Ciphertext access control method based on multi-chain key generation and distribution

Abstract

This invention provides a ciphertext access control method based on multi-chain key generation and distribution, belonging to the field of blockchain technology. The method comprises the following steps: establishing a ciphertext access control system; user registration and system initialization, in which the ciphertext access control system issues identity identifiers to all users and performs system initialization; ciphertext encryption, in which the data owner formulates an access policy, encrypts the data using an encryption algorithm, and uploads the ciphertext; a ciphertext generation and distribution node determines whether the data user meets the access policy and, if so, generates an attribute private key for the data user; and ciphertext decryption, in which the data user downloads the ciphertext and executes the decryption algorithm to obtain the ciphertext data. This invention can improve the efficiency, security, and scalability of existing key generation and distribution methods.

Description

Technical Field

[0001] The present invention belongs to the field of blockchain technology, and in particular relates to a ciphertext access control method based on multi-chain key generation and distribution. Background Art

[0002] The rapid development of social informatization and networking has led to an explosive growth in the scale of user data. The in-depth application of cloud computing and big data technologies has given rise to data security and privacy protection issues in the open sharing of data resources. Access control technology, as a key technology for protecting data privacy, ensures that only authorized users have access to systems or data, preventing illegal data tampering or leakage. Therefore, how to implement secure and efficient access control to protect personal privacy data has become a key research topic.

[0003] Cipher policy attribute-based encryption (CP-ABE), a new type of public key encryption tool, associates keys with attributes and ciphertexts with access policies. It allows data owners to freely formulate access policies, giving them flexible control over their data and implementing fine-grained, one-to-many encryption access control. This makes it particularly suitable for IoT access control in large-scale environments. Blockchain technology, with its decentralized, publicly verifiable, and tamper-proof characteristics, is becoming the valuable internet infrastructure for trusted computing and storage in the digital economy. The combination of ciphertext access control and blockchain presents tremendous potential, offering new possibilities for resolving the trust and security challenges inherent in data sharing.

[0004] However, with the deepening of research and the advancement of practice, the current blockchain-based CP-ABE ciphertext access control scheme still has some urgent problems to be solved, especially in the face of large-scale data sharing scenarios. These problems not only limit its application in practice, but also affect the scalability and efficiency of the system. Specifically, these problems are mainly reflected in the following two aspects: (1) Centralized management risks and single point failures. All keys and access control policies of the centralized system are centrally managed. Once the server is attacked or fails, the security of the entire system will be seriously threatened; (2) Poor flexibility and scalability. Blockchain technology, especially public chains, usually faces problems such as slow transaction speed, poor scalability and high energy consumption. In the case of a surge in data sharing demand and high-frequency transactions, complex ciphertext operations will cause congestion in the blockchain network and increase transaction processing delays. In addition, if the participation of blockchain nodes is low, it may affect the security and decentralization of the network, making it difficult to meet the needs of different users and different application scenarios. Summary of the Invention

[0005] In order to solve the above problems, the purpose of the present invention is to provide a ciphertext access control method based on multi-chain key generation and distribution to improve the efficiency, security and scalability of key generation and distribution in the existing CP-ABE system.

[0006] To solve the above technical problems, the technical solution adopted by the present invention is a ciphertext access control method based on multi-chain key generation and distribution, comprising the following steps:

[0007] S1. Build a ciphertext access control system;

[0008] S2, user registration and system initialization, the encrypted access control system issues identity identification to all users and initializes the system;

[0009] S3, ciphertext encryption: the data owner formulates an access policy, uses an encryption algorithm to encrypt the data, and uploads the ciphertext;

[0010] S4. The key generation and distribution node determines whether the data user meets the access policy. If so, it generates an attribute private key for the data user.

[0011] S5. Ciphertext decryption: the data user downloads the ciphertext and executes the decryption algorithm to obtain the ciphertext data.

[0012] Furthermore, in step S1, the ciphertext access control system includes:

[0013] Management chain, electing key generation and distribution nodes to enable them to independently manage a set of attributes;

[0014] The functional chain includes key generation and distribution nodes and consensus verification nodes. The key generation and distribution nodes are responsible for key generation and distribution, and issue attribute private keys to data users who meet the access policy. The consensus verification nodes verify the user's identity and check the legitimacy of the transaction.

