Following a series of multimillion-dollar thefts and losses, federal regulators want to step up their oversight of virtual currency bitcoin. But bitcoin — a nationless digital money that uses cryptography to control its creation and transactions — doesn’t fit neatly in any regulatory box.

“There’s an incredible interest in regulating this at the federal level,” said Kenneth Russak, a commercial-finance specialist at Frandzel Robins Bloom & Csato.