Autonomous path access authorization method for encrypted data in cloud storage environment

Abstract

The invention relates to an autonomous path access authorization method for encrypted data in a cloud storage environment, and belongs to the field of cloud data security. The method comprises the steps that data receivers are divided into a consignor and an acceptor, the consignor and a data owner are located in an IBE password system, the acceptor is located in an IPE password system, and the data owner carries out IBE encryption on a plaintext according to the identity of the consignor and uploads the plaintext to a cloud server; the delegator uses an autonomous path generation algorithm to generate an access path composed of access vectors with priorities from high to low, and a re-encryption key; and the cloud server re-encrypts the IBE ciphertext into an IPE ciphertext according to the re-encryption key and sends the IPE ciphertext to the acceptor. By using the method provided by the invention, the privacy information of the data receiver can be protected, and the data user not only can realize one-to-many access authorization, but also can specify the priority of a plurality of groups of acceptors, thereby ensuring that the decryption authority of the data in a multi-hop scene is always authorized to the credible acceptor.

Description

Technical Field

[0001] The present invention belongs to the technical field of cloud data security, and particularly relates to an autonomous path access authorization method for encrypted data in a cloud storage environment. Background Art

[0002] The rise of cloud computing has unlocked massive storage and computing resources for individual and enterprise users. Through cloud services, individuals and enterprises can efficiently and reliably achieve data transmission, storage, and distribution between the sender and the receiver. As the network environment faced by cloud servers becomes increasingly complex, user data is often stored in encrypted form in the cloud. For example, in an email system, the sender uses Alice's public key to encrypt an email and sends the ciphertext to Alice and stores it in the email server. However, Alice may not be able to process these emails in a timely manner due to certain reasons and hopes to forward the emails to her secretary Bob for processing. But since the ciphertext is encrypted with Alice's public key, Bob cannot decrypt these ciphertexts, so this encryption method lacks flexibility.

[0003] Therefore, the proxy re-encryption (PRE) technology has emerged, providing a new solution for access authorization of encrypted data. The PRE technology allows a third-party proxy to convert the data that the initial recipient can decrypt into data that the new recipient can decrypt, thus realizing access authorization for encrypted data. To cope with more complex application scenarios, some researchers have proposed cross-system proxy re-encryption schemes, which can convert the ciphertext of one encryption system into the ciphertext within another system. In particular, a fast and secure unbounded cross-domain proxy re-encryption scheme (FABRIC) can achieve the conversion of ciphertext from an identity-based encryption (IBE) scheme to an attribute-based encryption (ABE) scheme.

[0004] Based on the PRE technology, FABRIC can achieve cross-system access authorization for encrypted data in cloud computing. The entities involved include a trusted authorization authority, a cloud server, a data owner, and a data user. As Figure 1 shown, the implementation process of FABRIC includes the following steps:

[0005] 1) System initialization. The trusted authorization authority generates a system public key PK and a system master key MSK.

[0006] 2) IBE key generation. The trusted authorization authority generates a key SK ID based on the system public key PK, the system master key MSK, and the user ID and securely distributes it to the data user.

[0007] 3) ABE key generation. The trusted authorization authority generates a key SK Sand securely distribute it to data users.

[0008] 4) Data encryption. The sender inputs the system public key PK, the plaintext m, and the data user's identity ID to obtain the original ciphertext C ID and upload it to the cloud server.

[0009] 5) Re-encryption key generation. The original data user inputs the system public key PK, its secret key SK ID , and the access policy to obtain the re-encryption key RK ID→S and upload it to the cloud server.

[0010] 6) Re-encryption. The cloud server, based on the system public key PK, the original ciphertext C ID and the re-encryption key PK ID→s , obtains the re-encrypted ciphertext C ID→s .

[0011] 7) IBE data decryption. The user obtains the ciphertext C ID from the cloud server and uses the secret key SK ID to decrypt and obtain the plaintext m.

[0012] 8) ABE data decryption. The user obtains the ciphertext C ID→S from the cloud server and uses the secret key SK S to decrypt and obtain the plaintext m.

