JP6792191B2 - Information transmission method, information processing method, program, decoding method, program - Google Patents

Description

The present invention relates to an information transmission method, an information processing method, a program, a decoding method, and a program, and more particularly to an information transmission method, an information processing method, a program, a decoding method, and a program for safely sharing information with an external user.

As one of the means for securely sharing information with external users, a method of encrypting file data is known.

For example, Patent Document 1 describes an example of a method of secretly sharing data. Specifically, according to Patent Document 1, the data is divided into two to generate one data and the other data. Then, the other data is encrypted multiple times using a plurality of pseudo-random numbers generated based on one data, and one data is encrypted multiple times using a plurality of pseudo-random numbers generated based on the other data. To become. According to Patent Document 1, the above configuration can prevent deterioration of safety even when data is divided into unequal sizes.

Further, as one of the techniques for storing the data stored in the client device in the storage device in order to ensure the confidentiality and recoverability of the data, for example, Patent Document 2 is provided. Patent Document 2 describes a first step of transmitting a write request including the first distributed information obtained by dividing the original data M by the secret sharing method to the storage server and deleting the first distributed information from itself. , A data protection method comprising a second step of transmitting a data write request including a second encrypted distributed information Epk in which the second distributed information is encrypted using a public key to a storage server is described. There is. According to Patent Document 2, the above configuration can provide data confidentiality and resilience at the same time.

Japanese Unexamined Patent Publication No. 2009-288616 Japanese Unexamined Patent Publication No. 2008-097591

For the purpose of more strongly concealing data, the data is secretly distributed by the method described in Patent Document 1, then further encrypted, and the encrypted data is sent to the storage device or the other party's device. May be sent. Here, when trying to transmit data to the other party by using the method described in Patent Document 2, in order to decrypt the data at the other party, obtain a key for decoding by some method. Is required.

As a key method, for example, there is a method of distributing a key for decrypting when authentication is passed through an authentication server. However, when this method is used, it is necessary to register the data sharing partner in the authentication server in advance. As a result, there are problems such as complicated operation and difficulty in sharing data requiring decryption with a partner who cannot be registered in the authentication server. On the other hand, if the key is shared by a method such as e-mail, the leakage of the e-mail enables a third party to decrypt the key, and there is a problem that the decryption cannot be noticed.

In this way, it was difficult to securely pass the key for decrypting the ciphertext to the other party. As a result, there has been a problem that it is difficult to prevent anyone other than the target party from decrypting the encrypted file without distributing the key to the data sharing partner in advance.

Therefore, an object of the present invention is an information transmission method for solving a problem that it is difficult to prevent a file encrypted by anyone other than the target party from being decrypted without distributing the key to the data sharing partner in advance. The purpose is to provide information processing methods, programs, decryption methods, and programs.

The information transmission method, which is one embodiment of the present invention, in order to achieve such an object
This is an information transmission method in which information is transmitted from the sending device to the receiving device via the management server.
The management server
The first ciphertext encrypted by the first encryption key is received from the sending device,
Receives state information from the receiving device, which is information indicating the state of the receiving device,
A configuration is adopted in which a second ciphertext created based on the received state information and a second ciphertext created based on the first ciphertext are transmitted to the receiving device.

Further, the information processing method which is another embodiment of the present invention is
Information processing method performed by the management server
The first ciphertext encrypted by the first encryption key is received from the external device,
Receives status information indicating the status of the receiving device,
A configuration is adopted in which a second ciphertext created based on the received state information and a second ciphertext created based on the first ciphertext are transmitted to the receiving device.

In addition, the program which is another form of the present invention
On the management server
The first ciphertext encrypted by the first encryption key is received from the external device,
Receives status information indicating the status of the receiving device,
In order to realize a process of transmitting a second ciphertext created based on the received second encryption key created based on the state information and the first ciphertext to the receiving device. It is a program of.

Moreover, the decoding method which is another form of this invention is
Status information, which is information indicating the status of the receiving device, is transmitted to the management server having the ciphertext to be decrypted.
A configuration is adopted in which a ciphertext encrypted based on an encryption key created based on the transmitted state information is acquired from the management server, and the acquired ciphertext is decrypted.

In addition, the program which is another form of the present invention
On the receiving device,
Status information, which is information indicating the status of the receiving device, is transmitted to the management server having the ciphertext to be decrypted.
This is a program for acquiring a ciphertext encrypted based on an encryption key created based on the transmitted state information from the management server and realizing a process of decrypting the acquired ciphertext.

The present invention has a problem that it is difficult to prevent a file encrypted by anyone other than the target party from being decrypted without distributing the key to the data sharing partner in advance due to the configuration as described above. It is possible to provide an information transmission method, an information processing method, a program, a decoding method, and a program to be solved.

It is a block diagram which shows an example of the structure of the information sharing system in 1st Embodiment of this invention. It is a block diagram which shows an example of the structure of the sending side apparatus shown in FIG. It is a block diagram which shows an example of the structure of the management server shown in FIG. It is a figure which shows an example of the content information stored in the content information storage part shown in FIG. It is a block diagram which shows an example of the structure of the receiving side apparatus shown in FIG. It is a figure which shows an example of the information which each configuration of an information sharing system has. It is a figure which shows an example of the processing flow when the sending side device secretly distributes the file M, encrypts it, and sends the encrypted file to a management server and a receiving side device. It is a figure which shows an example of the processing flow in the management server which received information from the sending side apparatus. It is a figure which shows an example of the information transmitted from the receiving side device to the management server. It is a figure which shows an example of the processing flow in the management server which received information from the receiving side apparatus. It is a figure which shows an example of the flow of the decoding process in the receiving side apparatus. It is a figure which shows an example of the process flow at the time of updating the information stored in the management server. It is a flowchart which shows an example (an example of the flow of the information transmission method) of the operation of the information sharing system in the 1st Embodiment of this invention. It is a flowchart which shows an example of the operation of the information sharing system in 1st Embodiment of this invention. It is a flowchart which shows an example of the operation of the information sharing system in 1st Embodiment of this invention. It is a figure which shows an example of the process flow at the time of not performing secret sharing. It is a figure which shows an example of the process flow at the time of not performing secret sharing. It is a block diagram which shows an example of the structure of the information sharing system in the 2nd Embodiment of this invention. It is a block diagram which shows an example of the structure of the management server in the 2nd Embodiment of this invention. It is a block diagram which shows an example of the structure of the receiving side apparatus in 2nd Embodiment of this invention.

[First Embodiment]
The first embodiment of the present invention will be described with reference to FIGS. 1 to 17. FIG. 1 is a block diagram showing an example of the configuration of the information sharing system 1. FIG. 2 is a block diagram showing an example of the configuration of the sending side device 11. FIG. 3 is a block diagram showing an example of the configuration of the management server 12. FIG. 4 is a diagram showing an example of content information 1261, which is information stored in the content information storage unit 126. FIG. 5 is a block diagram showing an example of the configuration of the receiving device 13. 6 to 12 are diagrams for explaining an example of the flow of the information transmission method performed by the information sharing system 1. 13 to 15 are flowcharts showing an example of the operation of the information sharing system 1 (that is, an example of the flow of the information transmission method). 16 and 17 are diagrams showing an example of a processing flow when secret sharing is not performed.

In the first embodiment of the present invention, the information sharing system 1 capable of safely transmitting information from the sending side device 11 to the receiving side device 13 will be described. The sending side device 11 in the present embodiment secretly distributes the file M, which is the information to be transmitted to the receiving side device 13, to the files M1 and M2, and then encrypts the file M1 and transmits the file M1 to the management server 12. , The file M2 is encrypted and transmitted to the receiving device 13. As will be described later, when the receiving side device 13 attempts to decrypt the file M2 received from the sending side device 11, the management server 12 stores information including state information (Im) which is information indicating the state of the receiving side device 13. Send to. Then, the receiving device 13 receives the file M1 encrypted with the encryption key created based on the state information (Im) from the management server 12. After that, the receiving device 13 receives the encrypted file M2 received from the source device 11 and the encrypted file M1 received from the management server 12, and the file M is the original data to be secretly distributed. To decrypt.

