一種基於Oracle的鏈上隱私保護機制及其應用

Abstract

近幾年各式各樣不同的產業正在利用區塊鏈技術和智能合約的概念大量的研發新的應用。傳統上，大多數的應用都依賴於一個中央管理機構，換句話說，需要一個可以信任的第三方來處理和管理交易和通訊服務。然而這種集中式管理模式會遇到一些安全問題。有了區塊鏈的技術，我們在分佈式的環境基礎上構建了一個系統，並且一樣擁有原來中央管理模式應用服務的功能。 我們演示了如何使用Oracle讓區塊鏈和鏈外的儲存資料庫可以進行溝通和交互，建立利用區塊鏈來當平台的分佈式資料庫和真正實體資產的連接。此外，我們將智能合約的概念應用於我們兩個目標的應用程序。然而，由於區塊鏈本質上的特性，也就是資料公開性，我們會遇到一些隱私的問題。當使用區塊鏈同時又必須在鏈上保有隱私，我們提出使用同態加密的方法來達到鏈上隱私保護來保護重要的資料。另外，我們建構了一個安全的比較協議，可以檢查加密域中的邏輯功能。利用提出的訪問控制合約和安全比較協議，我們可以執行擁有重要資料的合約相關的操作，並且不會洩漏重要的資料。

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.