Securing Parallel-chain Protocols under Variable Mining Power
Securing Parallel-chain Protocols under Variable Mining Power
复制标题
在可变挖矿能力下保护并行链协议
DOI：
10.1145/3460120.3485254
复制
发表时间：
0202
期刊：
影响因子：
--
通讯作者：
Viswanath, P
中科院分区：
文献类型：
--
作者：
Wang, X;Muppirala, V;Yang, L;Kannan, S;Viswanath, P
几种新兴的工作证明(PoW)区块链协议依赖于一种“并行链”架构进行扩展，在这种架构中，多个链并行运行并聚合，而不是单链。实用的POW区块链的一个关键要求是适应挖掘能力随时间的变化(比特币的总挖掘能力在过去十年中增加了1014倍)。设计了一种能够适应这种挖掘能力变化的可证明安全的并行链协议，比特币难度调整规则周期性地调整块挖掘的难度目标，以获得恒定的平均块间时间。尽管表面上看起来很简单，但事实证明，无论是在实践中还是在理论上，这条规则本身都是复杂和成功的。我们表明，比特币调整规则对平行链情况的自然适应，为微妙但灾难性的安全和活跃性违规打开了大门。我们发现了一个元设计原则，该原则允许我们在一个公共规则中为三个流行的POW区块链方案(棱镜、俄亥俄、果链)设计可变挖掘难度的协议。该原则有三个组成部分：(M1)枢轴链，基于所有链中的块选择难度，(M2)引用枢轴链块的单调性条件，以及(M3)将额外的协议方面从使用级别(深度)转换为使用“难度级别”。我们表明，采用这些原则的子集的协议可能会出现灾难性的故障。设计的安全性也用一个共同的准则得到了证明--关键的技术挑战涉及分析枢转链与其他链之间的相互作用，以及限制非枢转链所经历的难度目标的突然变化。我们通过基于历史比特币数据的模拟，对新的挖掘难度规则的响应性进行了实证研究，发现该协议非常有效地控制了所有链的分叉率。
Several emerging proof-of-work (PoW) blockchain protocols rely on a ''parallel-chain'' architecture for scaling, where instead of a single chain, multiple chains are run in parallel and aggregated. A key requirement of practical PoW blockchains is to adapt to mining power variations over time (Bitcoin's total mining power has increased by a 1014 factor over the decade). In this paper, we consider the design of provably secure parallel-chain protocols which can adapt to such mining power variations.The Bitcoin difficulty adjustment rule adjusts the difficulty target of block mining periodically to get a constant mean inter-block time. While superficially simple, the rule has proved itself to be sophisticated and successfully secure, both in practice and in theory. We show that natural adaptations of the Bitcoin adjustment rule to the parallel-chain case open the door to subtle, but catastrophic safety and liveness breaches. We uncover a meta-design principle that allow us to design variable mining difficulty protocols for three popular PoW blockchain proposals (Prism, OHIE, Fruitchains) inside a common rubric.The principle has three components: (M1) a pivot chain, based on which blocks in all chains choose difficulty, (M2) a monotonicity condition for referencing pivot chain blocks and (M3) translating additional protocol aspects from using levels (depth) to using "difficulty levels". We show that protocols employing a subset of these principles may have catastrophic failures. The security of the designs is also proved using a common rubric -- the key technical challenge involves analyzing the interaction between the pivot chain and the other chains, as well as bounding the sudden changes in difficulty target experienced in non-pivot chains. We empirically investigate the responsivity of the new mining difficulty rule via simulations based on historical Bitcoin data, and find that the protocol very effectively controls the forking rate across all the chains.
用于快速结算的账本组合器
DOI：
10.1007/978-3-030-64375-1_12
发表时间：
2020
期刊：
Theory of Cryptography (TCC 2020
影响因子：
--
作者：
Fitzi, Matthias;Gazi, Peter;Kiayias, Aggelos;Russell, Alexander
通讯作者：
Russell, Alexander
TaiJi：最长链可用性和BFT快速确认
DOI：
--
发表时间：
2020
期刊：
IACR Cryptology ePrint Archive
影响因子：
--
作者：
Songze Li;David Tse
通讯作者：
David Tse