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Sign Bitcoin with separate computers

KeepKey remains a USB signer. In this workflow it connects to the signing computer; a file or QR transfer connects the two computer workflows. KeepKey itself has no camera or removable-media signing slot. A disconnected computer still needs to inspect untrusted transaction data.

Watch the overview: Separate the computers.

Before you start

Install the required apps and dependencies before disconnecting. Prepare matching public account information on the online computer. Confirm that your signing build supports PSBT import and, for QR transfer, the same encoding as the sender. Practice with a separate low-value wallet before using this as an operating procedure.

Sign Bitcoin offline

Watch this step.

  1. Use matching public account information on both computers. Install the required software before disconnecting the signing computer.
  2. In Sparrow, review the destination, amount, every output and fee.
  3. Choose Finalize Transaction for Signing. This prepares the payment; it does not sign.
  4. Choose Save Transaction and save the unsigned PSBT file.
  5. Copy that file to a thumb drive and move it to the disconnected signing computer.
  6. Open the file in KeepKey Desktop and inspect the payment.
  7. In this example, six thousand sixty-six satoshis fund a five thousand nine hundred fifty-six satoshi payment and a one hundred ten satoshi fee.
  8. Compare the destination and amount on KeepKey. Check the total shown by the device.
  9. Desktop reports the signed file saved. Signing does not broadcast the payment.
  10. Load the signed file in Sparrow. Inspect the final transaction and fee before choosing Broadcast Transaction.

Transfer a transaction by QR

Watch this step.

  1. This route uses Desktop on both computers. Prepare their matching public account and signing setup first.
  2. On the online computer, create and inspect the unsigned PSBT, then choose Show unsigned QR.
  3. On the signing computer, choose Scan Bitcoin QR and allow camera access. Keep scanning until the transaction review opens.
  4. Review all outputs and fee in Desktop, then compare the requested details on KeepKey before approving.
  5. Scan the signed result on the online computer and inspect it before broadcasting.

Resume from saved files

Watch this step.

  1. Save the unsigned PSBT before closing the creator. Keep the signed result when signing finishes.
  2. Restart Desktop on the signing computer with networking still disconnected. Connect and unlock the intended KeepKey.
  3. Read the fresh account and transaction checks. Compare destination, amount, change and fee with the payment you intended.
  4. If a signed file already exists, return it to the online computer and open it for final inspection.
  5. Check whether the same transaction was already broadcast before choosing to send.

Verify the result

Keep the original unsigned PSBT and the saved signed result. After returning online, compare all outputs and fee with the original and check whether the transaction was already submitted. Signing, broadcast and confirmation are different states; see inspect the signed result.

If something fails

Missing previous transactions or incompatible QR encoding are import failures, not reasons to weaken checks. Recover the original complete file or supported encoding. If a transfer is interrupted, resume from saved files and check submission status before broadcasting again.

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