FIG. 1 shows an example of the overall configuration of the information sharing system 1 described in the present embodiment. Referring to FIG. 1, the information sharing system 1 has a sending side device 11, a management server 12, and a receiving side device 13.

As shown in FIG. 1, the sending device 11 and the management server 12 are connected so as to be able to communicate with each other via the network 14. Further, the management server 12 and the receiving device 13 are connected so as to be able to communicate with each other via the network 14. Similarly, the sending side device 11 and the receiving side device 13 are connected so as to be able to communicate with each other via the network 14.

The sending device 11 is, for example, an information processing device such as a personal computer or a tablet device. The sending device 11 has information to be sent to the receiving device 13 (for example, a file M), and the file M, which is the information to be sent, is secretly distributed and then encrypted. , The secretly distributed and then encrypted information is transmitted to the management server 12 and the receiving device 13. Further, the sending side device 11 has a password (Pw) used when creating an encryption key (K) described later and an e-mail address (ML_b) of the receiving side device 13.

FIG. 2 is an example of the configuration of the sending side device 11. Referring to FIG. 2, the sending device 11 includes a transmitting / receiving means 111, a distributed processing means 112, an encryption key creating means 113, an encryption means 114, and an information storage unit 115.

The sending side device 11 has an arithmetic unit such as a CPU (Central Processing Unit) and a storage device (not shown). The sending side device 11 realizes each of the above means by, for example, the arithmetic unit executing a program included in the storage device.

The transmission / reception means 111 transmits / receives information to / from the management server 12 and the receiving device 13. The information transmitted to the management server 12 via the transmission / reception means 111 includes, for example, an encrypted encryption key P_sv (K), an encrypted file K (M1), and an email address (ML_b) of the receiving device 13. and so on. Further, the information received from the management server 12 via the transmission / reception unit 111 includes, for example, a public key (P_sv). The information transmitted to the receiving device 13 via the transmission / reception unit 111 includes, for example, an encrypted file K (M2) and a password (Pw). The details of various information transmitted and received by the transmission / reception means 111 will be described later.

The distributed processing means 112 (second distributed processing means) secretly distributes the information to be sent. For example, the distribution processing means 112 divides the file M into two by secret sharing (may be divided into three or more). That is, the distributed processing means 112 secretly distributes the file M to generate the file M1 and the file M2. Then, the distributed processing means 112 transmits the generated files M1 and M2 to the encryption means 114. In this embodiment, the specific method of secret sharing performed by the distribution processing means 112 is not particularly limited.

The encryption key creating means 113 creates an encryption key (K) which is a common key based on the password (Pw). For example, the encryption key creating means 113 refers to the information storage unit 115 and acquires a password (Pw) from the information storage unit 115. Subsequently, the encryption key creating means 113 creates an encryption key (K) based on the acquired password (Pw) (the means for creating the encryption key may be any means). After that, the encryption key creating means 113 transmits the created encryption key (K) to the encryption means 114. The encryption key creating means 113 may use a password (Pw) input via an input device such as a keyboard included in the sending device 11.

The encryption means 114 (second encryption means) uses the encryption key (K) created by the encryption key creation means 113 and the public key (P_sv) acquired from the management server 12, and the files M1 and M2 are secretly distributed. Or, the encryption key (K) is encrypted.

For example, the encryption means 114 uses the encryption key (K) to encrypt the secretly distributed files M1 and M2. That is, the encryption means 114 encrypts the files M1 and M2 with the encryption key (K) to generate the encrypted files K (M1) and K (M2). Further, the encryption means 114 embeds a content ID (Cid), which is a unique ID, in the encrypted files K (M1) and K (M2). By embedding the content ID (Cid) in the encrypted files K (M1) and K (M2) in this way, the correspondence between the encrypted file K (M1) and the encrypted file K (M2) can be established. It becomes identifiable. The encrypted files K (M1) and K (M2) encrypted by the encryption means 114 are transmitted to the management server 12 and the receiving device 13 via the transmission / reception means 111.

Further, the encryption means 114 encrypts the encryption key (K) by using the public key (P_sv) received from the management server 12 via the transmission / reception means 111. That is, the encryption means 114 acquires the public key (P_sv) from the management server 12 via the transmission / reception means 111. Subsequently, the encryption means 114 encrypts the encryption key (K) with the acquired public key (P_sv) to generate the encrypted encryption key P_sv (K). The encryption key P_sv (K) encrypted by the encryption means 114 will be transmitted to the management server 12 via the transmission / reception means 111.

The information storage unit 115 is a storage device such as a memory or a disk device. The information storage unit 115 can store a password (Pw), an e-mail address (ML_b) of the receiving device 13, and the like.

The management server 12 is, for example, an information processing device such as a server device. The management server 12 flattenes the encrypted file K (M1) received from the sending device 11 and then encrypts it again with the encryption key (K') and stores it in the content information storage unit 126. Further, the management server 12 transmits a file corresponding to the request to the receiving device 13 in response to the request from the receiving device 13. As will be described later, when the management server 12 transmits a file to the receiving device 13, the corresponding file is used by using the encryption key (K ") created by using the state information (Im) received from the receiving device 13. Is encrypted, and the encrypted file is transmitted. At this time, the management server 12 encrypts the information stored in the content information storage unit 126 by using the encryption key (K "). Will be updated to.

FIG. 3 is an example of the configuration of the management server 12. Referring to FIG. 3, the management server 12 includes a transmission / reception means 121, a decryption means 122, an encryption key creation means 123, an encryption means 124, a content information management means 125, a content information storage unit 126, and a public key. -Has a private key storage unit 127.

The management server 12 has an arithmetic unit such as a CPU (Central Processing Unit) and a storage device (not shown). The management server 12 realizes each of the above means by, for example, the arithmetic unit executing a program included in the storage device.

The transmission / reception means 121 (first transmission / reception means) transmits / receives information to / from the sending side device 11 and the receiving side device 13. The information received from the sending device 11 via the transmitting / receiving means 121 includes, for example, an encrypted encryption key P_sv (K), an encrypted file K (M1), an email address (ML_b) of the receiving device 13. is there. Further, as the information to be transmitted to the sending side device 11 via the transmitting / receiving means 121, for example, there is a public key (P_sv). The information received from the receiving device 13 via the transmitting / receiving means 121 includes, for example, a password (Pw), an e-mail address (ML_b), a state information (Im), a content ID (Cid), and an encrypted file K. (M1') and the like. Further, as the information to be transmitted to the receiving device 13 via the transmission / reception means 121, for example, there is an encrypted file K ”(M1) and the like. The details of the encrypted file K "(M1') and the encrypted file K" (M1) will be described later.

The decryption means 122 decrypts the received encrypted encryption key P_sv (K), decrypts the encrypted file K (M1), and decrypts the encrypted file K'(M1).

For example, the decryption means 122 decrypts the encrypted encryption key P_sv (K) by using the private key (S_sv) stored in the public key / private key storage unit 127. That is, when the decryption means 122 receives the encrypted encryption key P_sv (K) from the sending side device 11 via the transmission / reception means 121, the decryption means 122 refers to the public key / private key storage unit 127 and refers to the public key / private key. Acquires the private key (S_sv) stored in the storage unit 127. Then, the decryption means 122 decrypts the encryption key P_sv (K) encrypted using the acquired private key (S_sv) to generate the encryption key (K).

Further, the decryption means 122 decrypts the encrypted encryption key P_sv (K) to generate the encryption key (K), and then uses the encryption key (K) to send the sender device 11 via the transmission / reception means 121. The encrypted file K (M1) received from is decrypted. That is, the decryption means 122 decrypts the encrypted file K (M1) with the encryption key (K) to generate the file M1. After that, the decryption means 122 transmits the generated file M1 to the encryption means 124.

