WO2021186754A1

WO2021186754A1 - Information processing system, information processing method, information processing program, secret sharing system, secret sharing method, secret sharing program, secure computation system, secure computation method, and secure computation program

Info

Publication number: WO2021186754A1
Application number: PCT/JP2020/024944
Authority: WO
Inventors: 泰弘梅本
Original assignee: 株式会社モールサービス
Priority date: 2020-03-17
Filing date: 2020-06-25
Publication date: 2021-09-23

Abstract

The present invention addresses the problem of implementing new information processing.　Implemented is an information processing system including a node constituting a block chain network, wherein the node comprises a sharing means and a restoration means, the sharing means performs secret sharing at least based on generation of a plurality of shares constituting data that the node has, and storage of some of the shares in a newest undetermined block in a block chain stored in the block chain network, and the restoration means acquires the some shares at least from the block chain, and restores the data at least on the basis of the some shares.

Description

Information processing system, information processing method, information processing program, secret sharing system, secret sharing method, secret sharing program, secret calculation system, secret calculation method, and secret calculation program

The present invention relates to an information processing system, an information processing method, an information processing program, a secret sharing system, a secret sharing method, a secret sharing program, a secret calculation system, a secret calculation method, and a secret calculation program.

In recent years, blockchain technology has been attracting attention as a solution for improving tamper resistance in information management systems. Blockchain is being used in a wide range of scenes, not limited to the sending and receiving of tokens with economic value.

Patent Document 1 discloses an invention relating to information management based on an organic combination of blockchain and biometric authentication. The information management has an advantage that tamper resistance can be ensured in an offline environment such as a private network.

There is room for improvement in the above information management from the viewpoint of preferably realizing information processing such as data backup possessed by blockchain nodes.

There is room for improvement in the above information management from the viewpoint of ensuring confidentiality in calculations based on transaction history, etc. indicated by at least some blocks of the blockchain by a third party.

Patent No. 6650157

In view of the above circumstances, the present invention is a problem to be solved for the realization of new information processing.

In order to solve the above problems, the present invention is an information processing system including nodes constituting a blockchain network, the nodes having a distribution means and a restoration means, and the distribution means is the node. The restoration is performed by performing secret sharing based on at least the generation of a plurality of shares constituting the data possessed by the data and the storage of some of the shares in the latest undetermined block in the blockchain stored in the blockchain network. The means acquires at least some of the shares from the blockchain and restores the data based on at least some of the shares.

With such a configuration, even when the blockchain is managed in an offline environment such as a private network, it is possible to securely back up the data possessed by the blockchain nodes based on information-theoretic security. can.

In a preferred embodiment of the invention, the decentralizing means further performs the secret sharing based on the storage of the remaining share outside the blockchain, and the restoring means acquires the remaining share from outside the blockchain. Do more.

In a preferred embodiment of the invention, the decentralizing means further performs the secret sharing based on the storage of the remaining share outside the blockchain network, and the restoring means is the remaining share from outside the blockchain network. Further acquisition of.

With such a configuration, even when the blockchain is managed in an offline environment such as a private network, data backup of the blockchain nodes can be realized while ensuring redundancy.

In a preferred embodiment of the present invention, the node further has an authentication means, and the authentication means acquires the feature data of the operator of the node by performing a sensing process, and the template and the feature data of the node. When the result of the authentication process is positive, the distribution means stores a part of the share in the undetermined block, and the restoration means is the result of the authentication process. If is positive, a part of the share is acquired from the blockchain. Further, in a preferred embodiment of the present invention, the feature data is based on face image data.

With such a configuration, the present invention can securely realize backup / restore of data which is confidential information based on a secure authentication process by biometric authentication.

In order to solve the above problems, the present invention is an information processing method in which a node constituting a blockchain network executes a distribution step and a restoration step, and the distribution step constitutes data possessed by the node. Secret sharing is performed based on at least the generation of a plurality of shares and the storage of a part of the shares in the latest undetermined block in the blockchain stored in the blockchain network, and the restoration step is performed at least by the above. Acquire some of the shares from the blockchain and restore the data based on at least some of the shares.

