A Fully Local Last-Generated Rule in a Blockchain

TL;DR

This paper introduces a new locally applicable last-generated rule for blockchains that reduces the risk of honest miners following attackers during chain ties by using a conservative time-based approach.

Contribution

It proposes a simple, fully local last-generated rule based on relative time, improving security against adversaries in blockchain systems like Bitcoin.

Findings

Reduces honest miners following attackers by over 40%

Uses a conservative clock skew bound of 200 seconds

Enhances local applicability of last-generated rules

Abstract

An effective method for suppressing intentional forks in a blockchain is the last-generated rule, which selects the most recent chain as the main chain in the event of a chain tie. This rule helps invalidate blocks that are withheld by adversaries for a certain period. However, existing last-generated rules face an issue in that their applications to the system are not fully localized. In conservative cryptocurrency systems such as Bitcoin, it is desirable for methods to be applied in a fully local manner. In this paper, we propose a locally applicable last-generated rule. Our method is straightforward and is based on a relative time reference. By conservatively setting the upper bound for the clock skews $\Delta_{O_i}$ to 200 s, our proposed method reduces the proportion $\gamma$ of honest miners following the attacker during chain ties by more than 40% compared to existing local methods.