[0015] The data owner creates an access policy, grants access rights to the data user, and executes the encryption algorithm to encrypt the plaintext data into ciphertext;

[0016] Data users apply for attribute private keys from the key generation and distribution node and execute the decryption algorithm to obtain ciphertext data;

[0017] The InterPlanetary File System provides distributed storage services for all users and publishes the ciphertext storage address to the blockchain, allowing data users to download the ciphertext based on the storage address published on the chain.

[0018] Furthermore, in step S2, the system is initialized as follows:

[0019] The key generation and distribution node generates a security parameter λ and selects the maximum width s of the LSSS matrix based on the security parameter max , s max =s max (λ), set the security matrix Represents an n×m dimensional vector space with q integer elements, q is the modulus, n is the number of rows of the matrix, and m is the number of columns of the matrix. The hash function H is used for mapping to generate the public parameters GP=(n,m,q,s max ,χ lwe ,χ1,χ2,χ big ,B1), where χ lwe is a discrete Gaussian distribution, χ1 is the first normal distribution component, χ2 is the second normal distribution component, and χ big is the normal distribution of discrete Gaussian distribution;

[0020] Setup(GP,H,u)→(PK u ,MSK u ): The key generation and distribution node inputs the public parameter GP, the hash function H and the authority identifier u, and generates the matrix trapdoor pair A u is the trapdoor matrix, is a random matrix, and the sampling matrix H is set u , Output key pair (PK u ,MSK u ), where PK u =(A u ,H u ), PK u is the attribute authority public key, MSK u The attribute authority private key.

[0021] Furthermore, in step S3, the ciphertext is encrypted as:

[0022] Enc(GP,msg,(M,ρ),{PK u})→CT: The data owner inputs the plaintext data msg, public parameters GP, access policy (M, ρ) and attribute authority public key PK u , where M is the access control matrix, ρ is the mapping function, and the output ciphertext is:

[0023]

[0024] Where CT is the ciphertext, x i is a coset element, A ρ(i)is the first trapdoor matrix about ρ(i), ρ(i) is the attribute of the i-th row, s is the control vector, e i is the discrete Gaussian distribution χ lwe The noise in is the noise set, is the first ciphertext component, M i,j is the element in row i and column j in the access control matrix, j is the column corresponding to the attribute, B1 is the security matrix, s max is the maximum width of the LSSS matrix, v j is a random vector, H ρ(i) is the second trapdoor matrix with respect to ρ(i), is the normal distribution of discrete Gaussian distribution χ big The noise in , q is the number of integer elements.

[0025] Furthermore, step S3 further includes:

[0026]

[0027] in, represents an n-dimensional vector space with q integer elements, represents an m-dimensional vector space with q integer elements, is a discrete Gaussian distribution in m dimensions, is the normal distribution of the discrete Gaussian distribution in m dimensions.

[0028] Furthermore, in step S4, the attribute private key is generated as:

[0029] keyGen(GP,H,GID,MSK u )→SK GID,u :Key generation and distribution node input public parameters GP, hash function H, user identity GID, attribute authority private key MSK u , output attribute private key SK GID,u ,include:

[0030]

[0031] SK GID,u ={y GID,u ;u∈N},y GID,u ={y u,1 ,...,y u,N}

[0032] Where y u,i is the attribute key of the i-th row of the authoritative identifier u, RSample is the Gaussian sampling function, S GID is the user attribute set, S GID =∪ u SGID,u , ∪ is the union symbol, S GID,u The set of attributes managed by the authoritative identifier, y GID,u is the attribute key associated with the user and the authority identifier, N is the number of authority identifiers, y u,1 The first row of attribute keys for the authority identifier u.

[0033] Furthermore, in step S5, the ciphertext is decrypted as:

[0034] Dec(GP,H,CT,GID,{SK GID,u})→msg′: The data user inputs the public parameter GP, hash function H, ciphertext CT, user identity GID and attribute private key {SK GID,u}, for the i-th row attribute ρ(i) that meets the decryption condition, ρ(i)∈I, I is the attribute set that meets the decryption condition, let w i is the reconstruction coefficient, Be a vector space with q integer elements such that Π i∈I w i M i =(1,0,...,0), where M i Generate a key for the i-th row element of the access control matrix M c i is the second ciphertext component, is the transposed attribute private key, is the first ciphertext component, Transpose the attribute key of the i-th row of the authority identifier u and output the ciphertext data msg′=C⊕MSB(k′), where C is part of the ciphertext data and MSB is the ciphertext weight.

