number of receivers. The calculation time of scheme 4 and scheme 5 in the signcryption stage is very close, and because scheme 3 uses bilinear pairing operation in the signcryption stage, the calculation time increases more significantly than other schemes, but the time of the embodiment is significantly lower than that of other schemes.

[0233] Figure 5 It is a comparison of the total time overhead required for each scheme in the total time stage as the number of receivers increases. The total time is the sum of the calculation time of the signcryption stage and the calculation time of the decryption stage. It can be seen from Table 5 that the calculation time of all schemes in the decryption stage is constant, and the required time will not increase with the increase in the number of receivers. The decryption time of schemes 3-5 and this embodiment is 3.256ms, 4.292ms, 7.511ms and 1.073ms respectively. The time required for this embodiment is still the least. The total time of each scheme shows an increasing trend, but the total time overhead of this embodiment is significantly less than that of other schemes. In summary, the experimental results show that this embodiment has certain advantages not only in the signcryption stage, the decryption stage but also in the comparison of the total time.

[0234] The above two embodiments fully verify the feasibility and security of the present invention. At the same time, the performance comparison with other existing multi-receiver signcryption schemes fully illustrates the innovation and performance superiority of the present scheme.

[0235] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An efficient distribution method of fleet group key based on improved multi-receiver signcryption technology, characterized in that: The steps include: S1. Generate system common parameters; S2. Vehicle registration; S3, leader vehicle selection and group key distribution preprocessing; S4, the leader vehicle generates and securely distributes the group key; S5. Other legal vehicles in the fleet safely obtain the group key.

2. The method for efficiently distributing fleet group keys based on improved multi-receiver signcryption technology according to claim 1 is characterized in that: The S1 step includes the following steps: S11. Input security parameter λ, the key generation center generates two prime numbers p and q, and p Select parameters a, b to generate elliptic curve E: y 2 =x 3 +ax+b(mod p), must satisfy Δ=4a 3 +27b 2 ≠0(modp); S12, KGC multiplication group modulo prime number p In the example, a random number s is selected as the master private key, and the master public key P is calculated based on the doubling operation of the elliptic curve. pub =s·P; S13. Select four secure hash functions: S14, KGC public system parameters params = {P pub ,H1,H2,H3,H4}.

3. The method for efficiently distributing fleet group keys based on improved multi-receiver signcryption technology according to claim 1 is characterized in that: The S2 step includes the following steps: S21. Real identity is ID i Vehicle V i Random Selection i ∈Z p * , calculate the partial pseudonym PID i 1 =γ i ·P, V i The identity information M1 = {ID i ,PID i 1 }Transmit to the trusted authority TA; S22. The trusted institution TA receives the vehicle V i After obtaining the identity information M1, select a random number α∈Z p * , calculate the public key P TA =α·P, and at the same time, V i Another part of the pseudonym: S23, the trusted institution TA sends the vehicle's complete pseudonym PID i ={PID i 1 ,PID i 2 }Sent to vehicle V via secure channel i ; S24, Vehicle V i Choose a random number x i ∈Z p * As a secret value, calculate X i =x i P, then the full pseudonym PID i and X i Send to KGC via secure channel; S25, KGC for vehicle V i Generate partial private key psk i ; S26, the vehicle verifies the validity of the partial private key and generates a complete key; In step S25, KGC is the vehicle V i Generate partial private key psk i The process includes the following steps: S251, KGC receives PID i and X i Then, first calculate u i =H1(PID i ,X i ,s), then calculate the vehicle V i Part of the private key y i =s·u i , and then calculate S252, KGC will part of the private key y i and K i Sent to vehicle V via secure channel i ; In step S26, the process of the vehicle verifying the validity of the partial private key and outputting the complete key includes the following steps: S261, Vehicle V i Received partial private key y i and K i After that, the partial private key is verified by: If the equation y i ·K i = =P pub If established, then some private keys are valid; S262, Vehicle V i The complete private key is composed of sk i ={x i ,y i }, the public key is X i .

4. The method for efficiently distributing fleet group keys based on improved multi-receiver signcryption technology according to claim 1 is characterized in that: The S3 step includes the following steps: S31. Select the team leader vehicle; S32, the leader vehicle performs offline preprocessing for group key generation; In step S31, the process of selecting a leader vehicle includes the following steps: S311, when the vehicle enters the effective communication range of the roadside unit RSU, after the identity legitimacy authentication is performed, the RSU dynamically generates a legal vehicle set List = {element1, element2, ..., element n }, each element in the collection contains the pseudonym and public key information of the legal vehicle; S312, Legal Vehicle V i Send resource information to RSU i ={PID i ,X i ,Loc i ,C i ,Comp i ,B i }, where PID i Indicates vehicle pseudonym, X i Indicates public key information, Loc i Indicates location information, C i Indicates available bandwidth resources, Comp i represents computing resources, B i Indicates battery status; S313, RSU receives vehicle V i Source i After that, the vehicle V i To perform a performance evaluation:

