[论文解读] On The Longest Chain Rule and Programmed Self-Destruction of Crypto Currencies

Nicolas T. Courtois|arXiv (Cornell University)|May 2, 2014

Blockchain Technology Applications and Security参考文献 5被引用 44

一句话总结

本文通过揭示最长链规则和货币设计中的关键缺陷，挑战了比特币及各类代币在安全性和可持续性方面的表现。文章指出，由于缺乏时间戳机制和不良的检测机制，当前系统极易遭受双重支付攻击，并提出应通过交易时间戳和节点确认机制来增强安全性和网络中立性，从而减少对巨大算力的依赖。

ABSTRACT

In this paper we revisit some major orthodoxies which lie at the heart of the bitcoin crypto currency and its numerous clones. In particular we look at The Longest Chain Rule, the monetary supply policies and the exact mechanisms which implement them. We claim that these built-in properties are not as brilliant as they are sometimes claimed. A closer examination reveals that they are closer to being... engineering mistakes which other crypto currencies have copied rather blindly. More precisely we show that the capacity of current crypto currencies to resist double spending attacks is poor and most current crypto currencies are highly vulnerable. Satoshi did not implement a timestamp for bitcoin transactions and the bitcoin software does not attempt to monitor double spending events. As a result major attacks involving hundreds of millions of dollars can occur and would not even be recorded. Hundreds of millions have been invested to pay for ASIC hashing infrastructure yet insufficient attention was paid to network neutrality and to insure that the protection layer it promises is effective and cannot be abused. In this paper we develop a theory of Programmed Self-Destruction of crypto currencies. We observe that most crypto currencies have mandated abrupt and sudden transitions. These affect their hash rate and therefore their protection against double spending attacks which we do not limit the to the notion of 51% attacks which is highly misleading. In addition we show that smaller bitcoin competitors are substantially more vulnerable. In addition to small hash rate, many bitcoin competitors mandate incredibly important adjustments in miner reward. We exhibit examples of 'alt-coins' which validate our theory and for which the process of programmed decline and rapid self-destruction has clearly already started.

研究动机与目标

• 分析比特币最长链规则中的安全缺陷及其对双重支付防御能力的影响。
• 揭示当前加密货币设计（尤其是各类代币）因突然的货币制度过渡而易导致程序化自我毁灭的机制。
• 论证高算力既非安全的必要条件也非充分条件，且当前系统在检测或防范双重支付攻击方面表现不佳。
• 提出一种新的交易验证框架，整合时间戳与节点确认机制，以提升网络中立性与安全性。

提出的方法

• 本文分析比特币与各类代币协议，重点关注软件栈中缺乏交易时间戳以及缺乏主动的双重支付监控机制。
• 通过建模快速、预编程的货币过渡对矿工奖励与网络安全的影响，揭示此类机制如何引发自我毁灭性动态。
• 作者提出将交易时间戳整合进共识决策过程，认为这将随时间推移使双重支付攻击更加困难。
• 主张引入新激励机制，鼓励更多节点参与网络，以降低矿工集中化程度与自主权力。
• 本文利用比特币12个月内算力增长1000倍的实证数据，以及各类代币（如Dogecoin、Litecoin）的案例，说明系统性风险。
• 提出“程序化自我毁灭”的理论框架，即结构性设计缺陷将导致加密货币的可预测性衰退。

实验结果

研究问题

• RQ1 为何当前加密货币（尤其是各类代币）尽管投入了巨额算力，仍极易遭受双重支付攻击？
• RQ2 比特币软件中缺乏交易时间戳与主动的双重支付检测机制，如何削弱网络安全性？
• RQ3 各类代币中突然的货币制度过渡在多大程度上加速其衰落并增加受攻击风险？
• RQ4 能否通过交易时间戳与节点确认机制提升安全性，并减少对过度算力的依赖？
• RQ5 为何比特币在存在结构性缺陷的情况下仍能保持主导地位，而较小的竞争对手却因此走向灭亡？

主要发现

• 比特币软件并未监控或记录双重支付事件，意味着涉及数亿美元的攻击可能完全未被察觉。
• 比特币矿工算力在12个月内增长1000倍，但由于共识机制存在缺陷，其双重支付防御能力并未提升。
• 像Dogecoin这样的小型代币，由于快速且预编程的货币过渡，现极易遭受单个矿工的双重支付攻击。
• 许多代币已加速其过渡时间表，使其成为“拉高出货”策略与程序化自我毁灭的高风险目标。
• 当前设计使比特币实际上获得垄断优势，这并非源于更优的安全性，而是因为竞争对手复制了其有缺陷的机制却未理解其后果。
• 本文结论认为，庞大的算力基础设施既非安全数字货币运行的必要条件，也非充分条件，而基于时间戳的验证机制才是关键。