Education data decentration security verification method based on block chain and encryption search

Abstract

The invention discloses an educational data decentration security verification method based on a block chain and encrypted search, the block chain is used for storing a ciphertext and an encrypted index, a search trap door is generated and a search task is executed through a verification node in the block chain, and data storage and retrieval without a third party are realized. The attribute encryption method based on the ciphertext strategy is utilized, so that a data owner can safely share the file data to different users by encrypting the file data once. The integrity verification of the data search result is carried out by using a star-shaped hidden data structure and a multi-set hash function, and the problem of contradiction between data integrity verification and forward and backward privacy of data is solved.

Description

Technical Field

[0001] The present invention relates to the field of educational data security technology, and in particular to a decentralized security verification method for educational data based on blockchain and encrypted search. Background Art

[0002] The rapid development of Internet information technology has promoted the informatization of education, and educational data has gradually changed from paper storage to electronic storage. Due to the long life cycle of educational data and in order to reduce the pressure of local educational data storage, more and more network users choose to send educational data to the cloud for storage, so as to achieve long-term storage and management updates of educational data. However, if educational data is stored directly in the cloud, sensitive information in the educational data may be stolen and leaked by malicious users. Therefore, the owner of educational data will encrypt the educational data and then store it in the cloud to prevent the leakage of sensitive information, but traditional encryption technology cannot perform efficient search when educational data is encrypted. In response to the drawbacks of traditional encryption technology, searchable encryption technology has been studied, which can ensure that the content of educational data is not leaked, allowing educational data users to search and query encrypted educational data safely and efficiently.

[0003] Based on searchable encryption technology, education data owners can first encrypt their data and corresponding indexes locally, and then upload them to third-party platforms such as cloud servers. When education data users want to query education data containing a certain keyword, they build a search trap for the keyword locally and then upload it to third-party platforms such as cloud servers. Third-party platforms such as cloud servers match the corresponding data index through the search trap and return it to the education data user. The education data user then obtains the encrypted data based on the data index returned by the cloud server. Since the data index and the search trap are matched one by one, the search for encrypted data is realized. Most traditional searchable encryption schemes combine attribute-based access control or inner product encryption with searchable encryption technology to solve the problems of data privacy leakage and low search efficiency in encrypted data storage in third-party platforms such as cloud servers. However, there are still problems such as relying on third-party platforms such as cloud servers to store ciphertext and encrypted indexes, and performing search tasks through them, and the integrity of data search results cannot be verified.

[0004] In order to solve the problems in traditional searchable encryption schemes, some verifiable search encryption schemes based on blockchain have been proposed by scholars. Most of these research schemes use the irreversibility of hash functions to generate data summaries and use smart contracts to verify the integrity of data search results. However, these research schemes not only still rely on third-party platforms such as cloud servers to store ciphertexts and encrypted indexes and perform search tasks through them, but also the data sharing is for a certain user and is not suitable for sharing with multiple parties. In addition, when these research schemes verify data search results, they cannot protect the forward privacy and backward privacy of the data at the same time. Summary of the invention

[0005] The present invention aims to solve the problem that the current searchable encryption scheme for educational data relies on third-party platforms such as cloud servers, data can only be shared one-to-one, and when verifying data search results, it is impossible to simultaneously protect the forward privacy and backward privacy of the data. A decentralized security verification method for educational data based on blockchain and encrypted search is provided.

[0006] To solve the above problems, the present invention is achieved through the following technical solutions:

[0007] The decentralized security verification method for educational data based on blockchain and encrypted search includes the following steps:

[0008] Step 1: The education data owner and the verification node in the blockchain generate their own public and private key pairs, and generate relevant parameters for attribute access control;

[0009] Step 2: The education data owner encrypts the file to be updated locally, and generates the state ciphertext, index ciphertext and proof based on the star hidden data structure, and then uploads the encrypted file, state ciphertext, index ciphertext and proof to the blockchain;

[0010] Step 3: After the education data user completes the transaction with the education data owner, the education data user obtains his / her own attribute private key through the verification node, and then sends the keyword he / she wants to query and its version number to the verification node, and the verification node generates a search trap for the education data user;

[0011] Step 4: The verification node searches the file encryption index according to the search trap and uploads the search results to the smart contract of the blockchain;

[0012] Step 5: The smart contract verifies the integrity of the received search results and outputs a verification pass or a verification fail;

[0013] Step 6. After the smart contract verifies the integrity of the search results, the education data user first obtains the encrypted index from the blockchain and decrypts it to obtain the index of the encrypted file. Then, the encrypted file is obtained from the blockchain through the index of the encrypted file and decrypted to obtain the desired file.

