比特币是第一个也是迄今受到最广泛认可的加密货币。它通过使用一个去中心化的协议、 加密算法以及一个在公共交易账本（区块链）的状态上达成全球共识的机制，实现数字领域中点对点的价值交换。
实际上，比特币是一种数字货币，它 (1) 独立于任何政府、国家或金融机构而存在；(2) 可以在全球范围内转移， 而不需要一家中心化的中介机构；并且 (3) 货币政策众所周知，不能修改。比特币即可以指比特币软件协议，也可以指货币单位，它的货币符号为 BTC。比特币于 2009 年 1 月向一个小众的技术专家小组匿名推出，如今，比特币已成为一种在全球范围内交易的金融资产， 日结算量达到数百亿美元。尽管比特币的监管状态因地区而异，而且还在持续演变，但其最常见的监管方式是作为一种货币或商品， 并且比特币的使用在所有主要经济体中都是合法的（有不同程度的限制）。
比特币的起源、早期发展和演变
比特币起源于 2008 年发布的比特币白皮书（即，《比特币：一种点对点式的电子现金系统》）中提出的理念。
白皮书中详细介绍了“允许任何两个有意愿的当事人直接进行交易，而不需要一个信任的第三方”的方法。 白皮书中部署的技术解决了“双重支付”问题，首次使数字稀缺性成为可能。
这篇论文的署名作者是中本聪，据推测是一个人或团体的笔名，他的身份至今仍是个谜。中本聪于 2009 年 1 月 9 日发布了第一个开源的比特币软件客户端，任何安装了该客户端的人都可以开始使用比特币。
比特币是在数字世界进行价值交易的一种新方法，比特币网络的最初发展主要由这种实用性驱动。早期的支持者大体上都是“密码朋克”，即主张使用强大的密码学和隐私增强技术来推动社会和政治变革的人士。然而，对比特币未来价值的猜测很快就成为使用比特币的一个重要驱动力。
在接下来的十年里，比特币的价格和用户数量呈波浪式增长。随着主要经济体的监管机构明确了比特币的合法性，大量的比特币交易所建立了与银行的关联，使得当地货币与比特币之间可以轻松兑换。随着越来越多的知名投资者表现出对比特币的兴趣，其他的一些企业也建立了强大的托管服务，使机构投资者更容易接触到这种资产。
比特币的用途是什么？
在最基本的层面上，比特币可用于在传统金融体系之外进行价值交易。例如，如果人们使用比特币进行国际支付，那么与传统的结算方式如 SWIFT 或 ACH 网络相比，比特币的结算速度更快、更安全，而且交易费用更低。
在早期阶段，网络普及度较低，比特币甚至可以用来结算小额交易，与 Visa 和 Mastercard 等支付网络（它们的结算交易速度要慢得多）形成竞争。但是，随着比特币的使用日趋广泛，扩容发行使其作为小额物品交换媒介的竞争力下降。这支持了一种说法，即比特币成为了黄金的替代品，或者说是“数字黄金”。 这里面的投资理论是，比特币的价值源自于其所融合的技术突破、供应上限（货币政策“已嵌入代码”）和强大的网络效应等综合因素。
另一种流行的说法是，比特币支持经济自由。据称，之所以能够发挥这种作用，是因为比特币在基于选择性加入的机制上提供了一种能够有效防护以下不利因素的替代货币：(1) 货币没收；(2) 审查；和 (3) 通过不加限制的通胀实现贬值。请注意，这种说法与“数字黄金”的说法并不矛盾。
比特币的基本特征：
- 去中心化：没有人可以控制或拥有比特币网络，也没有 CEO。相反，比特币网络由同意协议规则（采取开源软件客户端的形式）的自愿参与者构成。对协议的修改必须由用户达成共识，并且应该有广泛的支持者的声音，这包括“节点”、最终用户、开发人员、矿工和相关行业参与者（如交易所、钱包服务提供商和托管机构）。这使比特币成为一个准政治系统。
阅读更多：比特币治理是如何进行的？
- 分布式：所有比特币交易都记录在一个叫做区块链的公共账本上。该网络的运行依赖于人们自动存储账本的副本并运行比特币协议软件。这些“节点”通过遵循由软件定义的协议规则，为交易的正确传播做出贡献。比特币网路目前有超过 80,000 个节点分布在全球各地，这使得比特币网络几乎不可能出现停运或信息丢失的情况。
- 透明：向区块链账本添加新的交易，以及比特币网络在任何特定时间的状态（即“事实”）均按照协议规则，以透明的方式达成共识。
- 点对点：尽管节点传播了网络的状态（“事实”），但付款实际上是在个人或企业之间直接完成的。这意味着不需要任何“受信任的第三方”来充当中介。
- 无需许可：任何人都可以使用比特币，没有“守门人”，也不需要创建“比特币账户”。 任何和所有遵循协议规则的交易都会按照设定的共识机制被网络所确认。
- 伪匿名。身份信息不与比特币交易相关联，这是比特币的固有属性。相反，交易与地址相关联，地址采取随机生成的字母数字字符串的形式。
- 抗审查：由于所有遵循协议规则的比特币交易都是有效的，交易是伪匿名的，而且用户自己拥有他们所持有的比特币的“密钥”，因此监管机构很难禁止个人使用比特币或扣押他们的比特币资产。这对自由和民主有着非常重要的意义。
- 公开：所有的比特币交易都被记录下来，而且任何人都可以查看。虽然这几乎消除了欺诈的可能性，但也导致在某些情况下，通过推断将个人身份与特定的比特币地址关联在一起成为可能。
比特币的经济特征
- 固定的供应量：比特币协议中的一个关键参数是，比特币的供应量将随着时间的推移最终扩增到 2,100 万枚的总货币量。这种固定且已知的总供应量使比特币成为一种“硬资产”，这也是促使比特币被认为具有投资价值的几个特点之一。