[0013] In a cloud storage environment, there are the following problems in implementing secure access authorization using FABRIC:

[0014] 1) FABRIC cannot protect the privacy information of data users. Specifically, the implementation of FABRIC access authorization is based on attribute-based encryption (ABE). The ABE ciphertext contains an access policy, and the access policy contains the user's attribute set S. This access policy is used when re-encrypting the ciphertext. Therefore, the re-encrypted ciphertext of this scheme will directly expose the user's attribute set S. The exposure of this information not only concerns the privacy information of data users but also involves the problem of data information leakage because an adversary may indirectly infer data information from the data user's attribute set information.

[0015] 2) FABRIC can only implement single-hop proxy re-encryption. Single-hop proxy re-encryption lacks flexibility, and the re-encrypted ciphertext cannot be re-encrypted. Multi-hop proxy re-encryption can transfer the decryption permission to different users sequentially. For example, if Alice is too busy to process data and delegates the decryption permission of the ciphertext to Bob, and Bob is also too busy to process data, the decryption permission can then be passed to Carol, and so on. Summary of the Invention

[0016] The present invention is an improvement based on the existing encryption data access authorization technology of FABRIC. Aiming at the problems of the existing technology mentioned above, namely, the leakage of user privacy information and the ability to only achieve single-hop proxy re-encryption, the present invention provides an autonomous path access authorization method for encrypted data in a cloud storage environment, realizing cross-system proxy re-encryption and autonomous path proxy re-encryption to meet the requirements of secure data sharing in a cloud storage environment.

[0017] An autonomous path access authorization method for encrypted data in a cloud storage environment proposed by the present invention includes the following steps:

[0018] Step 1: Set up an identity-based encryption scheme IBE and an inner product-based encryption scheme IPE in a trusted authorization agency; the data owner is located in the IBE cryptosystem, and the data receivers are divided into the delegator and the acceptor. The data receivers in the same cryptosystem as the data owner are used as the delegator, and the data receivers in the IPE cryptosystem are used as the acceptor; the data owner encrypts the plaintext using IBE according to the identity of the delegator and uploads it to the cloud server.

[0019] Step 2: When the delegator entrusts the access permission of the ciphertext to the acceptor, the delegator uses the autonomous path generation algorithm to generate an access path composed of access vectors with priorities from high to low, and generates re-encryption keys with different priorities based on this access path and sends them to the cloud server.

[0020] Step 3: The cloud server re-encrypts the IBE ciphertext according to the re-encryption key, converts it into an IPE ciphertext and sends it to the acceptor.

[0021] Step 4: The data receiver decrypts the received ciphertext using its own key; among them, the delegator obtains the IBE ciphertext from the cloud server, and the acceptor obtains the IPE ciphertext from the cloud server.

[0022] The said Step 1 includes:

[0023] Step 1: The trusted authorization agency generates the public parameters and the master key of the encryption system.

[0024] Step 2: The trusted authorization agency uses the IBE key generation algorithm to generate keys for the users in the IBE cryptosystem, and uses the IPE key generation algorithm to generate keys for the users in the IPE cryptosystem.

[0025] Step 3: The data owner encrypts the plaintext m according to the identity ID of the specified receiver.

[0026] The said Step 2 includes Step 4: First, the delegator runs the autonomous path generation algorithm according to its own identity ID, including: randomly selecting l access vectors for the acceptor, sorting the access vectors according to the priorities from high to low, and generating an access path The access vector therein describes the data access rights of the recipient; secondly, the delegator generates a re-encryption key rk ID based on its own secret key sk ID and the access path Pa ID = {rk 0→1 , rk 1→2 , …, rk l-1→l}.

[0027] The third step described above includes step 5: The cloud server generates a re-encrypted ciphertext CT j-1→j based on the re-encryption key rk j-1 and the ciphertext CH j .

