Data distribution system, data distribution method, and data distribution program

Abstract

To reduce the workload in a data transmitting device.SOLUTION: A data distribution system distributes encrypted data from a transmitting device to a receiving device via a relay device with support of a key issuing device. The transmitting device is configured to encrypt data using a public key, create a user-defined policy for each data ID, attach the defined policy for the corresponding data ID to the encrypted data, and transmit the encrypted data with the user-defined policy attached to the relay device. The key issuing device is configured to generate a re-encryption key using a private key, and the user-defined policy for the corresponding data ID, generate a decryption key for the receiving device that satisfies the user-defined policy to decrypt the re-encrypted data, transmit the re-encryption key to the relay device, and transmit the decryption key to the receiving device that satisfies the user-defined policy.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a data distribution system, a data distribution method, and a data distribution program. [Background technology]

[0002] Proxy re-encryption (PRE) is a public key encryption method that allows a third party to convert a ciphertext that can be decrypted by user A into another ciphertext that can be decrypted by user B. A data distribution system that uses attribute-based PRE to perform disclosure control is known. For example, Patent Document 1 discloses a data distribution system that uses attribute-based PRE. In a distribution system that uses attribute-based PRE, a re-encryption key is used to convert data into ciphertext that can be decrypted using a specific attribute that specifies an access policy. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2011 / 045723 Summary of the Invention [Problem to be solved by the invention]

[0004] The disclosures of the above prior art documents are incorporated herein by reference. The following analysis is provided by the inventor.

[0005] In a conventional distribution system using attribute-based PRE, the data owner generates and manages the re-encryption key (see, for example, Patent Document 1). However, in a conventional distribution system using attribute-based PRE, the attribute-based PRE and its revocation process require high computational costs, which makes it unsuitable for users with large databases, frequent data sharing, IoT devices, etc.

[0006] In view of the above-mentioned problems, an object of the present invention is to provide a data distribution system, a data distribution method, and a data distribution program that contribute to reducing the workload on a data transmission device. [Means for solving the problem]

[0007] According to a first aspect of the present invention, there is provided a data distribution system for distributing encrypted data from a transmitting device to a receiving device via a relay device with support of a key issuing device, the key issuing device being configured to output a pair of a public key and a private key, transmit the public key to the transmitting device, and hold the private key, the transmitting device being configured to encrypt data using the public key, create a user-defined policy for each data ID, attach the defined policy for the corresponding data ID to the encrypted data, and transmit the encrypted data with the user-defined policy attached to the relay device, the relay device separating the user-defined policy from the encrypted data, and storing the user-defined policy in a predefined format. a key issuing device configured to generate a re-encryption key using the private key and the user-defined policy for a corresponding data ID, generate a decryption key for the receiving device that satisfies the user-defined policy to decrypt the re-encrypted data, transmit the re-encryption key to the relay device, and transmit the decryption key to the receiving device that satisfies the user-defined policy, the relay device configured to re-encrypt the encrypted data of the data ID using the re-encryption key and transmit the re-encrypted data to the receiving device, and the receiving device configured to decrypt the re-encrypted data using the decryption key.

[0008] According to a second aspect of the present invention, there is provided a data distribution method for distributing encrypted data from a transmitting device to a receiving device via a relay device with support of a key issuing device, the method comprising the steps of: outputting a pair of a public key and a private key by the key issuing device; transmitting the public key to the transmitting device; storing the private key; encrypting data using the public key by the transmitting device; creating a user-defined policy for each data ID; attaching the user-defined policy for the corresponding data ID to the encrypted data; transmitting the encrypted data with the user-defined policy attached to the relay device; separating the user-defined policy from the encrypted data by the relay device; a data distribution method including: providing a policy to the key issuing device; generating a re-encryption key by the key issuing device using the private key and the user-defined policy for the corresponding data ID; generating a decryption key for the receiving device that satisfies the user-defined policy to decrypt the re-encrypted data; transmitting the re-encryption key to the relay device; transmitting the decryption key to the receiving device that satisfies the user-defined policy; re-encrypting the encrypted data of the data ID using the re-encryption key by the relay device; transmitting the re-encrypted data to the receiving device; and decrypting the re-encrypted data by the receiving device using the decryption key.

