JP6806433B2 - Key management system, key management device, key management method, and program - Google Patents

Description

The present invention relates to a key management system, a key management device, a key management method, and a program.

In recent years, information terminal devices such as smartphones have become widespread, and the importance of security technology for preventing unauthorized access by a third party to files stored in the information terminal device is increasing. One such security technology is file encryption. In file encryption, if all files are encrypted with one encryption key, if the encryption key is leaked to a third party, all the files will be accessible by the third party. Therefore, in order to ensure high security, it is desirable that the files are encrypted with a different encryption key for each file. Further, if the encryption key and the encrypted file are stored in the same information terminal device, the security risk when the encryption key is stolen increases. Therefore, the encryption key is stored in a different information terminal device, for example, a management server. Is common. However, in that case, since the number of encryption keys increases as the number of files increases, the security management cost related to the management of the encryption key in the key management server increases.

Therefore, for example, the file encryption system described in Patent Document 1 first encrypts a file with a random number generated randomly for each file to generate a ciphertext file, and further encrypts the random number with a common encryption key. Generate a ciphertext key. Then, the file encryption system stores the ciphertext key and the encrypted file together. As a result, the file encryption system secures the same level of security as when a file is encrypted with a different encryption key for each file by managing only one encryption key.

Japanese Unexamined Patent Publication No. 10-260903

By the way, in order to prevent unauthorized access to a file, in addition to file encryption, access control may be performed based on the setting of access authority to the file. Access control is performed using, for example, access right information in which a user who can access the file, an application that can access the file, and the like are defined for each file, for example, ACL (Access Control List). This allows only specific users or specific applications to access the file.
However, in that case, new security management costs may be incurred, such as the need to take measures to prevent unauthorized access to the access right information.

The present invention has been made in view of the above points, and provides a key management system, a key management device, a key management method, and a program capable of reducing security management costs while ensuring security.

(1) The present invention has been made to solve the above problems, and one aspect of the present invention is a scope which is an encryption key for encrypting a file key which is an encryption key used for encrypting a file. A storage unit that stores a key management table that defines the conditions under which the key can be used for each scope key, and a first control unit that generates the scope key and transmits the scope key that satisfies the condition to the terminal device. A key management device including, a second control unit that encrypts the file key with the scope key obtained from the key management device, and the file encrypted with the file key and encrypted with the scope key. It is a key management system characterized by having the terminal device including a file storage unit that stores the encrypted file key in association with each other.

(2) Further, as one aspect of the present invention, the key management system according to (1) is characterized in that the user authentication is performed by an identifier representing a specific user. ..

(3) Further, as one aspect of the present invention, the condition is characterized in that an application included in an application group consisting of at least one application uses the file (1) or (2). ) Is the key management system described in.

(4) Further, as one aspect of the present invention, the first control unit generates a device key, which is a different encryption key for each terminal device, and transmits the device key to the terminal device, and the second control unit. Is the key management system according to any one of (1) to (3), wherein the scope key is encrypted by the device key obtained from the key management device.

(5) Further, as one aspect of the present invention, a key that defines conditions for using a scope key, which is an encryption key for encrypting a file key, which is an encryption key used for encrypting a file, for each scope key. The key management device is characterized by including a storage unit that stores a management table and a control unit that generates the scope key and transmits the scope key satisfying the above conditions to the terminal device.

(6) Further, one aspect of the present invention is a key management method in a key management system including a key management device which is a computer and a terminal device which is a computer, and a storage unit included in the key management device is a file. The key management device includes a storage step for storing a key management table that defines conditions for using a scope key, which is an encryption key for encrypting a file key, which is an encryption key used for encryption, for each scope key. The first control step in which the control unit generates the scope key and transmits the scope key satisfying the above conditions to the terminal device, and the control unit included in the terminal device is the scope obtained from the key management device. The second control step of encrypting the file key with the key corresponds to the file storage unit included in the terminal device corresponding to the file encrypted by the file key and the file key encrypted by the scope key. It is a key management method characterized by having a file storage step of attaching and storing.

