JP2013246678A - Storage device, storage medium, access pattern concealing method, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable execution in a built-in system and the like, dispense with dedicated hardware, and conceal an access pattern.SOLUTION: A storage device randomly rearranges data in a non-access area just once in an initial state; selects data in the non-access area according to a memory size in an access area and moves it to the access area; and, when there is an access to one data item, exchanges data between the access area and the non-access area, accesses another data item in the access area, and exchanges the data between the access area and the non-access area. When the access processing to the data to be accessed is finished, the storage device writes necessary data in the access area.

Description

  The present invention relates to a storage device, a storage medium, an access pattern concealment method, and a program for concealing an access pattern with realistic overhead.

  In recent years, attacks called side channel attacks against cryptography have become a major problem. As a side channel attack against software, there is an attack that analyzes memory access and restores secret information. In response to such an attack, Obvious RAM has attracted attention in order to protect memory access from attackers (see, for example, Non-Patent Document 1 and Non-Patent Document 2).

Odded Goldrich and Rafir Ostrovsky, “Software protection and simulation on oblivious RAMS,” J. ACM, 43 (3): 431-473, 1996. X. Zhuang et al. “Hardware Assisted Control Flow Obfuscation for Embedded Processors”, CASE 2004, 2004.

  However, the memory protection by the Obvious RAM, which has been studied in Non-Patent Document 1 and the like, has a problem that it has a large overhead and is difficult to put into practical use. Therefore, Non-Patent Document 2 proposes a memory protection method supported by hardware, but this method has a problem that an attacker can obtain information such as access frequency and order of data. There is also a restriction that dedicated hardware is necessary.

  Therefore, the present invention has been made in view of the above-described problems, and can be executed even in an embedded system, and does not require dedicated hardware, and can store an access pattern in a storage device and storage It is an object to provide a medium, an access pattern concealment method, and a program.

  The present invention proposes the following matters in order to solve the above problems. In addition, in order to make an understanding easy, although the code | symbol corresponding to embodiment of this invention is attached | subjected and demonstrated, it is not limited to this.

  (1) The present invention is a storage device in which a memory is divided into a data access area and a non-access area, and in the initial state, the data in the non-access area is rearranged at random once. Means (for example, equivalent to the rearrangement unit 110 in FIG. 1) and moving means for selecting data in the non-access area according to the memory size of the access area and moving it to the access area (for example, FIG. 1) When a single data is accessed, data is exchanged between the access area and the non-access area, and other data in the access area is also accessed. Control means for exchanging data between the access area and the non-access area (for example, equivalent to the control unit 130 in FIG. 1) and data to be accessed And a writing device (for example, corresponding to the writing unit 140 in FIG. 1) for writing out the necessary data in the access area when the access processing is completed. .

  According to the present invention, the rearranging means rearranges the data in the non-access area at random once in the initial state. The moving means selects the data in the non-access area according to the memory size of the access area and moves it to the access area. When access to one piece of data occurs, the control means exchanges data between the access area and the non-access area, and also accesses other data in the access area to access the non-access area. Exchange data with the region. The writing means writes necessary data in the access area when the access process to the data to be accessed is completed. Therefore, since the data in the non-access area is rearranged only once, the overhead increases as in the case of the Obliative RAM that rearranges the data in the non-access area many times at a predetermined timing. Can be prevented. Since data is exchanged between the access area and the non-access area when one data is accessed, the data access pattern can be concealed. Furthermore, since other data in the access area is also accessed and data is exchanged between the access area and the non-access area, the data access pattern can be concealed.

  (2) The present invention relates to a storage unit that stores data moved from the access area to the non-access area as history data in the history area (for example, corresponding to the storage unit 150 in FIG. 1). The control means includes the data to be accessed and the history when the data to be accessed does not exist in the access area, exists in the non-access area, and there is data stored in the history area. Arbitrary data stored in the area is moved to the access area, and the arbitrary data in the access area is moved to the history area and stored according to the moved data size. A device is proposed.