[0009] According to a third aspect of the present invention, there is provided a data distribution program for distributing encrypted data from a transmitting device to a receiving device via a relay device with support of a key issuing device, the program causing the key issuing device to output a pair of a public key and a private key, transmit the public key to the transmitting device, hold the private key, encrypt data using the public key, create a user-defined policy for each data ID, attach the user-defined policy for the corresponding data ID to the encrypted data, transmit the encrypted data with the user-defined policy attached to the relay device, cause the relay device to separate the user-defined policy from the encrypted data, and a data distribution program including: causing the key issuing device to provide a policy to the key issuing device; causing the key issuing device to generate a re-encryption key using the private key and the user-defined policy for the corresponding data ID; causing the key issuing device to generate a decryption key for the receiving device that satisfies the user-defined policy to decrypt the re-encrypted data; causing the key issuing device to transmit the re-encryption key to the relay device; causing the relay device to transmit the decryption key to the receiving device that satisfies the user-defined policy; causing the relay device to re-encrypt the encrypted data of the data ID using the re-encryption key; causing the re-encrypted data to be transmitted to the receiving device; and causing the receiving device to decrypt the re-encrypted data using the decryption key.

[0010] According to each aspect of the present invention, it is possible to provide a data distribution system, a data distribution method, and a data distribution program that contribute to reducing the workload on a data transmission device. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram illustrating a data distribution system. [Figure 2] FIG. 1 illustrates the first step of the data distribution process. [Figure 3] FIG. 10 illustrates a second step in the data distribution process. [Figure 4] FIG. 10 illustrates a third step in the data distribution process. [Figure 5] FIG. 10 illustrates a fourth step in the data distribution process. [Figure 6] FIG. 5 illustrates the fifth and sixth steps of the data distribution process. [Figure 7] FIG. 7 illustrates the seventh and eighth steps of the data distribution process. [Figure 8] FIG. 1 is a system diagram of a data distribution method in the encryption and re-encryption phases. [Figure 9] FIG. 1 is a system diagram of a data distribution method in a decoding phase. [Figure 10] FIG. 1 illustrates multiple sub-policies in a data distribution system. [Figure 11] FIG. 7 illustrates a seventh step in the data distribution process. [Figure 12] FIG. 1 is a system diagram of a data distribution method in a re-encryption phase. [Figure 13] FIG. 10 is a system diagram of a data distribution method in the decryption key issuing phase. [Figure 14] FIG. 2 is a diagram illustrating an example of the hardware configuration of a transmitting device, a receiving device, a relay device, and a key issuing device. DETAILED DESCRIPTION OF THE INVENTION

[0012] [First embodiment] Fig. 1 is a schematic diagram illustrating a data distribution system. As shown in Fig. 1, the data distribution system 100 includes a transmitting device 10, a receiving device 20, a relay device 30, and a key issuing device 40. For example, the transmitting device 10 is operated by a data provider, the receiving device 20 is operated by a data user, the relay device 30 is operated by an information bank, and the key issuing device 40 is operated by a trusted organization. With the support of the key issuing device 40, the data distribution system 100 distributes encrypted data from the transmitting device 10 to the receiving device 20 via the relay device 30.

[0013] Key issuing device 40 is configured to output a public key / private key pair, transmit the public key to a transmitting device, and hold the private key. The public key is an encryption key for encrypting data, and the private key is a decryption key for decrypting data encrypted with the public key.

[0014] The transmitting device 10 is configured to encrypt data using a public key, create a user-defined policy for each data ID, attach the policy defined for the corresponding data ID to the encrypted data, and transmit the encrypted data with the user-defined policy attached to the relay device 30. The user-defined policy defines the authority to decrypt the encrypted data. For example, the authority is defined by an attribute that allows decryption of the encrypted data.