(7) Further, as one aspect of the present invention, in a key management system including a key management device and a terminal device, a file key, which is an encryption key used for encrypting a file, is encrypted on the computer of the key management device. A storage step for storing a key management table that defines conditions for using a scope key, which is an encryption key, for each scope key, and a scope key that generates the scope key and transmits the scope key that satisfies the condition to the terminal device. A second control step of causing the computer of the terminal device to execute the first control step and encrypting the file key with the scope key obtained from the key management device, and encryption with the file key. A program for executing a file storage step of associating and storing the file and the file key encrypted by the scope key.

According to the present invention, security management costs can be reduced while ensuring security.

It is a schematic diagram which shows the outline of the key management system which concerns on this embodiment. It is a block diagram which shows the functional structure of the key management apparatus in the key management system which concerns on this embodiment. It is a block diagram which shows the functional structure of the terminal apparatus in the key management system which concerns on this embodiment. It is a schematic diagram which shows an example of the data stored in the generation file storage part of the terminal apparatus in the key management system which concerns on this embodiment. It is a schematic diagram which shows the file encryption processing in the key management system which concerns on this embodiment. It is a sequence diagram which shows the flow of distribution of the encryption key in the key management system which concerns on this Embodiment. It is a sequence diagram which shows the flow of distribution of the encryption key in the key management system which concerns on this Embodiment. It is a figure which shows an example of the structure of the key management table stored in the key storage part of the key management device in the key management system which concerns on this embodiment.

(Embodiment)
Hereinafter, embodiments according to the present invention will be described with reference to the drawings.
FIG. 1 is a schematic diagram showing an outline of the key management system 1 according to the present embodiment.
The key management system 1 includes a key management device 10 and a terminal device 20.
The key management device 10 communicates with at least one terminal device 20 via a communication network, and generates and manages various encryption keys used when a file stored in the terminal device 20 is encrypted. It is a server device. The key management device 10 includes, for example, a general-purpose computer or a personal computer.

Further, the communication network connecting the key management device 10 and the terminal device 20 is configured to include, for example, a dedicated line or the Internet. The communication network may be any of a wireless communication network, a wired communication network, and a communication network that combines wireless communication and wired communication. Further, the communication network may include a relay base station such as a wireless communication base station.

The terminal device 20 is a terminal device used by the user and stores various files. The various files are, for example, text files, audio files, video files, program files, and the like. The terminal device 20 includes, for example, a portable terminal device such as a smartphone, a personal computer, or the like.

(Configuration of key management device)
Next, the configuration of the key management device 10 according to the present embodiment will be described with reference to the drawings.
FIG. 2 is a block diagram showing a functional configuration of the key management device 10 in the key management system 1 according to the present embodiment.
The key management device 10 includes a control unit 100, a communication unit 101, a random number generation unit 102, a temporary storage unit 103, and a key storage unit 104.

The control unit 100 (first control unit) controls various processes of the key management device 10. The control unit 100 includes, for example, a CPU (Central Processing Unit; central processing unit).
The communication unit 101 is a communication interface for communicating with at least one terminal device 20.
The random number generation unit 102 generates pseudo-random numbers for generating various encryption keys. The random number generation unit 102 includes, for example, a RAM that is a temporary storage area in which an algorithm for generating pseudo-random numbers is executed.

The temporary storage unit 103 temporarily stores the generated encryption key and the like. The temporary storage unit 103 includes a storage medium, for example, a RAM (Random Access read / write memory; readable and writable memory).
The key storage unit 104 stores the generated encryption key and the like. Further, the key storage unit 104 stores a key management table, which is a table for associating an encryption key with information used for managing the encryption key. The key storage unit 104 includes a storage medium, for example, a hard disk drive (HDD; Hard Disk Drive).

(Configuration of terminal device)
Next, the configuration of the terminal device 20 according to the present embodiment will be described with reference to the drawings.
FIG. 2 is a block diagram showing a functional configuration of the terminal device 20 in the key management system 1 according to the present embodiment.
The terminal device 20 includes a control unit 200, a communication unit 201, a random number generation unit 202, a temporary storage unit 203, a key storage unit 204, and a file storage unit 205.