  According to the present invention, the storage means saves the data moved from the access area to the non-access area as history data in the history area, and the control means stores the data to be accessed in the non-access area without the access area. When there is data stored in the history area, the data to be accessed and any data stored in the history area are moved to the access area, and the data is in the access area according to the moved data size. Move any data to the history area and save it. Therefore, since the data to be accessed and the arbitrary data stored in the history area are moved to the access area and desired data is accessed, the data access pattern can be effectively concealed.

  (3) The present invention provides a storage unit (for example, corresponding to the storage unit 150 in FIG. 1) that stores data moved from the access area to the non-access area as history data in the storage device of (1). And when the data to be accessed is stored in the history area, the control means selects data that is not stored in the history area, and selects the data to be accessed and the selected data as the data to be accessed. A storage device is proposed that moves to an access area and moves and saves arbitrary data in the access area to the history area according to the moved data size.

  According to the present invention, the storage means stores data moved from the access area to the non-access area as history data in the history area, and the control means saves the history when the data to be accessed is stored in the history area. Select data not stored in the area, move the data to be accessed and the selected data to the access area, and move any data that was in the access area to the history area according to the moved data size save. Therefore, data that is not stored in the history area is selected, the data to be accessed and the selected data are moved to the access area, and the desired data is accessed. Can be concealed.

  (4) The present invention relates to a storage unit that stores data moved from the access area to the non-access area as history data in the storage area (for example, corresponding to the storage unit 150 in FIG. 1). And when the data to be accessed is stored in the access area, the control means moves the data randomly selected from the non-access area and the data to be accessed to the access area, and moves According to the data size, there is proposed a storage device characterized in that arbitrary data in the access area is moved and stored in the history area.

  According to the present invention, the storage unit stores the data moved from the access area to the non-access area as history data in the history area, and the control unit stores the non-access area when the data to be accessed is stored in the access area. Data randomly selected from the access area and data to be accessed are moved to the access area, and arbitrary data in the access area is moved to the history area and stored in accordance with the moved data size. Therefore, since the data selected at random from the non-access area and the data to be accessed are moved to the access area to access the desired data, the data access pattern can be effectively concealed.

  (5) The present invention proposes a storage device in which the access area has tamper resistance with respect to the storage devices of (1) to (4).

  According to the present invention, the access area has tamper resistance. In this case, since it is not necessary to access all data in the access area, the overhead can be further reduced. A SIM card or the like can be used as the storage device.

  (6) The present invention is a storage medium in which a memory is divided into a data access area and a non-access area, and in the initial state, the data in the non-access area is rearranged at random once. Means for selecting data in the non-access area according to the memory size of the access area and moving the data to the access area; and when access to one data occurs, Control means for exchanging data with the access area, accessing other data in the access area, and exchanging data between the access area and the non-access area, and data to be accessed And writing means for writing out the necessary data in the access area when the access process is completed. It has proposed a storage medium that.

  According to the present invention, the rearranging means rearranges the data in the non-access area at random once in the initial state. The moving means selects the data in the non-access area according to the memory size of the access area and moves it to the access area. When access to one piece of data occurs, the control means exchanges data between the access area and the non-access area, and also accesses other data in the access area to access the non-access area. Exchange data with the region. The writing means writes necessary data in the access area when the access process to the data to be accessed is completed. Therefore, since the data in the non-access area is rearranged only once, the overhead increases as in the case of the Obliative RAM that rearranges the data in the non-access area many times at a predetermined timing. Can be prevented. Since data is exchanged between the access area and the non-access area when one data is accessed, the data access pattern can be concealed. Furthermore, since other data in the access area is also accessed and data is exchanged between the access area and the non-access area, the data access pattern can be concealed.

