Users bid in a transaction fee mechanism (TFM) to get their transactions included and confirmed by a blockchain protocol. Roughgarden (EC'21) initiated the formal treatment of TFMs and proposed three requirements: user incentive compatibility (UIC), miner incentive compatibility (MIC), and a form of collusion-resilience called OCA-proofness. Ethereum's EIP-1559 mechanism satisfies all three properties simultaneously when there is no contention between transactions, but loses the UIC property when there are too many eligible transactions to fit in a single block. Chung and Shi (SODA'23) considered an alternative notion of collusion-resilience, called c-side-contract-proofness (c-SCP), and showed that, when there is contention between transactions, no TFM can satisfy UIC, MIC, and c-SCP for any c at least 1. OCA-proofness asserts that the users and a miner should not be able to "steal from the protocol." On the other hand, the c-SCP condition requires that a coalition of a miner and a subset of users should not be able to profit through strategic deviations (whether at the expense of the protocol or of the users outside the coalition). Our main result is the first proof that, when there is contention between transactions, no (possibly randomized) TFM in which users are expected to bid truthfully satisfies UIC, MIC, and OCA-proofness. This result resolves the main open question in Roughgarden (EC'21). We also suggest several relaxations of the basic model that allow our impossibility result to be circumvented.

翻译：在交易费用机制中，用户通过出价使其交易被区块链协议打包并确认。Roughgarden（EC'21）开创了对交易费用机制的正式研究，并提出了三项要求：用户激励兼容性、矿工激励兼容性以及一种称为OCA抗合谋性的抗合谋形式。当交易间不存在竞争时，以太坊的EIP-1559机制能同时满足所有三项特性；但当合格交易数量超过单个区块容量时，该机制会丧失用户激励兼容性。Chung与Shi（SODA'23）提出了另一种抗合谋性概念——c方合约抗合谋性，并证明当交易存在竞争时，对于任意c≥1，不存在任何交易费用机制能同时满足用户激励兼容性、矿工激励兼容性及c方合约抗合谋性。OCA抗合谋性主张用户与矿工不应具备"从协议中窃取利益"的能力；而c方合约抗合谋性则要求矿工与用户子集组成的联盟无法通过策略性偏离获利（无论损害的是协议利益还是联盟外用户的利益）。我们的主要成果首次证明：当交易存在竞争时，任何期望用户诚实出价的（可能随机化的）交易费用机制都无法同时满足用户激励兼容性、矿工激励兼容性与OCA抗合谋性。该结果解决了Roughgarden（EC'21）中提出的核心开放性问题。我们还提出了若干基础模型的松弛条件，这些条件可以规避我们的不可能性结论。