Further, the decryption means 122 decrypts the encrypted file K'(M1) acquired from the content information storage unit 126 by using the encryption key (K') received from the encryption key creation means 123. That is, the decryption means 122 decrypts the encrypted file K'(M1) with the encryption key (K') to generate the file M1. After that, the decryption means 122 transmits the generated file M1 to the encryption means 124. The details of the encryption key creating means 123 and the encryption key (K') will be described later.

The encryption key creation means 123 (first encryption key creation means) creates an encryption key (K) based on the password (Pw). Further, the encryption key creating means 123 creates an encryption key (K') which is a common key and an encryption key (K ") which is a common key.

For example, when the transmitting / receiving means 121 receives the password (Pw), the encryption key creating means 123 creates the encryption key (K) based on the received password (Pw).

Further, the encryption key creating means 123 includes the created encryption key (K), the encryption key (K) generated by decryption by the decryption means 122, and the mail address (ML_b) of the receiving device 13 received by the transmission / reception means 121. Create an encryption key (K'), which is a common key, based on. Then, the encryption key creating means 123 transmits the created encryption key (K') to the encryption means 124.

Further, the encryption key creating means 123 is a common key based on the encryption key (K), the e-mail address (ML_b) of the receiving device 13 received by the transmitting / receiving means 121, and the state information (Im) received by the transmitting / receiving means 121. The encryption key (K ") is created. Then, the encryption key creation means 123 transmits the created encryption key (K") to the encryption means 124.

The encryption means 124 (first encryption means) encrypts the file M1 received from the decryption means 122 by using the encryption key (K') or the encryption key (K ") received from the encryption key creation means 123. Do.

For example, the encryption means 124 encrypts the file M1 using the encryption key (K'). That is, the encryption means 124 encrypts the file M1 with the encryption key (K') to generate the encrypted file K'(M1). After that, the encryption means 124 transmits the encrypted file K'(M1) to the content information management means 125.

Further, the encryption means 124 encrypts the file M1 using the encryption key (K "). That is, the encryption means 124 encrypts the file M1 with the encryption key (K") and encrypts the file M1. The file K "(M1) is generated. After that, the encryption means 124 transmits the encrypted file K" (M1) to the content information management means 125 and sends the encrypted file K "(M1) to the receiving device 13 via the transmitting / receiving means 121. Then, the encrypted file K ”(M1) is transmitted.

The content information management means 125 manages the creation, update, deletion, registration, and the like of the content information 1261 stored in the content information storage unit 126.

For example, when the content information management means 125 receives the encrypted file K (M1) from the sending device 11, the content information management means 125 extracts the content ID (Cid) embedded in the encrypted file K (M1) and extracts the content. New registration is performed in the content information 1261 in the information storage unit 126. That is, when the content information management means 125 receives the encrypted file K (M1) from the sender device 11, it creates a new record in the content information 1261 and embeds it in the encrypted file K (M1). Register the content ID (Cid).

Further, the content information management means 125 is based on the encrypted file K'(M1) received from the encryption means 124, and the mail address of the corresponding receiving device 13 is located at the location corresponding to the content ID (Cid). ML_b) and the encrypted file K'(M1) are registered.

Further, when the content information management means 125 receives the encrypted file K "(M1) from the encryption means 124, the content information management means 125 updates the information stored in the corresponding location to the encrypted file K" (M1). That is, the content information management means 125 refers to the content ID (Cid) and the e-mail address (ML_b) of the information received from the receiving device 13 to specify the location where the corresponding information is stored. Then, the content information management means 125 updates the information stored in the corresponding location from the encrypted file K'(M1) to the encrypted file K "(M1). In other words, the content information management means. When 125 receives the encrypted file K "(M1) from the encryption means 124, the 125 deletes the encrypted file K'(M1) stored in the corresponding location. Further, the content information management means 125 registers the newly encrypted file K "(M1) at the place where the encrypted file K'(M1) is deleted.

Further, when the content information management means 125 receives the encrypted file K "(M1') by the transmission / reception means 121, the content information management means 125 updates the information stored in the corresponding location to the encrypted file K" (M1'). .. That is, the content information management means 125 refers to the content ID (Cid) and the e-mail address (ML_b) of the information received from the receiving device 13 to specify the location where the corresponding information is stored. Then, the content information management means 125 updates the information stored in the corresponding location from the encrypted file K "(M1) to the encrypted file K" (M1'). In other words, when the content information management means 125 receives the encrypted file K "(M1'), the content information management means 125 deletes the encrypted file K" (M1) stored in the corresponding location. Further, the content information management means 125 registers the newly encrypted file K "(M1') at the place where the encrypted file K" (M1) is deleted.

In this way, the content information management means 125 manages the content information 1261 in the content information storage unit 126.

The content information storage unit 126 is a storage device such as a memory or a disk device. The content information storage unit 126 stores content information 1261 in which an encrypted file K'(M1), an encrypted file K "(M1), an encrypted file K" (M1'), and the like are stored. There is.

FIG. 4 is an example of the content information 1261. Referring to FIG. 4, the content information 1261 includes a content ID, an e-mail address, and a file. For example, the first line of FIG. 4 associates the content ID "A" with the e-mail address "a" and the file "α".

The public key / private key storage unit 127 is a storage device such as a memory or a disk device. The public key (P_sv) and the private key (S_sv) are stored in the public key / private key storage unit 127.

The receiving device 13 is, for example, an information processing device such as a personal computer or a tablet device. The receiving side device 13 decrypts the encrypted file received from the sending side device 11 and the management server 12 to acquire the file M which is the information that the sending side device 11 intends to transmit. The receiving side device 13 has state information (Im) and an e-mail address (ML_b) of the receiving side device 13.

The state information (Im) refers to information indicating the state of the receiving device 13. As the state information (Im), for example, device-specific information that specifies a device that enables decoding, environment-specific information that specifies the environment of a device that enables decoding, and the like can be considered. More specifically, the device specific information includes, for example, software specific information such as unique ID information automatically generated when a program for using the information sharing system 1 is installed on the receiving device 13. Device information such as the MAC name of the receiving device 13 and the machine name of the receiving device 13 can be considered. The environment-specific information includes, for example, connection location identification information for identifying an access point or gateway, and usage area identification information for specifying an area where the receiving device 13 is used, such as location information such as GPS information. Can be considered. As described above, various information such as device specific information and environment specific information can be adopted as the state information (Im).

The state information (Im) includes, for example, information obtained by hashing a value generated based on the fingerprint of the operator who operates the receiving device 13, information created based on the iris of the operator, and the like. It may include operator-specific information that identifies the operator of the device that enables decryption. In other words, the state information (Im) can include operator-specific information created based on the information used for biometric authentication. The state information (Im) may include only one of the device specific information, the environment specific information, and the operator specific information, or may include a plurality of information.

FIG. 5 is an example of the configuration of the receiving device 13. Referring to FIG. 5, the receiving device 13 includes a transmitting / receiving means 131, an encryption key creating means 132, a decryption means 133, a distributed processing means 134, an encryption means 135, and an information storage unit 136. ing. Further, the receiving device 13 can have a configuration for acquiring state information (Im) such as a GPS measuring means and a biometric authentication information acquiring means (not shown in FIG. 5).

The receiving device 13 has an arithmetic unit such as a CPU (Central Processing Unit) and a storage device (not shown). The receiving device 13 realizes each of the above means by, for example, the arithmetic unit executing a program included in the storage device.

The transmission / reception means 131 transmits / receives information to / from the sending device 11 and the management server 12. Information received from the sending device 11 via the transmitting / receiving means 131 includes, for example, an encrypted file K (M2) and a password (Pw). The information to be transmitted to the management server 12 via the transmission / reception means 131 includes, for example, a password (Pw), an e-mail address (ML_b) of the receiving device 13, a state information (Im), a content ID (Cid), and the like. , Encrypted file K "(M1') and the like. Further, as the information received from the management server 12 via the transmission / reception means 131, for example, there is an encrypted file K" (M1) and the like.

The encryption key creating means 132 creates an encryption key (K) based on the password (Pw). Further, the encryption key creating means 132 creates the encryption key (K "). The encryption key creating means 132 may be configured to create the encryption key (K').

