JP3815107B2 - Method for generating and browsing encrypted file using common key - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a data file generation method and a browsing method using a common key used by a plurality of viewers having different decryption keys.
[0002]
[Prior art]
In recent years, information sharing environments using computer networks have rapidly spread. By storing documents and other information to be shared on a network server and accessing them from a large number of clients, the management and use efficiency of the information is greatly improved. In such an environment, there is a demand to limit users who can view specific information. For example, in an in-house network environment, it is necessary to configure so that a target document can be viewed only by a specific officer, only by a specific department, or only by a specific employee.
[0003]
In order to meet this type of request, there is a method in which target information is encrypted using an information encryption technique, and only a person having a decryption key corresponding to this encryption can view it.
[0004]
One of the conventional methods using encryption technology is to set a security level that limits the viewers, encrypt the target information with a different key for each security level, and only those who have the decryption key for it. The target information can be browsed.
[0005]
However, in this method of setting a key for each security level, in order to allow a specific user to view information on a plurality of security levels, a plurality of keys must be managed. On the side, key management becomes complicated. For example, in the in-house network, it is necessary to distribute the keys corresponding to the officer level and the division level to be supervised to the officers, and use them appropriately as necessary. In addition, it is difficult to provide information to a group of users who do not follow a preset security level, and there is a problem that the degree of freedom for selecting a person to be viewed is low.
[0006]
Another conventional method using an encryption technique is to set an individual decryption key for each user and encrypt information with an encryption key corresponding to the decryption key for each target user of information. 7 and 8 show a conventional encrypted file creation and browsing system according to the above method. First, a method of encrypting and providing the document P having the same contents to the users A to C in the conventional encrypted file creation method will be described with reference to FIG. As shown in the figure, unique encryption keys KEA, KEB, and KEC are determined in advance for each of the users A to C, and the document P is encrypted using each encryption key KE, and ciphertexts CA to CC are obtained. Is generated. That is, the system encrypts the document P for the user A using the encryption key KEA in the encryption unit 70, and generates the document CA on the main memory. The writing unit 71 stores the document CA on the main memory as one data file on the hard disk of the server. Similarly, a ciphertext CB for user B is generated using the encryption key KEB, and a ciphertext CC for user C is generated using the encryption key KEC, and stored as a data file on the server.
[0007]
As shown in FIG. 8, the ciphertexts CA to CC are decrypted by using the decryption keys KDA to KDC in the clients operated by the users A to C. That is, the user A reads the ciphertext CA from the main memory of the client, and the decryption unit 81 decrypts the ciphertext CA using the decryption key KDA corresponding to the encryption key KEA to obtain the original document P. . Similarly, in the clients of user B and user C, the ciphertexts CB and CC are decrypted using the decryption keys KDB and KDC, respectively.
[0008]
[Problems to be solved by the invention]
However, according to the above conventional method, although the key management on the user side and the administrator side becomes easy, as in the above example, when there are a plurality of users who can view the same document, Since as many data files as the number of users are created, there is a possibility that the number of files stored on the server may become enormous, which causes a management problem.
[0009]
Accordingly, an object of the present invention is to provide an encrypted file generation method and a browsing method that can easily manage an encrypted document and a key necessary for the encryption.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a method for generating a data file used by a plurality of viewers having different decryption keys, and a procedure for encrypting at least one browsed information with a predetermined common encryption key; A procedure for encrypting a common decryption key corresponding to the predetermined common encryption key with an encryption key corresponding to the different decryption key, the encrypted browsed information, and the plurality of encrypted common decryption keys And a procedure for storing the key as at least one data file.
[0011]
In addition, the method for generating the encrypted file includes a step of encrypting a predetermined determination code with an encryption key corresponding to the different decryption key and the same key for each encrypted common decryption key. A procedure for associating the encrypted determination codes with each other, wherein the storing procedure includes the encrypted browsed information and the plurality of encrypted common decryption keys together with the determination code. It is preferable to save the data file.
