The blockchain is a perceptive invention - the discovery of a person or group of people. But since its invention, it has evolved into something greater and present opportunities for tempestuous innovation. Blockchain has tried to allure evreryone across different domains like industrial sector, banking, healthcare, land holdings and even the public and private sector. The blockchain is an imperishable digital log of financial transactions that can be scheduled to record not just efficient transactions but practically everything that holds a price. It enables global business transactions with less conflict and more trust. Blockchain has invented an era into technology in which the digital information can be distributed without being imitated. Bitcoin blockchain is the most popular public blockchain network, with around 10K nodes. The other big cryptocurrency blockchain project is Ethereum. Ethereum however wasn't designed to be a form of currency but instead it is intended to enable "smart contracts". Many cryptocurrencies are built on the top of blockchain, with the most popular being Bitcoin. In this paper we are going to present an overview of the blockchain technology with focus on two most widely used cryptocurrencies and their comparative analysis.