For example, the encryption key creating means 132 creates an encryption key (K) based on the password (Pw) received by the transmitting / receiving means 131. Further, the encryption key creating means 132 creates an encryption key (K ") which is a common key based on the created encryption key (K), the e-mail address (ML_b) of the receiving device 13, and the status information (Im). Then, the encryption key creating means 132 transmits the created encryption key (K) or encryption key (K ") to the decryption means 133 or the encryption means 135.

When the user enters the password (Pw) to open the encrypted file K (M2) received from the sending device 11, the decrypting means 133 receives the entered password (Pw) via the transmitting / receiving means 131. The mail address (ML_b), status information (Im), and content ID (Cid) included in the encrypted file K (M2) of the side device 13 are transmitted to the management server 12. After that, when the encrypted file K "(M1) is received from the management server 12, it is received from the sending device 11 using the encryption key (K) or the encryption key (K") received from the encryption key creation means 132. The encrypted file K (M2) and the encrypted file K "(M1) received from the management server 12 are decrypted to generate the file M.

For example, the decryption means 133 decrypts the encrypted file K (M2) by using the encryption key (K). That is, the decryption means 133 decrypts the file K (M2) encrypted by the encryption key (K) to generate the file M2. Further, the decryption means 133 decrypts the encrypted file K "(M1) by using the encryption key (K"). That is, the decryption means 133 decrypts the file K "(M1) encrypted with the encryption key (K") to generate the file M1. After that, the decoding means 133 generates the file M from the file M1 and the file M2. The decoding means 133 performs decoding based on the information received from the sending device 11 and the management server 12 in this way, for example, and generates the file M.

The distribution processing means 134 (third distribution processing means) secretly distributes the file M generated by the decoding means 133. For example, the distributed processing means 134 divides the file M into two in a different way than the distributed processing means 112 (that is, so that a different file is generated than before). In other words, the distributed processing means 134 secretly distributes the file M to generate the files M1'and the file M2', which are different from the files M1 and M2. Then, the distributed processing means 134 transmits the generated file M1'and the file M2' to the encryption means 135.

The encryption means 135 (third encryption means) encrypts the newly secretly distributed files M1'and M2' using the encryption key (K) and the encryption key (K "), for example. The means 135 encrypts the file M2'using the encryption key (K). That is, the encryption means 135 encrypts the file M2'with the encryption key (K) and encrypts the file K (M2'). ) Is generated. Further, the encryption means 135 encrypts the file M1'using the encryption key (K "). That is, the encryption means 135 encrypts the file M1'with the encryption key (K") to generate the encrypted file K "(M1'). Then, the encryption means 135 has the same content as the content ID embedded in the corresponding file K (M2) for the encrypted file K (M2') and the encrypted file K "(M1'). The ID (Cid) is embedded. The encryption means 135 may be configured to embed the usage history information indicating the usage history in the encrypted file K (M2') or file K "(M1').

After that, the encryption means 135 transmits the encrypted file K "(M1'), the content ID (Cid), and the e-mail address (ML_b) of the receiving device 3 to the management server 12 via the transmitting / receiving means 131. As a result, the content information 1261 on the management server 12 side is updated. The encrypted file K (M2') is stored in, for example, a storage device (not shown) included in the receiving device 13. Will be done.

The information storage unit 136 is a storage device such as a memory or a disk device. The e-mail address (ML_b) of the receiving device 13 is stored in the information storage unit 136. The state information (Im) may be stored in the information storage unit 136.

The above is an example of the configuration of the information sharing system 1. Subsequently, an example of the flow of the information transmission method performed by the information sharing system 1 will be described with reference to FIGS. 6 to 15.

As shown in FIG. 6, the sending side device 11 has a file M, a password (Pw), and an e-mail address (ML_b) of the receiving side device 13. Further, the management server 12 has a public key (P_sv) and a private key (S_sv). In addition, the receiving device 13 has state information (Im) and its own e-mail address (ML_b).

In this state, the distribution processing means 112 of the sending side device 11 secretly distributes the file M and generates the file M1 and the file M2 as shown in FIGS. 7 and 13 (step S101). Then, the distributed processing means 112 transmits the secretly distributed files M1 and M2 to the encryption means 114.

Further, the encryption key creation means 113 of the sending side device 11 creates an encryption key (K) based on the password (Pw) (step S102). Then, the encryption key creating means 113 transmits the created encryption key (K) to the encryption means 114.

The encryption means 114 encrypts the files M1 and M2 using the encryption key (K) to generate the encrypted files K (M1) and K (M2). Further, the encryption means 114 embeds a uniquely determined content ID (Cid) in the encrypted files K (M1) and K (M2) (step S103).

Further, the encryption means 114 encrypts the encryption key (K) using the public key (P_sv) acquired from the management server 12 to generate the encrypted encryption key P_sv (K) (step S104).

After that, the sending side device 11 transmits the encrypted file K (M2) and the password (Pw) to the receiving side device 13 (step S105). Further, the sending side device 11 transmits the encrypted encryption key P_sv (K), the encrypted file K (M1), and the e-mail address (ML_b) of the receiving side device 13 to the management server 12 (step S106).

Subsequently, referring to FIGS. 8 and 13, the management server 12 sends the encrypted encryption key P_sv (K), the encrypted file K (M1), and the mail of the receiving device 13 sent by the sending device 11. Receives the address (ML_b). Then, the content information management means 125 of the management server 12 extracts the content ID (Cid) from the encrypted file K (M1), and sets the extracted content ID (Cid) in the newly created record of the content information 1261. ) Is registered (step S201).

Further, the decryption means 122 of the management server 12 decrypts the encrypted encryption key P_sv (K) by using the private key (S_sv) acquired from the public key / private key storage unit 127, and obtains the encryption key (K). Take out (step S202). Then, the decryption means 122 decrypts the encrypted file K (M1) using the extracted encryption key (K) to generate the file M1 (step S203). After that, the decryption means 122 transmits the generated file M1 to the encryption means 124.

The encryption key creating means 123 creates an encryption key (K') based on the encryption key (K) taken out by the decryption means 122 and the e-mail address (ML_b) of the receiving side device 13 that has been received (step S204). .. Then, the encryption key creating means 123 transmits the created encryption key (K') to the encryption means 124.

The encryption means 124 uses the encryption key (K') received from the encryption key creation means 123 to encrypt the file M1 received from the decryption means 122 to generate an encrypted file K'(M1) (step). S205). Then, the encryption means 124 transmits the encrypted file K'(M1) to the content information management means 125.

The content information management means 125 includes the encrypted file K'(M1) and the e-mail address (ML_b) of the receiving device 13 in the locations corresponding to the locations where the content ID (Cid) is newly registered in the content information 1261. And are registered (step S206). As a result, as shown in FIG. 8, in the content information 1261, the content ID (Cid), the e-mail address (ML_b), and the file K'(M1) are associated with each other.

As shown in FIGS. 9 and 14, in the receiving device 13 that has received the encrypted file K (M2) and password (Pw) from the sending device 11, the user of the receiving device 13 uses the encrypted file. Enter the password (Pw) to open K (M2). Then, the receiving device 13 has the entered password (Pw), its own mail address (ML_b) (for example, pre-registered in the program used when using the information sharing system 1), and the state information (Im). , The content ID (Cid), which is the ID embedded in the file to be opened (encrypted file K (M2)), is transmitted to the management server 12 (step S301).

When the above information is received from the receiving device 13, the encryption key creating means 123 of the management server 12 creates an encryption key (K) based on the received password (Pw), as shown in FIGS. 10 and 14. Step S207). Further, the encryption key creating means 123 creates an encryption key (K') based on the encryption key (K) and the received e-mail address (ML_b) (step S208). Then, the encryption key creation means 123 transmits the created encryption key (K') to the decryption means 122.

Further, the content information management means 125 of the management server 12 identifies and acquires the file stored in the content information 1261 based on the received e-mail address (ML_b) and the content ID (Cid). That is, the content information management means 125 acquires the encrypted file K'(M1) stored in association with the e-mail address (ML_b) and the content ID (Cid) (step S209). Then, the content information management means 125 transmits the acquired encrypted file K'(M1) to the decryption means 122.

