CN108229208B - Public auditing method for multi-copy data in cloud storage service - Google Patents

Abstract

The invention discloses a public auditing method for multi-copy data in cloud storage service, which belongs to the field of information security and aims to realize efficient auditing on the integrity of dynamic multi-copy data in a cloud storage environment; the invention includes (1) a key generation step; (2) a user data preprocessing step; (3) preprocessing data of a cloud service side; (4) preprocessing third party auditor data; (5) a challenge step; (6) an evidence generating step; (7) an evidence verification step; (8) dynamically updating data; (9) and (5) batch auditing. The public auditing method provided by the invention can support dynamic updating of multi-copy data and batch auditing of the multi-copy data while ensuring high-efficiency auditing of the multi-copy cloud data.

Description

Public auditing method for multi-copy data in cloud storage service

Technical Field

The invention belongs to the field of information security, and particularly relates to cloud storage-oriented data security audit, which is suitable for integrity open audit of multi-copy data in a cloud storage environment.

Background

With the rapid development of cloud storage technology and its related industries, more and more individuals and enterprises tend to outsource their data to the cloud to improve the reliability of data storage and reduce their maintenance overhead. However, cloud storage also poses many security issues while providing convenience to users. In particular, due to the separation of data ownership and administrative rights, it is difficult for a user to verify the integrity of data in a conventional manner, thereby allowing a trust gap between the user and the cloud service.

In recent years, with the appearance and popularization of multi-copy storage service in the cloud, people gradually attract attention to the security audit problem facing multi-copy data. Curtmola et al, focusing on The problem for The first time, proposed a multi-copy data possession certification scheme, which uses RSA signature and random mask technology to realize integrity audit on multi-copy data, but does not support public audit (see Curtmola R, Khan O, Burns R, et al. MR-PDP: Multiple-repeatable data processing [ C ]// Distributed Computing Systems,2008.ICDCS'08.The 28th International Conference on. IEEE,2008: 411-; hao et al propose a Boneh-Lynn-Shacham signature scheme based on which public auditing of multi-copy Data is achieved (see Hao Z, Yu N.A multiple-duplication Data publication checking protocol with public verification [ C ]// Data, Privacy and E-Commerce (ISDPE),2010Second International Symposium on.IEEE 2010: 84-89); chen et al, on this basis, present a multi-user multi-copy data-consistent batch audit scheme (see Chenfeng, forest cypress, Yang 26104, etc.. BLS-based multi-user multi-copy data-consistent batch audit [ J ] Cryptographic report 2014, (04): 368) 378). However, none of these schemes support dynamic updating of multiple copies of data. To achieve Dynamic auditing of Multiple Copies of Data, Liu et al (see Liu C, Chen J, Yang L T, et al. automated publishing of Dynamic big Data storage on closed with efficient vertical extent fine-grained updates [ J ]. IEEE Transactions on Parallel and Distributed Systems,2014,25(9): 2234-. The former uses a MR-MHT tree combined by a plurality of Merkle hash trees as an authentication structure of multi-copy dynamic data. The latter abandons the index hash table to record the data block sequence number, designs the version mapping table as the authentication structure, and avoids the label generation to be related to the corresponding data block sequence number. Compared with the former, the data dynamic updating is more efficient. However, since it needs to aggregate tags with the same sequence number in different copies, the tag generation overhead is large.

Aiming at the problems existing in the existing research, the invention provides a novel integrity auditing scheme of multi-copy data. The method and the system support dynamic updating of the multi-copy data and batch auditing of the multi-copy data (namely, a third party auditor can audit tasks from multiple users at one time) while ensuring efficient auditing of the multi-copy cloud data.

Disclosure of Invention

The invention provides a public auditing method for multi-copy data in cloud storage service, and aims to provide efficient public auditing of the integrity of the multi-copy cloud data and support dynamic updating of the multi-copy data and batch auditing of the multi-copy data.

The invention adopts the following technical scheme:

a public auditing method for multi-copy data in cloud storage service comprises the following steps:

(1) a key generation step: a user generates a key pair, namely a private key SK is { x }, and a public key PK is { g, u, v, y }; the user saves the private key SK and issues the public key PK to the cloud service party and the third party auditor; wherein x is a set of integers Z_pIn (3), u, v are cyclic groups G of order prime p₁G is a cyclic group G whose order is a prime number p₂And y is g^x；

