“Data Registration Method, Data Decryption Method, Data Structure, Computer, and Program” in Patent Application Approval Process (USPTO 20210192059)

2021 JUL 14 (NewsRx) -- By a News Reporter-Staff News Editor at Information Technology Business Daily -- A patent application by the inventors Fujimura, Shigeru (Yokosuka-shi, Kanagawa-ken, JP); Nakadaira, Atsushi (Yokosuka-shi, Kanagawa-ken, JP); Ohashi, Shigenori (Yokosuka-shi, Kanagawa-ken, JP); Sakuma, Satoshi (Yokosuka-shi, Kanagawa-ken, JP); Watanabe, Hiroki (Yokosuka-shi, Kanagawa-ken, JP), filed on June 27, 2018, was made available online on June 24, 2021, according to news reporting originating from Washington, D.C., by NewsRx correspondents.

This patent application has not been assigned to a company or institution.

The following quote was obtained by the news editors from the background information supplied by the inventors: “Through the years, a mechanism that ensures the reliability without requiring centralized management has been getting popular, in particular, in a field of bitcoin which is cryptocurrency. This mechanism called blockchain ensures the reliability of exchanged information through a consensus building process within a distributed network. Its soundness is maintained by preventing frauds, such as tampering or double-spending, in the entire system. In this blockchain, cryptocurrency transaction information (transaction) between participants is organized into a unit called “block”, and blocks are linked in the form of a chain and managed in chronological order. A new block is approved through a consensus algorithm such as Proof of Work in a distributed network. This means that the currency transaction recorded inside a block has been consented in the entire system. The ledger of a series of transaction information pieces managed using this blockchain is called the “distributed ledger”. Nodes participating in a network have the same distributed ledger.

“Nowadays, blockchain platform technologies are also developed in which advanced script code is registered in the distributed ledger in addition to currency transactions and in which the execution and results of the script code are also subjected to consensus. For example, in a blockchain platform typified by Ethereum or Hyperledger Fabric, script code is executed using each transaction as input, the execution result is stored in a key-value store, a representative value of the store at the time is also recorded in the block in the distributed ledger (for example, non-patent document 1). In cryptocurrency described above, the content of a transaction is limited to a currency transaction record such as “who passed how much to whom”. In contrast, in these succeeding blockchain technologies, the user himself/herself can programmably set information to be recorded by using a transaction and script code. This makes it easy to apply blockchain to various applications other than currency transactions, such as securities exchange, insurance business, and copyright management. These platform technologies are called smart contract blockchain because a contract is subjected to consensus among participants.”

In addition to the background information obtained for this patent application, NewsRx journalists also obtained the inventors’ summary information for this patent application: “SUMMARY:

“Problem to be Solved by the Invention

“The above blockchain systems are based on the assumption that information is disclosed among all the nodes. However, there are cases, depending on the application, where it is desirable to conceal some areas of transactions and disclose the concealed areas only to participants involved. For example, according to the method disclosed in patent document 1, which is applied to the license management of contents, encrypted information can be communicated via a blockchain of a cryptocurrency type. In this method, target data to be encrypted is a common key for a content, and concealed information is exchanged only between the terminals of two parties, a right holder and a user. However, in this method, it is impossible to select an area to be concealed.

“For the case where the user can programmably set the items of a contract as in smart contract blockchains, it is desired that concealment can be designed more flexibly. For example, in a case where a smart contract blockchain is applied to transactions of cargo insurance policies in trade business, it is desired that items to be concealed can be set flexibly among multiple items and that the disclosure range can be set to a combination of multiple different organizations such an insurance company, an advising bank, and an issuing bank. In this case, management information is complex such as which items are encrypted in the contract data having multiple items, to which users the information is disclosed, and which keys need to be used for the decryption. Further, key exchange procedures necessary for obtaining common keys and management of public keys and secret keys are complex, which imposes a heavy burden in operation on the users when they use the system.

“To address these problems, it is conceivable to have a centralized concealment server outside the blockchain system as in non-patent document 2. The concealment server stores management information for concealment and provides functions of encryption and decryption in response to requests from the users. Concealed information is included into the contract data, which is stored in the distributed ledger in the blockchain system. The concealment server manages encryption items and disclosure ranges. This reduces the burden on the users. However, in non-patent document 2, the advantages of distributed authority, which is a feature of the blockchain system, are impaired. For example, it is difficult to prevent internal frauds such as a case where the administrator of the concealment server abuses his/her authority and peeks at confidential information stored by another company. In addition, in a case where the administrator of the concealment server stops the service, it is not easy to decrypt encrypted data registered in the distributed ledger only with the users’ authority. In addition, since keys are exchanged outside the blockchain system, no evidence of who passed a key to whom remains, which can impair the reliability of transaction evidence.

“An objective of the present invention made in light of these points is to provide a data registration method, data decryption method, data structure, computer, and program capable of managing data registered in a distributed ledger with part of the data flexibly concealed without a centralized concealment server and without bothering the users with complicated procedures or key management.

