A method and system for supporting hierarchical authorization of ciphertext search

Abstract

The application discloses a kind of ciphertext search method and system supporting hierarchical authorization, including two parts of hierarchical authorization method and dynamic security ciphertext search method;The hierarchical authorization method includes two modes of online authorization and offline authorization, solves the problem that existing scheme cannot be applied to hierarchical structure user, gets rid of the demand of real-time online authorization to data owner, the invention realizes the dynamic fine-grained authorization and reauthorization of encrypted file, and has file storage overhead independent of the number of authorization, so that system efficiency is significantly improved.The dynamic security ciphertext search method solves the security problem caused by the leakage of dynamic operation, and the invention realizes forward security, so that the system security is significantly improved.The ciphertext search method provided by the application does not depend on trusted third party, and the authorization efficiency is high and is executed by internal legal user, especially suitable for practical application scenarios of company, hospital and other hierarchical structure users.

Description

Technical Field

[0001] This invention belongs to the field of encrypted retrieval technology in applied cryptography, and relates to a multi-user dynamic secure encrypted retrieval method and system, specifically to an encrypted retrieval method and system that supports hierarchical authorization. Background Technology

[0002] With the development of cloud storage technology, individuals and businesses can outsource their data to cloud storage platforms, alleviating resource constraints on physical media such as local hard drives. Since individuals and businesses handle a large amount of sensitive data, storing it in plaintext on cloud servers poses security risks such as information leakage and tampering. Therefore, users often choose to encrypt and store it on cloud servers. However, while ensuring confidentiality, encryption reduces availability, making it difficult for users to directly update and retrieve encrypted data. This problem has attracted widespread attention from the academic community. To achieve the updating and retrieval of encrypted cloud data, dynamic encrypted retrieval technology has emerged. This technology allows cloud servers to retrieve updatable encrypted data upon receiving a query request, while maintaining both data confidentiality and availability, even in encrypted form.

[0003] Early dynamic encrypted retrieval schemes, operating under a single-user model, focused on improving search efficiency, supporting richer query expressions, and enhancing security. However, these schemes were only suitable for scenarios where personal data was outsourced and maintained and retrieved by the individual, and not for multi-user scenarios within enterprises involving file sharing and authorized retrieval. In reality, for example, in an enterprise's data center, file data is allocated different access and retrieval permissions based on the nature of different departments and the functions of different employees. Employees can only search within the scope of their authorized access, and the data center can dynamically maintain encrypted file data and authorization information as needed. In such cases, adopting a single-user model would allow any employee to access and retrieve sensitive files within the enterprise, increasing the risk of sensitive information leakage.

[0004] Existing multi-user dynamic encrypted retrieval schemes do not support scenarios with hierarchical user structures, such as those in enterprises and hospitals. Furthermore, current designs have significant room for improvement in efficiency, functionality, and security. Therefore, how to achieve efficient and secure retrieval, and implement hierarchical authorization in multi-user scenarios, is a pressing issue that needs to be addressed in this field. Summary of the Invention

[0005] In view of the drawbacks of data access in single-user scenarios mentioned above, as well as the needs for data privacy and security, efficiency and availability, hierarchical authorization in multi-user scenarios, and dynamic encrypted retrieval, this invention provides an encrypted retrieval method and system that supports hierarchical authorization.

[0006] The technical solution adopted by the method of the present invention is: a encrypted retrieval method that supports hierarchical authorization, wherein the participating entities include data owners, data users and cloud servers;

[0007] The method includes a hierarchical authorization method and a dynamic secure encrypted text retrieval method;

[0008] The hierarchical authorization method includes:

[0009] During the initialization phase, the security parameter λ is input, the key SK and the cyclic group parameter are generated, and the authorization index (USet, ASet) is initialized. The key is kept by the data owner, the cyclic group parameter is publicly provided to the participating entities, and the authorization index is uploaded to the cloud server. USet is the online authorization index, and ASet is the offline authorization index.

