JP2015148907A - data storage device, method, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a data storage device, method and program for preventing original data from being obtained even when data are copied from a server by an illegal user, and for preventing the original data from being restored even when the data are not correctly deleted by the server.SOLUTION: A data storage device 10 is configured to receive data from a user terminal 50, to convert the received data into an AONT (All Or Nothing Transform) block constituted of n pieces of blocks by an AONT algorithm, to separate at least one block among the blocks constituting the converted AONT block from the other blocks for storage, to restore the data on the basis of the separated and stored block, and to delete the separated and stored data.

Description

  The present invention relates to a data storage device, method, and program.

  Conventionally, a technique for guaranteeing the integrity of data stored on the server side and the integrity of processing on the server side has been proposed (for example, Non-Patent Document 1). In such a technique for guaranteeing data integrity, data is generally made redundant by encoding data to be stored. If redundancy is given to data, even if a part of stored data is changed, most of the data needs to be changed. Such a technique prevents the server from trying to change data without the permission of the client.

Giuseppe Athenise, Randal C.I. Burns, Reza Curtmola, Joseph Herring, Lea Kissner, Zachary N .; J. et al. Peterson, Dawn Xiaodong Song, “Provable data position at untrusted stores”, Proceedings of the 2007, ACM Conference on Computer and Communications 7

However, with the method described above, it is possible to guarantee that the server holds the data correctly, but even if the user deletes data that is no longer needed, it ensures that the data was deleted correctly. I can't. In addition, when data is copied without permission, the copied data cannot be protected.
For example, in an environment such as a public cloud, there may be an unauthorized user or an internal unauthorized person. If there are unauthorized users, the stored data can be copied without permission and stored on another server. When data is stored in another server without permission, even if a user deletes data stored in a cloud service, it is impossible to delete data stored by an unauthorized user. Even if the user encrypts the data, if the unauthorized user obtains the secret key by some method or restores the original data using the vulnerability to encryption, the data that should have been deleted May be available to attackers.

  Such an apparatus that solves the problems of the prior art is desired. In other words, there is a need for an apparatus that prevents original data from being acquired even if the data is copied from a server by an unauthorized user, and prevents original data from being restored even if the data is not properly deleted by the server. Yes.

  The present invention provides a data storage device that prevents original data from being acquired even if the data is copied from a server by an unauthorized user, and prevents original data from being restored even if the data is not properly deleted by the server. It is an object to provide a method and a program.

Specifically, the following solutions are provided.
(1) A data storage device that stores data from a user terminal in a cloud server via the Internet, the data receiving unit receiving the data from the user terminal, and the data received by the data receiving unit, Data conversion means for converting to an AONT block composed of n blocks by an AONT algorithm, at least one of the blocks constituting the AONT block converted by the data conversion means, and the other blocks A storage means for separating and storing the data, a data restoring means for restoring the data based on the blocks separated and stored by the storage means, and deleting the data separated and stored by the storage means Data deletion means for Data storage device.

  According to the configuration of (1), the data storage device according to the present invention receives data from a user terminal, and converts the received data into an AONT block composed of n blocks by an AONT (all or notifying transform) algorithm. Data that has been converted, and at least one of the blocks constituting the converted AONT block and other blocks are separated and saved, data is restored based on the separated and saved blocks, and the separated and saved data Is deleted.

That is, the data storage device according to the present invention converts received data into an AONT block, and separates and stores at least one block among the blocks constituting the converted AONT block.
Therefore, since the data storage device according to the present invention separates a part of the data integrated as an AONT block, even if the data is copied from the server by an unauthorized user, the original data is not acquired. And can ensure that the original data is not restored if the data is not properly deleted by the server.

  (2) further comprising block storage means for storing the block, wherein the storage means stores the at least one block in the block storage means, and stores the other block in the cloud server; The data storage device according to (1), wherein the data deletion unit deletes the data by deleting the at least one block stored in the block storage unit.

