A recent trend in multi-party computation is to achieve cryptographic fairness via monetary penalties, i.e. each honest player either obtains the output or receives a compensation in the form of a cryptocurrency. We pioneer another type of fairness, financial fairness, that is closer to the real-world valuation of financial transactions. Intuitively, a penalty protocol is financially fair if the net present cost of participation (the total value of cash inflows less cash outflows, weighted by the relative discount rate) is the same for all honest participants, even when some parties cheat. We formally define the notion, show several impossibility results based on game theory, and analyze the practical effects of (lack of) financial fairness if one was to run the protocols for real on Bitcoin using Bloomberg's dark pool trading. For example, we show that the ladder protocol (CRYPTO'14), and its variants (CCS'15 and CCS'16), fail to achieve financial fairness both in theory and in practice, while the penalty protocols of Kumaresan and Bentov (CCS'14) and Baum, David and Dowsley (FC'20) are financially fair. This version contains formal definitions, detailed security proofs, demos and experimental data in the appendix.
翻译:近期多党计算的趋势是通过货币处罚实现加密公平,即每个诚实的玩家要么获得产出,要么以加密货币的形式获得补偿。我们开创了另一种更接近真实世界金融交易估值的公平、金融公平、更接近金融交易的公平、金融公平。直觉看来,如果净参与成本(现金流入总额减去现金流出,按相对贴现率加权)对所有诚实的参与者都是一样的,即使有些当事方作弊,则惩罚协议在财务上是公平的,我们正式界定了这一概念,展示了基于游戏理论的若干不可能的结果,并分析了如果利用布隆伯格的黑池交易运行比特币真实交易协议(缺乏)金融公平的实际效果。例如,我们表明梯度协议(CRYPTO'14)及其变式(CC'15和CC'16)在理论上和实践中都没有实现财务公平,而库马里桑和本托夫(CCS'14)以及鲍姆、大卫和杜斯利(FC'20)的罚款协议则是财务上的详细证据。本版本载有正式定义、详细的安全证据和实验性数据。