[0010] During the data user registration phase, the data owner distributes the data user's exclusive key UK, initializes the authorization status information ST, and provides the exclusive key and authorization status information to the data user to complete the registration;

[0011] During the online authorization phase, the data owner authorizes a set of files that a data user can access, calculates a file key set generated from the identifier d of each authorized file, and the online authorization information bound to the data user's identity for each d, and then sends the file key set... K in d and The file key and its corresponding d are sent to the data user, and the online authorization information is sent to the cloud server; the data user receives the file key and its corresponding authorized file identifier, and updates the local authorization status information ST; the cloud server receives the online authorization information and updates the received data to the online authorization index USet stored on it;

[0012] During the offline authorization phase, authorized data users authorize the set of files accessible to their subordinate data users, calculate the offline authorization information bound to their own and subordinate user identities, and the offline authorization token bound to their own and subordinate data user identities for each authorized file identifier d. They then send the offline authorization token, file key, and offline authorization information index number to the subordinate data users and send the offline authorization information to the cloud server. The subordinate data users update their local authorization status information ST with the received data; the cloud server updates its stored offline authorization index ASet with the received data.

[0013] The dynamic secure encrypted retrieval method includes:

[0014] During the initialization phase, the security parameter λ is input to generate the key SK and the cyclic group parameters. Initialize the search index XSet, where the key is kept by the data owner, the circular group parameter is publicly provided to the participating entities, and the search index is uploaded to the cloud server.

[0015] During the encrypted data update phase, the data owner calculates the index number and encrypted value of the file identifier for each keyword / file identifier pair (w,d) in the search index for the updated file set DOC, and sends these index numbers and corresponding encrypted values ​​to the cloud server; when the cloud server receives the encrypted data update request sent by the data owner, it updates the received data to the search index XSet stored on it.

[0016] During the keyword encryption query phase, the data user generates a search token based on the keywords and authorization information they need to search for, and sends it to the cloud server. The cloud server performs a search operation within the set of files authorized for access by the data user without decryption, and returns the search results to the data user. After receiving the returned search results, the data user decrypts them and finally obtains the set of all file identifiers d that meet the search requirements.

[0017] Preferably, in the hierarchical authorization method, during the initialization phase, a security parameter λ∈N is input, and a key SK=(K1,K2,K3) is generated, where K1,K2,K3∈{0,1}. λ The key is randomly selected and kept by the data owner; cyclic group parameters are generated. Where p is a cyclic group The prime order of g, and g is a cyclic group. The generator is publicly provided to participating entities, including data users and cloud servers; the online authorization index USet and the offline authorization index ASet are initialized and uploaded to the cloud server.

[0018] Preferably, in the hierarchical authorization method, during the data user registration phase, the data owner distributes its exclusive key to the data user u. in For a randomly selected user key, initialize the authorization status information ST = (UAuth, DocKey, aid), where UAuth is the user's offline authorization token index, DocKey is the user's authorization file key index, and aid is the offline authorization information index number. Then, provide the exclusive key UK and the authorization status information ST to the data user u to complete the registration.

[0019] Preferably, in the hierarchical authorization method, during the online authorization phase, the data owner authorizes a set of files that data user u can access, and calculates a file key set generated by the identifier d of each authorized file. Where K d =F(K1,d), F:{0,1}λ ×{0,1} * →{0,1} Θ(λ) It is a pseudo-random function that outputs a field of order p. The elements of length Θ(λ) in the middle, G:{0,1} λ ×{0,1} * →{0,1} λ It is a pseudo-random function that outputs a string of length λ; it will also output a portion of the file key. The corresponding d is sent to the data user u, and the online authorization information (uid) bound to the data user u for each d is calculated. u,d U u,d ), including the online authorization information index number Index value The online authorization information is sent to the cloud server; the data user receives the file key and its corresponding set of authorized file identifiers. Update the local authorization status information ST; the cloud server will receive the online authorization information data {(uid)} u,d U u,d Update to the online authorization index USet stored on it.

