CN110798478A - Data processing method and device - Google Patents

Abstract

The embodiments of the present application provide a data processing method and device. The method receives an authentication request sent by a client through TTP, and performs user authentication based on the authentication request. The data request sends the corresponding data to the CSS, and records the corresponding data according to the sent data, receives the information fed back by the CSS, sends the corresponding data to the client according to the received information, and records the corresponding data according to the sent data. User and CSS authentication, only authenticated users can operate, and only authenticated CSS can provide cloud storage services; a certain data processing process is performed between users and storage servers to further enhance the security of user data; And the behavior of CSS is recorded, which can provide evidence when there is a problem between the user and the CSS, and solve the problem of mutual framing between the user and the storage server in the traditional situation.

Description

Data processing method and device

technical field

The embodiments of the present application relate to the technical field of data storage, and in particular, to a data processing method and device.

Background technique

With the maturity of the cloud computing service model and the explosive growth of the data volume of users, more and more users will store a large amount of data on a cloud storage service (Cloud Storage Service, CSS for short). CSS solves the problem of limited user storage space and insufficient resources.

Over time and the amount of data accumulated, users have stored a lot of data on CSS. For the user, a potential risk is that the user may forget the data stored on the CSS or not sure whether the data is stored on the CSS, and the user can only view it through the list of data provided by the CSS. On the other hand, there may be errors in the user's memory, the user has not stored or has performed the delete operation but still asks the CSS to return the data. For CSS, there is no guarantee that it is trustworthy.

In this way, under the traditional system architecture, there are various situations in which the two sides falsely accuse each other. How to provide evidence and conduct arbitration for these false accusations has become an urgent problem to be solved.

SUMMARY OF THE INVENTION

Embodiments of the present application provide a data processing method and device, so as to overcome the problem of mutual false accusations between the user and the CSS under the existing system architecture.

In a first aspect, an embodiment of the present application provides a data processing method, including:

Receive the authentication request sent by the client, and perform user authentication based on the authentication request;

After the authentication is passed, if a data request sent by the client is received, corresponding data is sent to the CSS according to the data request, and corresponding records are performed according to the sent data;

Receive the information fed back by the CSS, send corresponding data to the user terminal according to the received information, and perform corresponding recording according to the sent data.

In a possible design, the data request is a data upload request, the data upload request carries upload data, and the upload data includes a data tag, complete data and a hash value, wherein the hash value is based on the The complete data is determined;

The sending corresponding data to the CSS according to the data request, and performing corresponding recording according to the sent data, including:

Splitting the complete data, and calculating the hash value of each data block after splitting;

According to the hash value in the uploaded data and the calculated hash value, determine whether the complete data is correct;

If the complete data is correct, data processing is performed according to the data mark, the processed data is sent to the CSS for storage, and corresponding recording is performed according to the sent data.

In a possible design, the receiving the information fed back by the CSS, sending corresponding data to the user terminal according to the information, and performing corresponding recording according to the sent data, including:

Receive the storage result fed back by the CSS, generate a data list according to the storage result, send the data list to the client, and record the data list accordingly.

In a possible design, the performing data processing according to the data tag, and sending the processed data to the CSS for storage, includes:

Determine whether data encryption needs to be performed according to the data mark;

If it is determined that data encryption is required, a random number corresponding to each data block after division is generated respectively;

Encrypt each data block after division according to the generated random number, and obtain ciphertext data according to the encryption result;

The obtained ciphertext data is sent to the CSS for storage.

In a possible design, the data request is a data download request, and the data download request is determined by the user terminal according to a data list, and the data list is determined by a trusted third party (Trusted Third Part, TTP for short) according to The data stored in the CSS is generated;

The receiving the information fed back by the CSS, sending corresponding data to the client according to the information, and performing corresponding recording according to the sent data, including:

receiving the data to be downloaded fed back by the CSS, where the data to be downloaded is determined by the CSS according to the data download request;

Splitting the data to be downloaded, and calculating the hash value of each data block after splitting;

According to the stored hash value corresponding to the data to be downloaded and the calculated hash value, determine whether the data to be downloaded is correct;

If the data to be downloaded is correct, data processing is performed according to the data tag corresponding to the data to be downloaded, the processed data is sent to the client, and corresponding records are performed according to the sent data.

In a possible design, performing data processing according to a data tag corresponding to the data to be downloaded, and sending the processed data to the client, includes:

Determine whether data encryption needs to be performed according to the data mark;

If it is determined that data encryption is required, obtain a random number corresponding to each data block after division;

Encrypt each divided data block according to the obtained random number, and obtain ciphertext data according to the encryption result;

Send the obtained ciphertext data to the client.

In a possible design, the data request is a data deletion request, and the data deletion request is determined by the user terminal according to a data list, and the data list is generated by TTP according to the data stored in the CSS;

The receiving the information fed back by the CSS, sending corresponding data to the client according to the information, and performing corresponding recording according to the sent data, including:

receiving a deletion certificate fed back by the CSS, the deletion certificate being generated by the CSS after deleting the data corresponding to the data deletion request;

Save the deleted certificate, feedback the successful deletion information to the user terminal, update the data list according to the deleted certificate, send the updated data list to the user terminal, and perform corresponding processing on the updated data list Record.

In a possible design, after the authentication is passed, the method further includes:

If a query request sent by the client is received, the query request is recorded, and a target data list is determined from a data list according to the query request, wherein the data list is generated by TTP according to the data stored in the CSS;

Sending the target data list to the client.

In a second aspect, an embodiment of the present application provides a data processing device, including a memory, a processor, and computer-executable instructions stored in the memory and executable on the processor, where the processor executes the computer-executed instructions Implement the following steps when instructing:

Receive the authentication request sent by the client, and perform user authentication based on the authentication request;

After the authentication is passed, if a data request sent by the client is received, corresponding data is sent to the CSS according to the data request, and corresponding records are performed according to the sent data;

Receive the information fed back by the CSS, send corresponding data to the user terminal according to the received information, and perform corresponding recording according to the sent data.

