An attribute-based dual access control data sharing method for internet of vehicles

Abstract

The application discloses a kind of attribute-based Internet of Vehicles dual access control data sharing methods, user generates attribute key, and proxy key is generated using attribute key;Data owner is encrypted to data using attribute-based encryption algorithm according to defined semi-hidden access structure, considering the limited computing capacity of vehicle end, and the encryption process is divided into offline and online two stages;Cloud server filters out the false information sent by malicious user;(Access control is carried out to the download request sent by the user who wants to access data, so as to refuse EDOS attack;Only the user who satisfies access policy can decrypt ciphertext, and the decryption stage is also divided into two stages of outsourcing decryption and user decryption;Malicious user is revoked, and after malicious user is revoked, only the ciphertext related to revocation list needs to be updated, without updating the entire ciphertext.The application can realize the safe data sharing in Internet of Vehicles, and promotes the wide application of vehicle network.

Description

TECHNICAL FIELD

[0001] The present application relates to the Internet of Vehicles and attribute encryption technology, and in particular to an attribute-based dual access control data sharing method for Internet of Vehicles. BACKGROUND

[0002] Vehicle Ad Hoc Network (VANETs) is a kind of distributed self-organizing network, which improves the safety and efficiency of drivers by transmitting vehicle state information in real time. Through real-time monitoring of traffic flow, VANETs realizes intelligent planning, improves road traffic control capability, and injects new digital intelligence into urban traffic. VANETs also enhance the perception and computing power of roadside infrastructure by combining information with vehicles, thereby promoting the digitization of traffic governance. Although VANETs provide significant benefits for improving traffic efficiency, there are potential problems related to data privacy and security. For example, vehicle shared data may include personal and sensitive information such as vehicle owner identity and vehicle driving trajectory. In the dynamic network topology of VANETs, user privacy is most vulnerable to leakage, and leaked data and information can cause huge losses and even threaten public safety. Therefore, privacy protection is crucial in VANETs security.

[0003] In order to realize the safe sharing of data, it is required that the system reasonably encrypts the data of the vehicle user before transmission, and also has good access control. Ciphertext policy attribute-based encryption (CP-ABE) allows data owners to customize attribute-based access policies for their private data, so CP-ABE can be better combined with cloud data sharing systems. However, it is not enough to only implement access control for shared data in VANETs. In the VANETs environment, some special situations may be encountered. For example, a malicious vehicle may send an unlimited number of download requests to block the resources of the cloud server, thereby hindering its ability to properly respond to service requests from legitimate users. In addition to access control for shared data, effective access control for download requests from vehicles is also needed to ensure normal communication between vehicles,

[0004] In addition, in order to enhance user authentication and data retrieval functions, we integrate blockchain technology into the scheme. Blockchain is essentially a blockchain-stored, immutable, secure, and trusted decentralized distributed ledger, where each block has a different identifier from the previous block, creating a chain that can only be added. Blockchain uses its tamper-proof and trusted nature to achieve reliable data storage and strict access control through transaction verification and consensus mechanisms, ensuring data security and consistency. By taking advantage of the immutable nature of blockchain technology, secure tamper-proof data storage can be achieved, thereby ensuring data reliability and integrity. In our scheme, blockchain is mainly used for secure management of user identity and data information between vehicles and RSUs. Summary of the Invention

[0005] Purpose of the invention: The purpose of this invention is to address the shortcomings of existing technologies and provide an attribute-based dual access control data sharing method for vehicle networks.

[0006] Technical Solution: This invention provides an attribute-based dual access control data sharing method for vehicle networks, involving vehicles, attribute authority (AA), roadside unit (RSU), and cloud server (CSP), and includes the following steps:

[0007] Step (1): System initialization, attribute authority AA constructs bilinear pairing e: G×G→G T G and G T It is a multiplicative cyclic group of two prime numbers p, where g is a generator of the group; choose It is a cryptographic hash function. AA randomly selects h,v∈G and generates global parameters GP=(G,G T ,e,g,h,v,H);

[0008] Step (2): Initialize the attribute authority (AA), i.e., randomly select each AA. Set your private key as The corresponding public key is obtained through calculation.

