Decentralized multi-client function encryption method and system supporting bilateral privacy protection

Abstract

This invention discloses a decentralized multi-client function encryption method and system supporting bilateral privacy protection. The method includes a system initialization phase, a client initialization phase, an encryption phase, a partial key generation phase, a key aggregation phase, and a decryption phase. It supports multiple clients independently encrypting and managing data. Once a user obtains the corresponding key from the desired client, they can perform function calculations on the encrypted data from those clients to obtain the function value. This method simultaneously supports the privacy protection of the data requester's identity and the client's function privacy, offering high security and reliability, and better meeting practical application needs.

Description

Technical Field

[0001] This invention belongs to the technical field of computer security, and mainly relates to a decentralized multi-client function encryption method and system that supports bilateral privacy protection. Background Technology

[0002] Mobile crowdsourcing sensing leverages the sensing and computing capabilities of numerous mobile intelligent terminals, such as smartphones and in-vehicle devices, to collaboratively collect and analyze data on urban environments, traffic conditions, and social behaviors. This model significantly expands the coverage and real-time performance of traditional sensing systems, but challenges remain regarding data privacy protection, communication overhead, and participant incentive mechanisms. Most existing solutions cannot support selective computation of encrypted data, typically employing an "all or nothing" access model, which struggles to meet the diverse and customizable data processing needs of complex scenarios, thus limiting their flexibility and security in large-scale collaborative applications.

[0003] Multi-client function encryption is a new type of encryption technology that allows a trusted authorization center to encrypt specified functions. Generate a private key Each client generates its own ciphertext independently. When given ciphertext and private key At that time, the key holder can calculate the function value. However, no other information about the plaintext can be obtained. Therefore, multi-client function encryption protects data confidentiality while processing data. Inner product operation is a fundamental and commonly used computational operation, widely used in data statistical analysis and pattern mining, such as traffic flow estimation, environmental monitoring fusion, and behavioral feature analysis. In a multi-client inner product function encryption scheme, authorized users can jointly decrypt ciphertext generated by multiple clients without obtaining the plaintext data from each client, calculating the inner product value between the plaintext vector and the function vector, thus achieving privacy-preserving aggregation and analysis of multi-source sensing data.

[0004] Existing multi-client inner product function encryption schemes typically only focus on protecting the privacy of the data provider / client, and struggle to simultaneously guarantee the identity privacy of the data requester and the function privacy of the client, i.e., they lack a bilateral privacy protection mechanism. Summary of the Invention

[0005] This invention addresses the problems existing in the prior art by providing a decentralized multi-client function encryption method and system that supports bilateral privacy protection. The method includes a system initialization phase, a client initialization phase, an encryption phase, a partial key generation phase, a key aggregation phase, and a decryption phase. It supports multiple clients independently encrypting and managing data. Once a user obtains the corresponding key from the desired client, they can perform function calculations on the encrypted data from those clients to obtain the function value. This invention simultaneously supports the privacy protection of the data requester's identity and the client's function privacy, offering high security and reliability, and better meeting practical application needs.

[0006] To achieve the above objectives, the technical solution adopted by this invention is: a decentralized multi-client function encryption method supporting bilateral privacy protection, comprising the following steps:

[0007] S1. System initialization phase: The system inputs a security parameter. Output system common parameters ,Right now:

[0008] ;

[0009] in, Given an asymmetric bilinear group generation algorithm, input safety parameters... Output prime numbers Cyclic group ,in ;

[0010] S2, Client Initialization Phase: Each client Input system common parameters Output the client's secret key Client encryption key and client public key ,Right now:

[0011] ;

[0012] S3, Encryption Phase: Sending encryption information to the client Input system common parameters Plaintext vector The Each component Encryption key and encrypted tags Output ciphertext ,Right now:

[0013] ;

[0014] S4, Partial Key Generation Phase: Sending Keys to Clients Input system common parameters A global identifier for a data requester A client set Secret Key Function vectors The Each component and key tag Output partial key ,Right now:

[0015] ;

[0016] S5, Key Aggregation Phase: Data requester inputs system common parameters Partial key set Output decryption key ,Right now:

[0017] ;

[0018] S6. Decryption Phase: Data aggregator inputs system common parameters. Decryption key ciphertext collection and encrypted tags Output the inner product value ,Right now:

[0019] .

[0020] To achieve the above objectives, the present invention also adopts the following technical solution: a decentralized multi-client function encryption system supporting bilateral privacy protection, comprising a computer program, wherein when the computer program is executed by a processor, it implements the steps of a decentralized multi-client function encryption method supporting bilateral privacy protection.