[0020] Preferably, in the hierarchical authorization method, during the offline authorization phase, the authorized data user u A For its subordinate data users u B The set of files that can be authorized for access is used to calculate the offline authorization information (aid, α) that binds the user's identity to its own and the user's lower-level data, where the offline authorization information index number is... Index value Send the offline authorization information to the cloud server, and send the offline authorization information index number (AID) to the lower-level data user (U). B ; Calculate the file identifier d for each authorized access file with respect to itself and its subordinate data users u. B An offline authorization token bound to an identity, when an authorized user u A An offline authorization token is issued when the data owner authorizes online. Otherwise, from authorized user u A Retrieve the offline authorization token (offtok) corresponding to the authorized file d from the local authorization status information ST, and recalculate the offline authorization token. Send the offline authorization token to the lower-level data user u B From authorized user u A Retrieve the set of file keys corresponding to the set of authorized files from the local authorization status information ST. Send the authorization file key set to the lower-level data user u B Lower-level data user uB The received data is updated to the local authorization status information ST; the cloud server updates the received data to the offline authorization index ASet stored on it.

[0021] Preferably, in the dynamic secure encrypted retrieval method, during the initialization phase, a security parameter λ∈N is input, and a key SK=(K1,K2,K3) is generated, where K1,K2,K3∈{0,1} λ The key is randomly selected and kept by the data owner; cyclic group parameters are generated. Where p is a cyclic group The prime order of g, and g is a cyclic group. The generator is publicly provided to participating entities, including data users and cloud servers; the search index XSet is initialized and uploaded to the cloud server.

[0022] Preferably, in the dynamic secure encrypted retrieval method, during the encrypted data update phase, the data owner calculates a file key group for each file identifier d in the updated file set DOC. Where K d =F(K1,d), F:{0,1} λ ×{0,1} * →{0,1} Θ(λ) It is a pseudo-random function that outputs a field of order p. The elements of length Θ(λ) in the middle, G:{0,1} λ ×{0,1} * →{0,1} λ It is a pseudo-random function that outputs a string of length λ; for each keyword / file identifier pair (w, d), calculate its index number X in the search index. w,d and the encrypted value Y of the file identifier w,d ,in These index numbers and their corresponding encrypted values ​​are then sent to the cloud server; when the cloud server receives a request to update encrypted data from the data owner, it updates the received data to the search index XSet stored on it.

[0023] Preferably, in the dynamic secure encrypted retrieval method, during the keyword encryption query phase, data user u calculates the retrieval token set {stk} based on the keyword w to be retrieved and the authorization status information ST. d When data user u is a user authorized online by the data owner, otherwise, The `offtok` is the offline authorization token retrieved from the local authorization status information `ST` on the user's device. This token is then sent to the cloud server. The cloud server performs a search operation within the set of files authorized for access by the user without decryption, and calculates... and x ASet[aid] Does it match in the search index? If it does, return the corresponding index value y. d The search result is given to data user u; after receiving the returned search result, data user u decrypts it and calculates... Finally, the set Res of all file identifiers d that meet the search requirements is obtained.

[0024] The technical solution adopted by the system of the present invention is: a encrypted retrieval system supporting hierarchical authorization, comprising:

[0025] One or more processors;

[0026] A storage device for storing one or more programs that, when executed by one or more processors, cause the one or more processors to implement the encrypted retrieval method supporting hierarchical authorization.

[0027] Compared with the prior art, the advantages and positive effects of this invention are mainly reflected in the following aspects:

[0028] (1) This invention proposes a ciphertext retrieval method that supports hierarchical authorization. The method designs a hierarchical authorization method suitable for hierarchical users, including online authorization and offline authorization modes. It eliminates the need for real-time online authorization by data owners, realizes dynamic fine-grained authorization and re-authorization of encrypted files, and has file storage overhead that is independent of the number of authorizations. The authorization operations are all performed by internal legitimate users without relying on trusted third parties, avoiding unnecessary interaction rounds and significantly improving system efficiency.

[0029] (2) The present invention provides a dynamic secure encrypted retrieval method. This method generates different file key groups for different files, which solves the security problem of leakage caused by dynamic operation, realizes dynamic data updateability and forward security of the retrieval process, and improves system security. Attached Figure Description

[0030] The technical solutions described herein are further illustrated below using examples and specific implementation methods. Additionally, accompanying drawings are used in the description of the technical solutions. Those skilled in the art can, without any creative effort, obtain other drawings and the intent of the present invention based on these drawings.

