对话Adam Back：比特币白皮书发布十周年，经历了哪些技术演进？

Adam Back，他的twitter页面介绍为，赛博朋克，密码学家，隐私保护/电子现金，Hashcash（被用作比特币挖矿）发明人，计算机科学博士，Blockstream联合创始人兼CEO。

正如他的标签提到的，Hashcash是比特币白皮书引用不多的内容之一，Adam Back的名字被写入了比特币白皮书，工作量证明也成为了比特币的基石。（这篇文章讲述了Adam Back是如何推动比特币诞生的）

2014年，Adam back在美国旧金山创办了Blockstream，聘请了几位比特币核心开发者，持续推动比特币和区块链技术的发展与应用。

站在比特币白皮书发布十年的节点上，我们访问了Adam Back，话题包括这几年来比特币的技术演进，闪电网络，侧链，保密交易等技术进展，未来可能突破的技术方向，Adam还展望了比特币的未来，他认为比特币正处于新技术的接纳阶段，就像互联网，手机最初被采用那样。而未来十年将会更有趣，因为我们会看到比特币被广泛采用，众多新应用程序和用途被开发。

以下为访谈全文：

8btc：从比特币的诞生到现在，你认为比特币在技术演进上经历了哪些关键节点？有哪些技术突破？
Since the creation of bitcoin, are there any key points about technology evolution you can think of? Any important technology breakthroughs?

Adam Back：这些年来，比特币在代码效率、可扩展性及网络协议（同步速度量级提升）等方面都有了巨大的进步，还有着许多可用性的改进，包括HD钱包（更容易备份）、P2SH（可以发送至接收者选择的复杂脚本，并在发送时段保持公开)等。我认为双向支付通道（Decker和Wattenhofer）和闪电网络 （Poon和Dryja） 给比特币提供了巨大的可扩展性优势，同时也提供了速度更快、成本更低的零售支付及微支付方式——比特币很棒了，但我们希望所有对它感兴趣的人们都能够使用它，所以可扩展性很重要！

There have been huge improvements over the years in Bitcoin’s code efficiency, scalability and network protocol (orders of magnitude faster sync) as well as many usability improvements, including HD Wallets (easier to backup), P2SH (ability to send to complex scripts chosen by recipient to be disclosed at spending time). I think duplex payment channels (Decker and Wattenhofer) and Lightning (Poon and Dryja) offer huge scalability advantages while providing faster, cheaper retail payments as well as enabling micropayments – Bitcoin is great but we would like everyone interested to be able to use it, so scalability is important!

8btc：哪些技术是重要的，值得肯定的？另一方面，我们有没有走一些弯路？
Can you give us examples of some useful/important technologies? On the other side, did we make any mistakes?

Adam Back：早期比特币存在着较多漏洞，但那些明显的漏洞似乎大多已经被修复了。尽管经过了更加严格的开发和审查过程，但软件依然是复杂的，有些漏洞仍然不容易被发现和修复完善。
In the early days of Bitcoin there were some more major bugs, but the shallow bugs seem to be mostly fixed. However despite overtime more rigorous development and review processes, software is complex, and some bugs are still though infrequently discovered, and carefully fixed.

8btc：比特币以后会不会有硬分叉扩大区块的计划？还是只会专注于其它的技术方案，例如闪电网络、侧链这些layer 2 方案？
Will bitcoin go through a hard fork to increase the blocksize? Or layer-2 technologies like lightning network, sidechain are our only ways to solve this kind of problem?

Adam Back：我认为长远看来，随着技术的进步，更紧凑的交易将变得可能，如schnorr聚合签名及未来的其他创新等，将可以更有效地使用区块空间。因为比特币基础层是一种广播机制，所以在验证成本间总是存在着权衡，为了让比特币能够成为P2P网络和承载网络，使企业和高级用户能够同步和验证它的区块链是非常重要的。然而，随着技术和网络容量的提高，其效率和规模都可能通过某种机制得到提高。
I think longer term as technology improves more compact transactions become possible, like schnorr aggregated signatures, and other innovations in the future, allow more efficient use of block-space. Because Bitcoin base layer is a broadcast mechanism there is always a tradeoff between cost of validation, where in order for Bitcoin to be p2p and bearer, it is important that businesses and power users be able to sync and validate the chain. However as technology and networking capacity improves it maybe that both efficiency and size increases via some mechanism.

