Safe and efficient searchable attribute encryption sharing method based on block chain

Abstract

The invention discloses a safe and efficient searchable attribute encryption sharing method based on a block chain, and the method comprises the steps: initializing system parameters through employing a quick-pairing attribute-based encryption method, and generating an attribute key for an educational institution; generating a cooperative public key based on multi-party cooperation of the block chain; the educational archive owner realizes searchable encrypted shared data based on the collaborative public key; the educational archive user retrieves data according to the interested keyword chain; and the education archive user efficiently decrypts to obtain plaintext data. According to the searchable encryption method based on the distributed public key, key word guessing attacks are successfully defended and data retrieval security is ensured through the collaborative key generated by multiple parties of the nodes on the chain in a collaborative mode and the key word set is encrypted based on the collaborative key, so that even if a private key of a single node is leaked, illegal users cannot obtain key words, and the security of data retrieval is ensured. And the leakage of search preference and privacy is avoided, so that the risk of leakage of a single key is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of file sharing, and in particular to a secure, efficient, searchable attribute encryption sharing method based on blockchain. Background Art

[0002] With the continuous advancement of educational informatization, educational archives need to be shared across institutions to realize the circulation and search of archival data. However, due to the high sensitivity and authority of educational archives, the issues of privacy and authenticity need to be resolved simultaneously during the circulation of data.

[0003] In order to improve access efficiency while protecting privacy, researchers proposed an attribute-based searchable encryption scheme for multi-user shared retrieval. The core of this technology lies in the combination of searchable encryption technology and attribute-based encryption. Searchable encryption allows keyword search in the ciphertext domain without leaking plaintext, and attribute-based encryption well meets the user's one-to-many ciphertext search needs. However, this method relies on the centralized storage management mode of cloud servers and has the risk of single point failure. Once the server fails, it is easy to cause data to be maliciously tampered with or leaked, and users cannot obtain the real education process, which lacks security and flexibility and cannot guarantee the authenticity of the data.

[0004] In order to solve the problem of data authenticity, blockchain has attracted widespread attention from researchers from all walks of life due to its unique advantages such as transparency, immutability and traceability. Existing research proposes to use decentralized blockchain technology as a technical support for the secure sharing of educational archives, breaking through the single point failure problem of traditional educational service systems and realizing distributed trusted sharing of educational archives across institutions. It is worth noting that when encrypted data is placed on the blockchain, due to the transparent and immutable characteristics of the blockchain, users' retrieval and access behaviors still face huge security and privacy threats.

[0005] In order to solve the privacy and authenticity issues of data at the same time, existing research has designed a joint solution based on attribute searchable encryption and blockchain technology. Educational institutions only need to upload the index established for shared files to the chain, and data users perform search operations through smart contracts deployed on the chain. Every step of the execution is open and transparent. At the same time, data access records are recorded on the chain in the form of transactions and verified by peer nodes on the chain, ensuring the transparency and traceability of data access. The above method not only allows users to use arbitrary keywords to obtain encrypted data containing keywords of interest, but also allows data owners to implement effective data access control on outsourced ciphertext. However, the existing blockchain-based searchable attribute encryption schemes for educational archives have the following challenges:

[0006] At present, most of the blockchain research on educational archive sharing focuses on the two processes of data retrieval efficiency and data access control, ignoring the consideration of retrieval security and decryption computational overhead. Moreover, the research on the protection of student educational archives in the special field of education is still in its infancy. In addition, student educational archives record the complete educational process, including academic degrees, educational experience, award certificates and transcripts, and these data have the characteristics of high sensitivity and authority. Therefore, a data sharing solution with high search security and high decryption efficiency is needed. Summary of the invention

[0007] The present invention aims to solve the problem that the existing blockchain-based searchable attribute encryption method has information leakage and low user access efficiency when facing educational archives, and provides a safe and efficient blockchain-based searchable attribute encryption sharing method.

