JP4454489B2 - Browsing control method and program for files with browsing deadline - Google Patents

Description

  The present invention relates to a browsing control method and a program for allowing a viewer who has been granted browsing authority to browse a file with a browsing time limit.

Conventionally, as a method of restricting the browsing of confidential documents handed over to others, a method of authenticating whether or not the user is a regular viewer using a password is generally used. Even if a regular viewer wants to set a deadline, a browsing deadline is set in the file, and browsing is disabled when the deadline has expired compared to the PC internal clock.
However, since the PC user can arbitrarily change the PC internal clock, a malicious viewer can return the PC internal clock to the time before the browsing deadline and browse. As means for preventing this, there is one in the following document.
In Patent Document 1, the time is inquired to a server on the network. At this time, it was confirmed whether the time was falsified using an encryption technique.
In Patent Document 2, an inquiry is made to a clock in a hardware module having a tamper resistance outside the PC. In this case as well, it was confirmed whether the time has been falsified using encryption technology.
JP 2003-279675 A JP 2003-280522 A

  However, the techniques disclosed in Patent Documents 1 and 2 have a problem in that network connection and special hardware are required when checking the time, and there is a problem that costs are high, and a technique that does not require network connection and special hardware is desired. It was rare.

  The object of the present invention is to check the correct current time without providing a network connection or special hardware, and to allow browsing of files with a browsing deadline that can be browsed only within the browsing deadline. It is to provide a method and program.

In order to achieve the above object, the browsing control method according to the present invention provides time information that approximates the current time of the internal clock of a computer among files stored in storage means in a computer that browses files with a browsing time limit. The first step of extracting the file holding the time and the latest time information of the time information held in the extracted file and the time information of the computer internal clock are compared, and the time information of the computer internal clock is more If the file is old, the latest time information of the file is estimated as the correct current time, and the estimated current time is compared with the browsing deadline of the file with the browsing deadline to permit or prohibit browsing of the file with the browsing deadline. 2 steps.
In the first step, as a file stored in the storage unit, an e-mail file and a cache file of a Web page are set as time information extraction target files.
In the first step, as a file stored in the storage unit, a file created or updated by an application program in a computer is used as a time information extraction target file.

  The browsing control program according to the present invention extracts a file holding time information that approximates the current time of the internal clock of the computer from among the files stored in the storage means in the computer that browses the file with a browsing time limit. Step 1 is compared with the latest time information of the time information held in the extracted file and the time information of the computer internal clock, and when the time information of the computer internal clock is older, A process comprising a second step of estimating new time information as a correct current time, comparing the estimated current time with a browsing deadline of a file with a browsing deadline, and permitting or prohibiting browsing of the file with a browsing deadline. A step of causing a computer to execute is provided.

According to the present invention, if a user frequently uses e-mail or accesses a news article posting web site, a special hardware module can be used even if the user is not connected to the network when viewing a confidential file. The latest time information can be extracted from the browser cache memory when browsing the date field or received field of the body of the e-mail body or the news article on the website. If the latter is old, the former is estimated as the latest current time, and it is possible to control whether the browsing of the file with the browsing time limit is permitted or prohibited according to the estimated current time. Therefore, it is possible to prevent browsing of a file whose browsing deadline has passed by operating the computer internal clock illegally.
In this case, it is also possible to include files created or updated by the application program as targets for extracting time information, and to estimate the latest current time based on the creation time or update time of those files.

Hereinafter, the present invention will be described in detail based on embodiments.
FIG. 1 is an internal configuration diagram of a computer and a file showing an implementation environment of the present invention, and shows only main parts necessary for implementing the present invention.
In FIG. 1, reference numeral 110 denotes a personal computer (hereinafter referred to as a PC) used by a confidential file viewer.
Reference numeral 111 denotes a time inclusion file including the current time. Specifically, it is a cache file of an e-mail body or news article web site. Use multiple files to get the current time as accurate as possible.
Reference numeral 112 denotes a PC internal clock. In many cases, an almost accurate time is held, but since the PC user can change the time, it is possible to backdate to an old time.
Reference numeral 113 denotes a MAC address attached to the network card attached to the PC. Since the MAC address is a number unique to each network card, it can be used to identify the PC body.
Reference numeral 114 denotes a storage area for the user name of the PC user managed by the OS (operating system). Many OSs use a password corresponding to a user identification name to identify and authenticate the user before using the PC. That is, the PC cannot be used unless so-called login is successful.
Reference numeral 115 denotes a confidential file browsing program.
Reference numeral 120 denotes an external medium such as an FD (floppy disk) or a USB memory connected to the PC 110.
Reference numeral 121 denotes a part of the storage area of the external medium 120, which is an area for storing the latest one of the estimated current times recognized by the browsing program 115.
122 is a confidential file in the external medium 120, and is composed of parts 123-127.
Reference numeral 123 denotes a first component of the confidential file 122, which stores the MAC address 113 of the PC that is permitted to be browsed.
Reference numeral 124 denotes a second component of the confidential file 122, which is a user name and a password of a permitted person to be used for identification and authentication of the viewer of the confidential file 122.
Reference numeral 125 denotes a third component of the confidential file 122, which is a browsing time limit for the confidential file.
A fourth component 126 of the confidential file 122 is an area for storing the latest one of the estimated current times recognized by the browsing program 115 in the same manner as the latest time in the medium.
Reference numeral 127 denotes a fifth component of the confidential file 122, which is the content of the browsing target file itself. The file type and format are outside the scope of the present invention and will not be described in detail.

