Send Funds from Electrum using COLDCARD via MicroSD Card (~5 min)

  1. Open the Electrum COLDCARD signing wallet you previously created

  2. Click on the Send tab

  3. Enter the recipient's address in the Pay to field

    Electrum Send

    • Tip: Use the camera icon to scan a QR code of the recipient's address

  4. (Optional) Enter a description to be stored only in the local Electrum wallet file (this can only be stored unencrypted, unfortunately)

  5. Enter Amount in mBTC (1000th of a BTC)

  6. Click the Pay button

    Electrum Click Pay

  7. Click the Advanced button in the Confirm Transaction dialog box

    Electrum Send Confirm

  8. Adjust the fee as necessary and click the Finalize button

    Electrum Finalize

  9. Click the Export menu-button and select For hardware device; include xpubs > Export to file

    Export Transaction

  10. Browse to the microSD card to save the .psbt file to the microSD card and click Save

    Export Transaction

  11. Safely eject the microSD card using the icon in the Windows Desktop Tray

    Safe Eject

  12. Physically remove the microSD card and insert it into the COLDCARD for signing

  13. On the COLDCARD, press X as many times as necessary until you are returned to the main menu

  14. Select Ready to Sign and press [CHECK]

  15. Review and approve the transaction for signing

    1. Verify the amount!

    2. Verify the recipient address! Double and triple-check!

    3. Verify the network fee! (It should be relatively small; something on the order of 0.00000500 BTC)

    4. Press [CHECK] to approve the transaction

      • The COLDCARD will display a PSBT Signed message, including:

        • The filename of the signed transaction (e.g. coldcard_wallet.json-20200727-1331-signed.psbt). This file is useful in a case of a transaction that requires multiple signatures. In such a case, you would pass this file around to the signatories for signing until it contains a signature from each one. (NOT our case)

        • The filename of the finalized transaction (e.g. coldcard-wallet.json-20200727-1331-final.txn). This file contains a fully-signed transaction, ready for broadcast to the Bitcoin network. (This is the file we're interested in).

    5. Press [CHECK] to return to the main menu

  16. Eject the microSD card from the COLDCARD and insert it into the computer

  17. From the Elecrum menu, select Tools > Load transaction > From file

    Load Transaction

  18. Browse to the microSD card, select the file ending -final.txn and click Open

    Select Transaction

  19. Click Broadcast to broadcast the transaction to the Bitcoin network

  20. Electrum will broadcast the transaction and display the transaction ID

    Broadcast Transaction

    • Note: You have just broadcast a transaction out to the Bitcoin network through your own node; in the most private way possible!

  21. Open up your private block explorer on the Tor Browser and lookup this transaction to confirm (either using one of the addresses or the transaction ID)

  22. There's also no harm in searching for the Transaction ID on a 3rd party block explorer using an onion link via the Tor Browser

    • Blockstream.info's onion url is: explorerzydxu5ecjrkwceayqybizmpjjznk5izmitf2modhcusuqlid.onion

    • If you search for more than one piece of information on a 3rd party block explorer, it's best to switch to a new Tor identity between requests by clicking on the New Identity button so that the explorer can't learn that there is a relationship between two addresses or seemingly-unrelated transactions

      Tor New Identity