原始文献 / 邮件 / Bitcoin P2P e-cash paper
Bitcoin P2P e-cash paper
Cryptography Mailing List · 2008-11-03 16:23:49 UTC
> 只要诚实节点控制着网络上最多的 CPU 算力，
> 它们就能生成最长链，并超过任何攻击者。
但事实并非如此。坏人通常控制着拥有10万台甚至更多机器的僵尸网络。我认识的运行垃圾邮件僵尸黑名单的人告诉我，他们经常每天看到上百万新增僵尸机。
这也是 hashcash 在当今互联网上无法奏效的原因——好人拥有的计算火力远少于坏人。
感谢您提出这一点。
我本可以将那个陈述说得更严谨些。要求是：好人一方合计拥有的 CPU 算力超过任何单个攻击者。
存在许多不足以压倒网络的小型僵尸网络，它们仍可通过生成比特币赚钱。这些小型网络就成了"诚实节点"。（我需要一个比"诚实"更好的词）越多的小型网络转而生成比特币，压倒网络的门槛就越高，使得较大的网络也小到不足以压倒网络，于是它们也不妨转而生成比特币。根据"长尾"理论，小型、中型乃至仅仅是大型的网络加起来，其总量应远超过最大的僵尸网络。
即使坏人压倒了网络，也不意味着他立刻暴富。他所能做到的只是取回自己花掉的钱，就像开空头支票一样。要利用它，他得先从商家那里买东西，等商品发货，然后压倒网络，试图把钱要回来。我认为他搞这种盗刷骗局赚的钱，不会比生成比特币赚的多。拥有那么大的僵尸网络，他生成的比特币会比所有其他人加起来还多。
比特币网络甚至可能通过把僵尸网络引向生成比特币来减少垃圾邮件。
Satoshi Nakamoto
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英文原文
> As long as honest nodes control the most CPU power on the network,
> they can generate the longest chain and outpace any attackers.
But they don't. Bad guys routinely control zombie farms of 100,000
machines or more. People I know who run a blacklist of spam sending
zombies tell me they often see a million new zombies a day.
This is the same reason that hashcash can't work on today's Internet
-- the good guys have vastly less computational firepower than the bad
guys.
Thanks for bringing up that point.
I didn't really make that statement as strong as I could have. The requirement is that the good guys collectively have more CPU power than any single attacker.
There would be many smaller zombie farms that are not big enough to overpower the network, and they could still make money by generating bitcoins. The smaller farms are then the "honest nodes". (I need a better term than "honest") The more smaller farms resort to generating bitcoins, the higher the bar gets to overpower the network, making larger farms also too small to overpower it so that they may as well generate bitcoins too. According to the "long tail" theory, the small, medium and merely large farms put together should add up to a lot more than the biggest zombie farm.
Even if a bad guy does overpower the network, it's not like he's instantly rich. All he can accomplish is to take back money he himself spent, like bouncing a check. To exploit it, he would have to buy something from a merchant, wait till it ships, then overpower the network and try to take his money back. I don't think he could make as much money trying to pull a carding scheme like that as he could by generating bitcoins. With a zombie farm that big, he could generate more bitcoins than everyone else combined.
The Bitcoin network might actually reduce spam by diverting zombie farms to generating bitcoins instead.
Satoshi Nakamoto
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