[0012]
The method for generating the encrypted file further includes a procedure for generating position information for specifying a position of at least the encrypted browsed information in the data file, and the storing procedure is the encrypted file. The browsed information is preferably stored as a data file together with the position information.
[0013]
The present invention is also a method for browsing an encrypted file generated by the above method, the procedure for loading the data file onto the main memory, and a plurality of encrypted common decryption keys in the data file. A procedure for sequentially decrypting with the decryption key possessed by the viewer, a procedure for sequentially determining whether or not the decrypted common decryption key is correctly decrypted with the common decryption key before encryption, and a correct decryption The encrypted common decryption key is used to decrypt the encrypted browsed information, and the decrypted browsed information is displayed to the viewer.
[0014]
In addition, the method for browsing the encrypted file further includes a step of sequentially decrypting the plurality of encrypted determination codes with a decryption key possessed by the viewer, and the step of determining is decrypted. By sequentially comparing the determination code with the determination code before encryption to determine whether or not the decrypted common decryption key is correctly decrypted with the common decryption key before encryption. It is preferable that
[0015]
In the encrypted file browsing method, it is preferable that the procedure for decrypting the browsed information further includes a procedure for extracting the browsed information from the data file based on the position information.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail based on the illustrated embodiment. FIG. 1 is a system configuration diagram for realizing a method for creating an encrypted file according to an embodiment of the present invention. Basically, one document to be provided is encrypted with a predetermined common encryption key by this creation method. At the same time, the common decryption key corresponding to the common encryption key is encrypted using the encryption key set for each user. The encrypted document and each common decryption key are collected and stored in one data file.
[0017]
In FIG. 1, the encrypted file generation apparatus 10 can be realized by a computer operated by a file manager and a program operated on the computer, and as a functional configuration thereof, a key encryption unit 11, a key setting unit 12, A key / key data writing unit 13, a block size calculation unit 14, a document encryption unit 15, a document writing unit 16, and a data storage unit 17 are provided.
[0018]
The key encryption unit 11 encrypts input data by a predetermined algorithm using the encryption key KE set by the key setting unit 12. The data input to the key encryption unit 11 is the confirmation code M and the common decryption key KY. The key encryption unit 11 encrypts the confirmation code M to generate an encrypted confirmation code M ′, and the common decryption key KY. Is encrypted to generate an encrypted common decryption key KY ′. Here, the confirmation code M is used to determine whether or not the user who wants to view the document P has the authority to use the common decryption key KY. The confirmation code M may be any character string, symbol or other identifier, but a hash value or other message digest generated based on the document P may be used as the confirmation code M. A method for determining the viewing authority using the confirmation code M will be described later. The common decryption key KY corresponds to the common encryption key KX used for encrypting the document P to be browsed, and is a key for correctly decrypting the document P encrypted with the common encryption key KX. It is.
[0019]
The key setting unit 12 is for setting the encryption key KE used in the key encryption unit 11. In the example shown in the figure, the key setting unit 12 has encryption keys KEA, KDA, KDB, and KDC corresponding to the decryption keys KDA, KDB, and KDC distributed in advance to users A, B, and C who have the viewing authority for the document P to be encrypted. KEB and KEC are sequentially set as keys used in the key encryption unit 11. Thereby, the key encryption unit 11 generates the encryption confirmation code MA ′ and the encrypted common decryption key KYA ′ encrypted with the encryption key KEA as the data for the user A, and the encryption is performed as the data for the user B. An encryption confirmation code MB ′ encrypted with the key KEB and an encryption common decryption key KYB ′ are generated, and the encryption confirmation code MC ′ encrypted with the encryption key KEC and the encryption common are generated as data for the user C. A decryption key KYC ′ is generated.