[0009]

[0010] Step (3), Key Generation Stage: The attribute authority AA generates a decryption key SK and its corresponding blinding key AK for user DU.

[0011] Step (4), the ciphertext generation stage, involves two encryption stages: offline and online, before the data owner (DO) sends the data. The specific details are as follows:

[0012] Step (4-1), DO input R is the undo list, M is an l×n matrix, and ρ is a mapping function. Randomly select a vector Z = (s, z2, ..., z) for the attribute values ​​related to the access strategy. n ) T , s∈Z p ,(z2,...,z n )∈Z p

[0013] Step (4-2): Invoke the Linear Secret Sharing (LSSS) scheme, map a row in matrix M to a user attribute, and calculate λ. i =M i Z and s are used to encrypt data, (z2,...,z) n) is used to hide s;

[0014] Step (4-3): For i∈[1,l], randomly select t i ∈Z p Calculate the components of the ciphertext related to the access policy:

[0015]

[0016] Step (4-4): For j∈cover(R), calculate the ciphertext component associated with the revocation list R.

[0017]

[0018] The final ciphertext generated offline is as follows:

[0019] Steps (4-5), DO input m is the plaintext data to be encrypted, which is then encrypted online. The final ciphertext is generated as follows:

[0020] in It is a hidden access strategy that does not include attribute values;

[0021] Step (5), the ciphertext filtering stage, involves the cloud server CSP checking whether the ciphertext was generated under the declared access policy, thereby filtering out any fake ciphertext; the specific method is as follows:

[0022] Considering that some users might send false messages to the CSP, i.e., malicious users encrypting ciphertext without adhering to the defined access policy, the CSP will perform a filtering operation on the received ciphertext. The CSP randomly selects element γ and calculate

[0023]

[0024] CSP Inspection The equation is checked to see if it is true. If the equation is not true, CSP will reject the ciphertext, thus achieving the effect of ciphertext filtering.

[0025] Step (6), the download request access control phase: before DU accesses data, it will send a download request to CSP. CSP checks whether the download request is valid. If it is invalid, CSP rejects the download request, thus preventing EDOS attacks from occurring.

[0026] Step (7), the ciphertext decryption stage: before the DU that meets the access policy is finally decrypted, it will be outsourced to RSU to reduce the decryption overhead of the DU;

[0027] Step (8), user revocation stage, the system will track the malicious user and add its identity to the revocation list;

[0028] Step (9), ciphertext update stage, after the user revocation stage is completed, the system will perform a ciphertext update operation to update the relevant ciphertexts.

[0029] Further, the specific process of step (3) attribute authority AA generating a key for user DU is as follows:

[0030] Step (3-1), AA θ allocates a set of corresponding attributes S = {β1, β2,..., β θ} to each user, and constructs a binary tree in which the leaf nodes are associated with users;

[0031] Step (3-2), calculate the intermediate variable c = Enc k (i d ), where k is the key for symmetric encryption, i d is the serial number of the leaf node associated with the user in the binary tree;

[0032] Step (3-3), AA d constructs a binary tree for the user, where the leaf nodes represent users, and each node is assigned a random value; i represents the serial number, and i θ represents the serial number of the leaf node i assigns a random value x θ to each node in the binary tree, and randomly selects r, r1, r2,..., r p ∈Z r , generating a private key component related to the user's attributes;

[0033]

[0034] and the private key component related to the user's identity where is the value of the leaf node;

[0035] L1, L2, h r , g ri , are attribute-related private key components that need to be set for subsequent calculations and have no specific meaning; is the value of the binary tree leaf node; i in i ∈ [θ] is not the same as the subscript i of x i above, i in i ∈ [θ] represents the number of AA. The subscript i of x i above represents the serial number;

[0036] Step (3-4), algorithm output decryption key And send to the user through the secure channel.

