比特幣系統中 Simplified Payment Verification 方法之改進

自 2009 年比特幣系統問世，經歷了數年的運行，比特幣系統的可靠性與安全性已為普羅大眾所接受，也因此價值在這幾年來水漲船高。而隨著近年來移動裝置的風行，對於能夠在計算能力及儲存空間相對受限的移動裝置上運行的輕量級比特幣系統的需求也日益增加。事實上在中本聰所發表的比特幣系統論文中，就已經提出了輕量級比特幣系統的實作方法，藉由僅下載小部份區塊鏈上的資料來達成此目的。儘管此種實作方法相較於一般的比特幣系統的確能夠省下不少時間與儲存空間，但此種方法仍需要花上不少時間才能成為可使用的狀態，對於移動裝置的使用者來說無法接受。本研究的目的在於探討目前的輕量級比特幣系統中之區塊鏈同步機制，找出其中的瓶頸步驟並嘗試加以改進。

關鍵字

比特幣；區塊鏈同步；輕量級比特幣系統

並列摘要

In the past few years, Bitcoin system has proved its reliability and security as a distributed payment protocol without the need of trust and has become more and more popular. And with the rising of mobile devices nowadays, the demand of running a Bitcoin client on such space- and power-constrained devices is also increasing.ﰎ Actually, in the paper that first introduced the Bitcoin System which is published by Satoshi Nakamoto in 2008 has already described a lightweight implementation of Bitcoin clients ﲹ a Simplified Payment Verification(SPV) mode. These types of clients can operate without storing the full block chain data but only download a small part of block chain data. Although such implementation can reduce the block syncing time efficiently, it still takes quite a long time for a user to start up a wallet and synchronize with the block chain, which is intolerable for users today.ﰎ In this paper, we focus on the problem of the block syncing time of an SPV wallet, try to find out the bottleneck of its syncing mechanism and propose a few solutions to solve such problem.