JP2006237908A - Encryption and decryption method of file, and key information extract method and apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an encryption and decryption technology of a log file which can simply and securely cope with storage, movement and data browsing of the log file at a low cost and can place a limit on a range of a browseable log by a browsing person. <P>SOLUTION: The technology is an encryption method of a plurality of files, attaches a shared key encrypted by a public key to a log file encrypted by a shared key, and attaches part of elements for extracting a shared key group for log files connected backward and forward to the log file and encrypted by a shared key, and an element required for extracting the shared key group of the log files connected backward and forward to the log file encrypted by the public key together with the element above to the log file. In the case of providing a single log file, the log file shared key is provided from the single log file by using the private key. In the case of providing a file consecutive to the log file, part of elements encrypted by the public key for the log files consecutive forward and backward is provided together with the shared key of the log file. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an encryption and decryption technique for protecting secrets such as log files.

  Log data that records the usage status of the system is stored as a plurality of files separated by a certain period or size. Conventionally, log data is often stored in plain text and often copied to a DVD or tape medium as it is. However, the importance of logs has increased, and there are occasions where they are subject to audits or submitted as evidence, rather than simply being stored. As for storage, it may be stored in another physically safe place. For this reason, the medium containing the log data is moved, and encryption of the log file is required from the risk of leakage due to loss.

  In addition, there are cases where log data usage methods increase, and log files that can be browsed differ depending on the viewer. For example, a log file manager who can view all log files, an auditor who audits a plurality of log file groups in a certain period, and a partner who has submitted some continuous log files as evidence. Also, due to the nature of log files, it is often the case that consecutive log files are viewed in normal or reverse order, and those who can view a certain number of continuous log files can view all log files. There is also a feature that there are many.

  Considering the above points, it is necessary to encrypt the log file so that the range of logs that can be viewed by the viewer is determined.

Regarding the encryption method of log data, several methods using an existing encryption method can be considered. The first is a method in which all log files are simply encrypted and stored with the same key, and decrypted and re-encrypted for the viewer when handed over to the viewer. Second, if the log data and the log file are read as an image and a part of the image, they are encrypted and stored using different keys as in Patent Document 1 below, and the key group passed by the viewer is changed. There is also. Third, in order to solve the problem of key storage and recovery, a file is encrypted with a common key and the common key is encrypted with a public key as described in Patent Document 2 below. There is also a way to make it together with the digitized file.
JP 3-40689 JP-A-7-56507

  However, the conventional method has various problems. The first method of decrypting and encrypting when handing over to a viewer is high in cost, and the cost increases in proportion to the amount of files to be passed. Also, in the second method, using a separate common key for each, and changing the key passed by the other party, it is necessary to securely store the correspondence between the key and ciphertext, and when the amount of files to be passed increases The number of keys to be handed out is cumbersome. Finally, as with the third method, the method of storing a common key encrypted with a public key together with individual files eliminates the complexity of key management, but if you pass a secret key to all files Since it becomes possible to browse the private key, it is impossible to pass the secret key, and as long as the private key cannot be passed, it is necessary to pass the same number of common keys together with the encrypted file. If so, it will be cumbersome with more keys to pass.

  Thus, the conventional method can deal with storage and movement of log files and browsing of all data. However, in log data submission and auditing, it is assumed that a plurality of continuous files are passed. In such a case, handling is difficult or complicated.

  SUMMARY OF THE INVENTION An object of the present invention is a log file encryption / decryption technique that can deal with storage, movement, and data browsing of a log file safely and easily at low cost, and can limit the range of logs that can be browsed by a viewer. Is to provide.

  In order to solve the above problems, in the present invention, a common key encrypted with a public key is attached to a file encrypted with a common key, and a partial element for extracting a common key group of consecutive files Attached are the ones encrypted with the common key and the ones encrypted with the public key for extracting the common key group of the consecutive files in combination with the previous element. When a single file is submitted, the file common key is passed from the single file using a secret key. When passing a continuous file from a certain file, a part of the element for completely extracting the common key group of the preceding and following files together with the previous element is passed along with the common key of the file.

  According to the present invention, it is possible to decrypt a continuous log file without passing a secret key without taking the trouble of decryption and re-encryption, and without preparing and passing correspondence relationships between a large number of common key groups and files. It is possible to pass information that can be stored, and log files can be securely stored by encryption.

  Hereinafter, an embodiment for carrying out the present invention will be specifically described with reference to the drawings.

  FIG. 1 shows the overall configuration of a system according to an embodiment to which the present invention is applied. This system includes three terminals: a log file encryption terminal 110, a decryption key generation terminal 120, and a log file decryption terminal 130. In the log file encryption terminal 110, a log file encryption program 111 and a public key PK112 are arranged. The main processing in the log file encryption terminal 110 is to encrypt a given plain text log file and encrypt key information using the public key PK112. In the decryption key generation terminal 120, a decryption key generation program 121 and a secret key SK122 corresponding to the public key PK112 are arranged. The main process of the decryption key generation terminal 120 is that when one encrypted log file and a range to be decrypted before and after the encrypted log file are given, the key of the encrypted log file and the file decryption within the range to be decrypted The key information necessary for this is output. A log file decoding program 131 is arranged in the log file decoding terminal 130. The main processing of this terminal is to decrypt the log file specified by the file identifier when given the encrypted log file group, the output of the decryption key generation terminal 120, and the file identifier corresponding to the key. In other words, the log file in the range specified by the decryption key generation terminal 120 is decrypted according to the request of the terminal user.

  This system is used as follows, for example. First, the person in charge of encryption encrypts sequentially generated plain text log files using the log file encryption terminal 110. The detailed structure of the encrypted log file will be described with reference to FIG. 2. However, since the encrypted file cannot be decrypted alone, the encrypted log file can be safely stored. When making a predetermined reference refer to a log file, the administrator of the encrypted log file uses the decryption key generation terminal 120 to generate and pass a key element information file to be passed to the reference. Specifically, when the decryption key generation terminal 120 designates one log file to be referred to by the referrer and designates the range of how many log files from before and after that log file are designated, the key element Since the information file is generated and output, the encrypted log file to be referred to as the key element information file is passed to the reference person. In the log file decryption terminal 130, the referrer decrypts the log file using the passed key element information file information, and refers to the contents.

