Short Answer: To add the Coldcard with the Bitcoin Keeper app, ensure your Coldcard is set up and updated. In the Keeper app, go to “Your Vault”, select “Add a signing device”, choose “Coldcard”, and follow the NFC and QR-based signing steps.
- Make sure your phone has an NFC reader.
- Confirm that your Keeper app is properly set up.
Preparing the Coldcard:
- Initialize your Coldcard by adhering to the instructions provided in the mentioned video.( https://www.youtube.com/watch?v=qNjgs1WJfK0)
- Check that your Coldcard has the latest firmware. Use the link provided for Coldcard’s Firmware Update Guide for a step-by-step process.(https://coldcard.com/docs/upgrade)
Integration with the Keeper App:
- Open the Keeper app and tap on the Home Screen.
- Select “Your Vault”.
- Choose “Add a signing device” and opt for “Coldcard”.
- Follow the in-app instructions, paralleling them with your Coldcard actions.
- The Coldcard will be added to your list of signing devices in the Keeper app once an NFC connection is made and the necessary file is transferred.
Registering the Keeper Vault with the Coldcard:
- Inside the Keeper app, navigate to the Vault and select the Coldcard icon.
- Tap “Advanced Options”.
- Go for “Manual registrations”. This will prompt the app to seek your Coldcard via NFC.
- On your Coldcard, proceed to [Settings] > [Multisig Wallets] > [Import via NFC]. Establish an NFC connection by bringing the Coldcard close to your phone.
- Opt for “Receive”.
- Share your Bitcoin address or QR code with the sender. Optionally, specify a set amount you’d like to receive.
- The received Bitcoin becomes accessible for expenditure based on its set priority.
Sending Bitcoin from a 2-of-3 Vault:
- Open the vault in the Keeper app and press “Send”.
- Choose the desired recipient from within Keeper or manually input a Bitcoin address (or use a QR scanner).
- Input the amount you wish to send and set its priority.
- The app will then ask you to select two devices to authenticate the transaction.
- If you choose Coldcard, the app will display the PSBT as a QR code.
- On the Coldcard, navigate to [Multisig Wallet], select the [scan] icon, and scan the Keeper app’s QR code.
- Confirm the transaction details on your Coldcard, input your password/fingerprint, and tap [Confirm] to generate a QR code representing the signed transaction.
- Return to the signature page in the Keeper app, choose [Import signature], and scan the QR code displayed on the Coldcard.
- For the second signature, repeat this procedure with another selected device.
- With signatures from both devices, select “Broadcast Transaction” in the Keeper app. To verify its success, use block explorers like mempool.space. (https://mempool.space)
Always handle your Coldcard securely and store its recovery phrase safely.