Meanwhile Hill Ferguson from PayPal – the granddaddy of digital payments firms – confirmed the company is keeping an eye on the crypto-currency.

"It's the perfect currency by design," he said. "I'm curious to see how governments respond to it and how regulation may impact consumers' ability to get money in and out. I think it's a fascinating phenomenon and we are definitely watching it."

Ferguson also sounded a skeptical note. "What problem is Bitcoin trying to fix? There's no clear answer."