Preliminaries paper: Byzantine Tolerant Strong Auditable Atomic Register

TL;DR

This paper investigates the minimum server requirements for Byzantine resilient auditable registers in asynchronous systems, demonstrating that strong auditability can be achieved with fewer servers when server communication is allowed.

Contribution

It proves that strong auditable registers can be implemented with 3f+1 servers using server-to-server communication, reducing the known server count needed for auditability.

Findings

4f+1 servers are necessary without server communication.

3f+1 servers suffice with server-to-server communication.

Strong auditability does not increase server count when communication is allowed.

Abstract

An auditable register extends the classical register with an audit operation that returns information on the read operations performed on the register. In this paper, we study Byzantine resilient auditable register implementations in an asynchronous message-passing system. Existing solutions implement the auditable register on top of at least 4f+1 servers, where at most $f$ can be Byzantine. We show that 4f+1 servers are necessary to implement auditability without communication between servers, or implement does not implement strong auditability when relaxing the constraint on the servers' communication, letting them interact with each other. In this setting, it exists a solution using 3f+1 servers to implement a simple auditable atomic register. In this work, we implement strong auditable register using 3f+1 servers with server to server communication, this result reinforced that with communication between servers, auditability (event strong auditability) does not come with an additional cost in terms of the number of servers.