The decryption means 122 decrypts the encrypted file K'(M1) using the encryption key (K') created by the encryption key creation means 123 to generate the file M1 (step S210). Then, the decryption means 122 transmits the generated file M1 to the encryption means 124.

Further, the encryption key creating means 123 creates an encryption key (K ") which is a common key based on the encryption key (K), the e-mail address (ML_b), and the state information (Im) (step S211). , The encryption key creating means 123 transmits the created encryption key (K ") to the encryption means 124.

The encryption means 124 uses the encryption key (K ") created by the encryption key creation means 123 to encrypt the file M1 received from the decryption means 122 to generate the encrypted file K" (M1) (step). S212).

After that, the management server 12 transmits the encrypted file K ”(M1) to the receiving device 13 via the transmission / reception means 121. Further, the content information management means 125 of the management server 12 transmits the content information 1261. That is, in the content information 1261, the content ID (Cid), the mail address (ML_b), and the encrypted file K "(M1) are associated with each other.

When the encrypted file K ”(M1) is received from the management server 12, as shown in FIGS. 11 and 14, the encryption key creation means 132 of the receiving device 13 receives the encryption key (K) based on the password (Pw). ) (Step S302), and the encryption key (K ") is created from the encryption key (K), the mail address (ML_b), and the status information (Im) (step S303). Further, the encryption key creating means 132 transmits the encryption key (K) and the encryption key (K ") to the decryption means 133.

The decryption means 133 decrypts the encrypted file K (M2) using the received encryption key (K) and generates the file M2 (step S304). Further, the decryption means 133 decrypts the encrypted file K "(M1) using the received encryption key (K") to generate the file M1 (step S305). After that, the decoding means 133 generates a file M from the file M1 and the file M2 (step S306). The decoding means 133 generates the file M in this way, for example, based on the information received from the sending device 11 and the management server 12.

After that, as shown in FIGS. 12 and 15, the distribution processing means 134 of the receiving device 13 secretly distributes the file M to generate the file M1'and the file M2' (step S307). Then, the distributed processing means 134 transmits the generated file M1'and the file M2' to the encryption means 135. Note that the contents of the file M may be updated after the file M is generated and before the secret sharing is performed.

The encryption means 135 uses the encryption key (K) or the encryption key (K ") to encrypt the newly secretly distributed files M1'and file M2'. For example, the encryption means 135 uses the encryption key (K). File M2'is encrypted using K) to generate an encrypted file K (M2'). The encryption means 135 encrypts file M1'using an encryption key (K "). , Encrypted file K "(M1') is generated. Then, the encryption means 135 corresponds to the encrypted file K (M2') and the encrypted file K" (M1'). Embed the same content ID (Cid) as the content ID embedded in K (M2). The encryption means 135 may be configured to embed the usage history information indicating the usage history in the encrypted file K (M2') or file K "(M1') (step S308).

After that, the encryption means 135 transmits the encrypted file K "(M1'), the content ID (Cid), and the e-mail address (ML_b) of the receiving device 3 to the management server 12 (step S309). Upon receiving the above information, the content information management means 125 of the management server 12 updates the content information 1261 based on the received information (step S214). As a result, the content information 1261 has a content ID (Cid) and an e-mail. The address (ML_b) and the encrypted file K "(M1') are associated with each other.

The above is an example of the flow of the information transmission method performed by the information sharing system 1 in the present embodiment.

As described above, the management server 12 of the information sharing system 1 in the present embodiment has the encryption key creation means 123 and the encryption means 124. With such a configuration, the management server 12 can create an encryption key (K ") based on the state information (Im) received from the receiving device 13, and the encryption means 124 can use the sending device 124. An encrypted file K "(M1) can be created based on the file M1 received from 11 and the created encryption key (K"). As a result, the encrypted file is stored in the management server 12. This means that "K" (M1) is stored. As a result, even if the password (Pw) is leaked to a third party, the third party who has acquired the password (Pw) cannot decrypt it. That is, after the receiving device 13 is used, even if the password (Pw) is leaked to a third party, the corresponding state information (Im) cannot be acquired, so that the encrypted file K ”(M1). ) Cannot be decrypted. In other words, it is possible to prevent anyone other than the target party from decrypting the encrypted file without distributing the key to the data sharing partner in advance.

If the receiving device 13 is used by a third party before it is used, the information stored in the management server 12 cannot be decoded from the receiving device 13. As a result, it becomes possible to notice the leakage of information such as a password (Pw) at an early stage.

Further, by adopting environment-specific information as state information (Im), even a legitimate user can specify the place of use of the encrypted file. Further, by adopting the operator-limited information as the state information (Im), it is possible to identify the operator of the receiving device 13 when decoding the file.

Further, the receiving device 13 in the present embodiment is configured to transmit the file K "(M1') secretly distributed and encrypted again to the management server 12 after decrypting the file. Due to this configuration, decryption cannot be performed based on the previously secret-shared file, and only the latest file can be used at all times. Also, by embedding the usage history in the file, the usage history can be embedded. It is possible to manage the usage history of the file in the file.

In the present embodiment, the sending side device 11 transmits the secretly distributed file to the management server 12 and the receiving side device 13. However, the sending side device 11 may be configured to transmit the file to be transmitted to the receiving side device 13 to the management server 12 without performing secret sharing. In this case, as shown in FIG. 16, the encrypted file K (M) is transmitted to the management server 12, while the content ID (Cid) corresponding to the password (Pw) is sent to the receiving device 13. ) And the prescribed notification will be sent. Further, as shown in FIG. 17, the password (Pw), the e-mail address (ML_b), the status information (Im), and the content ID (Cid) are transmitted from the receiving device 13 to the management server 12 in response to the notification. Will be done. Then, the encryption key creation means 123 of the management server 12 creates an encryption key (K) based on the received password (Pw), and also uses the encryption key (K), the mail address (ML_b), and the status information (Im). Based on this, an encryption key (K ") is created. Then, after decryption by the decryption means 122, the encryption means 124 uses the encryption key (K") to encrypt the encrypted file K "(M). As a result, the encrypted file K "(M) is stored in the management server 12. Even with such a configuration that does not share secrets, the same effects as those described in the present embodiment can be obtained. The sending side device 11 may be configured to have a function as the management server 12 (the sending side device 11 and the management server 12 may be integrally configured).

Further, in the present embodiment, the encryption key creation means 123 and the encryption key creation means 132 create an encryption key (K ") based on the encryption key (K), the e-mail address (ML_b), and the state information (Im). However, if the encryption key creating means 123 and the encryption key creating means 132 use the state information (Im), the encryption key (K ") may be created by a method other than the above method. For example, the encryption key creation means 123 and the encryption key creation means 132 may be configured to create an encryption key (K ") based on the encryption key (K'), the e-mail address (ML_b), and the state information (Im). You can.

In order to securely pass the key for decrypting the ciphertext to the data sharing partner, it has been conventionally practiced to register the data sharing partner with an authentication server capable of distributing or issuing the key. According to this embodiment, it is not necessary to register a data sharing partner in an authentication server capable of key distribution or key issuance for the purpose of key distribution. Further, according to the present embodiment, there is an effect that it is not necessary to install an authentication server capable of key distribution or key issuance for the purpose of safely passing the key for decrypting the ciphertext to the data sharing partner. Be done.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIGS. 18 to 20. In the second embodiment, the outline of the configuration of the information sharing system 2, the management server 3, and the receiving device 4 for transmitting information from the sending device 21 to the receiving device 23 via the management server 22 will be described.

Referring to FIG. 18, the information sharing system 2 in the present embodiment has a sending side device 21, a management server 22, and a receiving side device 23. As shown in FIG. 18, the sending device 21 and the management server 22 are connected so as to be able to communicate with each other. Further, the management server 22 and the receiving device 23 are connected so as to be able to communicate with each other.

The management server 22 has a first transmission / reception means 221, a first encryption key creation means 222, and a first encryption means 223. The management server 22 has, for example, an arithmetic unit and a storage device (not shown), and the arithmetic unit executes a program included in the storage device to realize each of the above means.