[0028] Compared with the existing FABRIC-based encrypted data access authorization, the method of the present invention improves the security and practicality of data access authorization in the cloud storage environment. Specifically, the advantages and positive effects of the present invention are as follows:

[0029] (1) The method of the present invention adopts a more lightweight identity-based encryption at the data encryption end, which is conducive to resource-constrained devices such as Internet of Things devices and mobile devices to perform encryption operations. During data access authorization, it can convert the IBE ciphertext into a one-to-many IPE ciphertext to achieve privacy protection for the recipient, that is, except for the delegator, all other entities cannot infer any information about the recipient from the re-encryption key and the re-encrypted ciphertext. The data recipient (recipient) can only know whether it can decrypt the data, but cannot know the information of other recipients.

[0030] (2) The method of the present invention provides an autonomous path proxy re-encryption mechanism. The delegator can not only implement multi-hop proxy re-encryption, but also specify the priority of the recipient according to the path, so as to ensure that the decryption right of the data is always authorized to a trusted recipient in a multi-hop scenario. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a schematic diagram of the implementation of the existing unbounded cross-domain proxy re-encryption scheme FABRIC;

[0032] Figure 2 is a schematic diagram of the implementation of the method for autonomous path access authorization of encrypted data in the cloud storage environment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0033] The present invention will be further described in detail below with reference to the drawings and embodiments.

[0034] An autonomous path access authorization method for encrypted data in a cloud storage environment proposed by the present invention allows a data owner to store ciphertexts in the cloud using a lightweight encryption scheme. A data user can delegate the access rights of the ciphertext to other users. During this authorization process, the data user can not only achieve one-to-many access authorization but also specify the priorities of multiple groups of recipients, thus ensuring that the decryption rights of the data are always authorized to trusted recipients in a multi-hop scenario. In addition, the privacy information of data recipients will be protected, and the cloud server or external adversaries cannot obtain information about other data recipients. The implementation of the present invention's solution is specifically described below.

[0035] The present invention proposes an autonomous path access authorization method for encrypted data in a cloud storage environment. The entities involved include: a trusted authorization authority, a data owner, a cloud server, and data users, as Figure 2 shown.

[0036] 1) Trusted authorization authority. The trusted authorization authority establishes system public parameters and a system master key and maintains the entire system. At the same time, the trusted authorization authority generates a decryption key for each data user.

[0037] 2) Data owner. The data owner uploads the collected data to cloud storage. Before uploading, the data owner encrypts the data using the user's identity to ensure confidentiality.

[0038] 3) Cloud server. The cloud server is semi-trusted and has rich storage and computing resources. Specifically, the cloud server provides storage services for the ciphertexts of the data owner and provides computing services for converting the ciphertexts into re-encrypted ciphertexts as an agent.

[0039] 4) Data users, i.e., data recipients who want to obtain the data uploaded by the data owner. Data users can be further divided into delegators and recipients. The delegator is a data user within the same cryptographic system as the data owner, i.e., in IBE, and can access the data stored in cloud storage. At the same time, the delegator can create a delegation path and generate re-encryption keys, and the cloud server uses these keys to generate re-encrypted ciphertexts for users on the path. The recipient is a data user in another cryptographic system, i.e., IPE, and can decrypt the re-encrypted ciphertext. In addition, the recipient can give up the access right and notify the agent to re-encrypt for the next group of recipients.

[0040] The autonomous path access authorization method for encrypted data in the cloud storage environment of the present invention has the following algorithm definitions:

[0041] 1) System initialization algorithm Setup(1 λ)→(pp, msk): Input the security parameter λ and output the public parameter pp and the master secret key msk of the encryption system. The inputs of the remaining algorithms implicitly include the parameter pp, which is not explicitly written for simplicity of description.

[0042] 2) IBE Key Generation Algorithm Register IBE (msk, ID)→sk ID : Input the master secret key msk and the identity ID, and output the key sk of this identity. ID .

[0043] 3) IPE Key Generation Algorithm Input the master secret key msk and the predicate vector of the user. Output the key of this vector.

[0044] 4) Original Ciphertext Encryption Algorithm Encrypt(ID, m)→CT 0 : Input the plaintext m and the identity ID of the receiver, and output the original ciphertext CT. 0 .