[0015] The relay device 30 is configured to separate the user-defined policy from the encrypted data and provide the user-defined policy to the key issuing device 40. The encrypted data includes the user-defined policy, and the relay device 30 separates the user-defined policy from the encrypted data.

[0016] The key issuing device 40 is configured to generate a re-encryption key using the private key and a user-defined policy for the corresponding data ID, generate a decryption key for a receiving device 20 that satisfies the user-defined policy to decrypt the re-encrypted data, transmit the re-encryption key to the relay device 30, and transmit the decryption key to the receiving device 20 that satisfies the user-defined policy. The re-encryption key converts encrypted data that can be decrypted using the private key into different encrypted data that can be decrypted using the decryption key for the user-defined policy. The key issuing device generates the re-encryption key using the private key and the user-defined policy.

[0017] The relay device 30 is configured to re-encrypt the encrypted data of the data ID using a re-encryption key, and transmit the re-encrypted data to the receiving device 20. The re-encrypted data can only be decrypted using a decryption key for the user-defined policy.

[0018] The receiving device 20 is configured to decrypt the re-encrypted data using the decryption key. The key issuing device 40 transmits the decryption key to the receiving device 20 that satisfies the user-defined policy. The re-encrypted data can be decrypted only if the receiving device 20 satisfies the user-defined policy.

[0019] As described above, in a conventional data distribution system using attribute-based PRE, the data owner (data transmission device) generates a re-encryption key, and attribute-based PRE has a high computational cost. In contrast, the transmission device 10 of the above embodiment does not generate a re-encryption key. Therefore, the data distribution system of the above embodiment reduces the workload on the data transmission device 10.

[0020] Figure 2 shows the first step of the data distribution process. As shown in Figure 2, the data owner (a) requests the data provider (transmitter) to register data 1, 2, ..., N, (b) creates a policy for the data, and (c) selects and trusts a key generation center (KGC) (key issuing device). Meanwhile, the key generation center (KGC) (key issuing device) transmits a public key to the data provider (transmitter) and holds its private key.

[0021] 3 shows the second step of the data distribution process. As shown in FIG. 3, the data provider (transmitter) (a) encrypts data 1, 2, ..., N with the public key of the KGC, (b) attaches policies P1, P2, ..., PN to the encrypted data 1, 2, ..., N, and (c) transmits the encrypted data 1, 2, ..., N with the attached policies P1, P2, ..., PN to the information bank (relay device).

[0022] Figure 4 shows the third step of the data distribution process. As shown in Figure 4, the information bank (relay device) (a) analyzes the policy in the encrypted data 1, 2, ..., N, (b) adds additional attributes to the policy as necessary, and then (c) sends only the policy to the key generation center (KGC) (key issuing device). (d) The key generation center (KGC) (key issuing device) generates an (attribute-based) PRE key from the private key and the policy.

[0023] Figure 5 shows the fourth step of the data distribution process. As shown in Figure 5, the information bank (relay device) re-encrypts the encrypted data 1, 2, ..., N. The re-encrypted data can only be decrypted with the correct attribute combination.

[0024] FIG. 6 shows the fifth and sixth steps of the data distribution process. As shown in FIG. 6, a data user transmits his / her attributes to a key generation center (KGC) (key issuing device) to obtain a decryption key. The key generation center (KGC) (key issuing device) generates a decryption key using the attributes and a private key. Here, it is assumed that attribute A1 of data user X satisfies policy P1, but attribute A2 of data user Y does not satisfy policy P1. Therefore, the decryption key of data user X complies with policy P1, but the decryption key of data user Y does not comply with policy P1.

[0025] FIG. 7 shows the seventh and eighth steps of the data distribution process. As shown in FIG. 7, the information bank (relay device) transmits the re-encrypted data to data users who request them. The key generation center (KGC) (key issuing device) transmits a decryption key to each data user. Data user X's decryption key complies with policy P1, so data user X can decrypt the re-encrypted data. However, data user Y's decryption key does not comply with policy P1, so data user Y cannot decrypt the re-encrypted data. In this way, in the data distribution described above, data is protected so that only data users who satisfy policy P1 can decrypt the re-encrypted data 1.

