大話區塊鏈和比特幣的技術原理

{"type":"doc","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"前言：區塊鏈大熱之後，似乎淡出，但央行推出數字貨幣再次把區塊鏈推上風口浪尖。本文用大白話，簡單明瞭的講解區塊鏈和比特幣的技術原理。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"歷史"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"說到區塊鏈，不得不提一下比特幣。我們來看幾個比特幣的歷史事件："}]},{"type":"bulletedlist","content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"2008年10月，署名爲Satoshi Nakamoto（中本聰）的人發表了一篇名爲“Bitcoin: A Peer-to-Peer Electronic Cash System”的論文。論述了比特幣的技術原理，也就是區塊鏈的核心原理。這個文章大家可以在網上搜到。"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"2009年1月，中本聰發佈了比特幣軟件。他隨即創建了區塊鏈上的第一個數據塊Block，這個Block被稱作創世塊（Genesis Block）。因爲創建了這個數據塊，他獲得了50個比特幣的獎勵，這就是傳說中的挖礦賺金幣。一直沒有人知道他具體是誰。後來他就慢慢消失了，他擁有至少100萬個比特幣。退休啦！"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"發佈當天，一個名爲Hal Finney的哥們下載了比特幣軟件，中本聰轉給了它10個比特幣，這是比特幣軟件上第一筆交易。"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"2010年5月22日，名爲Hanyecz的人做了第一個現實中的比特幣交易，他用10000個比特幣買了兩個價值25美元的披薩，平均每個比特幣價值0.008美元。"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"之後比特幣價格扶搖直上，最高達到近20000多美元。"}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"比特幣現象引領了區塊鏈技術的熱潮，區塊鏈技術以中本聰的論文爲核心基礎，當然後面大家也有很多改進和創新。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"定義"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"區塊鏈是一種去中心化的數據庫，同一份數據在參與者的電腦上都複製了一份；數據一旦被寫入區塊鏈，就很難被修改；不同電腦上的數據不斷相互同步並驗證數據的有效性。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"區塊鏈沒有官方的定義，我這個定義很清晰的說明了區塊鏈技術的3個核心特徵。我們一個個來看。"}]},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"一種數據庫"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"區塊鏈是一種去中心化的數據庫，同一份數據在參與者的電腦上都有保存。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"這裏有兩個要點：它是數據庫，通俗點可以理解成賬本；它是去中心化的。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"先說去中心化，簡單說就是：這個賬本所有相關人都人手一份。沒有一箇中心人物掌握和控制這個賬本，人人平等。大家想想我們的銀行系統呢？這個賬本只有銀行有，你沒有，是中心化的。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"它是一種數據庫，什麼樣的數據庫呢？它是由數據塊Block組成的，這些數據塊前後相連，連成一個鏈，所以被稱爲區塊鏈。對於懂技術的同學，這就是一個鏈表。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/1b/1bda088f5acdb80397441f1ee5bd5511.png","alt":null,"title":null,"style":null,"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"這些塊裏面可以放任何數據。對於比特幣來說，放的就是交易信息："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"張三轉給麥叔3個比特幣"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"李四裝給麥叔4個比特幣"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"王五轉給麥叔5個比特幣"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"比特幣的第一個塊是由中本聰創建的，根據比特幣軟件的規則，因爲他成功創建了這個數據塊，系統獎勵給他50個比特幣。系統的比特幣哪裏來的？是憑空創造出來的，就像中央銀行印刷鈔票一樣。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"比特幣的參與者就是在努力的去創造數據塊，因爲創造數據塊可以獎勵比特幣。這就是挖礦。但是創造數據塊沒那麼容易，需要不停的挖呀挖呀，這個等下我會說。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"現在比特幣一共有多少個Block呢？截止到我正在碼字的這一刻，比特幣一共有553568個Block。最後這塊是一箇中國哥們挖出來的，這個數據塊裏面包含了2795筆交易數據，爲此他獲得了12.5個比特幣的獎勵。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"獎勵每4年就會減半，直到最後不再有獎勵。所以越來越難挖礦到比特幣，發財要趁早啊！比特幣最後一共有2100萬個，然後就不會再有新的比特幣了。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"比特幣的信仰者認爲比特幣最後總量是固定的，所以不會有通貨膨脹，因此具有價值。"}]},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/64/64516bc53da459eae588f7b6b249b467.jpeg","alt":null,"title":null,"style":null,"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"有興趣的同學可以在這裏查看比特幣的Block信息：https://www.blockchain.com/explorer"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"很難被修改"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"區塊鏈的數據塊，一旦被挖出來了，就很難被修改，因爲它的數據塊不是一般的數據塊，是數據塊中的戰鬥塊！來看一下結構："}]},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/96/96a4dfa60ef32c2589188d8b6733a927.jpeg","alt":null,"title":null,"style":null,"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"圖中有兩個數據塊，我用3個要點來說它是怎麼不一般："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"每個數據塊都有一個指紋（懂技術的同學，指紋就是Hash）。這個指紋是把這個塊裏面的所有數據經過一種算法轉換成的一個64位的字符串。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"一旦數據塊裏的任何數據變化了，這個64位的指紋都會發生完全的變化，這就是我說的雪崩效應。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"這個算法就是哈希算法，常用的是sha256（傻256）。我們來試驗一下："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"italic"}],"text":"數據是：中本聰轉給麥叔88個比特幣”"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"italic"}],"text":"Hash是：90621272001aed0b5f986943adc34ce2feae5d1e9ed9684f73d1ec1673de3247"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"如果聰明的我，把數據修改一下，悄悄加了1個0，Hash值將會變得完全不一樣。