- 抗通胀：按照内置于代码中的时间表，新的比特币被添加到流通供应量中的速度会逐渐减慢。从每个区块 50 个比特币开始（大约每 10 分钟增加一个新区块），发行速度大约每四年会减半一次。2020 年 5 月，第三次减半将发行速度从每个区块 12.5 个比特币减少到 6.25 个。此时，2,100 万个比特币中的 1,837.5 万个（占总数的 87.5%）已被“挖掘出来”。 第四次减半将发生在 2024 年，届时发行速度将减少到 3.125 个 BTC，以此类推，直到大约 2136 年，将发生最后一次减半，届时区块奖励将减少到只有 0.00000168 BTC。
- 激励驱动：有一群被称为矿工的核心参与者，受利益驱动，贡献出维护网络运行和保障网络安全所需的能量。矿工们通过一个被称为工作量证明 (PoW) 的过程，相互竞争着向构成账本（区块链）的链上添加新的区块。与 PoW 挖矿相关的硬件和能源成本以去中心化的方式以博弈论驱动的原则促进了网络安全。盈利动机被认为是赋予内生增长的重要因素。
阅读更多：什么是比特币挖矿？
是谁决定了什么是比特币？
比特币不是一个静态的协议。它可以并且已经在其整个生命周期中融合了各种变化，今后还将继续演变。尽管人们会使用一些正规化的程序来升级比特币（请参阅“比特币的治理是如何进行的？”），但比特币协议的治理最终是基于协商、劝导和自愿的。换句话说，比特币是什么由人们来共同决定。
在一些情形中，社区中曾对比特币的发展方向产生了很大的分歧。当这些分歧无法通过协商和劝导来解决时，一部分用户可能会出于他们自身的意愿，选择承认另一个不同版本的比特币。
拥有最多追随者的比特币替代版本被称为比特币现金 (BCH)。它产生于一项旨在解决交易成本上升和交易确认时间延长问题的提议。比特币现金诞生于 2017 年 8 月 1 日。
What is Bitcoin？
Bitcoin is the world’s first successful decentralized cryptocurrency and payment system, launched in 2009 by a mysterious creator known only as Satoshi Nakamoto. The word “cryptocurrency” refers to a group of digital assets where transactions are secured and verified using cryptography – a scientific practice of encoding and decoding data. Those transactions are often stored on computers distributed all over the world via a distributed ledger technology called blockchain (see below.)
Bitcoin can be divided into smaller units known as “satoshis” (up to 8 decimal places) and used for payments, but it’s also considered a store of value like gold. This is because the price of a single bitcoin has increased considerably since its inception – from less than a cent to tens of thousands of dollars. When discussed as a market asset, bitcoin is represented by the ticker symbol BTC.
The term “decentralized” is used often when discussing cryptocurrency, and simply means something that is widely distributed and has no single, centralized location or controlling authority. In the case of bitcoin, and indeed many other cryptocurrencies, the technology and infrastructure that govern the creation, supply, and security of it do not rely on centralized entities, like banks and governments, to manage it.
colorful pins on board
Instead, Bitcoin is designed in such a way that users can exchange value with one another directly through a peer-to-peer network; a type of network where all users have equal power and are connected directly to each other without a central server or intermediary company acting in the middle. This allows data to be shared and stored, or bitcoin payments to be sent and received seamlessly between parties.