[0020]
The key data writing unit 13 arranges the encryption confirmation code M ′ generated by the key encryption unit 11, the encrypted common decryption key KY ′, and their block size data S described later on the main memory 18. . As shown in the figure, each of the above data is collected for each user and sequentially mapped onto the main memory (hereinafter, these data are referred to as key data as necessary). That is, the block size data SA, the encryption confirmation code MA ′, and the encrypted common decryption key KYA ′ are successively arranged on the main memory 18 as the key data for the user A, and subsequently the key for the user B. As data, block size data SB, encryption confirmation code MB ′ and encrypted common decryption key KYB ′ are arranged in succession, and subsequently, block size data SC and encryption confirmation code MC ′ as key data for user C. The encrypted common decryption key KYC ′ is continuously arranged.
[0021]
The block size calculation unit 14 sums up the encryption confirmation code M ′ and the encryption common decryption key KY ′ input to the key data writing unit 13 for each output of the key encryption unit 11 using the encryption keys KEA to KEC. The number of bytes is calculated, and the block size data S storing the number of bytes is output to the key data writing unit 13. In this embodiment, three block size data SA, SB and SC are generated for each user A, B and C. The block size data SA to SC generated as described above are arranged on the main memory 18 by the key data writing unit 13 together with the encryption confirmation code M ′ and the encryption common decryption key KY ′. The block size calculation unit 14 also calculates the total number of bytes of an encrypted document code N ′ and ciphertext C, which will be described later, and outputs the block size data SP storing the number of bytes to the key data writing unit 13. The generated block size data SP is arranged in an area following the data written by the key data writing unit 13 on the main memory 18 together with the encrypted document code N ′ and the ciphertext C by the document writing unit 16 described later. Is done.
[0022]
The document encryption unit 15 encrypts input data by a predetermined algorithm using the common encryption key KX. Data input to the document encryption unit 15 is a document code N and a document P to be browsed. The document encryption unit 15 encrypts the document code N to generate an encrypted document code N ′, and the document P Is encrypted to generate a ciphertext C. Here, the document code N is for determining whether or not the user who wants to browse the document P has the viewing authority for the document. The document code N can be composed of an arbitrary character string, symbol, or other identifier as in the case of the confirmation code M.
[0023]
The document writing unit 16 stores the encrypted document code N ′ generated by the document encryption unit 15, the ciphertext C, and block size data SP described later (hereinafter referred to as document data as necessary) in the main memory 18. It is to be placed on top. The document data is sequentially mapped onto the main memory following the key data written by the previous key data writing unit 13. That is, on the main memory 18, as shown in the figure, the block size data SP, the encrypted document code N ', and the ciphertext C are sequentially arranged following the encrypted common decryption key KYC' for the user C. Is done. The block size data SP is generated by the block size calculation unit 14 described above.
[0024]
The data storage unit 17 stores the data arranged on the main memory 18, that is, the block size data SA to SC written by the key data writing unit 13, the encryption confirmation codes MA ′ to MC ′, and the encrypted common decryption key KYA. '˜KYC' and the block size data SP, encrypted document code N ′ and ciphertext C written by the document writing unit 16 are stored as one data file F on the hard disk of the server in the order of the arrangement. Note that the key data written by the key writing unit 13 and the document data written by the document writing unit 16 may be stored in separate files. In this case, the data file storing the key data includes link information to the data file storing the corresponding document data.
[0025]
FIG. 2 is a flowchart showing an encryption file generation procedure in the system. The encryption file generation procedure will be described below with reference to FIG. 1 and FIG. When the encryption file generation program is started on the computer operated by the file manager, the key setting unit 12 sets the encryption key KEA for the user A that provides the document P in the key encryption unit 11 (201). The key encryption unit 11 encrypts a predetermined confirmation code M using the encryption key KEA, and generates an encryption confirmation code MA ′ (202). Following this, the key encryption unit 11 encrypts the common decryption key KY using the same encryption key KEA, and generates an encrypted common decryption key KYA ′ (203).
[0026]
Next, the block size calculation unit 14 calculates the total number of bytes of the generated encryption confirmation code MA ′ and the encrypted common decryption key KYA ′, and generates block size data SA storing the number of bytes ( 204). The key data writing unit 13 writes the block size data SA, the encryption confirmation code MA ′, and the encrypted common decryption key KYA ′ in a predetermined area on the main memory 18 (205).