In order to solve the above problems, the present invention is an information processing program that causes a computer to function as a node constituting a blockchain network, and the node has a distribution means and a restoration means, and the distribution means. Creates a plurality of shares that make up the data held by the node, and stores some of the shares in the latest undetermined block in the blockchain stored in the blockchain network, at least based on secret sharing. Then, the restoration means acquires at least a part of the share from the blockchain and restores the data based on at least a part of the share.

In order to solve the above problems, the present invention is a secret sharing system having means for performing secret sharing of data inside and outside the blockchain. Further, the present invention is a secret sharing method in which a computer is made to perform a step of performing secret sharing of data both inside and outside the blockchain. The present invention is also a secret sharing program that causes a computer to function as a means for secret sharing data inside and outside the blockchain.

In order to solve the above problems, the present invention is an information processing system including a node constituting a blockchain network, a client outside the blockchain network, and a server outside the blockchain network. , The client has requesting means, the server has computing means, and the concealment means corresponds to at least one block in the blockchain stored in the blockchain network. After encrypting the snapshot based on the quasi-isomorphic encryption, the snapshot is stored in the server, and the requesting means determines a request based on the transaction stored in the block in the blockchain, and the request is determined. The request is transmitted to the server, and the calculation means performs a secret calculation based on the encrypted snapshot with the reception of the request as a turning point, and corresponds to the request based on the result of the secret calculation. The response is determined and the response is returned to the client.

With such a configuration, the present invention further ensures confidentiality as well as tamper resistance so that a third party can suitably perform calculations based on the transaction history and the like indicated by at least a part of the blocks of the blockchain. It is possible to realize information processing that can be done.

In a preferred embodiment of the present invention, the homomorphic encryption is somehat homomorphic encryption.

In a preferred embodiment of the present invention, the homomorphic encryption is a level 2 homomorphic encryption.

With such a configuration, the present invention provides a secret calculation that enables both additive calculation and multiplication calculation while suppressing the calculation cost in an operation based on at least a part of blocks in the blockchain. It can be realized.

In a preferred embodiment of the present invention, the homomorphic encryption is a fully homomorphic encryption.

In the preferred embodiment of the present invention, the secret calculation is a secret search.

In order to solve the above problems, the present invention causes a node constituting the blockchain network to execute a secret step, a client outside the blockchain network to execute a request step, and a server outside the blockchain network to perform a calculation step. In the information processing method to be executed, in the concealment step, a snapshot corresponding to at least one block in the blockchain stored in the blockchain network is encrypted based on a quasi-isomorphic cipher, and then the snap is performed. The shot is stored in the server, the request step determines a request based on the transaction stored in the block in the blockchain, sends the request to the server, and the calculation step receives the request. As a turning point, a secret calculation based on the encrypted snapshot is performed, a response corresponding to the request is determined based on the result of the secret calculation, and the response is returned to the client.

In order to solve the above problems, the present invention includes a computer, a node that constitutes a blockchain network and has a concealing means, a client that has a requesting means outside the blockchain network, or a computing means outside the blockchain network. An information processing program that functions as a server, in which the concealment means encrypts a snapshot corresponding to at least one block in the blockchain stored in the blockchain network based on a quasi-identical cipher. The snapshot is stored in the server, the requesting means determines a request based on a transaction stored in the block in the blockchain, sends the request to the server, and the computing means of the request. With the reception as a turning point, a secret calculation is performed based on the encrypted snapshot, a response corresponding to the request is determined based on the result of the secret calculation, and the response is returned to the client.

In order to solve the above problems, the present invention is a secret calculation system having means for performing secret calculation based on snapshots of at least a part of blocks in a blockchain.

In order to solve the above problems, the present invention is a secret calculation method in which a computer is made to perform a step of performing a secret calculation based on a snapshot of at least a part of blocks in a blockchain.

In order to solve the above problems, the present invention is a secret calculation program that causes a computer to function as a means for performing secret calculations based on snapshots of at least a part of blocks in a blockchain.

The present invention can realize new information processing.

The hardware block diagram which concerns on one Embodiment of this invention is shown. The functional block diagram which concerns on one Embodiment of this invention is shown. An explanatory diagram of secret sharing according to an embodiment of the present invention is shown. An explanatory diagram of secret sharing according to an embodiment of the present invention is shown. The data 110 which is the secret information S which concerns on one Embodiment of this invention is shown. The functional block diagram which concerns on one Embodiment of this invention is shown. The flowchart of the secret calculation which concerns on one Embodiment of this invention is shown. The flowchart of the secret calculation which concerns on one Embodiment of this invention is shown.