[0026] 8 is a system diagram of a data distribution method in the encryption and re-encryption phases. As shown in FIG. 8, the data distribution method in the encryption and re-encryption phases is executed by the transmitting device 10, the key issuing device 40, and the relay device 30. The transmitting device 10 provides a data ID for data distribution to the key issuing device 40. The key issuing device 40 generates a pair of a public key and a private key (step S11), transmits the public key to the transmitting device 10, and holds the private key. The transmitting device 10 encrypts the data with the public key (step S12), creates a policy for the data ID (step S13), and transmits the encrypted data together with the policy.

[0027] The relay device 30 analyzes the policy in the encrypted data (step 14) and provides the policy to the key issuing device 40. The key issuing device 40 generates a re-encryption key using the private key and the policy for the data ID (step 15) and transmits the re-encryption key to the relay device 30. The relay device 30 re-encrypts the encrypted data using the re-encryption key (step 16). In the above-mentioned data distribution method, the transmitting device 10 does not generate a re-encryption key. Therefore, the data distribution system of the above-mentioned data distribution method reduces the workload on the data transmitting device 10.

[0028] FIG. 9 is a system diagram of the data distribution method in the decryption phase. As shown in FIG. 9, the data distribution method in the decryption phase is executed by the receiving device 20, the key issuing device 40, and the relay device 30. The receiving device 20 provides its own attributes to the key issuing device 40. The key issuing device 40 generates a decryption key using the private key and the attributes (step S21) and transmits the decryption key to the receiving device 20. The receiving device 20 requests data access from the relay device 30, and the relay device 30 transmits the re-encrypted data to the receiving device 20. The receiving device 20 decrypts the re-encrypted data with the decryption key. Because the decryption key is generated according to the attributes of the receiving device 20, the receiving device 20 can perform decryption only if the attributes of the receiving device 20 satisfy the policy for the data ID. In this way, in the data distribution method described above, data is protected so that only receiving devices 20 that satisfy the policy for the data ID can decrypt the re-encrypted data.

[0029] [Second embodiment] Figure 10 shows multiple subpolicies in a data distribution system. As shown in Figure 10, user-defined policy P1 includes multiple subpolicies subP1, subP2, subP3, and subP4 that control individual operations on data. Each subpolicy subP1, subP2, and subP3 defines a policy for a specific operation. For example, subpolicy subP1 defines a policy for a "read" operation, subpolicy subP2 defines a policy for a "modify" operation, and subpolicy subP3 defines a policy for a "share" operation.

[0030] The relay device analyzes multiple subpolicies in the data received from the transmitting device. The key issuing device generates a re-encryption key for access control that complies with the multiple subpolicies. The generated re-encryption key converts the encrypted data into different encrypted data that can only be decrypted by a receiving device that satisfies the subpolicies. For example, a re-encryption key for a "read" operation converts the encrypted data into different encrypted data that can only be decrypted by a receiving device that satisfies the "read" subpolicy. A re-encryption key for a "modify" operation converts the encrypted data into different encrypted data that can only be decrypted by a receiving device that satisfies the "modify" subpolicy. And a re-encryption key for a "share" operation converts the encrypted data into different encrypted data that can only be decrypted by a receiving device that satisfies the "share" subpolicy. Here, the attribute of the "share" operation does not allow the "read" operation or the "write" operation to be decrypted. Similarly, a subsequent party receiving the shared data cannot perform any operations on the data because the data is encrypted according to a different policy.

