A Survey of Attacks on the Bitcoin System

In the era of digitalization, crypto-currency has become the talk of the town and Bitcoin is one of it. Bitcoin System is not controlled by any central authority or governed by any management division. Bitcoin is the first digital decentralized currency and its economic growth has encompassed to billions of dollars within a few years. In this paper we present detailed Introduction to the digital currency including the crypto-currency, then we present Bitcoin system in depth with the process of transactions, mining, miners' pooling. As we know that the popularity of Bitcoin is increasing day by day so are the attacks. We present an analysis of major attacks in the Bitcoin system such as eclipse attack, Sybil attack, >51% attack, selfish mining. More importantly, we present how these attacks play an important role for the attackers in order to receive unfair incentives or fraud the honest users. The current researchers are focusing on creating new protocols as defensive measures for the attacks; we also analyze the security of these protocols.