Asymmetric Distributed Trust

Published in Distributed Computing, 2024

Quorum systems are a key abstraction in distributed fault-tolerant computing for capturing trust as- sumptions. 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 pro- cesses 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 primi- tives, 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.

Co-authored by Orestis Alpos, Christian Cachin, and Björn Tackmann

arXiv paper here