六、限制
区块链产业仍处于发展的早期阶段，存在许多不同种类的潜在局限性。限制分为内部和外部两类，包括与底层技术的技术问题、持续的行业盗窃和丑闻、公众认知、政府监管以及主流技术采用相关的限制。
技术挑战
许多与区块链相关的 技术挑战，无论是具体的还是一般的模型，都已经确定。
开发人员清楚地看到了这些问题，对提出的挑战有不同的答案，并对潜在的解决方案进行了热烈的讨论和编码。对于能否以及如何克服这些问题，使区块链工业发展进入下一阶段，业内人士有着不同程度的信心。一些人认为事实上的标准将是比特币区块链，因为它是现任者，拥有部署最广泛的基础设施和如此的网络效应，它不能不成为标准化的基础。其他人正在建立不同的新的和独立的区块链(如以太坊)或不使用区块链的技术(如 Ripple)。比特币基础技术的一个核心挑战是从目前每秒 7 笔交易的最高限制(VISA 信用卡处理网络通常每秒处理 2000 笔交易，每秒可以容纳 10000 笔交易的峰值量)扩大规模，特别是如果比特币成为主流应用的话。 ^(178) 其他一些问题包括增加块大小、解决区块链膨胀、抵御 51%挖掘攻击的漏洞，以及对代码实施硬分叉(不向后兼容的更改)，如下所述: ^(179)
Throughput
The Bitcoin network has a potential issue with throughput in that it is processing only one transaction per second (tps), with a theoretical current maximum of 7 tps. Core developers maintain that this limit can be raised when it becomes necessary. One way that Bitcoin could handle higher throughput is if each block were bigger, though right now that leads to other issues with regard to size and blockchain bloat. Comparison metrics in other transaction processing networks are VISA (2,000 tps typical; 10,000 tps peak), Twitter (5,000 tps typical; 15,000 tps peak), and advertising networks (>100,000 tps typical).
Latency
Right now, each Bitcoin transaction block takes 10 minutes to process, meaning that it can take at least 10 minutes for your transaction to be confirmed. For sufficient security, you should wait more time—about an hour—and for larger transfer amounts it needs to be even longer, because it must outweigh the cost of a double-spend attack (in which Bitcoins are double-spent in a separate transaction before the merchant can confirm their reception in what appears to be the intended transaction). Again, as the comparison metric, VISA takes seconds at most.
Size and bandwidth
The blockchain is 25 GB, and grew by 14 GB in the last year. So it already takes a long time to download (e.g., 1 day). If throughput were to increase by a factor of 2,000 to VISA standards, for example, that would be 1.42 PB/year or 3.9 GB/day. At 150,000 tps, the blockchain would grow by 214 PB/year. The Bitcoin community calls the size problem “bloat,” but that assumes that we want a small blockchain; however, to really scale to mainstream use, the blockchain would need to be big, just more efficiently accessed. This motivates centralization, because it takes resources to run the full node, and only about 7,000 servers worldwide do in fact run full Bitcoind nodes, meaning the Bitcoin daemon (the full Bitcoin node running in the background). It is being discussed whether locations running full nodes should be compensated with rewards. Although 25 GB of data is trivial in many areas of the modern “big data” era and data-intensive science with terabytes of data being the standard, this data can be compressed, whereas the blockchain cannot for security and accessibility reasons. However, perhaps this is an opportunity to innovate new kinds of compression algorithms that would make the blockchain (at much larger future scales) still usable, and storable, while retaining its integrity and accessibility. One innovation to address blockchain bloat and make the data more accessible is APIs, like those from Chain and other vendors, that facilitate automated calls to the full Bitcoin blockchain. Some of the operations are to obtain address balances and balances changes, and notify user applications when new transactions or blocks are created on the network. Also, there are web-based block explorers (like https://blockchain.info/), middleware applications allowing partial queries of blockchain data, and frontend customer-facing mobile ewallets with greatly streamlined blockchain data.
Security
There are some potential security issues with the Bitcoin blockchain. The most worrisome is the possibility of a 51-percent attack, in which one mining entity could grab control of the blockchain and double-spend previously transacted coins into his own account.^(180) The issue is the centralization tendency in mining where the competition to record new transaction blocks in the blockchain has meant that only a few large mining pools control the majority of the transaction recording. At present, the incentive is for them to be good players, and some (like Ghash.io) have stated that they would not take over the network in a 51-percent attack, but the network is insecure.^(181) Double-spending might also still be possible in other ways—for example, spoofing users to resend transactions, allowing malicious coders to double-spend coins. Another security issue is that the current cryptography standard that Bitcoin uses, Elliptic Curve Cryptography, might be crackable as early as 2015; however, financial cryptography experts have proposed potential upgrades to address this weakness.^(182)
Wasted resources
Mining draws an enormous amount of energy, all of it wasted. The earlier estimate cited was $15 million per day, and other estimates are higher.^(183) On one hand, it is the very wastefulness of mining that makes it trustable—that rational agents compete in an otherwise useless proof-of-work effort in hopes of the possibility of reward—but on the other hand, these spent resources have no benefit other than mining.
