Artwork trading method, computer, and program

Abstract

To make it possible to trade artwork securely using a smart contract.SOLUTION: An artwork trading method is executed by a computer. The computer receives a request to acquire an exhibited artwork from an external device and issues a transaction including information regarding the request for acquisition of the exhibited artwork and information regarding the exhibit of the artwork for which the acquisition is requested to a contract account in a block chain network in response to the receipt of the request to acquire the exhibited artwork.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to a method and device for trading artwork, and a program. [Background technology]

[0002] In recent years, various services have been created using smart contracts that use blockchain to guarantee the validity of contracts. For example, Patent Literature 1 discloses the use of smart contracts for money lending by banks. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2019-524018 Summary of the Invention [Problem to be solved by the invention]

[0004] However, with conventional smart contracts, it was difficult to securely trade artworks such as digital paintings drawn on tablet devices. Specifically, it was not possible to guarantee that the seller of the artwork was the artist himself, or that the artwork had not been tampered with by anyone after it was put up for sale. In addition, if the artwork was illegally leaked after it was sold, it was not possible to identify the buyer from whom it was leaked.

[0005] Therefore, one object of the present invention is to provide an artwork trading method, trading device, and program that can securely trade artwork using smart contracts. [Means for solving the problem]

[0006] The method for trading artwork according to the present invention is a method for trading artwork executed by a computer, characterized in that it includes a first receiving step in which the computer receives the artwork and biometric signature data, and an listing transaction issuing step in which the computer issues an listing transaction including information identifying the artwork and the biometric signature data to a contract account in a blockchain network.

[0007] The artwork trading device according to the present invention is characterized in that it includes a receiving unit that receives artwork and biometric signature data, and a first transaction issuing unit that issues an auction transaction including information identifying the artwork and the biometric signature data to a contract account in a blockchain network.

[0008] The artwork program of the present invention is a program for causing a computer to function as an artwork trading device, and is a program for causing the computer to execute a first receiving step of receiving the artwork and biometric signature data, and an listing transaction issuing step of issuing an listing transaction including information identifying the artwork and the biometric signature data to a contract account in a blockchain network. Effect of the Invention

[0009] The present invention allows artwork to be traded securely using smart contracts. [Brief description of the drawings]

[0010] [Figure 1] 1 is a diagram showing a configuration of an artwork trading system 1 according to an embodiment of the present invention. [Diagram 2]2 is a diagram showing an example of the hardware configuration of a platform portal server 10, an artist terminal 40, and a purchaser terminal 41. FIG. [Diagram 3] FIG. 2 is a diagram showing a configuration of biometric signature data. [Figure 4] FIG. 4 is a diagram illustrating pen angle data. [Diagram 5] FIG. 2 is a diagram showing input and output of data to and from the platform portal server 10. [Figure 6] FIG. 2 is a functional block diagram of the platform portal server 10 for exhibiting artwork. [Figure 7] FIG. 2 is a functional block diagram of a platform portal server 10 for selling artworks. [Figure 8] 2 is a process flow diagram showing the process executed by the platform portal server 10. FIG. [Figure 9] FIG. 10 is a diagram showing details of the artwork submission process executed in step S5 of FIG. 8. [Figure 10] FIG. 9 is a diagram showing details of the artwork sales process executed in step S6 of FIG. 8. [Figure 11] FIG. 9 is a diagram showing details of the artwork sales process executed in step S6 of FIG. 8. [Figure 12] FIG. 11 is a diagram showing details of the QR code (registered trademark) embedding process executed in step S41 of FIG. [Figure 13] FIG. 13 is a process flow diagram showing a process for reading a QR code from a watermarked artwork generated by the QR code embedding process shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

[0012] 1 is a diagram showing the configuration of an artwork trading system 1 according to the present embodiment. As shown in the figure, the artwork trading system 1 has a configuration in which a platform portal server 10, an artist terminal 40, a purchaser terminal 41, a blockchain network 50, a distributed file system 51, and a catalog database 52 are interconnected via a network 2. In addition, a secure key store 53 is connected to the platform portal server 10.

[0013] 2 is a diagram showing an example of the hardware configuration of the platform portal server 10, the artist terminal 40, and the purchaser terminal 41. Each of the platform portal server 10, the artist terminal 40, and the purchaser terminal 41 can be configured by a computer 100 having the configuration shown in the figure.

[0014] As shown in FIG. 2, the computer 100 includes a CPU (Central Processing Unit) 101, a storage device 102, an input device 103, an output device 104, and a communication device 105.

[0015] The CPU 101 is a device that controls each part of the computer 100 and reads and executes various programs stored in the storage device 102. Each process described later with reference to Figs. 6 to 13 is realized by the CPU 101 of the platform portal server 10 executing the programs stored in the storage device 102.

[0016] The storage device 102 includes a primary storage device such as a dynamic random access memory (DRAM) and an auxiliary storage device such as a hard disk, and serves to store the operating system of the computer 100, various programs for executing various applications, and data used by these programs.

[0017] The input device 103 is a device that receives input operations from a user and supplies them to the CPU 101, and is configured to include, for example, a keyboard, a mouse, and a touch detection device. Among these, the touch detection device is a device that includes a touch sensor and a touch controller, and is used to detect pen input or touch input.

