隨著COVID-19的爆發和肆虐，對全世界的經濟、社會、教育和各方面都帶來嚴重的負面影響。為了減緩病毒的快速傳播，不論是政府還是民間機構都致力於找尋方法，而疫情追蹤(Contact tracing)即是其中一個常用來減緩病毒傳播的方式。現今常見的疫情追蹤系統是利用手機應用程式收集使用者在地理位置上和其他應用程式使用者的接觸紀錄，並提供自行比對的功能，使得使用者可以自行評估是否需要進行自我隔離。而為了防止使用者的隱私洩漏，現存的系統將用戶的隱私資料儲存在用戶端裝置上，需要使用者自行上傳資料並比對，這將會大幅降低使用者使用時的方便性。
本研究提出結合區塊鏈技術的自動化疫情追蹤與通知系統，希望可以在保護使用者隱私的前提下，同時也能進行自動化通知。在本研究的系統中，我們運用了區塊鏈自動化、匿名性、資料透明性等特點，令使用者的隱私資料以匿名的方式儲存於區塊鏈帳本中，並利用智能合約完成區塊鏈帳本互動及伺服器的驅動，開發了保護隱私且能提供自動通知的疫情足跡追蹤系統。最後，本研究亦對所設計之系統進行了實際模擬操作和效能分析，以確保本系統實際的可用性。

As the COVID-19 pandemic has been raging since 2020, it has had serious impact on the economy, society and many aspects of the world. In order to slow down the rapid spread of the virus, governments or organizations are committed to finding solutions. Contact tracing is one of the common methods to reduce the number of confirmed cases. However, the existing contact tracing systems usually require users to upload data by themselves, and does not automatically compare contact data or send notification. This will greatly decrease the convenience for users.
This thesis proposes an automatic contact tracing and alerting system based on blockchain technology, hoping to provide automatic notification as well as protect user’s privacy. In our proposed system, we use the characteristics of blockchain such as data anonymity and data transparency. We stored users’ private data anonymously and use smart contracts to interact with blockchain ledger and server. Finally, we also did prototype implementation and performance analysis of the proposed system to ensure the actual usability of the system.

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