The control unit 200 (second control unit) controls various processes of the terminal device 20. The control unit 200 includes, for example, a CPU.
The communication unit 201 is a communication interface for communicating with the key management device 10.
The random number generation unit 202 generates a random number for generating an encryption key called a file key, which will be described later. The random number generation unit 202 is configured to include, for example, a RAM which is a temporary storage area in which an algorithm for generating a pseudo-random number is executed.

The temporary storage unit 203 temporarily stores the generated encryption key and the like. The temporary storage unit 203 includes a storage medium, for example, a RAM.
The key storage unit 204 stores the generated encryption key and the like. The key storage unit 204 includes a storage medium, for example, an HDD.

The file storage unit 205 stores various files and metadata stored in pairs with each file. The metadata is data including information related to a file stored as a pair with the metadata. The metadata includes, for example, data indicating an encryption key used when a file stored as a pair with the metadata is encrypted. The file storage unit 205 includes a storage medium, for example, an HDD.

(Overview of data stored in the terminal device)
Next, an outline of the data stored in the file storage unit 205 of the terminal device 20 will be described with reference to the drawings.
FIG. 4 is a schematic diagram showing an example of data stored in the file storage unit 205 of the terminal device 20 in the key management system 1 according to the present embodiment.

Although not shown in FIG. 4, the file stored in the file storage unit 205 is first encrypted with an encryption key called a file key when it is newly stored in the file storage unit 205. The file key is generated by the control unit 200 using the random numbers generated by the random number generation unit 202. That is, when the control unit 200 newly stores the file in the file storage unit 205, the control unit 200 encrypts the file with the file key and then stores the file in the file storage unit 205.

The file key is a different key for each file to be encrypted, and is managed by the terminal device 20. Since the file key is an encryption key generated for each file, the number of file keys increases as the number of files increases. Therefore, the file key is an encryption key whose number may increase and the security management cost related to the management of the file key may increase. However, since the file key is generated and managed by the control unit 200 in each terminal device 20, the key management device 10 does not incur a security management cost for managing the file key.
An encryption key other than the file key, for example, a user key, an application key, a global key, a device key, and the like, which will be described later, is generated and managed by the control unit 100 of the key management device 10.

Of the files stored in the file storage unit 205 of the terminal device 20 illustrated in FIG. 4, in order to decrypt the file belonging to the data group i01, the file is decoded using the user key ukey1 which is the user key of the user A. Need to be. The user key is an encryption key generated for each user, that is, in association with a user ID (identifier) that identifies the user. For example, when the user A logs in to the terminal device 20 (user is authenticated), the file included in the data group i01 can be decrypted by the user key ukey1 which is the user key of the user A. When a user other than the user A logs in to the terminal device 20 (user authentication is performed), the file included in the data group i01 is not decrypted.
That is, the file belonging to the data group i01 is a file that can be decrypted when the user A logs in to the terminal device 20.

Although the details will be described later, the file belonging to the data group i01 is encrypted with the file key, and the file key is encrypted with the user key ukey1 which is the user key of the user A. Therefore, the file key is decrypted using the user key ukey1, and the file is decrypted by the decrypted file key, so that the file belonging to the data group i01 is decrypted.

Similarly, in order to decrypt the file belonging to the data group i02, it is necessary to decrypt using the user key ukey2 which is the user key of the user B. The file belonging to the data group i02 is a file that can be decrypted when the user B logs in to the terminal device 20 (user authentication).

For example, when the terminal device 20 is authenticated by the user ID corresponding to the user A, the file belonging to the data group i01 can be decrypted by distributing the user key ukey1 which is the user key of the user A. .. On the other hand, in that case, the file belonging to the data group i02, which needs to use the user key ukey2 which is the user key of the user B in order to decrypt the file, is not decrypted.

Further, in order to decrypt the file belonging to the data group i03, it is necessary to decrypt using the application group key application1 which is the application group key of the application group 1. The file belonging to the data group i03 is a file that can be decrypted only when accessed from the application belonging to the application group 1.

The application referred to here is an application used by the user in the terminal device 20, for example, an application such as a web browser, a file viewer, or a mailer. An application group is a set of applications that includes at least one application.
For example, if application group 1 contains only two applications, a web browser and a file viewer, the files belonging to the data group i03 are decrypted only when accessed from the web browser or file viewer, and are decrypted by the application. Can be used.

