An Autonomous Path Access Authorization Method for Encrypted Data in a Cloud Storage Environment

Abstract

The present invention is an autonomous path access authorization method for encrypted data in a cloud storage environment, belonging to the field of cloud data security. The method of the present invention includes: dividing data receivers into delegators and accepters, where the delegators and data owners are located in the IBE cryptosystem, and the accepters are located in the IPE cryptosystem. The data owner encrypts the plaintext using IBE according to the identity of the delegator and uploads it to the cloud server; the delegator uses an autonomous path generation algorithm to generate an access path composed of access vectors with decreasing priorities from high to low, as well as a re-encryption key; the cloud server re-encrypts the IBE ciphertext into an IPE ciphertext according to the re-encryption key and sends it to the accepter. Using the method of the present invention, the privacy information of data receivers will be protected. Data users can not only achieve one-to-many access authorization, but also specify the priorities of multiple groups of accepters, so as to ensure that the decryption permission of data is always authorized to trusted accepters in a multi-hop scenario.

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 transmit, store, and distribute data 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 encrypts an email with Alice's public key 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 wishes 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. Therefore, 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 data that can be decrypted by the initial recipient into data that can be decrypted by the new recipient, thereby realizing access authorization of encrypted data. To cope with more complex application scenarios, some researchers have proposed cross-system proxy re-encryption schemes, which can convert ciphertexts in one encryption system into ciphertexts in another system. In particular, a fast and secure unbounded cross-domain proxy re-encryption scheme (FABRIC) can realize the conversion of ciphertexts from an identity-based encryption (IBE) scheme to an attribute-based encryption (ABE) scheme.

[0004] FABRIC can realize cross-system access authorization of encrypted data in cloud computing based on the PRE technology. 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 from the cloud server ID , 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 from the cloud server ID→S , 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 built on attribute-based encryption (ABE). The ABE ciphertext contains an access policy, and the access policy contains the set of user attributes S. This access policy is used when re-encrypting the ciphertext. Therefore, the re-encrypted ciphertext of this scheme will directly expose the set of user attributes 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 set of data user attribute 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 again. Multi-hop proxy re-encryption can transfer the decryption permission to different users in sequence. 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 the 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 accepter. 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 accepter; 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 delegates the access permission of the ciphertext to the accepter, 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 accepter.

[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 accepter 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 accepter, 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] Step 3 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 practicability 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 achieve multi-hop proxy re-encryption, but also specify the priority of the recipient according to the path, so as to ensure that the decryption permission 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 Embodiments

[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, thereby 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 solution of the present invention 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 a data user, 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 ciphertexts into re-encrypted ciphertexts as an agent.

[0039] 4) Data user, i.e., the data recipient who wants to obtain the data uploaded by the data owner. The data user can be further divided into a delegator and a recipient. 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 involves the following defined algorithms:

[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) → CT0: Input the plaintext m and the identity ID of the receiver, and output the original ciphertext CT0.

[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 according to the 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 , CT0) → m: Input the key sk ID and the original ciphertext CT0, and output the plaintext m.

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

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

[0051] Step 1: System initialization, generate 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 g0 = g γ , h0 = 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 data users.

[0055] The trusted authorization agency runs the Register IBE algorithm and the Register IPE algorithm to generate keys for users within the IBE cryptosystem and the IPE cryptosystem respectively. Among them, 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 sk1 = h s , and finally outputs the corresponding user key sk ID = (sk0, sk1). The Register IPE algorithm takes the user's predicate vector and the master secret key msk as inputs, selects a random number to generate the key where k0, k1, and K2 are all intermediate parameters, and the user's predicate vector Finally, the trusted authorization agency 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 CT0 = (C, C0, C1, C2) and upload it to the cloud server.

[0058] Step 4: When the delegator entrusts the access right of the ciphertext to the accepter, the delegator authorizes the access 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 authorize the access 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 trustworthiness.

[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 a re-encryption key. Specifically, this algorithm takes the user key sk of the delegator ID and the access path Pa ID as inputs. For any j = 1,…l, randomly select the data σ j , For j = 1, calculate the intermediate parameter:[[]] d1 = sk1, and generate the parameter For j≥2, calculate the intermediate parameter:[[]] and generate the parameter

[0062] Finally, this algorithm returns the re-encryption key rk ID = {rk0→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, according to the re - encryption key rk j-1→j and the ciphertext CT j-1 , runs the ReEncrypt algorithm.

