JP2001127748A - Method for deciphering ciphered file - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the operability for deciphering ciphered files linked with a link descriptor. SOLUTION: This invention is a deciphering method for deciphering plural ciphered files linked with a link descriptor and has a procedure of setting a deciphering key abc12 for deciphering a 2nd ciphered file af14 to be deciphered later in a 1st ciphered file af12 to be deciphered first and a procedure of deciphering the 2nd ciphered file af13 by using the deciphering key abc12 set in the 1st ciphered file. Consequently, a user need not input the deciphering key each time each ciphered file which is linked is deciphered.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a decryption method for decrypting a plurality of encrypted files linked by a link descriptor, and more particularly to an encrypted file transmitted through various networks such as the Internet. And a decoding method.

[0002]

2. Description of the Related Art When performing information communication via various networks such as the Internet, encrypted communication is performed to maintain the confidentiality of communication information. In this encrypted communication, the sender encrypts information using a predetermined encryption key, and the receiver who has received the encrypted information via the network uses the decryption key corresponding to the encryption key. Is to be decoded.

As one form of a system for performing such encrypted communication, HTTP (Hyper Text Transfer Protocol) is used.
ol) There is an encrypted communication system on the Internet including a server. In this system, an encrypted file stored in an HTTP server (hereinafter, referred to as a server) is transmitted to a receiver terminal alone or together with a plain text file via the Internet. ). In this encrypted communication, an encrypted file can be displayed in the same manner as a plaintext file by adding a program (decryption plug-in) for decrypting the encrypted file to the browser. In this decryption plug-in, decryption is performed using a decryption key unique to the recipient, so that only a valid recipient can decrypt and display the encrypted file, and restricts access to the file. be able to.

[0004] Such a conventional encrypted communication system on the Internet will be specifically described. FIG.
FIG. 5 is a block diagram showing the configuration of the encryption communication system,
It is a conceptual diagram of the file communicated by the conventional encryption communication system. In FIG. 4, a server 1, a sender terminal 2, and a receiver terminal 3 are communicably connected via the Internet 4. An operating system (OS) 11 and a server application 12 are stored and operable in the server 1, and a magnetic disk 13 is provided. The caller terminal 2 has OS2
1, encryption software 22, and FTP (File Transfer Pr
The OS 31, browser 32, and decryption plug-in 33 are stored and operable in the otocol 23 and the recipient's terminal 3, respectively.

In such an information communication system, H
A case where a plurality of plaintext files and an encrypted file described in TML (Hypertext Markup Language) are transmitted will be described. Here, each file is stored in the browser 32
It corresponds to each page displayed in order, the file corresponding to the first page is a plain text file,
The file corresponding to each page after the second page is an encrypted file, which is called by the link button displayed on the immediately preceding page.

[0006] The sender transmits the plaintext file and the encrypted file encrypted by the encryption software 22 to the server 1 using the FTP 23. The server 1 stores the transmitted plaintext file and encrypted file on the magnetic disk 13 and transmits them in response to a request from the receiver.

The recipient terminal 3 first receives a plaintext file, which is interpreted by the browser 32 and displayed as the first page. Next, when the link button provided on the first page is selected, the encrypted file corresponding to the second page is called, and the encrypted file is transmitted from the server 1 and interpreted by the browser 32. Since the process of decrypting the encrypted file cannot be performed by the browser 32 itself, it is transferred to the decryption plug-in 33. Since a decryption key is required for this decryption, the decryption plug-in 33 displays a dialog screen and prompts the recipient to input the decryption key. If the input decryption key is valid, a plaintext file can be obtained by decryption using the decryption key. The plaintext file is transferred to the browser 32 and displayed as the second page. Similarly, in order to display the third page, an input of a decryption key for decrypting the encrypted file corresponding to the third page is required, and the n-th page (n is an arbitrary integer) is displayed. To do this,
An input of a decryption key for decrypting the encrypted file corresponding to the page is required.

[0008]

As described above, in the configuration of the conventional encrypted communication system, the receiver needs to input the decryption key every time the encrypted file is decrypted. Requires the input of the decryption key by the number of times, and the operation of the receiver becomes complicated.

Also, in such a conventional encrypted communication, since different decryption keys are set for each recipient, the sender prepares a large number of encrypted files having the same contents but different decryption keys. It is necessary to make the magnetic disk 1
There is a problem that an enormous capacity is required for a storage device such as a third storage device. For example, as shown in FIG.
If there are n encrypted files per person, a total of Mx
Since n encrypted files are required, the number of encrypted files to be stored in the server becomes enormous.