  (7) The present invention relates to a method for concealing an access pattern in a storage device in which a memory is divided into a data access area and a non-access area, and in the initial state, the data in the non-access area is stored only once. A first step (for example, corresponding to step S100 in FIG. 2) that randomly rearranges, and a second step of selecting data in the non-access area according to the memory size of the access area and moving it to the access area (For example, corresponding to step S200 in FIG. 2) and when one data is accessed, data is exchanged between the access area and the non-access area, and other data in the access area A third step (for example, for accessing data and exchanging data between the access area and the non-access area) 2) (corresponding to step S300 in FIG. 2), and a fourth step (for example, corresponding to step S400 in FIG. 2) of writing necessary data in the access area when the access processing to the data to be accessed is completed. A method of concealing an access pattern characterized by comprising:

  According to the present invention, in the initial state, the data in the non-access area is randomly rearranged only once, and the data in the non-access area is selected according to the memory size of the access area and moved to the access area. When one data is accessed, data is exchanged between the access area and the non-access area, and other data in the access area is also accessed, and the access area and the non-access area are Exchange data between them. Then, when the access process to the data to be accessed is completed, necessary data in the access area is written out. Therefore, since the data in the non-access area is rearranged only once, the overhead increases as in the case of the Obliative RAM that rearranges the data in the non-access area many times at a predetermined timing. Can be prevented. Since data is exchanged between the access area and the non-access area when one data is accessed, the data access pattern can be concealed. Furthermore, since other data in the access area is also accessed and data is exchanged between the access area and the non-access area, the data access pattern can be concealed.

  (8) In the access pattern concealment method according to (7), in the third step, the data to be accessed does not exist in the access area, exists in the non-access area, and exists in the history area. When there is stored data, the data to be accessed and any data stored in the history area are moved to the access area, and according to the moved data size, any data in the access area An access pattern concealment method is proposed in which data is moved to the history area and stored.

  According to the present invention, when the data to be accessed does not exist in the access area, exists in the non-access area, and there is data stored in the history area, the data to be accessed and any arbitrary data stored in the history area are stored. Data is moved to the access area, and arbitrary data in the access area is moved to the history area and stored in accordance with the moved data size. Therefore, since the data to be accessed and the arbitrary data stored in the history area are moved to the access area and desired data is accessed, the data access pattern can be effectively concealed.

  (9) In the access pattern concealment method of (7), the present invention provides data that is not stored in the history area when data to be accessed is stored in the history area in the third step. The data to be accessed and the selected data are moved to the access area, and any data in the access area is moved to the history area and stored in accordance with the moved data size. We have proposed a method for concealing access patterns characterized by this.

  According to the present invention, when the data to be accessed is stored in the history area, the data not stored in the history area is selected, the data to be accessed and the selected data are moved to the access area, and moved. Depending on the data size, the arbitrary data in the access area is moved to the history area and stored. Therefore, data that is not stored in the history area is selected, the data to be accessed and the selected data are moved to the access area, and the desired data is accessed. Can be concealed.

  (10) In the access pattern concealment method according to (7), the present invention randomly selects from the non-access area when the data to be accessed is stored in the access area in the third step. An access pattern characterized in that data and the data to be accessed are moved to the access area, and arbitrary data in the access area is moved and stored in the history area according to the moved data size. A secret method is proposed.

  According to the present invention, when the data to be accessed is stored in the access area, the data randomly selected from the non-access area and the data to be accessed are moved to the access area, and according to the moved data size, Arbitrary data in the access area is moved to the history area and saved. Therefore, since the data selected at random from the non-access area and the data to be accessed are moved to the access area to access the desired data, the data access pattern can be effectively concealed.

  (11) The present invention is a program for causing a computer to execute an access pattern concealment method in a storage device in which a memory is divided into a data access area and a non-access area. A first step of randomly rearranging data in the non-access area (for example, corresponding to step S100 in FIG. 2), and selecting data in the non-access area according to the memory size of the access area; When a second step of moving to the access area (for example, corresponding to step S200 in FIG. 2) and access to one data occurs, data exchange is performed between the access area and the non-access area. The other access data in the access area is also accessed, and the access area and the non-access area A third step of exchanging data between them (for example, corresponding to step S300 in FIG. 2) and a fourth step of writing out necessary data in the access area when the access process to the data to be accessed is completed A program for causing a computer to execute steps (for example, corresponding to step S400 in FIG. 2) is proposed.