In a possible design, the data request is a data upload request, the data upload request carries upload data, and the upload data includes a data tag, complete data and a hash value, wherein the hash value is based on the The complete data is determined;

The sending corresponding data to the CSS according to the data request, and performing corresponding recording according to the sent data, including:

Splitting the complete data, and calculating the hash value of each data block after splitting;

According to the hash value in the uploaded data and the calculated hash value, determine whether the complete data is correct;

If the complete data is correct, data processing is performed according to the data mark, the processed data is sent to the CSS for storage, and corresponding recording is performed according to the sent data.

In a possible design, the receiving the information fed back by the CSS, sending corresponding data to the user terminal according to the information, and performing corresponding recording according to the sent data, including:

Receive the storage result fed back by the CSS, generate a data list according to the storage result, send the data list to the client, and record the data list accordingly.

In a possible design, the performing data processing according to the data tag, and sending the processed data to the CSS for storage, includes:

Determine whether data encryption needs to be performed according to the data mark;

If it is determined that data encryption is required, a random number corresponding to each data block after division is generated respectively;

Encrypt each data block after division according to the generated random number, and obtain ciphertext data according to the encryption result;

The obtained ciphertext data is sent to the CSS for storage.

In a possible design, the data request is a data download request, and the data download request is determined by the user terminal according to a data list, and the data list is generated by TTP according to the data stored in the CSS;

The receiving the information fed back by the CSS, sending corresponding data to the client according to the information, and performing corresponding recording according to the sent data, including:

receiving the data to be downloaded fed back by the CSS, where the data to be downloaded is determined by the CSS according to the data download request;

Splitting the data to be downloaded, and calculating the hash value of each data block after splitting;

According to the stored hash value corresponding to the data to be downloaded and the calculated hash value, determine whether the data to be downloaded is correct;

If the data to be downloaded is correct, data processing is performed according to the data tag corresponding to the data to be downloaded, the processed data is sent to the client, and corresponding records are performed according to the sent data.

In a possible design, performing data processing according to a data tag corresponding to the data to be downloaded, and sending the processed data to the client, includes:

Determine whether data encryption needs to be performed according to the data mark;

If it is determined that data encryption is required, obtain a random number corresponding to each data block after division;

Encrypt each divided data block according to the obtained random number, and obtain ciphertext data according to the encryption result;

Send the obtained ciphertext data to the client.

In a possible design, the data request is a data deletion request, and the data deletion request is determined by the user terminal according to a data list, and the data list is generated by TTP according to the data stored in the CSS;

The receiving the information fed back by the CSS, sending corresponding data to the client according to the information, and performing corresponding recording according to the sent data, including:

receiving a deletion certificate fed back by the CSS, the deletion certificate being generated by the CSS after deleting the data corresponding to the data deletion request;

Save the deleted certificate, feedback the successful deletion information to the user terminal, update the data list according to the deleted certificate, send the updated data list to the user terminal, and perform corresponding processing on the updated data list Record.

In a possible design, after the authentication is passed, the method further includes:

If a query request sent by the client is received, the query request is recorded, and a target data list is determined from a data list according to the query request, wherein the data list is generated by TTP according to the data stored in the CSS;

Sending the target data list to the client.

In a third aspect, embodiments of the present application provide a computer-readable storage medium, where computer-executable instructions are stored in the computer-readable storage medium, and when a processor executes the computer-executable instructions, the first aspect and the first Aspects various possible designs of the data processing method described.

According to the data processing method and device provided by the embodiments of the present application, the method receives an authentication request sent by the client through TTP, and performs user authentication based on the authentication request. The data request sends the corresponding data to the CSS, and records the corresponding data according to the sent data, receives the information fed back by the CSS, sends the corresponding data to the client according to the received information, and records the corresponding data according to the sent data. And CSS authentication, only authenticated users can operate, and only authenticated CSS can provide cloud storage services; a certain data processing process is performed between users and storage servers to further enhance the security of user data; The behavior of CSS is recorded, which can provide evidence when there is a problem between the user and the CSS, and solve the problem of mutual framing between the user and the storage server in the traditional situation.

Description of drawings

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the accompanying drawings used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description These are some embodiments of the present application, and for those of ordinary skill in the art, other drawings can also be obtained from these drawings without any creative effort.

1 is a schematic diagram of the architecture of a data processing system provided by an embodiment of the present application;

FIG. 2 is a schematic structural diagram of a user terminal according to an embodiment of the present application;

3 is a schematic structural diagram of a TTP provided by an embodiment of the present application;

FIG. 4 is a schematic structural diagram of a CSS provided by an embodiment of the present application;

5 is a schematic flowchart of a data processing method provided by an embodiment of the present application;

6 is a schematic flowchart of another data processing method provided by an embodiment of the present application;

FIG. 7 is a schematic structural diagram of a data processing device according to an embodiment of the present application;

FIG. 8 is a schematic diagram of a hardware structure of a data processing device according to an embodiment of the present application.

Detailed ways

In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments It is a part of the embodiments of the present application, but not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

Existing users already store a lot of data on CSS. For the user, a potential risk is that the user may forget the data stored on the CSS or not sure whether the data is stored on the CSS, and the user can only view it through the list of data provided by the CSS. On the other hand, there may be errors in the user's memory, the user has not stored or has performed the delete operation but still asks the CSS to return the data. For CSS, there is no guarantee that it is trustworthy. In this way, under the traditional system architecture, there are various situations in which the two sides falsely accuse each other.

Therefore, in consideration of the above problems, this application provides a data processing method, which introduces TTP to complete the authentication of users and CSS. Only authenticated users can operate, and only authenticated CSSs can provide cloud storage services; A certain data processing process is carried out between the servers to further enhance the security of user data; the behavior of users and CSS can be recorded, which can provide evidence when problems occur between users and CSS, and solve the traditional problem between users and storage servers. the question of mutual framing.

A data processing method provided by the present application can be applied to the schematic diagram of the data processing system architecture shown in FIG. 1 . As shown in FIG. 1 , it includes: a user terminal 101 , a TTP 102 and a CSS 103 , and the TTP 102 can receive the authentication sent by the user terminal 101 . Request, perform user authentication based on the authentication request, and after the authentication is passed, if a data request sent by the client 101 is received, the corresponding data will be sent to CSS103 according to the data request, and corresponding records will be made according to the sent data, and CSS103 can be received. For the feedback information, corresponding data is sent to the user terminal 101 according to the received information, and corresponding recording is performed according to the sent data.