[0031] FIG. 11 illustrates the seventh step of the data distribution process. As shown in FIG. 11, the information bank (relay device) transmits the re-encrypted data to data users who request them. The key generation center (KGC) (key issuing device) generates decryption keys for decrypting the re-encrypted data by receiving devices that satisfy the user-defined policy and subpolicies, and transmits the decryption keys to each data user (receiving device). If attribute A1 satisfies only the subpolicy for "read," the generated decryption key can only be used for "read." Because the decryption key for data user X complies with the subpolicy for "read," data user X can only decrypt the re-encrypted data for "read," but because the decryption key for data user Y does not comply with the subpolicy, data user Y cannot decrypt the re-encrypted data at all. In this way, in the data distribution described above, data is protected so that only data users who satisfy the subpolicy for "read" can decrypt the re-encrypted data 1.

[0032] FIG. 12 is a system diagram of a data distribution method in the re-encryption phase. As shown in FIG. 12, the data distribution method in the re-encryption phase is executed by the transmitting device 10, the key issuing device 40, and the relay device 30. The transmitting device 10 creates a subpolicy for the data ID (step S31) and transmits encrypted data together with the subpolicy. The relay device 30 analyzes the first subpolicy in the encrypted data (step 32) and provides the first subpolicy to the key issuing device 40. The key issuing device 40 generates a first re-encryption key using the private key and the first subpolicy for the data ID (step 33) and transmits the first re-encryption key to the relay device 30. The relay device 30 analyzes the second subpolicy in the encrypted data (step 34) and provides the second subpolicy to the key issuing device 40. The key issuing device 40 generates a second re-encryption key using the private key and the second subpolicy for the data ID (step 35) and transmits the second re-encryption key to the relay device 30. The relay device 30 re-encrypts the encrypted data with each re-encryption key (step 36).

[0033] [Third embodiment] 13 is a system diagram of a data distribution method in the decryption key issuance phase. As shown in FIG. 13, the data distribution method in the decryption key issuance phase is executed by the receiving device 20, the key issuing device 40, and the relay device 30. The receiving device 20 provides its own attributes to the relay device 30. The relay device 30 checks whether the attributes satisfy the data policy corresponding to the requested operation (step S41) and provides the authenticated attributes to the key issuing device 40. The key issuing device 40 generates a decryption key using the private key and the authenticated attributes (step S42) and transmits the decryption key to the receiving device 20. In the above-described data distribution method, the relay device 30 checks whether the attributes satisfy the data policy corresponding to the requested operation, so that data is more securely protected.

[0034] [Hardware configuration] Fig. 14 is a diagram showing an example of the hardware configuration of a transmitting device, a receiving device, a relay device, and a key issuing device. The transmitting device 10, receiving device 20, relay device 30, and key issuing device 40 described above can be configured as an information processing device (computer) 200 having the hardware configuration shown in Fig. 14. However, the hardware configuration example shown in Fig. 14 is an example of a hardware configuration that realizes the functions of the transmitting device 10, receiving device 20, relay device 30, and key issuing device 40, and is not intended to limit the hardware configuration of the transmitting device 10, receiving device 20, relay device 30, and key issuing device 40. The transmitting device 10, receiving device 20, relay device 30, and key issuing device 40 may include hardware not shown in Fig. 14.

[0035] As shown in FIG. 14, a computer 200 includes a CPU (Central Processing Unit) 210, a main memory device 220, an auxiliary memory device 230, and a NIC (Network Interface Card) 240 which is a communication interface, which are interconnected by an internal bus, for example.

[0036] The CPU 210 executes an access control program. The main storage device 220 is, for example, a RAM (Random Access Memory), and temporarily stores the access control program executed by the computer 200 so that the CPU 210 can process it.

[0037] The auxiliary storage device 230 is, for example, a hard disk drive (HDD) and is capable of storing the data distribution program for the medium to long term. The access control program can be provided as a computer program recorded on a non-transitory computer-readable storage medium. The auxiliary storage device 230 can be used to store the access control program recorded on the non-transitory computer-readable storage medium for the medium to long term.

[0038] The NIC 240 provides an interface to external devices over a network. The NIC 240 is used to send and receive traffic communications.

[0039] By executing the data distribution program on the computer 200 as described above, the computer 200 operates as the transmitting device 10, the receiving device 20, the relay device 30, and the key issuing device 40, thereby realizing the data distribution method shown in Figures 8, 9, 12, and 13.

