WO2008007533A1

WO2008007533A1 - Data deletion method and data deletion program

Info

Publication number: WO2008007533A1
Application number: PCT/JP2007/062706
Authority: WO
Inventors: Akiyoshi Okamoto
Original assignee: Japan Wave. Inc.
Priority date: 2006-06-23
Filing date: 2007-06-25
Publication date: 2008-01-17
Also published as: JP2008003892A

Abstract

[PROBLEMS] To provide a novel data deletion method and a data deletion program capable of deleting data in a short time without applying a load on a computer CPU or the like. [MEANS FOR SOLVING PROBLEMS] A data deletion program includes: a step for identifying a data file of data d to be deleted; a step for overwriting a random number at arbitrary plural positions in the data d; a step for rewriting file size information contained in file management information on the data file of the data d to '0' so as to change the file size of the data file; and a step for recording deletion information in the file management information on the data file of the data d and deleting the data file from the file system.

Description

Specification

Data deletion method and data deletion program

Technical field

The present invention relates to a data deletion method and a data deletion program for deleting data recorded in units of files in a recording device such as a hard disk of a personal computer.

Background art

Conventionally, when a data file is deleted by operating an operation unit of a personal computer, a file management program (file system) is processed in the computer, and only file management information of the data file to be deleted is deleted. It has become so. That is, the data file is only deleted on the file system, and the actual data remains on the hard disk. For this reason, if the data restoration program is processed by the computer, actual data on the hard disk may be read.

[0003] Therefore, the entire data to be deleted on the hard disk or an arbitrary place is overwritten with meaningless data (for example, random numbers, etc.) so that the data cannot be read in a complete state. There are some (see Patent Document 1).

[0004] Patent Document 1: Japanese Patent Laid-Open No. 2003-030801

Disclosure of the invention

Problems to be solved by the invention

[0005] However, when the entire data is overwritten, the data can be almost completely deleted, but the process of overwriting the entire data takes a lot of time, and the computer that performs the process does There is a disadvantage that it places a heavy burden on the CPU and recording device. In particular, when the amount of data to be deleted is very large, the above-described drawback becomes significant.

[0006] On the other hand, when overwriting an arbitrary portion of data, the processing can be performed in a short time and the burden on the CPU of the computer that performs the processing can be reduced. There is a drawback that it is possible to read the part other than the overwritten part of the data is there.

[0007] The present invention has been made in view of the above circumstances, and the object of the present invention is to be able to delete data in a short time without imposing a burden on the CPU of the computer. Is to provide a data deletion method and a data deletion program. Means for solving the problem

[0008] In order to solve the above-described problem, the data deletion method of the present invention specifies file management information corresponding to a file of data to be deleted, and deletes the file management information to thereby delete the data file. This is a method for deleting data on a file system, and before deleting the file management information, rewrites the file size information included in the specified file management information, thereby changing the file size of the file. It is characterized by having a variable step.

In performing the file size variable step, it is preferable to rewrite the file size information so that the file size of the file is smaller than the original size.

[0010] Further, the data deletion method may further include an overwriting step of overwriting a random number with respect to the file data before performing the file size variable step.

The invention's effect

[0011] According to the data deletion method of the present invention, the file management information of the file of the data to be deleted is specified, the file size information included in the file management information is rewritten, and thereby the file size of the file is variable. After that, the file is deleted on the file system. For this reason, even if the computer recovers the data recovery program and restores the file deleted on the file system, the file with a variable file size is read, and the data of the file is completely read. It becomes difficult to read. Since the file size variable processing for such a file only rewrites the file management information, it can be performed in a short time without imposing a heavy burden on the CPU or recording device of the computer that performs the processing.

[0012] In particular, when the file size of the file is made smaller than the original size, the relationship between the difference data recorded in the reduced portion of the file and the file is the file system. Be deleted on the system. In other words, the file can be made to appear as if it was originally reduced in size, so that even if the file is restored using a data restoration program, the difference data can be restored. Can be reduced. Therefore, if the size is reduced as much as possible, illegal reading of the data can be suitably prevented.

[0013] According to the data deletion program of the present invention, the same effect as the data deletion method can be obtained.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, a computer that processes a data deletion program according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of a computer in which a data deletion program according to an embodiment of the present invention is processed, FIG. 2 is a flowchart of the program, and FIG. 3 is a process of changing the file size of the data file of the program. It is a schematic diagram shown.

A computer 10 shown in FIG. 1 is a general-purpose personal computer, and includes a control unit 11 such as a CPU, a recording device 12, an operation unit 13, a communication unit 14, and a read / write unit 15.

[0016] The operation unit 13 is connected to an input device such as a keyboard and a mouse. The communication unit 14 is connected to a communication line such as the Internet. The read / write unit ₅ is a DVD drive or the like in which a recording medium such as a compact disk or a flash memory is set and data is read from and written to the recording medium.

The recording device 12 is a hard disk drive, in which basic programs such as a data deletion program shown in FIG. 2 and an operation program (not shown) processed by the control unit 11 are recorded in advance. In the recording device 12, data d is recorded in units of files. Hereinafter, the file is referred to as a data file.

A recording device 12, an operation unit 13, a communication unit 14, and a read / write unit 15 are connected to the input port of the control unit 11. On the other hand, to the output port of the control unit 11, a recording device 12, a communication unit 14 and a read / write unit 15 are connected. The control unit 11 functions as the computer 10 by processing the operation program.

