It can be concluded that the use of bitcoin as a currency in Islamic law is permissible. However, its use is not legal in Indonesia because Bank Indonesia policy in determining the currency recognized in Indonesia is only Rupiah.
In fiqh review, muamalah against Bitcoin transactions in the process using the Sharf agreement. Sharf is an activity of buying and selling currencies with currencies, both similar and non-similar, such as buying and selling gold with gold, silver with silver, or gold with silver.
Judging from the conditions of the type of transaction, the Bitcoin transaction is included in the type of spot transaction. Spot transactions or Spot Transactions are foreign exchange buying and selling transactions for delivery at the time, with a settlement time of around two days. The law is permissible, because it is considered cash while the time of two days is considered as a process of settlement of international transactions.