[0037] Step (3-5), AA θ Use decryption key SK to generate the blind key AK and the corresponding recovery key RK required for outsourcing decryption. AA θ Randomly select Calculate

[0038]

[0039] Output AA θ Send SK and AK to the user.

[0040] Further, the specific process of step (6) download request access control phase is as follows:

[0041] Step (6-1), when DU wants to download data, send a download request to CSP, which contains its own attributes, CSP calls function ρ to map DU's attributes into attribute matrix M';

[0042] Step (6-2), determine whether the attribute matrix M' has an invertible matrix, if M' does not have an invertible matrix, it means that the DU attribute does not meet the access policy, that is, the encrypted exponent s cannot be reconstructed, which means that the user cannot decrypt the ciphertext, and the CSP will ignore the download request of the user.

[0043] Step (6-3), if M' has an invertible matrix, it means that the DU attribute meets the access policy, and the CSP will send the complete ciphertext C to the DU.

[0044] Further, the specific process of step (7) decryption ciphertext is as follows:

[0045] Step (7-1), call LSSS scheme to reconstruct Σ i∈I c i λ i =s, where c i is a set of vectors satisfying ∑ i∈I c i M i =(1,0,...,0);

[0046] Step (7-2), RSU calculates

[0047]

[0048] RSU sends pre-decryption ciphertext IC=(C1,B) to DU.

[0049] Step (7-3), after DU receives the pre-decryption ciphertext IC, the final decryption algorithm is executed to obtain the plaintext message m.

[0050]

[0051] Further, the specific method of step (8) is:

[0052] Step (8), by calculating i d = Dec k (K2) find the value of the leaf node in the binary tree, find the corresponding user identity u, add u to the revocation list R to obtain R'=R∪u; and prepare the ciphertext update operation.

[0053] Further, the specific process of step (9) is as follows:

[0054] Step (9-1), after the user is revoked, the value of the node in the binary tree needs to be updated, AA θ Randomly select t∈Z p , calculate For j'∈cover(R), there are two cases:

[0055] If there exists j∈cover(R) such that j=j', let

[0056] If there exists j∈cover(R) such that j is an ancestor of j', define path(j')=path(j)'{i dept(j)+1 ,...,i dept(j′)}, where i dept(j) =j, i dept(j′) =j'. k∈{depth(j),depth(j')}, iteratively calculate

[0057] Step (9-2), in the ciphertext update phase, the ciphertext component related to the access strategy does not change, only the ciphertext component related to the revocation list is changed, so the updated ciphertext is:

[0058]

[0059] Advantages: compared with the prior art, the present application has the following advantages:

[0060] (1) Considering the privacy of data and the security of communication, the encryption scheme designed realizes double access control. The data owner encrypts the data according to the access policy and sends it to the cloud server, ensuring that only users who meet the access policy can access the data. The scheme controls the download request of the user, ensures that the shared data in the cloud can only be downloaded by authorized users, and shows the ability of the system to resist EDOS attacks.

[0061] (2) Using the double-chain technology of the blockchain, transaction information and related authentication information and data are stored on the blockchain, realizing efficient user and data management. By deploying smart contracts on the user chain and the data chain, a complete user authentication and data security management mechanism can be established to ensure user privacy and data integrity.

[0062] Beneficial effects: We improve the traditional CP-ABE to realize secure data sharing. Our scheme uses blockchain for safer operation. In addition, the security of the cryptographic protocol is evaluated by formal security analysis, and can resist multiple types of attacks, and has stronger security compared with other related schemes. BRIEF DESCRIPTION OF DRAWINGS

[0063] Figure 1 The system model diagram of the present application;

[0064] Figure 2 The block structure diagram of the blockchain in the present application;

[0065] Figure 3 The smart contract cost diagram of the present application. DETAILED DESCRIPTION

[0066] The technical scheme of the present application will be described in detail below, but the protection scope of the present application is not limited to the described embodiments.