[0027]
The processes in steps 201 to 205 are repeated by the number of target users (206). In the above example, the target users are users A to C, and the above process is repeated for user B and user C. In this case, the key setting unit 12 sets the encryption key KEB for generating the data for the user B and the encryption key KEC for generating the data for the user C, respectively. Execute the process.
[0028]
When the generation of the key data is completed by the above processing, the document encryption unit 15 is activated next. The document encryption unit 15 encrypts the document code N using the set common encryption key KX, and generates an encrypted document code N ′ (207). Subsequently, the document encryption unit 15 encrypts the document P using the common encryption key KX, and generates a ciphertext C (208).
[0029]
The block size calculation unit 14 calculates the total number of bytes of the generated encrypted document code N ′ and ciphertext C, and generates block size data SP storing the number of bytes (209). Then, the document writing unit 16 writes the block size data SP, the encrypted document code N ′, and the ciphertext C after the key data on the main memory 18 (210).
[0030]
Through these processes, the generated data is arranged on the main memory 18 as shown in FIG. Then, the data on the main memory 18 is stored on the server as one data file F by the data storage unit 17 (211). Thus, an encrypted file is generated.
[0031]
FIG. 3 is a configuration diagram of a system for browsing the document P encrypted by the system of FIG. The encrypted file browsing device 30 can be realized by a client computer operated by a user and a program operated on the client computer. As a functional configuration thereof, a file reading unit 31, a key block reading unit 32, and a key decrypting unit 33 are provided. A confirmation code determination unit 34, a document block reading unit 35, a document decryption unit 36, a key setting unit 37, a document code determination unit 38, and a document display unit 39.
[0032]
The file reading unit 31 is a function for reading a file designated by the user onto the main memory 40 of the own client, whereby the data file F stored on the server is expanded on the main memory by an arbitrary user. Is done. The key block reading unit 32 enables reading in units of blocks from the data file F expanded on the main memory 40. First, the block size data SA at the head of the data file F is read, and the value, That is, the block size register 41 holds the total number of bytes of the encryption confirmation code MA ′ and the encrypted common decryption key KYA ′ that follow. The key block reading unit 32 sequentially reads out the blocks of the encryption confirmation code M ′ and the encrypted common decryption key KY ′, and gives them to the key decryption unit 33.
[0033]
The key decryption unit 33 decrypts the encryption confirmation code M ′ to generate the confirmation code M, and decrypts the encrypted common decryption key KY ′ to generate the common decryption key KY. Here, the decryption key KD used in the key decryption unit 33 is assigned to each user (in this example, KDA, KDB, KDC for the users A, B, and C). Therefore, for example, when the confirmation code and the ciphertext are decrypted using the decryption key KDA used by the user A, the encrypted confirmation code MA ′ and the encrypted common decryption encrypted with the corresponding encryption key KEA. Only the key KYA 'is successfully decrypted.
[0034]
The confirmation code determination unit 34 determines whether or not the confirmation code M decrypted by the key decryption unit 33 is normally decrypted. The confirmation code determination unit 34 compares the decrypted confirmation code M with a preset confirmation code, and controls the reading block of the key block reading unit 32 according to the result. If the key KE that encrypts the confirmation code does not correspond to the key KD that decrypts the confirmation code, normal decryption is not performed, and the confirmation code determination unit 34 outputs a mismatch. As a result, it is determined that the ciphertext C following the confirmation code is provided to a user other than the user who intends to view it. When the confirmation code determination unit 34 determines that the decrypted confirmation code M has been successfully decrypted, the confirmation code determination unit 34 continues to the key block reading unit 32 according to the value of the block size register 41. An instruction to give the encrypted common decryption key KY ′ to the read key decryption unit 33 is given. In response to this, the key decryption unit 33 decrypts the encrypted common decryption key KY ′ to generate the original common decryption key KY. The generated common decryption key KY is set in a key setting unit 37 described later. When the confirmation code determination unit 34 determines that the decrypted confirmation code M has not been decrypted normally, the confirmation code determination unit 34 determines whether the decryption confirmation code M is normally decrypted or not according to the value of the block size register 41. The subsequent encrypted common decryption key KY ′ is skipped, and the next block, that is, the block size data SB is read.