  Therefore, since the data storage device according to (2) stores a part of the data integrated as an AONT block in the block storage means of the data storage device, it is assumed that the data is copied from the server by an unauthorized user. Can be further ensured that the original data is not acquired, and even if the data is not deleted properly by the server, the original data is not restored by deleting some data stored in the block storage means Can be further ensured.

  (3) The data conversion means further includes data division means for dividing the data, the data division means divides the data into k groups, and the data conversion means is divided by the data division means. The group is converted into the AONT block, and the storage unit stores at least one block in the block storage unit and stores the other block in the cloud server for each group. The data storage device according to (2).

That is, the data storage device according to (3) divides the data into groups and integrates the divided groups as AONT blocks, so that when updating data, the overhead is reduced and the data is accessed as AONT blocks. The amount of data to be reduced can be reduced.
Therefore, the data storage device according to (3) can prevent the original data from being restored even if the data is copied from the server by an unauthorized user or the data is not properly deleted by the server. Therefore, it is possible to reduce the amount of data required for data access and to access the data at high speed.

  (4) The data dividing means divides the data into k groups, and each of the groups is configured by a predetermined arrangement, and the data converting means is divided into the groups divided by the data dividing means. The k data arranged in the same array position in the group is converted into an AONT block composed of k blocks by the AONT algorithm, and the storage means converts at least one block for each AONT block. The data storage device according to (3), wherein the data is stored in the block storage unit and the other block is stored in the cloud server.

That is, the data storage device according to (4) divides the data into groups constituted by a predetermined arrangement, and integrates k pieces of data arranged at the same arrangement position in each divided group as an AONT block. Therefore, when updating data, the amount of data accessed as an AONT block can be further reduced.
Therefore, the data storage device according to (4) can prevent the original data from being restored even if the data is copied from the server by an unauthorized user or the data is not properly deleted by the server. Therefore, it is possible to further reduce the amount of data required for the access and to access the data at high speed.

  (5) The data conversion means further includes data division means for dividing the data, the data division means divides the data into k groups, and the data conversion means is divided by the data division means. The group is converted into the AONT block, and the storage means separates the blocks constituting each AONT block, stores them in a mixed manner using a secret function, and deletes the data. The data storage device according to (1), wherein the means deletes the data by deleting the secret function.

That is, the data storage device according to (5) divides the data into groups, integrates the divided groups as AONT blocks, separates the blocks constituting each integrated AONT block, and Based on the function, it is mixed and saved.
Therefore, the data storage device according to (5) stores the blocks constituting the AONT block in a mixed manner using a secret function, so that even if the data is copied from the server by an unauthorized user, the original data Can be prevented from being obtained, and even if the data is not properly deleted by the server, the original data is not restored by deleting the secret function.

  (6) A method executed by the data storage device according to (1), wherein the data receiving unit receives the data from the user terminal, and the data converting unit includes the data receiving step. A data conversion step of converting the received data into an AONT block composed of n blocks by an AONT algorithm, and the storage means of the blocks constituting the AONT block converted by the data conversion step A storage step for separating and storing at least one of the blocks and the other block, and data for restoring the data on the basis of the block separated and saved by the storage step by the data restoration means A restoring step and the data deleting means; The method of and a data deleting step for deleting the data stored being separated by said storing step.

  Therefore, the method according to the present invention can prevent the original data from being obtained even if the data is copied from the server by an unauthorized user, and the original data is not deleted even if the data is not properly deleted by the server. It can be prevented from being restored.

  (7) A program for causing a computer to execute each step of the method according to (6).

  Therefore, the program according to the present invention can cause the computer to prevent the original data from being acquired even if the data is copied from the server by an unauthorized user, and even if the data is not correctly deleted by the server. Data can be prevented from being restored.

According to the present invention, even if data is copied from a server by an unauthorized user, the original data is not acquired, and the original data is not restored even if the data is not properly deleted by the server. Can do.
According to the present invention, even if an internal unauthorized person or the like in the cloud illegally copies data, it can be guaranteed that the data cannot be restored if the user performs a deletion process. If the present invention is applied, the reliability of the cloud can be improved.