Similarly, in order to decrypt a file belonging to the data group i04, it is necessary to decrypt using an encryption key called the application group key application2, which is the application group key of the application group 2. The file belonging to the data group i04 is a file that can be decrypted only when accessed from the application belonging to the application group 2.

Further, in order to decode the file belonging to the data group i05, it is necessary to decrypt using the global key gkey1. The global key gkey1 is an encryption key distributed to all users who log in to the terminal device 20 (user authentication) and all applications included in the terminal device 20. That is, the file belonging to the data group i05 is a file that can be decrypted regardless of which user uses the terminal device 20 or which application of the terminal device 20 accesses it.

Further, as shown in FIG. 4, files belonging to each data group (data group i01, data group i02, ..., Data group i05 in FIG. 4) are stored as a pair with metadata described later. .. The metadata is further encrypted by the device key dkey1. The device key is an encryption key generated for each terminal device 20. Details will be described later.

Further, in FIG. 4, the data group i01 includes a data group i11 that can be decrypted by using an encryption key called a binding key upkey1 which is a binding key between the user A and the application group 1. The file belonging to this data group i11 is a file that can be decrypted only when the user A logs in to the terminal device 20 (user authentication) and is accessed from the application belonging to the application group 1.
Similarly, the data group i01 includes a data group i12 that can be decoded by using the binding key upkey2 which is the binding key of the user A and the application group 2. The file belonging to this data group i12 is data that is used by user A and can be decrypted only when accessed by an application belonging to application group 2.

As described above, the combined key of the user and the application group is an encryption key having an effect of setting an access restriction combining the access restriction by the user key and the access restriction by the application group key. That is, when the file is encrypted using the combined key of the user and the application group, the access restriction equivalent to that when the file is encrypted with the user key and then further encrypted with the application group key is provided. become.

By using a binding key that combines a plurality of encryption keys, the key management device 10 originally realizes access control that can be realized by a plurality of encryption keys (for example, a user key and an application group key) with one encryption key. It is possible to reduce the number of encryption keys to be managed. As a result, the security management cost for managing the encryption key in the key management device 10 is reduced.

As described above, the file key used for encrypting the file stored in the file storage unit 205 of the terminal device 20 is a different encryption key (user key, application group key) for each data group to which the file belongs. , Global key, or user-application binding key) must be decrypted.
In the following description, the user key, the application group key, the global key, and the user-application combination key may be collectively referred to as a "scope key".

(File encryption process)
Next, the file encryption process in the key management system 1 according to the present embodiment will be described with reference to the drawings.
FIG. 5 is a schematic diagram showing a file encryption process in the key management system 1 according to the present embodiment.
First, when a new file is newly stored (saved) in the terminal device 20, the control unit 200 of the terminal device 20 generates a file key based on the random number generated by the random number generation unit 202 (FIG. 5, S001). ).

The file key is generated based on a random number generated by the random number generation unit 102 provided in the key management device 10, generated by the control unit 100, and transmitted (distributed) to the terminal device 20 via the communication unit 101. It does not matter if the configuration is such that. That is, the file key may be generated by the key management device 10 and managed by the terminal device 20, respectively.

Further, the control unit 100 generates an initialization vector based on the random numbers generated by the random number generation unit 102 (FIG. 5, S002). The control unit 100 transmits the initialization vector to the terminal device 20 in which the file is newly stored in the above via the communication unit 101.

Further, the control unit 100 generates a Mac (Message Authentication Code; message authentication code) key based on the random number generated by the random number generation unit 102 (FIG. 5, S003). The control unit 100 transmits the Mac key to the terminal device 20 in which the file is newly stored, via the communication unit 101. The Mac key is an encryption key used to generate an output value (Mac value) in message authentication, which is a technique for guaranteeing data integrity.

The control unit 200 of the terminal device 20 encrypts the file key generated above with the scope key described above (FIG. 5, S004). The scope key is generated in advance by the control unit 100 of the key management device 10, and is distributed to the terminal device 20 via the communication unit 101. Details will be described later.