[0014] The specific steps of step 1 above are:

[0015] Step 1.1: The education data owner generates a private key sk O and public key pk O ;

[0016] Step 1.2: The verification node in the blockchain generates a private key sk V and public key pk V , and use the CP-ABE method to generate the access control public key PK and the master key MK, and then use the Shamir method to convert the private key sk V And the master key MK is uploaded and stored on the blockchain.

[0017] In the above step 1.1, the education data owner sends the public key pk O Upload and store directly to the blockchain. In step 1.2 above, the verification node in the blockchain will send the public key pk V The public key PK is directly uploaded and stored on the blockchain.

[0018] The specific steps of step 2 above are:

[0019] Step 2.1: The education data owner uses the access control public key PK and access policy T to update the file set DB containing the keyword w. i File M j Encrypt and get the encrypted file CT j ;

[0020] Step 2.2: Educate the data owner to use his own private key sk O And the public key pk of the verification node V Generate the master private key Key;

[0021] Step 2.3: The owner of the education data uses the master key Key and keyword w i and keyword w i The current version number v l , generating the current state And the keyword w i The current version number v l Upload and store to the blockchain; at the same time, use the keyword w previously stored on the blockchain i The previous version number v l-1 , the same method is used to generate the previous state

[0022] Step 2.4: Educate data owners on the current status Previous state and the document set DB contains the keyword w i File M j The number of files in DB(w i )|Hash to generate the current state ciphertext, where the current state ciphertext includes the current state key ciphertext and the current state value ciphertext

[0023] Step 2.5: The education data owner uses the access control public key PK and access policy T to access each file set DB containing the keyword w. i File M j Position index and update method Encrypt and generate the current encryption index Then get the current encrypted index set

[0024] Step 2.6: The owner of the education data searches for the document set DB containing the keyword w i File M j The file number j, the current encryption index and current status Hash to generate the current index ciphertext, where the current index ciphertext includes the index key ciphertext and index value ciphertext

[0025] Step 2.7: Educate data owners on the current status Current encryption index set and the previous proof value stored on the blockchain Perform multi-set hashing to generate the current proof, where the current proof includes the current proof key and the current proof value

[0026] Step 2.8. The education data owner will encrypt the file CT j , current state key ciphertext and the current state value ciphertext Current index key ciphertext and the current index value ciphertext and the current certification key and the current proof value Upload and store them on the blockchain together.

[0027] In the above step 2.8, the current state key ciphertext and the current state value ciphertext Index key ciphertext and index value ciphertext and the current certification key and the current proof value It is stored in the blockchain as key-value pairs.

[0028] The specific steps of step 3 above are:

[0029] Step 3.1: After the education data user and the education data owner complete the transaction, the education data owner stores the transaction summary information on the blockchain;

[0030] Step 3.2: Verify that the node uses its own private key sk V and the public key pk of the education data owner O Generate the master private key Key′;

[0031] Step 3.3: The education data user sends his attribute set S to the verification node. The verification node uses the master key MK and the attribute set S to generate the attribute private key SK and returns it to the education data user.

[0032] Step 3.4: After receiving his / her attribute private key SK, the education data user will enter the keyword w i and its version number v l Sent to the verification node, the verification node uses the master private key Key′ and the keyword w to be queried i and its version number v l Generating search traps for educational data users

[0033] The specific steps of step 4 above are:

[0034] Step 4.1: Set the current number of iterations t = l, and search for the trapdoor As current status

[0035] Step 4.2: Verify the node using the current state Generate the current state key ciphertext Then get the current state value ciphertext in the form of key-value pairs

[0036] Step 4.3: Verify the node using the current state and the document set DB contains the keyword w i File M j Generate the current index key ciphertext based on the file number j Then get the current index value ciphertext in the form of key-value pairs

[0037] Step 4.4: Verify that the node uses the file set DB containing the keyword w i File M j File number j, current status and the current index value ciphertext Generate the current encryption index Then get the current encrypted index set

[0038] Step 4.5: Use the current state value ciphertext and current status Get the file set DB containing the keyword w i File M j The number of files in DB(w i )| and the previous state

[0039] Step 4.6: Subtract 1 from the current iteration number t and set the previous state As current status Repeat the process from 4.2 to 4.4;

[0040] Step 4.7: Repeat the iterative process of step 4.6 until the current iteration number t = 0. At this time, the current state obtained in each iteration is and the current set of encrypted indexes Aggregate search results And the search results Uploaded to the smart contract on the blockchain.