[0035] The beneficial effects of the present invention are:

[0036] 1. This invention enhances the blockchain system into two layers. The Layer-1 main chain serves as the management chain of the system. Each key generation and distribution node manages a set of attributes to ensure decentralized management of the system. The Layer-2 high-performance chain serves as the functional chain, responsible for key generation and distribution, and achieving traceability and auditability of transaction transmission.

[0037] 2. The present invention adopts MA-CPABE technology. Each function chain node independently manages and distributes keys according to the attribute set it is responsible for, reducing the risks brought by centralized management and ensuring that key fragments can be reconstructed without being leaked.

[0038] 3. This invention achieves decentralized management of keys and access control by designing a multi-chain architecture, avoiding single points of failure and centralization risks, and improving the efficiency and scalability of the blockchain system. The main chain and functional chains jointly achieve traceability and auditability of system operations, enhancing the transparency and credibility of the system. The multi-chain architecture allows the system to be flexibly expanded according to different application scenarios to meet diverse needs, thereby improving the flexibility and scalability of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0040] Figure 1 is a flow chart of the ciphertext access control system of the present invention;

[0041] Figure 2 It is the initialization time overhead test diagram of the present invention;

[0042] Figure 3 It is the actual time cost test graph of the present invention;

[0043] Figure 4 This is a test graph of the average time overhead of the user's overall encryption algorithm of the present invention;

[0044] Figure 5 This is a test chart of the average time overhead in the user decryption phase of the present invention. DETAILED DESCRIPTION

[0045] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0046] The present invention provides a ciphertext access control method based on multi-chain key generation and distribution, comprising the following steps:

[0047] S1. Build a ciphertext access control system, including:

[0048] Management chain Layer-1, electing key generation and distribution nodes to independently manage a set of attributes;

[0049] Functional chain Layer-2 includes key generation and distribution nodes and consensus verification nodes. The key generation and distribution nodes are responsible for key generation and distribution, issuing attribute private keys to data users who meet the access policy by executing algorithms; the consensus verification nodes verify the user's identity, check the legitimacy of the transaction, and achieve transaction traceability and auditability;

[0050] The data owner creates an access policy, grants access rights to the data user, and executes the encryption algorithm to encrypt the plaintext data into ciphertext;

[0051] When the data user meets the access policy, he applies to the key generation and distribution node to obtain the attribute private key to execute the decryption algorithm to obtain the ciphertext data.

[0052] The InterPlanetary File System provides distributed storage services for all users and publishes the ciphertext storage address to the blockchain, allowing data users to download the ciphertext based on the storage address published on the chain.

[0053] S2, user registration and system initialization;

[0054] All users in the system register their identities on the Layer-1 main chain, and identity identifiers are issued to data owners and data users. The key generation and distribution node obtains the public parameter GP from the Layer-1 main chain and initializes the system. The process is as follows:

[0055] The key generation and distribution node generates a security parameter λ and selects the maximum width s of the LSSS matrix based on the security parameter max , s max =s max (λ), set the security matrix Represents an n×m dimensional vector space with q integer elements, q is the modulus, n is the number of rows of the matrix, and m is the number of columns of the matrix. The hash function H is used for mapping to generate the public parameters GP=(n,m,q,s max ,χ lwe ,χ1,χ2,χ big ,B1), where χ lwe is a discrete Gaussian distribution, χ1 is the first normal distribution component, χ2 is the second normal distribution component, and χ big is a normal distribution of discrete Gaussian distribution.

[0056] Setup(GP,H,u)→(PK u ,MSK u ): The key generation and distribution node inputs the public parameter GP, the hash function H and the authority identifier u, and generates the matrix trapdoor pair A u is the trapdoor matrix, is a random matrix, and the sampling matrix H is set u , Output key pair (PK u ,MSK u ), where PK u =(A u ,H u ), PK u is the attribute authority public key, MSK u The attribute authority private key.

