CN105978695A - Batch self-auditing method for cloud storage data - Google Patents

Abstract

The invention belongs to the technical field of information security, and in particular relates to a batch self-auditing method for cloud storage data. The method of the present invention mainly includes: generating a public-private key pair based on an elliptic curve digital signature algorithm, a public-private key pair of a lightweight signature algorithm, and a lightweight symmetric encryption algorithm: calculating digital signatures of multiple data files, data files Tags and ciphertexts of data files are sent to the cloud server; cloud users generate audit challenge information and send it to the cloud server; the cloud server returns the aggregated audit proof response information to the cloud user; cloud users For the response information, use the digital signature algorithm based on the elliptic curve and the symmetric encryption algorithm to verify the legitimacy of the aggregated audit proof response. The invention has the beneficial effects of solving the problem of verifying the integrity of cloud storage data in batches, enabling users to effectively verify the integrity of multiple data files at the same time.

Description

A Batch Self-Audit Method for Cloud Storage Data

technical field

The invention belongs to the technical field of information security, and in particular relates to a batch self-auditing method for cloud storage data.

Background technique

As an important service model of cloud computing, cloud storage has become increasingly popular. Outsourcing data storage on cloud servers has great advantages over traditional storage models, but at the same time, it also makes users worry about the security and privacy of data stored on cloud servers. worry. First of all, cloud users worry that their data stored on cloud servers may be accessed and abused by unauthorized users, because once the data is stored on cloud servers, cloud users give up the physical control of the data. Second, cloud users worry that their data stored on cloud servers may be lost. Because no matter how reliable the cloud service provider is, it may cause data loss or damage on the cloud storage device. Thirdly, due to some economic interests, cloud service providers often delete some data that is rarely accessed by users to save storage space, and they will not promptly report the real situation to the owner of the deleted data. Therefore, in order to ensure the authenticity and integrity of cloud storage data, cloud users need to verify the integrity of the data stored on the cloud server.

In most cases, in order to ensure the confidentiality of the data, the user's data is first encrypted and then stored on the cloud server. Even so, in the process of verifying the integrity of the user's sensitive data stored on the cloud server, the user does not want to entrust a third-party auditor to help him audit the integrity of the data. This is because some public data stored on cloud servers will be mastered by third-party auditors, which will lead to the threat of leakage of sensitive and important data of cloud users. In addition, most of the current cloud storage data integrity audit methods that support third-party audits are designed using the aggregate digital signature algorithm based on bilinear pairings. However, this requires computationally expensive modular exponents and bilinear pairings operation. The security of the digital signature algorithm based on elliptic curve construction depends on the discrete logarithm problem on the elliptic curve finite group. It has the characteristics of short signature length, small storage space, and fast calculation speed. It is especially suitable for lightweight calculations. The storage space is limited and efficient implementation is required. Therefore, for the application scenarios applicable to the wireless communication environment, it is of great application value to design an elliptic curve-based cloud storage data batch self-audit method with higher privacy protection.

Contents of the invention

The object of the present invention is to solve the above problems, and provide a batch self-audit method for cloud storage data based on elliptic curves.

The technical solution of the present invention is: a batch self-audit method for cloud storage data, characterized in that it comprises the following steps:

a. System initialization, specifically including: generating a public-private key pair based on an elliptic curve-based digital signature algorithm, a public-private key pair for a lightweight signature algorithm for file names, and a lightweight symmetric encryption algorithm:

b. Signature generation, including:

b1. Using the digital signature algorithm based on the elliptic curve described in step a to calculate the digital signatures of multiple data files respectively;

b2. Use the signature algorithm described in step a to digitally sign different data file names to generate data file labels, and use the symmetric encryption algorithm described in step a to encrypt each data file to obtain the ciphertext of the data file ;

b3. The digital signature generated in step b1 and the data file label generated in step b2 and the ciphertext of the data file are sent to the cloud server;

c. Generation of audit certificates, including:

c1. Cloud users generate audit challenge information and send it to the cloud server;

c2. The cloud server generates aggregated audit proof response information of multiple data files according to the audit challenge information, and returns the aggregated audit proof response information to the cloud user;

d. Audit proof verification, specifically including: the cloud user uses the digital signature algorithm based on elliptic curve and symmetric encryption algorithm to verify the legitimacy of the aggregated audit proof response information according to the received aggregated audit proof response information.