[0045] 5) Autonomous Path Generation Algorithm CreatPath(ID)→Pa ID : Input the ID of the delegator and output the path Pa sorted from high to low in priority. ID .

[0046] 6) Re-encryption Key Generation Algorithm ReKeyGen(sk ID , Pa ID )→RK ID : Input the key sk ID , and output the re-encryption key RK ID ={rk j-1→j} j＝1,2,…,l .

[0047] 7) Re-encryption Algorithm ReEncrypt(rk j-1→j , CT j-1 )→CT j : Input the re-encryption key rk j-1→j and the ciphertext CT j-1 , and output a re-encrypted ciphertext CT j .

[0048] 8) IBE Decryption Algorithm Decrypt IBE (sk ID , CT 0 )→m: Input the key sk ID and the original ciphertext CT 0 , and output the plaintext m.

[0049] 9) IPE Decryption Algorithm Input key and the re-encrypted ciphertext CT j , and output the plaintext m.

[0050] As Figure 2 shown, the method for autonomous path access authorization of encrypted data in the cloud storage environment according to the embodiment of the present invention includes the following steps.

[0051] Step 1: System initialization, generating the parameters pp and the master secret key msk.

[0052] Select the security parameter λ, and the trusted authorization agency runs the Setup algorithm. Construct a bilinear group of prime order p and the corresponding bilinear map is e: is the target group of the bilinear map. Select random numbers and where is the set of integers of order p, and n is a positive integer.

[0053] Define the hash function H: Calculate the intermediate parameter g 0 = g γ , h 0 = h γ , u = g w , v = h w , Y = e(g, h) αβ . Where [n] represents the set of integers from 1 to n. Generate the public parameter and save the master secret key Finally, the trusted authorization agency saves the master secret key msk and publishes the system parameter pp.

[0054] Step 2: The trusted authorization agency generates keys for the data users.

[0055] The trusted authorization agency runs the Register IBE algorithm and the Register IPE algorithm to generate keys for the users in the IBE cryptosystem and the IPE cryptosystem respectively. Where the Register IBE algorithm takes the user's identity and the master secret key msk as inputs, selects a random number and calculates the parameters and sk 1 = h s , and finally outputs the corresponding user key sk ID = (sk 0,sk 1 ). Register IPE The algorithm takes the user's predicate vector and the master secret key msk as inputs, selects a random number to generate the key where k 0 , k 1 and K 2 are all intermediate parameters, and the user's predicate vector Finally, the trusted authority returns the key to the corresponding data user through a secure channel.

[0056] Step 3: The data owner encrypts the data and uploads the ciphertext to the cloud server.

[0057] Given the plaintext m, the data owner usually specifies the identity ID of a receiver and runs the Enctypt algorithm to encrypt the data. First, randomly select a number and calculate the parameter Finally, generate the ciphertext CT 0 =(C, C 0 , C 1 , C 2 ) and upload it to the cloud server.

[0058] Step 4: When the delegator delegates the access right of the ciphertext to the accepter, the delegator performs access authorization for the accepter and generates a re-encryption key.

[0059] The accepter is the data receiver located in the IPE cryptosystem and needs the delegator to perform access authorization for it. First, the delegator runs the CreatPath algorithm to create an autonomous path to specify the access priority of the accepter. In the embodiment of the present invention, the delegator generates access vectors with different priorities to correspond to accepters with different degrees of trust.

[0060] Specifically, the delegator inputs its own ID into CreatPath(ID), randomly selects l access vectors for the accepter, sorts the access vectors from high to low according to the priority, and generates a path Let the access vector j = 1, 2... l. The access vector describes the data access rights set by the delegator for the accepter. For each access vector, any user whose key satisfies the inner product can be regarded as the accepter authorized by the access vector. l also represents the number of priorities.