[0041] The specific steps of step 5 above are:

[0042] Step 5.1: Smart contract sends search results Split to obtain each state and its corresponding encrypted index set;

[0043] Step 5.2: Perform integrity verification on each encrypted index set. If all encrypted index sets pass the verification, the output verification passes. Otherwise, the output verification fails.

[0044] The specific steps of step 6 above are:

[0045] Step 6.1: Education data users obtain current search results from the blockchain And use the access control public key PK and attribute private key SK to access the current search result The current set of encrypted indexes in Each current encryption index Decrypt and get the corresponding position index and update method

[0046] Step 6.2: Educate data users according to the update method and position index Get encrypted file CT from blockchain j , and then decrypt to get the desired file set DB containing keyword w i File M j .

[0047] Compared with the prior art, the present invention has the following characteristics:

[0048] 1. Use blockchain to store ciphertext and encrypted indexes, and let the verification nodes in the blockchain generate search traps and perform search tasks, solving the single point of failure and centralization problems caused by relying on third-party platforms such as cloud servers;

[0049] 2. Using the attribute encryption method based on ciphertext strategy, the education data owner can encrypt the file data only once and then safely share the file data with different users;

[0050] 3. Use star-shaped hidden data structures and multi-set hash functions to ensure that the forward and backward privacy of data can be protected while the integrity of data search results is verified. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 A model architecture diagram of a decentralized security verification method for educational data based on blockchain and encrypted search;

[0052] Figure 2 A flowchart of a decentralized secure verification method for educational data based on blockchain and encrypted search;

[0053] Figure 3 Schematic diagram of file updates for educational data owners;

[0054] Figure 4 Diagram of searching the encrypted index of files for a verification node. DETAILED DESCRIPTION

[0055] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific examples and with reference to the accompanying drawings.

[0056] A decentralized security verification method for educational data based on blockchain and encrypted search. Its model architecture is as follows: Figure 1 As shown, the flow chart is as follows Figure 2 As shown, it includes the following steps:

[0057] S1. System initialization: The education data owner and the verification node in the blockchain generate their own public and private key pairs, and generate relevant parameters for attribute access control. The specific implementation steps are as follows:

[0058] 1.1) The system uses the elliptic curve method to generate the public parameter P.

[0059] Both the education data owner and the verification node in the blockchain use the public parameter P to generate a public-private key pair, and use the elliptic curve cryptography method to generate a public-private key pair to meet user information security requirements.

[0060] 1.2) The owner of the education data randomly selects an integer a as his private key sk O , and then generate your own public key pk O = aP. Then directly use the public key pk O Upload to the blockchain for storage.

[0061] 1.3) The verification node in the blockchain first randomly selects an integer b as the shared private key sk V , and then generate the shared public key pk V = bP. Then directly use the public key pk v Upload to the blockchain for storage.

[0062] 1.4) The verification node in the blockchain uses the CP-ABE (attribute encryption based on ciphertext policy) method to generate the access control public key PK and the master key MK, that is, formula (1). Then the access control public key PK is directly uploaded to the blockchain for storage.

[0063] Setup(λ)→(PK, MK) (1)

[0064] Wherein, Setup(*) represents the initialization method in the CP-ABE method.

[0065] An attribute encryption method based on ciphertext strategy is used to generate relevant parameters for attribute access control. This method allows education data owners to set data access policies, thereby achieving fine-grained access control of the data.

[0066] 1.5) The verification node in the blockchain sends the private key sk V And the master key MK is stored on the blockchain through the Shamir method.