[0065] When j = 1, CT j-1 =(C, C0, C1, C2), set the parameters: Calculate the parameter

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

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

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

[0069] For the IBE ciphertext CT0, the delegator ID uses sk ID to run the Decrypt IBE algorithm 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 acceptor uses to run the Decrypt IPE algorithm to decrypt the ciphertext. Specifically, the algorithm first calculates the parameters:

[0071]

[0072] Then calculates the intermediate parameter Finally, outputs the plaintext

[0073] As described above, the method of the present invention designs a cross-system proxy re-encryption scheme, and adopts lightweight identity-based encryption (IBE) to ensure the confidentiality of the original data. When a data user wants to authorize data access to other users, 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 sequentially. In autonomous path proxy re-encryption, the delegator can set the data access path independently, and the path includes trusted recipients, and the trust level 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 priority 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 exemplary embodiments of the present disclosure can be implemented in hardware or dedicated circuits, 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, microprocessor, or other computing device. 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, techniques, 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, they are all 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 embodiments described in the above embodiments do not represent all embodiments consistent with the present application. Based on the technical solution of the present invention, various modifications or deformations that can be made by those skilled in the art without creative labor are still within the protection scope of the present invention.

Claims

1. An autonomous path access authorization method for encrypted data in a cloud storage environment, characterized in that Including: 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. The data receivers are divided into the delegator and the accepter. The data receivers in the same cryptosystem as the data owner are taken as the delegator, and the data receivers in the IPE cryptosystem are taken as the accepter; The data owner encrypts the plaintext using IBE according to the identity of the delegator and uploads it to the cloud server; The said Step 1 includes Steps 1 to 3: Step 1: The trusted authorization agency generates the public parameters and the master key of the encryption system, and the generation method is as follows: Select the security parameter λ and construct a bilinear group of prime order p and Establish a bilinear map is the target group of the bilinear map; select random numbers and are the set of integers of order p; define a hash function Calculate the intermediate parameter g0 = g γ , h0 = h γ , u = g w , v = h w , Y = e(g, h) αβ ; n is a positive integer, [n] represents the set of integers from 1 to n; generate the public parameters and the master key Step 2: The trusted authorization agency generates keys for the users within the IBE cryptosystem using the IBE key generation algorithm and generates keys for the users within the IPE cryptosystem using the IPE key generation algorithm; among them, for the users within the IBE cryptosystem, the user key sk is generated according to the user identity ID and the master key msk ID ; sk ID =(sk0, sk1), parameter sk1 = h s , random number For the users within the IPE cryptosystem, according to the predicate vector of the user and the master key msk, generate the key Among them parameter random number Predicate vector of the user Step 3: The data owner encrypts the plaintext m according to the identity ID of the specified recipient, including: selecting a random number Calculating the parameter Generating the ciphertext CT0 = (C, C0, C1, C2); Step 2: When the delegator delegates the access right of the ciphertext to the accepter, 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 and sends a re-encryption key containing different priorities to the cloud server based on this access path; 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 accepter; 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 accepter obtains the IPE ciphertext from the cloud server.

2. The method according to claim 1, wherein The said Step 2 includes Step 4: First, the client runs an autonomous path generation algorithm based on its own identity ID, including: randomly selecting access vectors for the acceptor, sorting the access vectors from highest to lowest priority, and generating an access path Among them, the access vector describes the data access rights of the acceptor. Let Secondly, the delegator generates a re-encryption key according to its own secret key sk ID and the access path Pa ID which includes: for any j, select a random number For j = 1, calculate the intermediate parameter: d1 = sk1, and generate the parameter For j ≥ 2, calculate the intermediate parameter: and generate the parameter Set the re-encryption key<http: / / www.w3.org / 2001 / XMLSchema#double>[ 3. The method according to claim 2, characterized in that, The third step described above includes Step 5: The cloud server generates a re-encrypted ciphertext according to the re-encryption key rk j-1→j and the ciphertext CT j-1 as follows: When j = 1, CT j-1 = (C, C0, C1, C2), set parameters: C j = C, E j = R, Calculate parameters: When j ≥ 2, Set parameter: C j = C j-1 , Calculate parameter E j = E j-1 ·R j , Generated re-encrypted ciphertext 4. The method according to claim 3, wherein The said Step 4 includes Step 6: (1) The trustee receives the IBE ciphertext CT0 = (C, C0, C1, C2) from the cloud server and decrypts CT0 using its own secret key sk ID including: calculating the parameter Output the plaintext m = C / A; (2) The acceptor receives the IPE ciphertext from the cloud server Using its own key For CT j Confidential, including: First calculate the parameters When calculating the intermediate parameters Then output the plaintext

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