[0018] The output device 104 is a device that outputs the processing results of the CPU 101 to the user, and is configured to include, for example, a display and a speaker. The communication device 105 is a device for communicating with external devices, and transmits and receives data according to instructions from the CPU 101. Data transmission and reception between the platform portal server 10, the artist terminal 40, and the purchaser terminal 41 is realized by the communication devices 105 communicating with each other.

[0019] Returning to Fig. 1, the artist terminal 40 is a computer used by an artist to input and submit artwork, as well as to input biometric signature data, which will be described later. The artwork and biometric signature data are both digital data, and are generated by the artist using a pen P to input data to the input device 103 of the artist terminal 40. The specific process for submitting artwork will be described later.

[0020] Fig. 3 is a diagram showing the structure of biometric signature data. The biometric signature data is data generated according to, for example, WILL (Wacom Ink Layer Language) or FSS (Forensic Signature Stream), and as shown in the figure, includes dynamic signature data, a hash value of a signed document, context information, additional information, the dynamic signature data, the hash value of a signed document, a hash value of the context information, this hash value and this hash value of the additional information, and a checksum for detecting errors that may occur when this hash value is transmitted or received.

[0021] The dynamic signature data is digital ink data including a series of coordinate data constituting a line drawing. Each coordinate data is data indicating the position of the pen P detected by the touch detection device described above. To explain this detection in detail, the touch sensor includes a plurality of X electrodes each extending in the Y direction and arranged at equal intervals in the X direction, and a plurality of Y electrodes each extending in the X direction and arranged at equal intervals in the Y direction. When the pen P is configured to be able to transmit a signal, the touch controller receives a burst signal transmitted by the pen P at each of the plurality of X electrodes and the plurality of Y electrodes, thereby obtaining coordinate data indicating the position of the pen P. On the other hand, when the pen P cannot transmit a signal, the touch controller sequentially transmits a signal to each of the plurality of X electrodes, receives the signal at each of the plurality of Y electrodes, and obtains coordinate data indicating the position of the pen P by detecting a change in the amplitude of the received signal. The touch controller is configured to collect the coordinate data at a frequency of, for example, 100 or 200 times per second.

[0022] The dynamic signature data may include, in addition to the coordinate data, a writing pressure value and pen angle data. The writing pressure value is the pressure applied to the tip of the pen P, which is detected by a built-in sensor of the pen P and is supplied from the pen P to the touch sensor.

[0023] 4 is a diagram illustrating the pen angle data. The pen angle data is data detected by a built-in sensor or a touch sensor of the pen P, and includes an azimuth angle θ, a tilt angle φ, and a rotation angle ψ shown in the figure.

[0024] Returning to Figure 3, the hash value of the signed document is the hash value of the electronic data of the document (exhibition application, contract, etc.) that the artist signed to generate the biometric signature data. Note that the hash value is a value obtained by inputting the target electronic data into a specified one-way hash function. This also applies to the other hash values ​​described below.

[0025] The context information includes the name data of the artist who signed, the date and time of signature, the purpose of the signature, information on the touch detection device used for signing (manufacturer name, model name, etc.), information on the application used for signing (application name, version information, etc.), information on the operating system of the artist terminal 40 (operating system name, version information, etc.), address information of the artist terminal 40 (IP address, MAC address, etc.), etc. The additional information is information that can be arbitrarily specified by the administrator of the artwork trading system 1 in addition to the dynamic signature data, the hash value of the signed document, and the context information.

[0026] Returning to Fig. 1, the purchaser terminal 41 is a computer used by a purchaser to purchase artwork (artwork put up for sale by an artist). Specific processing for this purchase will be described later.

[0027] The blockchain network 50 is a network of multiple computers connected in a peer-to-peer manner and configured to record smart contract transactions on a blockchain. As a specific example, the blockchain network 50 is the Ethereum network. Recording of transactions on the blockchain is performed by several computers (hereinafter referred to as "miners") connected to the blockchain network 50.

[0028] Specifically, each block constituting the blockchain includes a block header and data (transaction data) indicating the specific contents of a transaction. The block header includes a Merkle root, which is data obtained by compressing the size of the transaction data, a hash value of the previous block, and a nonce value, which is an arbitrary character string. In the blockchain network 50, a rule is established that in order to connect a new block to the blockchain, the hash value of the block must satisfy a certain condition (for example, the condition that the value starts with "000"). Therefore, a miner who wishes to record a block in the blockchain performs an operation (mining) of brute-forcely finding a nonce value so that the hash value of the block header of the block satisfies the above-mentioned predetermined condition. As a result of this operation, the miner who succeeds in finding the nonce value first connects the block to the blockchain, thereby completing the recording of the transaction in the blockchain.

[0029] The distributed file system 51 is a network of multiple computers connected peer-to-peer, and is configured to store any electronic data. As a specific example, the distributed file system 51 is IPFS (InterPlanetary File System). Electronic data stored in the distributed file system 51 is identified by its hash value. That is, in the distributed file system 51, the hash value of the stored electronic data functions as address information of the electronic data. In this embodiment, the distributed file system 51 is used to store encrypted artwork.

[0030] The catalog database 52 is a database implemented on one or more computers. In this embodiment, it is used to store a catalog of artworks (information required for sales). The catalog database 52 may be implemented in the platform portal server 10.