It is a figure which shows the structure of the data storage apparatus which concerns on 1st Embodiment of this invention. It is a flowchart which shows the process of the data storage apparatus which concerns on 1st Embodiment of this invention. It is a figure which shows the example of the data which the data storage apparatus which concerns on 1st Embodiment of this invention preserve | saves. It is a figure which shows the example of the division | segmentation of the data which the data storage apparatus which concerns on 1st Embodiment of this invention preserve | saves. It is a figure which shows another example of the division | segmentation of the data which the data storage apparatus which concerns on 1st Embodiment of this invention preserve | saves. It is a figure which shows the example of the division | segmentation by the arrangement | sequence of the data which the data storage apparatus which concerns on 1st Embodiment of this invention preserve | saves. It is a flowchart which shows the process of the data storage apparatus which concerns on 2nd Embodiment of this invention. It is a figure which shows the example of the data which the data storage apparatus which concerns on 2nd Embodiment of this invention preserve | saves.

[First Embodiment]
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a configuration of a data storage device 10 according to the first embodiment of the present invention.
The data storage device 10 is a device that stores data from the user terminal 50 in the cloud server 30 via the Internet 70, and includes a data reception unit 11, a data conversion unit 12, a storage unit 13, and a data restoration unit 14. And data deletion means 15 and block storage means 20.
In the first embodiment, the data storage device 10 separates the blocks constituting the AONT block and stores them in the block storage means 20 and the cloud server 30. Each means will be described.

  The data receiving unit 11 receives data from the user terminal 50.

The data conversion unit 12 converts the data received by the data reception unit 11 into an AONT block composed of n blocks by the AONT algorithm.
The data conversion means 12 may encrypt the data and convert the encrypted data into an AONT block.

  The AONT algorithm converts data into a plurality of blocks. At this time, the AONT algorithm performs conversion so that access is required to all blocks when reading / writing the data. If one of the converted blocks is deleted by this conversion, the original data cannot be restored even if all the remaining blocks are obtained.

  The storage unit 13 stores at least one block among the blocks constituting the AONT block converted by the data conversion unit 12 and another block separately.

For example, the storage unit 13 stores at least one block in the block storage unit 20 and separates and stores other blocks in the cloud server 30 (see FIG. 3 described later). The storage unit 13 may store at least one block in the user terminal 50 and separate and store other blocks in the cloud server 30 for storage.
The data restoration unit 14 restores data based on the blocks separated and saved by the storage unit 13, that is, all blocks.
The data deletion unit 15 deletes the data separated and stored by the storage unit 13, for example, the block stored in the block storage unit 20. That is, the data deleting unit 15 makes the data unrecoverable by deleting at least one of the AONT blocks. If at least one block is stored in the user terminal 50 by the storage unit 13, the data deletion unit 15 deletes the block in the user terminal 50. Or the user terminal 50 may delete the block in the user terminal 50 locally.

Furthermore, the case where the data conversion means 12 is provided with the data division means 121 which divides | segments data is demonstrated.
The data dividing unit 121 divides the data into k groups. As the value of k, for example, an appropriate value may be set by the user. Also, the value of k may be calculated by √n when the data is composed of n blocks, for example.
The data conversion unit 12 converts each group divided by the data division unit 121 into an AONT block, and the storage unit 13 stores at least one block in the block storage unit 20 for each group. The block is stored in the cloud server 30 (see FIGS. 4 and 5 described later).
The data deletion unit 15 deletes all k blocks stored in the block storage unit 20. That is, by this processing, the data deleting unit 15 deletes at least one block of each AONT block so that each AONT block cannot be restored.

The data dividing unit 121 may divide the data into k groups, each group having a predetermined arrangement.
The data converting means 12 converts k data arranged at the same array position in each group divided by the data dividing means 121 into an AONT block composed of k blocks by the AONT algorithm, and saves the data. 13 stores at least one block for each AONT block in the block storage unit 20 and stores other blocks in the cloud server 30 (see FIG. 6 described later). The predetermined array may be arranged three-dimensionally as well as one-dimensional or two-dimensional (not only a square matrix but also a rectangular matrix).