Here, the user side: the data owner, the actual user of CSS. Clients can use CSS services to upload, view, download, update, delete and manage their own data. As shown in Figure 2, it includes data segmentation and reorganization module, random number module, data encryption and decryption module, integrity verification module, etc. Specifically:

Data segmentation and reorganization module: During the data upload process, according to the block size, the plaintext data can be divided into blocks, the original data is divided into N blocks of equal size, and the blocks with insufficient size are filled with 0. During the data download process, the data after decryption of each block is reorganized to restore the complete data.

Random number module: can generate random numbers equal to the block size for use in the encryption process.

Data encryption and decryption module: It can perform corresponding operations on file blocks and random numbers, such as bit XOR operation, to generate ciphertext data.

Integrity verification module: For plaintext or ciphertext data, the corresponding algorithm, such as hash algorithm, can be used to calculate the message digest, and the message digest value can be used as the data integrity proof.

TTP: A third-party system trusted by both the client and CSS. It is an authoritative organization with a higher security level. It can complete the authentication of users and CSS, complete the intermediate processing of user data, and complete the audit and arbitration of users and CSS. As shown in Figure 3, it includes an authentication module, a storage module, a verification module, a data segmentation and reorganization module, a random number generation module, an encryption and decryption module, a data list module, and an audit module. specific:

Authentication module: It can authenticate the request from the user, and after the authentication is passed, it can provide services for the user. If the authentication fails, the service is refused. On the other hand, the access CSS is also authenticated, and those that pass the authentication are allowed to provide CSS services to the outside world.

Storage module: In the process of data upload, it can temporarily store the files uploaded by the receiving users, and store the metadata information of the files, random numbers, integrity certificates, audit information, etc. During the data download process, the data returned by CSS is temporarily stored, and the decrypted data is stored.

Verification module: The corresponding algorithm, such as hash algorithm, can be used to generate data integrity proof, verify whether the received file is complete, and request file retransmission if it is incomplete.

Data segmentation and reorganization module: During the data upload process, according to the block size, the plaintext data can be divided into blocks, the original data is divided into N blocks of equal size, and the blocks with insufficient size are filled with 0. During the data download process, the data after decryption of each block is reorganized to restore the complete data.

Random number generation module: can generate random numbers equal to the block size for the encryption process.

Encryption and decryption module: can perform encryption operations on the data uploaded by the user during the data uploading process. During the data download process, decrypt the ciphertext data from CSS.

Data List Module: A data list about user data can be maintained. It's a trusted list that users can query to get their own list of files on CSS, even if it's old.

Audit module: It can record user operations and CSS operations to form audit logs.

CSS: Distributed storage can be done for files uploaded by TTP, such as hadoop hdfs, openstackswift, ceph FS, etc. As shown in Figure 4, usually it contains a storage control center and multiple data storage servers. The storage control center manages data block mapping, it receives data upload and download requests from TTP, and schedules access to the storage server according to a certain scheduling algorithm. During the uploading process, the received data is scheduled to different storage servers for storage, multiple copies are stored on different servers, and the scheduling results are recorded in the database. During the download process, query the database to obtain the storage location of the file, and then schedule the storage server to return the corresponding file.

It should be understood that the above system is only an exemplary system, and can be set according to application requirements during specific implementation.

The technical solutions of the present application and how the technical solutions of the present application solve the above-mentioned technical problems will be described in detail below with specific examples. The following specific embodiments may be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments. The embodiments of the present application will be described below with reference to the accompanying drawings.

FIG. 5 is a schematic flowchart of a data processing method provided by an embodiment of the present application. The execution body of the embodiment of the present application may be the TTP in the embodiment shown in FIG. 1 . As shown in Figure 5, the method may include:

S501: Receive an authentication request sent by a client, and perform user authentication based on the authentication request.

Here, the client sends an authentication request to TTP. TTP can audit the authentication behavior of the client and write it into the audit module. TTP can also authenticate the user and return the authentication result. If authentication fails, deny service. If the authentication passes, continue with the next steps.

S502: After the authentication is passed, if a data request sent by the client is received, corresponding data is sent to the CSS according to the data request, and corresponding recording is performed according to the sent data.

S503: Receive the information fed back by the CSS, send corresponding data to the user terminal according to the received information, and perform corresponding recording according to the sent data.

Optionally, the data request is a data upload request, the data upload request carries upload data, and the upload data includes a data tag, complete data and a hash value, wherein the hash value is determined according to the complete data .

Here, data upload refers to the process that the client stores local data to CSS through TTP.

Specifically, the user terminal selects the file to be uploaded, which is marked as M. Further, the user terminal can determine the privacy level of the file, and determine whether the file needs to be encrypted according to the privacy level.

Set the data flag to 1 if encryption is required. This tag value will be uploaded when the file is uploaded, and TTP will process the file differently according to different tag values. The data segmentation and reorganization module can be used to cut the file into N blocks of fixed size, and fill with 0 when the length of the Nth block is insufficient. The block number starts from 1, and the block data of the file is recorded as (B1_1, B1_2, B1_3...B1_N). Use the random number module to generate a random number R1 equal to the block size. The data encryption and decryption module uses R1 to perform XOR operation with the corresponding blocks (B1_1, B1_2, B1_3...B1_N) of the file, and the result is recorded as (C1_1, C1_2, C1_3....C1_N) ), etc., where C1_i=B_i⊕R1, C1 represents the first encryption, i represents the block number, and ⊕ represents the XOR operation. The integrity verification module calculates the hash value of the above ciphertext (H1_1, H1_2, H1_3...H1_N), H1_i=hash(C1_i), H1 represents the first hash, hash represents the hash algorithm, and i represents the block 's serial number. The client can reorganize (C1_1, C1_2, C1_3.......C1_N) to form a complete file C2. After the TTP receives the file, the file can be divided into corresponding blocks using a segmentation algorithm. The user terminal can also reorganize (H1_1, H1_2, H1_3....H1_N) to form a complete file H2. The client uploads [1, C2, H2] to TTP, that is, the client uploads the data mark, complete data and hash value to TTP. The client can locally store R1 and the hash value of the file H2.