Usability
The API for working with Bitcoind (the full node of all code) is far less user-friendly than the current standards of other easy-to-use modern APIs, such as widely used REST APIs.
Versioning, hard forks, multiple chains
Some other technical issues have to do with the infrastructure. One issue is the proliferation of blockchains, and that with so many different blockchains in existence, it could be easy to deploy the resources to launch a 51-percent attack on smaller chains. Another issue is that when chains are split for administrative or versioning purposes, there is no easy way to merge or cross-transact on forked chains.
另一个重大的技术挑战和要求是开发即插即用解决方案的完整生态系统，以提供服务交付的整个价值链。例如，链接到区块链需要安全的分散存储 (MaidSafe，Storj)消息传递、传输、通信协议、命名空间和地址管理、网络管理和归档。理想情况下，区块链行业的发展类似于云计算模式，标准基础设施组件(如云服务器和传输系统)在开始时被定义并快速实施，以使行业专注于更高层次的增值服务开发，而不是核心基础设施。由于分散式网络的敏感和复杂的密码工程方面，这在区块链经济中尤其重要。该行业正在理清一般区块链初创公司应该具备多少计算机网络安全、密码学和数学专业知识——理想情况下，如果他们可以依赖于一个安全的基础设施堆栈，而该功能已经存在，那么就不需要太多。这样，区块链行业的发展可以加快，而不是每个新企业都必须重新发明轮子，并担心其第一个面向客户的电子钱包不是 multisig(或无论当前的行业标准是什么，因为加密安全标准可能会继续迭代)。
这里讨论的技术问题的部分建议解决方案如下:
Offline wallets to store the majority of coins
Different manner of offline wallets could be used to store the bulk of consumer cryptocoins—for example, paper wallets, cold storage, and bit cards.
Dark pools
There could be a more granular value chain such that big crypto-exchanges operate their own internal databases of transactions, and then periodically synchronize a summary of the transactions with the blockchain—an idea borrowed from the banking industry.
Alternative hashing algorithms
Litecoin and other cryptocurrencies use scrypt, which is at least slightly faster than Bitcoin, and other hashing algorithms could be innovated.
Alternatives to proof of work for Byzantine consensus
There are many other consensus models proposed—such as proof of stake, hybrids, and variants—that have lower latency, require less computational power, waste fewer resources, and improve security for smaller chains. Consensus without mining is another area being explored, such as in Tendermint’s modified version of DLS (the solution to the Byzantine Generals’ Problem by Dwork, Lynch, and Stockmeyer), with bonded coins belonging to byzantine participants.^(184) Another idea for consensus without mining or proof of work is through a consensus algorithm such as Hyperledger’s, which is based on the Practical Byzantine Fault Tolerance algorithm.
Only focus on the most recent or unspent outputs
Many blockchain operations could be based on surface calculations of the most recent or unspent outputs, similar to how credit card transactions operate. “Thin wallets” operate this way, as opposed to querying a full Bitcoind node, and this is how Bitcoin ewallets work on cellular telephones. A related proposal is Cryptonite, which has a “mini-blockchain” abbreviated data scheme.
Blockchain interoperability
To coordinate transactions between blockchains, there are several side chains projects proposed, such as those by Blockstream.
Posting bond deposits
The security of proposed alternative consensus mechanisms like Tendermints’s DLS protocol (which requires no proof-of-work mining) could be reinforced with structural elements such as requiring miners to post bond deposits to blockchains. This could help resolve the security issue of the “nothing at stake in short time ranges” problem, where malicious players (before having a stake) could potentially fork the blockchain and steal cryptocurrency in a double-spend attack.^(185) Bond deposits could be posted to blockchains like Tendermint does, making it costly to fork and possibly improving operability and security.
REST APIs
Essentially secure calls in real time, these could be used in specific cases to help usability. Many blockchain companies provide alternative wallet interfaces that have this kind of functionality, such as Blockchain.info’s numerous wallet APIs.