[0031] The secure key store 53 is a database for storing encryption keys used for encrypting data, and is set in advance to only accept access from the platform portal server 10. In this embodiment, the secure key store 53 is used to store public keys 1 and 2, private keys 1 and 2, and data encryption keys 1 and 2, which will be described later.

[0032] The platform portal server 10 is a computer that functions as an artwork trading device, and plays a role in accepting artworks submitted by artists and in enabling the purchase of the submitted artworks.

[0033] FIG. 5 is a diagram showing data input and output to and from the platform portal server 10. First, in the stage of accepting the listing of an artwork, the platform portal server 10 accepts the listing of the artwork from the artist terminal 40. This listing includes the artwork itself (for example, digital image data in a raster format such as a JPEG file, or digital image data in a vector format such as a digital ink file) and sales conditions (paid / free, price in the case of a paid item, etc.). The price is preferably indicated by a virtual currency (such as Ether) realized by the blockchain network 50. The platform portal server 10 also accepts input of the biometric signature data described above from the artist terminal 40. Having received the listing and biometric signature data, the platform portal server 10 records a transaction (listing transaction) indicating the listing in the blockchain network 50. The specific contents of the listing transaction will be described later.

[0034] The platform portal server 10, which has accepted the submission of an artwork, encrypts the artwork body with a data encryption key 1 equivalent to the common key in a common key cryptosystem, and stores the artwork body in a distributed file system 51. The platform portal server 10 also generates a pair of a public key 1 and a private key 1 equivalent to the public key and private key in a public key cryptosystem, and encrypts the data encryption key 1 with the public key 1. The pair of the public key 1 and the private key 1 and the encrypted data encryption key 1 are then stored in a secure key store 53. The reason why the artwork body is encrypted with the data encryption key 1 rather than the public key 1 is that large-sized data such as artwork cannot be encrypted with a public key in a public key cryptosystem.

[0035] The platform portal server 10 further registers the thumbnail of the put up artwork, the sales conditions, and the ID (identification information) of the selling transaction recorded in the blockchain network 50 in the catalog database 52, and returns the ID of the selling transaction and the private key 1 to the artist terminal 40. The returned ID of the selling transaction is used by the artist to refer to the blockchain network 50 and confirm the contents of his / her own listing. In addition, the private key 1 is used by the artist to retrieve his / her own artwork from the distributed file system 51.

[0036] Next, at the stage of realizing the purchase of the exhibited artwork, the platform portal server 10 accepts a purchase application from the purchaser terminal 41. This purchase application includes purchaser information (such as an account and name on the blockchain network 50) indicating the purchaser, information indicating the artwork selected by the purchaser, and payment (for example, information indicating an arbitrary amount of virtual currency). Having accepted the purchase application, the platform portal server 10 records a transaction indicating the purchase (purchase transaction) in the blockchain network 50. The specific contents of the purchase transaction will be described later.

[0037] The platform portal server 10, which has accepted the purchase application, extracts the private key 1 and the data encryption key 1 from the secure key store 53, and also extracts the artwork from the distributed file system 51. Then, the platform portal server 10 decrypts the data encryption key 1 with the private key 1, and decrypts the artwork with the decrypted data encryption key 1.

[0038] The platform portal server 10 further embeds a watermark in the decrypted artwork to generate watermarked artwork, encrypts it with a data encryption key 2, and stores it in the distributed file system 51. As will be described in detail later, this watermark is generated based on the ID (identification information) of the purchase transaction.

[0039] The platform portal server 10 also generates a pair of public key 2 and private key 2, which correspond to the public key and private key in the public key cryptography, and encrypts the data encryption key 2 with the public key 2. Then, the pair of public key 2 and private key 2 and the encrypted data encryption key 2 are stored in the secure key store 53. Note that the reason why the watermarked artwork is encrypted with the data encryption key 2 rather than the public key 2 is that the size of the watermarked artwork is large, just like when it is put up for sale.

[0040] Thereafter, the platform portal server 10 performs a process of returning the purchase transaction ID, the private key 2, and the hash value of the encrypted watermarked artwork to the purchaser terminal 41, and also performs a process of transmitting the purchase transaction ID and the proceeds to the artist terminal 40. The purchase transaction ID returned to each terminal is used by the purchaser and artist to refer to the blockchain network 50 and confirm the purchase details. In addition, the private key 2 and the hash value of the encrypted watermarked artwork are used to retrieve the artwork purchased by the purchaser from the distributed file system 51 and decrypt it.

[0041] Figures 6 and 7 are functional block diagrams of the platform portal server 10. Figure 6 shows functional blocks of the platform portal server 10 related to the listing of artwork, and Figure 7 shows functional blocks of the platform portal server 10 related to the sale of artwork. Below, the functional blocks of the platform portal server 10 will be described in detail with reference to these figures.

[0042] Referring first to Figure 6, the platform portal server 10 is configured to have, as functional blocks related to the listing of artwork, a receiving unit 11, a duplicate determination unit 12, an artwork encryption processing unit 13, an artwork storage processing unit 14, a key pair generation unit 15, a transaction issuing unit 16, a key encryption processing unit 17, a catalog generation unit 18, and a transmitting unit 19.

[0043] The receiving unit 11 receives an artwork listing from the artist terminal 40. As described above, this listing includes the artwork itself and information indicating the sales conditions.