The terminal device 20 control unit 200 encrypts the newly stored file in the above with the file key and the initialization vector (FIG. 5, S005). As the encryption method, for example, AES256 using an encryption key having a length of 256 bits is used.

The terminal device 20 generates a Mac value by performing arithmetic processing on the newly stored file in the above by the Mac algorithm using the Mac key (FIG. 5, S006). For the Mac algorithm, for example, HmacSHA2 is used.

The terminal device 20 applies the metadata corresponding to the newly stored file (that is, the data including the file key encrypted by the scope key, the initialization vector, the Mac value, the Mac key, and the like) to the device described above. It is encrypted with a key (Fig. 5, S007). As the encryption method, for example, AES256 using an encryption key having a length of 256 bits is used.

The terminal device 20 stores the file encrypted by the file key and the metadata encrypted by the device key in the file storage unit 205 included in the terminal device 20. As described above, the metadata includes the file key encrypted by the scope key.

(Operation of key management system in distribution of encryption key)
Next, the flow of distributing the encryption key will be described with reference to the drawings.
6 and 7 are sequence diagrams showing the flow of distribution of the encryption key in the key management system 1 according to the present embodiment.
First, data indicating an authentication request is transmitted from the terminal device 20 to the key management device 10 (FIG. 6, S101). The data indicating the authentication request is transmitted, for example, when the user logs in (user is authenticated) in the terminal device 20.

The control unit 100 of the key management device 10 generates a master key based on the random numbers generated by the random number generation unit 102 (FIG. 6, S102). The master key is an encryption key used when the terminal device 20 is offline (that is, not connected to the key management device 10 by communication). The master key is used to encrypt the offline key list described later. In this example, the case where the terminal device 20 is used online and the case where the terminal device 20 is used offline (the communication connection with the key management device 10 is disconnected) will be described.

The control unit 100 of the key management device 10 generates a password-based key by using the data of the user password (password used for user authentication) included in the data indicating the above authentication request (FIG. 6, S103). .. The password-based key is generated by, for example, PBKDF2, which is one of the means for generating an encryption key.

The control unit 100 of the key management device 10 encrypts the master key with the password-based key (FIG. 6, S104).
The control unit 100 of the key management device 10 stores the master key of the key management device 10 and the master key encrypted by the above password-based key in the key storage unit 104 (FIG. 6, S105).

The control unit 100 of the key management device 10 transmits data indicating an authentication response to the terminal device 20 via the communication unit 101 (FIGS. 6, S106).
The terminal device 20 acquires the device ID, the user ID, and the key version from the file storage unit 205 of its own terminal device 20 (FIG. 6, S107). The key version indicates the version of the encryption key by updating the encryption key when the encryption key has an expiration date.
The terminal device 20 transmits data indicating a request for the online key list to the key management device 10 (FIG. 6, S108). The data indicating the request for the online key list includes data indicating the device ID, the user ID, and the key version.

The control unit 100 of the key management device 10 acquires an online encryption key from the key storage unit 104. The online encryption key includes a scope key. If the online encryption key is not stored in the key storage unit 104, the control unit 100 newly generates an online encryption key.
The control unit 100 of the key management device 10 generates an online key list, which is a list of acquired online encryption keys (FIG. 6, S109).

The control unit 100 of the key management device 10 acquires an offline encryption key from the key storage unit 104. When the offline encryption key is not stored in the key storage unit 104, the control unit 100 newly generates an online encryption key. The encryption key included in the list of offline encryption keys may be the same encryption key as the encryption key (scope key) included in the list of online encryption keys.
The control unit 100 of the key management device 10 generates an offline key list, which is a list of acquired offline encryption keys (FIG. 6, S110).

The control unit 100 of the key management device 10 acquires the master key from the key storage unit 104.
The control unit 100 of the key management device 10 encrypts the generated offline key list with the master key (FIG. 6, S111).

The control unit 100 of the key management device 10 stores the offline key list encrypted with the master key in the key storage unit 104 (FIG. 6, S112).
The control unit 100 of the key management device 10 transmits an online key list to the terminal device 20 via the communication unit 101 (FIGS. 6, S113). The online key list includes scope keys (ie, user keys, application group keys, global keys, and user-application group combined keys, etc.).