[0008] To solve the above problems, the present invention is achieved through the following technical solutions:

[0009] The secure, efficient and searchable attribute encryption sharing method based on blockchain includes the following steps:

[0010] Step 1: The authentication authority initializes the system public parameters using the attribute-based encryption method of fast pairing;

[0011] Step 2: The certification authority initializes its attribute private key SK based on the attribute set of the educational institution i , and the attribute private key SK i Send it back to the corresponding educational institution;

[0012] Step 3: The certification authority generates a public key pk for the educational institution i and private key sk i , and the public key pk i and private key sk i Send it back to the corresponding educational institution;

[0013] Step 4: The certification authority aggregates the public keys pk of all educational institutions i Get collaborative public key And the collaborative public key Send back to various educational institutions;

[0014] Step 5: The educational archive owner in the educational institution uses the symmetric key S specified by him / her key , use the symmetric encryption algorithm to encrypt the education file Doc to be shared, and get the ciphertext education file CT F ;

[0015] Step 6: The educational archive owner in the educational institution uses the attribute-based encryption method based on the fast pairing to encrypt the symmetric key S based on the access policy P specified by him. key Encrypt and obtain the encrypted symmetric key CT Skey ;

[0016] Step 7: The educational archive owner in the educational institution uses the collaborative public key Use the searchable encryption algorithm to encrypt the keyword set w of the educational archives to be shared, and get the ciphertext keyword set CT I ;

[0017] Step 8: The educational archive owner in the educational institution sends the identifier DocID of the educational archive to be shared and its corresponding ciphertext keyword set CT I Perform aggregation to obtain the encrypted index CT Index ;

[0018] Step 9: The educational file owner in the educational institution sends the encrypted educational file CT F Store it in the off-chain distributed storage server and get the storage address Address CTF , and the encrypted index CT Index , Symmetric key CT Skey and storage address Address CTF Uploaded to the blockchain as a transaction;

[0019] Step 10: Educational archive users in educational institutions use the collaborative public key Use the searchable encryption algorithm to encrypt the keyword set w′ of the educational archives of interest, and obtain the retrieval keyword set CT w′ ;

[0020] Step 11: Educational archive users in educational institutions use the attribute private key SK i and search keyword set CT w′ , use the trapdoor generation algorithm to obtain the search trapdoor Td W′ ;

[0021] Step 12: Educational archive users in educational institutions submit search traps Td to the blockchain W′ After receiving the search trap, the on-chain search smart contract executes the search operation and sends the identifier DocID′ and storage address DAddress of the education archive that meets the access policy. CTF 'Return to the user of the educational archive;

[0022] Step 13: The educational archive user in the educational institution obtains the returned educational archive identifier DocID′ and storage address DAddress that meets the access policy. CTF′ Retrieve the corresponding ciphertext education archive CT from the off-chain distributed storage server F′ ;

[0023] Step 14: Educational archive users in educational institutions use the attribute private key SK i , recalculate the symmetric key S using the fast pairing attribute-based encryption method key′ ;

[0024] Step 15: The educational archive user in the educational institution uses the recalculated symmetric key S key′ The ciphertext education archives CT F′ Decrypt it and get the final education file Doc′.

[0025] In the above scheme, the fast pairing attribute-based encryption method is implemented based on Type-Ⅲ asymmetric prime-order bilinear pairing group.

[0026] In the above scheme, in step 7, the ciphertext keyword set CT I for:

[0027]

[0028] Among them, w is the keyword set of the educational archives to be shared, is the collaborative public key, N is the slave collaborative public key The prime number extracted from the collaborative public key Generators extracted from .

[0029] In the above solution, in step 8, the encrypted index CT Index It is stored in an inverted index structure based on B+-Tree and then uploaded to the blockchain.

[0030] In the above scheme, in step 10, the keyword set CT is retrieved w′ for:

[0031]

[0032] Among them, w′ is the keyword set of the educational archives of interest, is the collaborative public key, N is the slave collaborative public key The prime number extracted from the collaborative public key Generators extracted from .

[0033] Compared with the prior art, the present invention has the following characteristics:

[0034] 1. The distributed public key searchable encryption method designed by the present invention generates a collaborative key through the collaboration of multiple nodes on the chain, and encrypts the keyword set based on the collaborative key, successfully resisting keyword guessing attacks and ensuring data retrieval security. In this way, even if the private key of a single node is leaked, illegal users cannot obtain keywords, avoiding search preference and privacy leakage, thereby solving the risk of single key leakage;

[0035] 2. The present invention uses a fast pairing based attribute encryption algorithm, and the educational archive ciphertext decryption process only requires a smaller and faster group Two or three pairing operations are performed in the process, which not only ensures that only valid users who meet the attribute access control policy can access the target data, but also reduces the number of decryption pairing times, improves the decryption efficiency of archive ciphertext, and solves the problem of heavy decryption computational burden on users.

[0036] 3. Use the efficient storage structure of B+-Tree and the convenience of linked list updates to build a dynamic keyword index to improve the flexibility and scalability of the solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a diagram of the architecture of a secure, efficient, searchable attribute encryption sharing model based on blockchain.

[0038] Figure 2 Flowchart of the secure and efficient searchable attribute encryption sharing method based on blockchain.

