What is Digital Currencies

Bitcoin is considered to be the world's first peer to peer and unregulated crypto-currency which has received widespread popularity in the last few years. It is issued and controlled by the members of the Bitcoin system. The success of Bitcoin has spurred the launch of many other crypto-currencies. Despite being widely adopted by various large scale businesses, Bitcoin transactions are still exposed to many known as well as zero-day attacks due to various vulnerabilities being exploited by the malicious entities. In order to achieve reliable and secure transactions, extensive research needs to be carried out to critically examine Bitcoin architecture and its level of security. In this regard, this chapter presents a holistic analysis of Bitcoin architecture and a survey of the attacks prevalent to its transactions. As an evaluation of the Bitcoin system, a comparison of different crypto-currencies has been presented, based on their features, possible attacks, disadvantages and the advantages which they possess over Bitcoin.