The first transmission / reception means 221 receives the first ciphertext encrypted by the first encryption key from the sending side device 21, and the state information indicating the state of the receiving side device 23 from the receiving side device 23. To receive.

The first encryption key creation means 222 creates a second encryption key based on the state information received by the first transmission / reception means 221. Then, the first encryption key creation means 222 transmits the created second encryption key to the first encryption means 223.

The first encryption means 223 creates a second ciphertext based on the second ciphertext created by the first encryption key creation means 222 and the first ciphertext. The second ciphertext created by the first encryption means 223 is transmitted to the receiving device 23 via the first transmission / reception means 221.

As described above, the information sharing system 2 in the present embodiment has the sending side device 21, the management server 22, and the receiving side device 23. Further, the management server 22 has a first transmission / reception means 221, a first encryption key creation means 222, and a first encryption means 223. With such a configuration, the first encryption key creation means 222 of the management server 22 can create the second encryption key based on the state information received from the receiving device 23. Further, the first encryption means 223 can create a second ciphertext based on the first ciphertext received from the sending device 21 and the created second encryption key. As a result, the management server 22 stores the second ciphertext. As a result, it is possible to prevent anyone other than the target party from decrypting the encrypted file without distributing the key to the data sharing partner in advance.

Further, the information transmission method executed by operating the information sharing system 2 described above is an information transmission method in which information is transmitted from the sending side device to the receiving side device via the management server, and the management server is , The first ciphertext encrypted by the first encryption key is received from the sending device, the receiving device receives the status information indicating the status of the receiving device, and the received status information is used. It is a method of transmitting the second ciphertext created based on the second encryption key created based on the above and the first ciphertext to the receiving device.

Even the invention of the information transmission method having the above-described configuration can achieve the above-mentioned object of the present invention because it has the same operation as the above-mentioned information sharing system 2.

Further, FIG. 19 shows an example of the configuration of the management server 3 capable of achieving the same purpose as the information sharing system 2. Referring to FIG. 19, the management server 3 has a first transmission / reception means 31, a first encryption key creation means 32, and a first encryption means 33. The management server 3 has, for example, an arithmetic unit and a storage device (not shown), and the arithmetic unit executes a program included in the storage device to realize each of the above means. The first transmission / reception means 31 corresponds to the first transmission / reception means 221 described above, the first encryption key creation means 32 corresponds to the first encryption key creation means 222, and the first encryption means 33 corresponds to the first encryption means. Corresponds to 223. Therefore, the description of each means will be omitted.

Further, the management server 3 can be realized by incorporating a predetermined program into the management server 3. Specifically, the program according to another embodiment of the present invention receives the first ciphertext encrypted by the first encryption key from the external device to the management server, and state information indicating the state of the receiving device. Is received, and the second encryption key created based on the received state information and the second ciphertext created based on the first ciphertext are transmitted to the receiving device. It is a program to realize the processing.

Further, the information processing method executed by operating the management server 3 described above is an information processing method performed by the management server, and the first ciphertext encrypted by the first encryption key is transmitted to an external device. The second encryption key created based on the received status information and the second encryption key created based on the received status information and the first ciphertext created based on the received status information indicating the status of the receiving device. This is a method of transmitting the ciphertext to the receiving device.

Even the invention of the program or the information processing method having the above-mentioned configuration can achieve the above-mentioned object of the present invention because it has the same operation as the above-mentioned management server 3.

Further, FIG. 20 shows an example of the configuration of the receiving side device 4 capable of achieving the same purpose as the information sharing system 2. Referring to FIG. 20, the receiving device 4 includes a transmitting / receiving means 41 and a decoding means 42. The receiving device 4 has, for example, an arithmetic unit and a storage device (not shown), and the arithmetic unit executes a program included in the storage device to realize each of the above means.

The transmission / reception means 41 transmits state information, which is information indicating the state of the receiving device 4, to the management server having the ciphertext to be decrypted. Further, the transmission / reception means 41 receives from the management server a ciphertext encrypted based on the encryption key created based on the transmitted state information.

The decryption means 42 decrypts the ciphertext received by the transmission / reception means 41. Since the receiving device 4 has the state information, it is possible to create an encryption key based on the state information, and the created encryption key is used to decrypt the ciphertext received by the transmitting / receiving means 41. Will be done.

As described above, the receiving device 4 in the present embodiment has the transmitting / receiving means 41 and the decoding means 42. With such a configuration, the receiving device 4 transmits the status information to the management server having the ciphertext to be decrypted, and is based on the encryption key created from the management server based on the transmitted status information. You will receive the encrypted ciphertext. In addition, it will be decrypted by the decoding means. As a result, the management server stores the ciphertext encrypted based on the encryption key created based on the state information. As a result, it is possible to prevent anyone other than the target party from decrypting the encrypted file without distributing the key to the data sharing partner in advance.

Further, the receiving side device 4 can be realized by incorporating a predetermined program into the receiving side device 4. Specifically, the program according to another embodiment of the present invention transmits state information, which is information indicating the state of the receiving device, to the receiving device to the management server having the ciphertext to be decrypted. It is a program for realizing a process of acquiring a ciphertext encrypted based on an encryption key created based on the transmitted state information from the management server and decrypting the acquired ciphertext.

Further, the decryption method executed by operating the receiving side device 4 described above is a decryption method performed by the receiving side device, and the receiving side of the management server having the ciphertext to be decrypted. Status information, which is information indicating the status of the device, is transmitted, and the ciphertext encrypted based on the encryption key created based on the transmitted status information is acquired from the management server, and the acquired ciphertext is decrypted. It is a method of doing.

Even the invention of the program or the decoding method having the above-described configuration can achieve the above-mentioned object of the present invention because it has the same operation as the above-mentioned receiving device 4.

<Additional notes>
Part or all of the above embodiments may also be described as in the appendix below. Hereinafter, the outline of the information transmission method and the like in the present invention will be described. However, the present invention is not limited to the following configurations.

(Appendix 1)
This is an information transmission method in which information is transmitted from the sending device to the receiving device via the management server.
The management server
The first ciphertext encrypted by the first encryption key is received from the sending device,
Receives state information from the receiving device, which is information indicating the state of the receiving device,
An information transmission method for transmitting a second ciphertext created based on a second encryption key created based on the received state information and the first ciphertext to the receiving device.

(Appendix 2)
The information transmission method described in Appendix 1.
An information transmission method in which the management server receives device-specific information as state information, which is information for specifying a device that decrypts the second ciphertext.

(Appendix 3)
The information transmission method described in Appendix 1 or 2.
An information transmission method in which the management server receives environment-specific information, which is information for specifying the environment of a device that decrypts the second ciphertext, as the state information.

(Appendix 4)
The information transmission method according to any one of Supplementary notes 1 to 3.
An information transmission method in which the management server receives operator-specific information, which is information for identifying an operator of the receiving device, as the state information.

(Appendix 5)
The information transmission method according to any one of Appendix 1 to 4.
The sending side device divides the information to be transmitted to the receiving side device into two by secret sharing, encrypts one of them with the first encryption key, and then sends the information as the first ciphertext to the management server. Then, after encrypting the other with the first encryption key, it is transmitted to the receiving device as a third ciphertext.
The receiving side device decrypts based on the second ciphertext received from the management server and the third ciphertext received from the sending side device, and the information transmitted by the sending side device. How to send information to get.

(Appendix 6)
The information transmission method described in Appendix 5.
An information transmission method in which the receiving device transmits the state information to the management server and receives the second ciphertext from the management server when decrypting the third ciphertext.

(Appendix 7)
The information transmission method according to Appendix 5 or 6.
After acquiring the information transmitted by the sending device, the receiving device secretly distributes the acquired information and divides the acquired information into two, and one of the divided devices is based on the second encryption key. A method of transmitting information that is encrypted and then transmitted to the management server.