侧链并不是真正的可扩展性解决方案，因为它们有类似的权衡，高级用户需要能够验证区块链来使其有意义地成为一条可公开审计的区块链。
侧链更多的，是为特定的用例引入那些对比特币主链来说可能没有意义的新功能，或者这些功能也可以先在侧链上进行尝试，然后再添加到比特币中。
Sidechains are not really a scaling solution as they have a similar tradeoff where power users need to be able to verify the chain for it to meaningfully be a publicly auditable blockchain. Sidechains are more about introducing new features for specific use cases that may not make sense for the main Bitcoin chain, or that can be tried first on a sidechain and may be later added to Bitcoin.

闪电网络及其他layer 2解决方案为可扩展性提供了非常好的权衡，通过闪电网络的一些权衡改进，使得其数量级和规模能比在链上进行公开审计的更加的大。
Lightning and other 2nd layer solutions offer a hugely better tradeoff for scalability, with Lighning via some trade-offs, being able to provide many orders of magnitude more scale, than would be plausibly publicly audited on-chain.

8btc：能否介绍一下闪电网络和侧链技术方案的进展？
Can you tell us about the progress of lightning network and sidechain?

Adam Back：闪电网络似乎进展得非常快，有着众多的黑客马拉松、众多独立实现（c-lightning、LND和eclair）、独立协议开发者及众多钱包，还有非常活跃的闪电网络应用开发者对其感兴趣。
The lightning network seems to be progressing very rapidly with many developer hackathons, multiple independent implementations (c-lightning, LND and eclair), independent protocol developers and multiple wallets and very active Lightning application developer interest.

侧链方面也在积极开展工作，Blockstream为比特币交易所清算服务的Liquid网络已经推出上线，且支持更加保密、更加快速的清算和流动资产支持。Liquid使用联盟信任模型来降低交易中的托管风险。此外，包括Drivechain和RootStock等，侧链的变体和概念还在不断改进。
There is active work on sidechains, with Blockstream’s Liquid network for Bitcoin-exchange settlement now being live and enabling more confidential, faster settlement, and Liquid Asset support. Liquid uses a federated trust model to reduce custody risk from trading. Also there is ongoing work on improving sidechain variants and concepts including drivechain, and rootstock.

8btc：我们该如何看待软件安全漏洞，例如近期发生的core软件漏洞事件？
We know that Bitcoin Core client had a severe bug recently, which was already fixed. How should we deal with software bugs in the future?

Adam Back：软件开发是人类工作最复杂的领域之一。类似飞机系统，比特币开发在开发审查和测试方面采取了非常谨慎的方法。当发现漏洞时，就像飞机事故一样会进行事后分析，以确定原因及审查修改程序，吸取教训来防止类似问题再次发生。
Software development is one of the most complex areas of human undertaking. Like aircraft systems, Bitcoin development takes a very cautious and careful approach to development review and testing. When bugs are discovered, like with aircraft incidents, a post-mortem is done to determine the causes and processes reviewed and amended to try to draw lessons and prevent a similar issue recurring.

8btc：由Blockstream联合斯坦福大学、伦敦大学学院提出的Bulletproofs技术方案，已经在门罗币上得到了应用，那这种技术是否会应用到比特币的身上呢？如果可以的话，优缺点在哪？
Bulletproofs is developed by Blockstream, Stanford university and University College London. It is implemented in Monero network. Do you think bitcoin can be adopted this tech? If so, what are the advantages and disadvantages?