[0067] The existing blockchain-based verifiable search encryption scheme uploads all public keys to the blockchain by default, and stores private keys sk v The master key MK is stored locally, and in order to facilitate the subsequent verification nodes to share them, the present invention not only stores all the public keys (pk O , pkV and PK) are uploaded and stored on the blockchain, and sk V and MK are uploaded and stored on the blockchain.

[0068] S2. The education data owner encrypts the file to be updated locally, and generates the state ciphertext, index ciphertext and proof based on the star hidden data structure, and then uploads the encrypted file, state ciphertext, index ciphertext and proof to the blockchain. Figure 3 The specific implementation steps are as follows:

[0069] 2.1) The education data owner uses the access control public key PK and access policy T to update the file set DB containing the keyword w i File M j Encrypt and get the encrypted file CT j , that is, formula (2).

[0070] E(PK,M j , T)→CT j (2)

[0071] Among them, E(*) represents the encryption method in the CP-ABE method, j represents the file set DB containing the keyword w i File M j The file number, j = 1, 2, ..., | DB (w i )|,|DB(w i )|Indicates that the file set DB contains the keyword w i File M j The number of files. File M j Contains the keyword w i , keyword w i Can be selected as data retrieval condition.

[0072] 2.2) Educate data owners to use their own private key sk O and the public key pk of the verification node V , generate the master private key Key, that is, formula (3).

[0073] sk O pk V →Key (3)

[0074] 2.3) Educate data owners to use keyword w i , keyword w i The current version number v l and the master key Key to generate the current state That is, formula (4), and the version number v lUpload and store it on the blockchain. At the same time, the owner of the education data uses the previous version number v stored on the blockchain l-1 , the same method is used to generate the previous state That is formula (5).

[0075]

[0076] Wherein, F1(*) represents a pseudo-random function.

[0077] 2.4) Educate data owners on the current status and the previous state and the file set DB contains the keyword w i File M j The number of files in DB(w i )|Hash to generate the current state ciphertext, where the current state ciphertext includes the state key ciphertext and state value ciphertext That is, formulas (6) and (7).

[0078]

[0079]

[0080] Among them, h1(*) and h2(*) represent different collision-resistant hash functions. represents an XOR operation, and || represents a string concatenation operation.

[0081] 2.5) Educate the data owner to use the access control public key PK and access policy T to access each file set DB containing the keyword w i File M j Position index and update method Encryption is performed to generate information about each file set DB containing the keyword w i File M j Current encryption index of That is, formula (8), and then all the documents containing keyword w in the document set DB are obtained i File M j The current set of encrypted indexes That is formula (9).

[0082]

[0083] Wherein, E(*) represents the encryption method in the CP-ABE method, and | | represents the string concatenation operation.

[0084] 2.6) The owner of the education data has a database containing the keyword wi File M j The file number j, the current encryption index and current status Hash to generate the current index ciphertext, where the current index ciphertext includes the index key ciphertext and index value ciphertext That is, formulas (10) and (11).

[0085]

[0086] Among them, h3(*) and h4(*) represent different collision-resistant hash functions. represents XOR operation, and || represents string concatenation operation.

[0087] 2.7) Educate data owners on the current status Current encryption index set and the previous proof value stored on the blockchain Perform multi-set hashing to generate the current proof, where the current proof includes the current proof key and the current proof value That is, formulas (12) and (13).

[0088]

[0089] Among them, h0(*) represents a collision-resistant hash function, and H(*) represents a multi-set hash function.

[0090] Previous proof value Generated in the last update operation (generation method and current proof value The initial proof value is set to a constant U and stored on the blockchain.

[0091] 2.8) The owner of the educational data will encrypt the file CT j , current state ciphertext and Current index ciphertext and And the current proof and Upload and store them on the blockchain together, including the current state key ciphertext and the current state value ciphertext Index key ciphertext and index value ciphertext and the current certification key and the current proof value It is stored in the blockchain as key-value pairs.

[0092] S3. After the education data user completes the transaction with the education data owner, the education data user obtains his own attribute private key through the verification node, and then sends the keyword he wants to query and its version number to the verification node, and the verification node generates a search trap for the education data user. The specific implementation steps are as follows:

[0093] 3.1) After the education data user conducts a transaction with the education data owner, the education data owner stores the transaction summary information on the blockchain.

