JP2018093409A - Encrypted data circulation system and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrypt information in an intermediate route by using each other's encryption keys when data is distributed from a transmitting side terminal to a receiving side terminal via a plurality of relays and these relays collude. There is a risk of leakage. SOLUTION: The conversion key issuing server is provided, only the conversion key issuing server holds the encryption key for generating the conversion key, and the conversion key for performing re-encryption from the receiving side terminal to the transmitting side terminal is generated and issued. Since the relay device does not have the encryption key for generating the conversion key and holds only the conversion key issued by the conversion key issuer, it reduces the risk of information leakage due to decryption of the encrypted data on the way. be able to. [Selection diagram] Fig. 1

Description

  The present invention relates to a technique for encrypting and sending data to a plurality of information users via a plurality of relayers.

  With the development of information systems, it is becoming common for multiple information senders who send information and information users who use information to be connected to each other through the Internet and to distribute various information. . Also, as the number of information senders and information users increases, information relay service providers called portal sites that manage the main information senders and information users together and relay information distribution are becoming necessary. ing.

  In the above form, the relayer relays not only the encryption of the communication path but also the information sender to the information user in response to the risk of information leakage on the intermediate route due to information exploitation or internal fraud, although information is relayed In some cases, it is desirable that the information data is encrypted.

  When the information to be distributed is personal information, it is necessary to prevent the information from leaking to information users other than the provision destination permitted by the intention of the information sender. In addition, there are various types of information users who use personal information, and since there are different ways of utilizing data and the range of required personal information, there are some organizations (policy mediation organizations) such as industry organizations. After the usage policy is established, data usage is made according to the policy.

  As a conventional technique related to information distribution with the relayer interposed as described above, a method of re-encrypting encrypted data at the time of information relay is known as in Patent Document 1.

Japanese Patent Laying-Open No. 2015-073238

  However, Patent Document 1 discloses a form in which both parties holding one relay person hold an encryption key, but does not disclose a form through a plurality of relay persons. For this reason, when a plurality of relayers make a collusion, there is a problem that it becomes possible to decrypt information along the route by using the encryption keys of each other.

  The present invention is a system that distributes encrypted information without being decrypted even once through a multistage relay between information receivers, even when a plurality of relayers on the information distribution route collide. The purpose is to prevent information leakage due to information decoding on the route.

When sending encrypted data from the sending terminal to the receiving terminal via the relay device,
The transmitting terminal encrypts original data using a first key, and transmits the encrypted first encrypted data to the first relay device;
Using the second key, the first relay device converts the first encrypted data transmitted from the transmitting terminal into second encrypted data, and converts the second encrypted data to the second encrypted data. To the second relay device,
Using the third key, the second relay device converts the second encrypted data transmitted from the first relay device into third encrypted data, and the third encryption Store data,
The receiving terminal requests the second relay device to transmit the third encrypted data, receives the third encrypted data, and uses the fourth key to perform the third encryption. The original data is decrypted from the data.

  Each relay device does not have an encryption key for generating a conversion key, and only holds the conversion key issued by the conversion key issuer. The risk of information leakage cannot be reduced.

It is a figure which illustrates the outline of an encryption key conversion system. It is a figure explaining the process which performs the conversion key registration application for information users. It is a figure explaining the process which performs the conversion key registration application for information senders. It is a figure explaining the process which transmits and accumulate | stores the encryption data of an information sender. It is a figure explaining the process in which an information user acquires and browses encryption data.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 is a schematic diagram of an information distribution system. As shown in the figure, the information relay system includes one or more user terminals 120 (120-A, 120-B) used by information senders and one or more information use servers 140 (used by information users). 140-1, 140-2), one or more information relayer's portal server 100, an information relayer's policy arbitration server 180, a conversion key issuing server 160 for issuing a conversion key for re-encryption, It has. The user terminal 120, the information use server 140, the portal server 100, one or more policy arbitration servers 180 (180-1, 180-2), and the conversion key issuing server 160 can exchange information with each other via the network 199. .

  Next, the functional outline of each device constituting the system of FIG. 1 will be described.