If encryption is not required, set the data flag to 0, and no encryption will be performed during uploading. The data segmentation and reorganization module can be used to cut the file into N blocks of fixed size, and fill with 0 when the length of the Nth block is insufficient. The block number starts from 1, and the block data of the file is recorded as (B1_1, B1_2, B1_3...B1_N). The integrity verification module calculates the hash value of each block (H1_1, H1_2, H1_3...H1_N), H1_i=hash(B1_i), hash represents the hash algorithm, and i represents the serial number of the block. The client can reorganize (H1_1, H1_2, H1_3.......H1_N) to form a complete file H2. The client uploads [0, M, H2] to TTP. That is, the client uploads the data tag, complete data, and hash value to TTP. The client can locally store the block number and the corresponding hash value H2, [0, H2].

Optionally, the sending corresponding data to the CSS according to the data request, and performing corresponding recording according to the sent data, including:

Splitting the complete data, and calculating the hash value of each data block after splitting;

According to the hash value in the uploaded data and the calculated hash value, determine whether the complete data is correct;

If the complete data is correct, data processing is performed according to the data mark, the processed data is sent to the CSS for storage, and corresponding recording is performed according to the sent data.

Optionally, the performing data processing according to the data mark, and sending the processed data to the CSS for storage, includes:

Determine whether data encryption needs to be performed according to the data mark;

If it is determined that data encryption is required, a random number corresponding to each data block after division is generated respectively;

Encrypt each data block after division according to the generated random number, and obtain ciphertext data according to the encryption result;

The obtained ciphertext data is sent to the CSS for storage.

Specifically, TTP records the uploading behavior of the client in the audit module. TTP can store the data uploaded by the client. TTP can temporarily store the received data locally. Here, the received data can be represented in the form of a list, which is divided into three parts. The first part of the data flag, indicating whether the data is encrypted. The second part represents the complete data (plaintext or ciphertext data). The third part represents the reorganization result of the second part of the N block hash values.

After the TTP reception is completed, the data segmentation and reorganization module can be used to re-segment the file. The segmentation algorithm here is the same as the previous one. The result of this segmentation is recorded as (B2_1, B2_2, B2_3...B2_N), and Temporarily store these chunks. Use the verification module to calculate the hash value (H3_1, H3_2, H3_3...H3_N) for these blocks (B2_1, B2_2, B2_3...B2_N) in turn, H3_i=hash(B2_i), hash represents hash Algorithm, i represents the sequence number of the block. The received H2 is segmented by the data segmentation and reorganization module, and the result is recorded as (H2_1, H2_2, H2_3...H2_N). Compare (H3_1,H3_2,H3_3...H3_N) with (H2_1,H2_2,H2_3...H2_N). If the two results are consistent, the data is correct, and you can continue with the following steps. If the two are inconsistent, the data is damaged, and the client is required to re-upload the complete data or a certain block of data. Here, it is easy to know which block has incomplete data through the hash value of the block.

TTP performs data processing on the received data. Determine whether the data needs to be encrypted according to the received data tag. 1 means encrypted, 0 means no encryption.

If encryption is required, TTP generates a random number R2 equal to the block size. Use R2 to perform the XOR operation with the corresponding blocks (B2_1, B2_2, B2_3...B2_N) of the file respectively, here the result is recorded as (C2_1, C2_2, C2_3....C2_N), etc., here C2_i=B2_i⊕R2, i represents the block number, and ⊕ represents the XOR operation. Further, TTP can calculate the hash value of the ciphertext (H2_1, H2_2, H2_3...H2_N), H2_i=hash(C2_i), hash represents the hash algorithm, and i represents the serial number of the block. TTP will reorganize (C2_1, C2_2, C2_3....C2_N) to form a complete file C3, and then upload the file to CSS. TTP reorganizes (H2_1, H2_2, H2_3...H2_N) to form a document integrity proof H3. TTP can locally store R2, data tag and corresponding hash value H3, [R2,1,H3].

If encryption is not required, TTP can upload the received plaintext data M to the CSS. TTP locally stores data tags and file integrity proofs H3, [0, H3].

TTP can record the uploading behavior of CSS into the audit module. CSS receives the data uploaded by TTP and stores it in a distributed manner.

Optionally, the receiving the information fed back by the CSS, sending corresponding data to the user terminal according to the information, and performing corresponding recording according to the sent data, including:

Receive the storage result fed back by the CSS, generate a data list according to the storage result, send the data list to the client, and record the data list accordingly.

Here, after receiving the data uploaded by TTP and storing it in a distributed manner, CSS returns a successful response to TTP storage. TTP generates a data list, such as user name, file name, file type, data tag, modification time, file size, file integrity certificate, etc., sends the generated data list to the client, and records the generated data list accordingly.

Optionally, the data request is a data download request, and the data download request is determined by the user terminal according to a data list, and the data list is generated by the TTP according to the data stored in the CSS.

Here, the data download refers to a process in which the client requests TTP to download data, the TTP downloads the data for processing, and returns the result to the client.

Specifically, TTP can provide a data list to the client. The client can select the data to be downloaded through the data list, and send a data download request to the TTP. The TTP receives the download request and writes the download request information into the audit module. Further, the TTP can forward the download request to the CSS.

Optionally, the receiving the information fed back by the CSS, sending corresponding data to the user terminal according to the information, and performing corresponding recording according to the sent data, including:

receiving the data to be downloaded fed back by the CSS, where the data to be downloaded is determined by the CSS according to the data download request;

Splitting the data to be downloaded, and calculating the hash value of each data block after splitting;

According to the stored hash value corresponding to the data to be downloaded and the calculated hash value, determine whether the data to be downloaded is correct;

If the data to be downloaded is correct, data processing is performed according to the data tag corresponding to the data to be downloaded, the processed data is sent to the client, and corresponding records are performed according to the sent data.

Optionally, performing data processing according to the data tag corresponding to the data to be downloaded, and sending the processed data to the client, includes:

Determine whether data encryption needs to be performed according to the data mark;

If it is determined that data encryption is required, obtain a random number corresponding to each data block after division;

Encrypt each divided data block according to the obtained random number, and obtain ciphertext data according to the encryption result;

Send the obtained ciphertext data to the client.