  According to the present invention, in the initial state, the data in the non-access area is randomly rearranged only once, and the data in the non-access area is selected according to the memory size of the access area and moved to the access area. When one data is accessed, data is exchanged between the access area and the non-access area, and other data in the access area is also accessed, and the access area and the non-access area are Exchange data between them. Then, when the access process to the data to be accessed is completed, necessary data in the access area is written out. Therefore, since the data in the non-access area is rearranged only once, the overhead increases as in the case of the Obliative RAM that rearranges the data in the non-access area many times at a predetermined timing. Can be prevented. Since data is exchanged between the access area and the non-access area when one data is accessed, the data access pattern can be concealed. Furthermore, since other data in the access area is also accessed and data is exchanged between the access area and the non-access area, the data access pattern can be concealed.

  (12) According to the present invention, in the program of (11), in the third step, data to be accessed does not exist in the access area, exists in the non-access area, and is stored in the history area If there is, the data to be accessed and the arbitrary data stored in the history area are moved to the access area, and the arbitrary data in the access area is transferred to the history according to the moved data size. A program characterized by moving to an area and saving is proposed.

  According to the present invention, when the data to be accessed does not exist in the access area, exists in the non-access area, and there is data stored in the history area, the data to be accessed and any arbitrary data stored in the history area are stored. Data is moved to the access area, and arbitrary data in the access area is moved to the history area and stored in accordance with the moved data size. Therefore, since the data to be accessed and the arbitrary data stored in the history area are moved to the access area and desired data is accessed, the data access pattern can be effectively concealed.

  (13) The present invention selects the data not stored in the history area when the data to be accessed is stored in the history area in the third step for the program of (11), The data to be accessed and the selected data are moved to the access area, and arbitrary data in the access area is moved to the history area and stored according to the moved data size. Propose a program to do.

  According to the present invention, when the data to be accessed is stored in the history area, the data not stored in the history area is selected, the data to be accessed and the selected data are moved to the access area, and moved. Depending on the data size, the arbitrary data in the access area is moved to the history area and stored. Therefore, data that is not stored in the history area is selected, the data to be accessed and the selected data are moved to the access area, and the desired data is accessed. Can be concealed.

  (14) According to the present invention, in the program of (11), when the data to be accessed is stored in the access area in the third step, the data randomly selected from the non-access area and the access A program is proposed in which data to be moved is moved to the access area, and arbitrary data in the access area is moved and stored in the history area in accordance with the moved data size.

  According to the present invention, therefore, the randomly selected data from the non-access area and the data to be accessed are moved to the access area to access the desired data, so that the data access pattern is effectively concealed. can do.

  According to the present invention, since the data in the non-access area is rearranged only once, there is an overhead like an Obvious RAM that rearranges the data in the non-access area many times at a predetermined timing. There is an effect that it can be prevented from becoming large. In addition, since data is exchanged between the access area and the non-access area when one data is accessed, the data access pattern can be concealed. Further, since other data in the access area is accessed and data is exchanged between the access area and the non-access area, the data access pattern can be concealed.

It is a figure which shows the structure of the memory | storage device which concerns on embodiment of this invention. It is a figure which shows the process of the memory | storage device which concerns on embodiment of this invention. It is the figure which showed the process of step 300 among the processes of the memory | storage device which concerns on embodiment of this invention in detail. It is the figure which showed the process of step 300 among the processes of the memory | storage device which concerns on embodiment of this invention in detail. It is the figure which showed the process of step 300 among the processes of the memory | storage device which concerns on embodiment of this invention in detail. It is a figure which shows the transition of the data in the storage area at the time of the access which concerns on the Example of this invention. It is a figure which shows the process of the memory | storage device which concerns on the Example of this invention. It is a figure which shows the process of the memory | storage device which concerns on the Example of this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
Note that the constituent elements in the present embodiment can be appropriately replaced with existing constituent elements and the like, and various variations including combinations with other existing constituent elements are possible. Therefore, the description of the present embodiment does not limit the contents of the invention described in the claims.