The terminal device 20 stores the online encryption key (scope key) included in the acquired online key list in the temporary storage unit 203 of its own terminal device 20 (FIGS. 6, S114).

As described above, the same scope key is stored in the temporary storage unit 103 of the key management device 10 and the temporary storage unit 203 of the terminal device 20. As a result, the terminal device 20 can decrypt and use the encrypted file by using the scope key generated by the key management device 10. Further, by using the scope key associated with each file group for encryption and decryption, the terminal device 20 can use the file only by the user who has the access authority to the file and the application group which has the access authority. Access control can be performed in this way.

Next, the terminal device 20 transmits data indicating a request for the offline key list to the key management device 10 (FIG. 7, S115). The data indicating the request for the offline key list includes the device ID and the data indicating the user ID.
The control unit 100 of the key management device 10 acquires the offline key list encrypted with the master key and the master key encrypted with the password-based key from the key storage unit 104 (FIG. 7, S116).

The control unit 100 of the key management device 10 transmits the offline key list encrypted with the master key and the master key encrypted with the password base key to the terminal device 20 via the communication unit 101 (FIG. 7, FIG. S117).
The control unit 100 of the key management device 10 deletes the master key, the master key encrypted with the password-based key, and the offline key list encrypted with the master key from the key storage unit 104 (FIG. 7, S118). ). In this way, the control unit 100 of the key management device 10 transmits all the offline encryption keys necessary for decrypting the file in the offline case to the terminal device 20, and sends them to the key storage unit 104 of the key management device 10. Delete all stored offline encryption keys. As a result, the offline encryption key is not leaked from the key management device 10, so that security can be improved.

The terminal device 20 stores the offline key list encrypted with the acquired master key and the master key encrypted with the password-based key in the temporary storage unit 203 of its own terminal device 20 (FIG. 6, S119). ..

As described above, the control unit 200 of the terminal device 20 is a password in which the master key encrypted with the password-based key is input by the user from the input unit (not shown) of the terminal device 20 even in the offline state. Can be decrypted by. Further, the control unit 200 can decrypt the offline key list encrypted with the master key by using the decrypted master key. As a result, the terminal device 20 is in an offline state (a state in which the communication connection between the key management device 10 and the terminal device 20 is disconnected) after acquiring the offline key list from the key management device 10. Even if it becomes, the file encrypted by using the encryption key (for example, the scope key) included in the offline key list can be used.

(Structure of key management table)
Next, the configuration of the key management table stored in the key storage unit 104 of the key management device 10 will be described with reference to the drawings.
FIG. 8 is a diagram showing an example of the configuration of the key management table stored in the key storage unit 104 of the key management device 10 in the key management system 1 according to the present embodiment.
As shown in the figure, the key management table includes "device ID", "user ID", "scope ID", "group ID", "expiration flag", "key version", and "expiration date". , And a two-dimensional tabular data consisting of columns containing at least eight items of "key value". Each row in the key management table represents information about each encryption key.

In the item of "device ID", an identifier for uniquely identifying the device (that is, identifying which terminal device 20 is) is stored.
In the item of "user ID", an identifier that uniquely identifies a user who logs in to the terminal device 20 is stored.
In the item of "scope ID", a number indicating what kind of encryption key the scope key is is stored. In this example, the number "1" is stored if the encryption key is a global key, "2" if it is a user key, or "3" if it is an application group key.
In the "Group ID" item, only when the encryption key is the application group key (that is, when the value of the "scope key" is "3" in the above example), which application group it is. The indicated number is stored.

In the item of "expiration flag", a value indicating whether or not the encryption key has expired is stored. In this example, the value of "True" is stored when the expiration date has expired, and the value of "False" is stored when the expiration date has not expired.
In the "key version" item, a version number indicating the encryption key version is stored.
Data indicating the expiration date of the encryption key is stored in the "expiration date" item. For example, if the expiration date of the encryption key is "January 1, 2016", the value "20160101" is annoying.
The value of the encryption key (encryption key itself) is stored in the item of "key value".
In this way, the conditions under which the scope key can be used are defined in the key management table for each scope key. The key management device 10 transmits the scope key satisfying this condition and the information regarding the scope key to the terminal device 20 based on the information indicating the authentication request transmitted from the terminal device 20.

