Bitcoin Security under Temporary Dishonest Majority
This addresses the security of Bitcoin for users and developers in scenarios with temporary adversarial control, but it is incremental as it extends existing security analyses to more realistic network conditions.
The paper tackles the problem of proving Bitcoin's security under temporary dishonest majority, where adversaries can corrupt parties and cause crash failures, and shows that security holds with a majority of honest online participants on expectation across three network models.
We prove Bitcoin is secure under temporary dishonest majority. We assume the adversary can corrupt a specific fraction of parties and also introduce crash failures, i.e., some honest participants are offline during the execution of the protocol. We demand a majority of honest online participants on expectation. We explore three different models and present the requirements for proving Bitcoin's security in all of them: we first examine a synchronous model, then extend to a bounded delay model and last we consider a synchronous model that allows message losses.