Bitcoin, created in 2009, was the first decentralized cryptocurrency and remains the most expensive virtual currency worldwide. Other popular cryptocurrencies include: Bitcoin Cash, Ethereum, Dash, Mixin, Litecoin, Zcash, Bitcoin SV and Monero. The cryptocurrency used in the most transactions daily was Ethereum in 2019.
The decentralized control of each cryptocurrency works through Blockchain, a public transaction database that functions as a distributed ledger. The size of Bitcoin Blockchain grows from year to year and it mounted to around 242 gigabytes as of the third quarter of 2019.
The prices of cryptocurrencies are quite unstable and strongly dependent on the market sentiment. The price of Bitcoin, for example, experienced an increase from about 371 U.S. dollars in January 2016 to a peak of over 13 thousand by December 2017. Also, market capitalization of Bitcoin experienced a rapid growth in that time period.
The possibility of taking part in exceptionally high returns offered by the cryptocurrency market resulted in huge interest of investors. The number of users of Coinbase, one of the leading cryptocurrency exchanges in the U.S., increased from 0.4 million in January 2017 to 5.6 million by June 2018.
Cryptocurrencies became so popular that governments and banking regulators decided to intervene and warn that Bitcoin could be the next economic bubble. Some governments even prohibited the trading of cryptocurrencies due to lack of control and market unpredictability. Centralization of hashing power in the hands of a few or in a particular geographical area, are the main challenges affecting the cryptocurrency industry.