(2) User data preprocessing step: a user firstly generates a file identification ID for a file F to be processed; and divides file F into n data blocks, i.e. F ═ b₁，b₂，···，b_nIn which b is_i(i ═ 1, 2.. times, n) is the ith data block; simultaneously recording version information of each data block to obtain a set phi { (v)_i，t_i) I is more than or equal to 1 and less than or equal to n, wherein v_i，t_iAre respectively data block b_iVersion number and timestamp of; in addition, the user also assigns each data block b_iGenerating a corresponding digital signature σ_iSo as to obtain the digital signature set Λ ═ σ { (σ ═ σ }_iI is more than or equal to 1 and less than or equal to n; subsequently, t different copy files are generated by inserting different random masks into the data blocks, and the multiple copy set is recorded as FS ═ { F'₁,F’₂,…,F’_tOf which is F'_j( j 1, 2.. times, t) is the jth copy file; finally, the user saves the file identification ID and the version information phi by a third party auditor, sends the file identification ID, the data block signature set Lambda and the multi-copy set FS to a cloud service party, and then deletes all the numbers except the private keyAccordingly;

(3) preprocessing data of a cloud server side: after receiving a multi-copy set FS, a data block signature set Lambda and a file identification ID sent by a user, a cloud service party firstly signs a sigma on each data block_iCarrying out bilinear pairing calculation to obtain a data block label omega_iI.e. omega_i＝e(σ_iG), and set of tags Ω ═ ω { ω ═ ω_iI is more than or equal to 1 and less than or equal to n, and simultaneously storing each copy in different servers;

(4) a third party auditor data preprocessing step: the third party auditor identifies the file ID and the version information phi transmitted by the user { (v)_i，t_i) And i is more than or equal to 1 and less than or equal to n is stored in the dynamic hash table so as to realize auditable data freshness (latest version state). A dynamic hash table is a newly proposed authentication data structure for supporting data dynamics (see Tian H, Chen Y, Chang C, et al]IEEE Transactions on Services Computing,2017, 10(5):701-714) is essentially a two-dimensional table in which a plurality of files are organized in an array manner and version information of each data block in each file is organized in a linked list manner.

(5) The challenge step is as follows: responding to the user audit request or periodically auditing the data on behalf of the user by a third party auditor, first generating challenge information including randomly selected data block sequence number set psi { [ PSI ]_s1,2, …, c, random number set t ═ r_s|r_s∈Z_pS-1, 2, …, c }, and a random mask R-y^aWherein c is the number of data blocks needing to be challenged in each copy file, and a is an integer set Z_pA medium random number; subsequently, the third party auditor sends challenge information (Ψ, Τ, R) to the cloud service party;

(6) an evidence generation step: after the cloud service party receives the challenge information of the third party auditor, data-bearing evidence needs to be generated, wherein the data-bearing evidence comprises a tag evidence theta and a data block evidence set Pp ═ ρ {_jJ is more than or equal to 1 and less than or equal to t, wherein rho_jThe data block evidence of the jth copy file; evidence information (Θ, Ρ) is then returned to the third party reviewCounting;

(7) and (3) evidence verification step: the third party auditor verifies the evidence information (Θ, p) returned by the cloud service party; if the verification is successful, the multiple copies of the file are complete; otherwise, it indicates that the data in some multi-copy files has been damaged;

(8) and a data dynamic updating step: when data needs to be updated (including modification, insertion and deletion), a user needs to send update information U to a third-party auditor_TPASending update information U to cloud service side_CSP(ii) a After receiving the update information, the third party auditor updates the dynamic hash table accordingly, and the cloud service party updates the corresponding data block and the corresponding label.

(9) Batch auditing step: when w different users simultaneously initiate audit requests, the cloud service side respectively generates label evidence theta for each user_kAnd data block evidence set p_k＝{ρ_k,jJ is less than or equal to 1 and less than or equal to t, wherein k is 1, 2. Then, all the label evidences are aggregated again to obtain a label batch audit evidence theta_BAnd aggregating the data block evidences of different copy files of each user again to obtain a data block batch audit evidence set f ═ { Ρ ^ p_BjJ is more than or equal to 1 and less than or equal to t }; subsequently, the cloud service party will audit the evidence (Θ)_BR) to a three-party auditor; the third party auditor verifies the batch audit evidence; if the verification is successful, the multiple copies of the files of all the users are complete; otherwise, it indicates that the data in some of the multiple copies has been corrupted.

