The Time to Consensus in a Blockchain: Insights into Bitcoin's "6 Blocks Rule''

TL;DR

This paper analyzes the time to reach consensus in Nakamoto blockchains, focusing on the competition between honest and adversarial growth processes, using queueing theory and simulations to understand the impact of random delays.

Contribution

It introduces a stylized Bitcoin model to compute the distribution of time to consensus considering random delays, providing new insights into blockchain stability.

Findings

Laplace transform of time to consensus computed

Simulation verifies theoretical results

Highlights impact of random delays on consensus time

Abstract

We investigate the time to consensus in Nakamoto blockchains. Specifically, we consider two competing growth processes, labeled \emph{honest} and \emph{adversarial}, and determine the time after which the honest process permananetly exceeds the adversarial process. This is done via queueing techniques. The predominant difficulty is that the honest growth process is subject to \emph{random delays}. In a stylized Bitcoin model, we compute the Laplace transform for the time to consensus and verify it via simulation.