  The information use server 140 includes a control unit 141, an encryption processing unit 142, a communication unit 143, an input / output unit 144, an encryption key storage unit 151, and an information storage unit 152.

  The information storage unit 152 stores encrypted data received via the portal server 100 and the policy arbitration server 180, and the encryption key storage unit 151 stores an encryption key for decrypting the encrypted data. Remembered.

  The encryption processing unit 142 generates an encryption key for decrypting the encrypted data, decrypts the encrypted data stored in the information storage unit 152 with the encryption key stored in the encryption key storage unit 151, etc. It has functions related to cryptographic processing in general.

  The communication unit 143 relates to processing for transmitting and receiving information (encryption key, encrypted data, etc.) via the network 199 among the user terminal 120, the policy arbitration server 180, the conversion key issuing server 160, and the portal server 100. It has a function.

  The input / output unit 144 has a function of accepting input from an information user and displaying information to the information user.

  The control unit 141 has a function of controlling the overall processing of each unit provided in the information use server 140. For example, the encrypted data is read from the information storage unit 142, the specified encryption key is read from the encryption key storage unit 151, the encrypted data and the encryption key are input to the encryption processing unit 142, and the decryption process is performed by the encryption processing unit 142. By performing this, the entire processing such as decryption of the encrypted data is controlled.

  The portal server 100 includes a control unit 101, an encryption processing unit 102, a communication unit 103, a conversion key storage unit 111, and an encrypted data storage unit 112.

  The encrypted data storage unit 112 stores the received encrypted data and the data re-encrypted by the portal server 100, and the conversion key storage unit 111 has a conversion key and the like re-encrypted by the portal server 100. Remembered.

  The encryption processing unit 102 generates a conversion key, re-encrypts data stored in the encrypted data storage unit 112 with a conversion key stored in the conversion key storage unit 111, and generates encrypted data. It has functions related to cryptographic processing in general.

  The communication unit 103 has a function related to processing for transmitting / receiving information (such as a conversion key and encrypted data) via the network 199 between the user terminal 120 and the information use server 140 and the policy arbitration server 180.

  The control unit 101 has a function of controlling the overall processing of each unit provided in the portal server 100. For example, the encrypted data is read from the encrypted data storage unit 112, the re-encryption key designated from the conversion key storage unit 111 is read, the encrypted data and the re-encryption key are input to the encryption processing unit 102, and the encryption processing unit 102 Thus, re-encryption processing is performed to generate encrypted data, and overall processing such as storing encrypted data in the encrypted data storage unit 112 is controlled.

  The policy arbitration server 180 includes a control unit 181, an encryption processing unit 182, a communication unit 183, a conversion key storage unit 191, and an encrypted data storage unit 192.

  The encrypted data storage unit 192 stores the received encrypted data and the data re-encrypted by the policy arbitration server 180, and the conversion key storage unit 191 stores a conversion key to be re-encrypted by the policy arbitration server 180. Remembered.

  The encryption processing unit 182 generates a conversion key, re-encrypts the data stored in the encrypted data storage unit 192 with the conversion key stored in the conversion key storage unit 191, and generates encrypted data. It has functions related to cryptographic processing in general.

  The communication unit 183 has a function related to processing for transmitting and receiving information (such as a conversion key and encrypted data) via the network 199 between the user terminal 120 and the information use server 140 and the portal server 120.

  The control unit 181 has a function of controlling the overall processing of each unit provided in the policy arbitration server 180. For example, the encrypted data is read from the encrypted data storage unit 192, the re-encryption key designated from the conversion key storage unit 191 is read, the encrypted data and the re-encryption key are input to the encryption processing unit 182, and the encryption processing unit 182 is read. Thus, re-encryption processing is performed to generate encrypted data, and overall processing such as storing encrypted data in the encrypted data storage unit 192 is controlled.

  The conversion key issuing server 160 includes a control unit 161, an encryption processing unit 162, a communication unit 163, an input / output unit 164, and a conversion key storage unit 171.

  The conversion key storage unit 171 stores a conversion key that is re-encrypted by the portal server 100.

  The cryptographic processing unit 162 has functions related to overall cryptographic processing such as generation of a conversion key.