[0031] Figure 1 This is a system framework diagram in an embodiment of the present invention;

[0032] Figure 2 This is a schematic diagram of the hierarchical authorization method in an embodiment of the present invention;

[0033] Figure 3 This is a schematic diagram of the dynamic secure encrypted text retrieval method in an embodiment of the present invention. Detailed Implementation

[0034] To facilitate understanding and implementation of the present invention by those skilled in the art, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0035] Please see Figure 1 The present invention provides a method for encrypted retrieval that supports hierarchical authorization, which is applied to a multi-user encrypted retrieval system with a hierarchical structure; the participating entities include data owners, data users and cloud servers.

[0036] Please see Figure 2 The hierarchical authorization method provided in this embodiment of the invention includes the following specific implementation process:

[0037] During the system initialization phase, the security parameter λ∈N is input, and the key SK=(K1,K2,K3) is generated, where K1,K2,K3∈{0,1} λ The key is randomly selected and kept by the data owner; cyclic group parameters are generated. Where p is a cyclic group The prime order of g, and g is a cyclic group. The generator is publicly provided to participating entities, including data users and cloud servers; the online authorization index USet and the offline authorization index ASet are initialized and uploaded to the cloud server.

[0038] During the data user registration phase, the data owner distributes a unique key to the data user u. in For a randomly selected user key, initialize the authorization status information ST = (UAuth, DocKey, aid), where UAuth is the user's offline authorization token index, DocKey is the user's authorization file key index, and aid is the offline authorization information index number. Then, provide the exclusive key UK and the authorization status information ST to the data user u to complete the registration.

[0039] During the online authorization phase, the data owner authorizes the data user u to access a set of files, and calculates a file key set generated from the identifier d of each authorized file. Where K d =F(K1,d), F:{0,1}λ ×{0,1} * →{0,1} Θ(λ) It is a pseudo-random function that outputs a field of order p. The elements of length Θ(λ) in the middle, G:{0,1} λ ×{0,1} * →{0,1} λ It is a pseudo-random function that outputs a string of length λ, which contains a portion of the file key. The corresponding d is sent to data user u; the online authorization information (uid) bound to the data user u for each d is calculated. u,d U u,d ), including the online authorization information index number Index value The online authorization information is sent to the cloud server; the data user receives the file key and its corresponding set of authorized file identifiers. Update the local authorization status information ST; the cloud server will receive the online authorization information data {(uid)} u,d U u,d Update to the online authorization index USet stored on it.

[0040] During the offline authorization phase, authorized data user u A For its subordinate data users u B The set of files that can be authorized for access is used to calculate the offline authorization information (aid, α) that binds the user's identity to its own and the user's lower-level data, where the offline authorization information index number is... The index value \alpha = F\left(K_{u_A},u_B\rigt)^{-1} is used to send the offline authorization information to the cloud server, and the offline authorization information index number aid is sent to the lower-level data user u. B ; Calculate the file identifier d for each authorized access file with respect to itself and its subordinate data users u. B An offline authorization token bound to an identity, when an authorized user u A An offline authorization token is issued when the data owner authorizes online. Otherwise, from authorized user u A Retrieve the offline authorization token (offtok) corresponding to the authorized file d from the local authorization status information ST, and recalculate the offline authorization token. Send the offline authorization token to the lower-level data user u B From authorized user u A Retrieve the set of file keys corresponding to the set of authorized files from the local authorization status information ST. Send the authorization file key set to the lower-level data user u BLower-level data user u B The received data is updated to the local authorization status information ST; the cloud server updates the received data to the offline authorization index ASet stored on it.

