Attribute-based searchable encryption method and system supporting privacy protection and fair payment

Abstract

This invention relates to the field of edge computing security technology, specifically to an attribute-based searchable encryption method and system that supports privacy protection and fair payment. The scheme includes: an attribute authorization center generating parameters and user private keys; data owners collaborating with edge nodes to generate ciphertext and keyword indexes for hidden access policies; data users generating search trapdoors with the assistance of edge nodes; after matching by the cloud server, multiple smart contracts on the blockchain collaboratively execute fair payment; edge nodes pre-decrypt, and users satisfying the policy complete the final decryption. This invention solves the technical challenge of fair payment verification under policy concealment conditions, achieving fair payment between users and cloud servers through blockchain smart contracts, while offloading major computing tasks from the terminal using edge computing, significantly reducing overhead; and using matching verification equations as on-chain trusted signals, achieving synergistic effects of privacy protection and transaction fairness under policy concealment.

Description

Technical Field

[0001] This invention relates to the field of edge computing security technology, specifically to an attribute-based searchable encryption method and system that supports privacy protection and fair payment, and is mainly applied to edge computing scenarios that require privacy protection and fair transactions, such as vehicle networking and smart healthcare. Background Technology

[0002] In edge computing scenarios, lightweight terminal devices typically need to encrypt data and outsource it to cloud storage, while also requiring keyword retrieval of the encrypted data to balance data security and ease of use. The combination of Attribute-Based Encryption (ABE) and Searchable Encryption (SE) provides a feasible approach to this.

[0003] Existing research has made positive progress in its respective directions. For example, the scheme proposed by Shufen Niu et al. in 2023 utilizes edge nodes to offload computation, reducing the burden on lightweight devices, but the access policy is at risk of plaintext leakage and the issue of payment fairness remains unresolved. Public patent CN118764230A proposes using blockchain smart contracts to achieve fair payment for searches and outsourced decryption verification, but it does not consider access policy hiding, nor does it employ an edge computing architecture to further reduce user-end overhead. Public patent application CN202511082086.1 proposes an attribute-based searchable encryption method with dual privacy protection, achieving strong hiding of access policies and user attributes through inner product predicate encryption, but it completely fails to consider the crucial fair payment mechanism in data transaction scenarios.

[0004] In summary, existing technologies each have their own focus in terms of functionality, but none can simultaneously solve the following three technical challenges: privacy protection of access policies, fair payment for search services, and excessive computational overhead on the user side. More importantly, there is an inherent technical contradiction between hiding access policies (preventing third parties from knowing the policy content) and achieving fair payment (requiring sufficient information to verify and bill search results). Existing technologies have not directly addressed or resolved this contradiction. Summary of the Invention

[0005] The technical problem to be solved by this invention is to provide an attribute-based searchable encryption method and system that supports privacy protection and fair payment, thereby solving the problem that existing attribute-based searchable encryption schemes cannot simultaneously achieve access policy hiding and search-based fair payment in edge computing scenarios.

[0006] The technical solution adopted by this invention to solve its technical problem is: an attribute-based searchable encryption method that supports privacy protection and fair payment, comprising the following steps: S1: System initialization, the attribute authorization center inputs security parameters and outputs system public parameters, master public key and master private key; S2: Key generation, the attribute authorization center generates the private key of the data user based on the master public key and the attribute set of the data user; S3: Data encryption and index generation. The data owner uses a symmetric key to encrypt the file to be uploaded; the data owner anonymizes the access strategy through an access tree smart contract and sends the processed access tree to the edge node; the edge node generates a random polynomial for each node of the access tree to generate access structure ciphertext; the data owner and the edge node work together to generate the final ciphertext and keyword index, and upload the final ciphertext and keyword index to the cloud server provider; S4: Trapdoor generation: With the assistance of the edge node, the data user generates a search trapdoor based on the keyword to be searched, the master public key, and the user's private key, and sends it to the cloud server provider. S5: Ciphertext Search and Fair Payment: The cloud server provider performs matching verification between the search trap and the keyword index; when the match is successful, the cloud server provider returns the corresponding ciphertext to the edge node, and the smart contract executes the payment operation based on the matching result and the pre-decryption result of the edge node, thereby realizing fair payment between the data user and the cloud server provider. S6: Collaborative decryption: The edge node pre-decrypts the returned ciphertext; when the data user's attribute set satisfies the access policy set by the data owner, the edge node sends the pre-decryption result to the data user, and the data user completes the final decryption to obtain the plaintext file.