[0057] S3, ciphertext encryption: The data owner formulates an access policy, uses an encryption algorithm to encrypt the data, and uploads the ciphertext. Specifically:

[0058] Enc(GP,msg,(M,ρ),{PK u})→CT: The data owner inputs the plaintext data msg∈{0,1}, the public parameter GP, the access policy (M,ρ) and the attribute authority public key PK u , where M is the access control matrix, ρ is the mapping function, and the control vector is selected:

[0059]

[0060] Where s is the control vector, represents an n-dimensional vector space with q integer elements, v j is a random vector, s max is the maximum width of the LSSS matrix, represents an m-dimensional vector space with q integer elements, e i is the discrete Gaussian distribution χ lwe The noise in is the noise set, is a discrete Gaussian distribution in m dimensions, is the normal distribution of the discrete Gaussian distribution in m dimensions.

[0061] Output ciphertext CT:

[0062]

[0063] Where x i is a coset element, A ρ(i) is the first trapdoor matrix about ρ(i), ρ(i) is the attribute of the i-th row, is the first ciphertext component, M i,j is the element in row i and column j in the access control matrix, where j is the column corresponding to the attribute, and H ρ(i) is the second trapdoor matrix with respect to ρ(i), is the normal distribution of discrete Gaussian distribution χ big The noise in , q is the number of integer elements.

[0064] S4. The key generation and distribution node determines whether the data user meets the access policy. If so, it generates an attribute private key for the data user. Specifically:

[0065] keyGen(GP,H,GID,MSK u )→SK GID,u :Key generation and distribution node input public parameters GP, hash function H, user identity GID, attribute authority private key MSK u , output attribute private key SK GID,u ,include:

[0066]

[0067] SK GID,u ={y GID,u ;u∈N},y GID,u ={y u,1 ,...,y u,N}

[0068] Where y u,i is the attribute key of the i-th row of the authoritative identifier u, RSample is the Gaussian sampling function, S GID is the user attribute set, S GID =∪ u S GID,u , ∪ is the union symbol, S GID,u The set of attributes managed by the authoritative identifier, y GID,u is the attribute key associated with the user and the authority identifier, N is the number of authority identifiers, y u,1 The first row of attribute keys for the authority identifier u.

[0069] S5. Ciphertext decryption: The data user downloads the ciphertext and executes the decryption algorithm to obtain the ciphertext data, including:

[0070] Dec(GP,H,CT,GID,{SK GID,u})→msg′: The data user inputs the public parameter GP, hash function H, ciphertext CT, user identity GID and attribute private key {SK GID,u}, for the i-th row attribute ρ(i) that meets the decryption condition, ρ(i)∈I, I is the attribute set that meets the decryption condition, let w i is the reconstruction coefficient, is a vector space with q integer elements, such that ∑ i∈I w i M i=(1,0,...,0), where M i Generate a key for the i-th row element of the access control matrix M c i is the second ciphertext component, is the transposed attribute private key, Transpose the attribute key of the i-th row of the authority identifier u and output the ciphertext data msg′=C⊕MSB(k′), where C is the partial ciphertext and MSB is the ciphertext weight.

[0071] like Figure 1 As shown, it is a model diagram of the ciphertext access control system of the present invention.

[0072] The ciphertext access control method based on multi-chain key generation and distribution proposed in this paper is used for experimental simulation analysis. The experimental simulation host is (Intel Core i5-8265U CPU@1.60GHz), the management chain Layer-1 is implemented based on Ethereum, and the function chain Layer-2 is set as an Ethereum compatible chain. The method is compared with the methods proposed in the existing solutions [1], [2], [3], and [4]. Each experiment is repeated 30 times and the average value is taken as the experimental result.

[0073] The specific solutions [1], [2], [3], and [4] are:

[0074] [1] C. Zhao, L. Xu, J. Li, H. Fang, Y. Zhang. Toward Secure and Privacy-Preserving Cloud Data Sharing: Online / Offline Multiauthority CP-ABE WithHidden Policy. IEEE Systems Journal, DOI: 10.1109 / JSYST.2022.3169601.