[0041] Please see Figure 3 The dynamic secure encrypted text retrieval method provided in this embodiment of the invention includes the following specific implementation process:

[0042] During the system initialization phase, the security parameter λ∈N is input, and the key SK=(K1,K2,K3) is generated, where K1,K2,K3∈{0,1} λ The key is randomly selected and kept by the data owner; cyclic group parameters are generated. Where p is a cyclic group The prime order of g, and g is a cyclic group. The generator is publicly provided to participating entities, including data users and cloud servers; the search index XSet is initialized and uploaded to the cloud server.

[0043] During the encrypted data update phase, the data owner calculates the file key set for each file identifier d in the updated file set DOC. Where K d =F(K1,d), For each keyword / file identifier pair (w,d), calculate its index number X in the search index. w,d and the encrypted value Y of the file identifier w,d ,in These index numbers and their corresponding encrypted values ​​are then sent to the cloud server; when the cloud server receives a request to update encrypted data from the data owner, it updates the received data to the search index XSet stored on it.

[0044] During the keyword encryption query phase, data user u calculates the retrieval token set {stk} based on the keyword w they need to search for and the authorization status information ST. d When data user u is a user authorized online by the data owner, otherwise, The `offtok` is the offline authorization token retrieved from the local authorization status information `ST` on the user's device. This token is then sent to the cloud server. The cloud server performs a search operation within the set of files authorized for access by the user without decryption, and calculates... and x ASet[aid] Does it match in the search index? If it does, return the corresponding index value y. d The search results are returned to data user u; after receiving the returned search results, data user u decrypts them and calculates... Finally, the set Res of all file identifiers d that meet the search requirements is obtained.

[0045] This embodiment also provides a encrypted retrieval system that supports hierarchical authorization, including:

[0046] One or more processors;

[0047] A storage device for storing one or more programs that, when executed by one or more processors, cause the one or more processors to implement the encrypted retrieval method supporting hierarchical authorization.

[0048] The invention will be further illustrated by the following experiments.

[0049] This embodiment conducted extensive experimental analysis and randomly extracted subsets of different sizes from the original Enron dataset to evaluate the computational overhead of ciphertext retrieval supporting hierarchical authorization in terms of server storage, authorization phase computation, ciphertext update phase computation, and keyword encryption query phase computation. The specific analysis is as follows:

[0050] The relevant experimental environment is as follows: This experiment uses the relic library and C++ to implement the technical solution. The pseudo-random function is instantiated using HMAC, the symmetric encryption algorithm is instantiated using AES-128, and the group computation is instantiated using NIST-256 elliptic curve cryptography. All tests were conducted on a Linux Ubuntu 18.04.5 server, which has an Intel Xeon Gold5218 CPU@2.30GHz and 32GB of RAM.

[0051] (1) This experimental analysis is based on the commonly used Enron email dataset. Based on the number of keyword pairs, different sizes of subsets were first extracted, as shown in Table 1 below:

[0052] Table 1: Subdataset Extraction Status

[0053] Number of files 1000 5000 10000 502005 Number of keywords 8756 25057 32893 333619 (Keywords, document) number 32359 194156 574270 21206546

[0054] (2) For the different subsets extracted above, the storage overhead of the hierarchical authorization and encrypted retrieval data structures of this invention on the server was analyzed, and further compared with existing technologies. The server storage overhead of this invention is the lowest, requiring only 2.8GB for the complete Enron dataset. The storage overhead based on the unintentional mapping technique increases continuously with the size of the dataset, and is significantly greater than that of this invention. Running the unintentional mapping technique on the complete Enron dataset would take more than a week; this experimental data is omitted in this study. The storage overhead based on the RSA function technique also increases continuously with the size of the dataset, requiring 3.5GB of storage when the complete Enron dataset is reached. Clearly, the storage efficiency of this invention is superior. Relevant experimental test data are shown in Table 2.

[0055] Table 2: Comparison of Server Storage Overhead

[0056]

[0057] (3) The client-side computation time overhead during the authorization stage of this invention was tested and analyzed, and compared with existing technologies. When the number of authorized files increased from 100 to 1000, the authorization time overhead of existing schemes based on unintentional mapping technology increased from 5.731 seconds to 50.950 seconds, and the authorization time overhead of schemes based on RSA function technology increased from 11.200 seconds to 61.302 seconds. In this invention, the online authorization time increased from 0.008 seconds to 0.077 seconds, and the offline authorization time increased from 0.055 seconds to 0.549 seconds. The efficiency of both online and offline authorization is significantly optimal. The relevant experimental test data are shown in Table 3.

