JP5255154B1 - Crypto system capable of partial match search - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an encryption device and an encryption program for generating encryption data that can secure encryption strength that can withstand practical use and that can be partially matched.
A block data generating unit (a1) sequentially selects one character at a time from a character string to be encrypted in order, and (a2) selects a character string having a predetermined plural character length from a selected character as a block character. A block is extracted from the encryption target character string, and (a3) block data having an encrypted block length is generated from the extracted block character string data. The encrypted block length is a predetermined data length that is equal to or greater than the maximum data length of the block character string. The encryption processing unit 63 encrypts block data using a block encryption method. The encryption data generation unit 64 combines encrypted block data corresponding to a plurality of block character strings obtained from the encryption target character string, and generates encryption data for the encryption target character string.
[Selection] Figure 2

Description

  The present invention relates to an encryption system capable of partial match search.

  With the spread of cloud computing in recent years, user data is often stored in a database in a service provider's system.

  In such a system, by accessing the database on the service provider side, the user data can be read and the contents of the data can be acquired. Therefore, if there is a Service-to-Self on the service provider side, there is a possibility that the confidential information of the user stored in the database will be leaked.

  Therefore, a technique for encrypting user data and storing it in a database has been proposed. In a database where encrypted user data is stored, when searching without decrypting the encrypted user data, the search key is encrypted and then the database search is performed. Although an exact match search that finds matching data is possible, in general, a partial match search that finds data that partially hits the search key is difficult.

  In view of this point, in the system described in Patent Document 1, data is converted character by character by single substitution encryption (that is, substitution encryption using a single substitution table), and the converted data is encrypted. The search key is also converted character by character with the same single substitution cipher, and a partial match search is performed with the converted search key.

  In addition, in the system described in Patent Document 2, index information converted by single substitution type encryption (Caesar encryption) is registered in the server in addition to the encrypted document, and the same search key is used for the search. A partial match search of index information is performed after conversion using a single substitution cipher.

JP 2002-108910 A JP 2002-278970 A

  However, all of the above-described techniques use single substitutional encryption and are encrypted in units of one character, so that it is impossible to secure a cryptographic strength that can withstand practical use. Further, even if encryption is performed character by character using another encryption method, since the data length of the original data is as short as one character, the encryption is easily deciphered.

  The present invention has been made in view of the above problems, and provides an encryption device and an encryption program that generate encrypted data that can ensure practically sufficient encryption strength and that can be partially matched. With the goal.

  In order to solve the above problems, the present invention is configured as follows.

An encryption apparatus according to the present invention includes a block data generation unit, an encryption processing unit, and an encryption data generation unit. The block data generation unit (a1) sequentially selects one character at a time from the character string to be encrypted that is one of the character string to be searched and the search key for which encrypted data is generated by the same method, a2) A character string having a predetermined plurality of characters continuous from the selected character is extracted as a block character string from the character string to be encrypted, and (a3) block data having an encrypted block length is generated from the extracted block character string data. . The encrypted block length is a predetermined data length that is equal to or greater than the maximum data length of the block character string. The encryption processing unit encrypts block data obtained by the block data generation unit by a block encryption method in which encryption is performed in units of encrypted block length. The encryption data generation unit combines encrypted block data corresponding to a plurality of block character strings obtained from the encryption target character string to generate encryption data for the encryption target character string.

  As a result, block data containing a block character string with multiple character lengths is block-encrypted with a sufficient encryption block length, so that the encryption strength that can withstand practical use can be secured and partial matching search is possible. Data can be generated.

  In addition to the above-described encryption apparatus, the encryption apparatus according to the present invention may be configured as follows. In this case, the encryption device further includes an encryption target specifying unit. The encryption target identification unit obtains the encryption target information that specifies the database table and the columns in the table as the encryption target, and specifies the encryption target information in the record when registering the record in the database. The character string of the designated column is specified as the character string to be encrypted.

  As a result, only the character string of the specific column can be partially matched and can be used as encrypted data.

  In addition to the above-described encryption apparatus, the encryption apparatus according to the present invention may be configured as follows. In this case, the encryption target specifying unit specifies a search key to be an encryption target character string based on the encryption target information when searching in the database.