[0040] Some or all of the above embodiments may be described as, but are not limited to, the following supplementary notes. [Appendix 1] A data distribution system that distributes encrypted data from a transmitting device to a receiving device via a relay device with support of a key issuing device, comprising: the key issuing device is configured to output a public key / private key pair, transmit the public key to the transmitting device, and retain the private key; the transmitting device is configured to encrypt data using the public key, create a user-defined policy for each data ID, attach the defined policy for the corresponding data ID to the encrypted data, and transmit the encrypted data with the user-defined policy attached to the relay device; the relay device is configured to separate the user-defined policy from the encrypted data and provide the user-defined policy to the key issuing device; the key issuing device is configured to generate a re-encryption key using the private key and the user-defined policy for the corresponding data ID, generate a decryption key for the receiving device that satisfies the user-defined policy to decrypt the re-encrypted data, transmit the re-encryption key to the relay device, and transmit the decryption key to the receiving device that satisfies the user-defined policy; the relay device is configured to re-encrypt the encrypted data of the data ID using the re-encryption key and transmit the re-encrypted data to the receiving device; the receiving device is configured to decrypt the re-encrypted data using the decryption key; Data distribution system. [Appendix 2] the user-defined policy includes a plurality of sub-policies that control individual operations on the data; the relay device is configured to analyze the plurality of sub-policies in the data received from the sending device; the key issuing device is configured to generate the re-encryption key for access control so as to conform to the plurality of sub-policies. 1. A data distribution system as described in Appendix 1. [Appendix 3] the receiving device is configured to provide its attributes to the relay device to request an operation on the data; the relay device is configured to verify whether the attribute satisfies a data policy corresponding to the requested operation, and provide the authenticated attribute to the key issuing device; the key issuing device is configured to generate the decryption key using the authenticated attribute and transmit the decryption key to the receiving device that has requested the operation on the data. 10. The data distribution system according to claim 1 or 2. [Appendix 4] 1. A data distribution method for distributing encrypted data from a transmitting device to a receiving device via a relay device with support of a key issuing device, comprising: outputting a public key and a private key pair by the key issuing device, transmitting the public key to the transmitting device, and holding the private key; encrypting data using the public key by the transmitting device, creating a user-defined policy for each data ID, attaching the user-defined policy for the corresponding data ID to the encrypted data, and transmitting the encrypted data with the user-defined policy attached to the relay device; separating the user-defined policy from the encrypted data by the relay device and providing the user-defined policy to the key issuing device; generating a re-encryption key by the key issuing device using the private key and the user-defined policy for the corresponding data ID, generating a decryption key for the receiving device that satisfies the user-defined policy to decrypt the re-encrypted data, transmitting the re-encryption key to the relay device, and transmitting the decryption key to the receiving device that satisfies the user-defined policy; re-encrypting the encrypted data of the data ID using the re-encryption key by the relay device, and transmitting the re-encrypted data to the receiving device; decrypting the re-encrypted data using the decryption key by the receiving device; A data distribution method including: [Appendix 5] the user-defined policy includes a plurality of sub-policies that control individual operations on the data; The method comprises: analyzing, by the relay device, the plurality of sub-policies in the data received from the transmitting device; generating, by the key issuing device, the re-encryption key for access control so as to conform to the plurality of sub-policies; 5. The data distribution method of claim 4, comprising: [Appendix 6] the receiving device provides its attribute to the relay device to request an operation on the data; verifying, by the relay device, whether the attribute satisfies a data policy corresponding to the requested operation, and providing the authenticated attribute to the key issuing device; generating the decryption key by the key issuing device using the authenticated attribute, and transmitting the decryption key to the receiving device that has requested the operation on the data; 6. The data distribution method according to claim 4 or 5, comprising: [Appendix 7] A data distribution program for distributing encrypted data from a transmitting device to a receiving device via a relay device with support from a key issuing device, causing the key issuing device to output a pair of a public key and a private key, to transmit the public key to the transmitting device, and to hold the private key; causing the transmitting device to encrypt data using the public key, create a user-defined policy for each data ID, attach the user-defined policy for the corresponding data ID to the encrypted data, and transmit the encrypted data with the user-defined policy attached to the relay device; causing the relay device to separate the user-defined policy from the encrypted data and provide the user-defined policy to the key issuing device; causing the key issuing device to generate a re-encryption key using the private key and the user-defined policy for the corresponding data ID, to generate a decryption key for the receiving device that satisfies the user-defined policy to decrypt the re-encrypted data, to transmit the re-encryption key to the relay device, and to transmit the decryption key to the receiving device that satisfies the user-defined policy; causing the relay device to re-encrypt the encrypted data of the data ID using the re-encryption key and transmit the re-encrypted data to the receiving device; causing the receiving device to decrypt the re-encrypted data using the decryption key; A data distribution program including: [Appendix 8] the user-defined policy includes a plurality of sub-policies that control individual operations on the data; The program causing the relay device to analyze the plurality of sub-policies in the data received from the transmitting device; causing the key issuing device to generate the re-encryption key for access control so as to conform to the plurality of sub-policies; 8. The data distribution program according to claim 7, [Appendix 9] causing the receiving device to provide its attributes to the relay device to request an operation on the data; causing the relay device to verify whether the attribute satisfies a data policy corresponding to the requested operation, and providing the authenticated attribute to the key issuing device; causing the key issuing device to generate the decryption key using the authenticated attribute and to transmit the decryption key to the receiving device that has requested the operation on the data; 9. The data distribution program according to claim 7 or 8,

