Stabilizing Server-Based Storage in Byzantine Asynchronous Message-Passing Systems

TL;DR

This paper introduces new algorithms for stabilizing Byzantine atomic registers in asynchronous message-passing systems, tolerating transient failures and Byzantine servers, with practical stabilization after initial writes.

Contribution

It presents the first algorithms for stabilizing Byzantine atomic storage on asynchronous servers with transient failures and Byzantine faults, using sequence numbers and time-stamps.

Findings

First stabilizing Byzantine SWSR register after initial write.

Practical stabilization achieved with bounded sequence numbers.

Tolerates up to t<n/8 Byzantine servers asynchronously.

Abstract

A stabilizing Byzantine single-writer single-reader (SWSR) regular register, which stabilizes after the first invoked write operation, is first presented. Then, new/old ordering inversions are eliminated by the use of a (bounded) sequence number for writes, obtaining a practically stabilizing SWSR atomic register. A practically stabilizing Byzantine single-writer multi-reader (SWMR) atomic register is then obtained by using several copies of SWSR atomic registers. Finally, bounded time-stamps, with a time-stamp per writer, together with SWMR atomic registers, are used to construct a practically stabilizing Byzantine multi-writer multi-reader (MWMR) atomic register. In a system of $n$ servers implementing an atomic register, and in addition to transient failures, the constructions tolerate t<n/8 Byzantine servers if communication is asynchronous, and t<n/3 Byzantine servers if it is synchronous. The noteworthy feature of the proposed algorithms is that (to our knowledge) these are the first that build an atomic read/write storage on top of asynchronous servers prone to transient failures, and where up to t of them can be Byzantine.