[0061] Secondly, the delegator runs the ReKeyGen algorithm to generate the re-encryption key. Specifically, the algorithm takes the delegator's user key sk ID and the access path Pa ID as inputs, and for any j = 1,..., l, randomly selects the data σ j , For j = 1, calculate the intermediate parameter: d 1 = sk 1 , and generate the parameter For j ≥ 2, calculate the intermediate parameter: and generate the parameter

[0062] Finally, the algorithm returns the re-encryption key rk ID = {rk 0→1 , rk 1→2 , …, rk l-1→l}. The delegator sends the re-encryption key to the cloud server.

[0063] Step 5: The cloud server re-encrypts the ciphertext according to the re-encryption key, and converts the IBE ciphertext into an inner product encryption ciphertext.

[0064] The cloud server runs the ReEncrypt algorithm according to the re-encryption key rk j-1→j and the ciphertext CT j-1 .

[0065] When j = 1, CT j-1 = (C, C 0 , C 1 , C 2 ), set the parameter: Calculate the parameter

[0066] When j ≥ 2, Set the parameter: Calculate the parameter E j = E j-1 ·R j ,

[0067] Finally, return the re-encrypted ciphertext to the recipient.

[0068] Step 6: After receiving the ciphertext, the data recipient decrypts the data.

[0069] For the IBE ciphertext CT 0 , the delegator ID runs the Decrypt ID algorithm using sk IBE to decrypt the ciphertext. Specifically, the algorithm first calculates the parameter Then outputs the plaintext m = C / A.

[0070] For the IPE ciphertext CT j , the recipient uses Run Decrypt IPE algorithm to decrypt the ciphertext. Specifically, the algorithm first calculates the parameters:

[0071]

[0072] Then calculate the intermediate parameter Finally, output the plaintext

[0073] As described above, the method of the present invention designs a cross-system proxy re-encryption scheme, and uses lightweight identity-based encryption IBE to ensure the confidentiality of the original data. When a data user wants to authorize other users to access the data, the cloud server converts the IBE ciphertext into an inner product encryption IPE ciphertext to achieve one-to-many data access authorization and privacy protection of the recipient's identity. In addition, autonomous path proxy re-encryption is also implemented. Autonomous path proxy re-encryption is a multi-hop proxy re-encryption that can transfer the decryption permission to different users in sequence. In autonomous path proxy re-encryption, the delegator can independently set the data access path, and the path includes trusted recipients, and the degree of trust of the recipients decreases along the path from high to low. If the recipient in the path cannot complete the decryption, the decryption permission will be automatically delegated to the next group of recipients in the path. In this way, the delegator ensures that the data decryption permission is always authorized to trusted recipients in a multi-hop scenario. Thus, using the method of the present invention, the data owner can store the ciphertext in the cloud using a lightweight encryption scheme. The data user can delegate the access permission of the ciphertext to other users. In this authorization process, the data user can not only achieve one-to-many access authorization, but also specify the priorities of multiple groups of recipients, so as to ensure that the data decryption permission is always authorized to trusted recipients in a multi-hop scenario. In addition, the privacy information of the data recipient will be protected, and the cloud server or external adversaries cannot obtain the information of other data recipients.

[0074] It should be noted that the various example embodiments of the present disclosure can be implemented in hardware or a dedicated circuit, software, firmware, logic, or any combination thereof. Some aspects can be implemented in hardware, while other aspects can be implemented in firmware or software that can be executed by a controller, a microprocessor, or other computing devices. When aspects of the embodiments of the present disclosure are illustrated or described as block diagrams, flowcharts, or using some other graphical representation, it will be understood that the blocks, devices, systems, technologies, or methods described herein can be implemented as non-limiting examples in hardware, software, firmware, dedicated circuits or logic, general hardware or controllers or other computing devices, or some combination thereof.

[0075] Except for the technical features described in the specification, the rest are well-known technologies to those skilled in the art. The present invention omits the description of well-known components and well-known technologies to avoid redundancy and unnecessary limitation of the present invention. The implementation manners described in the above embodiments do not represent all implementation manners consistent with the present application. On the basis of the technical solution of the present invention, various modifications or deformations that can be made by those skilled in the art without creative efforts are still within the protection scope of the present invention.

