Voting mechanisms are widely accepted and used methods for decentralized decision-making. Ensuring the acceptance of the voting mechanism's outcome is a crucial characteristic of robust voting systems. Consider this scenario: A group of individuals wants to choose an option from a set of alternatives without requiring an identification or proof-of-personhood system. Moreover, they want to implement utilitarianism as their selection criteria. In such a case, players could submit votes multiple times using dummy accounts, commonly known as a Sybil attack (SA), which presents a challenge for decentralized organizations. Is there a voting mechanism that always prevents players from benefiting by casting votes multiple times (SA-proof) while also selecting the alternative that maximizes the added valuations of all players (efficient)? One-person-one-vote is neither SA-proof nor efficient. Coin voting is SA-proof but not efficient. Quadratic voting is efficient but not SA-proof. This study uses Bayesian mechanism design to propose a solution. The mechanism's structure is as follows: Players make wealth deposits to indicate the strength of their preference for each alternative. Each player then receives an amount based on their deposit and the voting outcome. The proposed mechanism relies on two main concepts: 1) Transfers are influenced by the outcome in a way that each player's optimal action depends only on individual preferences and the number of alternatives; 2) A player who votes through multiple accounts slightly reduces the expected utility of all players more than the individual benefit gained. This study demonstrates that if players are risk-neutral and each player has private information about their preferences and beliefs, then the mechanism is SA-proof and efficient. This research provides new insights into the design of more robust decentralized decision-making mechanisms.

翻译：投票机制是广泛接受并用于去中心化决策的方法。确保投票机制结果的可接受性是稳健投票系统的关键特征。考虑以下场景：一组个体希望从一组备选方案中选择一个选项，且无需身份认证或人格证明系统。此外，他们希望以功利主义作为选择标准。在这种情况下，参与者可能使用虚假账户多次投票（通常称为女巫攻击），这对去中心化组织构成了挑战。是否存在一种投票机制，既能始终防止参与者通过多次投票获益（抗女巫攻击），又能选择使所有参与者估值总和最大化的备选方案（高效）？一人一票制既不抗女巫攻击也不高效。代币投票机制抗女巫攻击但缺乏效率。二次投票机制高效但不抗女巫攻击。本研究采用贝叶斯机制设计提出一种解决方案。该机制结构如下：参与者通过财富质押来表明对每个备选方案的偏好强度，随后根据其质押金额和投票结果获得相应回报。所提出的机制基于两个核心概念：1）转移支付与投票结果相关联，使得每个参与者的最优行动仅取决于个人偏好和备选方案数量；2）通过多个账户投票的参与者，其行为对所有参与者预期效用的轻微降低程度将超过其个人所获收益。本研究证明，若参与者风险中性且各自拥有关于偏好和信念的私有信息，则该机制同时具备抗女巫攻击性和高效性。这项研究为设计更稳健的去中心化决策机制提供了新的见解。