This specification describes the configuration, the action and effect, etc. according to the embodiment of the present invention with reference to the drawings. The present invention is not limited to the following embodiment, and various configurations may be adopted. Further, in one embodiment of the present invention, a part of the configuration in each of the respective embodiments may be adopted with each other as long as the realization of the desired action and effect of the one embodiment of the present invention is not hindered.

Each of the information processing system, the information processing method, the information processing program, and the information processing program medium according to the present invention has the same effect. Each means in the information processing system and each step in the information processing method have the same effect.

Further, each of the secret sharing system, the secret sharing method, the secret sharing program, and the secret sharing program medium according to the present invention has the same effect. Each means in the secret sharing system and each step in the secret sharing method have the same effect.

Further, each of the secret calculation system, the secret calculation method, the secret calculation program, and the secret calculation program medium according to the present invention has the same effect. Each means in the secret calculation system and each step in the secret calculation method have the same effect.

Each means in each of the information processing system, the information processing program, the information processing program medium, the secret sharing system, the secret sharing program, the secret sharing program medium, the secret calculation system, the secret calculation program, and the secret calculation program medium according to the present invention. It can be understood that the action and effect are exerted by a computing device such as a processor described later. Further, it can be understood that the action and effect of each step of the information processing method and the secret sharing method are also realized by the arithmetic device such as the processor.

The information processing program medium and the secret sharing program medium according to the present invention are non-transient recording media in which the information processing program and the secret sharing program are stored, respectively.

<Hardware configuration>
As illustrated in FIG. 1, information processing system, information processing method, information processing program, information processing program medium, secret sharing system, secret sharing method, secret sharing program, secret sharing program medium, secret calculation method, secret calculation program -The secret calculation program medium includes (uses) node 1 which is a known computer.

Node 1 has an arithmetic device 11, a main storage device 12, an auxiliary storage device 13, and a bus interface, and is appropriately used in order to realize the effects exhibited by the present invention. In addition to the above configuration, the node 1 may include an input device 14, an output device 15, a communication device 16, and a detection device 17.

The arithmetic device 11 has a known processor capable of executing an instruction set.
The main storage device 12 has a known volatile memory capable of storing an instruction set.
The auxiliary storage device 13 has a known recording medium capable of recording a program or the like.
The input device 14 is, for example, a known interface capable of inputting intentions.
The output device 15 is a known interface that enables, for example, visual notification.
The communication device 16 has a known interface based on a wired system or a wireless system for realizing connection / participation to at least a part of a network including a public network / private network.
The detection device 17 is a known sensor that enables the sensing process.

Each device in node 1 may not be included in one housing. At least a part of each device in the node 1 (for example, the detection device 17) may have a power supply independent of the node 1 and may be able to communicate with the node 1 main body.

<Functional block>
As illustrated in FIG. 2, the information processing system 0 has a node 1. The node 1 constitutes the blockchain network 2 and is a storage destination of the blockchain 20. The number of nodes 1 in the blockchain network 2 is 2 or more.

<Node 1>
Node 1 preferably has distribution means 101 (corresponding to the distribution step) and restoration means 102 (corresponding to the restoration step). Further, the node 1 may further have an authentication means 103 (corresponding to an authentication step). It can be understood that the node 1 has means (steps) for performing secret sharing of the data 110 inside and outside the blockchain 20 or inside and outside the blockchain network 2.

<Dispersion means 101>
The distribution means 101 generates a plurality of shares 111 constituting the data 110 possessed by the node 1, and stores a part of the shares 111 in the latest undetermined block 21 in the blockchain 20 stored in the blockchain network 2. Perform secret sharing based on.

As illustrated in FIG. 3, the distribution means 101 may perform secret sharing based on the storage of the remaining share 111 outside the blockchain 20. Further, as illustrated in FIG. 4, the distribution means 101 may perform secret sharing based on the storage of the remaining share 111 outside the blockchain network 2.