[0035]
Upon receiving a command from the confirmation code determination unit 34, the document block reading unit 35 can read each block of document data in the data file F expanded on the main memory 40. When the confirmation code determination unit 34 outputs a coincidence signal of the confirmation code, the document block reading unit 35 reads the block size data SP, and the value, that is, the following encrypted document code N ′ and the total bytes of the ciphertext C The number is held in the block size register 42. The document block reading unit 35 sequentially reads the encrypted document code N ′ and the block of the ciphertext C and supplies them to the document decryption unit 36.
[0036]
The document decryption unit 36 decrypts the encrypted document code N ′ to generate the document code N, and decrypts the ciphertext C to generate the document P. Here, the decryption key used in the document decryption unit 36 is the common decryption key KY set in the key setting unit 37. The common decryption key KY is normally decrypted by the key decryption unit 33 and set in the key setting unit 37 when the confirmation code determination unit 34 matches the confirmation code.
[0037]
The document code determination unit 38 determines whether or not the document code N decrypted by the document decryption unit 36 is normally decrypted. The document code determination unit 38 compares the decrypted document code N with a preset document code N, and controls the reading block of the document block reading unit 35 according to the result. If the key KX for encrypting the document code and the key KY for decrypting the document code do not correspond to each other, normal decryption is not performed, and the document code determination unit 38 outputs a mismatch. As a result, it is determined that the ciphertext C following the document code is provided to a user other than the user who intends to view it. When the document code determination unit 38 determines that the decrypted document code N has been successfully decoded, the document code determination unit 38 continues to the document block reading unit 35 according to the value of the block size register 42. An instruction is given to read the ciphertext C to the document decryption unit 36. In response to this, the document decryption unit 36 decrypts the ciphertext C and generates the original document P.
[0038]
The document display unit 39 has a function of displaying the decrypted document P so that the user can view it. When the user who performs the above operation has the viewing authority for the provided document P, the document display unit 39 displays the target document on the display of the client.
[0039]
4 and 5 are flowcharts showing the browsing procedure of the encrypted file in the system. Hereinafter, a procedure for an arbitrary user B having the decryption key KDB to browse the encrypted file will be described with reference to FIGS. When the encryption file browsing program is started on the client computer operated by the user B and the data file F on the server is designated, the file reading unit 31 expands the data file F in a predetermined area of the main memory 40 of the client. (401). The block size data SA which is the first block of the data file F is read by the key block reading unit 32 (402) and stored in the block size register 41 (403). Next, the encryption confirmation code MA ′ in the next block is read and sent to the key decryption unit 33. The key decryption unit 33 decrypts the encryption confirmation code MA ′ with the decryption key KDB assigned to the user B (404).
[0040]
Next, it is determined whether the encoded confirmation code is correct by the confirmation code determination unit 34 (405). However, since this encryption confirmation code MA ′ is encrypted with the encryption key KEA for user A, it cannot be correctly decrypted with the decryption key KDB. Therefore, the process moves to step 406, and the pointer indicating the next block to be read is moved to the head address of the next block size data SB according to the value in the block size register 41 by the confirmation code determination unit 34.
[0041]
By moving the pointer, the key block reading unit 32 next reads the block size data SB (402) and stores it in the block size register 41 (403). Next, the encryption confirmation code MB ′ in the next block is read and sent to the key decryption unit 33. The key decryption unit 33 decrypts the encryption confirmation code MB ′ with the decryption key KDB assigned to the user B (404). Similar to the above process, the decrypted confirmation code is determined by the confirmation code determination unit 34 (405), but this time the encrypted confirmation code MB ′ is the user B encryption key KEB. Since it is encrypted, it is correctly decrypted with the decryption key KDB. As a result, the process proceeds to step 407.