  FIG. 2 is a flowchart showing processing of the data storage device 10 according to the first embodiment of the present invention. The data storage device 10 is configured by hardware included in a computer and its peripheral devices and software that controls the hardware, and the following processing is processing that each control unit (for example, CPU) executes according to predetermined software. is there. FIG. 2A is a flowchart showing the data storage process of the data storage device 10.

In step S101, the CPU (data receiving unit 11) receives data.
In step S102, the CPU (data dividing unit 121) divides the data received in step S101 into groups.
In step S103, the CPU (data conversion unit 12) converts the data divided in step S102 into an AONT block for each divided group.
In step S <b> 104, the CPU (storage unit 13) stores some blocks for each AONT block converted in step S <b> 103 in the block storage unit 20, and stores other blocks in the cloud server 30. That is, the CPU stores some blocks in the block storage unit 20 and transmits other blocks to the cloud server 30 for storage.

  FIG. 2B is a flowchart showing the data deletion process of the data storage device 10.

In step S111, the CPU (data deletion unit 15) deletes the block saved in the block storage unit 20 from the AONT block. If the block is stored in the user terminal 50, the CPU deletes the block in the user terminal 50. Or the user terminal 50 may delete the block in the user terminal 50 locally.
In step S <b> 112, the CPU (data deletion unit 15) requests the cloud server 30 to delete other blocks that are remaining blocks among the AONT blocks.

FIG. 3 is a diagram illustrating an example of data stored by the data storage device 10 according to the first embodiment of the present invention. The example of FIG. 3 is an example of converting one file into an AONT block 100 composed of 32 blocks using the AONT algorithm. The data storage device 10 stores, for example, only the block of block number 1 in the block storage unit 20 among the blocks constituting the AONT block 100, transmits the blocks of block number 2 to block number 32 to the cloud server 30, and The server 30 stores it.
Since the unauthorized user cannot access the block number 1, even if the analysis is performed using all the blocks having the block numbers 2 to 32 stored in the cloud server 30, information regarding the file cannot be obtained.
When the user deletes data, the data storage device 10 requests the cloud server 30 to delete after deleting only the block of block number 1. Once the block is deleted, the attacker cannot restore the original data.

FIG. 4 is a diagram illustrating an example of division of data stored by the data storage device 10 according to the first embodiment of the present invention. The example of FIG. 4 does not create one AONT block composed of n blocks in one file, but divides one file into k groups and creates k AONT blocks. It is an example.
As shown in FIG. 4, the data storage device 10 creates, for example, four AONT blocks 100, 200, 300, and 400. As for each AONT block, the AONT block 100 has block numbers 1 to 8, the AONT block 200 has block numbers 9 to 16, the AONT block 300 has block numbers 17 to 24, and the AONT block 400 has block numbers 25 to 32. The data storage device 10 holds the blocks of block number 1, block number 9, block number 17, and block number 25 in the block storage means 20, and transmits the remaining blocks to the cloud server. This increases the data size to be held, but the number of accesses required for reading and writing can be reduced from 32 blocks to 8 blocks, and the speed can be increased.
When the user deletes data, the data storage device 10 requests the cloud server 30 to delete after deleting block number 1, block number 9, block number 17, and block number 25.

FIG. 5 is a diagram illustrating another example of division of data stored by the data storage device 10 according to the first embodiment of the present invention. The example of FIG. 5 is an example in which the number of blocks constituting the AONT block is calculated based on n pieces of data constituting one file, and the block having the calculated number of blocks is set as one AONT block. In FIG. 5, an AONT block composed of sqrt (n) blocks, for example, 6 is calculated from √32, and six AONT blocks 100, 200, 300, 400 composed of the calculated 6 blocks. , 500, 600 (AONT block 600 is composed of two blocks (block number 31, block number 32)). This method is effective when the size of n increases.
When the user deletes the data, the data storage device 10 deletes the block number 1, the block number 7, the block number 13, the block number 19, the block number 25, and the block number 31, and then deletes the data to the cloud server 30. Request.

