VC money continues to flow into bitcoin businesses. Vaurum, a firm that develops bitcoin-exchange software that it sells to financial institutions, raised $4 million in seed funding from Battery Ventures and investors including former AOL CEO Steve Case and Tim Draper, co-founder of Draper Fisher Jurvetson.

While it didn’t disclose the names of the firms to which it’s sold its software (we asked) – or for that matter if it’s sold any of its software – it’s one more sign that Wall Street is getting serious about digital currencies.