  The communication unit 163 has a function related to processing for transmitting and receiving information (such as a conversion key) via the network 199 between the user terminal 120 and the information use server 140 and the portal server 120.

  The input / output unit 164 has a function of accepting input from the conversion key issuing server administrator and displaying information.

  The control unit 161 has a function of controlling the overall processing of each unit provided in the conversion key issuing server 160.

  The user terminal 120 includes a control unit 121, an encryption processing unit 122, a communication unit 123, an encryption key storage unit 131, an input / output unit 124, and an information storage unit 132.

  The information storage unit 132 stores data transmitted through the portal server 100, and the encryption key storage unit 131 stores an encryption key for encrypting the transmitted data.

  The encryption processing unit 122 generates an encryption key for encrypting data to be transmitted, and encrypts data stored in the information storage unit 132 with an encryption key stored in the encryption key storage unit 131 to generate encrypted data. It has functions related to all cryptographic processes such as generating.

  The communication unit 123 relates to processing for transmitting and receiving information (encryption key, encrypted data, etc.) via the network 199 among the portal server 100, the policy arbitration server 180, the conversion key issuing server 160, and the information use server 140. It has a function.

  The input / output unit 124 has a function of receiving input from a user and displaying information to the user.

  The control unit 121 has a function of controlling the overall processing of each unit provided in the user terminal 120. For example, the data to be encrypted is read from the information storage unit 132, the specified encryption key is read from the encryption key storage unit 131, the data to be encrypted and the encryption key are input to the encryption processing unit 122, and the encryption processing unit 122 Encrypted data is generated by performing encryption processing, and overall processing such as transmitting encrypted data generated by the communication unit 123 to the portal server 100 via the network 199 is controlled.

  The devices of the user terminal 120, the portal server 100, the information use server 140, the policy arbitration server 180, and the conversion key issue server 160 illustrated in FIG. 1 are an external storage device such as a CPU, a memory, and a hard disk. A communication device for communicating with other devices via a network, an input device such as a keyboard and a mouse, an output device such as a display device and a printer, and a reading device that reads information from a portable storage medium It is a general electronic computer. Each processing unit (121, 122, etc.) of each server described above is realized by reading various programs into the CPU. Not only the method of realizing each function by the CPU, but also each may be realized by a module, that is, realized as individual hardware.

  The encryption processing unit 122 of the user terminal 120, the encryption processing unit 102 of the portal server 100, the encryption processing unit 142 of the information use server 140, the encryption processing unit 182 of the policy arbitration server 180, and the encryption processing unit 162 of the conversion key issuing server 160 The encryption method implemented in and will be described below.

Here, data obtained by encrypting the information M to be encrypted with the encryption key K by the encryption operation f of the encryption method is described as f (K, M), and an operation between the encryption key K ₁ and the encryption key K ₂ Describe the new encryption key with “・” as K ₁ and K ₂ . Also, the encrypted data f (K, M) can be decrypted into the information M using the encryption key K.

As a first property of the encryption method, by performing encryption key conversion operation U using re-encryption key K ₁ on data f (K ₂ , M) obtained by encrypting information M with encryption key K ₂ The data f (K ₁ · K ₂ , M) encrypted with the encryption keys K ₁ and K ₂ can be converted.

U (K ₁ , f (K ₂ , M)) = f (K ₁ · K ₂ , M) (Equation 1)
The first property using an encryption key K _2, the encryption key K ₁ inverse of the encryption key K ₁ ^-1 related operation "," with a cryptographic key between possible generation from re-encryption generated by If the key is K ₂ · K ₁ ⁻¹ , the following relationship holds.

U (K ₂ · K ₁ ^-1 , f (K ₁ , M)) = f (K ₂ · K ₁ ^-1 · K ₁ , M) = f (K ₂ , M) (Equation 1-1)
That is, using the re-encryption key K ₂ · K ₁ ^-1 , the encrypted data f (K ₁ , M) encrypted with the encryption key K ₁ is encrypted with the encryption key K ₂ without being decrypted. Can be converted into encrypted data f (K ₂ , M).