[0044] The duplication determination unit 12 determines whether the submitted artwork is a duplicate of another artwork (i.e., whether the submitted artwork is not unique). This determination may be performed, for example, by comparing the submitted artwork with artworks previously stored in the distributed file system 51 by the platform portal server 10, or by comparing with images obtained by searching on the Internet, or by both. If the comparison results in no other artwork that overlaps with the submitted artwork, the duplication determination unit 12 determines that there is no duplication, and causes the receiving unit 11 to further receive the above-mentioned biometric signature data from the artist terminal 40. On the other hand, if another artwork that overlaps with the submitted artwork is found, the duplication determination unit 12 determines that there is a duplication, and returns to the artist terminal 40 that the submitted artwork cannot be submitted.

[0045] The artwork encryption processing unit 13 encrypts the artwork when the duplication determination unit 12 determines that there is no duplication. More specifically, the artwork encryption processing unit 13 first generates a data encryption key 1 that corresponds to a common key in a common key cryptosystem. Then, the generated data encryption key 1 is used to encrypt the artwork.

[0046] The artwork storage processing unit 14 stores the artwork encrypted by the artwork encryption processing unit 13 in the distributed file system 51, and also obtains the hash value.

[0047] The key pair generation unit 15 generates a pair of a public key 1 and a private key 1, which correspond to a public key and a private key in a public key cryptosystem.

[0048] The transaction issuing unit 16 generates an auction transaction including the hash value of the encrypted artwork acquired by the artwork storage processing unit 14, the biometric signature data received by the receiving unit 11, and the public key 1 generated by the key pair generating unit 15, and issues the transaction to a contract account (described later) of the blockchain network 50. After this, any of the miners connected to the blockchain network 50 completes recording of the auction transaction in the blockchain.

[0049] The key encryption processing unit 17 encrypts the data encryption key 1 using the public key 1 generated by the key pair generation unit 15, and stores the data encryption key 1, together with the pair of public key 1 and private key 1, in the secure key store 53 in association with the ID of the listing transaction issued by the transaction issuing unit 16.

[0050] The catalog generation unit 18 generates thumbnails of the put-up artworks and registers them together with the sales conditions and the ID of the putting-up transaction in the catalog database 52. By registering the put-up artworks in the catalog database 52 in this manner, a purchaser can refer to the catalog database 52 and select the artwork he or she wishes to purchase.

[0051] The transmitter 19 returns the listing transaction ID issued by the transaction issuer 16 and the private key 1 generated by the key pair generator 15 to the artist terminal 40. This enables the artist to confirm the listing transaction on the blockchain network 50, and also enables the artist to confirm the original artwork by retrieving and decrypting the encrypted artwork stored in the distributed file system 51.

[0052] The artist's confirmation of the original artwork will be described in more detail. The artist uses the artist terminal 40 to transmit the listing transaction ID and the private key 1 to the platform portal server 10. The platform portal server 10 obtains a hash value of the encrypted artwork by referring to the blockchain network 33 based on the listing transaction ID received from the artist terminal 40. Then, the platform portal server 10 accesses the distributed file system 51 using the obtained hash value and reads the encrypted artwork. The platform portal server 10 also reads the encrypted data encryption key 1 from the secure key store 53 based on the listing transaction ID received from the artist terminal 40, and decrypts it with the private key 1 received from the artist terminal 40. Finally, the platform portal server 10 obtains the artwork by decrypting the encrypted artwork using the decrypted data encryption key 1, and returns it to the artist terminal 40. In this way, the artist can confirm the artwork.

[0053] Next, referring to Figure 7, the platform portal server 10 is configured to have functional blocks related to the sale of artwork, including a receiving unit 20, a purchase eligibility determination unit 21, a key decryption processing unit 22, an artwork decryption processing unit 23, a key pair generation unit 24, a transaction issuance unit 25, a watermark generation unit 26, a watermark embedding processing unit 27, an artwork encryption processing unit 28, an artwork storage processing unit 29, a key encryption processing unit 30, and a transmitting unit 31.

[0054] The receiving unit 11 receives a purchase offer indicating an intention to purchase an artwork from the purchaser terminal 41. As described above, this purchase offer includes the purchaser information, information indicating the artwork selected by the purchaser, and the price.

[0055] The purchase permission determination unit 21 determines whether the purchase offer is successful. More specifically, the purchase permission determination unit 21 first reads out the sales conditions of the corresponding artwork and the ID of the auction transaction from the catalog database 52. Then, the purchase permission determination unit 21 compares the read out sales conditions with the contents of the purchase offer and determines whether the purchase offer is successful based on the result. For example, if the sales conditions stipulate that the price of the artwork is 1 Ether, then if the purchase offer includes 1 Ether, the purchase permission determination unit 21 determines that the purchase offer is successful. On the other hand, if the purchase offer does not include 1 Ether, the purchase permission determination unit 21 determines that the purchase offer is not successful. In the latter case, the purchase permission determination unit 21 returns a notice of purchase denial to the purchaser terminal 41.

[0056] Based on the ID of the auction transaction, the key decryption processing unit 22 reads out the private key 1 and the encrypted data encryption key 1 from the secure key store 53. Then, the key decryption processing unit 22 uses the read out private key 1 to decrypt the read out encrypted data encryption key 1.