[0042]
In step 407, the size of the encrypted common decryption key KYB 'is confirmed according to the value of the block size register 41. The key block reading unit 32 reads the encrypted common decryption key KYB ′ according to the confirmed size and sends it to the key decryption unit 33. The key decryption unit 33 decrypts the encrypted common decryption key KYB ′ with the decryption key KDB assigned to the user B (408). As a result, the common decryption key KY is normally decrypted. The decrypted common decryption key KY is set in the key setting unit 37 of the document decryption unit 36 (409).
[0043]
Next, the document block reading unit 35 reads the block size data SP in the first block of the document data (501 in FIG. 5) and stores the value in the block size register 42 (502). Next, the encrypted document code N ′ in the next block is read and sent to the document decryption unit 36. The document decrypting unit 36 decrypts the encrypted document code N ′ with the set common decryption key KY (503).
[0044]
Next, it is determined whether or not the encoded document code is correct by the document code determination unit 38 (504). If the decryption key set in the key setting unit 37 is not correct, the encrypted document code N ′ cannot be decrypted correctly. In this case, the process ends without the document P being decrypted. When the key set in the key setting unit 37 is the decryption key KY, since the encrypted document code N ′ is encrypted with the common encryption key KX, it is correctly decrypted with the decryption key KY. As a result, the process proceeds to step 505.
[0045]
In step 505, the size of the ciphertext C is confirmed according to the value of the block size register 42. The document block reading unit 35 reads the ciphertext C according to the confirmed size and sends it to the document decryption unit 36. The document decryption unit 36 decrypts the ciphertext C with the set common decryption key KY (506). As a result, the ciphertext C is normally decrypted, and the original document P is obtained. The decrypted document P is displayed on the display by the document display unit 39 so that the user B can view it.
[0046]
Similarly, the users A and C can browse the target document P by executing the program on their own clients and accessing the same data file F. On the other hand, when the user who does not have the authority to view the document P (for example, the user D who has the decryption key KDD with respect to the encryption key KED) accesses the data file F, the confirmation code in the confirmation code determination unit 34 is correct. It is determined not to be decrypted. As a result, any ciphertext cannot be browsed. In such a case, a message for a user who does not have browsing authority such as “no browsing authority” may be stored in the final block of the data file F and displayed.
[0047]
Next, another embodiment of the present invention will be described. In the present embodiment, basically, the encrypted file generation device 10 and the encrypted file browsing device 30 used in the previous embodiment are used. In the generation and browsing of the encrypted file in the present embodiment, different common keys KX and KY are used separately for different security levels (for example, officers, internal specific departments and general employees). As a result, a single data file can include a plurality of documents with the same theme but different contents (according to each security level), and only a user at the corresponding security level can view the target document. .
[0048]
FIG. 6 shows a data file F generated by the encrypted file generation device according to the present embodiment. The lower part of the data file F includes three ciphertexts C1 to C3 having different contents, and these are encrypted with different common encryption keys KX1 to KX3. That is, the ciphertext C1 encrypts the document P1 provided to the users A and B belonging to the first security level (for example, officer level; hereinafter, level 1) with the common encryption key KX1 assigned to the level. The ciphertext C2 is assigned to the document P2 provided to the users C and D belonging to the second security level (for example, the specific department level; hereinafter, level 2). The ciphertext C3 is a document provided to users E, F, and G belonging to the third security level (for example, general employee level; hereinafter, level 3). P3 is encrypted with the common encryption key KX3 assigned to the level. A document code N encrypted with a corresponding common encryption key, that is, encrypted document codes N1 ′ to N3 ′ and block size data SP1 to SP3 are stored above each ciphertext.
