Asymmetric Distributed Trust
This work addresses the need for more flexible trust models in distributed systems prone to Byzantine faults, representing a foundational advancement rather than an incremental improvement.
The paper tackles the problem of modeling subjective trust in distributed fault-tolerant computing by introducing asymmetric Byzantine quorum systems, which allow each process to define its own trust assumptions, and presents protocols for shared memory, broadcast, and consensus that achieve these capabilities.
Quorum systems are a key abstraction in distributed fault-tolerant computing for capturing trust assumptions. They can be found at the core of many algorithms for implementing reliable broadcasts, shared memory, consensus and other problems. This paper introduces asymmetric Byzantine quorum systems that model subjective trust. Every process is free to choose which combinations of other processes it trusts and which ones it considers faulty. Asymmetric quorum systems strictly generalize standard Byzantine quorum systems, which have only one global trust assumption for all processes. This work also presents protocols that implement abstractions of shared memory, broadcast primitives, and a consensus protocol among processes prone to Byzantine faults and asymmetric trust. The model and protocols pave the way for realizing more elaborate algorithms with asymmetric trust.