[0010] The present invention has been made in view of the above-mentioned problems in the conventional encrypted communication system, and can reduce the file size of the sender when communicating a plurality of encrypted files, and can reduce the file size of the receiver. The purpose is to improve the operability of the device.

[0011]

SUMMARY OF THE INVENTION The present invention relates to a decryption method for decrypting a plurality of encrypted files linked by a link descriptor. The decryption method of the present invention comprises the steps of: setting a decryption key for decrypting a second encrypted file to be decrypted later in a first encrypted file to be decrypted first; When the second encrypted file is called by the link descriptor of the first encrypted file, the second encrypted file is decrypted using the decryption key set in the first encrypted file. And a procedure for converting the

The present invention also provides a method for decoding a first
Enter the decryption key for decrypting the encrypted file of
A procedure for requesting a user, a procedure for storing a decryption key input by the user, a procedure for decrypting the first encrypted file using the stored decryption key, The link descriptor of the previously decrypted encrypted file containing the encrypted file of
And decrypting the second encrypted file using the stored decryption key when the encrypted file is called.

In these cases, it is preferable that the plurality of encrypted files are stored in a server on a network, and the decryption of the plurality of encrypted files is performed in a terminal on the network.

Preferably, the encrypted file is page data that can be displayed by a WWW browser, and the link descriptor is described in the page description language.

[0015] Furthermore, it is preferable that a decryption key set in the encrypted file is set in the link descriptor.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on one embodiment shown in the drawings. FIG. 1 is a diagram showing a communication file and a display page of a browser according to the present embodiment, and FIG. 2 is a flowchart of a decoding process in a decoding plug-in. Note that the overall configuration of the encrypted communication system according to the present embodiment is the same as the overall configuration of the related art shown in FIG.

In the network system shown in FIG. 4, the magnetic disk 13 of the server 1 stores a plurality of plaintext files hf1 to hfm described in HTML and a plurality of encrypted files af11 to afmn. Each of the plaintext files hf1 to hfm describes a page P1 (so-called main page) displayed first on the browser 32 of the terminal 3 on the receiver side, and includes a plaintext file hf1 for the recipient 1 and a plaintext file hf1 for the recipient m. Plain text file hf
The number is provided in accordance with the number m of recipients, such as m. Each of the encrypted files af11 to afmn describes each page P2 to Pn displayed sequentially from the second page onward. The encrypted files af12 on the second page for the recipient 1 and 3 for the recipient 1 Encrypted file a of the page
f13, encrypted file af on page n for recipient m
mn, the number is provided according to the number of pages 2 to n and the number m of recipients.

[0018] Of these, page 1
The case where the plaintext file hf1 describing .about.Pn and the encrypted files af12 to 1n are transmitted will be described. However, the same encrypted communication can be performed for the other recipients 2 to m.

The upper part of FIG. 1 shows pages P1 to P3 displayed on the browser 32. The lower part of FIG. 1 shows a plaintext file hf1 describing each page P1 to P3 and encrypted files af12 and af13. Illustration of other pages and encrypted files is omitted.

Different decryption keys are set for each of the encrypted files af12 to af1n for each recipient and each file. Here, the decryption key for the encrypted file af12 is “abc12” and the encrypted file af13 Is set as “abc13”, and the decoding key of the encrypted file af1n is set as “abc1n”.

Each of the plaintext file hf1 and the encrypted files af12 to af1n is transferred to the decryption plug-in 33 in order for the decryption plug-in 33 to perform processing relating to display of the next encrypted file. A link descriptor (specifically, a tag such as EMBED) for instructing is described, and, following the link descriptor, various parameters for defining the processing contents of the decoding plug-in 33 are described. ing. The parameters include the file name of the next encrypted file, the setting of whether or not to display a link button for calling the next encrypted file (hereinafter, button display setting), and the next encrypted file. Of the decryption key for decrypting the encrypted file
Key setting) is included. For example, as shown in FIG. 1, the parameters described in the plain text file hf1 are “file name = af12”, “button display setting = yes” (yes
s indicates a button, no indicates a parameter that does not display a button), and “key setting = NULL” (NULL indicates a blank value). The parameters described in the first encrypted file af12 are set as “file name = af13”, “button display setting = yes”, “key setting = abc13”, and described in the next encrypted file af13. Parameter is "file name =
af14 "," button display setting = yes ", and" key setting = abc14 ". That is, in each key setting of each of the encrypted files af12 to af1n, a decryption key for decrypting the next encrypted file is described.

