从国内离职回到加拿大之后我就一直在 casually 思考区块链这个东西。今天看到了 Jesse Frederik 这篇文章（英文译者 Hannah Kousbroek）我觉得不用再想了——我没想到的他都说到了；我想到的就算写出来也不如他写的好。（因为网站倒闭所以额外链接一下 archive.org 的链接。）

关于区块链效率低下——

Enlightened – and thus former – blockchain developer Mark van Cuijk explained: “You could also use a forklift to put a six-pack of beer on your kitchen counter. But it’s just not very efficient.”

[…]> Carrying out a payment with Visa requires about 0.002 kilowatt-hours; the same payment with bitcoin uses up 906 kilowatt-hours, more than half a million times as much, and enough to power a two-person household for about three months.

关于 immutability 的负面性——

[The] technology is at loggerheads with European privacy legislation, specifically the right to be forgotten. Once something is in the blockchain, it cannot be removed. For instance, hundreds of links to child abuse material and revenge porn were placed in the bitcoin blockchain by malicious users. It’s impossible to remove those.

The fact that no one is in charge and nothing can be modified also means that mistakes cannot be corrected. A bank can reverse a payment request. This is impossible for bitcoin and other cryptocurrencies. So anything that has been stolen will stay stolen.

关于伪匿名性——

Also, in a blockchain you aren’t anonymous, but “pseudonymous”: your identity is linked to a number, and if someone can link your name to that number, you’re screwed. Everything you got up to on that blockchain is visible to everyone.

The presumed hackers of Hillary Clinton’s email were caught, for instance, because their identity could be linked to bitcoin transactions. A number of researchers from Qatar University were able to ascertain the identities of tens of thousands of bitcoin users fairly easily through social networking sites. Other researchers showed how you can de-anonymise many more people through trackers on shopping websites.

关于 “解决不存在的问题”——

OK, so with bitcoin, banks can’t just remove money from your account at their own discretion. But does this really happen? I have never heard of a bank simply taking money from someone’s account. If a bank did something like that, they would be hauled into court in no time and lose their license. Technically it’s possible; legally, it’s a death sentence.

关于线上线下数据匹配问题，这是我想了好久不知道如何表达清楚的地方。我想到的描述是，区块链解决了线上数据的可信度问题，但是一旦和线下实体经济结合，区块链就没有办法监督了。Jesse Frederik——

People lie and cheat. But the biggest problem is scams by data suppliers (for instance: someone secretly registers a hunk of horse meat as beef), not by data administrators (for instance: a bank makes money disappear).

Some people have suggested putting the Land Registry on the blockchain. That would solve all kinds of problems in countries with corrupt administrations. Take Greece, for example, where one in five buildings is not registered. Why are these buildings not registered? Because the Greeks just start building and then there’s suddenly a house that’s not in the Land Registry.

Except a blockchain can’t do anything about that. A blockchain is a database – it’s not a self-regulating system that checks all data for correctness, let alone one that calls a halt to unauthorised building works. The same rules apply for blockchain as for any database: if people put garbage into it, what comes out is also garbage.

Or as Bloomberg columnist Matt Levine wrote: “My immutable unforgeable cryptographically secure blockchain record proving that I have 10,000 pounds of aluminium in a warehouse is not much use to a bank if I then smuggle the aluminium out of the warehouse through the back door.”

点睛之笔在此：

Data should reflect reality, but sometimes reality changes and the data stays the same. That’s why we have notaries, supervisors, lawyers – actually, all those boring people that blockchain thinks it can do without.

2020 年底了我也不愿意再多想了。也许五年、十年之后我就被证明是错的。如果真的有那么一天我愿意回来复盘自己的思考是哪一步走错了路、当初的思路是在哪里有了盲区——可能这个恍然大悟会荣登人生恍然大悟十大时刻榜首。

但在那一天到来之前，区块链我就只会当做笑话看了。过两天把手里捏着的几百刀比特币和以太坊出了吧。