Preferably, the user data preprocessing step includes the following processes:

(2.1) firstly, generating a file identification ID for a file F to be processed by a user; and divides file F into n data blocks, i.e. F ═ b₁，b₂，···，b_n) Wherein b is_iIs the ith data block; simultaneously recording version information of each data block to obtain a set phi { (v)_i，t_i) I is more than or equal to 1 and less than or equal to n, wherein v_i，t_iAre respectively data block b_iVersion number and timestamp of; in addition, the user also assigns each data block b_iGenerating corresponding numbersSignature sigma_iThe calculation process is as follows:

where H (-) is a secure hash function whose function is to map a string to a set of integers Z_pThe above step (1);

(2.2) the user generates t different copy files by inserting different random masks into the data blocks, and records that the multiple copy sets are FS ═ F'₁,F’₂,…,F’_t) Of which is F'_j＝{m_j,1，m_j,2，…，m_j,nJ is 1,2, t, and m_j,i(i-1, 2, …, n) is composed of data block b_iDifferentiation is obtained, and the calculation process is as follows:

m_j,i＝b_i+H(v_i||t_i||j)。

(2.3) the user passes the file identification ID and the version information phi to a third party auditor for storage, and sets the file identification ID and the data block signature lambda as { sigma ═ sigma_iAnd |1 is not less than i and not more than n and the plurality of copy sets FS are sent to the cloud service side, and then all data except the private key are deleted.

Preferably, the evidence generating step includes the following processes:

(6.1) after receiving the challenge information of the third party auditor, the cloud service side firstly generates a label evidence for the multiple copies of the files, and the calculation process is as follows:

wherein the content of the first and second substances,

is a multi-copy document_sA tag of each data block;

(6.2) the cloud service side generates data block evidence rho for each copy file_j(j ═ 1,2, …, t), which is calculated as:

wherein e is a bilinear mapping function;

is the jth copy file_sA data block;

(6.3) the cloud service side will evidence information (Θ, p ═ ρ {_jJ is more than or equal to 1 and less than or equal to t) to the third party auditor.

Preferably, the evidence verification step includes the following processes:

the third party auditor substitutes the evidence information (Θ, p) returned by the cloud service party into the following equation for verification:

wherein the content of the first and second substances,

are respectively phi_sA data block

Version number and timestamp of; if the equation is established, the multiple copies of the file are complete; otherwise, it indicates that the data in some of the multiple copies has been corrupted.

Preferably, the step of dynamically updating the data includes the following steps:

(8.1) data block modification: if the user needs to put the ith data block b of the file F into the file_iModified as b_i', the user is first b_i' Generation of version information (v)_i’，t_i') and then sends update information U_TPA＝(ID，modify，i，v_i’，t_i') to a third party auditor, wherein the ID is an identifier of the file F;modify represents an update operation as a modification. The third party auditor receives the update information U_TPAThen, find the version information of the ith data block of the file F in the dynamic hash table, and replace it with (v)_i’，t_i'). In addition, the user needs to generate a new signature for the modified data block

And t data block copies M '═ M'_j,i＝b_i’+H(v_i’||t_i' | j) |1 ≦ j ≦ t }, and then update information U is sent_CSP＝(ID，modify，i，M’，σ’_i) Giving the cloud service party, wherein the ID is the identifier of the file F; modify represents an update operation as a modification. The cloud service side receives the update information U_CSPAfterwards, sign σ 'to the digit'_iReprocessing to obtain a data block label omega'_i＝e(σ’_iG), then updates are made to the i-th data block tag and the multiple copies, i.e., ω is_iIs replaced by ω'_iCopy the data block m_j,iIs replaced by m'_j,i，j＝1,2,…,t。

(8.2) data block insertion: b is inserted behind ith data block of file F according to user requirement^*The user is first b^*Generating version information (v)^*，t^*) Then sends update information U_TPA＝(ID，insert，i，v^*，t^*) Giving a third party auditor, wherein the ID is the identifier of the file F; insert stands for update operation as insert. The third party auditor receives the update information U_TPAThen, finding the position of the i-th data block version information of the file F in the dynamic hash table, and inserting the version information (v) after the position^*，t^*). In addition, the user needs to generate a new signature σ for the inserted data block^*＝(vH^(v*||t*)u^b*)^xAnd t data block copies M^*＝{m^* _j＝b^*+H(v^*||t^*J is more than or equal to 1 and less than or equal to t, and then update information U is sent_CSP＝(ID，insert，i，M^*，σ^*) To the cloud server, where ID is of file FAn identifier; insert stands for update operation as insert. The cloud service side receives the update information U_CSPThen, sign the digital signature σ^*The data block label omega is obtained by reprocessing^*＝e(σ^*G) will then tag ω at the ith data block_iRear insert tag omega^*And at data block copy m_j,iPost-insertion data block m^* _j，j＝1,2,…,t。

(8.3) data block deletion: if the user needs to put the ith data block b of the file F into the file_iDeleting, the user sends the updated information U_TPAGiving (ID, delete, i) to the third party auditor, wherein ID is the identifier of file F; delete represents the update operation as delete. The third party auditor receives the update information U_TPAAnd then finding the version information of the ith data block of the file F in the dynamic hash table, and deleting the version information. In addition, the user sends update information U_CSPGiving (ID, delete, i) to the cloud server, wherein ID is an identifier of file F; delete represents the update operation as delete. The cloud service side receives the update information U_CSPThen, tag ω will be tagged at the ith data block_iDelete, and delete b at the same time_iAll data block copies of, i.e. { m_j,i|j＝1,2,…,t}。