FIG. 2 shows the body of an electronic mail that is a first example of the time inclusion file 111. In general, an e-mail body is composed of a header and a body, and the header is composed of several fields. The main body is the body part of the mail.
Reference numeral 201 denotes a received field that is one component of the header, and there are many cases where there are a plurality of fields. This field 201 is given one after another whenever an e-mail passes through the gateware. Generally, the received field at the top is given later and includes newer time information. The format of this field varies depending on the gateway, but in many cases, includes the identifier of the transmission source machine, the identifier of the gateware, and the reception time when the gateway receives.
Reference numeral 202 denotes a mail destination.
Reference numeral 203 denotes a mail transmission source.
Reference numeral 204 denotes a mail transmission date and time.
205 is the title of the mail.
206 and after are the main body of the mail.

  FIG. 3 shows a cache file of a news article posting web site which is a second example of the time inclusion file 111. The cache file is in the HTML format, and the update date / time information is included in the BODY part of HTML corresponding to the main body.

<First Embodiment>
The best embodiment of the present invention will be described with reference to the flowchart of FIG.
As shown in FIG. 1, the confidential file 122 includes information necessary for three access controls: a MAC address 123 of a PC that can be browsed, an authorized user and a password 124 used for authentication, and a browsing time limit 125.
The browsing program 115 compares the access control information in the confidential file 122 with the time included in the MAC address 113 of the PC 110, the user name 114 managed by the OS, the PC internal clock 112 and the time inclusion file 111, and the access permission information. If so, the file content body 127 is displayed. Details are shown below.
First, in step 401, the user activates the browsing program 115. The browsing program 115 requests a password input necessary for displaying the confidential file 122 and is input by the user.
In step 402, the browsing program 115 accesses the mail text of FIG. 2 corresponding to the PC internal clock 112 and the time inclusion file 111 to obtain the estimated current time. In the case of the PC internal clock 112, it is easy to obtain the time. In many cases, it can be obtained by contacting the OS. In the case of the mail body shown in FIG. 2, the file format differs depending on the mail program being used, and the mail body in the mailbox is divided into a plurality of files and a single file. Separately described.
When there are a plurality of files, the one with the largest sequence number is often the latest mail body, and the time information in the date and received fields included in this file is used as the estimated current time. If a long processing time is allowed, all files are examined in the same way, and the latest time is set as the estimated current time.
If the mailbox is not a plurality of files but a single file, the time information of the date and received fields of all the mail texts in the file is examined, and the latest time is set as the estimated current time. Then, the time of the PC internal clock 112 and the newer time of the time inclusion file 111 are set as the estimated current time.
In step 403, the browsing program 115 compares the last in-medium time 121 in the external medium 120 with the previous estimated current time. If the estimated current time is old even after a certain period of time is considered, it is determined that some work has been done, an error is displayed, and this browsing process is terminated. That is, the file content main body 127 is not displayed. Note that the above-mentioned fixed time is for considering some errors, and assumes about one hour.
In step 404, the browsing program 115 stores the previous estimated current time in the latest in-medium time 121 in the external medium 120.
In step 405, the browsing program 115 compares the browsing deadline 125 of the confidential file 122 with the previous estimated current time. If the estimated current time has passed the browsing deadline 125 even after taking a certain time into consideration, it is determined that the browsing deadline has passed, an error is displayed, and the main browsing process is terminated. That is, the file content main body 127 is not displayed. Note that the above-mentioned fixed time is for considering some errors, and assumes about one hour.
In step 406, the browsing program 115 compares the user name 114 managed by the OS with the authorized user 124 in the confidential file 122, and the password obtained from the user in step 401 and the password 124 in the confidential file 122. In addition, the MAC address 113 and the permitted MAC address 123 in the confidential file 122 are compared. If even one of these three comparisons does not match, it is determined that the person is not a viewing authority or is not a viewing-permitted PC, an error is displayed, and the viewing process is terminated. That is, the file content main body 127 is not displayed.
In step 407, the browsing program 115 reads and displays the file content body 127 of the confidential file 122.