[0067] The present application realizes flexible access control while supporting secure data sharing, adopts the LSSS scheme to divide the attributes into attribute value and attribute name two parts, and encrypts the attribute value to realize policy hiding; the data owner DO formulates an access policy, only users who meet the access policy can access and decrypt the ciphertext; the CSP filters out false messages sent by malicious users; the CSP performs fine-grained access control on the download request, and refuses the occurrence of EDOS attack; the system supports user revocation operation, adds the identity information of malicious users to the revocation list to refuse the access request of malicious users; at the same time, the blockchain is used for security management of user identity and data information between vehicles and RSUs, and the specific content is that the user identity is written into the user chain, and the ciphertext address and ciphertext hash are written into the data chain.

[0068] As Figure 1As shown, the present application relates to the following participating entities, namely attribute authority (AA), data owner (DO), roadside unit (RSU), data user (DU), cloud server provider (CSP) and blockchain network.

[0069] The attribute authority is responsible for generating the global parameters within its management domain and generating the attribute keys of the DUs; the data owner formulates the access policy and uploads the ciphertext to the CSP; the RSU acts as a communication medium and executes the outsourcing decryption algorithm; when the user's attributes meet the access policy of the ciphertext, the user can access the data and use the decryption algorithm to decrypt the file using the key to obtain the plaintext. If the data owner deletes any user, the user cannot access the data; the cloud service provider stores the encrypted files uploaded by the data owner and provides ciphertext filtering and download request access control functions, which manage the access to the stored data and provide related services.

[0070] The attribute-based dual access control data sharing method for Internet of Vehicles of the present application comprises the following steps:

[0071] Step (1), system initialization, the attribute authority AA constructs a bilinear pairing e:GxG→G T , G and G T are two multiplicative cyclic groups of prime order p, g is the generator of the group; select H is an encryption hash function, AA randomly selects h, v∈G, generates the global parameter GP=(G, G T , e, g, h, v, H);

[0072] Step (2), initialization of the attribute authority AA, that is, each AA randomly selects sets its private key as and obtains the corresponding public key

[0073]

[0074] Step (3), key generation phase, the attribute authority AA generates the decryption key SK of the user DU and the corresponding blinding key AK;

[0075] Step (4), ciphertext generation phase, the data owner DO sends data after two stages of offline encryption and online encryption; the specific content is:

[0076] Step (4-1), DO inputs R is a revocation list, M is an lxn matrix, ρ is a mapping function, a set of vectors Z=(s, z2,..., zn) is randomly selected according to the attribute values related to the access policy, n T s∈Z​p ,(z2,...,z n )∈Z p

[0077] Step (4-2): Invoke the Linear Secret Sharing (LSSS) scheme, map a row in matrix M to a user attribute, and calculate λ. i =M i Z and s are used to encrypt data, (z2,...,z) n ) is used to hide s;

[0078] Step (4-3): For i∈[1,l], randomly select t i ∈Z p Calculate the components of the ciphertext related to the access policy:

[0079]

[0080] Step (4-4): For j∈cover(R), calculate the ciphertext component associated with the revocation list R.

[0081]

[0082] The final ciphertext generated offline is as follows:

[0083] Steps (4-5), DO input m is the plaintext data to be encrypted, which is then encrypted online. The final ciphertext is generated as follows:

[0084] in It is a hidden access strategy that does not include attribute values;

[0085] Step (5), the ciphertext filtering stage, involves the cloud server CSP checking whether the ciphertext was generated under the declared access policy, thereby filtering out any fake ciphertext; the specific method is as follows:

[0086] The cloud server CSP performs a filtering operation on the received ciphertext, and the CSP randomly selects element γ and calculate

[0087]

[0088]

[0089] CSP Inspection The CSP checks whether the equation is true or false. If the equation is false, the CSP will reject the ciphertext.