Next, before describing the detailed configuration and operation of the present embodiment, a description will be given of a common key used when actually decrypting a log file. In the system of the present embodiment, there are two types of elements, a key difference element α and a key element β. These elements are data for calculating a common key. There are 2m key difference elements α for each log file to be encrypted. There are 2m-1 key elements β for each log file to be encrypted. In the following, the x-th key difference element capable of generating a common key for encrypting and decrypting the log file n (the n-th log file) is expressed as α _{n, x} and the x-th key element is β Expressed as _{n, x} . α and β are significant when x is 0 or more and 2 m or less, and α and β when this range is exceeded are calculated as 0. Similarly, α and β are significant when n is a natural number, and α and β are calculated as 0 when they are outside of them. As will be described with reference to FIG. 2, among the 2m-1 key elements β corresponding to one log file, β _{n, m} is a common key itself for encrypting and decrypting the log file n.

The key difference element α and the key element β have the following expressions (1) and (2).
β _{i, j} + α _{i, j} = β _{i, j + 1} (0 ≦ j ≦ 2m-1) Equation (1)
β _{i, 0} = β _{i, 2m} = 0 Equation (2)

Due to the above characteristics, the key element β _{n, m serving as} the common key of the log file n is the sum of the key difference elements α _{n, 0} ... Α _{n, m−1} or the key difference element −α _{n, m + 1} . -α _{n, 2m} can be calculated with the total sum or a part of it replaced with the key element β.

FIG. 2 shows a configuration of an encryption log file 200 with key information that is output as a result of encrypting the nth log file. The encryption log file with key information 200 is a key difference element that is a set of encrypted log file data 210 obtained by encrypting the _nth log file 211 with the common key β _{n, m} and a key difference element α as shown in the figure. Encrypted key difference element data 220 obtained by encrypting information 221 with a common key β _{n, m} and encrypted key element obtained by encrypting key element information 231 that is a set of key elements β as shown in the figure with a public key PK Three of the data 230 are combined.

The encrypted log file data 210 included in the nth encrypted file 200 can be decrypted by the following method.
(1) If the common key β _{n, m} is known, the common key β _{n, m} can be used for decryption.
(2) If the secret key SK is known without knowing the common key β _{n, m} , the encrypted key element data 230 is decrypted with the secret key SK and decrypted with the obtained common key β _{n, m} Can be
(3) Instead of directly obtaining the common key β _{n, m} from the n-th encrypted file 200, the encryption included in _{the m} encrypted files before the encrypted file or the m encrypted files after the encrypted file And the common key β _{n, m} is calculated by calculating the sum of α _{n, 0} … α _{n, m-1} or the sum of -α _{n, m} … -α _{n, 2m-1} You can ask for it. This is because β _{n, m} = α _{n, 0} + α _{n, 1} + ... + α _{n, m-1} = -α _{n, m} -α _{n, m + 1} -...- α _{n, 2m-1} . α _{n, 0} is a key difference element included in the m-th encryption file after this encryption file, α _{n, 1} is a key difference element included in the m-1 encryption file after this encryption file _{,. , m−1} is a key difference element included in the next encrypted file after this encrypted file. Similarly, -α _{n, m} is a key difference element included in the previous encryption file of this encryption file, and -α _{n, m + 1} is a key difference element included in the encryption file two times before this encryption file. ,..., -Α _{n, 2m-1} are key difference elements included in the m-th preceding encryption file.
(4) In the calculation of (3) above, the common key β obtained by decrypting the encrypted key element data with the secret key SK can be used for a part of the calculation. For example, β _{n, m} = β _{n, m-1} + α _{n, m-1} .

As described above, in the system of the present embodiment, when the reference person wants to refer only to the n-th log file and its p-th to q-th (that is, np-th, n-p + 1th,. nth, n + 1th,..., n + qth), β _{np, mp} , β _{n-p + 1, m-p + 1} ,. It is only necessary to pass _{n, m} , β _{n + 1, m + 1} ,..., β _{n + p, m + q} to the reference (the secret key SK is not passed to the reference). In this case, the referrer can decrypt the log file by the following procedure.
(1-1) Since β _{n, m} is held, the referrer can decrypt the n-th log file.
(1-2) Furthermore, since carrying _{β n-1, m-1} , the reference person, beta _n-1 by using the n-th α _{n-1, m-1} in encryption log _{file, m- 1} + α _{n−1, m−1} = β _{n−1, m} can be obtained, and thus the (n−1) th log file can be decrypted.
(1-3) Furthermore, since carrying _{β n-2, m-2} , the reference person, using the n-th alpha _n-2 in the cryptographic log _{file, m-2 β n-2} , m- ₂ + α _{n-2, m-2} = β _{n-2, m-1} , and β _n- using α _{n-2, m-1} in the (n-1) th encrypted log file _{2, m-1} + α _{n-2, m-1} = β _{n-2, m} can be obtained, whereby the (n-2) th log file can be decrypted.
(1-4) Similarly, the log file can be decrypted while returning one by one from the nth. After decrypting the npth log file, even if you try to decrypt the np-1th log file _{, the referrer} does not have β _{np-1, mp-1} , so decrypt the np-1th log file Can not.
(1-5) However, if p + q + 1 is greater than or equal to m, that is, if the reference is allowed to decrypt m or more consecutive log files, the key difference element α _{np in the} np-th encrypted file _{-1, m-1} , key difference element α _{np-1, m-2 in} the n-p + _1st encryption file, key difference element α _{np-1, m in} the n-p + _2th encryption file _-3 , ..., n-p + m-1 can obtain all the key difference elements α _np-1,0 in the n th encrypted file, α _{np-1, m-1} + α _{np-1, m Since −2} +... + Α _np−1,0 = β _{np−1, m} can be obtained, the np−1 log file can be decrypted. Similarly, all log files up to the first can be decrypted by returning to np-2 and np-3.

