As blockchain-based applications and research such as cryptocurrency increase, an oracle problem to bring external data in the blockchain is emerging. Among the methods to solve the oracle problem, a method of configuring oracle based on TLS, an existing internet infrastructure, has been proposed. However, these methods currently have the disadvantage of not supporting privacy protection for external data, and there are limitations in configuring the process of a smart contract based on external data verification for automation. To solve this problem, we propose a framework consisting of middleware of external source server, data prover, and verification contract. The framework converts the data signed in the web server into a proof that the owner can prove with zk-SNARKs and provides a smart contract that can verify this. Through these procedures, data owners not only protect their privacy by proving themselves, but they can also automate on-chain processing through smart contract verification. For the proposed framework, we create a proof using libsnark for server data and show the performance and cost to verify with Solidity the smart contract language of the Ethereum platform.

Anonymity forms the basis of decentralized ecosystems, leading to an increase in criminal activities such as money laundering and illegal currency trading. Especially in blockchain-based metaverse services, activities such as preventing sexual crimes and verifying the identity of adults are becoming essential. Therefore, avatar authentication and the KYC (Know Your Customer) process have become crucial elements. This paper proposes a mechanism to achieve the KYC process by verifying user identity using smart contracts. Users obtain an SBT (Soul Bound Token) from the metaverse service provider through the DID (Decentralized Identity) credential issued during the KYC process. The identity verification of avatars occurs within smart contracts, ensuring user privacy and protection through ZKP (Zero Knowledge Proof). Tools for generating ZKP are also provided, enabling users, even those who are unfamiliar with ZKP, to use them conveniently. Additionally, an integrated wallet is offered to seamlessly manage DID credentials and SBTs. Furthermore, in case of avatar identity issues, users can request an audit by the issuer through the associated DID tokens.