Adam Back：就我个人而言，我希望看到比特币最终能实现保密交易。目前保密交易已经可以在Liquid侧链和相关FOSS项目中实现使用。上述研究机构的研究人员进行调查期间，为了进一步优化保密交易使用的范围证明（range proofs），Bulletproofs技术便出现了。
Personally I would be interested to see Confidential Transactions implemented in Bitcoin eventually. Already today CT is available for live use in the Liquid sidechain and the associated Elements FOSS project. BulletProofs arose during an investigation by researchers at the mentioned research institutions to further optimise the range proofs used by Confidential Transactions.

实际上，除了为保密交易提供更紧凑和更符合对数缩放的范围证明之外，Bulletproofs还是执行的通用签名，能够证明程序的执行，类似于SNARKs，但其具有更健壮的保守安全保证。Bulletproofs及其他技术的进一步优化，对比特币和区块链的优化来说可能有着有趣的应用。特别是执行递归证明的前景非常有趣，因为程序会是另一个程序的解释器。
In fact as well as providing a more compact and log-scaling range-proof for CT, BulletProofs are a general signature of execution able to make proofs of program execution, similar to SNARKs but with more robust conservative security assurances. BulletProofs, and further optimisation of them may have interesting applications for Bitcoin and blockchain optimisation. Particularly the prospect of recursive proofs of execution is interesting, where the program is an interpreter for another program.

8btc：对于可能替代Merkle tree数据结构的RSA累加器方案，斯坦福大学的Benedikt Bünz提出说通过这种方案可以有效压缩比特币区块链的UTXO集大小，另外以太坊创始人Vitalik也在研究这种数据结构，这种方案能否应用到比特币身上呢？如果可以的话，预计效果会怎样？
Proposed by Benedikt Bünz from Standford University, RSA accumulators can replace Merkle tree by compressing bitcoin UTXO. Ethereum’s founder Vitalik also pays a lot attention on this solution. Do you think it can be adopted on bitcoin? If so, what can it do for bitcoin?

Adam Back：RSA累加器的权衡之处是，其安装过程中必须删除一个主私钥。所以我个人认为，在“去信任验证”的比特币中很难使用这一方案。RSA累加器是一个有趣的技术机制，其来源可以追溯至1993年Benaloh的论文。在zeroCash的白皮书中也对其进行了探讨以构造零知识身份证明。
A trade-off with RSA accumulators is that there is a master private key that must be deleted during setup. So personally I think it is difficult to use that in Bitcoin which has a “Don’t Trust. Verify” approach. RSA accumulators are an interesting technical mechanism dating back to Benaloh’s 1993 paper. They were also explored in the zeroCash paper, to construct zero-knowledge set membership proofs.

8btc：对于以太坊2.0 的分片+Casper+Plasma 发展计划，您有什么看法？
What do you think of Ethereum 2.0? i.e. sharding+Casper+Plasma.

Adam Back：我并没有真正地去追踪很多相互竞争的共享系统，因为现在有这么多的共享系统，而且我认为比特币的安全性及其以效率为中心的分层方式更有希望。
I don’t really track the many competing shares systems as there are so many, and I see more promise in Bitcoin’s security and efficiency focussed approach with layers.

8btc：对于区块链的安全、去中心化以及效率的“不可能三角”猜想您是怎么看的？有些团队认为可以打破这个猜想，您觉得可能吗？
There’s a theory known by blockchain community named ‘impossible triangle’. It means that a blockchain system cannot have security, decentralization and effectiveness simultaneously. You can only get two of them and abandon the other one. What do you think of this theory? Some blockchain projects think they can break this ‘curse’, do you think it is possible for them to do so?

Adam Back：我想我们需要一些新的BulletProof/ SNARK之类的创新来打破这个不可能三角。就我至今所见，还没有人能既保留工作证明激励保障机制，又保留比现有的比特币模型更好的完整验证模型。这并不是要否定研究，但它反映出这是一个棘手的问题，且人们往往会低估自己所做的权衡折衷。
I think we will need some new BulletProof / SNARK like innovations to break this triangle. From what I have seen so far no one has retained proof-of-work incentive security, and retained a full-validation model with better than the existing Bitcoin model. This is not to dismiss research, but reflects that this is a hard-problem and people tend to discount the trade-offs they have made.