[0057] The artwork decryption processing unit 23 acquires a hash value of the encrypted artwork by referring to the blockchain network 50 based on the ID of the listing transaction. Then, based on the acquired hash value, the encrypted artwork is read from the distributed file system 51 and decrypted using the data encryption key 1 decrypted by the key decryption processing unit 22.

[0058] The key pair generating unit 24 generates a pair of a public key 2 and a private key 2, which correspond to a public key and a private key in a public key cryptosystem.

[0059] The transaction issuing unit 25 generates a purchase transaction including the purchaser information included in the purchase offer, the listing transaction ID read by the purchase availability determination unit 21 from the catalog database 52, the amount indicating the purchase price of the artwork, and the public key 2 generated by the key pair generation unit 24, and issues the transaction to a contract account (described later) on the blockchain network 50. After this, any of the miners connected to the blockchain network 50 completes recording of the purchase transaction on the blockchain.

[0060] The watermark generation unit 26 generates a watermark based on the purchase transaction ID issued by the transaction issuer 25. The watermark thus generated is, for example, a QR code (registered trademark) indicating the purchase transaction ID. The watermark embedding processor 27 embeds a watermark in the artwork decoded by the artwork decoding processor 23, thereby generating watermarked artwork. The details of this process will be described later in detail with reference to FIG. 12.

[0061] The artwork encryption processing unit 28 generates a data encryption key 2 that corresponds to a common key in the common key cryptosystem, and encrypts the watermarked artwork using the generated data encryption key 2. The artwork storage processing unit 29 stores the watermarked artwork encrypted by the artwork encryption processing unit 28 in the distributed file system 51, and also acquires its hash value.

[0062] The key encryption processing unit 30 encrypts the data encryption key 2 using the public key 2 generated by the key pair generation unit 24, associates it with the purchase transaction ID issued by the transaction issuing unit 25, and stores it in the secure key store 53.

[0063] The transmission unit 31 returns the purchase transaction ID, the hash value acquired by the artwork storage processing unit 29, and the private key 2 generated by the key pair generation unit 24 to the purchaser terminal 41, and also transmits the purchase transaction ID and the proceeds of the sale to the artist terminal 40. This enables the purchaser and artist to confirm the purchase transaction on the blockchain network 50. In addition, the purchaser can obtain the purchased artwork in a watermarked state by acquiring and decrypting the encrypted watermarked artwork stored in the distributed file system 51.

[0064] The acquisition of the artwork by the purchaser will be described in more detail. The purchaser uses the purchaser terminal 41 to transmit the hash value of the encrypted watermarked artwork, the ID of the purchase transaction, and the private key 2 to the platform portal server 10. The platform portal server 10 accesses the distributed file system 51 using the hash value received from the purchaser terminal 41 and reads out the encrypted watermarked artwork. The platform portal server 10 also reads out the encrypted data encryption key 2 from the secure key store 53 based on the ID of the purchase transaction received from the purchaser terminal 41, and decrypts it with the private key 2 received from the purchaser terminal 41. Finally, the platform portal server 10 obtains the watermarked artwork by decrypting the encrypted watermarked artwork using the decrypted data encryption key 2, and returns it to the purchaser terminal 41. In this way, the purchaser can obtain the watermarked artwork.

[0065] 8 to 12 are process flow diagrams showing the processes executed by the platform portal server 10. Below, the processes executed by the platform portal server 10 will be explained in more detail with reference to these drawings.

[0066] 8, the platform portal server 10 first performs a process of generating an account (contract account) on the blockchain network 50 so that the listing and purchase of artwork can be recorded on the blockchain network 50. Specifically, the platform portal server 10 transmits a transaction including a contract code to the blockchain network 50 (step S1), and obtains the address of the contract account generated as a result (step S2).

[0067] Thereafter, the platform portal server 10 repeatedly executes a process of determining whether or not an artwork listing has been received from the artist terminal 40 (step S3) and a process of determining whether or not an artwork purchase request has been received from the purchaser terminal 41 (step S4).

[0068] If it is determined in step S3 that an artwork listing has been received, the platform portal server 10 executes an artwork listing process (step S5). If it is determined in step S4 that an artwork purchase request has been received, the platform portal server 10 executes an artwork sales process (step S6).

[0069] Fig. 9 is a diagram showing details of the artwork listing process executed in step S5 of Fig. 8. As shown in the figure, the platform portal server 10, which has started the artwork listing process, acquires the artwork listing including the artwork itself and the sales conditions (step S11). Then, the uploaded artwork is compared with known artworks (step S12). The details of this comparison are as described above.

[0070] Based on the result of the comparison performed in step S12, the platform portal server 10 judges whether the artwork is unique or not (step S13). As a result, if it is judged not to be unique, the platform portal server 10 returns a notice to the artist terminal 40 that the artwork cannot be exhibited, and ends the artwork exhibiting process (step S14). On the other hand, if it is judged to be unique, the platform portal server 10 receives biometric signature data from the artist terminal 40 (step S15). In a specific example, a screen prompting the artist to sign is displayed on the display of the artist terminal 40, and the artist is prompted to input the dynamic signature data described above. The artist terminal 40 generates biometric signature data by adding each piece of information described with reference to FIG. 3 to the dynamic signature data thus input, and transmits the biometric signature data to the platform portal server 10.

[0071] Next, the platform portal server 10 generates a pair of public key 1 and private key 1 (step S16), and also generates data encryption key 1 and encrypts it using public key 1 (step S17).

