..What are cryptocurrency
a digital currency in which encryption techniques are used to regulate the generation of units of currency and verify the transfer of funds, operating independently of a central bank.
"decentralized cryptocurrencies such as bitcoin now provide an outlet for personal wealth that is beyond restriction and confiscation"
..pyramid scheme?
a form of investment (illegal in the UK and elsewhere) in which each paying participant recruits two further participants, with returns being given to early participants using money contributed by later ones.
Alexey Moiseev has said it is “hard to argue cryptocurrency is not a pyramid scheme” amid sudden plans to ban sales.