In the above (1-1) to (1-5), the procedure of decoding while returning one by one from the nth log file has been described. Similarly, it is possible to decrypt the next file while proceeding one by one from the nth log file by the following procedure.
(2-1) Since β _{n, m} is held, the referrer can decrypt the nth log file.
(2-2) Furthermore, since carrying β _{n + 1, m + 1,} the reference person, using a-.alpha. _{n + 1, m} in the n-th cipher log file β _{n + 1, m + 1} -α _{n + 1, m} = β _{n + 1, m} can be obtained, whereby the (n + 1) th log file can be decrypted.
(2-3) Furthermore, since β _{n + 2, m + 2} is held, the referrer uses β- _{n + 2, m + 1} in the n-th encrypted log file to obtain β _{n + 2, m +2} -α _{n + 2, m + 1} = β _{n + 2, m + 1} and β _{n + 2} using α _{n + 2, m} in the (n + 1) th encrypted log file _{, m + 1} -α _{n + 2, m} = β _{n + 2, m} , thereby decoding the (n + 2) th log file.
(2-4) Similarly, the log file can be decrypted while proceeding one by one from the nth. After decrypting the n + qth log file, even if you try to decrypt the n + q + 1st log file, the referrer does not have β _{n + q + 1, m + q + 1} , so n Cannot decrypt + q + 1st log file.
(2-5) However, if p + q + 1 is greater than or equal to m, that is, if the reference is allowed to decrypt m or more consecutive log files, the key difference element in the n + q-th encrypted file -α _{n + q + 1, m} , key difference element in n + q-1st cipher file -α _{n + q + 1, m + 1} , key difference element in n + q-2 th cipher file -α _{n + q + 1, m + 2} , ..., all the key difference elements -α _{n + q + 1,2m-1} in the n + q-m + 1-th encrypted file can be acquired,- α _{n + q + 1, m} -α _{n + q + 1, m + 1-} … -α _{n + q + 1,2m-1} = β _{n + q + 1, m} q + 1 log file can be decrypted. In the same manner, the process proceeds further to n + q + 2 and n + q + 3, and all log files can be decrypted.

  As can be seen from the above, m is a threshold value indicating how many or more consecutive log files are allowed to be decoded if decoding is allowed. A specific value of m is determined in advance.

  FIG. 3 shows the configuration of the log file encryption program 111. To be precise, the configuration is realized when the log file encryption program 111 is executed by the log file encryption terminal 110, but it is simply referred to as the configuration of the program. The same applies to FIGS. 9 and 11 described later. The log file encryption program 111 includes a log file input unit 301, a random number generation unit 302, a previous key element information storage unit 303, a key element information storage unit 304, a next key element information storage unit 305, and a key difference element information storage unit. 306, a log file encryption processing unit 307, a key element information encryption processing unit 308, a key difference element information encryption processing unit 309, a data combination unit 310, and an encryption log file output unit 311 with key information.

  The log file input unit 301 performs a process of inputting a log file to be encrypted. The random number generation unit 302 generates a random number used for key element information.

  The previous key element information storage unit 303 stores the key element information 231 including the common key used when encrypting the n-1st log file at the time of encrypting the nth log file. It is. The key element information storage unit 304 stores key element information 231 including a common key used when encrypting the nth log file at the time of encrypting the nth log file. The next key element information storage unit 305 stores key element information 231 including a common key used when encrypting the (n + 1) th log file at the time of encrypting the nth log file. It is. The key difference element information storage unit 306 stores the key difference element information 221 for the nth log file at the time of encrypting the nth log file.

  The log file encryption processing unit 307 encrypts the nth log file using the common key included in the key element information storage unit 304, and generates encrypted log file data 210. The key element information encryption processing unit 308 encrypts key element information stored in the key element information storage unit 304 using the secret key PK112, and generates encrypted key element data 230. The key difference element information encryption processing unit 309 encrypts the key difference element information stored in the key difference element information storage unit 306 and creates encrypted key difference element data 220. The data combining unit 310 combines the output data of the log file encryption processing unit 307, the key element information encryption processing unit 308, and the key difference element information encryption processing unit 309 into one file (FIG. 2). The encryption log file with key information output unit 311 outputs the file generated by the data combining unit 310.

  FIG. 4 is a flowchart showing a processing procedure by the log file encryption program 111. First, a plain text log file is input to the log file input unit 301 (step 401). At this time, whether the input log file is the first log file is input together. Next, it is determined whether or not the input log file is the first log file (step 402). If it is the first log file (that is, n = 1), the initial key element information is generated using the random number generation unit 302, stored in the key element information storage unit 304, and the previous key element information storage unit 303 further The information to be stored is filled with 0 (step 403).

  FIG. 5 shows details of information stored by the key element information storage unit 304. The key element information storage unit 304 includes an n-th log file encryption key 501, which is a key used for encrypting the n-th log file, an n-th and subsequent log file encryption key element group 502, and the n-th and previous log files. Log file encryption key element group 503. In step 403 described above, since the first log file is not encrypted, the log file encryption key 501 and the log file encryption key element group 502 are filled with the random number generated by the random number generation unit 302. Otherwise, fill with 0.

  FIG. 6 shows details of information stored by the previous key element information storage unit 303. The previous key element information storage unit 303 includes an (n-1) th log file encryption key 601 and a (n-1) th log file encryption key element group, which are keys used for encrypting the (n-1) th log file. 602 and the log file encryption key element group 603 before the (n-1) th. In step 403 described above, before the first log file is encrypted and there is no corresponding information, all values are filled with 0 as an initial setting. Information stored by the previous key element information storage unit 303 other than step 403 will be described later.

Returning to FIG. 4, after the initial key element is generated in step 403 or when it is determined in step 402 that it is not the first log file, the nth log file encryption key β _{n, m} 501 exists. Accordingly, the log file encryption processing unit 307 encrypts the input _n-th log file with the n-th log file encryption key β _{n, m} 501 to generate encrypted log file data 210 (step 404).

  Next, next key element information is generated using the random number generation unit 302 and stored in the next key element information storage unit 305 (step 405).

  FIG. 7 shows details of information stored by the next key element information storage unit 305. The next key element information storage unit 305 includes an (n + 1) th log file encryption key 701, which is a key used for encrypting the (n + 1) th log file, and (n + 1) th and subsequent log file encryption key element groups. 702 and the log file encryption key element group 703 before the (n + 1) th. The configuration of the next key element information storage unit 305 is the same as that of the key element information storage unit 304 shown in FIG. 5, but includes the encryption of the next log file, such as including the (n + 1) th log file encryption key. Stores key element information for occasional use.

In step 405 described above, in β _{x, y} in the next key element information storage unit 305, the part where x is 0 or less is a key element that does not have a corresponding log file, so it is _padded with 0. Set a random number. For example, if the first log file is encrypted in step 404, the (n + 1) th log file encryption key 701, the (n + 1) th and subsequent log file encryption key elements 702, and n + The part of the key element β _{n, m−1} in the log file encryption key element group 703 before the first one is filled with the random number generated by the random number generation unit 302, and the others are filled with 0.