Preferably, the batch auditing step comprises the following processes:

(9.1) when w different users simultaneously initiate audit requests, the cloud service side respectively generates label evidence theta for each user_kAnd data block evidence set p_k＝{ρ_k,jJ is more than or equal to 1 and less than or equal to t }; wherein, the label evidence theta_kThe calculation process of (2) is as follows:

wherein the content of the first and second substances,

is the k-th user_sA tag; r is_k,sAn s-th random number that is a set of random numbers in the challenge information about the k-th user;

each element ρ in the data block evidence set_k,jThe calculation process of (2) is as follows:

wherein u is_kIs the public key of the kth user; r_kIs the random mask of the kth user in the challenge information;

is the jth psi in the jth copy file of the kth user_sA data block;

(9.2) the cloud service party aggregates all the label evidences again to obtain a label batch audit evidence theta_BThe calculation process is as follows:

and aggregating the data block evidences of different copy files of each user again to obtain a data block batch audit evidence set f ═ { PiB_jJ ≦ 1 ≦ t }, where Pp_BjThe calculation process of (2) is as follows:

(9.3) the cloud service party audits the evidence (theta) in batches_BR) to a three-party auditor.

(9.4) the third party auditor audits the batch audit evidence (theta) returned by the cloud service party_BR) into the following equation:

wherein v is_k，u_kAre public keys of the kth user;

phi's for the k-th user respectively_sA data block

Version number and timestamp of; r_kIs a random mask of the kth user in the challenge information, an

Wherein y is_kIs the public key of the kth user, a is the integer set Z_pA medium random number;

if the equation is established, the multiple copies of the file are complete; otherwise, it indicates that the data in some of the multiple copies has been corrupted.

The technical scheme provided by the invention has the beneficial effects that:

the public auditing method provided by the invention can support dynamic updating of multi-copy data and batch auditing of the multi-copy data while ensuring high-efficiency auditing of the multi-copy cloud data.

The present invention is described in further detail with reference to the accompanying drawings and embodiments, but the method for public auditing multiple copies of data in a cloud storage service according to the present invention is not limited to the embodiments.

Drawings

FIG. 1 is a timing diagram illustrating an audit according to an embodiment of the present invention;

FIG. 2 is a diagram of a dynamic hash table according to an embodiment of the present invention;

FIG. 3 is a timing diagram illustrating dynamic update of data according to an embodiment of the present invention.

Detailed Description

The invention is further described below by means of specific embodiments.

The invention provides a public auditing method for multi-copy data in cloud storage service, which is further explained by combining the attached drawings.

Referring to fig. 1, the public auditing method for multiple copies of data in cloud storage service of the present invention includes a key generation step, a user data preprocessing step, a cloud service side data preprocessing step, a third party auditor data preprocessing step, a challenge step, an evidence generation step, and an evidence verification step, and specifically includes the following steps:

1. a key generation step: a user generates a key pair, namely a private key SK is { x }, and a public key PK is { g, u, v, y }; the user saves the private key SK and issues the public key PK to the cloud service party and the third party auditor; wherein x is a set of integers Z_pIn (3), u, v are cyclic groups G of order prime p₁G is a cyclic group G whose order is a prime number p₂And y is g^x；

2. The user data preprocessing step comprises the following processes:

2.1 the user firstly generates a file identification ID for a file F to be processed; and divides file F into n data blocks, i.e. F ═ b₁，b₂，···，b_n) Wherein b is_iIs the ith data block; simultaneously recording version information of each data block to obtain a set phi { (v)_i，t_i) I is more than or equal to 1 and less than or equal to n, wherein v_i，t_iAre respectively data block b_iVersion number and timestamp of; in addition, the user also assigns each data block b_iGenerating a corresponding digital signature σ_iThe calculation process is as follows:

where H (-) is a secure hash function whose function is to map a string to a set of integers Z_pThe above step (1);

2.2 the user generates t different copy files by inserting different random masks into each data block, and records the multiple copy sets as FS ═ F'₁,F’₂,…,F’_t) Of which is F'_j＝{m_j,1，m_j,2，…，m_j,nJ is 1,2, t, and m_j,i(i-1, 2, …, n) is composed of data block b_iDifferentiation is obtained, and the calculation process is as follows:

m_j,i＝b_i+H(v_i||t_i||j)。

2.3 the user passes the file identification ID and the version information phi to a third party auditor for storage, and sets the file identification ID and the data block signature lambda are { sigma }_iAnd |1 is not less than i and not more than n and the plurality of copy sets FS are sent to the cloud service side, and then all data except the private key are deleted.