  Thus, even when a plain text search key is given, the search key is selectively encrypted as necessary, and a partial match search can be performed without decrypting the encrypted data in the database.

  In addition to the above-described encryption apparatus, the encryption apparatus according to the present invention may be configured as follows. In this case, the encryption apparatus further includes a decryption unit that decrypts the encrypted data of the column specified by the encryption target information in the record hit at the time of searching in the database. The decryption unit includes an encryption block data extraction unit, a decryption processing unit, and a plaintext data generation unit. The encryption block data extraction unit extracts a plurality of encryption block data having an encryption block length from the encryption data. The decryption processing unit decrypts the encrypted block data by a decryption method corresponding to the encryption method of the encryption processing unit. The plaintext data generation unit (b1) extracts block character strings from the data obtained by decryption by the decryption processing unit from the plurality of cipher block data, and (b2) plaintext for the cipher data from the extracted block character strings. Generate data.

  As a result, the encrypted data in the record hit by the search can be decrypted and presented to the user as a search result.

  In addition to the above-described encryption apparatus, the encryption apparatus according to the present invention may be configured as follows. In this case, the encrypted block length is a predetermined data length longer than the maximum data length of the block character string, and the block data generation unit generates block data by padding the block character string data.

  As a result, an encryption method having a long encryption block length and high encryption strength can be employed.

  In addition to the above-described encryption apparatus, the encryption apparatus according to the present invention may be configured as follows. In this case, the character length of the block character string is two characters, and the block encryption method of the encryption processing unit is a common key encryption method that is not a substitution type encryption.

  An encryption program according to the present invention causes a computer to function as the block data generation unit, the encryption processing unit, and the encryption data generation unit.

  According to the present invention, it is possible to obtain an encryption device and an encryption program that can ensure encryption strength that can be practically used and can generate encrypted data that can be partially matched.

FIG. 1 is a block diagram showing a configuration of a system according to an embodiment of the present invention. FIG. 2 is a block diagram illustrating a configuration example of the proxy device in FIG. FIG. 3 is a flowchart for explaining the operation of the proxy device in FIG. FIG. 4 is a flowchart for explaining details of the encryption processing in steps S3 and S6 in FIG. FIG. 5 is a diagram showing an example of a table managed by the database server in FIG. FIG. 6 is a diagram for explaining a series of data generated by the encryption processing in steps S3 and S6 in FIG. FIG. 7 is a flowchart illustrating details of the decoding process in step S9 in FIG. FIG. 8 is a diagram for explaining a series of data generated by the encryption process for the search key in step S6 of FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Embodiment 1 FIG.

  FIG. 1 is a block diagram showing a configuration of a system according to an embodiment of the present invention.

  In the system shown in FIG. 1, a server apparatus 1 is connected to a network 3 such as the Internet via a gateway 2 and operates an application server 11. The server device 1 has a built-in computer, and the application server 11 is operated by executing a program on the computer.

  The application server 11 is a front-end server, and a service providing unit 12 that provides various services to the user via a network 3 by a software as a service (SaaS) method, and a service provided by the service providing unit 12 And a data management unit 13 for managing user data.

  A server device 4 and a proxy device 5 are connected to the server device 1 via, for example, a LAN (Local Area Network). The proxy device 5 is an embodiment of the encryption device of the present invention. A user terminal device 6 operated by the user is connected to the network 3 via the gateway 7, and the application server 11 executes various processes in response to requests from the user terminal device 6.

  User data managed by the data management unit 13 is registered and held in the back-end database server 21 in the server device 4. The database server 21 accepts various commands such as record registration, reading, and search, executes processing corresponding to the accepted command, and transmits the processing result as a response to the command. The server device 4 has a built-in computer, and the database server 21 is operated by executing a program on the computer.

  In the first embodiment, the proxy device 5 operates as a proxy between the data management unit 13 and the database server 21.

  The data management unit 13 transmits a command that conforms to the specifications of the database server 21, and the proxy device 5 receives the command from the data management unit 13, encrypts the encryption target part in the command, The command is transmitted to the database server 21, a response to the command is received from the database server 21, the part to be decoded in the response is decoded, and the response is transmitted to the data management unit 13.