Here, CSS receives the request forwarded by TTP. CSS returns the corresponding request data to TTP. TTP can buffer the received data, which is recorded as M3. TTP queries stored information to determine data tags. After receiving, TTP re-segments the file M3 by using the data segmentation and reorganization module, records the result of this segmentation as (B3_1, B3_2, B3_3...B3_N), and temporarily stores these segments. TTP uses the verification module to sequentially calculate the hash values (H4_1, H4_2, H4_3...H4_N) for these blocks (B3_1, B3_2, B3_3...B3_N), H4_i=hash(B3_i), hash represents Hash algorithm, i represents the sequence number of the block. TTP splits the hash value of the data that has been stored. Get (H5_1, H5_2, H5_3...H5_N). TTP compares (H4_1, H4_2, H4_3...H4_N) with (H5_1, H5_2, H5_3...H5_N). If the two results are consistent, the data is correct, and you can continue with the following steps. If the two are inconsistent, TTP requires CSS to return the data again.

TTP processes the data according to the data tag and returns the data to the client.

If encryption is required, TTP obtains the random number corresponding to the encryption, which is denoted as R3 here. TTP uses random number R3 to perform XOR operation with data blocks (B3_1, B3_2, B3_3... TTP reorganizes (C3_1, C3_2, C3_3....C3_N) to obtain file C4. TTP can return the data tag and C4 to the client, [1, C4]. TTP can also record accordingly according to the data sent.

If encryption is not required, TTP directly sends the verified data M3 and data mark to the user, [0, M3]. TTP can also record accordingly according to the data sent.

The client receives the data returned by TTP and stores it. The client uses the data segmentation and reorganization module to re-segment the received data, records the result of this segmentation as (B4_1, B4_2, B4_3...B4_N), and stores these segments. The client uses the integrity verification module to sequentially calculate the hash values (H6_1, H6_2, H6_3...H6_N) for these blocks (B4_1, B4_2, B4_3...B4_N), H6_i=hash(B4_i) , hash represents the hash algorithm, and i represents the serial number of the block. The client splits the stored hash value. Get (H7_1,H7_2,H7_3...H7_N). The client compares H7_1, H7_2, H7_3...H7_N) with (H6_1, H6_2, H6_3...H6_N). If the results are the same, continue with the following steps. If the two are inconsistent, the client requests TTP to return the data again. The user terminal processes the data according to the received data mark and restores the original data.

If encrypted, the user terminal queries the random number corresponding to the encryption, which is recorded as R4 here. The client uses random number R4 and data blocks (B4_1, B4_2, B4_3...B4_N) to perform XOR operation in turn, decrypts the original data corresponding to each block, and obtains (C4_1, C4_2, C4_3... ....C4_N). The client will reorganize (C4_1, C4_2, C4_3......C4_N) to get the original data.

If not encrypted, the client can directly obtain the original data from the data returned by TTP.

Optionally, after the authentication is passed, it also includes:

If a query request sent by the client is received, the query request is recorded, and a target data list is determined from a data list according to the query request, wherein the data list is generated by TTP according to the data stored in the CSS;

Sending the target data list to the client.

Here, the data query refers to a process in which the client requests the TTP to return a list of data that meets the conditions. Specifically, the client sends a query request to the TTP. TTP receives the request and writes the query request information into the audit module. TTP performs a query to obtain a list of data that meets the query conditions. TTP returns a list of data that meets the query conditions to the client.

Optionally, the data request is a data deletion request, and the data deletion request is determined by the user terminal according to a data list, and the data list is generated by the TTP according to the data stored in the CSS.

Here, data deletion refers to the process from the client requesting the TTP to delete the data to the CSS completely deleting the data.

Specifically, TTP can provide a data list to the client. The client selects the file to be deleted through the data list and sends a data deletion request. TTP receives the delete request and writes the delete behavior into the audit module. TTP sends the above delete request to CSS.

Optionally, receiving the information fed back by the CSS, sending corresponding data to the user terminal according to the information, and performing corresponding recording according to the sent data, including:

receiving a deletion certificate fed back by the CSS, the deletion certificate being generated by the CSS after deleting the data corresponding to the data deletion request;

Save the deleted certificate, feedback the successful deletion information to the user terminal, update the data list according to the deleted certificate, send the updated data list to the user terminal, and perform corresponding processing on the updated data list Record.

Here, CSS receives the TTP request and deletes the corresponding data. CSS sends TTP a proof of deletion. The TTP saves the proof of deletion. TTP writes CSS actions and results into the audit module. TTP sends a message that the deletion is successful to the client. TTP deletes records in the data list and updates the data list. TTP provides the updated list of data to the client.

It can be seen from the above description that the embodiment of the present application introduces TTP to authenticate users and CSSs. Only authenticated users can operate, and only authenticated CSSs can provide cloud storage services; TTP performs certain operations between users and storage servers. The data processing process further enhances the security of user data; TTP records and audits the behavior of users and CSS, and provides evidence when problems occur between users and CSS; TTP acts as an arbiter between users and storage servers, Validate the data in the process, sanction the sabotage of the server, and solve the problem of mutual framing between the user and the storage server in the traditional situation.

Customize the security level (encrypted and unencrypted) for the data, and the two levels correspond to different processing procedures.

The block operation of data solves the problem of slow reading and writing of large files. In addition, the data is divided into blocks, and then the calculation is performed on the blocks to effectively improve the calculation efficiency.

The encryption operation of the data is carried out by using a simple XOR operation, which can meet the confidentiality requirements of the data, reduce the amount of calculation, and improve the calculation speed.

The decryption operation of the data can be realized by a simple XOR operation, the calculation amount is small, and the operation speed is fast;

The number of XOR operations can be extended, and security can be improved by adjusting the number of times and the block size.

TTP provides a user list to solve the situation that users forget for a long time.

TTP requires CSS to provide proof of file existence and proof of file deletion, effectively preventing CSS from maliciously deleting user files.

CSS uses sharding and multiple copies to store data in different segments in a distributed manner to prevent data from being unrecoverable after one or several servers fail.

FIG. 6 is a schematic flowchart of another data processing method provided by an embodiment of the present application, and the execution body of the embodiment of the present application may be the TTP in the embodiment shown in FIG. 1 . As shown in Figure 6, the method includes:

S601: Receive an authentication request sent by a client, and perform user authentication based on the authentication request.