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"italic"}],"text":"數據是：中本聰轉給麥叔808個比特幣”"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"italic"}],"text":"Hash是：0bdaababb3efa3149f30c0f45319fcf0249f4d289d071b93e7694b5c3471a179"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"有興趣的同學可以自己網上找個在線計算器玩一下，比如這個地址：https://emn178.github.io/online-tools/sha256.html"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"後一個數據塊保存了前一個數據塊的Hash，這也就是說，如果前一個數據塊變化了，後一個數據塊保存的Hash和前一個數據塊就完全不同了。區塊鏈軟件會進行這個驗證，如果不同就說明數據是無效的。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"如果我把後一個Block修改一下，加上新的前一個塊的Hash呢？那麼根據要點1，後一個塊的Hash就又變了，造成了再後一個塊又無效了。造成多米諾骨牌式的崩塌，雪崩效應加劇了！"}]},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/f5/f5bbb30f248f18198759a8ed1cb17967.jpeg","alt":null,"title":null,"style":null,"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"每個塊的Hash必須以多個數字0開頭，加大計算Hash的難度。要點2提到修改了某Block後，就需要修改所有後續Block中的Hash。但如果計算機運算速度快，就一個個修改過去吧，計算Hash是非常快的。比特幣到現在也只有55萬個Block，找一臺怪獸機來恐怕一會就都計算好了，就成功篡改了數據。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"所以比特幣引入了要點3：不是你隨便計算出來一個Hash就可以的，你計算出來的Hash必須以若干個0開頭（假設6個0開頭）。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"Hash不是根據數據自動算出來的嗎，怎麼能隨便修改成0開頭呢？所以有了挖礦專用數字。在每個Block中添加了一個額外的數字，這個數字你可以隨便改，直到你能讓整個Block的Hash是以6個0開頭。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"所謂的挖礦就是找到這個數字，讓Hash以6個0開頭。就是我圖中下面標的綠油油的綠寶石一樣的數字。"}]},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/d4/d410d784b2034f19dffe19e8567cee6a.jpeg","alt":null,"title":null,"style":null,"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"具體幾個0呢？具體幾個是會變化的。比特幣設計的原則是整個網絡中大約每10分鐘能有1個人挖出來1個Block。如果挖的人少了，就會減少要求的0的個數，這樣就容易挖點，相當於降低要求；如果挖的人多了，就會增加難度，要求更多的0。軟件會定期自動調整要求的0個數，比特幣是每週調整一次。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"這樣綜合起來看："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"你要改一個數據，需要從新計算當前Block的Hash，爲了保證它的Hash符合0開頭的條件，你要不停計算，整個參與比特幣網絡的人要大約10分鐘才能計算出來，你自己機器肯定需要更長時間，假設10天吧；10天后你找到了，然後你又要10天的時間計算下一個數據塊的。如果你修改的Block後面有1000個Block，你需要10000天才能算完。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"10000天后，大功告成了嗎？問題是，在這10000天時間裏，整個網絡上已經又新加了大約10000x24x6個新的數據塊了。你還能跟得上嗎？"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"同步機制"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"就算你可以修改自己的那份數據，也都計算出了Hash，但你還需要和網絡上的其他參與者同步。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"同步是一個複雜的過程，但至少驗證以下幾件事情："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"是否每個Block都有符合條件的Hash，就是以多個0開頭並且確實是根據Block的數據計算出來的。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"這裏注意：計算Hash，也就是挖礦是很費時，但是驗證是否正確是非常快的！"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"是否每個Block都保存了正確的前一個Block的Hash。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"比特幣等數字貨幣還會驗證裏面的轉賬交易是否合理，比如張三要轉給我3個比特幣，但他實際上1個幣都沒有，那交易肯定不合理了。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"最後還會比較誰的有效的鏈條更長。如果出現不一致，誰的長聽誰的。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"所以我們前面討論的情況，修改數據的人幾乎永遠跟不上大部隊的長度，除非他的計算能力超過了所有其他人的總和！"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/7d/7dca4d1062f70f76fc3fad4ef4e8c8fd.jpeg","alt":null,"title":null,"style":null,"href":null,"fromPaste":true,"pastePass":true}},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"應用"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"現在比特幣的價格飛流直下，反對者認爲它的價值可能會歸零。不管比特幣如何，區塊鏈技術都是大有用武之地的，否則我也不會寫這麼長了吧。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"有人這麼說：人工智能(AI)技術是生產力的革命，而區塊鏈是生產關係的革命，因爲它去除了中心機構，從軟件底層機制上解決了人與人之間的信任關係。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"一旦理解了它的本質，就可以在很多場景上去應用它，而不僅僅是比特幣這樣的數字貨幣，比如："}]},{"type":"numberedlist","attrs":{"start":null,"normalizeStart":1},"content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":1,"align":null,"origin":null},"content":[{"type":"text","text":"產品（藥品，食物）溯源"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":2,"align":null,"origin":null},"content":[{"type":"text","text":"我們前面說的警察檔案庫"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":3,"align":null,"origin":null},"content":[{"type":"text","text":"投票系統"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":4,"align":null,"origin":null},"content":[{"type":"text","text":"供應鏈系統等"}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"就具體的應用案例，我們後面可以再細聊。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"歡迎在InfoQ平臺關注我，也可以關注我的公衆號：麥叔編程。"}]}]}