[0019] The data file is a function of the operation program by the control unit 11. It is a file configured on the recording device 12 to manage (read / write and delete) data d by processing a file management program (file system). As the file system, the well-known FATFS (File Allocation

Tables File System), NTFS (NT File System), Ext2FS (Ext2 File System), etc.

This data file has a data area in which data d is recorded and a management area in which file management information for managing data d is recorded. The file management information includes information such as file name, extension, attribute, file size, update date and time, file start cluster number, and file end cluster number.

[0021] The contents of the data deletion program and the data deletion method will be described in detail below. First, this data deletion program is processed by the control unit 11 when an instruction to delete data d is input. The data deletion instruction includes an instruction input by an operation through an input device connected to the operation unit 13, or an instruction input by a data expiration management program (not shown) recorded in the recording device 12. The data expiration management program refers to the date and time when the data d was recorded in the recording device 12 by referring to the timer unit of the computer 10 and recorded in the recording device 12, and the date and time on the recording device 12 and the current date and time. When a predetermined period of time elapses, a data deletion program is started and the instruction input is input.

[0022] First, a command for specifying a data file of data d instructed to be deleted is executed (sl). Then, the file system of the operation program is processed, the file management information of the data file is searched, and the data file is specified.

[0023] After that, a command for overwriting random numbers at arbitrary plural positions is executed on the data d of the specified data file (s2). Then, the file system of the operation program is processed, and the data d is overwritten.

[0024] After that, when a file size variable command for the data file of the data d is executed (s3) o, the file system of the operation program is processed and, as shown in FIG. The included file size information is rewritten to “0” (that is, the file size variable processing of data d). [0025] Thereafter, a command for deleting the data file of the data d from the recording device 12 is executed (s4). Then, the file system of the operation program is processed, and deletion information is recorded in the file management information of the data file of data d. As a result, the data file is deleted from the file system. Then, the data deletion program process ends.

[0026] According to such a data deletion program, after the file size information of the data file of data d is rewritten to "0" through the file system of the operation program, the data file is deleted on the file system. ing. In other words, the relationship between the data d (difference data) recorded in the reduced portion of the data file and the file is deleted on the file system, and the data file has the file size “0” from the beginning. "I can pretend to be. For this reason, even if the data file deleted using the data recovery program is restored, only the data file with the file size “0” is restored. Can be prevented. However, since the random number is overwritten to any plurality of locations of the data d before the file size variable processing, by any chance, the original file size of the data file of the data d on the recording device 12 Even if traces of information are found and the data d is restored, the data d cannot be read completely. In this respect as well, illegal reading of data d can be prevented.

[0027] Furthermore, the file size variable processing can be performed in a short time without imposing a burden on the computer CPU or the recording device 12, so that the processing time of the data d deletion processing can be shortened. .

[0028] The data deletion program includes a step of specifying file management information of a file of data to be deleted, and deleting the data file on the file system by deleting the specified file management information. File size information included in the identified file management information before the file management information is deleted, thereby changing the file size of the file to a size different from the original size. As long as there is a variable step, no matter how much design changes are made, it will not work.

[0029] Further, the file size information is rewritten to "0" for the above file size variable processing. However, the present invention is not limited to this, and the end cluster number of the file may be rewritten. In this variable file size step, it is desirable to rewrite the file size information so that it is smaller than the original size. However, for data files with a structure in which data access information is written at the end of the file, By rewriting the file size information so as to be larger than the original size, the same effect as described above can be obtained by making the position of the access information unknown.

[0030] In addition, whether or not to include the contents of the processing in step 2 in the deletion program is arbitrary.

In addition, other processing can be incorporated into the deletion program. For example, the contents of the data management program.

[0031] Needless to say, the input of the data d deletion instruction to the deletion program is not limited to the above-described one. For example, the deletion instruction may be input at a predetermined date and time, or the deletion instruction may be input from the outside of the computer 10 through the communication unit 14.

[0032] As for the recording device 12, it is possible to use a recording medium such as a compact disc, a DVD, a flash memory, or the like, which is not limited to what is built into the computer 10 as a hard disk drive! What! /

[0033] The file system described above is an example, and it goes without saying that it can also be realized by using a file system having the same function. Also, it does not matter if the deletion program and the file system are configured integrally. As for the deletion of data files on the file system, the deletion information is recorded in the file management information. However, the present invention is not limited to this, and the file management information may be overwritten to delete the information. I do not care.

[0034] Note that any computer 10 can be used as long as it has a function capable of processing the deletion program.

Brief Description of Drawings

FIG. 1 is a block diagram of a computer in which a data deletion program according to an embodiment of the present invention is processed.

FIG. 2 is a flowchart of the program. FIG. 3 is a schematic diagram showing the process of variable file size processing of the data file of the program.

Explanation of symbols

10 computers

11 Recording device

d data

Claims

The scope of the claims

[1] In a data deletion method for identifying file management information of a data file to be deleted and deleting the data file on the file system by deleting the file management information.

Before deleting the file management information, the file size information included in the specified file management information is rewritten, thereby having a file size variable step for changing the file size of the file to a size different from the original size. How to delete featured data.

[2] The data deletion method according to claim 1, wherein the file size information is rewritten so that the file size of the file is smaller than the original size when performing the file size variable step. How to delete data.

[3] The data deletion method according to claim 1 or 2, further comprising an overwriting step of overwriting a random number on the data of the file before performing the file size variable step. How to delete data.

[4] A data file deletion program characterized by being a program for realizing the data deletion method according to claim 1, 2 or 3.