比特幣如何達成共識
📖 6 min read
Quick Answer
Thousands of strangers who do not trust each other somehow agree on a single, shared truth about who owns what — with no referee. The mechanism that makes this possible is called Nakamoto consensus, and it is Bitcoin’s real breakthrough.
💡 Think of it as…
每個人都同意沿著最長、最堅硬的磚牆走的人群。如果兩個人同時建造新牆，人群就會等待並支持哪堵牆成長最快，而廢棄的那堵牆就會被遺忘。
The longest-chain rule
When miners find blocks at nearly the same time, the chain can briefly split. Nodes resolve this by always following the chain with the most accumulated proof-of-work (the "heaviest" chain). The other branch is orphaned.
Why honesty pays
礦工可以嘗試作弊，但這會花費大量電力，當網路拒絕他們的區塊時，他們可能會失去獎勵。激勵措施的設計是為了讓遵守規則比攻擊規則更有利可圖。
The 51% attack
如果某一方控制了網路一半以上的挖礦能力，理論上他們可以重新排序最近的交易。對於比特幣來說，這將花費數十億美元，攻擊者將摧毀他們所攻擊的東西的價值——這是一種強大的威懾力。
🔑 Key takeaway
共識=遵循最多工作量證明的鏈。作弊在理論上是可能的，但在實踐上卻代價高昂且弄巧成拙。
Why this matters for you
This is why you can accept Bitcoin from someone in another country and trust it without a bank confirming it. Consensus is the invisible trust layer behind every cross-border payment and remittance.
常見問題
有多少確認是安全的？▼
交易之上的每個新區塊都是一個「確認」。日常用量 1-3 就足夠了；對於非常大的金額，許多人會等待 6，這使得逆轉實際上是不可能的。
What is "finality" in Bitcoin?▼
比特幣具有機率終結性——交易埋藏得越深，它就越不可逆轉。經過幾個區塊後，逆轉幾乎是不可能的。
比特幣曾經遭受 51% 攻擊嗎？▼
No. Bitcoin’s mining power is so large and distributed that a sustained 51% attack has never been economically feasible.