[0058] Table 3: Comparison of computation time overhead during the authorization phase (unit: seconds)

[0059]

[0060]

[0061] (4) The client-side computation time overhead of the encrypted update stage of the present invention was tested and analyzed, and compared with existing technologies. The computation time overhead of the encrypted update stage in the present invention is the lowest, requiring only 3.23 hours for the complete Enron dataset. The storage overhead based on the unintentional mapping technique increases continuously with the size of the dataset, requiring 15.13 hours of computation when the complete Enron dataset is reached. The storage overhead based on the RSA function technique also increases continuously with the size of the dataset, requiring 10.63 hours of computation when the complete Enron dataset is reached. Clearly, the encrypted update efficiency of the present invention is more advantageous. Relevant experimental test data are shown in Table 4.

[0062] Table 4: Comparison of computation time overhead during the ciphertext update phase

[0063]

[0064] (5) The end-to-end search time overhead of the keyword encryption query stage of the present invention was tested and analyzed, and compared with existing technologies. When the number of authorized files increases from 100 to 1000, the end-to-end search time overhead of existing solutions based on unintentional mapping technology is independent of the number of authorized files. Due to the acceptable error fluctuation of network transmission around 0.005 seconds, the end-to-end search time overhead of the RSA function-based solution increases from 27.201 seconds to 141.302 seconds. In the present invention, the end-to-end search time for online authorized users increases from 0.150 seconds to 1.195 seconds, and the end-to-end search time for offline authorized users increases from 0.209 seconds to 1.852 seconds. The search efficiency of the present invention is significantly better than that of the RSA function-based solution for both online and offline authorized users. When the number of users increases, the authorization and search time and storage amortization performance of the unintentional mapping technology solution are not as good as those of the present invention. Therefore, the present invention is more suitable for large-scale user scenarios in practical applications than the unintentional mapping technology solution, and can provide users with a better search experience. The relevant experimental test data are shown in Table 5.

[0065] Table 5: Comparison of End-to-End Search Time Costs (Unit: seconds)

[0066]

[0067] This invention addresses the problem of hierarchical authorization in encrypted retrieval within multi-user scenarios. It designs a hierarchical authorization method suitable for hierarchical user structures, including both online and offline authorization modes. This eliminates the need for real-time online authorization from data owners, enabling dynamic, fine-grained authorization and re-authorization of encrypted files with file storage overhead independent of the number of authorization cycles. Authorization operations are performed by legitimate internal users without relying on trusted third parties, avoiding unnecessary interaction rounds and significantly improving system efficiency. In the field of encrypted retrieval, this method generates different file key sets for different files, solving the security problem of potential data leakage caused by dynamic operations. It achieves dynamic data updateability and forward security in the retrieval process, improving system security.

[0068] This invention can provide users with a reliable and secure hierarchical authorized encrypted text retrieval method in more fields such as cloud storage, data security, and access control.

[0069] It should be understood that the embodiments described above are only some, not all, of the embodiments of the present invention. Furthermore, the technical features of the various embodiments or individual embodiments provided by the present invention can be arbitrarily combined to form feasible technical solutions. Such combinations are not constrained by the order of steps and / or structural composition patterns, but must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0070] It should be understood that the above description of the preferred embodiments is quite detailed, but it should not be considered as a limitation on the scope of protection of this invention. Those skilled in the art, under the guidance of this invention, can make substitutions or modifications without departing from the scope of protection of the claims of this invention, and all such substitutions or modifications fall within the scope of protection of this invention. The scope of protection of this invention should be determined by the appended claims.