3. Preprocessing data of a cloud server side: after receiving a multi-copy set FS, a data block signature set Lambda and a file identification ID sent by a user, a cloud service party firstly signs a sigma on each data block_iCarrying out bilinear pairing calculation to obtain a data block label omega_iI.e. omega_i＝e(σ_iG), and set of tags Ω ═ ω { ω ═ ω_iI is more than or equal to 1 and less than or equal to n, and simultaneously storing each copy in different servers;

4. a third party auditor data preprocessing step: the third party auditor identifies the file ID and the version information phi transmitted by the user { (v)_i，t_i) And i is more than or equal to 1 and less than or equal to n is stored in the dynamic hash table so as to realize auditable data freshness (latest version state). A dynamic hash table is a newly proposed authentication data structure for supporting data dynamics (see Tian H, Chen Y, Chang C, et al]IEEE Transactions on Services Computing,2017, 10(5):701-714), as shown in FIG. 2, the dynamic hash table is essentially a two-dimensional table, in which a plurality of files are organized in an array manner, and version information of each data block in each file is organized in a linked list manner.

5. The challenge step is as follows: responding to the user audit request or periodically auditing the data on behalf of the user by a third party auditor, first generating challenge information including randomly selected data block sequence number set psi { [ PSI ]_s1,2, …, c, random number set t ═ r_s|r_s∈Z_pS-1, 2, …, c }, and a random mask R-y^aWherein c is the number of data blocks needing to be challenged in each copy file, and a is an integer set Z_pA medium random number; the third party auditor then sends the challenge information (Ψ,sending the T, R) to a cloud service side;

6. the evidence generating step includes the following processes:

6.1 after the cloud service side receives the challenge information of the third party auditor, firstly generating a label evidence for the multiple copies of the file, wherein the calculation process is as follows:

wherein the content of the first and second substances,

is a multi-copy document_sA tag of each data block;

6.2 cloud service side generates data block evidence rho for each copy file_j(j ═ 1,2, …, t), which is calculated as:

wherein e is a bilinear mapping function;

is the jth copy file_sA data block;

6.3 cloud service side will evidence information (Θ, p ═ ρ { (ρ })_jJ is more than or equal to 1 and less than or equal to t) to the third party auditor.

7. The third party auditor substitutes the evidence information (Θ, p) returned by the cloud service party into the following equation for verification:

wherein the content of the first and second substances,

are respectively the firstψ_sA data block

Version number and timestamp of; if the equation is established, the multiple copies of the file are complete; otherwise, it indicates that the data in some of the multiple copies has been corrupted.

Referring to fig. 3, the time sequence diagram of the dynamic data update of the present invention includes that a user sends update information, a third party auditor performs update, and a cloud service party performs update.

8.The step of dynamically updating data comprises the following processes:

8.1 when data needs to be updated (including modification, insertion and deletion), a user needs to send update information U to a third party auditor_TPASending update information U to cloud service side_CSP(ii) a After receiving the update information, the third party auditor updates the dynamic hash table accordingly, and the cloud service party updates the corresponding data block and the corresponding label.

8.2 data Block modification: if the user needs to put the ith data block b of the file F into the file_iModified as b_i ^’The user is first b_i' Generation of version information (v)_i’，t_i') and then sends update information U_TPA＝(ID，modify，i，v_i’，t_i') to a third party auditor, wherein the ID is an identifier of the file F; modify represents an update operation as a modification. The third party auditor receives the update information U_TPAThen, find the version information of the ith data block of the file F in the dynamic hash table, and replace it with (v)_i’，t_i'). In addition, the user needs to generate a new signature for the modified data block

And t data block copies M '═ M'_j,i＝b_i’+H(v_i’||t_i' | j) |1 ≦ j ≦ t }, and then update information U is sent_CSP＝(ID，modify，i，M’，σ^’ _i) Giving the cloud service party, wherein the ID is the identifier of the file F; modify represents an update operation as a modification. CloudThe server receives the update information U_CSPAfterwards, sign σ 'to the digit'_iReprocessing to obtain a data block label omega'_i＝e(σ’_iG), then updates are made to the i-th data block tag and the multiple copies, i.e., ω is_iIs replaced by ω'_iCopy the data block m_j,iIs replaced by m'_j,i，j＝1,2,…,t。