  The protocol used between the data management unit 13 and the database server 21 and the existing data management unit 13 and database server 21 can be used regardless of the proxy device 5.

  Then, when the proxy device 5 receives the registration command from the data management unit 13, if the data registered by the registration command includes a character string registered in the specified column of the specified table, the proxy device 5 After the character string is replaced with encrypted data that can be partially matched by the database server 21, the command is transmitted to the database server 21.

  In addition, when the proxy device 5 receives the search command from the data management unit 13, at the time of partial match search, the proxy device 5 encrypts the search key, transmits the search command to the database server 21, and records the hit record as the search result in the database. When received from the server 21, the encrypted data in the specified column of the specified table included in the search result record is decrypted, and the search result record including the decrypted original character string is stored in the data management unit 13. Send to.

  FIG. 2 is a block diagram illustrating a configuration example of the proxy device 5 in FIG.

  The proxy device 5 includes a computer. The computer includes a CPU (Central Processing Unit) 31 that is a processor, a ROM (Read Only Memory) 32 that is a nonvolatile memory, and a RAM (Random Access Memory) that is a main storage device. ) 33, a hard disk drive, an auxiliary storage device 34 such as an SSD (Solid State Drive), and a communication device 35 such as a network interface.

  Various processing units are realized by loading a program stored in the ROM 32 or the auxiliary storage device 34 into the RAM 33 and executing it by the CPU 31. This processing unit executes processing while temporarily storing data in the RAM 33.

  In the first embodiment, a communication processing unit 51, an encryption unit 52, and a decryption unit 53 are realized based on the encryption program 41.

  The communication processing unit 51 controls the communication device 35 to perform network communication between the data management unit 13 and the database server 21.

  The encryption unit 52 identifies the encryption target, encrypts the identified encryption target, and replaces the encryption target with the encrypted encryption target. The encryption unit 52 includes an encryption target specifying unit 61, a block data generation unit 62, an encryption processing unit 63, and an encryption data generation unit 64.

  The encryption target specifying unit 61 acquires from the application server 11 encryption target information that designates a database table and a column in the table by the database server 21 as an encryption target, and at the time of registering the record in the database, In the record, the character string of the column specified by the encryption target information is specified as the encryption target character string. Note that the application server 11 specifies the encryption target information in advance by a user setting specified from the user terminal device 6.

  Further, the encryption target specifying unit 61 specifies the search key in the search command as an encryption target character string when searching in the database. If the search target by the search command is a column specified by the encryption target information, the encryption target specifying unit 61 sets the search key as an encryption target character string. It is not a character string to be encrypted.

  The block data generation unit 62 (a1) sequentially selects one character at a time from the beginning of the character string to be encrypted, and (a2) selects a character string having a predetermined multiple character length starting from the selected character as a block character string. And (a3) block data having an encrypted block length is generated from the extracted block character string data.

  The encrypted block length is a predetermined data length that is equal to or greater than the maximum data length of the block character string. For example, the character length of the block character string is 2 characters, and when the character is a 1-byte character or a 2-byte character, the maximum data length of the block character string is 4 bytes. Note that the data length of each character is specified from, for example, the type of character code being used.

  The encryption processing unit 63 encrypts the block data obtained by the block data generation unit 62 by a block encryption method in which encryption is performed in units of a predetermined encryption block length.

  The encryption data generation unit 64 combines a plurality of encryption block data obtained from a plurality of block character strings extracted from the encryption target character string to generate encryption data for the encryption target character string.

  In the first embodiment, the encrypted block length is a predetermined data length longer than the maximum data length of the block character string, and the block data generating unit generates block data by padding the block character string data. .

  In the first embodiment, the block character string has a character length of 2 characters, and the encryption method has a key length of 128 bits, 192 bits or 256 bits, and an encryption block length of 128 bits. AES (Advanced Encryption Standard) method is used. However, the character length of the block character string may be 3 characters or more, and the encryption method of the encryption processing unit 63 is another common key encryption method that is not a substitution type encryption (agitation by bit operation using an encryption key). Modern encryption method). As the encryption method of the encryption processing unit 63, an encryption block length whose multiple is a multiple of 8 bits is used. For example, the encryption key of the encryption processing unit 63 is set for each user and stored in the proxy device 5.