8btc：现在的比特币开发社区是怎样的？跟最开始的时候有哪些关键区别？普通人能否参与其中呢？
What does bitcoin developer community look like now? Any difference between the earliest one and nowadays? Can an ordinary person join this community?

Adam Back：据我所知，现在你可以在发行版名单上看到有数百名开发者。许多早期的开发者们仍然非常活跃，也有一些新的开发者也加入了进来。当然，许多方面我们都可以加入并提供帮助，包括撰写文档、测试、教育和学习其协议及其代码，还有应用程序开发、构建用例和培训用户等方面。同时还有一些开发者培训计划和行业/开发者最佳实践计划等。
From what I hear there are now hundreds of developers that you can see listed on releases. Many of the early developers are still very active, and some new active developers have joined. There is certainly scope to join in and help in many ways, including documentation, testing, education and learning the protocols and code. As well as application development, building use-cases, and training users. There are several developer training programs and industry / developer best practices initiatives at this point also.

8btc：站在比特币十年的节点上，你对未来有什么预测或展望？
Bitcoin has gone through ten years since its birth, what predictions you can make for its future? Or can you tell us how it will develop in the future? You can talk about price, possible applications and technology developments, etc..

Adam Back：就我个人而言，我希望能看到比特币的可替换性得到改善，还有比特币协议和节点软件的每一个主要发行版中都能有一些能提高隐私保护的增量内容，比如schnorr签名、taproot、闪电网络layer2支付提供的dandelion等相关协议。我还希望能看到更多有雄心的方法，比如经验证和优化的保密交易等方法最终以各自的方式融入比特币。
Personally I would like to see fungibility improved, and there are incremental things that improve privacy in each major release of the Bitcoin protocol and node software, like schnorr signatures, taproot and related protocols, dandelion as well as the privacy provided by Lightning layer2 payments. I would also like to see more ambitious approaches like Confidential Transactions validated and optimised more eventually make their way into Bitcoin.

很难说价格会怎么样，但在我看来，比特币似乎仍处于新技术的接纳阶段，正如互联网、手机最初被采用那样。在某种程度上，对于那些看重比特币所提供的独特用例的人来说，比特币将达到其应用S曲线的顶端，成为抗审查的电子货币，或其希望持有比特币，将其作为一种资产类别与黄金竞争：比特币有一些类似黄金的属性，但与实物黄金相比有很多优势。一些人正进一步计划实现超级比特币化( hyperbitcoinization)，给各国货币带来竞争，特别是对于那些存在恶性通货膨胀或其他货币问题的国家。但就我个人而言，我认为，如果比特币与黄金竞争，那就已经非常有趣了，根据对实物黄金私人拥有量的估计，已经可以设想其价格的显著上涨。我们将会看到接下来会发生什么。接下来的10年应该会很有趣，因为我们会看到其被广泛接纳采用、还有众多新应用程序及用途被开发。
It’s hard to say what price will do, but to me it does seem like Bitcoin is still in the adoption phase of new technology as Internet use, mobile phones saw in their initial adoption. At some point Bitcoin will reach the top of it’s adoption S curve for people who value the unique use-cases Bitcoin offers, as the censor resistant electronic money, or wish to hold Bitcoin as an asset class competing with gold: Bitcoin has some similar properties but a number of advantages vs physical gold. Some people are projecting further out to hyperbitcoinization providing competition to national currencies, particularly in countries with hyperinflation or other monetary problems. But personally I think it’s already interesting if Bitcoin competes with gold which already envisages significant price growth depending on estimates of the private ownership of physical gold. We’ll see what happens after that. The next 10 years should be interesting as we see adoption play out and new applications and uses develop.

感谢思敏，Linkea，洒脱喜，Wendy对此次访谈做出的贡献。