S602: After the authentication is passed, if a data upload request sent by the client is received, the data upload request carries the upload data, and the upload data includes a data tag, complete data and a hash value, wherein the above-mentioned hash value is based on the above-mentioned complete data. If determined, the above complete data is divided, and the hash value of each data block after the division is calculated.

S603: Determine whether the above-mentioned complete data is correct according to the hash value in the above-mentioned uploaded data and the calculated hash value.

S604: If the above-mentioned complete data is correct, perform data processing according to the above-mentioned data mark, send the processed data to the CSS for storage, and perform corresponding recording according to the sent data.

S605: Receive the storage result fed back by the CSS, generate a data list according to the storage result, send the data list to the client, and record the above data list accordingly.

S606: After the authentication is passed, if a data download request sent by the client is received, the data download request is determined by the client according to the data list, and the data list is generated by the TTP according to the data stored in the CSS, and the corresponding data download request is sent according to the above-mentioned data download request. data to CSS and recorded accordingly according to the data sent.

S607: Receive the data to be downloaded fed back by the CSS, the data to be downloaded is determined by the CSS according to the data download request, the data to be downloaded is divided, and the hash value of each data block after the division is calculated.

S608: According to the stored hash value corresponding to the data to be downloaded and the calculated hash value, determine whether the data to be downloaded is correct;

S609: If the data to be downloaded is correct, perform data processing according to the data tag corresponding to the data to be downloaded, send the processed data to the client, and perform corresponding recording according to the sent data.

S610: After the authentication is passed, if a data deletion request sent by the client is received, the data deletion request is determined by the client according to the data list, and the data list is generated by the TTP according to the data stored in the CSS, and the corresponding data deletion request is sent according to the above data deletion request. data to CSS and recorded accordingly according to the data sent.

S611: Receive the deletion certificate fed back by the CSS, where the deletion certificate is generated by the CSS after deleting the data corresponding to the above data deletion request, save the deletion certificate, feed back the successful deletion information to the user, and update the data according to the deletion certificate list, send the updated data list to the client, and record the updated data list accordingly.

S612: After the authentication is passed, if the query request sent by the client is received, the query request is recorded, and the target data list is determined from the data list according to the query request, wherein the data list is generated by the TTP according to the data stored in the CSS.

S613: Send the above target data list to the client.

In the data processing method provided by the embodiment of this application, TTP is introduced to complete the authentication of users and CSSs. Only authenticated users can operate, and only authenticated CSSs can provide cloud storage services; The data processing process further enhances the security of user data; recording the behavior of users and CSS can provide evidence when problems occur between users and CSS, and solve the traditional problem of mutual framing between users and storage servers.

Corresponding to the data processing method of the above embodiment, FIG. 7 is a schematic structural diagram of a data processing device provided by an embodiment of the present application. For the convenience of description, only the parts related to the embodiments of the present application are shown. FIG. 7 is a schematic structural diagram of a data processing device according to an embodiment of the present application. As shown in FIG. 7 , the data processing device 70 includes: a receiving module 701 , a first processing module 702 and a second processing module 703 .

The receiving module 701 is configured to receive an authentication request sent by a user terminal, and perform user authentication based on the authentication request.

The first processing module 702 is configured to send corresponding data to the CSS according to the data request after receiving the data request sent by the user terminal after passing the authentication, and perform corresponding recording according to the sent data.

The second processing module 703 is configured to receive the information fed back by the CSS, send corresponding data to the user terminal according to the received information, and perform corresponding recording according to the sent data.

In a possible design, the data request is a data upload request, the data upload request carries upload data, and the upload data includes a data tag, complete data and a hash value, wherein the hash value is based on the The complete data is determined.

The first processing module 702 sends corresponding data to the CSS according to the data request, and performs corresponding recording according to the sent data, including:

Splitting the complete data, and calculating the hash value of each data block after splitting;

According to the hash value in the uploaded data and the calculated hash value, determine whether the complete data is correct;

If the complete data is correct, data processing is performed according to the data mark, the processed data is sent to the CSS for storage, and corresponding recording is performed according to the sent data.

In a possible design, the second processing module 703 receives the information fed back by the CSS, sends corresponding data to the client according to the information, and performs corresponding recording according to the sent data, including:

Receive the storage result fed back by the CSS, generate a data list according to the storage result, send the data list to the client, and record the data list accordingly.

In a possible design, the first processing module 702 performs data processing according to the data tag, and sends the processed data to the CSS for storage, including:

Determine whether data encryption needs to be performed according to the data mark;

If it is determined that data encryption is required, a random number corresponding to each data block after division is generated respectively;

Encrypt each data block after division according to the generated random number, and obtain ciphertext data according to the encryption result;

The obtained ciphertext data is sent to the CSS for storage.

In a possible design, the data request is a data download request, and the data download request is determined by the user terminal according to a data list, and the data list is generated by the TTP according to the data stored in the CSS.

The second processing module 703 receives the information fed back by the CSS, sends corresponding data to the client according to the information, and performs corresponding records according to the sent data, including:

receiving the data to be downloaded fed back by the CSS, where the data to be downloaded is determined by the CSS according to the data download request;

Splitting the data to be downloaded, and calculating the hash value of each data block after splitting;

According to the stored hash value corresponding to the data to be downloaded and the calculated hash value, determine whether the data to be downloaded is correct;

If the data to be downloaded is correct, data processing is performed according to the data tag corresponding to the data to be downloaded, the processed data is sent to the client, and corresponding records are performed according to the sent data.

In a possible design, the second processing module 703 performs data processing according to the data tag corresponding to the data to be downloaded, and sends the processed data to the client, including:

Determine whether data encryption needs to be performed according to the data mark;

If it is determined that data encryption is required, obtain a random number corresponding to each data block after division;

Encrypt each divided data block according to the obtained random number, and obtain ciphertext data according to the encryption result;

Send the obtained ciphertext data to the client.

In a possible design, the data request is a data deletion request, and the data deletion request is determined by the user terminal according to a data list, and the data list is generated by the TTP according to the data stored in the CSS.

The second processing module 703 receives the information fed back by the CSS, sends corresponding data to the client according to the information, and performs corresponding records according to the sent data, including:

receiving a deletion certificate fed back by the CSS, the deletion certificate being generated by the CSS after deleting the data corresponding to the data deletion request;

Save the deleted certificate, feedback the successful deletion information to the user terminal, update the data list according to the deleted certificate, send the updated data list to the user terminal, and perform corresponding processing on the updated data list Record.