  The decrypting unit 53 identifies the encrypted data to be decrypted, decrypts the identified encrypted data, and replaces the decrypted encrypted data with the plaintext data after decryption. The decrypting unit 53 decrypts the encrypted data in the column designated by the encryption target information in the record hit during the search in the database. The decryption unit 53 includes a decryption target identification unit 71, an encrypted block data extraction unit 72, a decryption processing unit 73, and a plaintext data generation unit 74.

  Based on the above-described encryption target information, the decryption target specifying unit 71 specifies the encrypted data of the column designated by the encryption target information in the record as the decryption target encrypted data.

  The encryption block data extraction unit 72 extracts a plurality of encryption block data having an encryption block length from the encryption data specified by the decryption target specification unit 71.

  The decryption processing unit 73 decrypts the extracted encrypted block data with a decryption method corresponding to the encryption method of the encryption processing unit 63.

  The plaintext data generation unit 74 (b1) extracts block character strings from the data obtained by the decryption by the decryption processing unit 73 from the plurality of encrypted block data, and (b2) encrypts the encrypted data from the extracted block character strings. Generate plain text data for.

  Next, the operation of the proxy device 5 will be described.

  FIG. 3 is a flowchart for explaining the operation of the proxy device 5 in FIG.

  When receiving a command addressed to the database server 21 from the data management unit 13 (step S1), the communication processing unit 51 determines whether or not the command is a registration command (step S2).

  If the command is a registration command, the encryption unit 52 executes encryption processing for the record to be registered (step S3), and the communication processing unit 51 sends the registration command after encryption processing to the database server 21. Transmit (step S4). The database server 21 registers the encrypted record in the database according to the registration command.

  If the command is not a registration command, the communication processing unit 51 determines whether or not the command is a search command (step S5).

  If the command is a search command, the encryption unit 52 executes encryption processing for the search key (step S6), and the communication processing unit 51 transmits the search command after the encryption processing to the database server 21. (Step S7). The database server 21 performs a search with the encrypted search key in accordance with the search command, reads the hit record from the database, and transmits it as response data.

  When the communication processing unit 51 receives response data for the search command from the database server 21 (step S8), the communication processing unit 51 executes a decoding process for the response data (step S10), and the response data after the decoding process is sent to the data management unit 13. (Step S10).

  If the received command is a command that does not require encryption processing and decryption processing, the communication processing unit 51 transmits the command to the database server 21 as it is, and receives a response to the command from the database server 21. Then, it transfers to the data management part 13 as it is (step S11).

  Here, details of the encryption processing in steps S3 and S6 will be described.

  FIG. 4 is a flowchart for explaining details of the encryption processing in steps S3 and S6 in FIG. FIG. 5 is a diagram showing an example of a table managed by the database server 21 in FIG. FIG. 6 is a diagram for explaining a series of data generated by the encryption processing in steps S3 and S6 in FIG.

  In the encryption processing of steps S3 and S6, first, the encryption target specifying unit 61 performs encryption on the received command (for a specific column of a specific table in a registration command and a specific column of a specific record in a search command). It is determined whether or not there is a search key (step S21). When there is no encryption target in the received command, this encryption process is skipped.

  For example, when the address column of the address book table shown in FIG. 5 is designated as an encryption target, a registration command for registering a record in the address book table and a search command for the address column of the address book table are When received, it is determined that there is an encryption target (a character string in the address column in the record and a search key) in the received command.

  If there is an encryption target in the received command, the block data generation unit 62 first sets the first character of the character string to be encrypted as the block end character (step S22).

  For example, when the character string 101 “Shinjuku-ku, Tokyo” shown in FIG. 6 is an encryption target, the first character “east” is set as the first block end character 102-1.

  Next, the block data generation unit 62 extracts two characters starting from the block end character as a block character string (step S23).