In the secret sharing according to the embodiment of the present invention, the data 110 corresponds to the secret information S. As illustrated in FIG. 5, the data 110 is a private key possessed by the node 1, and there is no limitation on its type. There is no limit to the number of bits of the private key. As an example, one means of node 1 generates a digital signature based on a transaction stored in an undetermined block 21 on the blockchain 20 and the private key. The plaintext in the digital signature is the transaction or the hash value of the transaction.

The "blockchain 20 stored in the blockchain network 2" in the description in the present specification corresponds to the blockchain 20 stored in a plurality of nodes 1 constituting the blockchain network 2.

"Storing a part of the shares 111 in the undecided block 21" in the description in this specification means, for example, storing a part of the shares 111 as a transaction in the undecided block 21. For the transaction, as an example, an electronic signature is generated by the private key of the node 1 which is the secret information S configured by the share 111.

<Restoration means 102>
The restoring means 102 preferably acquires at least a part of the share 111 from the blockchain 20 and restores the data 110 based on at least a part of the share 111. The restoration means 102 may further acquire the remaining share 111 from outside the blockchain 20. The restoration means 102 may further acquire the remaining share 111 from outside the blockchain network 2.

In the description of the present specification, "acquisition of a part of the share 111 from the blockchain 20" means, for example, that the restoration means 102 has an electronic signature corresponding to the share 111 as a transaction stored in the block, and a node. It can be understood that the transaction is performed after specifying the partial share 111 on the blockchain 20 based on the public key corresponding to 1. At this time, the "public key corresponding to the node 1" is, for example, a public key corresponding to the private key which is the secret information S configured by the share 111.

"Outside the blockchain 20" in the description in this specification means that any of the blocks in the blockchain 20 is not a storage destination of various data. At this time, among the local storage 1ls of the node 1 and the external storage that does not operate independently of the node 1, the area that does not correspond to any of them corresponds to the outside of the blockchain 20. The “external storage that does not operate independently of the node 1” refers to, for example, a non-volatile memory such as a flash memory connected to the node 1 via a physical interface.

"Outside the blockchain network 2" in the description in this specification means that the local storage 1ls of the node 1 constituting the blockchain network 2 is not a storage destination of various data. At this time, the area in the external storage that operates independently of the node 1 corresponds to the outside of the blockchain network 2. The "external storage that operates independently of the node 1" is, for example, cloud storage 1cs.

The secret sharing in one embodiment of the present invention is a secret sharing based on a known method. As an example, the secret sharing divides the secret information S into n shares 111 (corresponding to the distributed information). Confidential information S can be restored based on at least a portion of n shares 111.

In one embodiment of the present invention, the quantity of share 111 (dispersion information) is, for example, n = 3. At this time, the restoration of the secret information S may be performed at least based on the share 111 stored in the undecided block 21 on the blockchain 20.

The secret sharing method in one embodiment of the present invention includes, for example, Shamir secret sharing, Lamp-Shamir secret sharing, Adaptive Secret Sharing, Repeated Adaptive Secret Sharing, and calculation. Type additive secret sharing (Computational Adaptive Secret Sharing), etc., and there are no restrictions on the type.

The storage destinations of the plurality of shares 111 in one embodiment of the present invention may be the undecided block 21, the local storage 1 ls, and the cloud storage 1 cs, and may be the undecided block 21 and the local storage 1 ls. It may be undecided block 21 and cloud storage 1cs.

<Authentication means 103>
The authentication means 103 may perform an authentication process of acquiring the feature data 112 of the operator of the node 1 by performing a sensing process and collating the template 113 and the feature data 112 of the node 1. When the result of the authentication process is positive, the distribution means 101 stores a part of the shares 111 in the undecided block 21. When the result of the authentication process is positive, the restoration means 102 acquires a part of the share 111 from the blockchain 20.

The feature data 112 in one embodiment of the present invention is biological data including the operator's face image data, fingerprint data, palm shape data, retinal data, voice print data, iris data, handwriting data, walking data, vein data, and the like. based on. At this time, it can be understood that the sensing process adopts the optimum method according to the type of feature data 112 / biometric data.