For example, each item of the first data row in the key management table shown in FIG. 8 has "asdfghj", "-", "1", "-", "False", "1", "20160101", respectively. And the value "0x186A593F264B59C6" is stored. In addition, when the value is "-", it means that there is no value (Null).

The value of the item of "device ID", "asdfghj", indicates that the data in this line is the data about the encryption key used in the terminal device 20 to which the device ID "asdfghj" is assigned.
"1" which is the value of the item of "scope ID" indicates that the data of this line is the data about the global key.

As described above, since the data is about the global key that is not limited to the user (used regardless of which user logs in), the value of the "user ID" item of the data in this line is "-". Further, since the data is about the global key that is not limited to the application (used regardless of which application accesses it), the value of the "group ID" item of the data in this row is "-".

"False", which is the value of the "expiration flag" item, indicates that the encryption key has not expired.
The value "1" of the "key version" item indicates that the version number of the encryption key is "1".

The value of the item of "expiration date", "20160101", indicates that the expiration date of the encryption key is "January 1, 2016".
The value of the item of "key value", "0x186A593F264B59C6", indicates that the value of the encryption key is "0x186A593F264B59C6".

As described above, the key management system 1 according to the present embodiment encrypts a file with a different file key for each file. As a result, even if the file key of one file is leaked to a malicious third party, the third party cannot decrypt any file other than the file corresponding to the leaked file key. Therefore, the key management system 1 according to the present embodiment can ensure higher security than the case where a plurality of files are encrypted with one file key.

Further, the key management system 1 according to the present embodiment encrypts a file key different for each file with a common scope key for each data group grouped based on the access authority. Then, the key management system 1 stores the file key encrypted with the scope key and the file as a pair in the terminal device 20. Therefore, the key management device 10 does not need to manage the file key, and may manage the scope key. As a result, the key management system 1 according to the present embodiment can reduce the number of keys managed by the key management device 10 as compared with the case where all the file keys generated for each file are managed, and thus security. Management costs can be reduced.

Further, the key management device 10 according to the present embodiment generates scope keys grouped based on access authority such as for each user and each application group. As a result, the key management device 10 can control the authority to decrypt the file (that is, control the access to the content contained in the file) by using the scope key. As a result, the key management device 10 does not need to separately create and manage an access control list such as an ACL, and does not need to perform processing for preventing unauthorized access to the access control list. Security management costs can be reduced compared to using lists.

As described above, according to the key management device 10 according to the present embodiment, it is possible to reduce the security management cost while ensuring the security.

Although the embodiments of the present invention have been described in detail above, the specific configuration is not limited to the above, and various design changes and the like can be made without departing from the gist of the present invention. is there.

A part or all of the key management device 10 and the terminal device 20 in the above-described embodiment may be realized by a computer. In that case, the program for realizing this control function may be recorded on a computer-readable recording medium, and the program recorded on the recording medium may be read by the computer system and executed.

The "computer system" referred to here is a computer system built in the key management device 10 and the terminal device 20, and includes hardware such as an OS and peripheral devices. Further, the "computer-readable recording medium" refers to a portable medium such as a flexible disk, a magneto-optical disk, a ROM, or a CD-ROM, or a storage device such as a hard disk built in a computer system.

Furthermore, a "computer-readable recording medium" is a medium that dynamically holds a program for a short period of time, such as a communication line when a program is transmitted via a network such as the Internet or a communication line such as a telephone line. In that case, a program may be held for a certain period of time, such as a volatile memory inside a computer system serving as a server or a client. Further, the above-mentioned program may be a program for realizing a part of the above-mentioned functions, and may be a program for realizing the above-mentioned functions in combination with a program already recorded in the computer system.

Further, the key management device 10 and the terminal device 20 in the above-described embodiment may be realized as an integrated circuit such as an LSI (Large Scale Integration). Each functional block of the key management device 10 and the terminal device 20 may be made into a processor individually, or a part or all of them may be integrated into a processor. Further, the method of making an integrated circuit is not limited to LSI, and may be realized by a dedicated circuit or a general-purpose processor. Further, when an integrated circuit technology that replaces an LSI appears due to advances in semiconductor technology, an integrated circuit based on this technology may be used.