The Bitcoin network (capital “B”, when referring to the network and technology, lower-case “b” when referring to the actual currency, bitcoin) is completely public, meaning anyone in the world with an internet connection and a device that can connect to it can participate without restriction. It’s also open-source, meaning anyone can view or share the source code Bitcoin was built upon.
Perhaps the easiest way to understand bitcoin is to think of it like the internet for money. The internet is purely digital, no single person owns or controls it, it’s borderless (meaning anyone with electricity and a device can connect to it), it runs 24/7, and people who use it can easily share data between one another. Now imagine if there was an ‘internet currency’ where everyone who used the internet could help to secure it, issue it and pay each other directly with it without having to involve a bank. That’s what bitcoin essentially is.
An alternative to fiat currency
Nakamoto originally designed bitcoin as an alternative to traditional money, with the goal for it to eventually become a globally accepted legal tender so people could use it to purchase goods and services.
However, bitcoin’s utility for payments has been stymied somewhat by its price volatility. Volatility is a word used to describe how much an asset’s price changes over a period of time. In the case of bitcoin, its price can change dramatically day to day – and even minute to minute – making it a less than ideal payment option. For example, you wouldn’t want to pay $3.50 for a cup of coffee and 5 minutes later it’s worth $4.30. Conversely, it doesn’t work out great for merchants either if bitcoin’s price falls dramatically after the coffee’s handed over.
In many ways, bitcoin works in the opposite way as traditional money: It is not controlled or issued by a central bank, it has a fixed supply (which means new bitcoins cannot be created at will) and it’s price is not predictable. Understanding these differences is the key to understanding bitcoin.
How does Bitcoin work?
It’s important to understand there are three separate components to Bitcoin, all of which combine together to create a decentralized payment system:
- The Bitcoin network
- The native cryptocurrency of the Bitcoin network, called bitcoin (BTC)
- The Bitcoin blockchain
Bitcoin runs on a peer-to-peer network where users — typically individuals or entities who want to exchange bitcoin with others on the network — do not require the help of intermediaries to execute and validate transactions. Users can choose to connect their computer directly to this network and download its public ledger in which all the historical bitcoin transactions are recorded.
This public ledger uses a technology known as “blockchain,” also referred to as “distributed ledger technology.” Blockchain technology is what allows cryptocurrency transactions to be verified, stored and ordered in an immutable, transparent way. Immutability and transparency are vitally important credentials for a payment system that relies on zero trust.
Whenever new transactions are confirmed and added to the ledger, the network updates every user’s copy of the ledger to reflect the latest changes. Think of it as an open Google document that updates automatically when anyone with access edits its content.
As its name implies, the Bitcoin blockchain is a digital string of chronologically ordered “blocks” — chunks of code that contain bitcoin transaction data. However, it is important to mention that validating transactions and bitcoin mining are separate processes. Mining can still occur whether transactions are added to the blockchain or not. Likewise, an explosion in Bitcoin transactions does not necessarily increase the rate at which miners find new blocks.
Irrespective of the volume of transactions waiting to be confirmed, the Bitcoin is programmed to allow new blocks to be added to the blockchain approximately once every 10 minutes.
Due to the public nature of the blockchain, all network participants can track and assess bitcoin transactions in real-time. This infrastructure reduces the possibility of an online payment issue known as double-spending. Double spending occurs when a user tries to spend the same cryptocurrency twice.
Bob, who has 1 bitcoin, might try to send it to both Rishi and Eliza at the same time and hope the system doesn’t spot it.
Double spending is prevented in the traditional banking system because reconciliation is performed by a central authority. It also isn’t a problem with physical cash because you can’t hand two people the same single dollar bill.
Bitcoin, however, has thousands of copies of the same ledger and so it requires the entire network of users to unanimously agree on the validity of each and every bitcoin transaction that takes place. This agreement between all parties is what’s known as “consensus.”
Just as banks constantly update the balances of their users, everyone that has a copy of the Bitcoin ledger is responsible for confirming and updating the balances of all bitcoin holders. So, the question is: How does the Bitcoin network ensure that consensus is achieved, even though there are countless copies of the public ledger stored all over the world? This is done through a process known as “proof-of-work.”
What is proof-of-work?
Computers in the Bitcoin network use a process called proof-of-work (PoW) to validate transactions and secure the network. Proof-of-work is the Bitcoin blockchain’s “consensus mechanism.”
While Proof-of-Work was the first and is generally the most common type of consensus mechanism for cryptocurrencies that run on blockchains, there are others — most notably proof-of-stake (PoS), which tends to consume less overall computing power (and therefore less energy).
