Recent works of Roughgarden (EC'21) and Chung and Shi (SODA'23) initiate the study of a new decentralized mechanism design problem called transaction fee mechanism design (TFM). Unlike the classical mechanism design literature, in the decentralized environment, even the auctioneer (i.e., the miner) can be a strategic player, and it can even collude with a subset of the users facilitated by binding side contracts. Chung and Shi showed two main impossibility results that rule out the existence of a {\it dream} TFM. First, any TFM that provides incentive compatibility for individual users and miner-user coalitions must always have zero miner revenue, no matter whether the block size is finite or infinite. Second, assuming finite block size, no non-trivial TFM can simultaenously provide incentive compatibility for any individual user, and for any miner-user coalition. In this work, we explore what new models and meaningful relaxations can allow us to circumvent the impossibility results of Chung and Shi. Besides today's model that does not employ cryptography, we introduce a new MPC-assisted model where the TFM is implemented by a joint multi-party computation (MPC) protocol among the miners. We prove several feasibility and infeasibility results for achieving {\it strict} and {\it approximate} incentive compatibility, respectively, in the plain model as well as the MPC-assisted model. We show that while cryptography is not a panacea, it indeed allows us to overcome some impossibility results pertaining to the plain model, leading to non-trivial mechanisms with useful guarantees that are otherwise impossible in the plain model. Our work is also the first to characterize the mathematical landscape of transaction fee mechanism design under approximate incentive compatibility, as well as in a cryptography-assisted model.

翻译：Roughgarden（EC'21）以及Chung和Shi（SODA'23）的最新研究开创性地提出了一种新的去中心化机制设计问题——交易费机制设计（TFM）。与传统机制设计文献不同，在去中心化环境中，即便是拍卖者（即矿工）也可能成为策略性参与者，甚至可通过具有约束力的侧合同与部分用户合谋。Chung和Shi给出了两项主要的不可能性结果，排除了“理想”TFM的存在性。第一，无论区块大小是有限还是无限，任何为单个用户和矿工-用户联盟提供激励相容性的TFM，其矿工收益必然为零。第二，假设区块大小有限，则不存在任何非平凡TFM能同时为任意单个用户和任意矿工-用户联盟提供激励相容性。本文探索了哪些新模型和有意义的松弛条件能够规避Chung和Shi的不可能性结果。除当前不依赖密码学的模型外，我们引入了一种新的MPC辅助模型，其中TFM通过矿工间的联合多方计算（MPC）协议实现。我们分别证明了在普通模型和MPC辅助模型下，实现“严格”与“近似”激励相容性的若干可行性及不可行性结果。研究表明，尽管密码学并非万能，但它确实能够克服普通模型中的某些不可能性结果，从而设计出具有实用保证的非平凡机制——这些机制在普通模型中是无法实现的。本文还首次刻画了近似激励相容性下以及密码学辅助模型下交易费机制设计的数学全景。