1. Calculate vehicle V i Distance to RSU: Where P t is the vehicle’s transmission power, G t is the transmitting antenna gain, G r is the receiving antenna gain, RSSI is the received signal strength, and α is the distance attenuation factor; 2. Calculate vehicle V i Communication capabilities: Among them C i is the available bandwidth resource of the vehicle, C max It is the largest available bandwidth resource within the fleet; 3. Evaluate computing resource advantages: Among themComp i is the computing resource of the current vehicle, Comp max It is the largest computing resource for the fleet; 4. Advantages of calculating battery status: Among them B i is the battery capacity of the vehicle, B max The largest battery capacity in the fleet; 5. Calculate vehicle V i Overall performance score Where: w1+w2+w3+w4=1; S314, RSU selects the vehicle with the highest score as the leader vehicle V s ; S315, RSU will be other legal vehicles in the fleet V j The public key X j Sent to leader vehicle V s , and broadcast the election results; S316, RSU periodically updates C based on the resource information of the newly certified vehicle max 、Comp max and B max The comprehensive score of each vehicle is recalculated according to step S313, and the leader vehicle is updated to timely adapt to the dynamic changes of the team, ensuring that the vehicle with the highest score in the team can serve as the leader; In step S32, the leader vehicle V s The offline preprocessing process of group key generation includes the following steps: S321, Team Leader Vehicle V s Choose a random number r∈Z p * , calculate R = rP, L j =ry j X j and α j =H2(R,L j ); S322, Team Leader Vehicle V s Randomly choose a number θ∈Z p * , construct an n-order polynomial: where a j ∈Z p * ; S323, Team Leader Vehicle V s Pre-generate offline ciphertext σ off =(R,L j ,θ,a n-1 ,...,a1,a0).

5. The method for efficiently distributing fleet group keys based on improved multi-receiver signcryption technology according to claim 1 is characterized in that: The S4 step includes the following steps: S41, Team Leader Vehicle V s Generate the signcrypted ciphertext σ=(Z,R,h,a n-1 ,...,a1,a0); In step S41, the leader vehicle V s The process of generating the signcrypted ciphertext σ includes the following steps: S411, Team Leader Vehicle V s Generate the group key K using a secure random number generator (CSPRNG) g , which is 256 bits long and can provide security equivalent to 128-bit symmetric encryption, in line with current mainstream cryptography standards; the randomness of the group key is guaranteed by CSPRNG to ensure its unpredictability, thus avoiding malicious speculation or reproduction; S412, Team Leader Vehicle V s Calculate and generate the symmetric encryption key t=H3(θ,R); S413, Team Leader Vehicle V s Select the secure AES-128 symmetric encryption function Enc(), use the key t, and encrypt the group key K g Encrypt and obtain the ciphertext Z=Enc t (K g ); S414, Team Leader Vehicle V s Execute hash calculation and obtain h = H4 (PID s ,K g ,R,θ,a n-1 ,...,a1,a0); S415, Team Leader Vehicle V s Generate the signcrypted ciphertext σ=(Z,R,h,a n-1 ,...,a1,a0), and broadcast the signature σ to other vehicles in the team.

6. The method for efficiently distributing fleet group keys based on improved multi-receiver signcryption technology according to claim 1 is characterized in that: The S5 step includes the following steps: S51、Other legally received vehicles in the fleet V j Decrypt the signcryption to obtain the group key K g ; In step S51, other legal receiving vehicles V in the fleet j Decrypt the signcryption to get the group key K g The process includes the following steps: S511、Legal acceptance of vehicles within the fleet V j Calculate L j =y j x j R, the correctness proof is: L j =y j x j R=y j x j (rP)=ry j (x) j P);=ry j X j =L j S512, legally receiving vehicle V j Calculate α j =H2(R,L j ), using the coefficient a in σ n-1 ,...,a1,a0 restore n-order polynomial S513, legally receiving vehicle V j Calculate θ = f(α j ) and t = H3(θ,R); S514, legally receiving vehicle V j Decrypt the ciphertext Z using the key t and the AES-128 symmetric decryption function Dec() to obtain the group key K g =Dec t (Z); S515, legally receiving vehicle V j Execute hash calculation to obtain h′=H4(PID s ,K g ,R,θ,a n-1 ,...,a1,a0), and verify whether the equation h′=h holds. If so, extract the group key K g ; Otherwise, return the termination symbol ⊥.

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