1 ... Key management system, 10 ... Key management device, 20 ... Terminal device, 100 ... Control unit, 101 ... Communication unit, 102 ... Random number generation unit, 103 ... Temporary Storage unit, 104 ... key storage unit, 200 ... control unit, 201 ... communication unit, 202 ... random number generation unit, 203 ... temporary storage unit, 204 ... key storage unit, 205・ ・ ・ File storage

Claims (5)

An encryption key that encrypts a file key, which is an encryption key used to encrypt a file, in order to control access to one or more data groups to which the file belongs, and is at least a "global data group" or "with a user". The conditions under which the scope key that controls access to any of the "joined data group with the application group" can be used are defined for each scope key , and the "device ID" that uniquely identifies the device and the user are uniquely identified. A storage unit that stores a key management table including a "user ID" for identification, a "scope ID" for indicating what kind of encryption key the scope key is, and a "group ID" for indicating which application group .
A first control unit that generates the scope key and transmits the scope key satisfying the above conditions to the terminal device.
Key management device equipped with
A second control unit that encrypts the file key with the scope key obtained from the key management device, and
A file storage unit that stores the file encrypted by the file key and the file key encrypted by the scope key in association with each other.
The terminal device comprising
A key management system characterized by having. The first control unit generates a device key, which is a different encryption key for each terminal device, and transmits the device key to the terminal device.
The second control unit encrypts metadata including a file key encrypted by the scope key with the device key obtained from the key management device.
The key management system according to claim 1, wherein the key management system is characterized in that. An encryption key that encrypts a file key, which is an encryption key used to encrypt a file, in order to control access to one or more data groups to which the file belongs, and is at least a "global data group" or "with a user". The conditions under which the scope key that controls access to any of the "joined data group with the application group" can be used are defined for each scope key , and the "device ID" that uniquely identifies the device and the user are uniquely identified. A storage unit that stores a key management table including a "user ID" for identification, a "scope ID" for indicating what kind of encryption key the scope key is, and a "group ID" for indicating which application group .
A control unit that generates the scope key and transmits the scope key that satisfies the condition to the terminal device.
A key management device characterized by being equipped with. It is a key management method in a key management system consisting of a key management device that is a computer and a terminal device that is a computer.
The storage unit included in the key management device is an encryption key that encrypts a file key, which is an encryption key used for encrypting a file, in order to control access to a single or a plurality of data groups to which the file belongs, at least. The condition for using the scope key that controls access to either the "global data group" or the "joined data group between the user and the application group" is defined for each scope key , and the device is uniquely identified. A key management table including a "device ID" to be used, a "user ID" that uniquely identifies a user, a "scope ID" that indicates what kind of encryption key the scope key is, and a "group ID" that indicates which application group. And the memory step to memorize
A first control step in which the control unit included in the key management device generates the scope key and transmits the scope key satisfying the above conditions to the terminal device.
A second control step in which the control unit included in the terminal device encrypts the file key with the scope key obtained from the key management device.
A file storage step in which the file storage unit included in the terminal device stores the file encrypted by the file key and the file key encrypted by the scope key in association with each other.
A key management method characterized by having. In a key management system consisting of a key management device and a terminal device
To the computer of the key management device
An encryption key that encrypts a file key, which is an encryption key used to encrypt a file, in order to control access to one or more data groups to which the file belongs, and is at least a "global data group" or "with a user". The conditions under which the scope key that controls access to any of the "joined data group with the application group" can be used are defined for each scope key , and the "device ID" that uniquely identifies the device and the user are uniquely identified. A storage step that stores a key management table that includes a "user ID" to identify, a "scope ID" to indicate what type of encryption key the scope key is, and a "group ID" to indicate which application group .
The first control step of generating the scope key and transmitting the scope key satisfying the above conditions to the terminal device,
To execute,
To the computer of the terminal device
A second control step of encrypting the file key with the scope key obtained from the key management device, and
A file storage step of associating and storing the file encrypted by the file key and the file key encrypted by the scope key, and
A program to execute.

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