  For example, as illustrated in FIG. 6, for the block end character 102-1, a block character string 103-1 “Tokyo” is extracted from the character string 101.

  Then, the block data generation unit 62 generates block data having an encrypted block length from the extracted character string data of the block character string (step S24).

  For example, when the two extracted characters are each 2-byte characters, the data length of the extracted character string data of the two characters is 4 bytes. If the encrypted block length is 128 bits (= 16 bytes), the block data generation unit 62 combines 12 bytes of padding data with 4 bytes of character string data as shown in FIG. Byte block data 104-1 is generated. The padding data is predetermined data corresponding to the extracted two characters.

  When the block data is generated, the encryption processing unit 63 encrypts the encrypted block length block data, and generates encrypted block length encrypted block data (step S25).

  Thereby, as shown in FIG. 6, for example, for one character 102-1 in the character string 101, one encrypted block data 105-1 corresponding to the block character string 103-1 of the character 102-1 is obtained. Generated.

  When the encrypted block data is generated, the block data generating unit 62 determines whether or not the currently set block end character is the second character from the end of the character string to be encrypted (step S26). ). That is, it is determined whether or not the current block end character is the (character length of encryption target character string−character length of block character string + 1) -th character.

  If the currently set block end character is not the second character from the end of the character string to be encrypted, the block data generation unit 62 sets the next character after the currently set block end character to the block end character. A character is set (step S27). When a block end character is newly set, the processing after step S23 is executed for the block end character.

  For example, in the character string 101 “Shinjuku-ku, Tokyo” shown in FIG. 6, when the first character “East” is the current block end character, the character “Kyo” is newly set as the block end character 102-2. Then, the block character string 103-2 is extracted corresponding to the block end character 102-2, the block data 104-2 is generated, and the encrypted block data 105-2 is generated.

  Similarly, block end characters 102-3 to 102-5 such as “Me”, “New”, and “Hotel” are set in order, and corresponding to these block end characters 102-3 to 102-5, respectively. The block character strings 103-3 to 103-5 are extracted, block data 104-3 to 104-5 are generated, and encrypted block data 105-3 to 105-5 are generated.

  In step S26, when the currently set block end character is the second character from the end of the character string to be encrypted, the encrypted data generation unit 64 generates all of the character strings to be encrypted. The encryption block data is combined to generate encryption data for the encryption target (step S28), and the encryption target in the command is replaced with the encryption data (step S29).

  For example, when the character string 101 “Shinjuku-ku, Tokyo” shown in FIG. 6 is an encryption target, encrypted block data 105-1 to 105-5 corresponding to five block character strings 103-1 to 103-5 are stored. Are combined in the order corresponding to the order of the characters 102-1 to 102-5, and the encrypted data 106 is generated.

  In this way, the encryption process is performed.

  Next, details of the decoding process in step S9 will be described.

  FIG. 7 is a flowchart illustrating details of the decoding process in step S9 in FIG.

  In the decoding process of step S9, first, the decoding target specifying unit 71 determines whether or not there is a decoding target (a specific column of a specific table in the registration command) in the received response data (step S41). When there is no decoding target in the received command, this decoding process is skipped.

  If there is a decryption target in the received response data, the cipher block data extraction unit 72 first extracts the top cipher block data in the decryption target cipher data (step S42). For example, in the case of the encrypted data 106 shown in FIG. 6, the first encrypted block data 105-1 is extracted.

  When the encrypted block data is extracted, the decryption processing unit 73 decrypts the encrypted block data and generates block data having an encrypted block length (step S43).

  The plaintext data generation unit 74 extracts the above-described two-character block character string included in the block data (step S44).

  For example, in the example shown in FIG. 6, the block data 104-1 is generated from the encrypted block data 105-1 by decryption, and the block character string 103-1 (“Tokyo” from the first 4 bytes of the block data 104-1 is generated. )) Is extracted.

  When the plaintext block character string corresponding to one piece of cipher block data is specified in this way, the cipher block data extraction unit 72 determines that the current cipher block data is the last cipher block data in the cipher data to be decrypted. It is determined whether or not (step S45).