[0094] 3.2) The verification node uses its own private key sk V and the public key pk of the education data owner O Generate the master private key Key′, that is, formula (14).

[0095] sk V pk O →Key′ (14)

[0096] 3.3) The education data user sends his attribute set S to the verification node. The verification node uses the master key MK and the attribute set S to generate the attribute private key SK and returns it to the education data user, that is, formula (15).

[0097] KeyGen(MK,S)→SK (15)

[0098] Wherein, KeyGen(*) represents the key generation method in the CP-ABE method.

[0099] 3.4) After receiving his / her attribute private key SK, the education data user will enter the keyword w i and its version number v l Sent to the verification node, the verification node uses the master private key Key′ and the keyword w i and version number v l Generating search traps for educational data users That is formula (16).

[0100]

[0101] Wherein, F1(*) represents a pseudo-random function.

[0102] S4. The verification node searches the file encryption index according to the search trap and uploads the search results to the smart contract of the blockchain, such as Figure 4 The specific implementation steps are as follows:

[0103] 4.1) Let the current iteration number t = l, and search for the trapdoor As current status Right now:

[0104]

[0105] 4.2) Verify the node uses the current state Generate the current state key ciphertext That is, formula (17), and then the current state value ciphertext is obtained in the form of key-value pairs

[0106]

[0107] Wherein, h1(*) represents a collision-resistant hash function.

[0108] 4.3) Verify the node uses the current state and the document set DB contains the keyword w i File M j Generate the current index key ciphertext based on the file number j That is, formula (18), and then the current index value ciphertext is obtained in the form of a key-value pair

[0109]

[0110] Wherein, h3(*) represents a collision-resistant hash function.

[0111] 4.4) The verification node uses each file set DB containing the keyword w i File M j File number j, current status and the current index value ciphertext Generate the current encryption index That is, formula (19), and then all the files in the document set DB containing the keyword w are obtained i File M j The current set of encrypted indexes That is formula (20).

[0112]

[0113] Among them, h4(*) represents the collision-resistant hash function. represents XOR operation, and || represents string concatenation operation.

[0114] 4.5) Encrypt the current state value and current status Perform XOR to obtain the file set DB containing the keyword w i File M j The number of files in DB(w i )| and the previous state That is formula (21).

[0115]

[0116] Among them, h2(*) represents the collision-resistant hash function. represents XOR operation, and || represents string concatenation operation.

[0117] 4.6) Subtract 1 from the current iteration number t and set the previous state As current status Repeat the process from 4.2 to 4.4.

[0118] 4.7) Repeat the iterative process of step 4.6 until the current iteration number t = 0, at which time the current state obtained in each iteration is and the current set of encrypted indexes Aggregate search results That is, formula (22), and the search results Uploaded to the smart contract on the blockchain.

[0119]

[0120] Among them, ∪ represents the union operation.

[0121] S5. The smart contract verifies the integrity of the received search results. The specific implementation steps are as follows:

[0122] The integrity of data search results refers to ensuring the consistency and accuracy of data search results during the transmission and storage of data search results, that is, ensuring that data search results will not be damaged or tampered with. The forward privacy of data means that when the content of past data queries is leaked, the current or future data query content will not be leaked. The backward privacy of data means that when the content of current or future data queries is leaked, the past query content will not be leaked. Data integrity verification requires that the relevant information of historical data query content be saved, but the forward and backward privacy of data require maximizing the disconnection between data query content, which creates a contradiction that data integrity verification and forward and backward privacy of data are difficult to guarantee at the same time.

[0123] 5.1) The smart contract first sends the search results Split it and get each state and its corresponding encrypted index set, that is, formula (23).

[0124]

[0125] Among them, ⊥ represents the empty set.

[0126] 5.2) Then the smart contract performs a Perform integrity verification, i.e., formula (24).

[0127]

[0128] Where H(*) represents a multi-set hash function. represents the current proof value, Represents the previous proof value.

[0129] The search result integrity verification uses a multi-set hash function method, which can verify data integrity safely and efficiently.

[0130] 5.3) If each If the above verifications are met, the output verification passes, otherwise the output verification fails.