Claims

1. A method for encrypted retrieval that supports hierarchical authorization, wherein participating entities include data owners, data users, and cloud servers; Its features are: The method includes a hierarchical authorization method and a dynamic secure encrypted text retrieval method; The hierarchical authorization method includes: During the initialization phase, the security parameter λ is input, the key SK and the cyclic group parameter are generated, and the authorization index (USet, ASet) is initialized. The key is kept by the data owner, the cyclic group parameter is publicly provided to the participating entities, and the authorization index is uploaded to the cloud server. USet is the online authorization index, and ASet is the offline authorization index. During the data user registration phase, the data owner distributes the data user's exclusive key UK, initializes the authorization status information ST, and provides the exclusive key and authorization status information to the data user to complete the registration; During the online authorization phase, the data owner authorizes a set of files that a data user can access, calculates a file key set generated from the identifier d of each authorized file, and the online authorization information bound to the data user's identity for each d, and then sends the file key set... K in d and The file key and its corresponding d are sent to the data user, and the online authorization information is sent to the cloud server; the data user receives the file key and its corresponding authorized file identifier, and updates the local authorization status information ST; the cloud server receives the online authorization information and updates the received data to the online authorization index USet stored on it; During the offline authorization phase, authorized data users authorize the set of files accessible to their subordinate data users, calculate the offline authorization information bound to their own and subordinate user identities, and the offline authorization token bound to their own and subordinate data user identities for each authorized file identifier d. They then send the offline authorization token, file key, and offline authorization information index number to the subordinate data users and send the offline authorization information to the cloud server. The subordinate data users update their local authorization status information ST with the received data; the cloud server updates its stored offline authorization index ASet with the received data. The dynamic secure encrypted retrieval method includes: During the initialization phase, the security parameter λ is input to generate the key SK and the cyclic group parameters. Initialize the search index XSet, where the key is kept by the data owner, the circular group parameter is publicly provided to the participating entities, and the search index is uploaded to the cloud server. During the encrypted data update phase, the data owner calculates the index number and encrypted value of the file identifier for each keyword / file identifier pair (w,d) in the search index for the updated file set DOC, and sends these index numbers and corresponding encrypted values ​​to the cloud server; when the cloud server receives the encrypted data update request sent by the data owner, it updates the received data to the search index XSet stored on it. During the keyword encryption query phase, the data user generates a search token based on the keywords and authorization information they need to search for, and sends it to the cloud server. The cloud server performs a search operation within the set of files authorized for access by the data user without decryption, and returns the search results to the data user. After receiving the returned search results, the data user decrypts them and finally obtains the set of all file identifiers d that meet the search requirements.

2. The encrypted retrieval method supporting hierarchical authorization according to claim 1, characterized in that: In the hierarchical authorization method, during the initialization phase, the security parameter λ∈N is input, and the key SK=(K1,K2,K3) is generated, where K1,K2,K3∈{0,1} λ The key is randomly selected and kept by the data owner; cyclic group parameters are generated. Where p is a cyclic group The prime order of g, and g is a cyclic group. The generator is publicly provided to participating entities, including data users and cloud servers; the online authorization index USet and the offline authorization index ASet are initialized and uploaded to the cloud server.

3. The encrypted retrieval method supporting hierarchical authorization according to claim 1, characterized in that: In the hierarchical authorization method, during the data user registration phase, the data owner distributes its exclusive key to the data user u. in For a randomly selected user key, initialize the authorization status information ST = (UAuth, DocKey, aid), where UAuth is the user's offline authorization token index, DocKey is the user's authorization file key index, and aid is the offline authorization information index number. Then, provide the exclusive key UK and the authorization status information ST to the data user u to complete the registration.

4. The encrypted retrieval method supporting hierarchical authorization according to claim 2, characterized in that: In the hierarchical authorization method, during the online authorization phase, the data owner authorizes a set of files that data user u can access, and calculates a file key set generated from the identifier d of each authorized file. Where K d =F(K1,d), F:{0,1} λ ×{0,1} * →{0,1} Θ(λ) It is a pseudo-random function that outputs a field of order p. The elements of length Θ(λ) in the middle, G:{0,1} λ ×{0,1} * →{0,1} λ It is a pseudo-random function that outputs a string of length λ; it will also output a portion of the file key. The corresponding d is sent to the data user u, and the online authorization information (uid) bound to the data user u for each d is calculated. u,d U u,d ), including the online authorization information index number Index value The online authorization information is sent to the cloud server; the data user receives the file key and its corresponding set of authorized file identifiers. Update the local authorization status information ST; the cloud server will receive the online authorization information data {(uid)} u,d U u,d Update to the online authorization index USet stored on it.

