Bitcoin: Censorship Resistance Against Hash Dominance

Abstract

Bitcoin's resistance to censorship is potentially vulnerable to attacks via hash power concentration; this paper analyzes their impact using probabilistic models and realistic simulations. We prove that these attacks are incapable of breaching the anticensorship defences present by design in the Proof of Work regardless of attackers hash power dominance. Complex scenarios are studied including cumulating Compliance Attack with Selfish Mining by pools, and a novel Detente Attack of colluding malicious pools. Our findings reinforce the robustness of Bitcoin's neutrality and provides a quantitative framework to its limits with a new metric termed Nuisance that measures delays of censored transactions.