Further, the specific method of the step a is:

a1. Define an elliptic curve E on Z _P (modulus p residual class ring), set V to be a point whose upper order is a prime number q, V is the generator of the cyclic group <V>, and p is a large prime number;

a2. Set up a secure lightweight symmetric encryption algorithm The secret key is t; at the same time, a public-private key pair (rpk, rsk) of a lightweight digital signature algorithm is generated;

a3. Randomly select a value z from Z _q to generate the public key K={q,E,V,U} based on the elliptic curve signature algorithm, U=zV is the actual signature public key, and the signature private key is z, Z _q is a remainder class ring modulo q.

Further, the specific method of step b is:

For 1≤l≤L, set each data file bit The file name is name _l , then:

Step b1 is specifically: select random numbers k _l,i ∈ Z _q , and generate digital signatures for each data file f _l,i respectively: δ _l,i = (W _l,i ,r _l,i ,τ _{l, i} ) Among them, W _l,i =k _l,i V=(u _l,i ,v _l,i ), r _l,i =u _l,i mod q, τ _l,i =(r _l,i k _{l, i} +f _l,i z)modq, defining the set of these signatures as

Step b2 is specifically: calling a lightweight digital signature algorithm to calculate the label σ _{l of the file name name l =} name _l ||SSig _rsk (name _l ); calling a symmetric encryption algorithm Encrypt each data block f _l,i as about to encrypted as

Step b3 is specifically: the cloud user sends to the cloud server.

Further, the audit challenge information generated by the cloud user in the step c1 is: from Randomly select a subset C={l ₁ ,…,l _c } containing c elements; for each j∈C, the user generates a corresponding random value ν _j , and finally the cloud user sends an audit challenge message chal={j ,ν _j } _j∈C to the cloud server;

Then in step c2: the cloud server calculates the combined information block and the aggregated signature Finally, the cloud server sends (W,τ,{f _l } _1≤l≤L ,{name _l } _1≤l≤L ) as the audit proof response information to the cloud user.

Further, the specific method of step d is:

Verification equation Whether it is established, if established, the audit proves that the response information is valid, if not established, the audit proves that the response information is invalid; among them,

The invention has the beneficial effects of solving the problem of batch integrity verification of cloud storage data. The inventive method requires the user's original data to be stored in the cloud server in the form of ciphertext, which can effectively ensure the confidentiality of the data. This method uses the elliptic curve digital signature algorithm to construct a homomorphic linear authenticator, which enables users to effectively verify the integrity of multiple data files at the same time, and the amount of calculation and storage required by the designed method are both lightweight It can be effectively applied to the wireless communication network environment.

detailed description

Describe technical scheme of the present invention in detail below:

The steps of the present invention are divided into four parts:

System initialization: The system generates a public-private key pair based on an elliptic curve digital signature algorithm, a public-private key pair for lightweight signatures on file names, and a secure lightweight symmetric encryption algorithm.

Signature generation steps: the user uses the improved Elliptic Curve Signature Algorithm (ECDSA) to calculate their digital signatures for multiple data files, and at the same time digitally signs different data file names to generate data file labels, and stores these multiple sensitive data files Perform symmetric encryption. Finally, these signatures and the ciphertext of the data file are sent to the cloud server, and these data are deleted on the local client.

Audit proof generation steps: In order to batch audit the integrity of the outsourced data stored on the cloud server at the same time, the cloud user generates an audit challenge message and sends the challenge message to the cloud server. After the cloud server receives the challenge information, it generates the aggregated audit proof response information of the multiple data files, and returns it to the cloud user.