<First Embodiment>
The embodiment of the present invention will be described with reference to FIGS.

<Configuration of storage device>
As illustrated in FIG. 1, the storage device according to the present embodiment includes a rearrangement unit 110, a movement unit 120, a control unit 130, a writing unit 140, a storage unit 150, and a storage area 200. Yes. The storage device of the present invention includes not only a general storage device such as a RAM but also a storage medium such as a SIM or an IC card.

  In the storage area 200, the memory is divided into a data access area, a non-access area, and a history area. The access area, non-access area, and history area are composed of rewritable memories such as DRAM and SRAM. Further, the access area may be constituted by a rewritable memory such as a DRAM or SRAM having tamper resistance. The rearrangement unit 110 randomly rearranges the data in the non-access area only once in the initial state. The moving unit 120 selects data in the non-access area according to the memory size of the access area and moves it to the access area.

  When access to one piece of data occurs, the control unit 130 exchanges data between the access area and the non-access area, and also accesses other data in the access area so that the access area and the non-access area are not. Exchange data with the access area.

  For example, if the data to be accessed does not exist in the access area, exists in the non-access area, and there is data stored in the history area, the data to be accessed and any data stored in the history area are accessed. The data is moved to the area, and arbitrary data in the access area is moved to the history area and stored in accordance with the moved data size.

  In addition, when the data to be accessed is stored in the history area, the data not stored in the history area is selected, the data to be accessed and the selected data are moved to the access area, and the moved data size is set. In response, any data in the access area is moved to the history area and saved.

  In addition, when the data to be accessed is stored in the access area, the randomly selected data from the non-access area and the data to be accessed are moved to the access area, and the access area is matched with the moved data size. Move any data to the history area and save it.

  The writing unit 140 writes necessary data in the access area when the access process to the data to be accessed is completed. The storage unit 150 stores data moved from the access area to the non-access area as history data in the history area.

<Storage device processing>
Processing of the storage device according to this embodiment will be described with reference to FIGS.

  First, in the initial state, the data in the non-access area is randomly rearranged only once (step S100), and the data in the non-access area is selected according to the memory size of the access area and moved to the access area. (Step S200).

  Next, when one data is accessed, the data is exchanged between the access area and the non-access area, and other data in the access area is also accessed, and the access area and the non-access area And exchange data with each other (step S300).

  For example, if the data to be accessed does not exist in the access area, exists in the non-access area, and there is data stored in the history area, the data to be accessed and any data stored in the history area are The data is moved to the access area (step S311), and arbitrary data in the access area is moved to the history area according to the moved data size and stored (step S312).

  If the data to be accessed is stored in the history area, the data not stored in the history area is selected (step S321), the data to be accessed and the selected data are moved to the access area, In accordance with the moved data size, arbitrary data in the access area is moved to the history area and stored (step S322).

  If the data to be accessed is stored in the access area, the data randomly selected from the non-access area and the data to be accessed are moved to the access area (step S331), and the data size is changed according to the moved data size. The arbitrary data in the access area is moved to the history area and stored (step S332).

  When the access process to the data to be accessed is completed, necessary data in the access area is written (step S400).

  As described above, according to the present embodiment, data in the non-access area is rearranged only once. Therefore, data in the non-access area is rearranged many times at a predetermined timing. It is possible to prevent the overhead from becoming large as in the case of Oblivious RAM. Since data is exchanged between the access area and the non-access area when one data is accessed, the data access pattern can be concealed. Furthermore, since other data in the access area is also accessed and data is exchanged between the access area and the non-access area, the data access pattern can be concealed.

<Example>
Embodiments of the present invention will be described with reference to FIGS.