(Appendix 8)
The information transmission method according to any one of Appendix 1 to 7.
The management server
A third encryption key and the first encryption key created based on the first encryption key by receiving the first ciphertext from the sender device and the first encryption key from the sender device. A ciphertext based on the first ciphertext is created and stored based on the ciphertext of the above.
When the state information is received from the receiving device, the second ciphertext created based on the second encryption key and the ciphertext based on the first ciphertext is sent to the receiving device. Information transmission method to be transmitted.

(Appendix 1A)
An information sharing system that sends information from the sending device to the receiving device via the management server.
The management server
With the first transmitting / receiving means for receiving the first ciphertext encrypted by the first encryption key from the sending side device and receiving the state information which is the information indicating the state of the receiving side device from the receiving side device. ,
A first encryption key creation means that creates a second encryption key based on the received status information, and
A first encryption means for creating a second ciphertext based on the second encryption key and the first ciphertext.
An information sharing system having the above and configured to transmit the created second ciphertext to the receiving device via the first transmitting / receiving means.

(Appendix 2A)
The information sharing system described in Appendix 1A.
The first transmission / reception means is an information sharing system that receives device-specific information as state information, which is information for specifying a device that decrypts the second ciphertext.

(Appendix 3A)
The information sharing system described in Appendix 1A or 2A.
The first transmission / reception means is an information sharing system that receives environment-specific information, which is information that specifies the environment of a device that decrypts the second ciphertext, as the state information.

(Appendix 4A)
The information sharing system according to any one of Appendix 1A to 3A.
The first transmission / reception means is an information sharing system that receives operator-specific information, which is information that identifies an operator of the receiving device, as the state information.

(Appendix 5A)
The information sharing system according to any one of Appendix 1A to 4A.
The sending side device has a second distributed processing means that divides information transmitted to the receiving side device into two by secret sharing, and one of the divided parts by the second distributed processing means is a first encryption key. It has a second encryption means that encrypts the other with the first encryption key, and one of the ones encrypted by the second encryption means is managed as the first ciphertext. It is configured to send to the server and the other as a third ciphertext to the receiving device.
The receiving side device performs decryption based on the second ciphertext received from the management server and the third ciphertext received from the sending side device, and the information transmitted by the sending side device. An information sharing system having a decryption means for acquiring.

(Appendix 6A)
The information sharing system described in Appendix 5A.
The decryption means is an information sharing system that transmits the state information to the management server and receives the second ciphertext from the management server when decrypting the third ciphertext.

(Appendix 7A)
The information sharing system described in Appendix 5A or 6A.
The receiving side device is a third distributed processing means that secretly distributes the acquired information and divides the acquired information into two after acquiring the information transmitted by the sending side device by the decoding means, and one of the divided parts. It has a third encryption means that encrypts the information based on the second encryption key, and is configured to transmit the ciphertext encrypted based on the second encryption key to the management server. Information sharing system.

(Appendix 8A)
The information sharing system according to any one of Appendix 1A to 7A.
The first transmission / reception means receives the first encryption text from the sender device and receives the first encryption key from the sender device, and the first encryption key creation means is the first encryption key creation means. A third encryption key is created based on the encryption key, and the first encryption means is based on the third encryption key and the first encryption text, and the encryption text based on the first encryption text. The management server is configured to store a cipher statement based on the first ciphertext created by the first encryption means.
When the first transmitting / receiving means receives the state information from the receiving device, the first encryption means is based on the second encryption key and the ciphertext based on the first ciphertext. An information sharing system configured to create a second ciphertext and transmit the created second ciphertext to the receiving device.

(Appendix 9)
Information processing method performed by the management server
The first ciphertext encrypted by the first encryption key is received from the external device,
Receives status information indicating the status of the receiving device,
An information processing method in which a second ciphertext created based on the received state information and a second ciphertext created based on the first ciphertext are transmitted to the receiving device.

(Appendix 10)
The information processing method described in Appendix 9
An information processing method for receiving device-specific information, which is information for specifying a device that decrypts the second ciphertext, as the state information.

(Appendix 11)
The information processing method according to Appendix 9 or 10.
An information processing method for receiving environment-specific information, which is information for specifying the environment of a device that decrypts the second ciphertext, as the state information.

(Appendix 12)
The information processing method according to any one of Supplementary note 9 to 11.
Based on the third ciphertext and the first ciphertext created based on the first ciphertext and the first ciphertext received from the external device as well as the first ciphertext. , The first ciphertext is encrypted and stored,
When the state information is received from the receiving device, a second ciphertext created based on the second encryption key and the encrypted first ciphertext is sent to the receiving device. Information processing method to send.

(Appendix 9A)
A first transmission / reception means for receiving the first ciphertext encrypted by the first encryption key from the external device and receiving the state information which is the information indicating the state of the receiving side device from the receiving side device.
A first encryption key creation means that creates a second encryption key based on the received status information, and
A first encryption means for creating a second ciphertext based on the second encryption key and the first ciphertext.
A management server having the above and configured to transmit the created second ciphertext to the receiving device via the first transmitting / receiving means.

(Appendix 10A)
The management server described in Appendix 9A.
The first transmission / reception means is a management server that receives device identification information, which is information for specifying a device that decrypts the second ciphertext, as the state information.

(Appendix 11A)
The management server described in Appendix 9A or 10A.
The first transmission / reception means is a management server that receives environment-specific information, which is information that specifies the environment of the device that decrypts the second ciphertext, as the state information.

(Appendix 12A)
The management server according to any one of Appendix 9A to 11A.
The first transmission / reception means receives the first encryption text from the external device and the first encryption key from the external device, and the first encryption key creation means receives the first encryption key. A third encryption key is created based on the above, and the first encryption means creates an encryption sentence based on the first encryption sentence based on the third encryption key and the first encryption sentence. It is configured to store a cipher statement based on the first ciphertext created by the first encryption means.
When the first transmitting / receiving means receives the state information from the receiving device, the first encryption means is based on the second encryption key and the ciphertext based on the first ciphertext. A management server configured to create a second ciphertext and transmit the created second ciphertext to the receiving device.

(Appendix 13)
On the management server
The first ciphertext encrypted by the first encryption key is received from the external device,
Receives status information indicating the status of the receiving device,
In order to realize a process of transmitting a second ciphertext created based on the received second encryption key created based on the state information and the first ciphertext to the receiving device. Program.

(Appendix 14)
The program described in Appendix 14,
A program that receives device-specific information, which is information that identifies a device that decrypts the second ciphertext, as the state information.

(Appendix 15)
The program according to Appendix 13 or 14.
As the state information, a program that receives environment-specific information that is information that specifies the environment of the device that decrypts the second ciphertext.

(Appendix 16)
The program according to any one of Appendix 13 to 15.
Based on the third ciphertext and the first ciphertext created based on the first ciphertext and the first ciphertext received from the external device as well as the first ciphertext. , The first ciphertext is encrypted and stored,
When the state information is received from the receiving device, a second ciphertext created based on the second encryption key and the encrypted first ciphertext is sent to the receiving device. The program to send.

(Appendix 17)
A decryption method performed by the receiving device.
Status information, which is information indicating the status of the receiving device, is transmitted to the management server having the ciphertext to be decrypted.
A decryption method for acquiring a ciphertext encrypted based on an encryption key created based on the transmitted state information from the management server and decrypting the acquired ciphertext.

(Appendix 18)
The decoding method according to Appendix 17,
A decoding method for transmitting device identification information, which is information for identifying the receiving device, as the state information.

(Appendix 19)
The decoding method according to Appendix 17 or 18.
A decoding method for transmitting environment-specific information, which is information for specifying the environment of the receiving device, as the state information.

(Appendix 20)
The decoding method according to any one of Supplementary note 17 to 19.
When a ciphertext is received from an external device and the received ciphertext is decrypted, the state information is transmitted to the management server, and the management server uses the encryption key created based on the state information. Get the ciphertext encrypted based on
A decryption method that decrypts based on the ciphertext received from the management server and the ciphertext received from the external device.