8.3 data Block insertion: b is inserted behind ith data block of file F according to user requirement^*The user is first b^*Generating version information (v)^*，t^*) Then sends update information U_TPA＝(ID，insert，i，v^*，t^*) Giving a third party auditor, wherein the ID is the identifier of the file F; insert stands for update operation as insert. The third party auditor receives the update information U_TPAThen, finding the position of the i-th data block version information of the file F in the dynamic hash table, and inserting the version information (v) after the position^*，t^*). In addition, the user needs to generate a new signature σ for the inserted data block^*＝(v^H(v*||t*)u^b*)^xAnd t data block copies M^*＝{m^* _j＝b^*+H(v^*||t^*J is more than or equal to 1 and less than or equal to t, and then update information U is sent_CSP＝(ID，insert，i，M^*，σ^*) Giving the cloud service party, wherein the ID is the identifier of the file F; insert stands for update operation as insert. The cloud service side receives the update information U_CSPThen, sign the digital signature σ^*The data block label omega is obtained by reprocessing^*＝e(σ^*G) will then tag ω at the ith data block_iRear insert tag omega^*And at data block copy m_j,iPost-insertion data block m^* _j，j＝1,2,…,t。

8.4 data Block deletion: if the user needs to put the ith data block b of the file F into the file_iDeleting, the user sends the updated information U_TPAGiving (ID, delete, i) to the third party auditor, wherein ID is the identifier of file F; delete represents the update operation as delete. The third party auditor receives the update information U_TPAThen in a dynamic stateAnd finding the version information of the ith data block of the file F in the hash table, and deleting the version information. In addition, the user sends update information U_CSPGiving (ID, delete, i) to the cloud server, wherein ID is an identifier of file F; delete represents the update operation as delete. The cloud service side receives the update information U_CSPThen, tag ω will be tagged at the ith data block_iDelete, and delete b at the same time_iAll data block copies of, i.e. { m_j,i|j＝1,2,…,t}。

9. The batch auditing step comprises the following processes:

9.1 when w different users simultaneously initiate audit requests, the cloud service side respectively generates a label evidence theta for each user_kAnd data block evidence set p_k＝{ρ_k,jJ is more than or equal to 1 and less than or equal to t }; wherein, the label evidence theta_kThe calculation process of (2) is as follows:

wherein the content of the first and second substances,

is the k-th user_sA tag; r is_k,sAn s-th random number that is a set of random numbers in the challenge information about the k-th user;

each element ρ in the data block evidence set_k,jThe calculation process of (2) is as follows:

wherein u is_kIs the public key of the kth user; r_kIs the random mask of the kth user in the challenge information;

is the jth psi in the jth copy file of the kth user_sA data block;

9.2 the cloud service side carries out polymerization again on all the label evidences to obtain label batch examinationCalculate evidence Θ_BThe calculation process is as follows:

and aggregating the data block evidences of different copy files of each user again to obtain a data block batch audit evidence set f ═ { PiB_jJ ≦ t }, where PbB_jThe calculation process of (2) is as follows:

9.3 cloud service will audit evidence (Θ)_BR) to a three-party auditor.

9.4 third party Auditer Audit evidence (theta) returned by cloud service party_BR) into the following equation:

wherein v is_k，u_kAre public keys of the kth user;

phi's for the k-th user respectively_sA data block

Version number and timestamp of; r_kIs a random mask of the kth user in the challenge information, an

Wherein y is_kIs the public key of the kth user, a is the integer set Z_pA medium random number;

if the equation is established, the multiple copies of the file are complete; otherwise, it indicates that the data in some of the multiple copies has been corrupted.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.

Claims (6)

1. A public auditing method for multi-copy data in cloud storage service is characterized by comprising the following steps:

(1) a key generation step: a user generates a key pair, namely a private key SK is { x }, and a public key PK is { g, u, v, y }; the user saves the private key SK and issues the public key PK to the cloud service party and the third party auditor; wherein x is a set of integers Z_pIn (3), u, v are cyclic groups G of order prime p₁G is a cyclic group G whose order is a prime number p₂And y is g^x；

(2) User data preprocessing step: a user firstly generates a file identification ID for a file F to be processed; and divides file F into n data blocks, i.e. F ═ b₁，b₂，···，b_nIn which b is_i(i ═ 1, 2.. times, n) is the ith data block; simultaneously recording version information of each data block to obtain a set phi { (v)_i，t_i) I is more than or equal to 1 and less than or equal to n, wherein v_i，t_iAre respectively data block b_iVersion number and timestamp of; in addition, the user also assigns each data block b_iGenerating a corresponding digital signature σ_iSo as to obtain the digital signature set Λ ═ σ { (σ ═ σ }_iI is more than or equal to 1 and less than or equal to n; subsequently, t different copy files are generated by inserting different random masks into the data blocks, and the multiple copy set is recorded as FS ═ { F'₁,F’₂,…,F’_tOf which is F'_j(j 1, 2.. times, t) is the jth copy file; finally, the user saves the file identification ID and the version information phi by a third party auditor, sends the file identification ID, the data block signature set Lambda and the multi-copy set FS to a cloud service party, and then deletes all data except the private key;