FIG. 6 is a diagram showing an example of division based on the arrangement of data stored by the data storage device 10 according to the first embodiment of the present invention. In the example of FIG. 6, one file composed of 64 data is divided into 4 groups (each group is composed of data arranged by a 4 × 4 matrix). 4 data (for example, the block number 3, the block number 19, the block number 35, the block number 35, and the block number 51 in the first row and the third column) arranged in the same array position in each of the group, are converted into one AONT block 300. It is an example converted to.
When the user deletes data, the data storage device 10 requests the cloud server 30 to delete after deleting the block numbers 1 to 16.

[Second Embodiment]
The data storage device 10 separates the blocks constituting the AONT block and stores them in the cloud server 30. The configuration of the data storage device 10 is the same as that of the first embodiment.
The data conversion unit 12 includes a data division unit 121 that divides data, and the data division unit 121 divides the data into k groups. The data conversion unit 12 converts each group divided by the data division unit 121 into an AONT block, and the storage unit 13 separates the blocks constituting each AONT block and mixes them using a secret function. (See FIG. 8 to be described later). The data deleting unit 15 deletes data by deleting a secret function. The secret function may be stored in the block storage unit 20 or the user terminal 50 in association with the AONT block.

  FIG. 7 is a flowchart showing the processing of the data storage device 10 according to the second embodiment of the present invention. FIG. 7A is a flowchart showing data storage processing of the data storage device 10.

In step S201, the CPU (data receiving unit 11) receives data.
In step S202, the CPU (data dividing unit 121) divides the data received in step S201 into groups.
In step S203, the CPU (data conversion means 12) converts the data divided in step S202 into an AONT block for each divided group.
In step S <b> 204, the CPU (storage unit 13) stores the blocks constituting the AONT block in the cloud server 30 in a mixed manner using a secret function. That is, the CPU transmits to the cloud server 30 and stores data in which blocks are mixed together using a secret function.

  FIG. 7B is a flowchart showing the data deletion process of the data storage device 10.

In step S211, the CPU (data deleting unit 15) deletes the secret function used in step S204.
In step S212, the CPU (data deleting unit 15) requests the cloud server 30 to delete the data.

FIG. 8 is a diagram illustrating an example of data stored by the data storage device 10 according to the second embodiment of the present invention. The example of FIG. 8A is an example of four AONT blocks 100, 200, 300, and 400 created from one file (AONT block 100 has block numbers 1 to 8, AONT block 200 has block numbers 9 to 16, The AONT block 300 is composed of block numbers 17 to 24, and the AONT block 400 is composed of block numbers 25 to 32).
The example of FIG. 8 (2) is an example in which, in the four AONT blocks 100, 200, 300, and 400, the blocks constituting each AONT block are shuffled using a secret function and mixed together.
However, the cloud server 30 may be able to identify the AONT block depending on the pattern in which the data storage device 10 accesses the AONT block. For this reason, when this method is used, it is necessary to conceal the access pattern using a technique such as an Obvious RAM. For example, when the data storage device 10 reads one AONT block, the data storage device 10 reads the block constituting the AONT block and the block constituting the other AONT block from each other, and which block constitutes the AONT block. It is read in such a way that it is unknown whether it is or not, and the access pattern is concealed.
When the user deletes data, the data storage device 10 deletes the secret function.

