回复：在滚动时间窗口内使比特币保持不可花费状态

此前来信Mike Hearn→ 中本聪2011-04-20原文来源 ↗

谢谢，很有帮助。我现在更理解合约了。

Thanks, that's helpful. I'm understanding contracts better now.

所以，加入 OP_TIME/OP_BLOCKNUMBER 操作码的问题，不仅在于链重组后结果可能改变（你之前提到过），还在于人们可以用它生成在某个时间之后完全失效的交易，从而造成分叉。回头看，这其实挺明显的。

So the issue with having an OP_TIME/OP_BLOCKNUMBER opcode is not only that the results can change after a re-org (you said that previously), but also that people could use it to produce transactions that cease to be valid entirely after a certain time and cause a fork. Kind of obvious in hindsight.

谷歌与信任之间的关系很复杂。很多人虽然不太信任我们，仍然使用我们的服务。有些人起初信任我们，后来读了媒体上的报道（常常是耸人听闻或不实的），又改变了看法，诸如此类。这也是我们做电话验证时遇到的问题之一……有些人不愿把电话号码交给我们。

Google and trust is a complicated issue. Lots of people use our services despite having little trust in us. Some people start out trusting us but then read (often sensationalist or wrong) stories in the media that change their minds, and so on. This is one of the problems we have with phone verification ... a few people don't want to give us their phone number.

在这个场景中，问题可能不大，因为对数据隐私的信任，与对履行合约的信任是两回事。我相信没人会怀疑谷歌会把钱还给他们——在这方面，我敢打赌我们的信用评级甚至会比美国政府还高 :-) 不过，我们的验证误判率相当高，有些人可能会怀疑，我们让用户因误判而接受验证，是为了积攒大量的币来赚利息。我见过比这荒唐得多的阴谋论也有人相信。

For this case it'd probably be OK because trust around data privacy is different to trust around obeying contracts. I'm sure nobody would doubt that Google will pay them back - I bet we'd have an even better credit rating than the US Government in that sense :-) But we have quite a high rate of false positives with our verifications and some people would suspect we were accidentally verifying users in order to accumulate big piles of coins with which to earn interest. I've seen much sillier conspiracy theories gain traction.

再说，避免依赖庞大、复杂的机构，本来也更符合比特币的思路。而且，我之前猜想有一种我还没弄明白的做法，果然如此。这正好是进一步了解比特币的机会。

Besides, avoiding the need to trust big, complex institutions is much more BitCoin-ish. And I correctly suspected there was a way to do it I didn't understand yet so it's a good chance to learn more about BitCoin.

如果我写一篇介绍如何用比特币构建合约的维基页面，你愿意帮忙审阅一下吗？

If I wrote a wiki page on how to build contracts with BitCoin, would you mind reviewing it?

我在想，也许应该尽快重新启用交易替换，因为随着网络发展，升级会变得越来越难。从一个角度说，这是好事，因为它让系统的基本规则难以更改。另一方面，协议中的许多功能可能会因为缺乏广泛支持而一直用不上。HTTP 的许多请求方法，以及请求流水线等功能，都遇到过这种情况。

I'm thinking it might be a good idea to re-enable transaction replacement soon because as the network grows, it will become harder and harder to upgrade. In one sense this is good as it makes it hard to change the fundamental rules of the system. On the other hand, we risk having a protocol which has many unused features because they aren't widely supported enough. HTTP suffered this fate with many of its verbs as well as features like pipelining.

对于重新启用这项功能，你是否列过任务清单，比如需要做哪些审查，或者还要完成哪些代码？

Did you have any list of tasks for re-activation, some kind of audit or finishing off some code?

我还有几个问题想问（和往常一样）。其中一个是，你是否打算在某个时候重新参与社区（比如审查代码），还是打算永远淡出公众视野？我不断向你提问，原因之一是要发挥比特币的许多潜力，需要谨慎运用目前尚未启用的功能，而我担心的是，这方面的指导太少。坦白说，我觉得自己还没有聪明到能独自把一切都弄明白。也许 theymos 可以，他似乎理解得很透彻。但如果有一天你完全离开，协议的某些部分可能就会被荒废，那实在可惜。

I had a few other things on my mind (as always). One is, are you planning on rejoining the community at some point (eg for code reviews), or is your plan to permanently step back from the limelight? One reason I'm peppering you with questions is I worry that much of BitCoins potential lies in careful use of currently inactive features, but there's little guidance on how to do it. And frankly, I don't think I'm smart enough to figure it all out on my own. Maybe theymos is, he seems to understand it well. But if one day you leave entirely, parts of the protocol might fall into disuse, which would be a shame.

另一个问题是，过渡到完全依赖手续费的系统之后，挖矿的经济机制会怎样。目前，难度大致取决于美元与比特币的汇率，以及每个区块带来的货币增发量。当挖矿报酬由市场决定时，会不会出现“公地悲剧”：所有人都受益于较高的难度，却没有哪个人特别愿意为此支付手续费？此外，要判断难度的价值也很困难，因为当你终于知道攻击者有多强时，已经来不及了。会不会随着时间推移，手续费逐渐趋近于零，因为总有矿工愿意接受手续费更低的交易；而随着矿工退出，难度又会调整，使延迟始终不至于高到无法忍受？

Another is the economics of mining after the transition to a fully fee based system. Right now difficulty is roughly a function of the USD/BTC exchange rate and per-block inflation. When mining reward is set by the market, it might be possible for a "Tragedy of the commons" to occur in which everyone benefits from a high difficulty, but nobody specifically wants to pay fees to get it. Besides, valuing difficulty is quite hard as you never know what the capabilities of attackers are until it's too late. Would it be possible for fees to trend towards zero over time as some miner is always willing to accept cheaper transactions and as miners drop out, the difficulty adjusts so the delays never get too bad to tolerate?

一如既往，感谢你分享见解。

As always thanks for your insights.