Stick a fork in it: Analyzing the Ethereum network partition.

As blockchain technologies and cryptocurrencies increase in popularity, their decentralization poses unique challenges in network partitions. In traditional distributed systems, network partitions are generally a result of bugs or connectivity failures; the typical goal of the system designer is to automatically recover from such issues as seamlessly as possible. Blockchain-based systems, however, rely on purposeful "forks" to roll out protocol changes in a decentralized manner. Not all users may agree with proposed changes, and thus forks can persist, leading to permanent network partitions. In this paper, we closely study the large-scale fork that occurred in Ethereum, a new blockchain technology that allows for both currency transactions and smart contracts. Ethereum is currently the second-most-valuable cryptocurrency, with a market capitalization of over $28B. We explore the consequences of this fork, showing the impact on the two networks and their mining pools, and how the fork lead to unintentional incentives and security vulnerabilities.