  Next, key difference element information 221 is generated from information stored in the previous key element information storage unit 303, key element information storage unit 304, and next key element information storage unit 305, and stored in the key difference element information storage unit 306. (Step 406).

FIG. 8 shows details of information stored by the key difference element information storage unit 306. The key difference element α _{nm, 0} 801 is the key element β _{nm, 1} itself stored in the previous key element information storage unit 303 (FIG. 6). The key difference element −α _{n + m, 2m−1} 802 is the key element β _{n + m, 2m−1} itself stored in the next key element information storage unit 305 (FIG. 7). As shown in FIG. 8, the key difference elements α _{n-m + 1,1 to} α _{n-1, m-1} 803 are different from the information stored in the previous key element information storage unit 303 and the key element information storage unit 304. Is calculated and generated. The key difference elements -α _{n + 1, m} to -α _{n + m-1,2m-2} 804 are information stored by the _next key element information storage unit 305 and the key element information storage unit 304 as shown in FIG. The difference is calculated and generated.

  After the key difference element information 221 is generated in step 406 and stored in the key difference element information storage unit 306, the information stored in the key element information storage unit 304 is encrypted as the key element information 231 using the public key PK112, Encrypted key element data 230 is generated (step 407). Next, the key difference element information 221 stored in the key difference element information storage unit 306 is encrypted with the nth log file encryption key 501 stored in the key element information storage unit 304, and the encrypted key difference element data 220 is stored. Is generated (step 408).

  Next, the information stored in the key element information storage unit 304 is copied to the previous key element information storage unit 303, and the information stored in the next key element information storage unit 305 is copied to the key element information storage unit 304 (step 409). . This prepares for the input of the next log file. Next, the encrypted log file data 210 generated in step 404, the encrypted key element data 230 generated in step 407, and the encrypted key difference element data 220 generated in step 408 are combined to generate an encrypted file 200. (Step 410). Finally, the file generated in step 410 is output (step 411).

  Thus, the file 200 in which the three data shown in FIG. 2 are combined is generated.

  FIG. 9 shows the configuration of the decryption key generation program 121. The decryption key generation program 121 includes an encryption log file / key range input unit 901, an encryption log file separation unit 902, a key element information decryption processing unit 903, a key element information storage unit 904, an out-of-range information deletion processing unit 905, It has a key element information combining unit 906 and a key element information file output unit 907.

  The encryption log file / key range input unit 901 inputs one encryption log file with key information 200 for which a decryption key is to be generated and a range of encryption log files with key information that are to be continuously decrypted. The encryption log file separation unit 902 extracts the encrypted key element data 230 from the input encryption log file with key information 200. The key element information decryption processing unit 903 decrypts the encrypted key element data 230 using the secret key SK122, and generates key element information 231. The key element information storage unit 904 stores the key element information 231 generated by the key element information decryption processing unit 903. The out-of-range information deletion processing unit 905 deletes key elements outside the range specified in the key element information 231 with respect to the range input by the encryption log file / key range input unit 901. The key element information combining unit 906 combines the key element information 231 obtained as a result of deletion by the out-of-range information deletion processing unit 905 as a key element information file. The key element information file output unit 907 outputs the key element information file generated by the key element information combining unit 906.

  FIG. 10 is a flowchart showing a processing procedure by the decryption key generation program 121. First, the encryption log file / key range input unit 901 inputs one encryption log file 200 with key information for which a decryption key is to be generated and a range of encryption log files with key information to be decrypted continuously before and after that file. (Step 1001). Here, the range is 0 for the input encrypted log file with key information, minus the old direction, plus the new direction, for example, if you want to decrypt the log file three to four after the previous, It shall be entered in the format (-4, 3). If x is larger than 0 or y is smaller than 0 in input (x, y), it is input again as an error.

  Next, it is checked whether or not the range input in step 1001 is m or more log files, and if m or more, the process proceeds to step 1003, and if less than m, the process proceeds to step 1004 (step 1002). For example, if m is 8 or less and the range is (−4, 3), it means that decoding of 8 consecutive log files is allowed, and the process proceeds to step 1003. If it is determined in step 1002 that m or more ranges have been designated, it is confirmed with the input person whether a key that can decrypt all log files can be output (step 1003). If not, the range is input again at step 1001. Otherwise, go to step 1004. As described in FIG. 2, a person who can decrypt m or more consecutive log files can decrypt all log files beyond that range. I have confirmed.

  Next, the encrypted key element data 230 is extracted from the input encryption log file with key information 200 using the encryption log file separation unit 902 (step 1004). Next, the key element information decryption processing unit 903 decrypts the encrypted key element data 230 using the secret key SK122, generates key element information 231 and stores the key element information 231 in the key element information storage unit 904. (Step 1005). Details of the information held by the key element information storage unit 904 are the same as those shown in FIG.

Next, the out-of-range information deletion processing unit 905 sets the key element outside the specified range among the information in the key element information storage unit 904 to 0 (step 1006). For example, if the range is specified as (−4,3) with the nth log file set to 0, the part other than key element β _{n-4, n-4} to key element β _{n + 3, n + 3} Is 0. Next, the key element information combining unit 906 simply combines the information stored in the key element information storage unit 904 to generate a key element information file (step 1007). Finally, the key element information file generated in step 1007 is output by the key element information file output unit 907 (step 1008).

  FIG. 11 shows a schematic configuration of the log file decoding program 131. The log file decryption program 131 is roughly divided into four parts: an initial input screen processing unit 1101, a key-related information storage unit 1102, a log file information storage unit 1103, and a reference user operation screen processing unit 1104. The initial input screen processing unit 1101 performs initial input and processing such as inputting an encryption log file group with key information and a key element information file. The key related information storage unit 1102 manages key element information, key difference information, and the like. The log file information storage unit 1103 holds the correspondence between the management of the given encrypted log file group with key information and the information in the key related information storage unit 1102. The reference user operation screen processing unit 1104 uses the information of the key related information storage unit 1102 to decrypt the encryption log file with the key information so that the reference is referred to, and also decrypts the key difference information to store the key related information. The information of the unit 1102 is updated, and the encrypted log files with key information before and after are decrypted and referred to in response to a request from the referrer.