[0007] Furthermore, in step S3 of this invention, the data owner anonymizes the access strategy through the access tree smart contract, specifically as follows: The access strategy is represented in the form of an access tree, and the access tree is anonymized through the access tree smart contract, so that the processed access tree hides the specific attribute information and only retains the access structure.

[0008] Furthermore, in step S3 of this invention, the edge nodes generate random polynomials for each node of the access tree to generate access structure ciphertext, specifically as follows: The edge node selects a polynomial from the root node down for each node of the access tree, where the order of the polynomial is determined by the threshold of the node; for each leaf node, a corresponding ciphertext component is generated according to its associated attributes, and finally the access structure ciphertext is generated.

[0009] Furthermore, in step S5 of this invention, the cloud server provider performs matching verification between the search trap and the keyword index, specifically as follows: Verify whether the bilinear pairing equation holds true; if the equation holds true, the match is successful; otherwise, the match fails.

[0010] Furthermore, step S5 of this invention, which involves the smart contract performing a payment operation based on the matching result and the pre-decryption result of the edge node, includes: If the encrypted message returned by the cloud server provider is pre-decrypted by the edge node and the search results are confirmed to meet the data user's search requirements, the smart contract will execute the payment. If the returned message does not meet the search requirements, the data user may refuse to pay. If the data user claims that the returned information is incorrect after obtaining the correct search results, the smart contract guarantees that the cloud server provider will receive the fees it is entitled to.

[0011] Furthermore, in step S6 of this invention, the edge node pre-decrypts the returned ciphertext, specifically as follows: The edge node employs a recursive algorithm to calculate the intermediate decryption value layer by layer for the leaf nodes and non-leaf nodes of the access tree. The recursive operation obtains a valid result only when the attribute set of the data user satisfies the access strategy. The edge node then generates a pre-decryption result and sends it to the data user.

[0012] Furthermore, this invention also provides an attribute-based searchable encryption system that supports privacy protection and fair payment, comprising: The attribute authorization center module is used to generate system public parameters, master public key and master private key, and generate corresponding private keys based on the attribute set of data users; The data owner module is used to encrypt files using symmetric keys, anonymize access policies through the AccessTree smart contract, and collaborate with edge nodes to generate the final ciphertext and keyword index before uploading it to the cloud server provider. The data user module is used to generate search trapdoors with the assistance of edge nodes, initiate ciphertext search requests, and complete the final decryption after receiving the pre-decryption results; The edge node module is used to generate access structure ciphertext during the encryption phase, assist data users during the trapdoor generation phase, and pre-decrypt the ciphertext during the decryption phase. The cloud server provider module is used to store encrypted text and keyword indexes, perform matching verification between search traps and keyword indexes, and return encrypted text based on the matching results; The smart contract module is used to execute payment operations based on search matching results and pre-decryption results from edge nodes, enabling fair payments between data users and cloud server providers.

[0013] Furthermore, the system described in this invention is applied to a vehicle-to-everything (V2X) scenario, wherein the data owner is a roadside unit (RSU), the data user is a moving vehicle, and the edge node is deployed at the network edge close to the vehicle.

[0014] The beneficial effect of this invention is that it solves the defects existing in the prior art. 1. This invention does not simply combine strategy hiding with fair payment. Instead, it addresses the inherent contradiction between the two by cleverly transforming the bilinear pairing verification equation of keyword search and the recursive pre-decryption success status of edge nodes into judgment signals. This allows smart contracts to reliably perform billing and dispute resolution even when the plaintext access policy is completely invisible. This fundamentally solves the privacy risks inherent in existing technologies due to the lack of strategy hiding, and also addresses the problem of being unable to be applied to commercial transactions due to the lack of a payment mechanism.

[0015] 2. Unlike single-contract solutions, this invention employs multiple smart contracts to ensure fair payment during the search process. When the search results returned by the cloud server provider do not meet the user's search requirements, the user can refuse to pay. When the user receives correct search results but claims the returned information is incorrect, the smart contract ensures that the cloud server provider receives its due payment, thus resolving the issues of verifying the correctness of search results and ensuring payment fairness.

[0016] 3. Unlike existing cloud outsourcing or blockchain node computation technologies, this invention generates the access structure ciphertext by edge nodes during the encryption phase, assists in generating the final trapdoor during the trapdoor generation phase, and performs recursive pre-decryption by edge nodes during the decryption phase. This offloads computationally intensive operations from the user end to edge nodes, significantly reducing the computational burden on data users. The user terminal only needs to perform a very small number of lightweight operations, making the solution suitable for resource-constrained terminal devices.

