比特币白皮书 学习(2)：简介篇

本文是比特币白皮书正文的第一部分——简介。

简介内容

Introduction
Commerce on the Internet has come to rely almost exclusively on financial institutions serving as trusted third parties to process electornic payments. While the system works well enough for most transactions, it still suffers from the inherent weaknesses of the trust based model. Completely non-reversible transactions are not really possible, since financial institutions cannot avoid mediating disputes. The cost of mediation increase transaction costs, limiting the minimum practical transaction size and cutting off the possibility for small casual transactions, and there is a broader cost in the loss ability to make non-reversible payments for non-reversible services. With the possibility of reversal, the need for trust spreads. Merchants must be wary of their customers, hassling them for more information than they would otherwise need. A certain percentage of fraud is accepted as unavoidable. These costs and payment uncetainties can be avoided in person by using physical currency, but no mechanism exists to make payments over a communications channel without a trusted party.

What is needed is an electronic payment system based on cryptographic proof instead of trust, allowing any two willing parties to transact directly with each other without the need for a trusted third party. Transactions that are computationally impratical to reverse would protect sellers from fraud, we propose a solution to the double-spending problem using a peer-to-peer distributed timestamp sever to generate computational proof of the chronological order of transactions. The system is secure as long as honest nodes collectively control more CPU power than any cooperating group of attacker nodes.

简介翻译

简介
在网络上，商家处理电子支付，几乎都需要依靠作为可信任的第三方的金融机构。虽然这类系统在绝大多数情况下运转良好，但是它仍然遭受了来自“基于信任模型”的固有缺陷的风险。我们无法完全实现不可逆的交易，因为金融机构总是不可避免地会出面协调争端。调解纠纷的成本增加了交易的成本，限制了最小实际交易的规模，切断了偶然交易的可能性，而且，潜在的损失还在于，很多商品和服务本身是无法退货的。有了潜在退款的可能性，就需要交易双方拥有信任。商家必须提防自己的顾客，因此会向客户索取完全不必要的个人信息。一定比例的欺诈行为被认为是不可避免的。这些成本和支付的不确定性在人们使用物理货币时可以避免，因为此时没有第三方信用中介的存在。

我们需要的是基于密码学原理而不是信任的电子系统，它使得任意两个自由的双方能够直接交易而不需要可信任的第三方。在计算上不可逆的交易将保护卖方免受欺诈，并且例行托管机制将很容易地保护买方。在本文中，我们提出一种解决双重支付问题的方案，使用点对点的分布式时间戳服务来生成交易的时间顺序的计算证明。这个系统是安全的，只要诚实的节点比合作的攻击者节点集合更能够集中控制CPU的能力。

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