Proof-of-work elevates certain network contributors to the role of “validators” – more commonly known as “miners” – only after they have proven their commitment to the network by dedicating an immense amount of computing power to discovering new blocks — a process that typically takes approximately 10 minutes.
mining farm
When a new block is discovered, the successful miner who found it through the mining process gets to fill it with 1 megabyte’s worth of validated transactions. This new block is then added to the chain and everyone’s copy of the ledger is updated to reflect the new data. In exchange for their efforts, the miner is allowed to keep any fees attached to the transactions they add, plus they’re given an amount of newly minted bitcoin. The new bitcoin created and handed to successful miners is known as a “block reward.”
All Bitcoin users have to pay a network fee each time they send a transaction (usually based on the size of it) before the payment can be queued for validation. Think of it like buying a stamp to post a letter.
The goal when adding a transaction fee is to match or exceed the average fee paid by other network participants so your transaction is processed in a timely manner. Miners have to cover their own electricity and maintenance costs when running their machines all day to validate the bitcoin network, so they prioritize transactions with the highest fees attached to make the most money possible when filling new blocks.
You can view the average fees on the Bitcoin mempool, which can be likened to a waiting room where unconfirmed transactions are held until they are selected and added to the blockchain by miners.
Read more: How Bitcoin Mining Works
How is bitcoin created?
The Bitcoin network automatically releases newly minted bitcoin to miners when they find and add new blocks to the blockchain. The total supply of bitcoin has a cap of 21 million coins, meaning once the number of coins in circulation reaches 21 million, the protocol will stop minting new coins. In a way, Bitcoin mining doubles as both the transaction validation and the bitcoin issuance process (until all the coins are mined, then it will only function as the transaction validation process.)
Importantly, increasing the amount of computing power dedicated to bitcoin mining will not mean more bitcoins are mined. Miners with more computing power only increase their chances of being rewarded with the next block, so the amount of bitcoin mined remains relatively stable over time.
The Bitcoin network uses a coin distribution strategy known as “bitcoin halving” that ensures the amount of bitcoin distributed to miners reduces over time. By gradually decreasing the supply of new bitcoin entering circulation, the idea is it will help support the asset’s price (based on the fundamental principles of supply and demand.)
A bitcoin halving (sometimes called a “halvenings”) happens every 210,000 blocks or roughly four years. When the bitcoin protocol first launched in 2009, each successful miner received 50 bitcoin (BTC) as a block reward. Fast forward to 2021: Block rewards are now 6.25 BTC, a reduction from 12.5 BTC prior to the bitcoin halving in May 2020.
The next halving is expected to take place sometime in 2024 and will see block rewards drop again, to 3.125 BTC. This process will continue until eventually there are no more coins left to be mined.
Today, there are over 18.7 million BTC in circulation meaning there are just 2.25 million BTC left to enter circulation. However, taking into consideration the halving principle and other network factors like mining difficulty, it’s estimated the last bitcoin will be mined sometime around the year 2140.
What is a bitcoin wallet?
A bitcoin wallet is a software program that runs on a computer or a dedicated device that provides the functionality required to secure, send and receive bitcoin. Counterintuitively, the bitcoin itself is not stored in a wallet. Instead, the wallet secures the cryptographic keys — essentially a very specialized type of password — that proves the ownership of a specific amount of bitcoin on the Bitcoin network.
Anytime a bitcoin transaction is executed, ownership of the bitcoin transfers from the sender to the recipient, with the network designating the recipient’s keys as the new “password” for accessing the bitcoin.
Bitcoin uses a system called public-key cryptography (PKC) to preserve the integrity of its blockchain. Originally used to encrypt and decrypt messages, PKC is now commonly used on blockchains to secure transactions. This system allows only individuals with the right set of keys to access specific coins.
There are two types of keys required to own and execute bitcoin transactions: A private key and a public key. Both keys are strings of randomly generated alphanumeric characters used to encrypt and decrypt transactions. On the bitcoin network, PKC implements one-way mathematical functions that are easy to solve in one way and almost impossible to reverse.
The blockchain uses the one-way mathematical algorithm to create a public key from the private key. With this, it is practically impossible to regenerate the private key from the public key, meaning you’d better not lose your keys (or forget your password to access them). Also, you will receive a public address, which is simply the hashed or shorter form of your public key.
This address functions similarly to a house address and is shared to receive bitcoin. On the other hand, the private key must be kept hidden from prying eyes, just as your debit card’s PIN is meant for your eyes alone.
To execute transactions, you are required to use your private key and public key to encrypt and sign your Bitcoin transactions. Also, you have to include the public address of the recipient. With this, only the recipient with the right private key can unlock or claim the transferred bitcoin.
一般情况下认为，比特币的私钥有多少比特？(POAP 在正确选项中)
- 256 (Correct && Over)