[0131] S6. After the smart contract verifies the integrity of the search results, the education data user first decrypts the encrypted file to obtain the location index, and then decrypts the desired file. The specific implementation steps are as follows:

[0132] 6.1) Educational data users obtain current search results from the blockchain And use the access control public key PK and attribute private key SK to access the current search result The current set of encrypted indexes in Each current encryption index Decrypt and get the corresponding position index and update method That is formula (25).

[0133]

[0134] Wherein, D(*) represents the decryption method in the CP-ABE method.

[0135] 6.2) Education data users according to the update method and position index Get encrypted file CT from blockchain j , and then decrypt to get the desired file set DB containing keyword w i File M j , that is, formula (26).

[0136] D(PK,CT j , SK)→M j (26)

[0137] Wherein, D(*) represents the decryption method in the CP-ABE method.

[0138] In order to improve efficiency, in the actual implementation process, the update method Can be used to guide encrypted file CT jIf the update method is to add, the education data user needs to index the location Get encrypted file CT from blockchain j If the update method is deletion, the education data user does not need to index by location. Get encrypted file CT from blockchain j .

[0139] The present invention uses blockchain to store ciphertext and encrypted indexes, and generates search traps and executes search tasks through verification nodes in the blockchain, thereby realizing data storage and retrieval without a third party. By using an attribute encryption method based on a ciphertext strategy, data owners can encrypt file data only once and then safely share the file data with different users. By using a star-shaped hidden data structure and a multi-set hash function to verify the integrity of data search results, the problem of the contradiction between data integrity verification and forward and backward privacy of data is solved.

[0140] It should be noted that, although the embodiments of the present invention described above are illustrative, they are not intended to limit the present invention, and therefore the present invention is not limited to the above specific embodiments. Without departing from the principles of the present invention, any other embodiments obtained by those skilled in the art under the guidance of the present invention are deemed to be within the protection of the present invention.

Claims

1. A decentralized security verification method for educational data based on blockchain and encrypted search, characterized by: The steps include: Step 1: The education data owner and the verification node in the blockchain generate their own public and private key pairs, and generate relevant parameters for attribute access control; Step 2: The education data owner encrypts the file to be updated locally, and generates the state ciphertext, index ciphertext and proof based on the star hidden data structure, and then uploads the encrypted file, state ciphertext, index ciphertext and proof to the blockchain; Step 3: After the education data user completes the transaction with the education data owner, the education data user obtains his / her own attribute private key through the verification node, and then sends the keyword he / she wants to query and its version number to the verification node, and the verification node generates a search trap for the education data user; Step 4: The verification node searches the file encryption index according to the search trap and uploads the search results to the smart contract of the blockchain; Step 5: The smart contract verifies the integrity of the received search results and outputs a verification pass or a verification fail; Step 6. After the smart contract verifies the integrity of the search results, the education data user first obtains the encrypted index from the blockchain and decrypts it to obtain the index of the encrypted file. Then, the encrypted file is obtained from the blockchain through the index of the encrypted file and decrypted to obtain the desired file.

2. According to the decentralized security verification method for educational data based on blockchain and encrypted search according to claim 1, the specific steps of step 1 are: Step 1.1: The education data owner generates a private key sk O and public key pk O ; Step 1.2: The verification node in the blockchain generates a private key sk V and public key pk V , and use the CP-ABE method to generate the access control public key PK and the master key MK, and then use the Shamir method to convert the private key sk V And the master key MK is uploaded and stored on the blockchain.

3. According to the decentralized security verification method for educational data based on blockchain and encrypted search according to claim 2, in step 1.1, the owner of the educational data sends the public key pk O Upload and store directly to the blockchain. In step 1.2, the verification node in the blockchain will send the public key pk V The public key PK is directly uploaded and stored on the blockchain.

