In the last year, Coinbase has been at the center of both the boom and bust in cryptocurrencies. After Coinbase became the most downloaded iPhone app for a short period in late 2017, its shares traded on the secondary market at a valuation of $4.5 billion. It runs a brokerage business, where retail customers can buy cryptocurrencies like bitcoin or ether using a bank account, and an exchange, where traders can make bids and offers on cryptocurrencies. Coinbase mostly makes money on fees it charges its customers, so it has continued to do well as the prices of cryptocurrencies plunged.
The first wallet program, simply named Bitcoin, and sometimes referred to as the Satoshi client, was released in 2009 by Satoshi Nakamoto as open-source software.[10] In version 0.5 the client moved from the wxWidgets user interface toolkit to Qt, and the whole bundle was referred to as Bitcoin-Qt.[100] After the release of version 0.9, the software bundle was renamed Bitcoin Core to distinguish itself from the underlying network.[101][102]

The debate over whether bitcoin should be considered a legal tender has accelerated in the wake of the high-profile attack of Japanese exchange Mt. Gox and the widespread adoption of it in payment processing at major U.S. retailers. Unlike the U.S. dollar, the Chinese yuan, or the euro, bitcoin is not recognized universally as a currency by every participant of the global markets, including regulators and government officials.


In 2014, prices started at $770 and fell to $314 for the year.[32] In February 2014 the Mt. Gox exchange, the largest bitcoin exchange at the time, said that 850,000 bitcoins had been stolen from its customers, amounting to almost $500 million. Bitcoin's price fell by almost half, from $867 to $439 (a 49% drop). Prices remained low until late 2016.[citation needed]
In 2014, researchers at the University of Kentucky found "robust evidence that computer programming enthusiasts and illegal activity drive interest in bitcoin, and find limited or no support for political and investment motives".[128] Australian researchers have estimated that 25% of all bitcoin users and 44% of all bitcoin transactions are associated with illegal activity as of April 2017. There were an estimated 24 million bitcoin users primarily using bitcoin for illegal activity. They held $8 billion worth of bitcoin, and made 36 million transactions valued at $72 billion.[228][229] A group of researches analyzed bitcoin transactions in 2016 and came to a conclusion that "some recent concerns regarding the use of bitcoin for illegal transactions at the present time might be overstated".[230]
Transactions are verified by network nodes through cryptography and recorded in a public distributed ledger called a blockchain. Bitcoin was invented by an unknown person or group of people using the name Satoshi Nakamoto[9] and released as open-source software in 2009.[10] Bitcoins are created as a reward for a process known as mining. They can be exchanged for other currencies,[11] products, and services. Research produced by the University of Cambridge estimates that in 2017, there were 2.9 to 5.8 million unique users using a cryptocurrency wallet, most of them using bitcoin.[12]
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