  If the current cipher block data is not the last cipher block data in the cipher data to be decrypted, the cipher block data extraction unit 72 extracts the cipher block data next to the current cipher block data from the decryption target (step S46). When new encryption block data is extracted, the processes after step S43 are executed for the encryption block data.

  When the block character string corresponding to all the encrypted block data in the decrypted encryption data is specified, the plaintext data generation unit 74 starts from the first encrypted block data to the second encrypted block data from the last. Are combined with the first character of the block character string, and the block character string for the last encrypted block data is combined to generate the original character string to be decrypted (step S47). The character string is replaced (step S48).

  For example, five encrypted block data 105-1 to 105-5 are extracted from the encrypted data 106 shown in FIG. 6, and five block character strings 103-1 to 103-5 (“Tokyo”, “Kyoto”, “ The original character string 101 (“Shinjuku-ku, Tokyo”) is generated from “Toshin”, “Shinjuku”, and “Suku-ku”).

  In this way, the decoding process is performed.

  Here, a specific example of partial match search will be described.

  Here, a case will be described in which encrypted data 106 corresponding to the character string 101 “Shinjuku-ku, Tokyo” shown in FIG. 6 is registered in the database and a search is performed using a search key “Shinjuku-ku”.

  FIG. 8 is a diagram for explaining a series of data generated by the encryption process for the search key in step S6 of FIG.

  When the search key 201 “Shinjuku-ku” is set in the search command, as shown in FIG. 8, the block character string 203-1 “Shinjuku” is the search key for the block end character 202-1 “new”. The block data 204-1 corresponding to the block character string 203-1 is generated from the data 201, and the block data 204-1 is encrypted to generate the encrypted block data 205-1.

  Similarly, for the block end character 202-2 “inn”, a block character string 203-2 “juku-ku” is extracted from the search key 201, and block data 204-2 corresponding to the block character string 203-2 is obtained. The block data 204-2 is encrypted, and the encrypted block data 205-2 is generated.

  Then, the encrypted block data 205-1 and 205-2 are combined to generate encrypted data 206 corresponding to the search key 201, and the search key 201 is replaced with the encrypted data 206.

  Therefore, the database server 21 performs a search using the encrypted data 206 as a search key.

  As shown in FIG. 6, the encrypted data 106 includes encrypted block data 105-4 of a block character string 103-4 “Shinjuku” and encrypted block data 105-5 of a block character string 103-5 “Juku”. Therefore, when the database server 21 performs a search using the encrypted data 206 as a search key, a record including the encrypted data 106 is hit.

  In this way, partial matching search can be performed by encrypting the search key in the search command by the same method as described above.

  As described above, according to the first embodiment, the block data generation unit 62 (a1) selects block end characters sequentially from the encryption target character string one character at a time, and (a2) selects them. A block character string having a predetermined plurality of characters continuous from the block end character is extracted from the encryption target character string, and (a3) block data having an encrypted block length is generated from the extracted block character string data. The encrypted block length is a predetermined data length that is equal to or greater than the maximum data length of the block character string. The encryption processing unit 63 encrypts the block data obtained by the block data generation unit 62 by a block encryption method that performs encryption in units of encrypted block length. The encryption data generation unit 64 combines encrypted block data corresponding to a plurality of block character strings obtained from the encryption target character string, and generates encryption data for the encryption target character string.

  As a result, block data containing a block character string with multiple character lengths is block-encrypted with a sufficient encryption block length, so that the encryption strength that can withstand practical use can be secured and partial matching search is possible. Data can be generated and used in a database by the database server 21.

Embodiment 2. FIG.

  The system according to Embodiment 2 of the present invention is such that the gateway 2 has the function of the proxy device 5 and the back-end side proxy device 5 is omitted. That is, in this system, the gateway 2 is an embodiment of the encryption device of the present invention.

  Therefore, in the second embodiment, the registration command, search command, and response data that pass through the gateway 2 are processed in the same manner as in the first embodiment. In the second embodiment, the data management unit 13 directly accesses the database server 21.

Embodiment 3 FIG.