[0075] [2] Liu.J, Li.Y, Sun.R, et al. SDSS: Secure Data Sharing Scheme for EdgeEnabled IoV Networks[J]. IEEE Transactions on Intelligent TransportationSystems, 2023, 24(11):12038-12049.

[0076] [3] Gao.J, Yu.H, Zhu.X, et al. Blockchain-based digital rights management scheme via multiauthority ciphertext-policy attribute-based encryption and proxyre-encryption[J]. IEEE Systems Journal, 2021, 15(4): 5233-5244.

[0077] [4]Z.Guo, G.Wang, Y.Li, J.Ni, R.Du and M.Wang.Accountable Attribute-BasedData-Sharing Scheme Based on Blockchain for Vehicular Ad Hoc Network[J].IEEEInternet ofThings Journal, vol.10, no.8, pp.7011-7026, 15April15, 2023, doi: 10.1109 / JIOT.2022.3228550.

[0078] Figure 2 This is a test graph of initialization time cost. By testing the actual performance of the key generation distribution node / attribute authority node initialization algorithm, the attribute scale managed by KGD / AA is set to 0-90 with a step size of 10, and the average initialization time cost of different schemes is tested. As can be seen from the figure, the time cost of KGD / AASetup in all the above schemes is constant. In comparison, the initialization time cost of the present invention is lower than that of schemes [2], [3], and [4], and slightly higher than that of scheme [1].

[0079] Figure 3 This is a graph showing actual time cost testing. The average time cost of the KeyGen algorithm for different schemes was tested, with the user attribute set size set from 0 to 90, in a step size of 10. As can be seen from the graph, the time cost of the key generation algorithm for all the above schemes is linearly correlated with the number of user attributes, with the proposed method having the lowest actual time cost.

[0080] Figure 4The average time cost test graph of the user's overall encryption algorithm is shown in the figure. The number of rows of the access matrix is set to 0 to 90, with a step size of 10, and the average time cost of the user's overall encryption algorithm of different schemes is tested. As can be seen from the figure, the overall encryption time cost of the present invention is similar to that of schemes [1] and [4]. Although schemes [1], [2], and [4] all introduce online / offline encryption methods to improve online encryption efficiency, the overall computing cost of the user itself is not reduced.

[0081] Figure 5 The figure shows the average time cost test of the user decryption phase. It can be seen from the figure that the decryption time cost of the present invention, scheme [1] and scheme [2] are all linearly related to the attribute size in the decryption key, and the decryption cost of scheme [3] and scheme [4] are all constant. The user decryption time cost of the present invention is lower than the computational cost generated by scheme [1]. This is because schemes [2-4] reduce the user decryption cost by introducing trusted proxy nodes with strong computing power or outsourcing the decryption process to pre-decrypt the ciphertext, while the present invention does not entrust the decryption process to a trusted third party. Therefore, the user decryption cost of the present invention is slightly higher in comparison.

[0082] Each embodiment in this specification is described in a related manner. Similar parts between the various embodiments can be referred to in conjunction with each other. Each embodiment focuses on the differences between the other embodiments. In particular, the system embodiment is generally similar to the method embodiment, so the description is relatively simple. For related parts, refer to the description of the method embodiment.

[0083] The above description is only a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention are included in the scope of protection of the present invention.