In the communication of each file configured as described above, first, the recipient inputs a predetermined URL (Uniform Resource Locator) to the browser 32 of the terminal 3 to transmit the plaintext file hf1 in the server 1. To instruct. The plaintext file hf1 is received from the server 1 receiving this instruction.
Is transmitted and received by the terminal 3, the plaintext file hf1 is interpreted by the browser 32, and the page P1 is displayed.

Here, when the link descriptor described in the plaintext file hf1 is interpreted, the above-described parameters are sent to the decoding plug-in 33. The decoding plug-in 33 that has received this first determines the presence or absence of the button setting by interpreting the button display setting of the parameters (201 in FIG. 2). Here, since “button display setting = yes”, the link button LB1 is displayed on the browser 32 (202). Here, the process in the decoding plug-in 33 is in a state of waiting for the link button LB1 to be selected by clicking or the like (203). On the other hand, when there is no button setting, the decoding process described later is started immediately without displaying the button.

Next, when the link button LB1 provided on the page P1 is selected by clicking or the like, the server 1 is instructed to transmit the encrypted file af12 as the next file. When the encrypted file af12 is transmitted from the server 1 receiving this instruction and received by the terminal 3 on the receiver side, the encrypted file af12 is passed to the decryption plug-in 33.

The decryption plug-in 33 decrypts the encrypted file af12 by using the parameters in the plaintext file hf1 passed before. In this decryption, first, the content of the key setting is determined (204). Here, since “key setting = NULL”, the dialog DL for prompting the receiver to input the decryption key
Is displayed on the screen (205). Then, the receiver waits for the input of the decryption key (206). When the decryption key is input, the input decryption key is stored in the encrypted file af.
12 (207), and using this, the encrypted file af12 is decrypted (20).
8). If the input decryption key is “abc12”, the encrypted file af12 is properly decrypted to become the decrypted file af12.
2 is passed to the browser 32 and interpreted, and the page P2
Is displayed.

Further, when interpreting the decrypted file af12, since the link descriptor is described in the decrypted file af12, the link descriptor is interpreted, and the parameters are set to the decryption plug-in 33. Sent to Then, as described above, the link button LB2 is displayed on the page P2 by interpreting the button display setting.

When the link button LB2 is selected by clicking or the like, the next encrypted file af13 is stored in the terminal 3.
And passed to the decryption plug-in 33. When decrypting the encrypted file af13, the decryption plug-in 33 determines the contents of the key setting described in the decrypted file af12. Here, when any decryption key is set in the key setting, the set decryption key is set as the decryption key of the encrypted file af13 (209), and the decryption key of the encrypted file af13 is decrypted by using this. Is performed (208). Here, since “key setting = abc13” is described in the decryption file af12 as described above, the encryption file af13 is decrypted using the “abc13” as a decryption key.

Thereafter, similarly, the next encrypted file af
14 is decrypted as the key setting “abc1” described in the encrypted file af13 decrypted immediately before.
4 ”is used as a decryption key, and the encrypted file af1n
At the time of decryption, "a" described as a key setting is described in the encrypted file af1 (n-1) decrypted immediately before.
bc1n ”is used as a decryption key. Therefore, the recipient 1 only needs to input the decryption key “abc12” for decrypting the first encrypted file af12 when displaying the page P2, and when displaying the subsequent pages P3 to Pn, Since the encrypted files af13 to af1n are decrypted and displayed without any input of a decryption key, the operability for displaying the received file is improved. The key settings described in each of the encrypted files af12 to af1n are stored in the encrypted files af12 to af1n.
Since it is transmitted after being encrypted as a part of f1n, it is not illegally known to a third party.

In the above description, a different decryption key is set for each of the encrypted files af12 to 1n.
In this case, the operability of the receiver is improved, but the number of files to be stored in the server 1 is not reduced. The problem is that a different decryption key is set for each recipient only for the first encrypted pages af12 to afm2, and for the subsequent encrypted pages af13 to afln, a decryption key common to all recipients (for example, This can be solved by setting abc). In this case, for all the encrypted pages af12 to afmn, “key setting = abc”
And the same decryption key "ab
c ".

Then, the first encrypted pages af12 to af12
The fm2 is decrypted using the decryption key input to the dialog DL (204 to 207 and 2 in FIG. 2).
08), and subsequent encrypted pages af13 to af1n are decrypted using the same decryption key of the encrypted file decrypted immediately before (204-209-2).
08). Therefore, in the same manner as described above, each page after page P3 can be sequentially displayed without inputting a decryption key, and operability can be improved.
In particular, in this case, as shown in FIG. 3, even when the number of recipients is M, the first encrypted pages af12 to af
For m2 only, set a different decryption key for each recipient,
Since the subsequent encrypted pages af13 to af1n can be shared for each recipient, the server 1
Can reduce the number of files to be stored.