4. The decentralized security verification method for educational data based on blockchain and encrypted search according to claim 1 is characterized in that: The specific steps of step 2 are: Step 2.1: The education data owner uses the access control public key PK and access policy T to update the file set DB containing the keyword w. i File M j Encrypt and get the encrypted file CT j ; Step 2.2: Educate the data owner to use his own private key sk O And the public key pk of the verification node V Generate the master private key Key; Step 2.3: The owner of the education data uses the master key Key and keyword w i and keyword w i The current version number v l , generating the current state And the keyword w i The current version number v l Upload and store to the blockchain; at the same time, use the keyword w previously stored on the blockchain i The previous version number v l-1 , the same method is used to generate the previous state Step 2.4: Educate data owners on the current status Previous state and the document set DB contains the keyword w i File M j The number of files in DB(w i )|Hash to generate the current state ciphertext, where the current state ciphertext includes the current state key ciphertext and the current state value ciphertext Step 2.5: The education data owner uses the access control public key PK and access policy T to access each file set DB containing the keyword w. i File M j Position index and update method Encrypt and generate the current encryption index Then get the current encrypted index set Step 2.6: The owner of the education data searches for the document set DB containing the keyword w i File M j The file number j, the current encryption index and current status Hash to generate the current index ciphertext, where the current index ciphertext includes the index key ciphertext and index value ciphertext Step 2.7: Educate data owners on the current status Current encryption index set and the previous proof value stored on the blockchain Perform multi-set hashing to generate the current proof, where the current proof includes the current proof key and the current proof value Step 2.

8. The education data owner will encrypt the file CT j , current state key ciphertext and the current state value ciphertext Current index key ciphertext and the current index value ciphertext and the current certification key and the current proof value Upload and store them on the blockchain together.

5. The decentralized security verification method for educational data based on blockchain and encrypted search according to claim 4 is characterized in that: In step 2.8, the current state key ciphertext and the current state value ciphertext Index key ciphertext and index value ciphertext and the current certification key and the current proof value It is stored in the blockchain as key-value pairs.

6. The decentralized security verification method for educational data based on blockchain and encrypted search according to claim 1 is characterized in that: The specific steps of step 3 are: Step 3.1: After the education data user and the education data owner complete the transaction, the education data owner stores the transaction summary information on the blockchain; Step 3.2: Verify that the node uses its own private key sk V and the public key pk of the education data owner O Generate the master private key Key′; Step 3.3: The education data user sends his attribute set S to the verification node. The verification node uses the master key MK and the attribute set S to generate the attribute private key SK and returns it to the education data user. Step 3.4: After receiving his / her attribute private key SK, the education data user will enter the keyword w i and its version number v l Sent to the verification node, the verification node uses the master private key Key′ and the keyword w to be queried i and its version number v l Generating search traps for educational data users 7. The decentralized security verification method for educational data based on blockchain and encrypted search according to claim 1 is characterized in that: The specific steps of step 4 are: Step 4.1: Set the current number of iterations t = l, and search for the trapdoor As current status Step 4.2: Verify the node using the current state Generate the current state key ciphertext Then get the current state value ciphertext in the form of key-value pairs Step 4.3: Verify the node using the current state and the document set DB contains the keyword w i File M j Generate the current index key ciphertext based on the file number j Then get the current index value ciphertext in the form of key-value pairs Step 4.4: Verify that the node uses the file set DB containing the keyword w i File M j File number j, current status and the current index value ciphertext Generate the current encryption index Then get the current encrypted index set Step 4.5: Use the current state value ciphertext and current status Get the file set DB containing the keyword w i File M j The number of files in DB(w i )| and the previous state Step 4.6: Subtract 1 from the current iteration number t and set the previous state As current status Repeat the process from 4.2 to 4.4; Step 4.7, repeat the iterative process of step 4.6 until the current iteration number t = 0, then stop, and the current state obtained in each iteration and the current set of encrypted indexes Aggregate search results And the search results Uploaded to the smart contract on the blockchain.

8. The decentralized security verification method for educational data based on blockchain and encrypted search according to claim 1 is characterized in that: The specific steps of step 5 are: Step 5.1: Smart contract sends search results Split to obtain each state and its corresponding encrypted index set; Step 5.2: Perform integrity verification on each encrypted index set. If all encrypted index sets pass the verification, the output verification passes. Otherwise, the output verification fails.

9. The decentralized security verification method for educational data based on blockchain and encrypted search according to claim 1 is characterized in that: The specific steps of step 6 are: Step 6.1: Education data users obtain current search results from the blockchain And use the access control public key PK and attribute private key SK to access the current search result The current set of encrypted indexes in Each current encryption index Decrypt and get the corresponding position index and update method Step 6.2: Educate data users according to the update method and position index Get encrypted file CT from blockchain j , and then decrypt to get the desired file set DB containing keyword w i File M j .

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