[0039] Figure 3 It is a time sequence diagram of data sharing among education archive owners based on distributed public key searchable encryption.

[0040] Figure 4 It is a time sequence diagram of educational archive users retrieving data based on the keywords of interest. DETAILED DESCRIPTION

[0041] 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.

[0042] The existing blockchain-based searchable attribute encryption system cannot alleviate the privacy threat caused by the leakage of a single key, and is vulnerable to keyword guessing attacks, resulting in the leakage of sensitive information such as the search preferences of education archive users and students' personal privacy. At the same time, traditional attribute-based encryption brings a heavy decryption calculation burden to education archive users, resulting in low user access efficiency. This paper proposes a secure and efficient searchable attribute encryption sharing method based on blockchain. Its model architecture is as follows: Figure 1 As shown, the flow chart is as follows Figure 2 As shown, the specific steps are as follows:

[0043] S1: Initialize system parameters using the attribute-based encryption method of fast pairing and generate attribute keys for educational institutions.

[0044] 1.1) System initialization: The authentication authority adopts Type-III asymmetric prime-order bilinear pairing group to implement fast pairing based on attribute encryption method. Initialize system common parameters.

[0045] Type-Ⅲ asymmetric prime-order bilinear group is a bilinear pairing group based on attribute encryption method. Efficient hashing can quickly establish a matching relationship between educational archive attributes and educational institution attributes.

[0046] 1.2) Generate attribute private key: The certification authority initializes its attribute private key SK based on the attribute set of the educational institution i , and the attribute private key SK i Send it back to the corresponding educational institution.

[0047] S2: Multiple parties collaborate to generate collaborative public keys based on blockchain.

[0048] 2.1) Generate public and private keys: The certification authority generates a public key pk for the educational institution i and private key sk i , and the public key pk i and private key sk i Send it back to the corresponding educational institution.

[0049] The public key pk of the i-th educational institution i for:

[0050] pk i =(N,g,θ i )

[0051] The private key sk of the i-th educational institution i for:

[0052] sk i =μ i

[0053] Wherein, N=p1q1, p1 and q1 are both prime numbers; g is the generator of the cyclic group; mod means modular operation; μ i is a random number, and μ i ∈[1,N / 4]; i∈[1,V], V is the number of educational institutions.

[0054] 2.2) Generate collaborative public key: The certification authority aggregates the public keys pk of all educational institutionsi Get collaborative public key And the collaborative public key Send back to various educational institutions.

[0055] Collaborative public key for:

[0056]

[0057] in,

[0058] S3: Educational archive owners can realize searchable encrypted shared data based on collaborative public keys; Figure 3 shown.

[0059] Aiming at the security problem of the retrieval process and resisting keyword guessing attacks, the present invention designs a distributed public key searchable attribute encryption scheme. In the sharing stage, the keywords in the education archives are encrypted by the collaborative public key, and the fine-grained access characteristics of the attribute-based encryption with fast pairing are used to achieve fine-grained access to the education archives.

[0060] 3.1) Encryption of plain text education archives: The owner of the education archives in the educational institution uses the symmetric key S specified by him / her. key , use the symmetric encryption algorithm to encrypt the education file Doc to be shared, and get the ciphertext education file CT F .

[0061] Educational archives can represent the true historical records of a student, and they are indispensable in the process of a person's in-depth learning and career development. In order to achieve cross-institutional sharing of educational archives, the owner of the educational archives generally needs to provide their complete educational records. At this time, in order to protect the security of educational archives and prevent data from being maliciously stolen and abused without authorization, the owner of the educational archives needs to encrypt the plaintext data when uploading their educational archives for data sharing.

[0062] Encrypted education files (ciphertext education files) CT F for:

[0063] CT F =Enc AES (Doc,S key )

[0064] Among them, Enc AES Represents the symmetric encryption algorithm, S key is a symmetric key, and Doc is the education file before encryption (plaintext education file).

[0065] 3.2) Symmetric key encryption: The educational archive owner in the educational institution uses the fast pairing attribute-based encryption method to encrypt the symmetric key S based on the access policy P formulated by the educational institution. key Encrypt and obtain the encrypted symmetric key CT Skey .

[0066] Encrypted symmetric key CT Skey for:

[0067] CT Skey =Enctypt_Skey(S key ,P)

[0068] Among them, Enctypt_Skey represents the attribute-based encryption method of fast pairing, S key is a symmetric key, P is the access policy specified by the owner of the education archive, which consists of a matrix E and a mapping function δ. The mapping function δ maps each row of the matrix E to an attribute, P = (E, δ).