Further, by using a method in which the inverse original encryption key K ₁ ^-1 is the same as the encryption key K ₁ , the following relationship is also established.

U (K ₂ · K ₁ , f (K ₁ , M)) = f (K ₂ · K ₁ ^-1 · K ₁ , M) = f (K ₂ , M) (Equation 1-2)
As a second property of the encryption method, the data f (K ₂ , M) obtained by encrypting the information M with the encryption key K ₂ is re-encrypted with the encryption key K ₁ and f (K ₁ , f (K ₂ , M)) is the data f (K ₁ , M) obtained by encrypting the information M with the encryption key K ₁ and f (K ₂ , f (K ₁ , M)) encrypted again with the encryption key K ₂ is Equally in the order of encryption has commutative nature.

f (K ₁ , f (K ₂ , M)) = f (K ₂ , f (K ₁ , M)) (Equation 2)
As a third property of the encryption method, an operation “•” with encryption keys has the following commutability.

K ₁ · K ₂ = K ₂ · K ₁ (Equation 3)
FIG. 2 is a diagram illustrating a sequence in which the information use server 140 registers the conversion key in the policy arbitration server 180 in cooperation with the conversion key issuing server 160 in the present embodiment.

First, the information use server 1 (140-1) sends an application for registration of an information use key to the policy mediation server 180 at the communication unit 143 (S201), and the policy mediation server 180 uses the disposable key at the encryption processing unit 182. K _q is generated and held in the conversion key storage unit 191 (S202), and the disposable key K _q is sent to the information providing server 1 (140-1) by the communication unit 183 (S203).

Then, the information providing server 1 (140-1) is to generate a secret key K _x as an encryption key for the server in the encryption processing section 142 holds the encryption key storage unit 151 (S204), the encryption processing unit 142 Then, a conversion key K _q · K _x that is a source of the server conversion key is generated (S205).

Next, the information providing server 1 (140-1) sends the re-encryption key K _q · K _x generated in S205 by the communication unit 143 to the conversion key issuing server 160 (S206). Here, the re-encryption key K _q · K _x generated in S205 is data that should not be known except for the information providing server 1 (140-1) and the conversion key issuing server 160, and the encryption communication such as SSL is performed. It is necessary to keep it secret from others by using it.

Next, the conversion key issuing server 160 generates a private key K _i of the information providing server 1 (140-1) for at encryption key processing unit 162 holds the encryption key storage unit 171 (S207), the encryption key The processing unit 162 generates a re-encryption key K _q · K _x · K _i that is a source of the re-encryption key for the information providing server 1 (140-1) (S208), and the communication unit 163 at S208. The generated re-encryption key K _q · K _x · K _i is sent to the policy arbitration server 180 (S209).

Then, the policy mediation server 180, using the encryption key K _q that held the re-encryption key K _q · K _x · K _i received in the conversion key storage unit 191 by the communication unit 183, the encryption processing unit At 182, the re-encryption key K _a · K _i (= K _q · K _q · K _a · K _i = K _q ⁻¹ · K _q · K _a · K _i ) is generated and stored in the conversion key storage unit 191. (S210). Here, since the encryption key K _q held in the encryption storage unit 191 is a disposable key for generating a re-encryption key, it may be discarded.

  Finally, the policy arbitration server 180 sends a key registration application completion notification to the information providing server 1 (140-1) by the communication unit 183, and the communication unit 143 of the information providing server 1 (140-1) notifies the notification. Is received and the process ends (S211).

  FIG. 3 is a diagram illustrating a sequence in which the user terminal 120 registers the personal re-encryption key in the portal server 100 in cooperation with the conversion key issuing server 160 in the present embodiment.

First, the user terminal A (120-A) uses the communication unit 123 to send a re-encryption key registration application for the user to the portal server 100 (S301), and the portal server 100 sends it to the encryption processing unit 102. The disposable key _Kp is generated and held in the conversion key storage unit 111 (S302), and the communication unit 103 sends the disposable key _Kp to the user terminal A (120-A) (S303).