[0090] Step (6), download request access control phase, before the DU accesses the data, the DU sends a download request to the cloud server CSP, the CSP checks whether the download request is legal, if not, the CSP rejects the download request;

[0091] Step (7), the ciphertext decryption phase, the DU that meets the access strategy will be outsourced decryption by the RSU before the final decryption;

[0092] Step (8), user revocation phase, the malicious user will be tracked and its identity will be added to the revocation list;

[0093] Step (9), ciphertext update phase, after the user revocation phase is completed, the ciphertext update operation is performed, and the related ciphertext is updated.

[0094] The specific process of step (3) of the attribute authority AA generating a key for the user DU is as follows:

[0095] Step (3-1), AA θ allocates a set of corresponding attributes S={β1,β2,...,β θ} to each user, and constructs a binary tree, wherein the leaf nodes are associated with the users;

[0096] Step (3-2), calculate the intermediate variable c=Enc k (i d ), wherein k is the key of symmetric encryption, i d is the serial number of the leaf node associated with the user in the binary tree;

[0097] Step (3-3), AA θ allocates a random value x i to each node in the binary tree, i represents the serial number, i d represents the serial number of the leaf node, and randomly selects r, r1, r2,..., r θ ∈Z p , to generate a private key component related to the user attribute;

[0098]

[0099] and the private key component related to the user identity wherein is the value of the leaf node;

[0100] Step (3-4), the algorithm outputs the decryption key and sends it to the user through a secure channel;

[0101] Step (3-5), AA θThe blind key AK and the corresponding recovery key RK required for decryption outsourcing are generated using the decryption key SK; AA θ Randomly selected Calculate:

[0102]

[0103] Output

[0104] Finally, AA θ Send SK and AK to the user.

[0105] The specific process of embodiment step (6) download request access control phase is as follows:

[0106] Step (6-1), when the DU wants to download data, send a download request to the CSP, which contains its own attributes, and the CSP calls the function ρ to map the DU's attributes into the attribute matrix M';

[0107] Step (6-2), determine whether the attribute matrix M' has an invertible matrix, if M' does not have an invertible matrix, it means that the DU attributes do not meet the access policy, that is, the encrypted exponent s cannot be reconstructed, which means that the user cannot decrypt the ciphertext, and the CSP ignores the download request of the user;

[0108] Step (6-3), if M' has an invertible matrix, it means that the DU attributes meet the access policy, and the CSP will send the complete ciphertext C to the DU.

[0109] The specific process of embodiment step (7) decryption of ciphertext is as follows:

[0110] Step (7-1), call the LSSS scheme to reconstruct ∑ i∈I c i λ i = s, where c i is a set of vectors satisfying ∑ i∈I c i M i = (1, 0,..., 0);

[0111] Step (7-2), the RSU calculates

[0112]

[0113] The RSU sends the pre-decryption ciphertext IC = (C1, B) to the DU;

[0114] Step (7-3), after receiving the pre-decryption ciphertext IC, the DU executes the final decryption algorithm to obtain the plaintext message m;

[0115]

[0116] The specific method of step (8) of the embodiment is as follows:

[0117] Calculate i d = Dec k (K2) Find the value of the leaf node in the binary tree, find the corresponding user identity u, add u to the revocation list R to obtain R'=R∪u; and prepare the ciphertext update operation.

[0118] The specific process of step (9) of the embodiment is as follows:

[0119] Step (9-1), after the user is revoked, the value of the node in the binary tree needs to be updated, AA θ Randomly select t∈Z p , and calculate For j'∈cover(R), there are two cases:

[0120] If there exists j∈cover(R) such that j=j', then let

[0121] If there exists j∈cover(R) such that j is an ancestor of j', define path(j')=path(j)∪{i dept(j)+1 ,...,i dept(j′)},

[0122] Where i dept(j) =j, i dept(j′) =j', k∈{depth(j),depth(j')}, and iteratively calculate

[0123] Step (9-2), in the ciphertext update phase, the ciphertext component related to the access policy does not change, only the ciphertext component related to the revocation list is changed, so the updated ciphertext is:

[0124]

[0125] In order to facilitate the understanding of the technical solutions of the embodiment, the meanings of related variables are explained first, and the specific contents are shown in Table 1.

