Blockchain.com says it's raised $300 million in a mega fundraising round, valuing the company at $5.2 billion. : LONDON — Blockchain.com, one of the world's largest cryptocurrency wallet providers, announced Wednesday that it's raised $300 million in a mega fundraising round that values the company at $5.2 billion. The London-based start-up said its latest cash injection was led by DST Global, Lightspeed Venture Partners and VY Capital. It comes just one month after the company raised $120 million at a $3 billion valuation. Blockchain.com claims to be responsible for about 28% of all bitcoin transactions since 2012.