[0017] 4. Based on CP-ABE, it enables data owners to implement fine-grained access control over data. It adopts anonymous access tree and multinomial hiding technology. Only data users whose attribute sets meet the access policy can successfully decrypt the ciphertext, which ensures secure data sharing. It ensures that even if a cloud server or malicious attacker obtains the ciphertext, it will not be able to parse any user sensitive attribute information contained in the access policy. The privacy protection strength is far superior to the solution without policy hiding. Attached Figure Description

[0018] Figure 1 This is a schematic block diagram of the system structure of the present invention; Figure 2 This is a schematic diagram of the operation of the system of the present invention. Detailed Implementation

[0019] The present invention will now be described in further detail with reference to the accompanying drawings and preferred embodiments. These drawings are simplified schematic diagrams, illustrating only the basic structure of the invention, and therefore only show the components relevant to the invention.

[0020] like Figure 1 The attribute-based searchable encryption system shown supports privacy protection and fair payment, comprising the following five entity parts: Attribute Authorization Center (AA): AA is completely honest and trustworthy, responsible for generating the system's public parameters, master public key, and master private key, and generating user private keys for each user.

[0021] Cloud Server Provider (CSP): The CSP is responsible for storing the keyword index and ciphertext, and sending the ciphertext containing the search keywords to the edge node when the search module is successfully executed.

[0022] Data Owner (DO): The data owner is responsible for building the access policy and generating the final ciphertext. The generated ciphertext is then uploaded to the CSP via the edge node.

[0023] Data User (DU): Each data user can generate a trapdoor corresponding to a search keyword. Using the trapdoor, they can obtain ciphertext containing the search keyword on the CSP. If their attributes meet the access policy in the ciphertext, they can decrypt the ciphertext using their own private key.

[0024] Edge Node (EN): The edge node generates a portion of the ciphertext and uploads the final ciphertext to the CSP. When decrypting the ciphertext, the EN performs partial decryption but does not learn any of the ciphertext's contents.

[0025] like Figure 2 As shown, the system's hardware includes the following components: System parameter setting module: Input security parameters The Attribute Authority (AA) outputs the public parameter PP and the master public key. and master private key The master public key Send the master private key to the key generation module, encryption module, and trapdoor generation module. Send it to the key generation module.

[0026] Key generation module: Attribute authorization center AA generates the key based on the system's master and public keys. and the set of attributes of data users Generate the private key for the data user. The data user's private key It is sent to the decryption module and the trapdoor generation module.

[0027] Encryption module: The data owner uses the system's master public key. The collection of files to be encrypted Visit tree and keyword set Output ciphertext and keyword index . ciphertext Send to the decryption module to index the keywords. Send to the search module.

[0028] Trapdoor generation module: Data users generate trapdoors based on the system's master public key. Data user's private key and the set of keywords to be searched Output trapdoor The trap door Send to the search module.

[0029] Search module: Cloud server provider (CSP) based on trapdoor and keyword index Output ciphertext . ciphertext Send to the decryption module.

[0030] Decryption module: Data users decrypt the received ciphertext. Private key Attribute set and symmetric keys Output file .

[0031] The following will combine Figure 2 The system will be described in detail for each module.

[0032] The system parameter setting module performs the following steps: Input security parameters Define a global property set The attribute authorization center AA selects large prime numbers. , Factorial Cyclic Group and Bilinear mapping .

[0033] Attribute Authorization Center AA Selection Group generator and Random selection Define two hash functions and For each attribute Attribute Authorization Center AA Selection Output common parameters public key and master private key .

[0034] The key generation module performs the following steps: Given a set of attributes of the data user and the system's master public key Random selection For all calculate , , , , The Attribute Authorization Center (AA) outputs the user's private key. .

[0035] The encryption module performs the following steps: Given a set of files Random selection The data owner, DO, uses a symmetric key. For each file Encryption, To encrypt the symmetric key The data owner, DO, uses AccessTree's smart contract, employing an anonymous access strategy and access tree. This indicates that DO will access the tree. Send to edge node EN.