  FIG. 12 shows details of the key related information storage unit 1102. The key related information storage unit 1102 includes a key element information storage unit 1201, a key difference element information storage unit 1202, a previous key element information storage unit 1203, and a next key element information storage unit 1204. The details of the information stored in these are the same as those described in the description of the log file encryption program 111 with reference to FIGS.

  FIG. 13 shows details of information stored in the log file information storage unit 1103. The log file information storage unit 1103 stores an ordered list 1301 of paths of the encryption log file group with key information. Also, a now pointer 1302, a prev pointer 1303, and a next pointer 1304 are provided. The now pointer 1302 is a pointer that points to the path to the encryption log file with key information corresponding to the key element information stored in the key element information storage unit 1201 of the key related information storage unit 1102. The prev pointer 1303 is a pointer that points to the path to the file before the now pointer 1302. The next pointer 1304 is a pointer that points to the path to the file after the now pointer 1302.

  FIG. 14 shows details of the initial input screen processing unit 1101. The initial input screen processing unit 1101 includes a key element information file input processing unit 1401, an encrypted log file group input processing unit with key information 1402, a corresponding log file designation input processing unit 1403, a log file information processing unit 1404, and a key. An element information file separation unit 1405 is configured. The key element information file input processing unit 1401 inputs the key element information file generated by the decryption key generation program 121. The encryption log file group with key information input processing unit 1402 inputs the encrypted log file with key information according to the order. Corresponding log file designation input processing unit 1403 is an encryption log with key information corresponding to the input key element information file among the encryption log files with key information input by encryption log file group input processing unit 1402 with key information. Specifies a file. The log file information processing unit 1404 sets information managed by the log file information storage unit 1103 from the information input by the input unit. The key element information file separation unit 1405 separates each key element from the key element information file input by the key element information file input processing unit 1401, and stores it as key element information in the key related information storage unit 1102. .

  FIG. 15 is a flowchart showing the processing procedure of the initial input screen processing unit 1101. First, the initial input screen 1600 shown in FIG. 16 is output (step 1501). The initial input screen 1600 includes an area 1601 for inputting an encryption log file group with key information, an area 1602 for inputting a key element information file, and an encryption log file corresponding to the key element information file in the encryption log file group with key information. Is composed of four areas: an area 1603 for inputting the “OK” and an OK button 1604.

  The reference person inputs in the areas 1601 to 1603 and presses an OK button 1604 (step 1502). Input to each of the areas 1601 to 1603 is processed by an encryption log file group with key information input processing unit 1402, a key element information file input processing unit 1401, and a corresponding log file designation input processing unit 1403, respectively. In FIG. 16, Log20040705.log is designated as one encryption log file with key information for which a decryption key is to be generated in step 1001 of FIG. 10, and it is set to 0, the old one is four, and the new one is three. An input example in the case of decryption using a key element information file Key2004705 obtained by specifying a range is shown.

  When the input of the referrer is completed in step 1502, the initial input screen processing unit 1101 uses the log file information processing unit 1402 to log file based on the information input to the area 1601 for inputting the encryption log file group with key information. An ordered list 1301 (FIG. 13) of paths of the encryption log file group with key information of the information storage unit 1103 is generated. In addition, the log file information processing unit 1403, based on the information input in the area 1603 for inputting the encryption log file corresponding to the key element information file, the now pointer 1302, the prev pointer 1303 of the log file information storage unit 1103, and Next pointer 1304 is set (step 1503). In the input example of FIG. 16, the now pointer 1302 points to the path of the encrypted log file Log20040705.log input to the area 1603, the prev pointer 1303 points to the path of the previous Log20040704.log, and the next pointer 1304 is 1. It is set to point to the path of the next Log20040706.log.

  Next, based on the information input to the key element information file input area 1602 by the key element information file separation unit 1405, the content of the key element information file is divided for each key element, and the key related information storage unit It is stored in the key element information storage unit 1201 1102 (step 1504).

  Thus, the process of the initial input screen processing unit 1101 is completed, and the process of the referer operation screen processing unit 1104 is started.

  FIG. 17 shows details of the reference user operation screen processing unit 1104. The reference user operation screen processing unit 1104 includes a log file input unit 1701 with key information, a data separation unit 1702, a key difference element information decryption processing unit 1703, a previous / next key element information processing unit 1704, a log file decryption processing unit 1705, a screen An output processing unit 1706, a file output processing unit 1707, and a key element information changing unit 1708 are configured.

  An encryption log file with key information input unit 1701 performs input processing of an encryption log file with key information to be decrypted and displayed. The data separation unit 1702 separates the input encrypted log file with key information into encrypted log file data 210, encrypted key difference element data 220, and encrypted key element data 230. The key difference element information decryption processing unit 1703 decrypts the encrypted key difference element data 220 separated by the data separation unit 1702 and stores it in the key difference element information storage unit 1202 of the key related information storage unit 1102. The previous / next key element information processing unit 1704 uses the information stored in the key element information storage unit 1201 and the key difference element information storage unit 1202 of the key-related information storage unit 1102 to generate the encryption log file with the previous and next key information. Key element information is calculated and stored in the previous key element information storage unit 1203 and the next key element information storage unit 1204. The log file decryption processing unit 1705 decrypts the encrypted log file data 210 separated by the data separation unit 1702. The screen output processing unit 1706 includes a log file data content decrypted by the log file decryption processing unit 1705, a decrypted log file name, previous and next log file names, and a reference person including operation buttons. It generates and outputs an operation screen. The file output processing unit 1707 outputs the contents of the displayed decrypted log file data to a file. The key element information changing unit 1708 changes the information stored by the key related information storage unit 1102 and the pointers stored by the log file information storage unit 1103 in accordance with the operation on the referrer operation screen of the referrer. Is.

  FIG. 18 is a flowchart illustrating a processing procedure of the reference user operation screen processing unit 1104. First, in the information stored in the key element information storage unit 1201, it is determined whether or not the nth log file encryption key 501 serving as a common key is 0 (that is, whether or not a common key does not exist). . If the key does not exist, the process ends. If it does exist, the process proceeds to step 1801 (step 1800).