[0069] 3.3) Keyword set encryption: Educational archive owners in educational institutions use a collaborative public key Use the searchable encryption algorithm to encrypt the keyword set w of the educational archives to be shared, and get the ciphertext keyword set CT I .

[0070] Ciphertext keyword set CT I for:

[0071]

[0072] in, I ∑,2 = g mod N 2 , N,g is obtained from the educational archive users The prime numbers and generators extracted from .

[0073] 3.4) Constructing a ciphertext index: The educational archive owner in the educational institution sends the identifier DocID of the educational archive to be shared and its corresponding ciphertext keyword set CT I Perform aggregation to obtain the encrypted index CT Index , and the encrypted index CT Index Stored in an inverted index structure based on B+-Tree.

[0074] Encrypted Index CT Index ;

[0075] CT Index =Index_Gen(CT I ,DocID)

[0076] When the owner of an educational archive wants to redefine new keywords for a certain educational archive, he needs to use the collaborative public key to encrypt the new keywords and insert the new ciphertext keyword set into the inverted index structure to complete the index update operation to solve the problem of mismatch between the first extracted keywords and the documents.

[0077] 3.5) Transaction upload: The education file owner in the educational institution uploads the encrypted education file CT F Store it in the off-chain distributed storage server and get the storage address Address CTF , and the encrypted index CT Index , Symmetric key CT Skey and storage address Address CTF Uploaded to the blockchain as a transaction.

[0078] A transaction can be represented as:

[0079] Tx upload ={CT Index ,CT Skey ,Address CTF}

[0080] Transaction transactions are uploaded to the blockchain's data pool, and blockchain nodes record transactions in blocks through a consensus mechanism, realizing distributed shared data on the chain.

[0081] S4: Educational archive users search for data on-chain based on keywords of interest; e.g. Figure 4 shown.

[0082] 4.1) Generate a search keyword set: Educational archive users in educational institutions use the collaborative public key Use the searchable encryption algorithm to encrypt the keyword set w′ of the educational archives of interest, and obtain the retrieval keyword set CT w′ .

[0083] Search keyword set CT w′ for:

[0084]

[0085] in, I′ ∑,2 = g mod N 2 , N,g is obtained from the educational archive users The prime numbers and generators extracted from .

[0086] 4.2) Generate search trapdoor: Educational archive users in educational institutions use the attribute private key SK i and search keyword set CT w′, use the trapdoor generation algorithm to obtain the search trapdoor Td W′ .

[0087] Search Trapdoor Td W′ for:

[0088] Td W′ =Trapdoor_Gen(SK i ,CT w′ )

[0089] 4.3) Ciphertext retrieval: Educational archive users in educational institutions submit search traps Td to the blockchain W′ After receiving the search trap, the on-chain search smart contract executes the search operation and sends the retrieval result, which is the identifier DocID′ and storage address DAddress of the educational archive that meets the access policy. CTF ’ is returned to the user of the educational archive.

[0090] Educational archive users submit retrieval requests to the blockchain (search trap Td Wv ) to obtain the corresponding educational archives. After receiving the retrieval request, the on-chain search smart contract will automatically trigger the search smart contract to perform the search operation. By deploying the search smart contract on the chain, a safe and fair sharing method is provided for both parties in the case of mutual distrust, thus solving the problem of trusted sharing in an untrusted environment. During the search operation process:

[0091] First, the search function of the search smart contract effectively matches the search trap submitted by the education archive user with the encrypted index published on the ledger to obtain the matching results (the identifiers and storage addresses of all education archives that match the keyword set w′).

[0092] Next, the access request function of the search smart contract verifies whether the attribute private key of the education archive user satisfies the access policy of these education archives, and sends the search result (the identifier DocID′ and storage address DAddress of the education archive that satisfies the access policy) to the smart contract. CTF ′) is returned to the user of the educational archive.

[0093] S5: Educational archive users can efficiently decrypt and obtain plaintext data.

[0094] 5.1) Obtaining ciphertext education archives: Education archive users in educational institutions obtain the returned education archive identifier DocID′ and storage address DAddress that meets the access policy. CTF ′ Retrieve the corresponding ciphertext education archive CT from the off-chain distributed storage server Fv .

[0095] 5.2) Calculate the symmetric key: Educational archive users in educational institutions calculate the symmetric key based on the attribute private key SK i , recalculate the symmetric key S using the fast pairing attribute-based encryption method key′ .