[0021] Compared with the prior art, the technical effects and advantages of the present invention are as follows:

[0022] (1) The method of the present invention does not require the participation of a trusted center, supports multiple clients to coexist and run independently, each client can perform partial key generation and local encryption operations respectively, and the whole process does not require interaction, while resisting the "mix-match" attack of ciphertext.

[0023] (2) In the method of the present invention, authorized users can perform joint calculations on ciphertext from multiple clients and can only obtain the corresponding plaintext function value, but cannot obtain any other information about the plaintext, thereby achieving data privacy protection.

[0024] (3) In the method of the present invention, the client can generate and distribute part of the key to the data requester without knowing the identity information of the data requester, and can hide the function privacy information in the key from the data requester, thereby achieving two-way privacy protection.

[0025] (4) The method of the present invention supports the dynamic addition of clients to the system, which enhances the scalability of the system. Attached Figure Description

[0026] Figure 1 This is a flowchart illustrating the steps of the decentralized multi-client function encryption method supporting bilateral privacy protection according to the present invention. Detailed Implementation

[0027] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0028] Example 1

[0029] A decentralized multi-client function encryption method supporting bilateral privacy protection enhances the overall privacy, security, and usability of the system by simultaneously hiding the identity of the data requester and the client function input while ensuring the correct computation of the inner product result. Furthermore, it removes the dependence on a trusted center, effectively avoiding the single point of failure problem caused by a single trusted entity in traditional multi-client function encryption schemes. This reduces system operational risks and trust assumptions, significantly improving overall robustness and scalability while maintaining security. The steps are as follows: Figure 1 As shown, it includes the following steps:

[0030] Step S1, System Initialization Phase: The system inputs a security parameter. Output system common parameters ,Right now:

[0031] ;

[0032] Assumption This is an asymmetric bilinear group generation algorithm, which takes a security parameter as input. Output prime numbers Cyclic group ,in The system inputs a security parameter. ,run Select generators , and four hash functions , ,in For model The cyclic group that forms the system. Common parameters of the system. .

[0033] Step S2, Client Initialization Phase: Each client Input system common parameters Output the client's secret key Client encryption key Client public key ,Right now:

[0034] ;

[0035] This phase is handled by each client. Executes independently. (Client) Select , Client Generate your own secret key independently Encryption key And calculate the public key. No trust center is required.

[0036] Step S3, Encryption Phase: Client Input system common parameters plaintext vector The Each component Client encryption key Encrypted tags Output ciphertext ,Right now:

[0037] ;

[0038] This phase is executed independently by each client, and ciphertext tags are embedded in the ciphertext. Only ciphertexts with matching tags can be combined for decryption, thus resisting "mix-match" attacks. This is for encrypting messages. In a ciphertext tag Next, client Calculate the hash value of the ciphertext tag Set up blind plaintext Using encryption keys Generate ciphertext The details are as follows:

[0039] .

[0040] Step S4, Partial Key Generation Stage: Client Input system common parameters A global identifier for a data requester A client collection Client secret key function vector The Each component and key tag Output partial key ,Right now:

[0041] ;

[0042] This phase is handled by each client. Execution involves interaction with the data requester. Each client operates without knowing the identity of the data requester. In such cases, a corresponding function key is generated to avoid privacy risks caused by the leakage of identity information. Simultaneously, the client, during the function key generation process, includes function information... By hiding the data, the data requester cannot know the actual function content used by the client, thereby achieving dual protection of the privacy of the data requester's identity and the privacy of the client's function.

[0043] First, the data requester randomly selects... Calculate the global identity identifier of the data requester. hash value A zero-knowledge proof and supporting evidence ,send For the required clients ,in It is a client-side index set.

[0044] Then, the client receive Then, randomly select , Select the specified function Set up a blind function For the specified key tag , Calculate the hash value of the key tag Choose a random value Calculate the symmetric key Using a symmetric encryption algorithm to Encryption, that is, the symmetric ciphertext of the private key is . Calculate key tag ciphertext and auxiliary key Choose a random value The hash value of the calculation function Each key consists of , , , , , , Compute a zero-knowledge proof. Send data tuple For the data requester.

[0045] Finally, the data requester received in Then, calculate , ,in Configure the client. function key The partial function key generated for the data requester is .

[0046] Step S5, Key Aggregation Stage: The data requester inputs system common parameters. Partial key set Output decryption key ,Right now:

[0047] ;

[0048] This phase is performed by the data requester if the data requester obtains the required client. Partial function key This allows the aggregation of the complete decryption key, which can then be used for subsequent decryption operations. The data requester recovers the symmetric key. Run the symmetric encryption decryption algorithm Decrypt , can be calculated The decryption key is as follows:

[0049] .

[0050] Step S6, Decryption Phase: The data aggregator inputs the system's common parameters. A decryption key ciphertext collection and encrypted tags Output the inner product value ,Right now:

[0051] .