  The encryption log file with key information input unit 1701 reads the encryption log file with key information 200 pointed to by the now pointer of the log file information storage unit 1103 (step 1801). Next, the data separation unit 1702 separates the read encrypted log file with key information 200 into encrypted log file data 210, encrypted key difference element data 220, and encrypted key element data 230 (step 1802). Next, the key difference element information decryption processing unit 1703 decrypts the separated encrypted key difference element data 220 using the nth log file encryption key 501 stored in the key element information storage unit 1201 as a common key. And stored in the key difference element information storage unit 1202 (step 1803). Next, the previous key element information is obtained from the information stored in the key element information storage unit 1201 and the key difference element information storage unit 1202 by using the reverse operation of the key difference element information generation method described in FIG. The next key element information is calculated and stored in the previous key element information storage unit 1203 and the next key element information storage unit 1204 (step 1804). Next, the log file decryption processing unit 1705 decrypts the encrypted log file data 210 separated in step 1802 using the common key used in step 1803 (step 1805). Next, a reference operation screen is generated from the log file decrypted in step 1805 and the name of the encrypted log file with key information pointed to by the now pointer 1302, prev pointer 1303, and next pointer 1304 of the log file information storage unit 1103. And output (step 1806).

  FIG. 19 shows details of the reference user operation screen. The referrer operation screen 1900 has a log output result area 1901 for displaying the contents of the decrypted log file, an area 1902 for displaying the name of the log file output to the area 1901, and the log file that is output one before. 1903 for displaying the log file name, 1904 for displaying the log file name immediately after the output log file, end button 1905 for the operation to end the reference, contents of the output log file A file button 1906 for the operation of outputting the file as a file, a prev button 1907 for the operation of displaying the previous log file, and a next button 1908 for displaying the next log file .

  After referring to the log output result 1901 on the referrer operation screen, the referrer inputs to press one of the end button 1905, the file button 1906, the prev button 1907, and the next button 1908 (step 1807). It is determined whether or not the end button 1905 has been pressed. If the end button 1905 has been pressed, the program is terminated; otherwise, the process proceeds to step 1809 (step 1808). Next, it is determined whether or not the file button 1906 has been pressed. If the file button 1906 has been pressed, the process proceeds to step 1810, and if not, the process proceeds to step 1811 (step 1809). If the file button has been pressed in step 1809, the file output processing unit 1707 outputs the log file output in the log output result 1901 as a plain text file (step 1810), and then the referrer input in step 1807 Return to. If the file button 1906 has not been pressed in step 1809, it is determined whether the prev button 1907 has been pressed. If it has been pressed, the process proceeds to step 1812. If not, the next button 1908 has been pressed. Therefore, the process proceeds to Step 1813 (Step 1811).

  In step 1812, the key element information change unit 1708 copies the information of the key element information storage unit 1201 of the key related information storage unit 1102 to the next key element information storage unit 1204, and stores the information of the previous key element information storage unit 1203 as the key. Copy to the element information storage unit 1201. Further, the now pointer 1302, the prev pointer 1303, and the next pointer 1304 of the log file information storage unit 1103 are changed to point to the previous file (step 1812).

  In step 1813, the key element information changing unit 1708 copies the information of the key element information storage unit 1201 of the key related information storage unit 1102 to the previous key element information storage unit 1203, and the information of the next key element information storage unit 1204 is used as the key. Copy to the element information storage unit 1201. Further, the now pointer 1302, the prev pointer 1303, and the next pointer 1304 of the log file information storage unit 1103 are changed to point to the next file, respectively (step 1813).

  After step 1812 and step 1813, the process returns to step 1801 to perform processing.

In the log file encryption according to the present embodiment, as described with reference to FIG. 2, when the referrer is allowed to decrypt m or more consecutive log files, the referrer can refer to all log files. . However, FIG. 18 does not include a process for allowing a referrer to refer to all log files when the referrer is allowed to decode m or more consecutive log files. A limited number of encrypted log files to be referred to by the referrer in advance are passed to the referrer, and the referrer inputs and refers to the encrypted log file group on the screen as shown in FIG. This is because the above processing is assumed. However, if all the encrypted log files can be accessed from the log file decryption terminal 130 used by the referrer, for example, via the network, the referrer can be permitted by allowing the referrer to decrypt m or more consecutive log files. It makes sense to be able to see all log files. In this case, the common key for decrypting the previous and next encrypted log files of the m consecutive log files is the key difference element α _{*, 0 to} α _*, included in the consecutive m or more encrypted files _{. Since it is obtained by} the sum of _{m−1 and} the sum of −α _{*, m} to −α _{*, 2m−1} , such processing may be added. Specifically, when the prev button is pressed in the process of FIG. 18 and the process returns to step 1800 via step 1812 and there is no common key, or the next button is pressed and the process returns to step 1800 via step 1813 and the common key. If there is no (if it is out of the range to be referred), if it is a prev button, whether or not the key difference element α of m encrypted files continuous behind the log file to be referred to can be obtained If it is the next button, it is determined whether or not the key difference element α of the m encrypted files consecutive in front of the log file to be referred to can be obtained. If the key difference element α of these m encrypted files can be acquired, the common key of the encryption log file to be referred to by the prev button or the next button can be obtained from those key difference elements as described above. The common key is obtained and the process proceeds to step 1806. When the key difference element α of m encrypted files cannot be acquired, the process ends.

  In the above embodiment, encryption and decryption of a log file has been described as an example. However, the present invention can be applied to encryption / decryption of an arbitrary plurality of files that are sequentially ordered.

Overall system configuration diagram Figure showing details of the encryption log file with key information corresponding to the nth log file Configuration diagram of log file encryption program Log file encryption program processing flowchart The figure which shows the details of the information which the key element information storage section stores The figure which shows the detail of the information which the former key element information storage section stores The figure which shows the details of the information which the next key element information storage section stores The figure which shows the detail of the information which a key difference element information storage part stores Configuration diagram of decryption key generation program Processing flow of decryption key generation program Overview of log file decryption program The figure which shows the details of the key related information storage section Figure showing details of information stored by the log file information storage unit The figure which shows the details of the initial input screen processing section Processing flowchart of initial input screen processing unit Screen diagram showing the initial input screen The figure which shows the details of the referer operation screen processing section Flowchart of reference user operation screen processing unit Screen shot of referrer operation screen

