JP2008003892A - Data deletion method and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new data deletion method and a new data deletion program capable of deleting data in a short period of time without applying a load on a CPU and the like of a computer. <P>SOLUTION: The data deletion program includes a step s1 for specifying a data file of the data to be deleted, a step s2 for overwriting random numbers at a plurality of arbitral positions of the data, a step s3 for rewriting file size information included in file management information of the data file of the data with "0" so that the file size of the data file becomes variable and a step s4 for storing deletion information in the file management information of the data file of the data and deleting the data file from a file system. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

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

  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 so that only file management information of the data file to be deleted is deleted. It has become. That is, the data file is only deleted on the file system, and the actual data remains on the hard disk. For this reason, when the data restoration program is processed by the computer, actual data on the hard disk may be read.

  Therefore, there is a data that cannot be read in a complete state by overwriting meaningless data (for example, a random number) on the entire data to be deleted or an arbitrary place on the hard disk ( (See Patent Document 1).

Japanese Patent Laid-Open No. 2003-030801

  However, when the entire data is overwritten, the data can be almost completely deleted, but the process of overwriting the entire data takes a very long time, and the CPU or recording device of the computer that performs the process There is a drawback that a large burden is applied to the above. In particular, when the amount of data to be deleted is very large, the above-described drawback becomes significant.

  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 performing the processing can be reduced. There is a drawback that it is possible to read a portion other than the marked portion.

  The present invention has been developed in view of the above circumstances, and the object of the present invention is to provide new data that can be deleted in a short time without imposing a burden on the CPU of the computer. To provide a deletion method and a data deletion program.

  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 delete the data file on the file system. A method of deleting data to be deleted, comprising: a file size variable step for changing the file size of the file by rewriting the file size information included in the specified file management information before deleting the file management information. It is characterized by that.

  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.

  The data deletion method may further include an overwrite step of overwriting a random number on the file data before performing the file size variable step.

  In the case of the data deletion method of the present invention, the file management information of the file of the data to be deleted is identified, the file size information included in the file management information is rewritten, thereby changing the file size of the file, The file is deleted on the file system. For this reason, even if the data restoration program is processed by the computer and the file deleted on the file system is restored, the file with a variable file size is read, and the data of the file is read in a complete state. It becomes difficult. Since the file size variable processing of 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.

  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 deleted on the file system. That is, since the file can appear to have a reduced file size from the beginning, even if the file is restored using a data restoration program, the possibility of restoring the differential data is reduced. be able to. Therefore, if the size is made as small as possible, illegal reading of the data can be suitably prevented.

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

  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. 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 schematic diagram showing a process of variable file size processing of a data file of the program FIG.

  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.

  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 15 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 / written on the recording medium.

  The recording device 12 is a hard disk drive, in which basic programs such as an operation program (not shown) and a data deletion program shown in FIG. In the recording device 12, data d is recorded in file units. 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 an input port of the control unit 11. On the other hand, a recording device 12, a communication unit 14, and a read / write unit 15 are connected to the output port of the control unit 11. The control unit 11 functions as the computer 10 by processing the operation program.

  The data file is configured on the recording device 12 in order for the control unit 11 to manage (read / write and delete) data d by processing a file management program (file system) which is a function of the operation program. It is a file. As the file system, there are known FATFS (File Allocation Tables File System), NTFS (NT File System), Ext2FS (Ext2 File System), and the like.

  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 a file name, an extension, an attribute, a file size, an update date and time, a file start cluster number, and a file end cluster number.

  Hereinafter, the contents of the data deletion program and the data deletion method will be described in detail. First, the 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 term management program records the date and time when the data d was recorded in the recording device 12 with reference to the timer unit of the computer 10 and records the date and time on the recording device 12 and the current date and time. When the difference elapses a predetermined period, a data deletion program is started and the instruction input is input.

  First, a command for specifying a data file of data d instructed to be deleted is executed (s1). 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.

  Thereafter, a command for overwriting random numbers at arbitrary plural positions is executed for 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.

  Thereafter, a file size variable command for the data file of the data d is executed (s3). Then, the file system of the operation program is processed, and the file size information included in the file management information of the data file is rewritten to “0” as shown in FIG. 3 (that is, the file size variable processing of the data d). .

  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 on the file system. Then, the data deletion program process ends.

  In the case of 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. That is, 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 a file size “0” from the beginning. It can look like. For this reason, even if the deleted data file is restored by using the data restoration program, the data file having the file size “0” is only restored, so that illegal reading of the data d is preferably prevented. be able to. In addition, since the random number is overwritten on any plurality of locations of the data d before the file size variable processing, by any chance, the original file size information of the data file of the data d on the recording device 12 Even if the trace is found and the data d is restored, the data d cannot be completely read out. Also in this respect, illegal reading of the data d can be prevented.

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

  The data deletion program includes a step of specifying file management information of a file of data to be deleted, a step of deleting the data file on the file system by deleting the specified file management information, and file management How to change the design as long as there is a file size variable step to rewrite the file size information contained in the specified file management information before deleting the information, thereby reducing the file size of the file smaller than the original size It doesn't matter.

  In the file size variable process, the file size information is rewritten to “0”. 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, the file size information By rewriting to be larger than the original size, the position similar to the above can be obtained because the position of the access information becomes unknown.

  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.

  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.

  Although the recording device 12 is a hard disk drive, it is needless to say that the recording device 12 may be a recording medium such as a compact disk, a DVD, or a flash memory as well as the one built in the computer 10.

  The above-described file system is an example, and it goes without saying that it can be realized by using a file system having the same function. Further, the deletion program and the file system may be configured integrally. The deletion of the data file on the file system is recorded in the file management information. However, the present invention is not limited to this, and the file management information is overwritten to delete the information. It doesn't matter.

  Any computer 10 may be used as long as it has a function capable of processing the deletion program.

It is a block diagram of the computer by which the data deletion program which concerns on embodiment of this invention is processed. It is a flowchart of the program. It is a schematic diagram which shows the process of the file size variable process of the data file of the program.

Explanation of symbols

10 Computer 11 Recording device d Data

Claims (4)

In a data deletion method for identifying file management information of a file of data 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 making the file size of the file smaller than the original size. To delete 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.   3. The data deleting method according to claim 1, further comprising an overwriting step of overwriting a random number on the data of the file before performing the file size variable step. 4. A data file deletion program for realizing the data deletion method according to claim 1, 2, or 3.

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