Next, the user terminal A (120-A) generates _a private key Ka as its own encryption key in the encryption processing unit 122 and holds it in the encryption key storage unit 131 (S304). to generate a re-encryption key K _p · K _a which is the source of the re-encryption key for the person Te (S305).

Then, the user terminal A (120-A) is sent to re-encryption key K _p · K _a generated in S305 by the communication unit 123 to convert the key issuing server 160 (S306). Here, the re-encryption key K _p · K _a generated in S305, is known other than the user terminal A (120-A) and the conversion key issuing server 160 is a data do not, the cryptographic communication such as SSL It is necessary to keep it secret from other user terminals, other information providing servers, and portal servers.

Next, the conversion key issuing server 160 retrieves the secret key K _i stored in the encryption key storage unit 171 (S307), the user terminal A (120-A) for the re-encryption by the encryption key processing unit 162 generates a re-encryption key K _p · K _a · K _i as the encryption key of the original (S308), re-encryption key K _p · K _a · K _i portal server that generated in S308 by the communication unit 143 100 (S319).

Next, the portal server 100 using the encryption key K _p that held the re-encryption key K _p · K _a · K _i received in the conversion key storage unit 111 by the communication unit 103, the encryption processing unit 102, the re-encryption key K _a · K _i (= K _p · K _p · K _a · K _i = K _p ^-1 · K _p · K _a · K _i ) is generated and held in the conversion key storage unit 111. (S310). Here, the encryption key K _p held in the encryption storage unit 111 is a disposable key for generating a re-encryption key, and may be discarded.

  Finally, the portal server 100 sends a key registration application completion notification to the user terminal A (120-A) by the communication unit 103, and the communication unit 123 of the user terminal A (120-A) notifies the notification. And the process is terminated (S311).

  FIG. 4 is a diagram showing a sequence in which the user terminal 120 encrypts and sends information for a specific policy arbitration server 180 to the portal server 100 in the present embodiment.

  First, the user terminal A (120-A) generates information M to be sent to the policy arbitration server 180 and stores it in the information storage unit 122 (S401).

Next, the user terminal A (120-A) holds the information M to be sent to the policy arbitration server 180 held in the information storage unit 132 in the encryption key storage unit 131 in the encryption processing unit 122. by encrypting the secret key K _a of there, to generate encrypted data _{f (K a, M) (} S402).

Next, the user terminal A (120-A) sends the generated encrypted data f (K _a , M) to the portal server 100 through the communication unit 123 (S403).

Next, the portal server 100 uses the encryption processing unit 102 for the policy arbitration server 180 that holds the encrypted data f (K _a , M) received by the communication unit 103 in the conversion key storage unit 111. Encrypted data f (K _i , M) is generated by re-encrypting using the re-encryption key K _a · K _i (S404). Here, the process of generating the encrypted data f (K _i , M) is shown below.

U (K _a・ K _i , f (K _a , M _{1, a} )) = f (K _a・ K _i・ K _a , M _{1, a} )) = f (K _i , M _{1, a} )
Next, the portal server 100 sends the generated encrypted data f (K _i , M) to the policy arbitration server 180 through the communication unit 103 (S405).

Next, the policy arbitration server 180 uses the encryption processing unit 182 for the policy arbitration server 180 that holds the encrypted data f (K _i , M) received by the communication unit 183 in the conversion key storage unit 191. Encrypted data f (K _x , M) is generated by re-encryption using the re-encryption key K _x · K _i (S406). Here, the process of generating the encrypted data f (K _x , M) is shown below.

U (K _x・ K _i , f (K _i , M _{1, a} )) = f (K _x・ K _i・ K _i , M)) = f (K _x , M)
Finally, the portal server 100 holds the encrypted data f (K _x , M) generated in S405 in the encrypted data storage unit 112, and ends the process (S406).

  FIG. 5 is a diagram illustrating a sequence in which the information use server 140 acquires and decrypts encrypted data from the policy arbitration server 180 and browses the decrypted information in the present embodiment.

First, the information providing server 1 (140-1) sends an information request to the policy arbitration server 180 through the communication unit 143 (S501), and the policy arbitration server 180 stores the encrypted data f stored in the information storage unit 192. (K _x , M) is read, and the encrypted data f (K _x , M) read by the communication unit 183 is sent to the information providing server 1 (140-1) (S502).