Explanation of symbols

  110: Log file encryption terminal, 120 ... Decryption key generation terminal, 130 ... Log file decryption terminal, 111 ... Log file encryption program, 112 ... Public key PK, 121 ... Decryption key generation program, 122 ... Secret key SK, 131 ... Log File decryption program, 200 ... encrypted log file with key information, 210 ... encrypted log file data, 220 ... encrypted key difference element data, 221 ... key difference element information, 230 ... encrypted key element data, 231 ... key element information , 301 ... log file input unit, 302 ... random number generation unit, 303 ... previous key element information storage unit, 304 ... key element information storage unit, 305 ... next key element information storage unit, 306 ... key difference element information storage unit, 307 ... log file encryption part, 308 ... key element information encryption part, 309 ... key difference element information encryption part, 310 ... data combination part, 311 ... encryption log file output part with key information, 501 ... n-th log file encryption key , 502 ... nth and subsequent log files No. key element group, 503... Nth log file encryption key element group, 601... N-1 log file encryption key, 602... N-1 log file encryption key element group, 603. n-1st log file encryption key element group, 701 ... n + 1 log file encryption key, 702 ... n + 1 log file encryption key element group, 703 ... n + 1th Previous log file encryption key element group, 901 ... encryption log file / key range input unit, 902 ... encryption log file separation unit, 903 ... key element information decryption processing unit, 904 ... key element information storage unit, 905 ... out of range information Deletion processing unit, 906 ... Key element information file combination unit, 907 ... Key element information file output unit, 1101 ... Initial input screen processing unit, 1102 ... Key related information storage unit, 1103 ... Log file information storage unit, 1104 ... Reference screen Processing unit, 1201 ... Key element information storage unit, 1202 ... Key difference element information storage unit, 1203 ... Previous key element information storage unit, 1204 ... Next key required Information storage unit, 1301 ... List with path order, 1302 ... now pointer, 1303 ... prev pointer, 1304 ... next pointer, 1401 ... Key element information file input processing unit, 1402 ... Cryptographic log file group input processing unit with key information, 1403 ... corresponding log file designation input processing unit, 1404 ... key element information file separation unit, 1600 ... initial input screen, 1701 ... log file input unit with key information, 1702 ... data separation unit, 1703 ... key difference element information decryption processing unit, 1704: Pre- and post-key element information processing unit, 1705 ... Log file decryption processing unit, 1706 ... Screen output processing unit, 1707 ... File output processing unit, 1708 ... Key element changing unit, 1900 ... Referer operation screen.

Claims (9)

