Off-chain protocols constitute one of the most promising approaches to solve the inherent scalability issue of blockchain technologies. The core idea is to let parties transact on-chain only once to establish a channel between them, leveraging later on the resulting channel paths to perform arbitrarily many peer-to-peer transactions off-chain. While significant progress has been made in terms of proof techniques for off-chain protocols, existing approaches do not capture the game-theoretic incentives at the core of their design, which led to overlooking significant attack vectors like the Wormhole attack in the past. In this work we take a first step towards a principled game-theoretic security analysis of off-chain protocols by introducing the first game-theoretic model that is expressive enough to reason about their security. We advocate the use of Extensive Form Games (EFGs) and introduce two instances of EFGs to capture security properties of the closing and the routing of the Lightning Network. Specifically, we model the closing protocol, which relies on punishment mechanisms to disincentivize parties to upload old channel states on-chain. Moreover, we model the routing protocol, thereby formally characterizing the Wormhole attack, a vulnerability that undermines the fee-based incentive mechanism underlying the Lightning Network.
翻译:离岸协议是解决链链技术固有的伸缩性问题最有希望的办法之一。核心思想是让各方仅一次在链上交易,在它们之间建立一条通道,在后来的通道上利用后方的渠道,任意进行许多同行对同行的离岸交易。尽管在离岸协议的验证技术方面已经取得重大进展,但现有办法并没有抓住其设计核心的游戏理论激励,这导致人们忽视过去虫洞袭击这样的重大攻击矢量。在这项工作中,我们迈出第一步,通过引入第一个足以说明其安全理由的游戏理论模式,对离岸协议进行有原则的游戏理论安全分析。我们主张使用广泛的形式游戏(EFGs),并举两例EFGs来捕捉关闭和光电网路线的保安特性。具体地说,我们模拟了关闭协议,依靠惩罚机制使各方无法上传旧频道国家上链。此外,我们模拟了基于“光电网”的“弱点”机制,从而正式地将“光路”机制化,从而破坏了“光电网”的弱点化。