| Summary: | 碩士 === 國立臺灣大學 === 資訊工程學研究所 === 106 === By leveraging blockchain technology and smart contract concept, there is an explosive amount of applications applied to many different industries recently. Traditionally, most applications are relied on a centralized authority, which required a trusted intermediate to handle transactions and communications service. This centralized service model can encounter some security issues. With the aid of blockchain, we built a system on the basis of distributed environment, which can ensure the functionality of the original application service.
We demonstrate how to interact between blockchain and the off-chain storage with oracle-based mechanism, establishing the connection between a distributed database and the real asset. Also, we apply the concept of smart contract to our two target applications. However, because of blockchain’s nature characteristics, we may encounter some privacy issues, since the data on blockchain is expose to the public. Our proposed scheme provided a solution for the major privacy issue, which is said, achieving on-chain privacy by using homomorphic encryption on the sensitive data. Moreover, we constructed a secure comparison protocol that can check the logic function in the encrypted domain. With the aid of the proposed access control contract and the secure comparison protocol, we can carry out the protected sensitive data dependent smart contract operations and without revealing the data themselves.
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