  In FIG. 6, when 1, 2,..., 9, A, B,..., F are data stored in the memory, the program is in the order of 5 → D → 8 → 5 → A. The memory transition when accessing data is shown. Hereinafter, this process will be described as an example. Regardless of the example of FIG. 6, the non-access area may be further divided into a plurality.

  First, in the initial state, the data in the non-access area is randomly rearranged only once (step S1100), and the data in the non-access area is selected according to the memory size of the access area and moved to the access area. (Step S1200).

  First, when accessing 5, since 5 is not included in the access area, 5 and another randomly selected data (2 in FIG. 6) are moved to the access area. Thus, 4 and B moving from the access area are stored in the history area and 5 is accessed. At this time, another data in the access area (2, 3, 8 in FIG. 6) is also accessed (step S1300).

  Next, when accessing D, since D is not included in the access area, D is moved to the access area, and another data is selected from the history area (for example, B in FIG. 6). Thereby, 5 and 8 moved from the access area are stored in the history area, and D is accessed. At this time, another data in the access area (3, B, 2 in FIG. 6) is also accessed (step S1400).

  Further, when accessing 8, since 8 is included in the history area, data other than the history area is randomly selected as another data (A in FIG. 6) and moved to the access area. To do. As a result, 3 and B moving from the access area are stored in the history area and 8 is accessed. At this time, another data in the access area (A, D, 2 in FIG. 6) is also accessed (step S1500).

  Furthermore, when accessing 5, since 5 is included in the history area, another data is selected at random (6 in FIG. 6) and moved to the access area. To do. Thus, 2 and 8 moving from the access area are stored in the history area and 5 is accessed. At this time, another data in the access area (A, D, 6 in FIG. 6) is also accessed (step S1600).

  Finally, when accessing A, since A is included in the access area, randomly selected data not included in the access area and data stored in the history area (in FIG. , F), move to the access area. Thus, 6 and D moving from the access area are stored in the history area and A is accessed. At this time, another data (5, F, 3 in FIG. 6) in the access area is also accessed (step S1700).

  When all the processes are completed, necessary data in the access area is written and the process ends (step S1800).

  Therefore, according to the present embodiment, it is possible to ensure the safety when accessing a certain number of times by storing the history and accessing the data contained therein every time, It is possible to conceal the access pattern with realistic overhead.

  The processing of the storage device and the storage medium is recorded on a recording medium that can be read by the computer system, and the program recorded on the recording medium is read into the storage device and the storage medium and executed to execute the storage device of the present invention. A storage medium can be realized. The computer system here includes an OS and hardware such as peripheral devices.

  Further, the “computer system” includes a homepage providing environment (or display environment) if a WWW (World Wide Web) system is used. The program may be transmitted from a computer system storing the program in a storage device or the like to another computer system via a transmission medium or by a transmission wave in the transmission medium. Here, the “transmission medium” for transmitting the program refers to a medium having a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line.

  The program may be for realizing a part of the functions described above. Furthermore, what can implement | achieve the function mentioned above in combination with the program already recorded on the computer system, what is called a difference file (difference program) may be sufficient.

  The embodiments of the present invention have been described in detail with reference to the drawings. However, the specific configuration is not limited to the embodiments, and includes designs and the like that do not depart from the gist of the present invention.

110; rearrangement unit 120; moving unit 130; control unit 140; writing unit 150; storage unit 200; storage area

Claims (14)