According to the first embodiment, the data storage device 10 receives data from the user terminal 50, converts the received data into an AONT block composed of n blocks by an AONT (all or notifying transform) algorithm, At least one block among the blocks constituting the converted AONT block is stored in the block storage unit 20, and another block is stored in the cloud server 30, and data is deleted by deleting the block stored in the block storage unit 20. delete.
Therefore, since the data storage device 10 stores a part of the data integrated as the AONT block in the block storage means 20, even if the data is copied from the cloud server 30 by an unauthorized user, the original data Can be prevented from being acquired, and even if the data is not correctly deleted by the cloud server 30, the original data is not restored by deleting some data stored in the block storage means 20. Can do.
Furthermore, the data storage device 10 divides the data into k groups, converts each divided group into an AONT block, stores at least one block for each group in the block storage means 20, and other Are stored in the cloud server 30.
Therefore, the data storage device 10 can prevent the original data from being restored even if the data is copied from the cloud server 30 by an unauthorized user or the data is not correctly deleted by the cloud server 30, Therefore, it is possible to reduce the amount of data required for data access and to access the data at high speed.

According to the second embodiment, the data storage device 10 divides data into groups, integrates the divided groups as AONT blocks, and separates the blocks constituting each integrated AONT block, Based on a secret function, they are stored together.
Therefore, the data storage device 10 can prevent the original data from being acquired even if the data is copied from the cloud server 30 by an unauthorized user, and even if the data is not correctly deleted by the cloud server 30, It is possible to prevent the original data from being restored by deleting the secret function.

  As mentioned above, although embodiment of this invention was described, this invention is not restricted to embodiment mentioned above. The effects described in the embodiments of the present invention are only the most preferable effects resulting from the present invention, and the effects of the present invention are limited to those described in the embodiments of the present invention. is not.

DESCRIPTION OF SYMBOLS 10 Data storage apparatus 11 Data reception means 12 Data conversion means 121 Data division means 13 Storage means 14 Data restoration means 15 Data deletion means 20 Block storage means 30 Cloud server 50 User terminal 70 Internet 100,200,300,400,500,600 AONT block

Claims (7)

A data storage device that stores data from a user terminal in a cloud server via the Internet,
Data receiving means for receiving the data from the user terminal;
Data converting means for converting the data received by the data receiving means into an AONT block composed of n blocks by an AONT algorithm;
Storage means for separating and storing at least one of the blocks constituting the AONT block converted by the data conversion means and the other blocks;
Data restoration means for restoring the data based on the blocks separated and saved by the storage means;
Data deletion means for deleting the data separated and stored by the storage means;
A data storage device comprising: Block storage means for storing the block;
The storage unit stores the at least one block in the block storage unit, and stores the other block in the cloud server;
The data deleting means deletes the data by deleting the at least one block stored in the block storage means;
The data storage device according to claim 1. The data converting means further comprises data dividing means for dividing the data,
The data dividing means divides the data into k groups,
The data converting means converts the group divided by the data dividing means into the AONT block,
The storage unit stores at least one block in the block storage unit and stores the other block in the cloud server for each group.
The data storage device according to claim 2. The data dividing unit divides the data into k groups, and each of the groups is configured by a predetermined arrangement,
The data converting means converts k data arranged at the same array position in each group divided by the data dividing means into AONT blocks composed of k blocks by the AONT algorithm,
The storage unit stores at least one block for each AONT block in the block storage unit, and stores the other block in the cloud server.
The data storage device according to claim 3. The data converting means further comprises data dividing means for dividing the data,
The data dividing means divides the data into k groups,
The data converting means converts the group divided by the data dividing means into the AONT block,
The storage means separates the blocks constituting each of the AONT blocks, stores them in a mixed manner using a secret function,
The data deleting means deletes the data by deleting the secret function;
The data storage device according to claim 1. A method performed by the data storage device according to claim 1, comprising:
A data receiving step in which the data receiving means receives the data from the user terminal;
A data conversion step in which the data conversion means converts the data received in the data reception step into an AONT block composed of n blocks by an AONT algorithm;
A storing step in which the storing unit separates and stores at least one of the blocks constituting the AONT block converted by the data converting step and the other block; and
A data restoring step in which the data restoring means restores the data based on the blocks separated and saved by the saving step;
A data deletion step in which the data deletion means deletes the data separated and stored in the storage step;
A method comprising:   The program for making a computer perform each step of the method of Claim 6.

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