[0072] Next, the platform portal server 10 encrypts the artwork using the data encryption key 1 (step S18), and stores the encrypted artwork in the distributed file system 51 (step S19). After that, the platform portal server 10 issues a listing transaction including the hash value of the encrypted artwork, the biometric signature data, and the public key 1 to the contract account generated in steps S1 and S2 of Fig. 8 (step S20).

[0073] After executing step S20, the platform portal server 10 stores the pair of public key 1 and private key 1 and the data encryption key 1 encrypted in step S17 in the secure key store 53 in association with the ID of the issued listing transaction (step S21).Then, the platform portal server 10 returns the listing transaction ID and private key 1 to the artist terminal 40 (step S22), and registers the artwork thumbnail, sales conditions, and listing transaction ID in association with each other in the catalog database 52 (step S23), and ends the artwork listing process.

[0074] Figures 10 and 11 are diagrams showing details of the artwork sales process executed in step S6 in Figure 8. As shown in these figures, the platform portal server 10, which has started the artwork sales process, acquires a purchase offer including the artwork selection result in the catalog database 52, purchaser information, and price (step S30). Then, it reads the sales conditions and the listing transaction ID from the catalog database 52 (step S31), and judges whether the purchase offer is successful or not (step S32). The details of this judgment are as described above.

[0075] If it is determined in step S32 that the purchase has not been completed, the platform portal server 10 returns a message indicating that the purchase is not possible to the purchaser terminal 41, and ends the artwork sales process (step S33). On the other hand, if it is determined that the purchase has been completed, the platform portal server 10 first reads out the private key 1 and the encrypted data encryption key 1 from the secure key store 53 based on the ID of the listing transaction (step S34), and uses the read out private key 1 to decrypt the read out encrypted data encryption key 1 (step S35).

[0076] Next, the platform portal server 10 acquires a hash value of the encrypted artwork by referring to the listing transaction in the blockchain network 50 (step S34). Then, based on the acquired hash value, the encrypted artwork is read from the distributed file system 51 and decrypted by the data encryption 1 acquired in step S35 (step S37).

[0077] Next, the platform portal server 10 reads the encrypted data encryption key 1 from the secure key store 53 based on the storage location obtained in step S34, and decrypts it with the private key 1 obtained in step S5 (step S36). Also, the platform portal server 10 reads the encrypted artwork from the distributed file system 51 based on the hash value obtained in step S34, and decrypts it with the data encryption key 1 obtained in step S36 (step S37).

[0078] Next, the platform portal server 10 generates a pair of public key 2 and private key 2 (step S38), and issues a purchase transaction including the purchaser information, the selling transaction ID, the amount, and the public key 2 to the contract account generated in steps S1 and S2 of FIG.

[0079] Next, the platform portal server 10 generates a QR code (registered trademark) from the ID of the purchase transaction (step S40), and executes a QR code (registered trademark) embedding process for embedding the generated QR code (registered trademark) in the artwork (step S41).

[0080] Fig. 12 is a diagram showing details of the QR code (registered trademark) embedding process executed in step S41 of Fig. 10. Note that, although the diagram shows an example of an approach using singular value decomposition (SVD: Singular Value Decomposition) (SVD Based Approach), the QR code (registered trademark) embedding process may be performed using other approaches. Examples of such approaches include an approach using discrete cosine transform (DCT: Discrete Cosine Transform) (Optimal DCT-Psychovisual Threshold), an approach using encoding in the YCbCr color space (YCbCr Colour Space Encoding Approach), and an approach using multi-resolution analysis (Multi-resolution Wavelet Decomposition).

[0081] As shown in FIG. 12, the platform portal server 10 first generates an n×n-bit QR code W=(w1, w2, . . . , w n×n ) is obtained (step S50). n×n Each of these has a value of either 0 or 1.

[0082] Next, the platform portal server 10 acquires a predetermined robustness factor σ (step S51). The robustness factor σ is a value that increases the restorability of the embedded QR code (registered trademark) as it increases, but also decreases the image quality of the watermarked artwork as it increases. Therefore, it is preferable to determine an optimal σ value in advance, taking into consideration the restorability of the QR code (registered trademark) and the image quality of the watermarked artwork.

[0083] Next, the platform portal server 10 separates the m×m-bit artwork into three images I1, I2, and I3 by color channel (e.g., red, green, and blue in the RGB color model) (step S52). Then, the image with the highest entropy (i.e., the most homogeneous and least variable image) is selected from the images I1, I2, and I3 (step S53). Here, the explanation will be continued assuming that image I1 has the highest entropy and is therefore selected in step S53.

[0084] Having selected the image I1, the platform portal server 10 divides the image I1 into non-overlapping blocks B(j) of 4×4 bits each (step S54), where 1≦j≦(m / 4)×(m / 4).

[0085] Next, the platform portal server 10 generates a sequence of n×n pseudorandom numbers P=(p1, p2, . . . , p n×n ) is generated (step S55). k ≦(m / 4)×(m / 4).Then, the platform portal server 10 executes the processes of steps S57 to S60 for each integer k that is equal to or greater than 1 and equal to or less than n×n (step S56).