[0041] Although various embodiments of the present invention have been described above, modifications and adjustments of the embodiments and examples are possible within the scope of the entire disclosure of the present invention (including the claims), and further based on the basic technical concept thereof. Furthermore, various combinations and selections (or at least partial deletions) of various disclosed elements (including each element of each claim, each element of each embodiment or example, each element of each drawing, etc.) are possible within the scope of the entire disclosure of the present invention. In other words, the present invention naturally includes various modifications and alterations that would be possible by a person skilled in the art in accordance with the entire disclosure, including the claims, and its technical concept. In particular, with regard to the numerical ranges described herein, any numerical value or subrange included within the range should be construed as specifically described, even if not otherwise specified. The disclosures of the above-cited patent documents, etc., are incorporated herein by reference. [Explanation of symbols]

[0042] 100 Data Distribution System 10 Transmitting device 20 Receiving device 30 Relay Device 40 Key issuing device 200 Information processing equipment (computer) 210 CPU(Central Processing Unit) 220 Main storage 230 Auxiliary storage 240 NIC(Network Interface Card)

Claims

1. A data distribution system that distributes encrypted data from a transmitting device to a receiving device via a relay device with support of a key issuing device, comprising: the key issuing device is configured to output a public key / private key pair, transmit the public key to the transmitting device, and retain the private key; the transmitting device is configured to encrypt data using the public key, create a user-defined policy for each data ID, attach the defined policy for the corresponding data ID to the encrypted data, and transmit the encrypted data with the user-defined policy attached to the relay device; the relay device is configured to separate the user-defined policy from the encrypted data and provide the user-defined policy to the key issuing device; the key issuing device is configured to generate a re-encryption key using the private key and the user-defined policy for the corresponding data ID, generate a decryption key for the receiving device that satisfies the user-defined policy to decrypt the re-encrypted data, transmit the re-encryption key to the relay device, and transmit the decryption key to the receiving device that satisfies the user-defined policy; the relay device is configured to re-encrypt the encrypted data of the data ID using the re-encryption key and transmit the re-encrypted data to the receiving device; the receiving device is configured to decrypt the re-encrypted data using the decryption key; Data distribution system.

2. the user-defined policy includes a plurality of sub-policies that control individual operations on the data; the relay device is configured to analyze the plurality of sub-policies in the data received from the sending device; the key issuing device is configured to generate the re-encryption key for access control so as to conform to the plurality of sub-policies.

