Blockchain Forks: A Formal Classification Framework and Persistency Analysis

Blockchain forks can have severe economic implications, sow uncertainty and undermine trust. In this paper, we introduce a formal framework to study the emergence, persistency and economic consequences of blockchain forks. We argue that blockchain forks can be process- or protocol-based and emerge unintentionally or deliberately. We then proceed with a sub-classification of protocol-based forks and study the circumstances under which a chain split may become permanent. It can be shown that the persistency of a fork depends on the nature of the change to the consensus rules and on the relative allocation of the consensus-relevant resources. Lastly, we discuss business implications as well as potential consequences for policy makers and practitioners.