商业模式挑战
另一个 提到的挑战，无论是功能性的还是技术性的，都与商业模式有关。起初，传统的商业模式似乎不适用于比特币，因为去中心化的点对点模式的要点是，没有中介机构收取佣金/交易费(就像一个经典的商业模式一样)。然而，在新的区块链经济中，仍然有许多有价值的创收产品和服务可以提供。教育和主流用户友好型工具是显而易见的唾手可得的成果(例如，被比特币基地、Circle Internet Financial 和 Xapo 瞄准)，提高整个全球现有银行和金融基础设施的效率也是如此，如 Ripple，这是另一个几乎“不用动脑筋”的项目，只要理解区块链原则。展望未来，在比特币 2.0 时代用智能合约重新配置所有业务和商业可能会很复杂，很难实施，服务提供商有很多机会提供实施服务、客户教育、标准制定和其他增值便利。随着企业软件和云计算发展起来的许多类型的商业模式中的一些可能也适用于比特币经济——例如，红帽模式(实现开源软件的收费服务)和 SaaS，提供软件即服务，包括定制。未来一个可能的工作可能是智能合约审计师，以确认在区块链上运行的人工智能合约确实按照指示行事，并确定和测量智能合约如何自我重写，以最大化发行代理的效用。
丑闻和公众认知
进一步采用比特币的最大障碍之一是其公众认为它是暗网洗钱、毒品相关和其他非法活动的场所(以及可能的教唆者)，例如丝绸之路等非法商品在线市场。比特币和区块链本身是中性的，和任何技术一样，是“两用”的；也就是说，它们可以被用来行善或作恶。尽管存在恶意使用区块链的可能性，但潜在的好处远远大于潜在的坏处。随着时间的推移，随着越来越多的个人拥有电子钱包并开始使用比特币，公众的看法可能会发生变化。尽管如此，必须承认，比特币作为一种假名的使能手段，可以被用来促进非法和恶意活动，这导致了适合区块链的实物“红皇后”反应(特定背景的进化军备竞赛)。计算机病毒检测软件是为了应对计算机病毒而出现的；到目前为止，比特币的相同构成技术(如 Tor，一个自由开放的软件网络)的一些功能已经被重新部署到检测恶意玩家中。
比特币采用的另一个重大障碍是该行业正在发生的盗窃、 丑闻和骗局(如所谓的新替代币“泵和转储”骗局，试图哄抬新替代币以快速获利)。2014 年 3 月，当时最大的比特币交易所东京 MtGox 的倒闭引起了公众的广泛关注。令人困惑的讽刺是，在区块链这个世界上最公开透明的账本中，货币可能会消失，但几个月后仍然会丢失，这仍然需要解释。该公司表示，它已被黑客攻击，欺诈是一个被称为“交易延展性漏洞”的问题的结果。这个漏洞允许恶意用户重复消费，将比特币转入他们的账户，同时让 MtGox 认为转账失败，从而重复交易，实际上是将价值转移了两次。 ^(186) 分析师仍然不确定 MtGox 是外部黑客还是内部盗用。问题是这种盗窃行为持续存在。例如，最近的头条新闻告诉我们，Moolah 首席执行官带着 140 万美元的比特币失踪(2014 年 10 月)，^(187)【2014 年 7 月】 ^(188) 和 62 万美元在 Dogecoin 采矿攻击中被盗(2014 年 6 月)。 ^(189)
区块链行业模型需要巩固和成熟，以便有更好的保护措施来稳定行业，并允许内部和外部人士区分好的和坏的参与者。监督不需要来自外部；可以在生态系统内建立相应的分散审查、确认和监测系统。一个来自公民科学的类比是，人们意识到监督职能仍然重要，并通过提供制衡来加强系统。例如，在 DIYgenomics 参与者组织的研究中，监督职能仍然履行，但在某些情况下，与传统的自上而下的监督者(以人类受试者研究机构审查委员会的形式)相反，监督职能具有与生态系统相关的全新角色——独立的公民伦理学家。其他自律行业包括电影、电子游戏和漫画。
整个区块链行业有可能崩溃(要么是由于已经预测到的问题，要么是其他一些尚未预见到的因素)。没有迹象表明崩溃是不可能的。从各种指标来衡量，区块链经济确实表现强劲，如货币市值、对该行业的投资、创业公司和在该行业工作的人数、GitHub 代码提交的行数以及该行业的“报纸油墨”数量。与之前的数字货币(像第二人生林登币这样的虚拟世界货币)相比，区块链的产业已经变得更大更完善。然而，尽管比特币取得了迄今为止的进步和崇高的理想，但也许对数字货币来说还为时过早；也许所有正确的保护措施和结构都还没有到位，数字货币还没有完全成为主流(尽管 Apple Pay 比其他任何因素都更有可能为数字货币的完全主流接受铺平道路)。短期来看，Apple Pay 可能已经足够了。比特币要想拥有 Apple Pay 一样的用户友好属性还需要很长时间，比如确认等待时间时间。