(3) preprocessing data of a cloud server side: after receiving a multi-copy set FS, a data block signature set Lambda and a file identification ID sent by a user, a cloud service party firstly signs a sigma on each data block_iCarrying out bilinear pairing calculation to obtain a data block label omega_iI.e. omega_i＝e(σ_iG), and set of tags Ω ═ ω { ω ═ ω_iI is more than or equal to 1 and less than or equal to n, and simultaneously storing each copy in different servers;

(4) a third party auditor data preprocessing step: the third party auditor identifies the file ID and the version information phi transmitted by the user { (v)_i，t_i) I is more than or equal to 1 and less than or equal to n is stored in the dynamic hash table to realize auditable data freshness;

(5) the challenge step is as follows: responding to the user audit request or periodically auditing the data on behalf of the user by a third party auditor, first generating challenge information including randomly selected data block sequence number set psi { [ PSI ]_s1,2, …, c, random number set t ═ r_s|r_s∈Z_pS-1, 2, …, c }, and a random mask R-y^aWherein c is the number of data blocks needing to be challenged in each copy file, and a is an integer set Z_pA medium random number; subsequently, the third party auditor sends challenge information (Ψ, Τ, R) to the cloud service party;

(6) an evidence generation step: after the cloud service party receives the challenge information of the third party auditor, data-bearing evidence needs to be generated, wherein the data-bearing evidence comprises a tag evidence theta and a data block evidence set Pp ═ ρ {_jJ is more than or equal to 1 and less than or equal to t, wherein rho_jThe data block evidence of the jth copy file; subsequently returning evidence information (Θ, Ρ) to the third party auditor;

(7) and (3) evidence verification step: the third party auditor verifies the evidence information (Θ, p) returned by the cloud service party; if the verification is successful, the multiple copies of the file are complete; otherwise, it indicates that the data in some multi-copy files has been damaged;

(8) and a data dynamic updating step: when the data needs to be updated, the user needs to send update information U to a third party auditor_TPASending update information U to cloud service side_CSP(ii) a In harvestingWhen the information is updated, the third party auditor updates the dynamic hash table, and the cloud service party updates the corresponding data block and the corresponding label;

(9) batch auditing step: when w different users simultaneously initiate audit requests, the cloud service side respectively generates label evidence theta for each user_kAnd data block evidence set p_k＝{ρ_k,jJ is less than or equal to 1 and less than or equal to t, wherein k is 1, 2. Then, all the label evidences are aggregated again to obtain a label batch audit evidence theta_BAnd aggregating the data block evidences of different copy files of each user again to obtain a data block batch audit evidence set

Subsequently, the cloud service party will audit the evidence (Θ)_BR) to a three-party auditor; the third party auditor verifies the batch audit evidence; if the verification is successful, the multiple copies of the files of all the users are complete; otherwise, it indicates that the data in some of the multiple copies has been corrupted.

2. The method for publicly auditing the data of multiple copies in the cloud storage service according to claim 1, characterized in that:

the user also being for each data block b_iGenerating a corresponding digital signature σ_iThe calculation process is as follows:

where H (-) is a secure hash function whose function is to map a string to a set of integers Z_pThe above step (1);

j ═ 1,2,... t) copy files F 'in the multi-copy set FS'_j＝{m_j,1，m_j,2，…，m_j,nIn (v), m_j,iBy data block b_iDifferentiation is obtained, and the calculation process is as follows:

m_j,i＝b_i+H(v_i||t_i||j)。

3. the method for publicly auditing the data of multiple copies in the cloud storage service according to claim 1, wherein the evidence generating step includes the following processes:

(3.1) after receiving the challenge information of the third party auditor, the cloud service side firstly generates a label evidence for the multiple copies of the files, and the calculation process is as follows:

wherein the content of the first and second substances,

is a multi-copy document_sA tag of each data block;

(3.2) the cloud service side generates data block evidence rho for each copy file_jThe calculation process is as follows:

wherein e is a bilinear mapping function;

is the jth copy file_sA data block;

(3.3) the cloud service side will evidence information (Θ, p ═ ρ_jJ is more than or equal to 1 and less than or equal to t) to the third party auditor.

4. The method for publicly auditing the data of multiple copies in the cloud storage service according to claim 1, wherein the evidence verification step comprises the following processes:

the third party auditor substitutes the evidence information (Θ, p) returned by the cloud service party into the following equation for verification:

wherein the content of the first and second substances,

are respectively phi_sA data block

Version number and timestamp of; if the equation is established, the multiple copies of the file are complete; otherwise, it indicates that the data in some of the multiple copies has been corrupted.