Audit proof verification step: After the user obtains the aggregated audit proof response information, use the private key of the elliptic curve signature algorithm and the secret key of the symmetric encryption algorithm to verify the legitimacy of the aggregate audit proof response information.

A specific example is given below:

The batch self-audit method of cloud storage data based on elliptic curve includes the following basic steps: Setup, SigGen, ProofGen, VerifyProof.

System initialization: includes the following three sub-steps:

(1) Define an elliptic curve E on Z _P (modulo p residual class ring, which is a large prime number), set V to be a point whose upper order of E is a prime number q, and V is the generator of the cyclic group <V>, and The discrete logarithm problem on <V> is intractable.

(2) Set a secure lightweight symmetric encryption algorithm The secret key is t. At the same time, the system generates a public-private key pair (rpk, rsk) of a lightweight digital signature algorithm.

(3) Randomly select a value z from Z _q , and calculate the actual signature public key U=zV, generate the public key K={q,E,V,U} of the signature algorithm based on the elliptic curve, and the signature private key is z .

Signature generation step: the cloud user simultaneously generates digital signatures of L data files and their names, and generates the ciphertext of these L data files as follows:

(1) For 1≤l≤L, given each data file The file name is name _l . In order to ensure the uniqueness of the data file name, the cloud user invokes a lightweight digital signature algorithm to calculate the label σ _{l of the file name name l =} name _l ||SSig _rsk (name _l ).

(2) The cloud user uses the private key z of the elliptic curve signature algorithm to generate the signature of each data block f _l,i as follows: select a random number k _l,i ∈ Z _q , calculate W _l,i = k _l,i V = (u _l,i ,v _l,i ), r _l,i =u _l,i modq,τ _l,i =(r _l,i k _l,i +f _l,i z)modq, generating each f _l,i get the digital signature δ _l,i ＝(W _l,i ,r _l,i ,τ _l,i ) Define the set of these signatures as

(3) For 1≤l≤L, given each data file In order to ensure the confidentiality of cloud user data files, cloud users use symmetric encryption algorithms Encrypt each data block f _l,i as so encrypted as

Finally, the cloud user sends to the cloud server and delete the information on the client's local side.

Audit proof generation steps: the cloud user first retrieves the label σ _l of each data file, and verifies the validity of the signature SSig _rsk (name _l ). After verifying the validity of the tag, the cloud user generates audit challenge information as follows: from Randomly select a subset C={l ₁ ,…,l _c } containing c elements; for each j∈C, the user generates a corresponding random value ν _j , and finally the cloud user sends chal={j,ν _j } _j∈C to the cloud server.

Once the audit challenge information chal={j,ν _j } _j∈C is received, the cloud server calculates the combined information block and the aggregated signature Finally, the cloud server sends (W,τ,{f _l } _1≤l≤L ,{name _l } _1≤l≤L ) as the audit proof response information to the cloud user.

Audit proof verification steps: The cloud user verifies the validity of the audit proof response information according to the following steps:

(1) For each 1≤l≤L, calculate

(2) Verification equation Whether it is established.

The audit proof verifies the correctness of the process as follows:

such equation established.

The invention provides a batch self-auditing method for cloud storage data based on elliptic curves. The audit method is designed using an aggregate digital signature algorithm based on elliptic curve construction. Its security is based on the discrete logarithm problem, which can ensure that malicious cloud servers cannot generate fake audit proof response information to deceive cloud users through the audit verification process. In the audit method, cloud users use elliptic curve aggregation digital signatures to construct a homomorphic linear authenticator, which can audit the integrity of multiple data files in batches at the same time, and the audit process can successfully verify the data stored in the cloud with only a limited number of calculations. The data integrity on the server does not require the computationally expensive modular exponent operation and bilinear pairing operation. It is especially suitable for application scenarios that require lightweight calculations, limited storage space, and need to efficiently implement wireless sensor networks.