In the above description, the confidential file 122 has a format in which information 123 to 126 necessary for access control is simply added to the file content main body 127, so that a person with a certain level of technology may rewrite the expiry date 125. is there. Alternatively, the file content main body 127 may be directly accessed without using the browsing program 115. In order to prevent this, the entire confidential file 122 may be encrypted. If encrypted, the confidential file 122 is decrypted in step 405, and thereafter, each of the components 123 to 127 may be accessed.
Further, the estimated current time recognized by the browsing program 115 is stored in the latest in-medium time 121, but this may be stored in the latest in-file time 126 of each individual confidential file 122, or stored in both. May be. In this case, in step 403, the estimated current time is also compared with the latest time in the file. By using the latest time in the file, it becomes possible to carry a confidential file using an attached file of an email instead of the external medium 120.
In the above description, the browsing PC 110 is also restricted using the MAC address 113. If the permitted MAC address 123 is NULL, there is also a method for improving the convenience of the user, assuming that there is no restriction.

<Second Embodiment>
In the first embodiment, the mail text in FIG. 2 is used as the time inclusion file 111. In addition, there is a web site cache file for posting news articles as a file containing time information. As shown in FIG. 3, the update time can be handled as the current time.

<Third Embodiment>
In the first and second embodiments, the PCs and viewers who browse the confidential file 122 are limited. However, in some cases, it may be desired to change the authorized MAC address 123 or authorized user and password 124 with the authority of the current authorized user in order to work on another PC or to entrust another person. An embodiment for realizing this will be described below.
Here, a technique is shown in which the confidential file 122 is once uploaded to the server, changed, and downloaded.
FIG. 5 is a diagram showing the exchange between the client (PC 110 in FIG. 1) and the server realizing the third embodiment, and will be described together with the flowchart in FIG.
First, in step 601 of FIG. 6, the user starts the client program and inputs the name of the confidential file 122 and the password.
In step 602, as shown at 501 in FIG. 5, the confidential file 122 is uploaded from the client program to the server program, and the user name 114 and the password obtained in the previous step are transmitted together.
In step 603, the server program confirms whether the authorized user and password 124 in the confidential file 122 received earlier match the user name and password sent from the client PC 110 in the previous step. . As indicated by 502 in FIG. 5, if they match, OK is transmitted, and if they do not match, NG is transmitted to the client program.
If the client program receives NG at step 604, it displays an error and ends. When OK is received, a new file name and a new user name and password to be permitted are obtained from the user.
In step 605, as shown at 503 in FIG. 5, a new user name and password are transmitted to the server program.
In step 606, the server program determines that the permitted MAC address 123 is NULL, the authorized user and password 124 have received the new user name and password, and the expiry date 125 is the expiry date of the confidential file received in 501 of FIG. The same confidential file is generated and transmitted to the client program as indicated at 504 in FIG.
In step 607, the client program stores the received file in the client PC 110 with a new file name previously obtained from the user.

<Fourth embodiment>
In the above embodiment, the time information included in the file contents is focused. However, a method using the update date and time of the file in the PC 110 may be used. That is, a method of estimating the latest update date and time of a file in the PC 110 as the current time, or estimating the newer one compared with the estimated current time obtained in the first embodiment or the second embodiment The current time may be set.

It is an internal block diagram of a computer and a file showing an implementation environment of the present invention. It is a figure which shows the example of the electronic mail text containing time. It is a figure which shows the example of the cache file of the web page containing time. It is a flowchart which shows a confidential file browsing process. It is a sequence diagram which shows the exchange of the client and server at the time of a browsing permission person change. It is a flowchart which shows a browsing authorized person change process.

Explanation of symbols

110 PC for browsing confidential files
111 File containing current time 112 PC internal clock 113 MAC address of PC 114 Login user name managed by OS 115 Viewing program 120 External medium 121 Latest current time stored in external medium 122 Confidential file 123 Viewable PC MAC address 124 Permitted user and password 125 Expiration date 126 Latest current time stored in the confidential file 127 Confidential file content body 201 Received field 202 Destination field 203 Source field 203 Transmission date and time field

Claims (4)

A computer having an internal clock controls the browsing of a file with a browsing time limit stored in a storage means,
A first step in which the browsing means of the computer extracts a file holding the latest time information among the files stored in the storage means; the time information held in the extracted file; Compare the time information of the clock, estimate the newer time as the current time, and store it in the predetermined area of the storage means, and compare the stored current time with the viewing time limit of the file with the viewing time limit And a third step of permitting or prohibiting the browsing of the file with the browsing time limit, and controlling the browsing of the file with the browsing time limit.   2. The expiration date according to claim 1, wherein, in the first step, an e-mail file or a cache file of a Web page is used as a time information extraction target file as the file stored in the storage unit. File browsing control method.   2. The time information extraction target file according to claim 1, wherein, in the first step, a file created or updated by an application program in a computer is used as a file stored in the storage unit as a time information extraction target file. Browsing control method for files with browsing deadline. A computer with an internal clock, a viewing access limit with files stored in the storage means in said computer a program for executing a control,
A first means for extracting a file holding the latest time information among files stored in the storage means; a time information held by the extracted file; Compares the time information of the clock, estimates the newer time as the current time, and compares the stored current time with the viewing time limit of the file with the viewing time limit, and stores it in a predetermined area of the storage means. And a browsing control program for a file with browsing deadline, which functions as a third means for permitting or prohibiting browsing of the file with browsing deadline.

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