The authentication means 103 determines the similarity based on the N-dimensional vector data indicating each of the feature data 112 and the template 113. If the similarity satisfies a predetermined condition, the result of the authentication process is positive (the authentication process succeeds). The similarity is determined, for example, based on the Euclidean distance or cosine similarity indicated by the N-dimensional vector data.

The template 113 in one embodiment of the present invention may be stored in the local storage 1ls of the node 1 and may be stored in the block on the blockchain 20. Template 113 corresponds to the public key of node 1 as an example. The "public key of the node 1" is, for example, a public key corresponding to the private key which is the secret information S. At this time, the storage / update / change of the template 113 is realized by one means possessed by the node 1.

At this time, if the result of the authentication process based on the template 113 is at least positive, the authentication means 103 may return the public key corresponding to the template 113 to the node 1. The public key is used for the specific use of the share 111 stored in the block on the blockchain 20.

The number of dimensions of the vector data of the feature data 112 is preferably 4096 or more, more preferably 2048 or more, more preferably 1024 or more, more preferably 512 or more, and more preferably 256 or more. More preferably, it is 128 or more.

The feature data 112 is determined through feature extraction for the detection data acquired by the detection device 17. The authentication means 103 includes, for example, calculation processing of an eigenvector by a principal component analysis model, learning and inference processing by a deep learning model such as a convolutional neural network model, learning and classification processing by a decision tree model such as a support vector machine, and so on. One of the algorithms including the extraction process by the gradient direction histogram and the one including is adopted.

<Blockchain network 2>
The blockchain network 2 is composed of a plurality of nodes 1 interconnected in a private network. The plurality of nodes 1 have at least a part of the blockchain 20 (at least the latest undecided block 21). The private network is, for example, an on-site network that is an on-site private network that points to "the place" such as inside an event venue.

<Blockchain 20>
The blockchain 20 may employ a known technique. Further, as one aspect of the blockchain 20, for example, the matters (various chains) described in Japanese Patent No. 6650157 can be adopted. In one embodiment of the present invention, the matters described in Japanese Patent No. 6650157 may be adopted.

Note that the node 1 has a means for finalizing including the generation of a hash value by hashing the undecided block 21 in the blockchain 20. Further, the node 1 has a means for generating a new undecided block 21 in the blockchain 20 after the finalization and adding the hash value to the new undecided block 21. The block in the blockchain 20 appropriately has a transaction corresponding to the electronic signature stored in the block.

It can be understood that the share 111 in one embodiment of the present invention is associated with the index and can be searched. It is determined whether or not the information restored based on the share 111 is the secret information S based on the secret information S (for example, corresponding to the private key possessed by the node 1) and the corresponding public key (the information is correct). Judge whether or not.)

According to the present invention, information processing including backup of data 110 (confidential information S) in the blockchain network 2 that is updated in an offline environment can be securely realized based on information-theoretic security.

<Functional block>
As illustrated in FIG. 6, the information processing system 0 includes a node 1 constituting the blockchain network 2, a client 3 outside the blockchain network 2, and a server 4 outside the blockchain network 2. The node 1 constitutes the blockchain network 2 and is a storage destination of the blockchain 20. The number of nodes 1 in the blockchain network 2 is 2 or more.

<Node 1>
Node 1 has a concealment means 104 (corresponding to a concealment step).

The concealment means 104 encrypts the snapshot 20s corresponding to at least one block in the blockchain 20 stored in the blockchain network 2 based on homomorphic encryption, and generates an encrypted snapshot 20se to generate a snapshot. 20se is transmitted to the server 4 and stored in the server 4.

As used herein, the term "at least one block in the blockchain 20" may refer to a block group containing at least the latest undetermined block 21, and may refer to a block group containing a predetermined block that has already been finalized. good.

Note that the snapshot 20se can be generated by the concealment means 104 and transmitted to the server 4 in real time.

The concealment means 104 may be configured to appropriately define the item name and the like based on the user-defined schema in the blockchain 20 when generating the encrypted data (including the snapshot 20se) related to the blockchain 20. ..

The homomorphic encryption in one embodiment of the present invention may be somehat homomorphic encryption. Further, the homomorphic encryption may be a level 2 homomorphic encryption (L2 homomorphic encryption). Further, the homomorphic encryption may be a fully homomorphic encryption. The homomorphic encryption preferably refers to a known homomorphic encryption that enables multiplication calculation in addition to addition calculation.