A storage device in which a memory is divided into a data access area and a non-access area,
In an initial state, rearrangement means for randomly rearranging data in the non-access area only once,
Moving means for selecting data in the non-access area according to the memory size of the access area and moving the data to the access area;
When one data is accessed, data is exchanged between the access area and the non-access area, and other data in the access area is also accessed, and the access area and the non-access area Control means for exchanging data with
Writing means for writing out the necessary data in the access area when the access process to the data to be accessed is completed;
A storage device comprising: A storage means for storing data moved from the access area to the non-access area as history data in the history area,
The control means includes
If the data to be accessed does not exist in the access area, exists in the non-access area, and there is data stored in the history area, the data to be accessed and any data stored in the history area The storage device according to claim 1, wherein, in accordance with the moved data size, arbitrary data in the access area is moved and stored in the history area. A storage means for storing data moved from the access area to the non-access area as history data in the history area,
The control means includes
When data to be accessed is stored in the history area, data that is not stored in the history area is selected, the data to be accessed and the selected data are moved to the access area, and moved 2. The storage device according to claim 1, wherein arbitrary data in the access area is moved and stored in the history area according to a data size. A storage means for storing data moved from the access area to the non-access area as history data in the history area,
The control means includes
When data to be accessed is stored in the access area, data randomly selected from the non-access area and the data to be accessed are moved to the access area, and the access is performed according to the moved data size. 2. The storage device according to claim 1, wherein arbitrary data in the area is moved to the history area and stored.   The storage device according to claim 1, wherein the access area has tamper resistance. A storage medium in which memory is divided into a data access area and a non-access area,
In an initial state, rearrangement means for randomly rearranging data in the non-access area only once,
Moving means for selecting data in the non-access area according to the memory size of the access area and moving the data to the access area;
When one data is accessed, data is exchanged between the access area and the non-access area, and other data in the access area is also accessed, and the access area and the non-access area Control means for exchanging data with
Writing means for writing out the necessary data in the access area when the access process to the data to be accessed is completed;
A storage medium comprising: An access pattern concealment method in a storage device in which a memory is divided into a data access area and a non-access area,
A first step of randomly rearranging data in the non-access area only once in an initial state;
A second step of selecting data in the non-access area according to the memory size of the access area and moving the data to the access area;
When one data is accessed, data is exchanged between the access area and the non-access area, and other data in the access area is also accessed, and the access area and the non-access area A third step of exchanging data with
A fourth step of writing necessary data in the access area when the access process to the data to be accessed is completed;
A method for concealing an access pattern, comprising: In the third step,
If the data to be accessed does not exist in the access area, exists in the non-access area, and there is data stored in the history area, the data to be accessed and any data stored in the history area 7. The access pattern according to claim 6, wherein arbitrary data in the access area is moved and stored in the history area according to the moved data size. Concealment method. In the third step,
When data to be accessed is stored in the history area, data that is not stored in the history area is selected, the data to be accessed and the selected data are moved to the access area, and moved 7. The method for concealing an access pattern according to claim 6, wherein arbitrary data in the access area is moved and stored in the history area according to a data size. In the third step,
When data to be accessed is stored in the access area, data randomly selected from the non-access area and the data to be accessed are moved to the access area, and the access is performed according to the moved data size. 7. The method for concealing an access pattern according to claim 6, wherein arbitrary data in the area is moved and stored in the history area. A program for causing a computer to execute an access pattern concealment method in a storage device in which a memory is divided into a data access area and a non-access area,
A first step of randomly rearranging data in the non-access area only once in an initial state;
A second step of selecting data in the non-access area according to the memory size of the access area and moving the data to the access area;
When one data is accessed, data is exchanged between the access area and the non-access area, and other data in the access area is also accessed, and the access area and the non-access area A third step of exchanging data with
A fourth step of writing necessary data in the access area when the access process to the data to be accessed is completed;
A program that causes a computer to execute. In the third step,
If the data to be accessed does not exist in the access area, exists in the non-access area, and there is data stored in the history area, the data to be accessed and any data stored in the history area The program according to claim 10, wherein arbitrary data in the access area is moved and stored in the history area in accordance with the moved data size. In the third step,
When data to be accessed is stored in the history area, data that is not stored in the history area is selected, the data to be accessed and the selected data are moved to the access area, and moved The program according to claim 10, wherein arbitrary data in the access area is moved and stored in the history area according to a data size. In the third step,
When data to be accessed is stored in the access area, data randomly selected from the non-access area and the data to be accessed are moved to the access area, and the access is performed according to the moved data size. The program according to claim 10, wherein arbitrary data in the area is moved to the history area and stored.

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