Double-spending analysis of bitcoin

Bitcoin is a distributed online payment system that facilitates anonymous transactions using a peer-to-peer network without a central trusted authority. Every peer in the Bitcoin network keeps the collection of all transactions which is referred to as a ledger. This public ledger will work effectively for honest peers, however, one well-known attack is the fifty-one percent or majority attack. This paper provides an Uppaal model of the Bitcoin protocol focusing on its three important components namely transactions, blocks and the blockchain. It presents a probability analysis for two scenarios of the fifty-one percent attacks. Two Phase Proof-of-Work (2PPoW) is a proposed solution to address attacks of this type, and we will extend the model to include 2PPoW and calculate the probability of a successful attack. The analysis shows that a traditional fifty-one percent attacks can be successful even if the attacker has less than a majority of the processing pool.