[0086] To explain the process of steps S57 to S60 in detail, the platform portal server 10 first k The th block B(p k ) (step S57). Next, the platform portal server 10 selects the selected block B(p k ) is obtained by singular value decomposition of the 4×4 diagonal matrix S(p k )=diag(s1,s2,s3,s4) is obtained (step S58). k )=U(p k )S(p k )V(p k ) Twhere U(p k ) and V(p k ) are each 4×4 unitary matrices.

[0087] And the robustness factor σ and the bit w k Using this diagonal matrix S(p k ) to obtain the 4×4 diagonal matrix S'(p k ) = diag(s1,s2+σ×w k , s2, s3 × 0.1) is derived (step S59). k ) to perform the inverse process of singular value decomposition to obtain WB(p k ) is generated (step S60). k )=U(p k )S'(p k )V(p k ) T By calculating WB(p k )

[0088] After all the processes of steps S57 to S60 are completed, the platform portal server 10 generates an image I1' (step S61) using the generated n×n WB(j) and the (m / 4)×(m / 4)-n×n blocks B(j) that were not selected in step S57. Specifically, of the (m / 4)×(m / 4) blocks B(j) that constitute the image I1, n×n blocks B(p1) to B(p n×n ) are WB(p1)~WB(p n×n ) to generate image I1'.

[0089] Finally, the platform portal server 10 generates the watermarked artwork using the image I1' and the images I2 and I3 (step S62). Specifically, the watermarked artwork is generated by synthesizing the images I1', I2, and I3.

[0090] Returning to Fig. 10, after completing the QR code (registered trademark) embedding process, the platform portal server 10 generates a data encryption key 2 and encrypts it using the public key 2 (step S42). Then, as shown in Fig. 11, the pair of the public key 2 and the private key 2 and the encrypted data encryption key 2 are stored in the secure key store 53 in association with the ID of the purchase transaction (step S43).

[0091] Next, the platform portal server 10 encrypts the watermarked artwork using the data encryption key 2 (step S44), and stores the encrypted watermarked artwork in the distributed file system 51 (step S45). Thereafter, the platform portal server 10 returns the hash value of the encrypted watermarked artwork, the purchase transaction ID, and the private key 2 to the purchaser terminal 41 (step S46), and also returns the purchase transaction ID and the sales amount to the artist terminal 40 (step S47), completing the artwork sales process.

[0092] Here, the QR code (registered trademark) read process for reading a QR code (registered trademark) from watermarked artwork will be described with reference to Fig. 13. Fig. 13 shows the process for reading a QR code (registered trademark) from watermarked artwork generated by the QR code (registered trademark) embedding process shown in Fig. 12, but it goes without saying that when the watermarked artwork is generated by another type of QR code (registered trademark) read process, a read process corresponding to that process is required. In addition, the following description will be given assuming that the platform portal server 10 performs the QR code (registered trademark) read process, but the QR code (registered trademark) read process may be performed by another computer.

[0093] First, the platform portal server 10 acquires a predetermined robustness factor σ (step S71). This robustness factor σ is preferably the same value as the robustness factor σ acquired in step S51 of FIG.

[0094] Next, the platform portal server 10 separates the m×m-bit watermarked artwork into three images I1, I2, and I3 for each color channel (step S71). Then, the image with the highest entropy is selected from the images I1, I2, and I3 (step S72). The processes of steps S71 and S72 are the same as those of steps S52 and S53 in Fig. 12. Here again, it is assumed that image I1 has the highest entropy and is selected in step S72.

[0095] The platform portal server 10, which has selected the image I1, divides the image I1 into non-overlapping blocks B(j) of 4×4 bits each (step S73), where 1≦j≦(m / 4)×(m / 4). This process is also the same as step S54 in FIG.

[0096] Next, the platform portal server 10 generates a sequence of n×n pseudorandom numbers P=(p1, p2, . . . , p n×n ) is generated (step S74). k ≦(m / 4)×(m / 4). The predetermined seed used in step S74 must be the same as the seed used in step S55 of Fig. 12. The QR Code cannot be read without knowing the seed, so the seed also functions as a kind of common key.

[0097] Next, the platform portal server 10 executes the processes of steps S76 to S79 ​​for each integer k that is equal to or greater than 1 and equal to or less than n×n (step S75).

[0098] To explain the process of steps S76 to S79 ​​in detail, the platform portal server 10 first k The th block B(p k ) (step S76). Next, the platform portal server 10 selects the selected block B(p k ) is obtained by singular value decomposition of the 4×4 diagonal matrix S'(p k)=diag(s1,s2',s3',s4') is obtained (step S77). This singular value decomposition is similar to step S58 in FIG. k )=U(p k )S'(p k )V(p k ) T It is expressed by:

[0099] Next, the platform portal server 10 derives s2'-s3' (step S78). The value thus derived is the diagonal matrix S'(p k ) is derived, σ×w k Therefore, the platform portal server 10 determines whether the derived value is equal to or greater than σ / 2 (σ×w k ≧σ / 2) if w k Set 1 to w otherwise k (step S79). k is read out.

[0100] When all the processes in steps S76 to S79 ​​are completed, the platform portal server 10 reads out n×n w k Based on this, we create an n × n bit QR code W = (w1, w2, . . . , w n×n ) is obtained (step S80). This completes the reading of the QR code (registered trademark) W.

