Securing Bitcoin payments since , Electrum is one of the most popular Bitcoin wallets. Electrum is fast, secure and easy to use. It suits the needs of a wide. Have your Bitcoins always with you, in your pocket! You pay by quickly scanning a QR-code. As a merchant, you receive payments reliably and instantly. Bitcoin. Bitcoin Core requires a one-time download of about GB of data plus a further GB per month. By default, you will need to store all of that data, but if you.