When the content of the key setting is determined by the decryption plug-in 33 (204 in FIG. 2), if there is no key setting itself, decryption is performed using the decryption key used for the previous decryption. If there is no decryption key used for the immediately preceding decryption, a dialog or the like may be displayed to allow the receiver to input the decryption key and to hold the decryption key.
In this case, a common decryption key “abc” is set for all the encrypted files including the first encrypted file,
The description of the key setting included in all of these encrypted files is omitted.

For example, after decrypting the encrypted file af12 using the decryption key “abc” input to the dialog DL, when determining the key setting described in the decrypted file af12, Since there is no key setting itself in the description of af12, it is determined whether or not there is a previous decryption key (210). Here, since the decryption key “abc” is held, this is set as the decryption key of the encrypted file af13 (211), and the decryption key “abc” is set.
The encrypted file af13 is decrypted using "c" (208). In this case as well, each page subsequent to page P3 can be sequentially displayed without inputting the decryption key, and the operability can be improved. In particular,
Since it is not necessary to describe key settings in all the encrypted files, file creation becomes easy. When the key setting used for the immediately preceding decryption is not exceptionally present, for example, when the immediately preceding key setting is erased due to an interrupt process or the like, the dialog is displayed in the same manner as when displaying the page P2. The DL can be displayed and a key can be entered (210 to 20).
5).

The embodiment of the present invention has been described with reference to the drawings. However, it is apparent that the present invention is not limited to the matters described in the above embodiments, and that changes, improvements, and the like can be made based on the description in the claims. For example, in the above-described embodiment, an example in which communication is performed via the Internet has been described, but the type of network is not limited to this. The decryption of the encrypted file may be performed not by a plug-in module such as a decryption plug-in, but by using decryption software that functions in any other form. The setting of the decryption key can be described in the encrypted file in any format according to any description language, in addition to the format such as the key setting described above.

[0034]

As described above, according to the present invention, by inputting only the decryption key for decrypting the first encrypted file, the encryption can be performed without inputting any decryption key thereafter. The file can be decrypted and displayed. Therefore, the operability for displaying the received file is improved.

Further, the decryption key described in the encrypted file is encrypted and transmitted as a part of the encrypted file, so that it is not illegally known to a third party. Furthermore, by setting a common decryption key for each encrypted file, the number of encrypted files to be stored in the server can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing a communication file together with a display page of a browser according to an embodiment of the present invention.

FIG. 2 is a flowchart of a decoding process in a decoding plug-in.

FIG. 3 is a conceptual diagram of a file communicated in the encryption communication system.

FIG. 4 is a block diagram illustrating a configuration of an encryption communication system.

FIG. 5 is a conceptual diagram of a file communicated in a conventional encrypted communication system.

[Description of Signs] 1 server 2 terminal (sender side) 3 terminal (recipient side) 4 Internet 11, 21, 31 OS 12 server application 13 magnetic disk 22 encryption software 23 FTP 32 browser 33 decryption plug-in

Claims (5)

[Claims] 1. A decryption method for decrypting a plurality of encrypted files linked by a link descriptor, wherein the decrypted files are decrypted later in a first encrypted file decrypted first. Setting a decryption key for decrypting the second encrypted file; and setting the first encrypted file when the second encrypted file is called by the link descriptor of the first encrypted file.
Decrypting the second encrypted file using a decryption key set in the encrypted file. 2. A decryption method for decrypting a plurality of encrypted files linked by a link descriptor, comprising: a decryption key for decrypting a first encrypted file to be decrypted first. Requesting the user to input the information, a procedure for storing the decryption key input by the user, and a procedure for decrypting the first encrypted file using the stored decryption key. The linked decryption key of the previously decrypted encrypted file containing the first encrypted file causes the stored decryption key to be stored when the second decrypted file that is decrypted later is called. Decrypting the second encrypted file by using the second method. 3. The method according to claim 1, wherein the plurality of encrypted files are stored in a server on a network, and the decryption of the plurality of encrypted files is executed in a terminal on the network. How to decrypt encrypted files. 4. The apparatus according to claim 1, wherein the encrypted file is page data that can be displayed by a WWW browser, and the link descriptor is described in the page description language. How to decrypt encrypted files. 5. The method for decrypting an encrypted file according to claim 4, wherein a decryption key set in the encrypted file is set in the link descriptor.