In a possible design, after passing the authentication, the first processing module 702 is further configured to:

If a query request sent by the client is received, the query request is recorded, and a target data list is determined from a data list according to the query request, wherein the data list is generated by TTP according to the data stored in the CSS;

Sending the target data list to the client.

The devices provided in the embodiments of the present application can be used to implement the technical solutions of the foregoing method embodiments, and the implementation principles and technical effects thereof are similar, and details are not described herein again in the embodiments of the present application.

FIG. 8 is a schematic diagram of a hardware structure of a data processing device according to an embodiment of the present invention. As shown in FIG. 8 , the data processing device 80 in this embodiment includes: a processor 801 and a memory 802; wherein

a memory 802 for storing computer-executed instructions;

The processor 801 is configured to execute computer-executed instructions stored in the memory to implement the following steps:

Receive the authentication request sent by the client, and perform user authentication based on the authentication request;

After the authentication is passed, if a data request sent by the client is received, corresponding data is sent to the CSS according to the data request, and corresponding records are performed according to the sent data;

Receive the information fed back by the CSS, send corresponding data to the user terminal according to the received information, and perform corresponding recording according to the sent data.

In a possible design, the data request is a data upload request, the data upload request carries upload data, and the upload data includes a data tag, complete data and a hash value, wherein the hash value is based on the The complete data is determined;

The sending corresponding data to the CSS according to the data request, and performing corresponding recording according to the sent data, including:

The complete data is divided, and the hash value of each data block after the division is calculated;

According to the hash value in the uploaded data and the calculated hash value, determine whether the complete data is correct;

If the complete data is correct, data processing is performed according to the data mark, the processed data is sent to the CSS for storage, and corresponding recording is performed according to the sent data.

In a possible design, the receiving the information fed back by the CSS, sending corresponding data to the user terminal according to the information, and performing corresponding recording according to the sent data, including:

Receive the storage result fed back by the CSS, generate a data list according to the storage result, send the data list to the client, and record the data list accordingly.

In a possible design, the performing data processing according to the data tag, and sending the processed data to the CSS for storage, includes:

Determine whether data encryption needs to be performed according to the data mark;

If it is determined that data encryption is required, a random number corresponding to each data block after division is generated respectively;

Encrypt each data block after division according to the generated random number, and obtain ciphertext data according to the encryption result;

The obtained ciphertext data is sent to the CSS for storage.

In a possible design, the data request is a data download request, and the data download request is determined by the user terminal according to a data list, and the data list is generated by TTP according to the data stored in the CSS;

The receiving the information fed back by the CSS, sending corresponding data to the client according to the information, and performing corresponding recording according to the sent data, including:

receiving the data to be downloaded fed back by the CSS, where the data to be downloaded is determined by the CSS according to the data download request;

Splitting the data to be downloaded, and calculating the hash value of each data block after splitting;

According to the stored hash value corresponding to the data to be downloaded and the calculated hash value, determine whether the data to be downloaded is correct;

If the data to be downloaded is correct, data processing is performed according to the data tag corresponding to the data to be downloaded, the processed data is sent to the client, and corresponding records are performed according to the sent data.

In a possible design, performing data processing according to a data tag corresponding to the data to be downloaded, and sending the processed data to the client, includes:

Determine whether data encryption needs to be performed according to the data mark;

If it is determined that data encryption is required, obtain a random number corresponding to each data block after division;

Encrypt each divided data block according to the obtained random number, and obtain ciphertext data according to the encryption result;

Send the obtained ciphertext data to the client.

In a possible design, the data request is a data deletion request, and the data deletion request is determined by the user terminal according to a data list, and the data list is generated by TTP according to the data stored in the CSS;

The receiving the information fed back by the CSS, sending corresponding data to the client according to the information, and performing corresponding recording according to the sent data, including:

receiving a deletion certificate fed back by the CSS, the deletion certificate being generated by the CSS after deleting the data corresponding to the data deletion request;

Save the deleted certificate, feedback the successful deletion information to the user terminal, update the data list according to the deleted certificate, send the updated data list to the user terminal, and perform corresponding processing on the updated data list Record.

In a possible design, after the authentication is passed, the method further includes:

If a query request sent by the client is received, the query request is recorded, and a target data list is determined from a data list according to the query request, wherein the data list is generated by TTP according to the data stored in the CSS; Sending the target data list to the client.

Optionally, the memory 802 may be independent or integrated with the processor 801 .

When the memory 802 is set independently, the data processing device further includes a bus 803 for connecting the memory 802 and the processor 801 .

An embodiment of the present invention provides a computer-readable storage medium, where computer-executable instructions are stored in the computer-readable storage medium, and when a processor executes the computer-executable instructions, the above-described data processing method is implemented.

In the several embodiments provided by the present invention, it should be understood that the disclosed apparatus and method may be implemented in other manners. For example, the device embodiments described above are only illustrative. For example, the division of the modules is only a logical function division. In actual implementation, there may be other division methods. For example, multiple modules may be combined or integrated. to another system, or some features can be ignored, or not implemented. On the other hand, the shown or discussed mutual coupling or direct coupling or communication connection may be through some interfaces, indirect coupling or communication connection of devices or modules, and may be in electrical, mechanical or other forms.

The modules described as separate components may or may not be physically separated, and components shown as modules may or may not be physical units, that is, may be located in one place, or may be distributed to multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution in this embodiment.

In addition, each functional module in each embodiment of the present invention may be integrated into one processing unit, or each module may exist physically alone, or two or more modules may be integrated into one unit. The units formed by the above modules can be implemented in the form of hardware, or can be implemented in the form of hardware plus software functional units.

The above-mentioned integrated modules implemented in the form of software functional modules may be stored in a computer-readable storage medium. The above-mentioned software function modules are stored in a storage medium, and include several instructions to enable a computer device (which may be a personal computer, a server, or a network device, etc.) or a processor (English: processor) to execute the various embodiments of the present application. part of the method.

