On the optionality and fairness of Atomic Swaps
On the optionality and fairness of Atomic Swaps
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DOI：
10.1145/3318041.3355460
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发表时间：
2019-10
期刊：
影响因子：
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通讯作者：
Runchao Han;Haoyu Lin;Jiangshan Yu
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文献类型：
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作者：
Runchao Han;Haoyu Lin;Jiangshan Yu
原子交换允许双方在不受信任的第三方的情况下自动交换自己的加密货币。本文首次对原子交换协议的公平性进行了定量分析，并提出了第一个公平的原子交换协议及其实现。特别地，我们将原子掉期建模为美国看涨期权，并证明原子掉期等同于没有溢价的美国看涨期权。因此，原子交换对交换参与者是不公平的。然后，我们量化原子掉期的公平性，并将其与传统金融资产（股票和法定货币）的公平性进行比较。量化结果表明，在相同的环境下，原子掉期对加密货币的不公平程度远高于股票和法定货币。此外，我们使用《金融》杂志中传统的Cox-Ross-Rubinstein期权定价模型来估计溢价，并表明加密货币的估计溢价为资产价值的2% ~ 3%，而股票和法定货币的溢价约为0.3%。此外，我们提出了两种公平的原子掉期协议，一种用于货币兑换，另一种用于美式看涨期权。我们的协议基于原始的原子交换协议，但实现了溢价机制。支持智能合约的区块链，如以太坊，直接支持我们的协议。只支持比特币等脚本的区块链可以通过添加简单的操作码来支持我们的协议。最后，我们在Solidity中提供了我们协议的参考实现，并给出了使用比特币脚本实现我们协议的详细说明。
Atomic Swap enables two parties to atomically exchange their own cryptocurrencies without trusted third parties. This paper provides the first quantitative analysis on the fairness of the Atomic Swap protocol, and proposes the first fair Atomic Swap protocol with implementations. In particular, we model the Atomic Swap as the American Call Option, and prove that an Atomic Swap is equivalent to an American Call Option without the premium. Thus, the Atomic Swap is unfair to the swap participant. Then, we quantify the fairness of the Atomic Swap and compare it with that of conventional financial assets (stocks and fiat currencies). The quantification results show that the the Atomic Swap is much more unfair on cryptocurrencies than on stocks and fiat currencies in the same setting. Moreover, we use the conventional Cox-Ross-Rubinstein option pricing model in Finance to estimate the premium, and show that the estimated premium for cryptocurrencies is 2% ~ 3% of the asset value, while the premium for stocks and fiat currencies is approximately 0.3%. Furthermore, we propose two fair Atomic Swap protocols, one is for currency exchange and the other is for American Call Options. Our protocols are based on the original Atomic Swap protocol, but implement the premium mechanism. Blockchains supporting smart contracts such as Ethereum support our protocols directly. Blockchains only supporting scripts such as Bitcoin can support our protocols by adding a simple opcode. Finally, we provide the reference implementation of our protocols in Solidity, and give detailed instructions on implementing our protocols with Bitcoin script.