The secret calculation in one embodiment of the present invention is, for example, a secret search. There is no limitation on the type of secret calculation in one embodiment of the present invention, and the configuration may be based on secret sharing.

It can be understood that the blockchain 20 in one embodiment of the present invention has a block including a transaction between the node 1 and the client 3.

<Client 3>
Client 3 is a known computer. The client 3 also takes the form of a known computer such as a smartphone, laptop, workstation or the like. The client 3 may have the same hardware configuration as that of the node 1.

Client 3 has request means 301 (corresponding to a request step). Each device possessed by the client 3 is appropriately provided to realize the means including the requesting means 301.

The request means 301 determines the request 310 based on the transaction stored in the block in the blockchain 20, and transmits the request 310 to the server 4. Further, it can be understood that the request means 301 determines the request 310 based on the transaction between the node 1 and the client 3. The request 310 may have a configuration that appropriately includes a request identifier, a time stamp, and transaction details.

In the description of the present specification, the "request 310 based on a transaction stored in a block in the blockchain 20" refers to a request for information disclosure relating to the content of the transaction and / or the calculation result based on the transaction. ..

<Server 4>
The server 4 is a known computer. The server 4 also takes the form of a known computer such as a smartphone, laptop, or workstation. The server 4 may have the same hardware configuration as that of the node 1.

The server 4 has a calculation means 401 (corresponding to a calculation step). Each device included in the server 4 is appropriately provided for realizing means including the calculation means 401.

It can be understood that the server 4 has a means (corresponding to a step) for performing a secret calculation based on the snapshot 20se of at least a part of the blocks in the blockchain 20.

The calculation means 401 performs a secret calculation based on the snapshot 20se with the reception of the request 310 as a turning point, determines the response 410 corresponding to the request 310 based on the result of the secret calculation, and returns the response 410 to the client 3.

<Secret calculation (Example 1)>
As illustrated in FIG. 7, the information processing including the secret calculation in one embodiment of the present invention is performed between the node 1 (at least a part of the nodes 1 in the blockchain network 2), the client 3, and the server 4 as follows. It can be understood that it is executed like this.

First, when the blockchain 20 is updated, the concealment means 104 acquires a snapshot 20s of the blockchain 20 based on the blockchain 20. After that, the concealment means 104 generates the snapshot 20se by encrypting the snapshot 20s based on the homomorphic encryption, and transmits the snapshot 20se to the server 4. In addition, "when the blockchain 20 is updated" means that a new undecided block 21 is generated in the blockchain 20, or a new transaction is stored in the latest undecided block 21 between the nodes 1. Refers to the case where it is broadcast on.

Next, the server 4 transmits the public key 411 corresponding to the private key 413 possessed by the server 4 to the node 1 and / or the client 3. When the node 1 receives the public key 411 from the server 4, the node 1 transmits the public key 411 to the client 3.

Next, the request means 301 transmits the request 310 to the node 1 and / or the server 4. When the node 1 receives the request 310 from the client 3, the node 1 sends the request 310 to the server 4.

The request 310 in the first embodiment is, for example, a general request relating to a credit balance that can be calculated based on a transaction stored in a block in the blockchain 20. The request in general is, for example, a comparison between the credit balance and a predetermined value corresponding to the transaction content. The predetermined value is, for example, a settlement amount. Further, the request in general is, for example, determination of the degree of similarity between the feature data and the template, such as the Euclidean distance.

Next, the calculation means 401 performs a secret calculation based on the snapshot 20se transmitted by the concealment means 104 and the request 310 transmitted by the request means 301. The calculation means 401 determines the response 410 corresponding to the request 310 transmitted by the request means 301 based on the result of the secret calculation, and returns the response 410 to the client 3 corresponding to the request 310.

At this time, the response 410 may be, for example, binary data indicating whether or not the transaction is possible, which corresponds to the above transaction content. Further, at this time, the calculation means 401 may generate an electronic signature 412 in which the response 410 is in plain text based on the private key 413. The calculation means 401 may further make at least a part of the request 310 corresponding to the response 410 in plain text.