[0126] Table 1

[0127]

[0128]

[0129] Embodiment:

[0130] The blockchain structure adopted in the embodiment is as follows: Figure 2As shown, a block in this blockchain consists of a block header and a block body. The block header contains the hash of the previous block and the root of a Merkle tree, in which a large amount of complex data is recorded.

[0131] The functional implementation of the technical solution of the present invention is compared, and the results are shown in Table 2. The technical solution of the present invention supports more functions suitable for vehicle networking.

[0132] Table 2 Functional Implementation Analysis

[0133]

[11]

[18]

[24] [2] Ours Access structure LSSS LSSS LSSS LSSS LSSS Traceability × × × × √ Recovation level × Attribute User User,Attribute User Update × Ciphertext,Key Key Ciphertext,Key Ciphertext Based-Blockchain × × × × √ Outsources decryption √ √ × √ √ Request control × × × × √ Ciphertext check × × × × √ Forward security √ √ √ √ √ Backward security √ × √ √ √

[0134] The computational overhead of the technical solution of the present invention is compared, and the results are shown in Table 3. The technical solution of the present invention still has good computational overhead under relatively secure privacy protection.

[0135] Table 3 Computational Cost Analysis

[0136]

[0137] Where E is the time taken for exponential operations on the group, P is the time taken for bilinear pairing, M is the time taken for multiplication operations on the group, s is the number of user attributes, u is the number of user attributes managed by an authority, H is the time taken for hash operations, and t is the number of attributes that have been revoked.

[0138] like Figure 3 As shown in the figure, the cost of the smart contract in the technical solution of the present invention can be seen to have reasonable gas consumption, which is feasible for the Internet of Vehicles.

Claims

1. An attribute-based dual access control data sharing method for Internet of Vehicles, characterized in that, Comprise the following steps: Step (1), system initialization, attribute authority AA constructs a bilinear pairing e:GxG→G T , G and G T are two multiplicative cyclic groups of prime order p, g is the generator of the group; select H: is a cryptographic hash function, AA randomly selects h, v∈G, and generates global parameters GP=(G, G T , e, g, h, v, H); Step (2), initialization of attribute authorities AA, i.e. each AA randomly selects Set its own private key as And through the calculation of the corresponding public key Step (3), the key generation stage, attribute authority AA generates decryption key SK and its corresponding blind key AK for user DU; Step (4), the ciphertext generation stage, the data owner DO sends data before offline encryption and online encryption two stages; The specific content is: Step (4-1), DO input R is a revocation list, M is an l x n matrix, p is a mapping function, The attribute values related to the access policy are randomly selected to form a set of vectors Z = (s, z2,..., zn) such that n ) T s e Z p (z2,..., zn) e Z n p ​ Step (4-2), call linear secret sharing LSSS scheme, map a row in matrix M to a user's attribute, calculate λ i = M i · Z, s is used to encrypt data, (z2,..., z n ) is used to hide s; Step (4-3), randomly select t for i∈[1, l] i ∈Z p Compute the component of the ciphertext related to the access policy: Step (4-4), for j e cover(R), compute the ciphertext component related to the revocation list R The ciphertext generated by offline encryption ends up as follows: Step (4-5), DO input m is the plaintext data to be encrypted, calculated by on-line encryption The final ciphertext is generated as follows: wherein is a hidden access policy that does not include attribute values; Step (5), the ciphertext filtering stage, the cloud server CSP checks whether the ciphertext is encrypted under the declared access policy, thereby filtering out which false ciphertext; The specific method is: The cloud server CSP performs a filtering operation on the received ciphertext, the CSP randomly selects an element γ and The computation CSP checks whether the equation holds, and if the equation does not hold, the CSP rejects the ciphertext; Step (6), the download request access control stage, DU sends a download request to the cloud server CSP before accessing the data, and the CSP checks whether the download request is legal, and if not, the CSP rejects the download request; Step (7), the decryption ciphertext stage, the DU that meets the access policy will be outsourced decryption by RSU before final decryption; Step (8), the user revocation stage, the malicious user will be tracked and its identity will be added to the revocation list; Step (9), the ciphertext update stage, after the user revocation stage is completed, the ciphertext update operation is carried out, and the related ciphertext is updated.

