Offline signing

Offline signing keeps your Monero spend key on a computer that never connects to the internet. It works like a hardware wallet, done by hand: the online computer prepares the payment, the offline one signs it, the online one broadcasts it.

What you need

• The offline computer: a laptop that stays offline for good, ideally with an encrypted disk. It holds the full wallet.
• The online computer: your everyday one. It holds a view-only copy.
• A way to move data between them: animated QR codes, with a webcam on each side (a cheap 720p USB webcam is enough), or files on a USB stick or SD card.

Setting up

1. On the offline computer, turn on Settings › Network › Offline › Disable all network connections (offline mode). Then create a wallet and write down its seed.
2. On the offline wallet, click View-only details, then Show QR.
3. On the online computer, choose Restore wallet from… › Keys, click Scan QR and scan it. Go through the steps; the restore height is filled in.

The offline wallet shows no balance and no history: it never sees the blockchain. Use the online one for that, and to get addresses. To check an address against the offline wallet, click Show address there and enter its number.

Sending

Send from the online, view-only wallet as usual. A window opens with an animated QR code and guides you; on the offline wallet, click Sign a transaction. Then, taking turns:

1. Offline scans the outputs shown by the online wallet.
2. Online clicks Next and scans the key images shown by the offline wallet, then builds the transaction.
3. Offline clicks Next, scans the unsigned transaction, checks the destination and the amount, and clicks Sign.
4. Online clicks Next, scans the signed transaction, and confirms to broadcast it.

Steps 1 and 2 only happen when the wallets need to catch up, usually the first time. The scanner shows a progress bar; keep scanning if it sits at 99%.

To use files instead, choose Tools › Offline transaction signing and the file option. Tools › Transmit over UR sets the size and speed of the animated codes.

If scanning is hard

• Turn on manual exposure in the scanner, if your webcam has it, and adjust the slider.
• Make the window bigger, lower the screen brightness, or try the dark theme.
• In the settings next to the code, make the fragments smaller and slower.
• A “double spend” error when sending: Wallet › Advanced › Rescan spent on the online wallet.

On Windows 10, webcams need version 22H2 or later.