(Appendix 21)
The decoding method according to Appendix 20,
After decryption, the information acquired by the decryption is secretly distributed and divided into two, and one of the divided pieces is encrypted based on the encryption key created based on the state information, and then the above-mentioned Decryption method to send to the management server.

(Appendix 17A)
A state information that is information indicating the state of the receiving device is transmitted to a management server having a ciphertext to be decrypted, and an encryption key created from the management server based on the transmitted state information. A means of receiving and receiving ciphertext encrypted based on
A decryption means for decrypting the ciphertext received by the transmission / reception means, and
Recipient device with.

(Appendix 18A)
The receiving device according to Appendix 17A.
The transmitting / receiving means is a receiving side device that transmits device specific information which is information for identifying the receiving side device as the state information.

(Appendix 19A)
The receiving device according to Appendix 17A or 18A.
The transmitting / receiving means is a receiving side device that transmits environment-specific information, which is information for specifying the environment of the receiving-side device, as the state information.

(Appendix 20A)
The receiving device according to any one of Appendix 17A to 19A.
The transmitting / receiving means receives a ciphertext from an external device, transmits the state information to the management server when decrypting the received ciphertext, and creates the ciphertext from the management server based on the state information. Receives ciphertext encrypted based on the encrypted key
The decryption means is a receiving device that decrypts based on the ciphertext received from the management server and the ciphertext received from the external device.

(Appendix 21A)
The receiving device according to Appendix 20A.
After decoding by the decoding means, the information acquired by the decoding is secretly distributed and divided into two, and one of the third distributed processing means and the divided by the third distributed processing means is used as the state information. A receiving device having a third encryption means that encrypts based on an encryption key created based on the above, and configured to transmit information encrypted by the third encryption means to a management server.

(Appendix 22)
On the receiving device,
Status information, which is information indicating the status of the receiving device, is transmitted to the management server having the ciphertext to be decrypted.
A program for acquiring a ciphertext encrypted based on an encryption key created based on the transmitted state information from the management server and realizing a process of decrypting the acquired ciphertext.

(Appendix 23)
The program described in Appendix 22
A program that transmits device identification information, which is information for identifying the receiving device, as the state information.

(Appendix 24)
The program described in Appendix 22 or 23.
A program that transmits environment-specific information, which is information that identifies the environment of the receiving device, as the state information.

(Appendix 25)
The program according to any one of Supplementary note 22 to 24.
When a ciphertext is received from an external device and the received ciphertext is decrypted, the state information is transmitted to the management server, and the management server uses the encryption key created based on the state information. Get the ciphertext encrypted based on
A program that decrypts based on the ciphertext received from the management server and the ciphertext received from the external device.

(Appendix 26)
The program described in Appendix 25.
After decryption, the information acquired by the decryption is secretly distributed and divided into two, and one of the divided pieces is encrypted based on the encryption key created based on the state information, and then the above-mentioned A program to send to the management server.

The programs described in each of the above-described embodiments and appendices may be stored in a storage device or recorded in a computer-readable recording medium. For example, the recording medium is a portable medium such as a flexible disk, an optical disk, a magneto-optical disk, and a semiconductor memory.

Although the present invention has been described above with reference to each of the above embodiments, the present invention is not limited to the above-described embodiments. Various changes that can be understood by those skilled in the art can be made to the structure and details of the present invention within the scope of the present invention.

1 Information sharing system 11 Sender device 111 Transmission / reception means 112 Distributed processing means 113 Encryption key creation means 114 Encryption means 115 Information storage unit 12 Management server 121 Transmission / reception means 122 Decryption means 123 Encryption key creation means 124 Encryption means 125 Content information management Means 126 Content information storage unit 1261 Content information 127 Public key / private key storage unit 13 Receiving side device 131 Transmission / reception means 132 Encryption key creation means 133 Decryption means 134 Distributed processing means 135 Encryption means 136 Information storage unit 2 Information sharing system 21 Sending Side device 22 Management server 221 First transmission / reception means 222 First encryption key creation means 223 First encryption means 23 Receiving side device 3 Management server 31 First transmission / reception means 32 First encryption key creation means 33 First encryption means 4 Receiving Side device 41 Transmission / reception means 42 Decryption means

Claims (12)

This is an information transmission method in which information is transmitted from the sending device to the receiving device via the management server.
The management server
The first ciphertext encrypted by the first encryption key is received from the sending device,
Receives state information from the receiving device, which is information indicating the state of the receiving device,
A second ciphertext created based on the received state information and a second ciphertext created based on the first ciphertext are transmitted to the receiving device .
The sending side device divides the information to be transmitted to the receiving side device into two by secret sharing, encrypts one of them with the first encryption key, and then sends the information as the first ciphertext to the management server. Then, after encrypting the other with the first encryption key, it is transmitted to the receiving device as a third ciphertext.
The receiving side device decrypts based on the second ciphertext received from the management server and the third ciphertext received from the sending side device, and the information transmitted by the sending side device. To get and
After acquiring the information transmitted by the sending device, the receiving device secretly distributes the acquired information and divides the acquired information into two, and one of the divided devices is based on the second encryption key. An information transmission method of transmitting to the management server after encryption . The information transmission method according to claim 1.
An information transmission method in which the management server receives device-specific information as state information, which is information for specifying a device that decrypts the second ciphertext. The information transmission method according to claim 1 or 2.
An information transmission method in which the management server receives environment-specific information, which is information for specifying the environment of a device that decrypts the second ciphertext, as the state information. The information transmission method according to any one of claims 1 to 3.
An information transmission method in which the management server receives operator-specific information, which is information for identifying an operator of the receiving device, as the state information. The information transmission method according to any one of claims 1 to 4 .
An information transmission method in which the receiving device transmits the state information to the management server and receives the second ciphertext from the management server when decrypting the third ciphertext. The information transmission method according to any one of claims 1 to 5 .
The management server
A third encryption key and the first encryption key created based on the first encryption key by receiving the first ciphertext from the sender device and the first encryption key from the sender device. A ciphertext based on the first ciphertext is created and stored based on the ciphertext of the above.
When the state information is received from the receiving device, the second ciphertext created based on the second encryption key and the ciphertext based on the first ciphertext is sent to the receiving device. Information transmission method to be transmitted. A decryption method performed by the receiving device.
Status information, which is information indicating the status of the receiving device, is transmitted to the management server having the ciphertext to be decrypted.
The ciphertext encrypted based on the encryption key created based on the transmitted state information is acquired from the management server, and the acquired ciphertext is decrypted .
When a ciphertext is received from an external device and the received ciphertext is decrypted, the state information is transmitted to the management server, and the management server uses the encryption key created based on the state information. Get the ciphertext encrypted based on
Decryption is performed based on the ciphertext received from the management server and the ciphertext received from the external device.
After decryption, the information acquired by the decryption is secretly distributed and divided into two, and one of the divided pieces is encrypted based on the encryption key created based on the state information, and then the above-mentioned Decryption method to send to the management server . The decoding method according to claim 7 .
A decoding method for transmitting device identification information, which is information for identifying the receiving device, as the state information. The decoding method according to claim 7 or 8 .
A decoding method for transmitting environment-specific information, which is information for specifying the environment of the receiving device, as the state information. On the receiving device,
Status information, which is information indicating the status of the receiving device, is transmitted to the management server having the ciphertext to be decrypted.
The ciphertext encrypted based on the encryption key created based on the transmitted state information is acquired from the management server, and the acquired ciphertext is decrypted .
When a ciphertext is received from an external device and the received ciphertext is decrypted, the state information is transmitted to the management server, and the management server uses the encryption key created based on the state information. Get the ciphertext encrypted based on
Decryption is performed based on the ciphertext received from the management server and the ciphertext received from the external device.
After decryption, the information acquired by the decryption is secretly distributed and divided into two, and one of the divided pieces is encrypted based on the encryption key created based on the state information, and then the above-mentioned A program to realize the process of sending to the management server . The program according to claim 10 .
A program that transmits device identification information, which is information for identifying the receiving device, as the state information. The program according to claim 10 or 11 .
A program that transmits environment-specific information, which is information that identifies the environment of the receiving device, as the state information.

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