83 lines
3.5 KiB
Markdown
83 lines
3.5 KiB
Markdown
# Using Coldcard with Electrum
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(please use the latest version of our plugin)
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## Off-line signing (air gap)
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Setup Time:
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- setup your Electrum wallet associated with the seed of the Coldcard
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- can be done over USB as a connected device... ie. like normal
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- might be possible to do this completely offline
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To spend:
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- setup the details of the transaction (amount,destination)
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- press preview, or press send when the Coldcard not connected
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- you get a "transaction details" window, along bottom, new button is shown: "Save PSBT"
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- click that, and it saves a new file ... perhaps direct to SD card if you have it
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- make note of the filename; it has date and time and wallet name in it.
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- close things, move the MicroSD to Coldcard
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- pick "Ready to Sign" from main menu on Coldcard
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- select the correct transaction from list
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- observe and confirm details, press OK and the Coldcard signs it.
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- a new file will be created on SD card: `blah-final.txn` .. contains HEX of txn to send
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- use any tool to transmit that on Bitcoin P2P network... for Electrum:
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- import the final transaction (`-final.txn`), using the "Tools > Load Transaction > from File" menu item
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- press Broadcast
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- should show up in wallet immediately
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## Restoring Coldcard Seed into Electrum
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Use this process to recover your funds if you loose your Coldcard and you still
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have the seed words.
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### Import from Seed Words
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- choose New/Restore => (filename) => Standard Wallet => I already have a Seed
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- type in 24 word phrase.
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- then click "Options", and enable checkbox labeled "BIP39 seed"
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- a warning is shown:
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BIP39 seeds can be imported in Electrum, so that users can access
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funds locked in other wallets. However, we do not generate BIP39
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seeds, because they do not meet our safety standard. BIP39 seeds
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do not include a version number, which compromises compatibility
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with future software. We do not guarantee that BIP39 imports will
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always be supported in Electrum.
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- press Next (seed phrase checksum is verified, so you must get all the words right)
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### Import from Extended Public Key (XPUB)
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- You may also save the XPUB from the Coldcard and import that.
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- On the Coldcard, choose `Dump Summary` from the Advanced menu, and open the
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`public.txt` file that generated on your computer.
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- In `public.txt`, look for the section labeled "BIP44 / Electrum" and
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Copy the top `xpub` value, beside: `m/44'/0'`
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- In Electrum, choose New/Restore => (filename) => Standard Wallet => Use a master key
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- Paste in the `xpub` value into the text box and press Next.
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- Verify your work by selecting View -> Show Addresses and clicking on the Addresses tab.
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- The first few receive addresses should match the values shown in `public.txt` beside
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the text: `m/44'/0'/0'/0/0`, `m/44'/0'/0'/0/1` and so on.
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#### Note
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You could also import the master xpub (`'m'`) from that file, and
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use that key in Electrum, but that would not follow BIP44, which
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is the default when importing seed words.
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### Derivation Screen
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- default value is `m/44'/0'/0'` (legacy BIP44), but options include:
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- p2sh-segwit BIP49: `m/49'/0'/0'` [NOT YET SUPPORTED]
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- native-segwit BIP84: `m/84'/0'/0'` [should work]
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- for testnet, the first `0'` will be `1'`
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- choose appropriately... but if you imported the top-level (master) xpub/xpriv, then
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use just `m/` which really is no derivation at all
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- Electrum always uses `/{change}/{index}` for individual addresses, where:
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- `change` is one if it's change back to the wallet, and zero for normal receive
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- `index` starts at zero and counts up based on usage and gap size.
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