  The system according to Embodiment 3 of the present invention is such that the user-side gateway 7 or the user terminal device 6 has the function of the proxy device 5 and the back-end side proxy device 5 is omitted. That is, in this system, the gateway 7 or the user terminal device 6 is an embodiment of the encryption device of the present invention.

  Therefore, in the third embodiment, the registration command, the search command, and the response data that pass through the gateway 7 are processed in the same manner as in the first embodiment, or the registration command, the search command, and When response data is transmitted, the registration command, search command, and response data are processed in the same manner as in the first embodiment. In the third embodiment, the data management unit 13 directly accesses the database server 21.

  Each embodiment described above is a preferred example of the present invention, but the present invention is not limited to these, and various modifications and changes can be made without departing from the scope of the present invention. It is.

  For example, in the first to third embodiments, the block data generation unit 62 may generate block data from character string data by a reversible conversion formula instead of padding. In that case, the plaintext data generation unit 74 performs reverse operation of the conversion formula to extract a character string from the block data.

  In the first to third embodiments, the block data generation unit 62 may insert padding before a character string or between characters.

  In the first to third embodiments, only a character string having a length equal to or longer than two characters (= character length of a block character string) among character strings to be encrypted is encrypted as described above. It may be. However, in that case, if the encryption target is a character string of 2 characters (= character length of the block character string), the search is an exact match. Therefore, the encryption target is substantially a character string of 3 characters or more. Partial match search is possible for some cases.

  In the first to third embodiments, the character to be encrypted is a 1-byte character or a 2-byte character, but a 3-byte character or a 4-byte character may be usable. In this case, since usable character codes are determined in advance, the data length of one character, and hence the maximum data length of the block character string, may be specified according to the character code.

  In the first to third embodiments, block end characters are selected in order from the beginning of the encryption target character string to the (character length of the encryption target character string−character length of the block character string + 1) -th character. Instead, block end characters are selected in order from the "character length of the block character string" th character to the last character of the character string to be encrypted, and from the block end character to the character to be encrypted. A character string of “character length of block character string” continuous in the head direction of the column may be used as a block character string.

  In this case, for example, for the character string 101 “Shinjuku-ku, Tokyo” shown in FIG. 6, if the character length of the block character string is two characters, “Kyo”, “Miyako”, “New” are used as block end characters. "Tokyo", "Kyoto", "Toshin", "Shinjuku", and "Yukujuku" are extracted as block character strings. That is, in the first to third embodiments, the block end character is the character at the front end of the block character string. However, the block end character may be the end character of the block character string.

  In the first to third embodiments, block end characters are selected in order from the beginning of the encryption target character string to the (character length of the encryption target character string−character length of the block character string + 1) -th character. Instead, block end characters are selected in reverse order from the last character of the character string to be encrypted to the character length of the “character length of the block character string”. A character string of “character length of a block character string” continuous in the head direction of the character string may be a block character string.

  In this case, for example, for the character string 101 “Shinjuku-ku, Tokyo” shown in FIG. 6, assuming that the character length of the block character string is two characters, “ku”, “inn”, “new” , “Miyako”, and “Kyo” are selected, and “Yado Ward”, “Shinjuku”, “Toshin”, “Kyoto”, and “Tokyo” corresponding to them are extracted as block character strings. In this case, the block end character is the end character of the block character string. In addition, the order of the characters in the block character string may be reversed as “kuyadojuku”, “yukushin”, “shinto”, “tokyo”, and “kyoto” (in this case, the block end character is , The first character of the block string).

  In the first to third embodiments, block end characters are selected in order from the beginning of the encryption target character string to the (character length of the encryption target character string−character length of the block character string + 1) -th character. Instead, block end characters are selected in reverse order from the character to be encrypted (character length of the character string to be encrypted-character length of the block character string +1) to the first character. A character string of “character length of the block character string” continuous from the block end character toward the end of the character string to be encrypted may be used as the block character string.

