Urns Filled with Bitcoins: New Perspectives on Proof-of-Work Mining

Abstract

It is widely assumed that the selection process in a blockchain is based on proportional winning probabilities. The reliability and security of any blockchain is based upon this assumption. However, making an analogy between the Bitcoin protocol and the classical statistical urn problem, we argue that, at least on a theoretical level, the selection process in several blockchains is based on nonproportional winning probabilities. This reveals a misconception regarding the incentive structure of many blockchain protocols. We develop an empirical approach to testing for nonproportional winning probabilities in any blockchain, and offer a solution to this problem.