[0049]
At the top of the data file F, there are seven blocks to be accessed by each of the users A to G. In each block, the common decryption keys KY1 to KY3 assigned to the level to which each user belongs are assigned to that user. The one encrypted with the assigned encryption keys KEA to KEG is stored. For example, since user A belongs to level 1, the corresponding level common decryption key KY1 is encrypted with the encryption key KEA, that is, the encrypted common key KY1A 'is stored for user A. . Since user C belongs to level 2, the corresponding level common decryption key KY2 is encrypted with the encryption key KEC, that is, the encrypted common decryption key KY2C ′ is stored for user C. The The confirmation code M encrypted with the corresponding common encryption key, that is, the encryption confirmation codes M1 ′ to M3 ′ and the block size data SA to SG are stored above each encrypted common decryption key.
[0050]
The generated data file F can be browsed by the encrypted file browsing apparatus 30 shown in the previous embodiment. That is, according to the procedures of FIGS. 4 and 5, each user A to G can correctly decrypt the common decryption keys KY1 to KY3 corresponding to the security level by using their own decryption keys KDA to KDG, respectively. Documents P1 to P3 provided respectively using the decrypted common decryption keys KY1 to KY3 can be correctly decrypted and viewed. On the other hand, the user cannot correctly decrypt a document provided to a user of another security level (for example, the document C1 for the user E at the level 3), so that the security is guaranteed.
[0051]
The embodiment of the present invention has been described with reference to the drawings. However, the present invention is not limited to the matters shown in the above-described embodiments, and it is obvious that changes, improvements, and the like can be made based on the description of the scope of claims. The encryption algorithm that can be used in the present invention is not particularly limited, and various encryption methods (whether it is a symmetric key encryption method, an asymmetric key encryption method, a stream encryption method, or a block encryption method) Etc.) can be used.
[0052]
Although the method of the present invention is preferably used in a computer network environment, the network may be local (for example, an in-house LAN) or wide area (for example, the Internet). The information to be encrypted is not limited to a document, but may be an image, sound, or a mixture of these and a document, and a plurality of related information may be stored as one data file. In addition, this method can be used for distribution of a product catalog to a specific user, and in this case, the product key and other confidential information are delivered together with the distribution of the product catalog using a different encryption key for each specific user. be able to.
[0053]
The method of the present invention can be basically realized by a computer and a program operated on the computer. However, the method of the present invention can be applied to a program (for example, a WWW browser on the Internet) that serves as an interface for displaying information transmitted and received between networks. You may implement | achieve in the form (what is called a plug-in) which adds a predetermined function.
[0054]
In the above embodiment, an example is shown in which key data is arranged in the upper part of the data file to be created and document data is arranged in the lower part. However, when the document data is short, it may be recorded in the key data for each user. Furthermore, for a specific user, the block in which the encrypted common decryption key is arranged is arranged such that document data encrypted using an encryption key (for example, KEA) assigned to the user is arranged. You may do it. In this case, in order to identify whether the data stored in the block is the encryption common decryption key or the document data, two types of confirmation codes are prepared, and the confirmation code determination unit identifies them. It ’s fine.
[0055]
【The invention's effect】
As described above, according to the present invention, files of the same or related information provided to a plurality of users can be combined into one in an encrypted state, and there is an advantage that management of stored information is easy. In this case, it is easy to manage keys for encryption and decryption on the user side and the administrator side.
[0056]
Furthermore, since it is sufficient to store one document encrypted with the common encryption key in the data file, the file size can be minimized.
[0057]
In addition, it is determined whether or not the user has the authority to view the information easily and quickly by determining whether the information to be browsed is correctly decoded using the determination code. it can.
[Brief description of the drawings]
FIG. 1 is a system configuration diagram for realizing an encrypted file creation method according to an embodiment of the present invention.
FIG. 2 is a flowchart showing a procedure for generating an encrypted file in the system of FIG. 1;
FIG. 3 is a system configuration diagram for browsing a document encrypted by the system of FIG. 1;
4 is a flowchart showing a procedure for browsing an encrypted file in the system of FIG.
