In distributed systems with asymmetric trust, each participant is free to make its own trust assumptions about others, captured by an asymmetric quorum system. This contrasts with ordinary, symmetric quorum systems and threshold models, where trust assumptions are uniformly shared among participants. Fundamental problems like reliable broadcast and consensus are unsolvable in the asymmetric model if quorum systems satisfy only the classical properties of consistency and availability. Existing approaches overcome this by introducing stronger assumptions. We show that some of these assumptions are overly restrictive, so much so that they effectively eliminate the benefits of asymmetric trust. To address this, we propose a new approach to characterize asymmetric problems and, building upon it, present algorithms for reliable broadcast and consensus that require weaker assumptions than previous solutions. Our methods are general and can be extended to other core problems in systems with asymmetric trust.

翻译：在具有非对称信任的分布式系统中，每个参与者可自由设定对其他参与者的信任假设，这种假设通过非对称仲裁系统来刻画。这与普通的对称仲裁系统和阈值模型形成对比，后者的信任假设在所有参与者间均匀共享。如果仲裁系统仅满足经典的一致性和可用性属性，则可靠广播和共识等基本问题在非对称模型中无法求解。现有方法通过引入更强的假设来克服这一限制。我们证明其中某些假设过于严格，以至于实际上消除了非对称信任的优势。为此，我们提出一种刻画非对称问题的新方法，并在此基础上提出了可靠广播与共识算法，这些算法所需的假设条件较以往解决方案更弱。我们的方法具有普适性，可扩展至非对称信任系统中的其他核心问题。