  In this case, for example, for the character string 101 “Shinjuku-ku, Tokyo” shown in FIG. 6, if the block character string has a character length of two characters, “inn”, “new”, “to” , “Kyo”, and “East” are selected, and “Yuku Ward”, “Shinjuku”, “Toshin”, “Kyoto”, and “Tokyo” corresponding to them are extracted as block character strings. In this case, the block end character is the leading character of the block character string. In addition, the order of the characters in the block character string may be reversed as “kuyadojuku”, “yukushin”, “shinto”, “tokyo”, and “kyoto” (in this case, the block end character is , The last character of the block string).

  In the first to third embodiments, the encryption program 41 is recorded on a portable recording medium, and the encryption program 41 is transferred from the recording medium to the proxy device 5, the gateway 2, the gateway 7, the user terminal device 6, and the like. Alternatively, the encryption program 41 may be downloaded from a server on the network 3 and installed in the proxy device 5, the gateway 2, the gateway 7, the user terminal device 6, and the like.

  The present invention can be applied to, for example, encryption of user data in cloud computing.

2,7 Gateway (an example of an encryption device)
5 Proxy device (an example of an encryption device)
6 User terminal device (an example of an encryption device)
DESCRIPTION OF SYMBOLS 41 Encryption program 53 Decryption part 61 Encryption object specific | specification part 62 Block data generation part 63 Encryption process part 64 Encryption data generation part 72 Encryption block data extraction part 73 Decryption process part 74 Plain text data generation part 103-1 to 103-5 Block character string 104-1 to 104-5 Block data 106 Encrypted data 201 Search key

Claims (7)

(A1) sequentially select one character at a time from the character string to be encrypted that is one of the search target character string and the search key for which encrypted data is generated by the same method, and (a2) from the selected character A continuous character string having a plurality of character lengths is extracted from the encryption target character string as a block character string, and (a3) an encrypted block having a length equal to or greater than the maximum data length of the block character string from the extracted block character string data A block data generator for generating block data having a length;
An encryption processing unit that encrypts the block data obtained by the block data generation unit in a block encryption method that performs encryption in units of the encrypted block length;
An encrypted data generation unit that generates encrypted data for the encryption target character string by combining the encrypted block data corresponding to the plurality of block character strings obtained from the encryption target character string;
An encryption device comprising:   Get the encryption target information that specifies the database table and the columns in the table as the encryption target, and when registering the record in the database, the character of the column specified by the encryption target information in the record The encryption apparatus according to claim 1, further comprising: an encryption target specifying unit that specifies a string as the encryption target character string.   3. The encryption apparatus according to claim 2, wherein the encryption target specifying unit specifies a search key to be the encryption target character string based on the encryption target information when searching in the database. . A decrypting unit for decrypting encrypted data of a column designated by the encryption target information in a record hit at the time of searching in the database;
The decoding unit
An encryption block data extraction unit for extracting a plurality of encryption block data of the encryption block length from the encryption data;
A decryption processing unit for decrypting the encrypted block data with a decryption method corresponding to the encryption method of the encryption processing unit;
(B1) Each of the block character strings is extracted from the data obtained by decryption by the decryption processing unit from the plurality of encrypted block data, and (b2) plaintext data for the encrypted data from the extracted plurality of block character strings. A plaintext data generation unit for generating
The encryption device according to claim 3. The encrypted block length is a predetermined data length longer than the maximum data length of the block character string,
The block data generation unit generates the block data by padding the block character string data;
The encryption device according to any one of claims 1 to 4, wherein: The block string has a character length of 2 characters,
The block encryption method of the encryption processing unit is a common key encryption method that is not a substitution encryption,
The encryption device according to claim 1, wherein: Computer
(A1) sequentially select one character at a time from the character string to be encrypted that is one of the search target character string and the search key for which encrypted data is generated by the same method, and (a2) from the selected character A continuous character string having a plurality of character lengths is extracted from the encryption target character string as a block character string, and (a3) an encrypted block having a length equal to or greater than the maximum data length of the block character string from the extracted block character string data A block data generator for generating block data having a length;
In a block encryption method that performs encryption in units of the encrypted block length, an encryption processing unit that encrypts the block data obtained by the block data generation unit, and a plurality of strings obtained from the encryption target character string An encryption program that functions as an encryption data generation unit that combines the encrypted block data corresponding to the block character string to generate encryption data for the encryption target character string.

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