[0096] Due to the property private key SK of the present invention i Mainly composed of smaller and faster asymmetric prime-order bilinear groups The elements in The decryption calculation is mainly based on 1 or 2 elements in This is done in the decryption process, thereby optimizing the pairing operation during the decryption process and reducing the decryption burden on the education archive owner.

[0097] 5.3) Decryption: The educational archive user in the educational institution uses the recalculated symmetric key S key′ The ciphertext education archives CT F′ Decrypt it and get the final education file Doc′.

[0098] Doc′=Dec AES (S key′ ,CT F′ )

[0099] 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 secure, efficient and searchable attribute encryption sharing method based on blockchain, characterized by: The steps include: Step 1: The authentication authority initializes the system public parameters using the attribute-based encryption method of fast pairing; Step 2: The certification authority initializes its attribute private key SK based on the attribute set of the educational institution i , and the attribute private key SK i Send it back to the corresponding educational institution; Step 3: The certification authority generates a public key pk for the educational institution i and private key sk i , and the public key pk i and private key sk i Send it back to the corresponding educational institution; Step 4: The certification authority aggregates the public keys pk of all educational institutions i Get collaborative public key And the collaborative public key Send back to various educational institutions; Step 5: The educational archive owner in the educational institution uses the symmetric key S specified by him / her key , use the symmetric encryption algorithm to encrypt the education file Doc to be shared, and get the ciphertext education file CT F ; Step 6: The educational archive owner in the educational institution uses the attribute-based encryption method based on the fast pairing to encrypt the symmetric key S based on the access policy P specified by him. key Encrypt and obtain the encrypted symmetric key CT Skey ; Step 7: The educational archive owner in the educational institution uses the collaborative public key Use the searchable encryption algorithm to encrypt the keyword set w of the educational archives to be shared, and get the ciphertext keyword set CT I ; Step 8: The educational archive owner in the educational institution sends the identifier DocID of the educational archive to be shared and its corresponding ciphertext keyword set CT I Aggregate and get the encrypted index CT Index ; Step 9: The educational file owner in the educational institution sends the encrypted educational file CT F Store it in the off-chain distributed storage server and get the storage address Address CTF , and the encrypted index CT Index , Symmetric key CT Skey and storage address Address CTF Uploaded to the blockchain as a transaction; Step 10: Educational archive users in educational institutions use the collaborative public key Use the searchable encryption algorithm to encrypt the keyword set w′ of the educational archives of interest, and obtain the retrieval keyword set CT w′ ; Step 11: Educational archive users in educational institutions use the attribute private key SK i and search keyword set CT w′ , use the trapdoor generation algorithm to obtain the search trapdoor Td W′ ; Step 12: Educational archive users in educational institutions submit search traps Td to the blockchain W′ After receiving the search trap, the on-chain search smart contract executes the search operation and sends the identifier DocID′ and storage address DAddress of the education archive that meets the access policy. CTF 'Return to the user of the educational archive; Step 13: The educational archive user in the educational institution obtains the returned educational archive identifier DocID′ and storage address DAddress that meets the access policy. CTF 'The corresponding ciphertext education archive CTF is retrieved from the off-chain distributed storage server; Step 14: Educational archive users in educational institutions use the attribute private key SK i , recalculate the symmetric key S using the fast pairing attribute-based encryption method key′ ; Step 15: The educational archive user in the educational institution uses the recalculated symmetric key S key′ Decrypt the retrieved ciphertext education file CTF′ to obtain the final education file Doc′; In the above, i∈[1,V], V is the number of educational institutions.

2. The secure, efficient, searchable, attribute encryption sharing method based on blockchain according to claim 1 is characterized in that: The fast pairing attribute-based encryption method is implemented based on Type-III asymmetric prime-order bilinear pairing group.

3. The secure, efficient, searchable, attribute encryption sharing method based on blockchain according to claim 1 is characterized in that: In step 7, the ciphertext keyword set CT I for: Among them, w is the keyword set of the educational archives to be shared, is the collaborative public key, N is the slave collaborative public key The prime number extracted from the collaborative public key Generators extracted from .

4. The secure, efficient, searchable, attribute encryption sharing method based on blockchain according to claim 1 is characterized in that: In step 8, the encrypted index CT Index It is stored in an inverted index structure based on B+-Tree and then uploaded to the blockchain.

5. The secure, efficient, searchable, attribute encryption sharing method based on blockchain according to claim 1 is characterized in that: In step 10, the search keyword set CTw′ is: Among them, w′ is the keyword set of the educational archives of interest, is the collaborative public key, N is the slave collaborative public key The prime number extracted from the collaborative public key Generators extracted from .

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