政府管制
政府监管如何展开，可能是区块链金融业能否发展成为成熟的金融服务业的最重要因素和风险之一。在美国，可能有联邦和州一级的立法；关于备受争议的纽约比特许可证的讨论继续进入第二个意见征询期。纽约的比特许可证可以为全球监管定下基调。一方面，比特币行业对目前提议的许可证中极其宽泛的域外语言感到担忧。该许可证将涵盖任何人用其他人的比特币做任何事情，包括基本的钱包软件(如 QT 钱包)。 ^(192) 然而，另一方面，对比特币行业参与者的监管消费者保护，如 KYC (know your customer)对货币服务企业(msb)的要求，可能会加速行业的主流发展，并消除消费者对似乎困扰行业的黑客袭击的担忧。
世界各国政府对比特币的审议和早期裁决提出了一些有趣的问题。一个问题是，用目前的方法征税实际上是不可能的。Airbnb 2.0 和优步 2.0 的分散式点对点共享经济运行在 OpenBazaar 的本地实现上，个人使用加密货币支付，这使得传统的税收结构变得不可能。跟踪商品和服务消费的常规跟踪和瓶颈可能会消失。这对税收和 GDP 计算等经济表现的整体衡量指标都有影响，这可能会产生有益的影响，使人们不再过度、甚至可能错误地将消费作为健康指标。取而代之的是，可以对税收制度进行彻底改革，对大额有形资产(如汽车、房屋)征收基于消费的税。对于税收来说，瓶颈点需要很容易被发现，这是一个“即期税”的概念。从以所得税为基础的体系向以消费税为基础的体系的潜在转变可能会给社会带来重大变化。
区块链科技提出的关于政府监管的第二个问题是政府及其商业模式提供的价值主张。一些人认为，在现代大数据时代，政府越来越无法履行记录和归档信息并使数据易于访问的记录义务。根据这种观点，政府可能会变得过时，因为它们无法通过传统的方式——增加税收——为自己融资。区块链技术可能有助于解决这两个挑战，并且至少可以补充和帮助政府更好地完成自己的工作，最终使政府提供的服务变得多余。在区块链记录一个社会的所有记录可以消除对整个公共服务阶层的需要。这种观点赤裸裸地把政府描绘成随着区块链政府特征的民主化而变得多余。
然而，正如可能有集中和分散的模式来协调我们在世界上的活动一样，传统政府和以区块链为基础的新形式的政府可能都有各自的角色。传统的中央集权政府可能还会发挥作用，但它们需要在经济上变得更加合理，具有真正的价值主张，能够引起选民的共鸣，降低成本，并展示有效性。未来可能会出现混合政府，就像其他行业一样，自动化是强制功能，而这项工作的最佳“工人”是人类/算法配对。 ^(193) 敷衍塞责的重复性工作通过区块链登记处和智能合约实现了自动化，而政府雇员则可以向价值链上游 移动。
个人记录的隐私挑战
在个人对以分散的方式用指针存储他们的个人记录并可能通过区块链访问感到舒适之前，有许多问题需要解决。潜在的隐私噩梦是，如果你所有的数据都在网上，密钥被盗或暴露，你几乎没有追索权。在当前的加密货币架构中，有许多可能发生这种情况的场景，就像今天个人和公司密码经常被盗或数据库被黑客攻击一样——具有广泛而浅的后果；成千上万的人处理一个通常很小的不便。如果一份完整的个人记录被盗，对一个人来说，其影响可能是惊人的:身份盗窃到了你根本不再拥有 身份的程度。
总体而言:权力下放趋势可能会持续下去
然而，尽管仍处于萌芽状态的区块链经济存在种种潜在限制，但比特币无疑是一股颠覆性力量，其影响将是巨大的。即使区块链产业目前开发的所有基础设施都消失了(或者像虚拟世界一样不再受欢迎)，它们的大部分遗产仍将存在。区块链经济为如何做事提供了新的更大范围的想法。即使你不相信比特币作为一种稳定、长期的加密货币的未来，也不相信目前正在构想和开发的区块链技术，去中心化模型也有非常强的理由。权力下放是一个时机已经成熟的想法。互联网足够大，流动性足够强，能够以新的、比以前更普遍的方式容纳去中心化的模型。集中式模型在当时是一个好主意，是数百年前人类协调的创新和革命，但现在我们有了新的文化技术、互联网和分布式公共区块链总账等技术，可以促进活动不仅首次包括所有 70 亿人，还允许更大规模、更复杂的协调，并加速我们向真正先进的社会迈进。如果没有区块链工业，可能会有其他东西，事实上可能会有和成为区块链工业的补充。只不过，区块链工业是第一个可识别的大规模实施分权模式的行业之一，它是在一个新的、更复杂的人类活动水平上构思和执行的。
