In the concept of currency, there is nothing wrong with bitcoin, so Bitcoin is clearly halal as a medium of exchange of goods.

In Islam there is no rule about what is the medium of exchange. They can be gold, silver, dates or wheat. The important thing is that the stuff is not unclean and is found in the right way.

Bitcoin can become haram when the process gets it in a haram way; gambling, cheating, money laundering or illegal transactions.