[0036] Edge node EN is the access tree Each node From the root node Choose one from top to bottom polynomial of order The threshold is Set the root node. , For non-root nodes ,in Representative in visiting the tree The parents of the root node in Central Africa Representatives visited the tree The order of children of leaf nodes in Central Africa. It is a visit tree The set of leaf nodes, each leaf node Associated with an attribute. Edge node EN generates access schema ciphertext. , , Edge node EN outputs ciphertext .

[0037] Data owner DO randomly selected ,calculate , , The data owner, DO, sends encrypted data. To the edge node EN.

[0038] Edge node EN calculation , The edge node EN will then transmit the final ciphertext. Send to the cloud server provider (CSP).

[0039] Given the system's master public key The data owner (DO) is the access tree. Each attribute is randomly selected Random selection ,calculate , For keyword sets ,calculate , Data owner (DO) outputs keyword index And upload it to the cloud server provider CSP.

[0040] The trapdoor generation module performs the following steps: Given the system's master public key Data user DU's private key and the set of keywords that data users want to search for. Random selection ,calculate , , Data user DU output section trapdoor And send it to the edge node EN.

[0041] Given partial trapdoor Edge nodes EN are randomly selected. ,calculate , , Edge node EN output trapdoor And send it to the cloud server provider (CSP).

[0042] The search module performs the following steps: Keyword index uploaded by data owner DO to cloud server provider CSP The trap of data users (DU) uploading data to cloud server providers (CSPs). Cloud server provider CSP verification equation If the equation holds true, the cloud storage server's CSS returns encrypted text. Give the edge node EN; otherwise return 0. .

[0043] The decryption module performs the following steps: Edge node EN performs partial decryption first. Data user DU is randomly selected. ,calculate , , , , , , Data user DU will use a random private key and hidden attributes Send to edge node EN. Upon receiving the message at edge node EN... Afterwards, regarding the ciphertext Perform partial decryption. If... For visiting the tree A leaf node and Edge node EN calculation ,otherwise .if For visiting the tree A non-leaf node, edge node EN is recursively calculated. , For nodes The child nodes. for A set of arbitrary length, denoted as . If non-leaf nodes exist. , Through recursive calculations, the edge node EN is finally obtained. The calculation is performed if and only if the set of attributes of the data user DU satisfies the access policy set by the data owner DO.

[0044] .

[0045] Then, the edge node EN will Send to data user DU.

[0046] Given and symmetric keys The data user DU performs the final decryption. First, DU calculates... DU is known symmetric key DU can use symmetric keys Decryption .

[0047] The following will describe an example scenario of the application of the attribute-based searchable encryption method and system with policy hiding and fair payment described in the embodiments to edge computing.

[0048] For connected vehicle applications, suppose multiple roadside units (RSUs) on a certain road segment need to inform vehicles traveling on that segment about road congestion, traffic light warnings, and other information. The RSUs first encrypt and upload this information to a cloud server provider. Since the RSUs upload a large number of messages to the cloud storage server, vehicles traveling on that segment can perform keyword searches on the encrypted text in the cloud storage server according to their needs, and then download the encrypted text that matches their access policy. The RSUs help the vehicles pre-decrypt the downloaded encrypted text and send the pre-decrypted encrypted text back to the vehicles. The vehicles then use their private keys to decrypt and recover the plaintext. Furthermore, when a vehicle sends a keyword search request and the CSP returns a message, if the returned message does not match the vehicle's search requirements, the vehicle can refuse to pay the CSP. Simultaneously, if a vehicle receives the corresponding information but claims the returned information is incorrect, the smart contract ensures the CSP receives its due payment. Further, since access policies often contain sensitive information, cloud storage servers or malicious users might try to guess the information through the access policies. Therefore, access policies are hidden to protect user privacy.

[0049] The above description is only a specific embodiment of the present invention. Various examples and illustrations do not constitute a limitation on the substantive content of the present invention. Those skilled in the art can make modifications or variations to the above-described specific embodiments after reading the specification without departing from the substance and scope of the invention.

