QR Scanner
The COLDCARD® Q comes with a built-in QR scanner to make airgapped transfer of data to the device more convenient. The larger LCD screen of the Q makes scanning QR codes from the device easier as well .
QR Scanner Buttons and Indicators#
Scanner Use#
The scanner module is located at the top of the Q, under the screen. Once initiated, the scanner will produce a red strobe to give visual feedback for where it is pointed. Located next to the scanner is an LED flashlight. The light can be turned on by pressing the flashlight key, and can be used to help with hard to scan codes.
The scanner can read QR codes, BBQr codes, and barcodes. While the scanner is reading a code, the Q will flash an orange LED indicator above the screen. If scanning a BBQr code, you will also get a progress report on screen.
Depending on the data found in the code, the Q will take different actions. If no Bitcoin related data is found, then the Q will show the text of what was found in the scanned code on screen.
Start The Scanner#
From the Main Menu, you can start the scanner by pressing the QR key or selecting Scan Any QR Code.
Scan Seeds#
When setting up a COLDCARD with no main seed (either a new device, or one where you have destroyed the seed), you can import the main seed from a QR code. The Q can scan seeds in the following formats:
To do so, choose Import Existing > Scan QR Code from the Main Menu and scan your seed.
If you already have a main seed set on your COLDCARD, you can scan a different seed for use as a Temporary Seed with the option of saving it in the Seed Vault. If the scanned seed is already in your Seed Vault, then it becomes your active Temporary Seed immediately upon scanning.
Video: Verify Address via QR Code
Verify Address Ownership#
Scan a QR code containing a Bitcoin address and the Q will show you the address and ask you to press 1 if you would like to verify ownership.
If selected, the COLDCARD will search through the wallets of the active seed, including multisig wallets (Miniscript and Tapscript addresses are included in the EDGE version of the firmware), to verify ownership of the address.
If the address is verified successfully, you will be shown Verified Address with details about the address.
If the address cannot be found, the Q will show Unknown Address.
Danger of Not Verifying Address Ownership
Failure to verify address ownership can leave you vulnerable to attacks via compromised mobile or desktop wallets that may be displaying addresses not generated by your COLDCARD.
Video: Send Bitcoin via QR Code
Sign PSBT#
When scanning a QR or BBQr code containing an unsigned PSBT that has inputs owned by the active seed, the Q will show you the details of the transaction and ask if you would like to sign it.
In order to sign the PSBT, you should review the details and press Enter if they are correct. The Q will sign the PSBT and present a QR or BBQr code for export to a wallet that can broadcast it.
If you have NFC Push TX enabled, then after signing the Q will begin to broadcast the transaction over NFC. You can tap the Q with an NFC enabled phone to open a browser and broadcast the transaction via your chosen service provider.
In the case where the inputs of the scanned PSBT are not owned by the active seed, then the Q will show the XFP of the seed needed to sign the PSBT.
Video: COLDCARD Q: Secure Notes & Passwords
Transfer Text#
At various text entry prompts the Q will give the option to import text to the COLDCARD via QR code. One such time is during entry of Secure Notes & Passwords.
The Q will indicate that you can use the scanner instead of typing the text by showing a QR key symbol on the screen.
Press the QR key to start the scanner, and scan a QR code of any text.
BBQr/QR Scanning Limitations#
BBQr Scanning#
- Files up to 2MiB in size can be accepted.
- When there are 14 or less parts, the Q displays the status of each part.
- If there are more than 14 parts, the Q will show percent complete.
QR Scanning#
- If not BBQr (or sent as unicode inside BBQr) the Q will auto detect these data types:
- PSBT in Base64 or hex
- Finalized transaction (ready for broadcast) in hex
- XPRV, XPUB, bare payment addresses, BIP-21 invoices
- Seed words (truncated, or full)
- SeedQR (but not Compact SeedQR)
- Textual multisig in COLDCARD or descriptor format
- For Base58, Bech32 encoded values, if the checksum is wrong then it is shown as text.
- Binary QR codes are not supported.
- When pasting into a Secure Note, if the QR's data is over 60 characters long, we assume done.