Claims (5)

1. A batch self-auditing method for cloud storage data is characterized by comprising the following steps:

a. the system initialization specifically comprises the following steps: generating a public and private key pair of a digital signature algorithm based on an elliptic curve, a public and private key pair of a signature algorithm for carrying out lightweight signature on a file name, and a lightweight symmetric encryption algorithm:

b. the signature generation specifically comprises:

b1. respectively calculating the digital signatures of a plurality of data files by using the digital signature algorithm based on the elliptic curve in the step a;

b2. respectively carrying out digital signature on different data file names by using the signature algorithm in the step a to generate data file labels, and encrypting each data file by using the symmetric encryption algorithm in the step a to obtain a ciphertext of the data file;

b3. transmitting the digital signature generated in the step b1, the data file label generated in the step b2 and the ciphertext of the data file to a cloud server;

c. and generating an audit certification, specifically comprising:

c1. the cloud user generates audit challenge information and sends the audit challenge information to the cloud server;

c2. the cloud server generates aggregated audit certification response information of the multiple data files according to the audit challenge information and returns the aggregated audit certification response information to the cloud user;

d. the audit certification verification specifically comprises the following steps: and the cloud user verifies the validity of the aggregated audit certificate response information by using a digital signature algorithm and a symmetric encryption algorithm based on an elliptic curve according to the received aggregated audit certificate response information.

2. The batch self-auditing method for cloud storage data according to claim 1, characterized in that the specific method of step a is as follows:

a1. is defined as one in Z_PAn elliptic curve E on (modulo p residual class ring) with V being a point of prime q on the order of E and V being a cyclic group<V>P is a large prime number;

a2. setting a safe lightweight symmetric encryption algorithmThe secret key is t; simultaneously generating a public and private key pair (rpk, rsk) of a lightweight digital signature algorithm;

a3. from Z_qRandomly selecting a value Z, generating a public key K ═ { q, E, V, U } of a signature algorithm based on an elliptic curve, taking U ═ zV as a signature public key, and taking a signature private key Z, Z as a signature private key_qIs a modulo-q residual class ring.

3. The batch self-auditing method for cloud storage data according to claim 2, characterized in that the specific method of step b is as follows:

for L is more than or equal to 1 and less than or equal to L, each data file is set asThe name of the file is name_lAnd then:

the step b1 is specifically as follows: selecting a random number k_l,i∈Z_qGenerating each data file f separately_l,iThe digital signature of (a) is:wherein, W_l,i＝k_l,iV＝(u_l,i,v_l,i)，r_l,i＝u_l,imod q，τ_l,i＝(r_{l, i}k_l,i+f_l,iz) modq, defining the set of these signatures as

The step b2 is specifically as follows: calling a lightweight digital signature algorithm to calculate the name of the file_lTag sigma of_l＝name_l||SSig_rsk(name_l) (ii) a Invoking symmetric encryption algorithmsEach data block f_l,iIs encrypted asThat is to say, theIs encrypted as

The step b3 is specifically as follows: cloud user deliveryTo the cloud server.

4. The batch self-auditing method for cloud storage data according to claim 3, wherein the auditing challenge information generated by the cloud user in step c1 is: fromIn which a subset C containing C elements is randomly chosen, { l ═₁,…,l_cFor each j ∈ C, the user generates a corresponding random value v_jFinally, the cloud user sends audit challenge information chal ═ j, v_j}_j∈CSending the data to a cloud server;

then in step c 2: cloud server computing combined information blockAnd aggregate signaturesFinally, the cloud server sends (W, τ, { f)_l}_1≤l≤L,{name_l}_1≤l≤L) And sending the audit certification response information to the cloud user.

5. The batch self-auditing method for cloud storage data according to claim 4, characterized in that the specific method of step d is as follows:

validation equationWhether the information is established or not, if so, the audit certification response information is valid, and if not, the audit certification response information is invalid; wherein,