Note that, instead of the calculation means 401, the node 1 may determine the response 410 based on the result of the secret calculation by the calculation means 401, and return the response 410 to the client 3. In this case, the node 1 generates an electronic signature in which the response 410 is in plain text based on the private key possessed by the node 1.

Finally, the client 3 verifies the electronic signature 412 based on the public key 411 sent from the server 4 to confirm the validity of the returned response 410.

<Secret calculation (Example 2)>
As illustrated in FIG. 8, the information processing including the secret calculation in one embodiment of the present invention is performed between the node 1 (at least a part of the nodes 1 in the blockchain network 2), the client 3, and the server 4 as follows. It can be understood that it is executed like this.

First, the client 3 transmits the public key 311 corresponding to the private key 313 possessed by the client 3, the selection information 312, and the node 1. As an example, the selection information 312 may take the form of a selection-type questionnaire, or may take the form of a candidate name in an election.

Next, the node 1 stores the transaction based on the selection information 312 in the latest undecided block 21 in the blockchain 20. At this time, the node 1 preferably stores the transaction in the undetermined block 21 after encrypting the transaction based on the public key 311 transmitted from the client 3.

The concealment means 104 acquires a snapshot 20s of the blockchain 20 based on the blockchain 20. After that, the concealment means 104 generates the snapshot 20se by encrypting the snapshot 20s based on the homomorphic encryption, and transmits the snapshot 20se to the server 4.

Next, the request means 301 determines the request 310 based on the transaction based on the selection information 312, and transmits the request 310 to the server 4. The request 310 is, for example, all statistical data that can be determined based on the selection information 312. The statistical data, for example, refers to information on the candidates and the like having the largest number of votes (selected).

Next, the calculation means 401 performs a secret calculation based on the snapshot 20se transmitted by the concealment means 104 and the request 310 transmitted by the request means 301.

The calculation means 401 determines the response 410 corresponding to the request 310 transmitted by the request means 301 based on the result of the secret calculation, and returns the response 410 to the client 3 corresponding to the request 310.

At this time, the response 410 indicates, for example, the candidate with the largest number of votes. Further, at this time, the calculation means 401 may generate an electronic signature 412 in which the response 410 is in plain text based on the private key 413.

Finally, the client 3 verifies the electronic signature 412 based on the public key 411 transmitted from the server 4, confirms the validity of the returned response 410, and makes the response 410 based on the private key 313. Decrypt.

In the secret calculation in one embodiment of the present invention including the first and second embodiments, the client 3 side can identify the node 1 that generated the transaction used for the secret calculation based on the verification result of the electronic signature 412. Is. At this time, information processing for providing an incentive from the client 3 to the specified node 1 can be realized as an example.

According to the present invention, by realizing secret calculation / homomorphic encryption based on at least a part of blocks of the blockchain, it is possible to ensure tamper resistance and confidentiality in information processing based on the blockchain. ..

0: Information processing system 1: Node 2: Blockchain network 3: Client 4: Server 1ls: Local storage 1cs: Cloud storage 2: Blockchain network 11: Computational device 12: Main storage device 13: Auxiliary storage device 14: Input device 15: Output device 16: Communication device 17: Detection device 20: Blockchain 20s: Snapshot 20se: Snapshot 21: Undecided block 101: Distribution means 102: Restoration means 103: Authentication means 104: Concealment means 110: Data 111: Share 112: Feature data 113: Template 301: Request means 310: Request 311: Public key 312: Selection information 313: Private key 401: Calculation means 410: Response 411: Public key 412: Electronic signature 413: Private key S: Secret information