Claims

1. A ciphertext access control method based on multi-chain key generation and distribution, characterized in that: The following steps are involved: S1. Build a ciphertext access control system; S2, user registration and system initialization, the encrypted access control system issues identity identification to all users and initializes the system; S3, ciphertext encryption: the data owner formulates an access policy, uses an encryption algorithm to encrypt the data, and uploads the ciphertext; S4. The key generation and distribution node determines whether the data user meets the access policy. If so, it generates an attribute private key for the data user. S5, ciphertext decryption, the data user downloads the ciphertext and executes the decryption algorithm to obtain the ciphertext data; In step S2, the system is initialized as follows: The key generation and distribution node generates a security parameter λ and selects the maximum width s of the LSSS matrix based on the security parameter max , s max =s max (λ), set the security matrix Represents an n×m dimensional vector space with q integer elements, q is the modulus, n is the number of rows of the matrix, and m is the number of columns of the matrix. The hash function H is used for mapping to generate the public parameters GP=(n,m,q,s max ,χ lwe ,χ1,χ2,χ big ,B1), where χ lwe is a discrete Gaussian distribution, χ1 is the first normal distribution component, χ2 is the second normal distribution component, and χ big is the normal distribution of discrete Gaussian distribution; Setup(GP,H,u)→(PK u ,MSK u ): The key generation and distribution node inputs the public parameter GP, the hash function H and the authority identifier u, and generates the matrix trapdoor pair A u is the trapdoor matrix, is a random matrix, and the sampling matrix H is set u , Output key pair (PK u ,MSK u ), where PK u =(A u ,H u ), PK u is the attribute authority public key, MSK u is the attribute authority private key; In step S3, the ciphertext is encrypted as: Enc(GP,msg,(M,ρ),{PK u })→CT: The data owner inputs the plaintext data msg, public parameters GP, access policy (M, ρ) and attribute authority public key PK u , where M is the access control matrix, ρ is the mapping function, and the output ciphertext is: Where CT is the ciphertext, x i is a coset element, A ρ(i) is the first trapdoor matrix about ρ(i), ρ(i) is the attribute of the i-th row, s is the control vector, e i is the discrete Gaussian distribution χ lwe The noise in is the noise set, is the first ciphertext component, M i,j is the element in row i and column j in the access control matrix, where j is the column corresponding to the attribute, and v j is a random vector, H ρ(i) is the second trapdoor matrix with respect to ρ(i), is the normal distribution of discrete Gaussian distribution χ big Noise in In step S3, the ciphertext encryption further includes: in, represents an n-dimensional vector space with q integer elements, represents an m-dimensional vector space with q integer elements, is a discrete Gaussian distribution in m dimensions, is the normal distribution of the discrete Gaussian distribution in m dimensions; In step S4, the attribute private key is generated as: keyGen(GP,H,GID,MSK u )→SK GID,u :Key generation and distribution node input public parameters GP, hash function H, user identity GID, attribute authority private key MSK u , output attribute private key SK GID,u ,include: SK GID,u ={and GID,u ;u∈N},y GID,u ={and u,1 ,...,and u,N } Where y u,i is the attribute key of the i-th row of the authoritative identifier u, RSample is the Gaussian sampling function, S GID is the user attribute set, S GID =∪ u S GID,u , ∪ is the union symbol, S GID,u The set of attributes managed by the authoritative identifier, y GID,u is the attribute key associated with the user and the authority identifier, N is the number of authority identifiers, y u,1 The first row attribute key of the authority identifier u; In step S5, the ciphertext is decrypted as: Dec(GP,H,CT,GID,{SK GID,u })→msg′: The data user inputs the public parameter GP, hash function H, ciphertext CT, user identity GID and attribute private key {SK GID,u }, for the i-th row attribute ρ(i) that meets the decryption condition, ρ(i)∈I, I is the attribute set that meets the decryption condition, let w i is the reconstruction coefficient, is a vector space with q integer elements, such that ∑ i∈I w i M i =(1,0,...,0), where M i Generate a key for the i-th row element of the access control matrix M c i is the second ciphertext component, is the transposed attribute private key, Transpose the attribute key for the i-th row of the authority identifier u and output the ciphertext data Where C is part of the ciphertext data, and MSB is the ciphertext weight.

2. The ciphertext access control method based on multi-chain key generation and distribution according to claim 1 is characterized in that: In step S1, the ciphertext access control system includes: Management chain, electing key generation and distribution nodes to enable them to independently manage a set of attributes; The functional chain includes key generation and distribution nodes and consensus verification nodes. The key generation and distribution nodes are responsible for key generation and distribution, and issue attribute private keys to data users who meet the access policy. The consensus verification nodes verify the user's identity and check the legitimacy of the transaction. The data owner creates an access policy, grants access rights to the data user, and executes the encryption algorithm to encrypt the plaintext data into ciphertext; Data users apply for attribute private keys from the key generation and distribution node and execute the decryption algorithm to obtain ciphertext data; The InterPlanetary File System provides distributed storage services for all users and publishes the ciphertext storage address to the blockchain, allowing data users to download the ciphertext based on the storage address published on the chain.

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