5. The method for publicly auditing the data of multiple copies in the cloud storage service according to claim 1, wherein the step of dynamically updating the data comprises the following processes:

(5.1) data block modification: if the user needs to put the ith data block b of the file F into the file_iModified as b_i', the user is first b_i' Generation of version information (v)_i’，t_i') and then sends update information U_TPA＝(ID，modify，i，v_i’，t_i') to a third party auditor, wherein the ID is an identifier of the file F; modify represents the update operation as modified; the third party auditor receives the update information U_TPAThen, find the version information of the ith data block of the file F in the dynamic hash table, and replace it with (v)_i’，t_i') to a host; in addition, the user needs to generate a new signature for the modified data block

And t data block copies M '═ M'_j,i＝b_i’+H(v_i’||t_i' | j) |1 ≦ j ≦ t }, and then update information U is sent_CSP＝(ID，modify，i，M’，σ’_i) Giving the cloud service party, wherein the ID is the identifier of the file F; modify represents the update operation as modified; the cloud service side receives the orderNew information U_CSPAfterwards, sign σ 'to the digit'_iReprocessing to obtain a data block label omega'_i＝e(σ’_iG), then updates are made to the i-th data block tag and the multiple copies, i.e., ω is_iIs replaced by ω'_iCopy the data block m_j,iIs replaced by m'_j,i；

(5.2) data block insertion: b is inserted behind ith data block of file F according to user requirement^*The user is first b^*Generating version information (v)^*，t^*) Then sends update information U_TPA＝(ID，insert，i，v^*，t^*) Giving a third party auditor, wherein the ID is the identifier of the file F; insert stands for update operation as insert; the third party auditor receives the update information U_TPAThen, finding the position of the i-th data block version information of the file F in the dynamic hash table, and inserting the version information (v) after the position^*，t^*) (ii) a In addition, the user needs to generate a new signature for the inserted data block

And t data block copies M^*＝{m^* _j＝b^*+H(v^*||t^*J is more than or equal to 1 and less than or equal to t, and then update information U is sent_CSP＝(ID，insert，i，M^*，σ^*) Giving the cloud service party, wherein the ID is the identifier of the file F; insert stands for update operation as insert; the cloud service side receives the update information U_CSPThen, sign the digital signature σ^*The data block label omega is obtained by reprocessing^*＝e(σ^*G) will then tag ω at the ith data block_iRear insert tag omega^*And at data block copy m_j,iPost-insertion data block m^* _j；

(5.3) data block deletion: if the user needs to put the ith data block b of the file F into the file_iDeleting, the user sends the updated information U_TPAGiving (ID, delete, i) to the third party auditor, wherein ID is the identifier of file F; delete represents an update operation as delete; the third party auditor receives the updated informationU_TPAThen, finding the version information of the ith data block of the file F in the dynamic hash table, and deleting the version information; in addition, the user sends update information U_CSPGiving (ID, delete, i) to the cloud server, wherein ID is an identifier of file F; delete represents an update operation as delete; the cloud service side receives the update information U_CSPThen, tag ω will be tagged at the ith data block_iDelete, and delete b at the same time_iAll data block copies of, i.e. { m_j,i|j＝1,2,…,t}。

6. The public auditing method for multi-copy data in cloud storage service according to claim 1, where the batch auditing step includes the following steps:

(6.1) when w different users simultaneously initiate audit requests, the cloud service side respectively generates label evidence theta for each user_kAnd data block evidence set p_k＝{ρ_k,jJ is more than or equal to 1 and less than or equal to t }; wherein, the label evidence theta_kThe calculation process of (2) is as follows:

wherein the content of the first and second substances,

is the k-th user_sA tag; r is_k,sAn s-th random number that is a set of random numbers in the challenge information about the k-th user;

each element ρ in the data block evidence set_k,jThe calculation process of (2) is as follows:

wherein u is_kIs the public key of the kth user; r_kIs the random mask of the kth user in the challenge information;

is the jth psi in the jth copy file of the kth user_sA data block;

(6.2) the cloud service party aggregates all the label evidences again to obtain a label batch audit evidence theta_BThe calculation process is as follows:

and aggregating the data block evidences of different copy files of each user again to obtain a data block batch audit evidence set

Wherein

The calculation process of (2) is as follows:

(6.3) the cloud service party audits the evidence (theta) in batches_BR) to a three-party auditor;

(6.4) the third party auditor audits the batch audit evidence (theta) returned by the cloud service party_BR) into the following equation:

wherein v is_k，u_kAre public keys of the kth user;

phi's for the k-th user respectively_sA data block

Version number and timestamp of; r_kIs a random mask of the kth user in the challenge information, an

Wherein y is_kIs the public key of the kth user, a is the integer set Z_pA medium random number;

if the equation is established, the multiple copies of the file are complete; otherwise, it indicates that the data in some of the multiple copies has been corrupted.

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