5. The encrypted retrieval method supporting hierarchical authorization according to claim 4, characterized in that: In the aforementioned hierarchical authorization method, during the offline authorization phase, authorized data user u A For its subordinate data users u B The set of files that can be authorized for access is used to calculate the offline authorization information (aid, α) that binds the user's identity to its own and the user's lower-level data, where the offline authorization information index number is... Index value Send the offline authorization information to the cloud server, and send the offline authorization information index number (AID) to the lower-level data user (U). B ; Calculate the file identifier d for each authorized access file with respect to itself and its subordinate data users u. B An offline authorization token bound to an identity, when an authorized user u A An offline authorization token is issued when the data owner authorizes online. Otherwise, from authorized user u A Retrieve the offline authorization token (offtok) corresponding to the authorized file d from the local authorization status information ST, and recalculate the offline authorization token. Send the offline authorization token to the lower-level data user u B ; From authorized user u A Retrieve the set of file keys corresponding to the set of authorized files from the local authorization status information ST. Send the authorization file key set to the lower-level data user u B Lower-level data user u B Update the local authorization status information ST with the received data; The cloud server updates the received data to the offline authorized index ASet stored on it.

6. The encrypted retrieval method supporting hierarchical authorization according to claim 1, characterized in that: The dynamic secure encrypted retrieval method, in its initialization phase, inputs a security parameter λ∈N and generates a key SK=(K1,K2,K3), where K1,K2,K3∈{0,1} λ The key is randomly selected and kept by the data owner; cyclic group parameters are generated. Where p is a cyclic group The prime order of g, and g is a cyclic group. The generator is publicly provided to participating entities, including data users and cloud servers; the search index XSet is initialized and uploaded to the cloud server.

7. The encrypted retrieval method supporting hierarchical authorization according to claim 6, characterized in that: In the aforementioned dynamic secure encrypted retrieval method, during the encrypted data update phase, the data owner calculates a file key group for each file identifier d in the updated file set DOC. Where K d =F(K1,d), F:{0,1} λ ×{0,1} * →{0,1} Θ(λ) It is a pseudo-random function that outputs a field of order p. The elements of length Θ(λ) in the middle, G:{0,1} λ ×{0,1} * →{0,1} λ It is a pseudo-random function that outputs a string of length λ; for each keyword / file identifier pair (w, d), its index number X in the search index is calculated. w,d and the encrypted value Y of the file identifier w,d ,in These index numbers and their corresponding encrypted values ​​are then sent to the cloud server. When the cloud server receives a request to update encrypted data from the data owner, it updates the received data to the search index XSet stored on it.

8. The encrypted retrieval method supporting hierarchical authorization according to claim 7, characterized in that: In the described dynamic secure encrypted retrieval method, during the keyword encryption query phase, data user u calculates a retrieval token set {stk} based on the keyword w to be retrieved and the authorization status information ST. d When data user u is a user authorized online by the data owner, otherwise, Offtok is an offline authorization token retrieved from the local authorization status information ST in u, and the retrieval token is sent to the cloud server; The cloud server performs a search operation within the set of files that the user has authorized access to without decryption, and calculates... and x ASet[aid] Does it match in the search index? If it does, return the corresponding index value y. d The search result is given to data user u; after receiving the returned search result, data user u decrypts it and calculates... Finally, the set Res of all file identifiers d that meet the search requirements is obtained.

9. A encrypted retrieval system supporting hierarchical authorization, characterized in that: include: One or more processors; A storage device for storing one or more programs, which, when executed by one or more processors, cause the one or more processors to implement the encrypted retrieval method supporting hierarchical authorization as described in any one of claims 1 to 8.

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