FIG. 5 is a flowchart showing a procedure for browsing an encrypted file in the system of FIG. 3;
FIG. 6 is a diagram showing a data file generated by an encrypted file generation device according to another embodiment of the present invention.
FIG. 7 is a system configuration diagram for realizing a conventional method for creating an encrypted file.
FIG. 8 is a system configuration diagram for realizing a conventional encrypted file browsing method;
[Explanation of symbols]
KX common encryption key
KYA'-KYC 'encryption common decryption key
KDA to KDC decryption key
KEA to KEC encryption key
P Document
C Ciphertext
M confirmation code
MA 'to MC' encryption confirmation code
N Document code
N 'Encrypted document code
SA to SC block size data
SP block size data
F data file
10 Encrypted file generator
11 Key encryption part
12 Key setting part
13 Key data writing part
14 Block size calculator
15 Document encryption part
16 Document writer
17 Data storage
18 Main memory
30 Encrypted file browsing device
31 File reading part
32 Key block reading unit
33 Key decryption unit
34 Confirmation code judgment part
35 Document block reading section
36 Document decryption unit
37 Key setting part
38 Document code determination unit
39 Document display area
40 Main memory
41, 42 Block size register

Claims (2)

A first encryption means for encrypting input data with a common encryption key; a second encryption means for encrypting input data with a plurality of different encryption keys; and an encrypted encryption A method for generating a data file used by a plurality of viewers having a decryption key corresponding to a plurality of different encryption keys in an encrypted file generation device comprising at least a writing means for writing encrypted data to a main storage means Because
Either the first encryption means encrypts the browsed information using the common encryption key or the second encryption means encrypts using the plurality of different encryption keys. Steps to be selectively performed according to the operation of
A procedure for generating a plurality of encrypted determination codes by respectively encrypting the predetermined determination codes input to the second encryption means with the plurality of encryption keys;
A procedure for generating a plurality of encrypted common decryption keys by encrypting a common decryption key corresponding to the common encryption key with the plurality of different encryption keys when the browsed information is encrypted with the predetermined common encryption key And a procedure for writing the encrypted browsing information in the main storage means by the writing means, and the encryption determination code encrypted by the writing means with the same key as each of the encrypted common decryption keys. And writing to the main memory means after attaching,
When the browsed information is encrypted with an encryption key corresponding to the different decryption key, the encryption determination code encrypted with the same key as each of the encrypted browsed information is associated with the writing means. Including the procedure of writing to the main memory means after attaching
When the encrypted browsing information stored in the main storage means, the encryption determination code, and the common encryption key are used, the encrypted common decryption key is combined to form one data file. There,
As the determination code, a determination code when the browsed information is encrypted with the predetermined common encryption key and a determination code when the browsed information is encrypted with an encryption key corresponding to the different decryption key A method for generating an encrypted file, characterized in that two types of determination codes are prepared. A main storage means, a reading means for reading out information encrypted from the main storage means, a first decryption means for decrypting information encrypted with the common encryption key, and the plurality of encryption keys. An encrypted file browsing device comprising at least a second decryption unit for decrypting encrypted information, a determination unit for determining whether the determination code is correct, and a display unit. A method of browsing an encrypted file generated by the described method,
The procedure for loading the data file onto the main memory, the procedure for reading the encryption determination code in the data file by the reading means, and the second decryption means using the decryption key possessed by the viewer A procedure for sequentially decrypting the encryption determination code and whether or not the decrypted determination code has been correctly decrypted into one of the two types of determination codes before encryption is sequentially determined by the determination means. The procedure and the second decryption means decrypt the encrypted common decryption key using the decryption key possessed by the viewer, or use the decryption key possessed by the browse user with the encrypted browsed information A first step using a procedure for selectively executing one of the decryption and a decryption code that is decrypted when the encrypted common decryption key is decrypted. Decrypt encrypted browsing information with the decryption means That procedure and, browsing method of the encrypted file, characterized by comprising, a step of displaying on the display means to be viewed decoded information.

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