Next, the information providing server 1 (140-1) uses the encryption processing unit 142 to store the encrypted data f (K _x , M) received in S502 in the encryption key storage unit 151 with the secret key K _x. By decoding, information M is generated (S504).

  Finally, the information user browses the information M decrypted in S504 and ends the process.

DESCRIPTION OF SYMBOLS 100 ... Portal server, 101 ... Control part, 102 ... Encryption processing part, 103 ... Communication part, 111 ... Conversion key storage part, 112 ... Encrypted data storage part, 120 ... User terminal, 121 ... Control unit, 122 ... Encryption processing unit, 123 ... Communication unit, 124 ... Input / output unit, 131 ... Encryption key storage unit, 132 ... Information storage unit 140 ... Information providing server 141 ... Control unit 142 ... Cryptographic processing unit 143 ... Communication unit 144 ... Input / output unit 151 ... Cryptographic key storage unit 152 ... Information storage unit, 160 ... Conversion key issuing server, 161 ... Control unit, 162 ... Cryptographic processing unit, 163 ... Communication unit, 164 ... Input / output unit, 171 ..Encryption key storage unit, 180 ... policy arbitration server, 181 ... control , 182 ... encryption unit, 183 ... communication unit, 191 ... conversion key storage unit, 192 ... encrypted data storage unit, 199 ... network

Claims (6)

In an encrypted data distribution system for transmitting encrypted data from a transmission side terminal to a reception side terminal via a first relay device and a second relay device,
The transmitting terminal transmits a cipher processing unit of the transmitting terminal that encrypts original data using a first key, and transmits the encrypted first encrypted data to the first relay device. A communication unit of the side terminal,
The first relay device uses a second key to convert the first encrypted data transmitted from the transmission side terminal into second encrypted data, and a cryptographic processing unit of the first relay device; A communication unit of a first relay device that transmits the second encrypted data to the second relay device,
The second relay device uses a third key to convert the second encrypted data transmitted from the first relay device into third encrypted data. A processing unit, and a storage unit for storing the third encrypted data,
The receiving-side terminal requests the second relay device to transmit the third encrypted data and receives the third encrypted data, and the third key using the fourth key. An encrypted data distribution system comprising: an encryption processing unit of a receiving terminal that decrypts the original data from the encrypted data. In the encrypted data distribution system according to claim 1,
Furthermore, a conversion key issuing server is provided,
The second secret key is generated from the first secret key generated by the transmitting terminal and the second secret key specific to the receiving terminal generated by the conversion key issuing server. And a third secret key generated by the receiving terminal, and the third key is generated. The encrypted data distribution system according to claim 2,
The conversion key issuing server sends the second key and the third key to a relay device on an information distribution path from the transmitting terminal to the receiving terminal. . In the encrypted data distribution method for transmitting the encrypted data from the transmission side terminal to the reception side terminal via the first relay device and the second relay device,
The transmitting terminal encrypts original data using a first key, and transmits the encrypted first encrypted data to the first relay device;
Using the second key, the first relay device converts the first encrypted data transmitted from the transmitting terminal into second encrypted data, and converts the second encrypted data to the second encrypted data. To the second relay device,
Using the third key, the second relay device converts the second encrypted data transmitted from the first relay device into third encrypted data, and the third encryption Store data,
The receiving terminal requests the second relay device to transmit the third encrypted data, receives the third encrypted data, and uses the fourth key to perform the third encryption. An encrypted data distribution method, comprising: decrypting the original data from data. The encrypted data distribution method according to claim 4,
The second key is generated from a first secret key generated by the transmitting terminal and a second secret key specific to the receiving terminal generated by a conversion key issuing server,
The encrypted data distribution method, wherein the third key is generated from the second secret key and a third secret key generated by the receiving terminal. The encrypted data distribution method according to claim 5,
The encrypted data distribution method, wherein the second key and the third key are sent to a relay device on an information distribution path from the transmission side terminal to the reception side terminal.

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