Eleven-month-old startup Coinbase announced Tuesday the largest funding round to date for a Bitcoin startup, a $5 million investment led by Union Square Ventures.

In an exclusive interview with The Wall Street Journal, Coinbase's founders Fred Ehrsam and Brian Armstrong said the Series A deal--which followed a seed round in September 2012 of $600,000--will help the San Francisco company cover operating costs and hire engineers, designers and business-support staff.

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