2. The attribute-based dual access control data sharing method for V2X according to claim 1, wherein, The specific process of the step (3) attribute authority AA generating key for user DU is as follows: Step (3-1), AA θ A set of corresponding attributes S = {β1, β2,..., βn} is assigned to each user, and a binary tree is constructed, in which the leaf nodes are associated with users. θ} is assigned to each user, and a binary tree is constructed, in which the leaf nodes are associated with users. Step (3-2), compute the intermediate variable c = Enc k (i d ), where k is the key for symmetric encryption, i d is the serial number of the leaf node associated with the user in the binary tree; Step (3-3), AA θ Assign a random value x to each node in the binary tree i , i represents the serial number, i d represents the serial number of the leaf node, and randomly selects r, r1, r2,..., r θ ∈Z p Generate a private key component related to the user attribute; Private key components related to a user identity wherein is the value of a leaf node; Step (3-4), algorithm outputs decryption key and sent to the user through a secure channel. Step (3-5), AA θ The blinding key AK needed for outsourcing decryption and the corresponding recovery key RK are generated using the decryption key SK;AA θ Randomly select Compute: Output RK = τ; Finally, the AA θ The SK and AK are sent to the user.

3. The attribute-based dual access control data sharing method for V2X according to claim 1, wherein, The specific process of the step (6) download request access control stage is as follows: Step (6-1), when DU wants to download data, sends a download request to CSP, which contains its own attributes, and CSP calls function ρ to map DU's attributes into attribute matrix M'; Step (6-2), it is judged whether the attribute matrix M' exists an invertible matrix, if M' does not exist an invertible matrix, it indicates that the DU attribute does not meet the access policy, that is, the encrypted exponent s cannot be reconstructed, indicating that the user cannot decrypt the ciphertext, and the CSP ignores the download request of the user; Step (6-3), if M' exists an invertible matrix, it indicates that the DU attribute meets the access policy, and the CSP will send the complete ciphertext C to the DU.

4. The attribute-based dual access control data sharing method for V2X according to claim 1, wherein, The specific process of the step (7) decryption ciphertext is as follows: Step (7-1), call LSSS scheme to reconstruct i∈I c i λ i = s, where c i is a set of vectors satisfying Σ i∈I c i M i = (1, 0,..., 0); Step (7-2), RSU calculates RSU sends the pre-decryption ciphertext IC=(C1,B) to DU; Step (7-3), after DU receives the pre-decryption ciphertext IC, the final decryption algorithm is executed to obtain the plaintext message m; 5. The attribute-based dual access control data sharing method for V2X according to claim 1, wherein, The specific method of the step (8) user revocation is: By calculating i d = Dec k (K2) Find the value of the leaf node in the binary tree, find the corresponding user identity u, add u to the revocation list R to get R'=R∪u; and prepare the ciphertext update operation.

6. The attribute-based dual access control data sharing method for V2X according to claim 1, wherein, The specific process of the step (9) ciphertext update is as follows: Step (9-1), when the user cancels, the value of the node in the binary tree needs to be updated, AA θ Randomly select t∈Z p , the calculation is For j'∈cover(R), there are two cases: If there exists j e cover(R) such that j = j', then let If there exists j∈cover(R) such that j is an ancestor of j', define path(j') = path(j) U {i dept(j)+1 ,...,i dept(j′)} where i dept(j) = j, i dept(j′) = j', k e {depth(j), depth(j')}, iteratively calculating Step (9-2), in the ciphertext update stage, the ciphertext components related to the access policy are not changed, only the ciphertext components related to the revocation list are changed, so the updated ciphertext is:

Images