Abstract: A method for providing oracle service of a blockchain network by using zero-knowledge proof includes steps of: (a) in response to feeder terminals registering data feeder transactions, including commitments generated with a commitment key and off-chain data, encrypted data generated by encrypting the off-chain data with a public key and data validation values proving with feeder zero-knowledge proof keys that the commitments are identical to the off-chain data, onto the blockchain network, the aggregator terminal acquiring at least one data feeder transaction therefrom; (b) the aggregator terminal verifying data validation values with its corresponding feeder zero-knowledge proof key, decrypting encrypted data with a private key, generating on-chain data from the decrypted data using a calculator and calculation validation values proving with an aggregator zero-knowledge proof key that the on-chain data is generated from the decrypted data, and registering the on-chain data and the calculation validation valu

Abstract: A tampering verification system and method for financial institution certificates are based on blockchain and verify whether one of the financial institution certificates has been tampered with by comparing the contents of the financial institution certificate at the point of first being generated by a financial institution and at the point of client issue.

Abstract: The present invention provides a certificate issuing system based on a block chain, the system having a means for directly generating a certificate-specific public key and a certificate-specific private key in a user terminal operated by a user, guiding the certificate-specific public key and the certificate-specific private key so as to be generated in a state in which a network in the user terminal is blocked, and eliminating the costs incurred for constructing, operating, and maintaining the certificate issuing system having a high-grade security system linked therewith so as to block hacking, which occurred in the past, as much as possible, since the certificate-specific public key requiring maintenance is stored and managed in an electronic wallet, installed in servers that hold block chains, through a peer-to-peer network (P2P)-based distributed database, not by a server run by a certificate authority (CA).

Abstract: A method of a payment for an Internet of Things (IoT) device is provided. The method includes steps of: a payment supporting server (a) on condition that the payment supporting server has registered certificates of the IoT device, a service providing device, and a digital wallet in a first blockchain, manages their transaction IDs, has registered a representative hash value in a second blockchain, manages their transaction IDs, and manages link information between the IoT device and the digital wallet, confirming validity of a billing transaction, and (b) acquiring identification information on the digital wallet; and (c) paying the billing detail using the digital wallet, registering its payment result in the first blockchain, registering in the second blockchain, if one anchoring condition is satisfied, a first representative hash value, and transmitting the payment result to the service providing device, the IoT device, and the digital wallet.

Abstract: The present invention provides a method for issuing an electronic voucher, the method comprising: (a) a step in which a server checks whether or not (i) electronic voucher data, (ii) a public key of a specific issuer and (iii) a signature value of the specific issuer are valid; and (b) a step in which, if the validity check result is positive, the server registers or supports the registration of a function value associated with (i) the electronic voucher data, (ii) the public key of the specific issuer and (iii) the signature value of the specific issuer in a blockchain network, and acquires or supports the acquisition of Txid indicating information on the location of the function value, registered in the blockchain network.

Abstract: A method for providing a user identity based on zero-knowledge proof over a blockchain network by using a user certificate is provided. The method includes steps of: an address abstraction smart contract (a) instructing the user terminal which made a user identity generating request to generate the user identity corresponding to the user certificate issued from a certification authority and generate a user identity proof by using user identity verifying parameters, the user identity, the user certificate and a certification authority public key, to thereby prove that the user identity is generated from the user certificate issued by the certification authority; and (b) upon receiving a user identity registering request from the user terminal, (i) verifying the user identity proof by using the user identity verifying parameters, the user identity, the certification authority public key and the user identity proof and (ii) registering the user identity upon successful verification.