“Means for Solving the Problem

“To solve the above problems, a data registration method in a computer, according to the present embodiment, includes: generating a common key for encrypting and decrypting an item included in data that is registered in a distributed ledger; acquiring a public key for each account of a user having access authority to the item; encrypting the common key with the public key for each account; and registering the common key encrypted for each account in the distributed ledger via a transaction.

“To solve the above problems, a data decryption method in a computer, according to the present embodiment, includes: acquiring data that is registered in a distributed ledger via a transaction and includes an encrypted item; acquiring concealment management information registered in the distributed ledger, via a transaction; acquiring the encrypted item and an encrypted common key for decrypting the encrypted item, from the concealment management information; decrypting the encrypted common key using a secret key corresponding to the common key; and decrypting the encrypted item using the decrypted common key.

“To solve the above problems, a data structure for concealment management information, according to the present embodiment, includes: account information on a user having access authority to an encrypted item of data registered in a distributed ledger via a transaction; information indicating the encrypted item; information on a public key for encrypting a common key for decrypting the encrypted item; and the common key encrypted with the public key. The account information identifies which user the concealment management information corresponds to. The common key is decrypted using a secret key corresponding to the public key. The decrypted common key is used for decrypting the encrypted item.

“To solve the above problems, a computer according to the present embodiment includes a processor that performs: generating a common key for encrypting and decrypting an item included in data that is registered in a distributed ledger; acquiring a public key for each account of a user having access authority to the item; encrypting the common key with the public key for each account; and registering the common key encrypted for each account in the distributed ledger via a transaction.

“To solve the above problems, a program according to the present embodiment causes a computer to perform generating a common key for encrypting and decrypting an item included in data that is registered in a distributed ledger; acquiring a public key for each account of a user having access authority to the item; encrypting the common key with the public key for each account; and registering the common key encrypted for each account in the distributed ledger via a transaction.

“Effect of the Invention

“The data registration method, data decryption method, data structure, computer, and program according to the present invention makes it possible to manage data registered in distributed ledgers with part of the data flexibly concealed without a centralized concealment server and without bothering the users with complicated procedures or the key management.”

The claims supplied by the inventors are:

“1. A data registration method performed by a computer, comprising: generating a common key for encrypting and decrypting an item included in data that is registered in a distributed ledger; acquiring a public key for each account of a user having access authority to the item; encrypting the common key with the public key for each account; and registering the common key encrypted for each account in the distributed ledger via a transaction.

“2. The data registration method according to claim 1, further comprising: encrypting an item that is included in the data and corresponds to the common key, using the common key; and registering data including the encrypted item in the distributed ledger via a transaction.

“3. The data registration method according to claim 1, wherein the common key is generated for each item to be encrypted included in the data.

“4. The data registration method according to claim 1, wherein in the generating of the common key, the common key is generated at each reception of a request for registering the data in the distributed ledger.

“5. A data decryption method performed by a computer, comprising: acquiring data that is registered in a distributed ledger via a transaction and includes an encrypted item; acquiring concealment management information registered in the distributed ledger via a transaction; acquiring the encrypted item and an encrypted common key for decrypting the encrypted item, from the concealment management information; decrypting the encrypted common key using a secret key corresponding to the common key; and decrypting the encrypted item using the decrypted common key.

“6. A data structure for concealment management information, comprising: account information on a user having access authority to an encrypted item of data registered in a distributed ledger via a transaction; information indicating the encrypted item; information on a public key for encrypting a common key for decrypting the encrypted item; and the common key encrypted with the public key, wherein the account information identifies which user the concealment management information corresponds to, the common key is decrypted using a secret key corresponding to the public key, and the decrypted common key is used for decrypting the encrypted item.

“7. A computer including a processor that performs: generating a common key for encrypting and decrypting an item included in data that is registered in a distributed ledger; acquiring a public key for each account of a user having access authority to the item; encrypting the common key with the public key for each account; and registering the common key encrypted for each account in the distributed ledger via a transaction.

“8. A computer readable storage medium storing a program that causes a computer to execute a process comprising: generating a common key for encrypting and decrypting an item included in data that is registered in a distributed ledger; acquiring a public key for each account of a user having access authority to the item; encrypting the common key with the public key for each account; and registering the common key encrypted for each account in the distributed ledger via a transaction.”

URL and more information on this patent application, see: Fujimura, Shigeru; Nakadaira, Atsushi; Ohashi, Shigenori; Sakuma, Satoshi; Watanabe, Hiroki. Data Registration Method, Data Decryption Method, Data Structure, Computer, and Program. Filed June 27, 2018 and posted June 24, 2021. Patent URL: https://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PG01&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.html&r=1&f=G&l=50&s1=%2220210192059%22.PGNR.&OS=DN/20210192059&RS=DN/20210192059

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