[0101] As described above, according to the artwork trading system 1 of this embodiment, biometric signature data including the artist's signature is recorded in the blockchain network 50 as part of the listing transaction, so that it is possible to confirm at a later date that the seller of the artwork is the artist himself. In addition, since the artwork is stored in the distributed file system 51 in an encrypted state, it is possible to guarantee that the artwork has not been tampered with by anyone after listing. Furthermore, since a QR code (registered trademark) indicating the ID of the purchase transaction is embedded in the sold artwork, if the artwork after sale is illegally leaked, it is possible to identify the purchaser who leaked the artwork by reading the QR code (registered trademark) from the leaked artwork. Therefore, according to the artwork trading system 1 of this embodiment, it can be said that it is possible to trade artwork securely using a smart contract.

[0102] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and it goes without saying that the present invention can be embodied in various forms without departing from the spirit of the present invention.

[0103] For example, in the above embodiment, the watermark to be embedded in the artwork to be sold is generated based on the ID of the purchase transaction, but the watermark may be generated based on other information. As a specific example, the watermark generating unit 26 may generate a watermark that is a QR code (registered trademark) or other bitmap representation based on data acquired by the artist terminal 40 when the artist draws a digital image as the artwork. Here, the above-mentioned "data acquired by the artist terminal 40 when drawing the digital image" is, for example, data included in a digital ink file generated according to the above-mentioned WILL. Specific examples of such data include, for example, one or more stroke data constituting a digital image or a part thereof, and identification information of the artist terminal 40 used to generate the artwork. The watermark generating unit 26 may derive a hash value (fingerprint of "data acquired by the artist terminal 40 when drawing the digital image") by substituting the "data acquired by the artist terminal 40 when drawing the digital image" into a predetermined hash function, and generate a watermark based on the derived hash value. [Explanation of symbols]

[0104] 1. Artwork Trading System 2 Network 10 Platform Portal Server 11,20 Receiving section 12 Duplication determination section 13,28 Artwork encryption processing section 14,29 Artwork storage processing unit 15,24 Key pair generation unit 16,25 Transaction issuing department 17,30 Key encryption processing unit 18 Catalog Generation Department 19,31 Transmitter 21 Purchase Eligibility Determination Department 22 Key decryption processing unit 23 Artwork Decoding Processing Unit 26 Watermark Generation Unit 27 Watermark embedding processing section 40 Artist terminals 41 Purchaser terminal 50 Blockchain Networks 51 Distributed File System 52 Catalog Database 53 Secure Key Store 100 Computers 101 CPU 102 Storage device 103 Input Device 104 Output Device 105 Communication equipment

Claims

1. 1. A computer-implemented method for trading artwork, comprising: The computer, receiving a request from an external device to acquire the submitted artwork; In response to receiving the request to acquire the exhibited artwork, issue a transaction to a contract account in a blockchain network, the transaction including information regarding the request to acquire the exhibited artwork and information regarding the exhibited artwork requested to be acquired; embedding a watermark in the requested artwork indicating the transaction; 13. A method for trading artwork, comprising:

2. The watermark is a QR code.

2. The method for trading artwork according to claim 1.

3. the computer encrypts the artwork with the embedded watermark using a data encryption key; 2. The method for trading artwork according to claim 1.

4. The computer, Generate a public / private key pair, encrypting said data encryption key with said public key; 4. The method for trading artwork according to claim 3.

5. the computer transmitting information identifying the encrypted and watermarked artwork to the external device; 4. The method for trading artwork according to claim 3.

6. the computer transmitting the private key and information identifying the encrypted and watermarked artwork to the external device; 5. The method for trading artwork according to claim 4.

7. a receiving unit for receiving a request for acquiring the submitted artwork from an external device; A processor that, in response to receiving a request to acquire the exhibited artwork, issues a transaction to a contract account in a blockchain network, the transaction including information regarding the request to acquire the exhibited artwork and information regarding the exhibit of the artwork requested to be acquired, and further embeds a watermark indicating the transaction in the artwork requested to be acquired; A computer comprising:

8. The watermark is a QR code.

8. The computer of claim 7.

9. the processor encrypts the artwork with the embedded watermark using a data encryption key; 8. The computer of claim 7.

10. The processor, Generate a public / private key pair, encrypting said data encryption key with said public key; 10. The computer of claim 9.

11. a transmitting unit for transmitting information identifying the encrypted artwork having the embedded watermark to the external device; 10. The computer of claim 9.

12. a transmitting unit configured to transmit the private key and information identifying the encrypted artwork having the watermark embedded therein to the external device; 11. The computer of claim 10.

13. receiving a request from an external device to acquire the submitted artwork; In response to receiving the request to acquire the exhibited artwork, issue a transaction to a contract account in a blockchain network, the transaction including information regarding the request to acquire the exhibited artwork and information regarding the exhibited artwork, and further embed a watermark indicating the transaction in the exhibited artwork. A program that causes a computer to execute a process.

14. The watermark is a QR code. The program according to claim 13.

15. encrypting the artwork with the embedded watermark using a data encryption key; The program according to claim 13, further causing the computer to execute a process.

16. Generate a public / private key pair, encrypting said data encryption key with said public key; The program according to claim 15, further causing the computer to execute a process.

17. transmitting information identifying the encrypted and watermarked artwork to the external device; The program according to claim 15, further causing the computer to execute a process.

18. transmitting the private key and information identifying the encrypted and watermarked artwork to the external device; The program according to claim 16, further causing the computer to execute a process.

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