It should be understood that the above-mentioned processor may be a central processing unit (Central Processing Unit, CPU for short), or other general-purpose processors, digital signal processors (Digital Signal Processor, DSP for short), application specific integrated circuit (Application Specific Integrated Circuit, Referred to as ASIC) and so on. A general purpose processor may be a microprocessor or the processor may be any conventional processor or the like. The steps of the method disclosed in conjunction with the invention can be directly embodied as executed by a hardware processor, or executed by a combination of hardware and software modules in the processor.

The memory may include high-speed RAM memory, and may also include non-volatile storage NVM, such as at least one magnetic disk memory, and may also be a U disk, a removable hard disk, a read-only memory, a magnetic disk or an optical disk, and the like. The bus may be an Industry Standard Architecture (ISA for short) bus, a Peripheral Component Interconnect (PCI for short) bus or an Extended Industry Standard Architecture (EISA for short) bus, or the like. The bus can be divided into address bus, data bus, control bus and so on. For convenience of representation, the buses in the drawings of the present application are not limited to only one bus or one type of bus.

The above-mentioned storage medium may be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as static random access memory (SRAM), electrically erasable programmable read only memory (EEPROM), erasable Except programmable read only memory (EPROM), programmable read only memory (PROM), read only memory (ROM), magnetic memory, flash memory, magnetic disk or optical disk. A storage medium can be any available medium that can be accessed by a general purpose or special purpose computer.

An exemplary storage medium is coupled to the processor, such that the processor can read information from, and write information to, the storage medium. Of course, the storage medium can also be an integral part of the processor. The processor and the storage medium may be located in application specific integrated circuits (Application Specific Integrated Circuits, ASIC for short). Of course, the processor and the storage medium may also exist in the electronic device or the host device as discrete components.

Those of ordinary skill in the art can understand that all or part of the steps of implementing the above method embodiments may be completed by program instructions related to hardware. The aforementioned program can be stored in a computer-readable storage medium. When the program is executed, the steps including the above method embodiments are executed; and the aforementioned storage medium includes: ROM, RAM, magnetic disk or optical disk and other media that can store program codes.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, but not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: The technical solutions described in the foregoing embodiments can still be modified, or some or all of the technical features thereof can be equivalently replaced; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the technical solutions of the embodiments of the present invention. scope.

Claims (10)

1. a data processing method, is characterized in that, comprises: Receive the authentication request sent by the client, and perform user authentication based on the authentication request; After the authentication is passed, if a data request sent by the client is received, corresponding data is sent to the cloud storage service CSS according to the data request, and corresponding records are performed according to the sent data; Receive the information fed back by the CSS, send corresponding data to the user terminal according to the received information, and perform corresponding recording according to the sent data. 2. The method according to claim 1, wherein the data request is a data upload request, the data upload request carries upload data, and the upload data includes a data tag, complete data and a hash value, wherein, the hash value is determined according to the complete data; The sending corresponding data to the CSS according to the data request, and performing corresponding recording according to the sent data, including: Splitting the complete data, and calculating the hash value of each data block after splitting; According to the hash value in the uploaded data and the calculated hash value, determine whether the complete data is correct; If the complete data is correct, data processing is performed according to the data mark, the processed data is sent to the CSS for storage, and corresponding recording is performed according to the sent data. 3. The method according to claim 2, wherein the receiving the information fed back by the CSS, sending corresponding data to the user terminal according to the information, and performing corresponding recording according to the sent data, comprising: Receive the storage result fed back by the CSS, generate a data list according to the storage result, send the data list to the client, and record the data list accordingly. The method according to claim 2 or 3, wherein the performing data processing according to the data mark, and sending the processed data to the CSS for storage, comprises: Determine whether data encryption needs to be performed according to the data mark; If it is determined that data encryption is required, a random number corresponding to each data block after division is generated respectively; Encrypt each data block after division according to the generated random number, and obtain ciphertext data according to the encryption result; The obtained ciphertext data is sent to the CSS for storage. 5. The method according to claim 1, wherein the data request is a data download request, and the data download request is determined by the user terminal according to a data list, and the data list is determined by a trusted third party TTP according to the The data stored in the CSS is generated; The receiving the information fed back by the CSS, sending corresponding data to the client according to the information, and performing corresponding recording according to the sent data, including: receiving the data to be downloaded fed back by the CSS, where the data to be downloaded is determined by the CSS according to the data download request; Splitting the data to be downloaded, and calculating the hash value of each data block after splitting; According to the stored hash value corresponding to the data to be downloaded and the calculated hash value, determine whether the data to be downloaded is correct; If the data to be downloaded is correct, data processing is performed according to the data tag corresponding to the data to be downloaded, the processed data is sent to the client, and corresponding records are performed according to the sent data. 6. The method according to claim 5, wherein the performing data processing according to the data tag corresponding to the data to be downloaded, and sending the processed data to the client, comprises: Determine whether data encryption needs to be performed according to the data mark; If it is determined that data encryption is required, obtain a random number corresponding to each data block after division; Encrypt each divided data block according to the obtained random number, and obtain ciphertext data according to the encryption result; Send the obtained ciphertext data to the client. The method according to claim 1, wherein the data request is a data deletion request, and the data deletion request is determined by the user terminal according to a data list, and the data list is stored by the TTP according to the CSS data generation; The receiving the information fed back by the CSS, sending corresponding data to the client according to the information, and performing corresponding recording according to the sent data, including: receiving a deletion certificate fed back by the CSS, the deletion certificate being generated by the CSS after deleting the data corresponding to the data deletion request; Save the deleted certificate, feedback the successful deletion information to the user terminal, update the data list according to the deleted certificate, send the updated data list to the user terminal, and perform corresponding processing on the updated data list Record. 8. The method according to claim 1, wherein after the authentication is passed, the method further comprises: If a query request sent by the client is received, the query request is recorded, and a target data list is determined from a data list according to the query request, wherein the data list is generated by TTP according to the data stored in the CSS; Sending the target data list to the client. 9. A data processing device, characterized in that it comprises a memory, a processor, and a computer-executable instruction stored in the memory and executable on the processor, wherein the processor implements the computer-executable instruction when the processor executes the computer-executable instruction. The data processing method according to any one of claims 1 to 8. 10. A computer-readable storage medium, characterized in that, computer-executable instructions are stored in the computer-readable storage medium, and when a processor executes the computer-executable instructions, the computer-executable instructions as claimed in any one of claims 1 to 8 are implemented. the data processing method described.

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