基於理想格的全同態加密技術運用於以太坊區塊鏈上之可行性探討

Abstract

因為不用第三方的操作與控制，區塊鏈提供了一個非常值得信賴的環境供使用者在上面執行程式。也因此，許多的相關應用應運而生，舉凡電子投票系統、拍賣系統、互聯網等等。然而，區塊鏈「透明化」的性質使得使用者們可以查看到所有放置在區塊鏈上的資料，這也導致了隱私問題。這個問題的存在，也使得目前眾多包含了隱私資訊的應用受到了極大的阻礙。 此篇論文中，我們提供了一個結合了區塊鏈與全同態加密技術的系統，讓我們可以在享有區塊鏈好處的同時，也透過全同態加密保障了隱私安全。藉由我們這個系統，使用者可以輕鬆的強化所寫的智能合約上的隱私保護。使用者透過鏈下加密後，上鏈時只要呼叫全同態加密的函數，便可以在加密空間下進行運算，並通過所有區塊鏈結點的驗證來保障安全性。 最後，我們也設計了維克里拍賣在我們的系統上，通過實際的運作來強調出此系統的優勢與弱點。

Without the requirement of trusted third-parties, Blockchain guarantees an environment which can be trusted to everyone. However, the transparency property caused a hazard to real-world application that every on-chain information can be viewed by every user. That is to say, the application which contains sensitive data and personal information which require privacy protection cannot be implemented into Blockchain. We propose Fully Homomorphic Encryption scheme into Blockchain, combining the trusty and privacy protection, build up a new framework to obtain both of the advantages and make the Blockchain applications easier to enforce privacy protection based on our system. Our framework’s programmer can encrypt the private data off-chain by FHE scheme, sequentially, they can call FHE function to compute their data after their smart contracts deploy to Blockchain. To present the advantages and the weakness of our framework, we then design a Vickrey Auction System using our FHE-based system to make the bidding price in secret while output the winner and his/her required payment.