Digital currency exchange Coinbase announced on its blog on Thursday that it has raised US$100 million in so-called "Series D" funding led by U.S. venture capital firm IVP, making it the first bitcoin start-up to achieve a valuation of at least US$1 billion. Start-ups with a US$1 billion valuation are part of what is called a "unicorn" club in the venture capital industry. The US$1 billion valuation was estimated by data and research provider Pitchbook. Series D is generally the fifth stage of funding, following a seed investment, and series A through C rounds. With the new investment, Coinbase has raised US$217 million since it launched in 2012. It raised US$75 million more than two years ago and then secured an additional US$10.5 million in July 2016, Pitchbook data showed. The other participants in Coinbase's Series D funding were Spark Capital, Greylock Partners, Battery Ventures, Section 32 and Draper Associates. Draper Associates was an investor in a previous financing round, Coinbase said. The funds will be used to finance the company's expansion, Brian Armstrong, chief executive officer and founder of Coinbase, said on the company's blog. Specifically, Coinbase wants to increase the size of its engineering and customer support teams and open an office in New York for GDAX, the company's trading platform for institutional investors. Coinbase, which operates in 32 countries, said it also wants to grow its investment in Toshi, a browser for the Ethereum network. Ethereum is blockchain, similar to that of bitcoin. Armstrong said Coinbase is beginning to transition into the third phase of its expansion and wants to build digital currency applications for consumers. "The key feature of this application will be that it dramatically lowers the hurdle for new digital currency applications to be developed and used by ordinary people," Armstrong said.