Claims

1. A method for autonomous path access authorization of encrypted data in a cloud storage environment, characterized in that: include: Step 1: Set up the identity-based encryption scheme IBE and the inner product-based encryption scheme IPE in the trusted authority; The data owner is located in the IBE cryptographic system. The data recipients are divided into entrustors and acceptors. The data recipients located in the same cryptographic system as the data owner are regarded as entrustors, and the data recipients located in the IPE cryptographic system are regarded as acceptors. The data owner encrypts the plaintext with IBE according to the identity of the client and uploads it to the cloud server; Step 2: When the delegator delegates the access rights of the ciphertext to the acceptor, the delegator uses the autonomous path generation algorithm to generate an access path consisting of access vectors with priorities from high to low, and generates a re-encryption key with different priorities based on the access path and sends it to the cloud server; Step 3: The cloud server re-encrypts the IBE ciphertext according to the re-encryption key, converts it into IPE ciphertext and sends it to the recipient; Step 4: The data receiver uses its own key to decrypt the received ciphertext; the client obtains the IBE ciphertext from the cloud server, and the receiver obtains the IPE ciphertext from the cloud server.

2. The method according to claim 1, characterized in that The step 1 includes step 1: a trusted authorization agency generates public parameters and a master key of the encryption system in the following manner: Choose a security parameter λ and construct a bilinear group of prime order p and Create a bilinear map e: is the target group of the bilinear map; choose a random number and is a set of integers of order p; define the hash function H: Calculate intermediate parameters g0=g γ , h0=h γ , u=g w ,v=h w ,Y=e(g,h) αβ ; n is a positive integer, [n] represents a set of integers from 1 to n; Generate public parameters and the master key 3. The method according to claim 1 or 2, characterized in that: The step 1 includes step 2: the trusted authority uses the IBE key generation algorithm to generate a key for the user in the IBE cryptographic system, and uses the IPE key generation algorithm to generate a key for the user in the IPE cryptographic system; wherein, for the user in the IBE cryptographic system, the user key sk is generated according to the user identity ID and the master key msk ID ;sk ID =(sk0,sk1), parameters sk1=h s , random number is a user in the IPE cryptographic system, according to the predicate vector of the user Generate a key with the master key msk in parameter Random Numbers User's predicate vector 4. The method according to claim 1 or 2, characterized in that: The step 1 includes step 3: the data owner encrypts the plaintext m according to the identity ID of the designated recipient, including: selecting a random number Calculation parameters Generate ciphertext CT0=(C, C0, C1, C2).

5. The method according to claim 1 or 2, characterized in that: The step 2 includes step 4: First, the client runs the autonomous path generation algorithm based on its own identity ID, including: randomly selecting l access vectors for the client, sorting the access vectors from high to low priority, and generating an access path. The access vector Describes the data access rights of the assignee. Secondly, the client uses its own key sk ID and access path Pa ID Generate a re-encryption key, including: for any j, choose a random number For j=1, calculate the intermediate parameters: d1=sk1, And generate parameters For j ≥ 2, calculate the intermediate parameters: And generate parameters Set the re-encryption key rk ID ={rk 0→1 ,rk 1→2 ,…,rk l-1→l }.

6. The method according to claim 1 or 2, characterized in that: The step three includes step 5: the cloud server uses the re-encryption key rk j-1→j and ciphertext CT j-1 Generate re-encrypted ciphertext as follows: When j = 1, CT j-1 =(C,C0,C1,C2), set parameters: C j =C, E j =R, Calculation parameters: When j ≥ 2, Setting parameters: C j =C j-1 , Calculation parameter E j =E j-1 ·R j , Generated re-encrypted ciphertext 7. The method according to claim 1 or 2, characterized in that: The fourth step includes step 6: (1) The client receives the IBE ciphertext CT0=(C, C0, C1, C2) from the cloud server and uses its own key sk ID Decrypt CT0, including: calculation parameters Output plaintext m = C / A; (2) The acceptor receives the IPE ciphertext from the cloud server Use your own key CT j Confidential, including: Calculate the parameters first In calculating the intermediate parameters Then output the plain text

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