2. The data distribution system according to claim 1.

3. the receiving device is configured to provide its attributes to the relay device to request an operation on the data; the relay device is configured to verify whether the attribute satisfies a data policy corresponding to the requested operation, and provide the authenticated attribute to the key issuing device; the key issuing device is configured to generate the decryption key using the authenticated attribute and transmit the decryption key to the receiving device that has requested the operation on the data.

2. The data distribution system according to claim 1.

4. 1. A data distribution method for distributing encrypted data from a transmitting device to a receiving device via a relay device with support of a key issuing device, comprising: outputting a public key and a private key pair by the key issuing device, transmitting the public key to the transmitting device, and holding the private key; encrypting data using the public key by the transmitting device, creating a user-defined policy for each data ID, attaching the user-defined policy for the corresponding data ID to the encrypted data, and transmitting the encrypted data with the user-defined policy attached to the relay device; separating the user-defined policy from the encrypted data by the relay device and providing the user-defined policy to the key issuing device; generating a re-encryption key by the key issuing device using the private key and the user-defined policy for the corresponding data ID, generating a decryption key for the receiving device that satisfies the user-defined policy to decrypt the re-encrypted data, transmitting the re-encryption key to the relay device, and transmitting the decryption key to the receiving device that satisfies the user-defined policy; re-encrypting the encrypted data of the data ID using the re-encryption key by the relay device, and transmitting the re-encrypted data to the receiving device; decrypting the re-encrypted data using the decryption key by the receiving device; A data distribution method including:

5. the user-defined policy includes a plurality of sub-policies that control individual operations on the data; The method comprises: analyzing, by the relay device, the plurality of sub-policies in the data received from the transmitting device; generating, by the key issuing device, the re-encryption key for access control so as to conform to the plurality of sub-policies; 5. The data distribution method according to claim 4, further comprising:

6. the receiving device provides its attribute to the relay device to request an operation on the data; verifying, by the relay device, whether the attribute satisfies a data policy corresponding to the requested operation, and providing the authenticated attribute to the key issuing device; generating the decryption key by the key issuing device using the authenticated attribute, and transmitting the decryption key to the receiving device that has requested the operation on the data; 5. The data distribution method according to claim 4, further comprising:

7. A data distribution program for distributing encrypted data from a transmitting device to a receiving device via a relay device with support from a key issuing device, causing the key issuing device to output a pair of a public key and a private key, to transmit the public key to the transmitting device, and to hold the private key; causing the transmitting device to encrypt data using the public key, create a user-defined policy for each data ID, attach the user-defined policy for the corresponding data ID to the encrypted data, and transmit the encrypted data with the user-defined policy attached to the relay device; causing the relay device to separate the user-defined policy from the encrypted data and provide the user-defined policy to the key issuing device; causing the key issuing device to generate a re-encryption key using the private key and the user-defined policy for the corresponding data ID, to generate a decryption key for the receiving device that satisfies the user-defined policy to decrypt the re-encrypted data, to transmit the re-encryption key to the relay device, and to transmit the decryption key to the receiving device that satisfies the user-defined policy; causing the relay device to re-encrypt the encrypted data of the data ID using the re-encryption key and transmit the re-encrypted data to the receiving device; causing the receiving device to decrypt the re-encrypted data using the decryption key; A data distribution program including:

8. the user-defined policy includes a plurality of sub-policies that control individual operations on the data; The program causing the relay device to analyze the plurality of sub-policies in the data received from the transmitting device; causing the key issuing device to generate the re-encryption key for access control so as to conform to the plurality of sub-policies; 8. The data distribution program according to claim 7, further comprising:

9. causing the receiving device to provide its attribute to the relay device to request an operation on the data; causing the relay device to verify whether the attribute satisfies a data policy corresponding to the requested operation, and providing the authenticated attribute to the key issuing device; causing the key issuing device to generate the decryption key using the authenticated attribute and to transmit the decryption key to the receiving device that has requested the operation on the data; 8. The data distribution program according to claim 7, further comprising:

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