Claims

1. An attribute-based searchable encryption method that supports privacy protection and fair payment, characterized in that, Includes the following steps: S1: System initialization, the attribute authorization center inputs security parameters and outputs system public parameters, master public key and master private key; S2: Key generation, the attribute authorization center generates the private key of the data user based on the master public key and the attribute set of the data user; S3: Data encryption and index generation. The data owner uses a symmetric key to encrypt the file to be uploaded; the data owner anonymizes the access strategy through an access tree smart contract and sends the processed access tree to the edge node; the edge node generates a random polynomial for each node of the access tree to generate access structure ciphertext; the data owner and the edge node work together to generate the final ciphertext and keyword index, and upload the final ciphertext and keyword index to the cloud server provider; S4: Trapdoor generation: With the assistance of the edge node, the data user generates a search trapdoor based on the keyword to be searched, the master public key, and the user's private key, and sends it to the cloud server provider. S5: Ciphertext Search and Fair Payment: The cloud server provider performs matching verification between the search trap and the keyword index; when the match is successful, the cloud server provider returns the corresponding ciphertext to the edge node, and the smart contract executes the payment operation based on the matching result and the pre-decryption result of the edge node, thereby realizing fair payment between the data user and the cloud server provider. S6: Collaborative decryption: The edge node pre-decrypts the returned ciphertext; when the data user's attribute set satisfies the access policy set by the data owner, the edge node sends the pre-decryption result to the data user, and the data user completes the final decryption to obtain the plaintext file.

2. The attribute-based searchable encryption method supporting privacy protection and fair payment according to claim 1, characterized in that, In step S3, the data owner anonymizes the access strategy through the access tree smart contract, specifically as follows: The access strategy is represented in the form of an access tree, and the access tree is anonymized through the access tree smart contract, so that the processed access tree hides the specific attribute information and only retains the access structure.

3. The attribute-based searchable encryption method supporting privacy protection and fair payment according to claim 1, characterized in that, In step S3, the edge nodes generate random polynomials for each node of the access tree to generate the access structure ciphertext, specifically as follows: The edge node selects a polynomial from the root node down for each node of the access tree, where the order of the polynomial is determined by the threshold of the node; for each leaf node, a corresponding ciphertext component is generated according to its associated attributes, and finally the access structure ciphertext is generated.

4. The attribute-based searchable encryption method supporting privacy protection and fair payment according to claim 1, characterized in that, In step S5, the cloud server provider performs a matching verification between the search trap and the keyword index, specifically as follows: Verify whether the bilinear pairing equation holds true; if the equation holds true, the match is successful; otherwise, the match fails.

5. The attribute-based searchable encryption method supporting privacy protection and fair payment according to claim 1, characterized in that, The step S5, in which the smart contract executes the payment operation based on the matching result and the pre-decryption result of the edge node, includes: If the encrypted message returned by the cloud server provider is pre-decrypted by the edge node and the search results are confirmed to meet the data user's search requirements, the smart contract will execute the payment. If the returned message does not meet the search requirements, the data user may refuse to pay. If the data user claims that the returned information is incorrect after obtaining the correct search results, the smart contract guarantees that the cloud server provider will receive the fees it is entitled to.

6. The attribute-based searchable encryption method supporting privacy protection and fair payment according to claim 1, characterized in that, In step S6, the edge node pre-decrypts the returned ciphertext, specifically as follows: The edge node employs a recursive algorithm to calculate the intermediate decryption value layer by layer for the leaf nodes and non-leaf nodes of the access tree. The recursive operation obtains a valid result only when the attribute set of the data user satisfies the access strategy. The edge node then generates a pre-decryption result and sends it to the data user.

7. An attribute-based searchable encryption system that supports privacy protection and fair payment, characterized in that, include: The attribute authorization center module is used to generate system public parameters, master public key and master private key, and generate corresponding private keys based on the attribute set of data users; The data owner module is used to encrypt files using symmetric keys, anonymize access policies through the AccessTree smart contract, and collaborate with edge nodes to generate the final ciphertext and keyword index before uploading it to the cloud server provider. The data user module is used to generate search trapdoors with the assistance of edge nodes, initiate ciphertext search requests, and complete the final decryption after receiving the pre-decryption results; The edge node module is used to generate access structure ciphertext during the encryption phase, assist data users during the trapdoor generation phase, and pre-decrypt the ciphertext during the decryption phase. The cloud server provider module is used to store encrypted text and keyword indexes, perform matching verification between search traps and keyword indexes, and return encrypted text based on the matching results; The smart contract module is used to execute payment operations based on search matching results and pre-decryption results from edge nodes, enabling fair payments between data users and cloud server providers.

8. The attribute-based searchable encryption system supporting privacy protection and fair payment according to claim 7, characterized in that, The system is applied to vehicle-to-everything (V2X) scenarios, where the data owner is the Roadside Unit (RSU), the data user is the vehicle, and the edge node is deployed at the network edge close to the vehicle.

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