A method of encrypting a plurality of files that are sequentially ordered,
File input means provided in the computer, inputting the file according to the order;
An encryption means included in the computer encrypts the input file with a common key generated for each file;
A key element generating means provided in the computer generates a key element for calculating a common key of a file that continues in front and back, and encrypts it with a public key;
A key difference element generation means provided in the computer calculates a key difference element for calculating a common key of a file that continues before and after, and encrypts the file with the common key generated when the file is encrypted;
A file encryption method comprising: a combining unit included in the computer; and a step of combining the encrypted information into one file with key information. A key information extraction method for extracting key information for decrypting a file with key information encrypted by the file encryption method according to claim 1, comprising:
A range input means provided in the computer for inputting information specifying one file to be decoded and a range of files to be decoded before and after the file;
A key element extraction means provided in the computer, extracting the encrypted key element from the identified file with key information;
A key element decryption means included in the computer decrypts the encrypted key element with a secret key;
The out-of-range deletion means provided in the computer excludes information of key elements outside the specified range among the decrypted key elements;
A key information extraction method comprising: a key file generation means provided in a computer, the step of combining the output result into one key information file and outputting the result. A file decryption method for decrypting a file with key information encrypted by the file encryption method according to claim 1 using the key information file output by the key information extraction method according to claim 2. And
A step of inputting an encryption file group with key information to be decrypted and a key information file by an input means provided in the computer;
Data separating means provided in the computer separates the encrypted file data, the encrypted key difference element data, and the encrypted key element data from the encrypted file with key information obtained by extracting the key element of the key information file;
Decrypting means provided in the computer, decrypting the separated encrypted file data with a common key extracted from the key information file and outputting the screen;
A method for decrypting a file with key information, comprising: a step of: operating means included in the computer comprising: sequentially decrypting and outputting a file with key information in a range specified by the key information file based on a user operation . A method of encrypting a plurality of files that are sequentially ordered,
A first step in which a file input means included in the computer inputs an n-th (n = 0, 1, 2,...) File according to the order;
A second step in which a determination unit included in the computer determines whether the file is the first file (n = 1);
When it is the first file, the initial key element information generating means provided in the computer sets m as a predetermined threshold, and β = 1 _{−m + 1,1,.} , Β _{n−1, m−1} , β _{n, m} , β _{n + 1, m + 1} ,..., Β _{n + m−1,2m−1} are generated (when the first subscript is 0 or less) Or 0 _nm when the second subscript is outside the range of 0 to 2 m), β _nm, which is a key element stored in the key element information storage unit and further stored in the previous key element information storage unit ₁ ,..., Β _{n−2, m−1} , β _{n−1, m} , β _{n, m + 1} ,..., Β _{n + m−2, 2m−1} are all set to 0;
The encryption means included in the computer generates encrypted file data by encrypting the input n-th file using β _{n, m} stored in the key element information storage unit as a common key. 4 steps,
The key element generation means included in the computer has the following (n + 1) th key element information as β _{n-m + 2,1} ,..., Β _{n, m−1} , β _{n + 1, m} , β _{n + 2, m +1} , ..., β _{n + m, 2m-1} is generated (however, when the first subscript is 0 or less, or when the second subscript is outside the range of 0 to 2 m, it is set to 0) A fifth step of storing in the next key element information storage unit;
The key difference element generation means provided in the computer is based on information stored in the previous key element information storage unit, the key element information storage unit, and the next key element information storage unit, α _{nm, 0} = β _{nm, 1} , α _{n− m + 1,1} = β _{n-m + 1,2} −β _{n-m + 1,1} ,..., α _{n-2, m-2} = β _{n-2, m-1} −β _{n-2, m -2} , α _{n-1, m-1} = β _{n-1, m} −β _{n-1, m-1} , -α _{n + 1, m} = β _{n + 1, m} −β _{n + 1, m + 1} , -α _{n + 2, m + 1} = β _{n + 2, m + 1} −β _{n + 2, m + 2} , ..., -α _{n + m-1,2m-2} = β _{n + m-1 , 2m-2} -β _{n + m-1,2m-1} , -α _{n + m, 2m-1} = β _{n + m, 2m-1} is calculated and stored in the key difference element information storage unit as a key difference element A sixth step,
The encryption processing means included in the computer generates encrypted key element data by encrypting the information stored in the key element information storage unit using a public key, and the information stored in the key difference element information storage unit A seventh step of generating encrypted key difference element data by encrypting with the common key β _{n, m} used in the fourth step;
The copy processing means provided in the computer copies the information stored in the key element information storage unit to the previous key element information storage unit, and copies the information stored in the next key element information storage unit to the key element information storage unit An eighth step to:
A combining unit included in the computer includes: a ninth step of generating a file with key information by combining the encrypted file data, the encrypted key element data, and the encrypted key difference element data, and indicating a file order; A method for encrypting a file, wherein the plurality of files are encrypted by executing the first to ninth steps while incrementing the value of n. A key information extraction method for extracting key information used for decrypting a file encrypted by the file encryption method according to claim 4,
A first step in which range input means provided in the computer inputs information for identifying n-th encrypted file data that permits decryption and a range that permits decryption before and after the file;
The key element extraction means provided in the computer extracts the encrypted key element data from the file with key information including the specified encrypted file data, and obtains β _{n-m + 1,} obtained by decrypting using the secret key ₁ , ..., β _{n-1, m-1} , β _{n, m} , β _{n + 1, m + 1} , ..., β _{n + m-1,2m-1} are stored in the key element information storage unit as key elements A second step of:
The out-of-range information deleting means provided in the computer excludes key elements outside the specified range from the key elements stored in the key element information storage unit based on the range input in the first step. A third step;
A key information extraction method comprising: a key file generation / output unit provided in the computer, and a fourth step of outputting the result after the exclusion as one key information file. A file decryption method for decrypting a file encrypted by the file encryption method according to claim 4, using the key information file output by the key information extraction method according to claim 5,
An input means included in the computer includes: a key information file output by the key information extraction method according to claim 5; information specifying the nth encrypted file data permitted to be decrypted; and the decryption. A first step of inputting an encrypted file group with key information in an allowed range;
Based on the key elements of the input key information file, the key information input means provided in the computer is based on β _{n-m + 1,1} ,..., Β _{n−1, m−1} , β _{n, m} , β _{n + A} second step of storing _{1, m + 1} , ..., β _{n + m-1,2m-1} as key elements in the key element information storage unit;
A third step in which data separation means included in the computer extracts the encrypted file data and the encrypted key difference element data from the n-th encrypted file data;
The key difference element information decryption means provided in the computer decrypts the extracted encrypted key difference element data using the common key β _{n, m} in the key element information storage unit, and the obtained α _{nm, 0} , α _{n -m + 1,1} , ..., α _{n-2, m-2} , α _{n-1, m-1} , -α _{n + 1, m} , -α _{n + 2, m + 1} , ..., -α _{n a} fourth step of storing _{+ m-1,2m-2} , -α _{n + m, 2m-1} as key difference element information in the key difference element information storage unit;
The previous / next key element information processing means included in the computer calculates β _{nm, 1} = α _{nm, 0} , β _{n-m + 1,2} from the information of the key difference element information storage unit and the information of the key element information storage unit. = Β _{n-m + 1,1} + α _{n-m + 1,1} ,..., Β _{n-1, m} = β _{n-1, m-1} + α _{n-1, m-1} , β _{n + 1, m} = Β _{n + 1, m + 1} -α _{n + 1, m} , ..., β _{n + m-1,2m-2} = β _{n + m-1,2m-1} -α _{n + m-1,2m- 2} , β _{n + m, 2m−1} = −α _{n + m, 2m−1} is calculated and stored in the previous key element information storage unit or the next key element information storage unit as the previous key element or the next key element. And the steps
A decrypting means provided in the computer, using a common key β _{n, m} stored in the key difference element information storage unit, decrypting the encrypted file data extracted in the third step;
A screen output means provided in the computer for displaying the decrypted file data on a screen;
The key element information changing means provided in the computer is
(A) When it is detected that an operation for instructing reference to the previous file has been made, the information stored in the key element information storage unit is copied to the next key element information storage unit, and the previous key element The information stored in the information storage unit is copied to the key element information storage unit, and the previous file is returned to the third step as the nth file to be referred to,
(B) When it is detected that an operation for instructing reference to the next file has been made, the information stored in the key element information storage unit is copied to the previous key element information storage unit, and the next key element And an eighth step of copying the information stored in the information storage unit to the key element information storage unit and returning to the third step as the nth file to be referred to by the next file. A method for decrypting a file with key information. A file encryption apparatus that encrypts a plurality of files that are sequentially ordered,
File input means for inputting files according to the order;
Encryption means for encrypting the input file with a common key generated for each file;
A key element generating means for generating a key element for calculating a common key of a file that is continuous before and after, and encrypting with a public key;
A key difference element generating means for calculating a key difference element for calculating a common key of a file that continues before and after, and encrypting with the common key generated when the file is encrypted;
A file encryption apparatus comprising: a combination unit configured to combine the one encrypted by the unit into a file with key information. A key information extraction device for extracting key information for decrypting a file with key information encrypted by the file encryption device according to claim 7,
Range input means for inputting information for specifying one file to be decrypted and a range of files to be decrypted before and after the file;
Key element extraction means for extracting an encrypted key element from the identified file with key information;
Key element decryption means for decrypting the encrypted key element with a secret key;
Out-of-range deletion means for excluding information on key elements other than the specified range among the decrypted key elements;
A key information extraction apparatus comprising: a key file generation unit that outputs the result of the exclusion combined with one key information file. A file decryption device for decrypting a file with key information encrypted by the file encryption device according to claim 7 by using the key information file output by the key information extraction device according to claim 8. And
An input means for inputting an encrypted file group with key information to be decrypted and a key information file;
Data separating means for separating encrypted file data, encrypted key difference element data, and encrypted key element data from an encrypted file with key information obtained by extracting the key element of the key information file;
Decrypting means for decrypting the separated encrypted file data with a common key extracted from the key information file and outputting a screen;
A file decrypting apparatus with key information, comprising: means for sequentially decrypting and outputting a file with key information in a range specified by the key information file based on a user's operation.

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