在現在的社會裡，「旅遊」已經是人們不可或缺的一部份，若到外國旅遊，我們會先購買旅遊目的地的貨幣，當一趟旅遊結束時，會再將剩餘的貨幣賣掉，買賣的對象皆為銀行。也就是說銀行扮演一個中介的角色，能夠從中賺取匯差。但假設有一個平台，能夠直接在上面找到一位需要該貨幣的人，買賣雙方能根據某種機制得到合適的匯率，並依該匯率直接進行交換，這樣不但能以更好的匯率買到貨幣，也能省下原本應該付給銀行的手續費。然而，當去中介化後，該怎麼建立交易雙方之間的「信任」，就變成了一個很重要的問題。 而區塊鏈是一種不依賴第三方、通過自身分散式節點進行網路數據的存儲、驗證、傳遞和交流的一種技術。其具有去中心化、透明性、開放性、獨立性、安全性及匿名性…等性質。 / In current society, "travelling" is already an integral part of their life. For travelling abroad, we will purchase the currency of the tourist destination first and then sell the remaining currency after the tour: The objects of trading are all banks. That means the bank plays an intermediary role and can earn the exchange difference from this trading. However, if it is supposed that there is a platform which people could directly find a person who needs the currency, both of the buyer and seller can get an applicable exchange rate according to some reasonable mechanism, and then they can directly exchange at that exchange rate. In this case, not only the currency can be bought at a better exchange rate, but also they could save the original fee which they pay to the bank. However, it becomes a very important issue to establish the "trust" relationship during the trade. The blockchain is a kind of technologies that relies on independent nodes to store, verify, delivery and exchange network data without relying on a third party. There are the properties of decentralization, transparency, openness, independence, security, anonymity….and so on. We can use the nature of the blockchain to strengthen the trust between buyers and sellers, in order to increase the security of this platform. This study will explore the feasibility of this platform.