OurChain上的跨鏈議題

Abstract

OurChain是少數能提供全局事件順序與決定性最終性來達到分散式同步的區塊鏈。跨鏈是指區塊鏈之間的互通，尤其是不同鏈上的價值流通。然而，無論是不是相同的鏈，每一個鏈都是獨立運作的，鏈與鏈之間無法簡單轉移價值。主要原因為區塊鏈目前只提供鏈內的信任，並不提供鏈與鏈之間的信任。也就是說，跨鏈是指提供一種信任機制讓區塊鏈之間能互通，使得鏈內物件所代表的資訊和價值能夠轉移到另一個鏈上正常運作，其中最關鍵的技術是以分散式同步來取得彼此資訊和價值的信任。本篇論文探討進行跨鏈時所面臨到的問題，如跨鏈雙方如何達成共識和最終性、驗證交易、確保交易的原子性、改善系統的安全性和效能等。本論文更利用 OurChain 的分散式同步特性改善現有的跨鏈技術，如使用 Oracle 機制的安全性問題、簡易支付驗證證明（Simple Payment Verification proof, SPV proof）模型的分叉問題、和原子交換智能合約(Atomic Swap Contract)的效能問題等。此外，錢包是區塊鏈的入口點，也最容易表現跨鏈的特色。本論文也設計一套去中心化的跨鏈錢包系統，除了圖形化表現鏈間的資料同步與操作，也提供簡易地鏈間價值流通時複雜的匯率查詢功能。並且以外匯市場和全球化貿易系統為例，探討如何將本論文落實於日常生活中。

OurChain is one of the few blockchains providing global event ordering and deterministic finality to achieve distributed synchronization. Cross chain addresses the communication among blockchains, especially, the value transfer between different blockchains. No matter the communicating blockchains are the same or not, each blockchain runs independently. It is not simple to transfer value among blockchains. The main reason is the blockchain technology only provided trust within the blockchain, not among blockchains. In other words, cross chain technology needs to provide a trust mechanism for blockchain communication, so that the information and value of objects in the blockchain can be transferred to another blockchain and function correctly. Distributed synchronization is the most critical technology for this mutual trust of information and value. This thesis will discuss the cross chain issues, such as how to reach consensus and finality, how to verify the transactions, how to ensure transaction atomicity, and how to improve the security and performance. This thesis also addresses the distributed synchronization feature of OurChain to improve the cross chain technologies, e.g. the security issues of using the Oracle mechanism, the fork problem of using simple payment verification proof (SPV proof) model, and the performance of using atomic swap contract. Moreover, electronic wallet is the entry point of blockchain systems. This thesis also designs a decentralized electronic wallet for cross chain systems. In addition to present the data synchronization and operation among blockchains graphically, the wallet provides simple search function for complex value transfer rates cross chain. Furthermore, this thesis takes the foreign exchange market and the global trading system as examples to explore how to realize this thesis in daily life.