Claims

An information processing system that includes the nodes that make up a blockchain network.
The node has a decentralizing means and a restoring means.
The distribution means is at least based on the generation of a plurality of shares constituting the data held by the node and the storage of some of the shares in the latest undetermined block in the blockchain stored in the blockchain network. Secret sharing,
The restoration means is an information processing system that acquires at least a part of the share from the blockchain and restores the data based on at least a part of the share.
The distribution means further performs the secret sharing based on the storage of the remaining share outside the blockchain, and the restoration means further acquires the remaining share from outside the blockchain. The information processing system described.
The distribution means further performs the secret sharing based on the storage of the remaining share outside the blockchain network, and the restoration means further acquires the remaining share from outside the blockchain network. The information processing system according to 1 or 2.
The node further has an authentication means
The authentication means acquires the feature data of the operator of the node by performing a sensing process, and performs an authentication process for collating the template possessed by the node and the feature data.
When the result of the authentication process is positive, the decentralizing means stores a part of the share in the undecided block.
The information processing system according to any one of claims 1 to 3, wherein the restoration means acquires a part of the share from the blockchain when the result of the authentication process is positive.
The information processing system according to claim 4, wherein the feature data is based on face image data.
It is an information processing method that causes the nodes that make up the blockchain network to execute the distribution step and the restoration step.
The distribution step is at least based on the generation of a plurality of shares constituting the data held by the node and the storage of some of the shares in the latest undetermined block in the blockchain stored in the blockchain network. Secret sharing,
The restoration step is an information processing method that acquires at least a part of the share from the blockchain and restores the data based on at least a part of the share.
An information processing program that causes a computer to function as a node constituting a blockchain network, the node having a distribution means and a restoration means.
The distribution means is at least based on the generation of a plurality of shares constituting the data held by the node and the storage of some of the shares in the latest undetermined block in the blockchain stored in the blockchain network. Secret sharing,
The restoration means is an information processing program that acquires at least a part of the share from the blockchain and restores the data based on at least a part of the share.
A secret sharing system that has a means to share data secretly inside and outside the blockchain.
A secret sharing method that allows a computer to perform the steps of performing data secret sharing both inside and outside the blockchain.
A secret sharing program that allows a computer to function as a means of secret sharing data both inside and outside the blockchain.
An information processing system including nodes constituting the blockchain network, clients outside the blockchain network, and servers outside the blockchain network.
The node has a concealment means
The client has a requesting means
The server has a calculation means and
The concealment means encrypts a snapshot corresponding to at least one block in the blockchain stored in the blockchain network based on homomorphic encryption, and then stores the snapshot in the server.
The request means determines a request based on a transaction stored in the block in the blockchain, sends the request to the server, and receives the request.
With the reception of the request as a turning point, the calculation means performs a secret calculation based on the encrypted snapshot, determines a response corresponding to the request based on the result of the secret calculation, and obtains the response. An information processing system that returns to the client.
The information processing system according to claim 11, wherein the homomorphic encryption is a somehat homomorphic encryption.
The information processing system according to claim 11, wherein the homomorphic encryption is a level 2 homomorphic encryption.
The information processing system according to claim 11, wherein the homomorphic encryption is a completely homomorphic encryption.
The information processing system according to any one of claims 11 to 14, wherein the secret calculation is a secret search.
An information processing method in which a node constituting a blockchain network is made to execute a secret step, a client outside the blockchain network is made to execute a request step, and a server outside the blockchain network is made to execute a calculation step.
In the concealment step, a snapshot corresponding to at least one block in the blockchain stored in the blockchain network is encrypted based on homomorphic encryption, and then the snapshot is stored in the server.
The request step determines a request based on a transaction stored in the block in the blockchain and sends the request to the server.
The calculation step uses the reception of the request as a turning point to perform a secret calculation based on the encrypted snapshot, determines a response corresponding to the request based on the result of the secret calculation, and obtains the response. Information processing method to be returned to the client.
Computer,
An information processing program that functions as a node that constitutes a blockchain network and has concealment means, a client that has request means outside the blockchain network, or a server that has calculation means outside the blockchain network.
The concealment means encrypts a snapshot corresponding to at least one block in the blockchain stored in the blockchain network based on homomorphic encryption, and then stores the snapshot in the server.
The request means determines a request based on a transaction stored in the block in the blockchain, sends the request to the server, and receives the request.
With the reception of the request as a turning point, the calculation means performs a secret calculation based on the encrypted snapshot, determines a response corresponding to the request based on the result of the secret calculation, and obtains the response. An information processing program to be returned to the client.
A secret calculation system that has a means to perform secret calculation based on snapshots of at least some blocks in the blockchain.
A secret calculation method that causes a computer to perform a secret calculation step based on a snapshot of at least some blocks in a blockchain.
A secret calculation program that makes a computer act as a means of performing secret calculations based on snapshots of at least some blocks on the blockchain.