[0052] This stage is performed by the data requester. (Received encrypted message) and decryption key The data requester supports the following calculations:

[0053] .

[0054] Verify decryption correctness:

[0055] ;

[0056] ;

[0057] ;

[0058] ;

[0059] ;

[0060] therefore:

[0061] .

[0062] In summary, this invention proposes a decentralized multi-client function encryption method that supports bilateral privacy protection. In this method, each client can operate independently and autonomously complete partial key generation and local encryption without a trusted central authority, and no interaction is required. By embedding a tagging mechanism in the ciphertext, it ensures that only ciphertexts with matching tags can be combined for decryption, effectively resisting "mix-match" attacks. Clients can generate and distribute partial keys to data requesters without knowing their identity, while simultaneously hiding function privacy information within their keys from the data requester, achieving two-way privacy protection. Authorized users can decrypt and calculate specific function values ​​without the participation of all clients in the system, and cannot obtain any other information from the plaintext except for the calculation result. This method allows for dynamic client addition, thus better meeting practical needs.

[0063] It should be noted that the above content merely illustrates the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. For those skilled in the art, various improvements and modifications can be made without departing from the principle of the present invention, and all such improvements and modifications fall within the scope of protection of the claims of the present invention.

Claims

1. A decentralized multi-client function encryption method supporting bilateral privacy protection, characterized in that, Includes the following steps: S1. System initialization phase: The system inputs a security parameter. Output system common parameters ,Right now: ； in, Given an asymmetric bilinear group generation algorithm, input safety parameters... Output prime numbers Cyclic group ,in ; S2, Client Initialization Phase: Each client Input system common parameters Output the client's secret key Client encryption key and client public key ,Right now: ; S3, Encryption Phase: Sending encryption information to the client Input system common parameters Plaintext vector The Each component Encryption key and encrypted tags Output ciphertext ,Right now: ； S4, Partial Key Generation Phase: Sending Keys to Clients Input system common parameters A global identifier for a data requester A client set Secret Key Function vectors The Each component and key tag Output partial key ,Right now: ； S5, Key Aggregation Phase: Data requester inputs system common parameters Partial key set Output the decryption key ,Right now: ; S6. Decryption Phase: Data aggregator inputs system common parameters. Decryption key ciphertext collection and encrypted tags Output the inner product value ,Right now: 。 2. The decentralized multi-client function encryption method supporting bilateral privacy protection as described in claim 1, characterized in that: In step S1, the system's common parameters ,in, They are and generator, , They are respectively: , ,in For model A cyclic group.

3. The decentralized multi-client function encryption method supporting bilateral privacy protection as described in claim 2, characterized in that: Step S2 is performed by each client. Executes independently, with each client generating its own secret key. Encryption key and calculate public key No trusted center is required; among them, , .

4. The decentralized multi-client function encryption method supporting bilateral privacy protection as described in claim 3, characterized in that: Step S3 is performed by each client. Execute independently, in encrypted label Next, client Calculate the hash value of the ciphertext tag Set up blind plaintext Using encryption keys Generate ciphertext The details are as follows: 。 5. The decentralized multi-client function encryption method supporting bilateral privacy protection as described in claim 2, characterized in that: Step S4 specifically includes the following steps: S41: Data requester randomly selected Calculate the global identity of the data requester. hash value and zero-knowledge proof ,send For the required clients ,in For the set of indexes of participating clients; S42: Client Received from step S41 Then, randomly select , Select the specified function Set up a blind function ; For the specified key tag , Calculate the hash value of the key tag Choose a random value Calculate the symmetric key Using a symmetric encryption algorithm to Encryption, specifically the symmetric ciphertext of the private key. ; Calculate the key tag ciphertext Auxiliary key Select random value The hash value of the calculation function Each key consists of , , , , , , Compute a zero-knowledge proof ; The above information is grouped into data tuples. Send to the data requester; S43: After receiving the data tuple from step S42, the data requester calculates... and Configure the client function key Generate partial function keys for data requesters. .

6. The decentralized multi-client function encryption method supporting bilateral privacy protection as described in claim 2, characterized in that: In step S5, the data requester calculates the recovery symmetric key. Run the symmetric encryption decryption algorithm Decrypt , can be calculated ,in For the data requester's random value Random values ​​from the client The sum of .

7. The decentralized multi-client function encryption method supporting bilateral privacy protection as described in claim 2, characterized in that: In step S6, when the data requester obtains a portion of the client's function key, it correctly decrypts the data based on the aggregated key and by performing the following formula: 。 8. A decentralized multi-client function encryption system supporting bilateral privacy protection, comprising a computer program, characterized in that: When the computer program is executed by a processor, it implements the steps of the method as described in any one of claims 1-7 above.

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