Electrum 2/2 PSBT Multi-sig

Keystone firmware version V1.1.1 (BTC-Only) or newer supports PSBT Muti-signature function. This instruction will show how to create a 2/2 PSBT Multi-signature with Keystone, Coldcard and Electrum V4.1.2 in details.
2/2 PSBT Multi-sig is not a good quorum. This tutorial is just for the purpose of showing how to use Keystone and Coldcard to set up your multi-sig wallet with Electrum. Learn more about picking a good quorum: https://btcguide.github.io/quorum​
I. Preparation
1. Firmware version V1.1.1 (BTC-Only) or newer running on Keystone Essential or Pro.
   (Please read How to upgrade firmware for more details.)
2. Coldcard upgraded to firmware version V2.1.0 or newer.
3. MicroSD card (≤512GB; Default FAT32 format).
How to Format a MicroSD Card to FAT32?
4. Electrum Wallet (V4.1.2 or newer) running on PC/Mac.
Tips: If you want to switch to [Test Net], please go to "Keystone > Settings > Blockchain > Test Net" and "Coldcard > Settings > Blockchain > Test Net". Then continue with the following steps.
II. Create a 2/2 multisig wallet with Keystone and Coldcard
- Create multisig wallet on Coldcard
1. Export Keystone's Xpub to microSD card
1) Insert the microSD card into Keystone
2) Touch [Menu] > [Multisig Wallet] > Press the [•••] button on the top right > [Show/Export XPUB].
3) Touch [Export All] > [Export].
2. Create multisig wallet on Coldcard
1) Take the microSD card from your Keystone and insert it into Coldcard.
2) [Settings] > [Multisig Wallets] > [Create Airgapped]
3) Set address type (Default-P2WSH) and the number of cosigner (2 of 2).
4) Confirm (√) and complete creating a 2/2 multisig wallet.
3. After the previous steps, you will get 2 files on your microSD card:
1) “export-CC-2-of-2.txt” - this is for importing multi-sig wallet to Keystone - allows Keystone to check the genuinity of multisig when signing.
2) “el-CC-2-of-2.json” - this is for creating watch-only wallet on Electrum.
If you didn’t get these two files, please export manually by following instructions:
1) Export the multisig wallet file (for importing multisig wallet to Keystone) to the microSD card.
① Insert the microSD card into Coldcard.
② [Settings] > [Multisig Wallets] > [2/2: CC-2-of-2] > [Coldcard Export] > Export the “export-CC-2-of-2.txt” file to the microSD card.
2) Export the multisig wallet file (for creating watch-only wallet on Electrum) to the microSD card.
① Insert the microSD card into Coldcard.
② [Settings] > [Multisig Wallets] > [2/2: CC-2-of-2] > [Electrum Export] > Export the “el-CC-2-of-2.json” file to the microSD card.
- Import multisig wallet file to Keystone
1. Take out the microSD card from Coldcard and insert it into Keystone.
2. Tap [Menu] > [Multisig Wallets] > [Import Multisig Wallet].
3. Select file “export-CC-2-of-2.txt” > Click on [Confirm].
- Import multisig wallet file to Electrum and create watch-only wallet
1. Take out the microSD card from Keystone and insert it into PC/Mac.
2. Run Electrum, then click on [choose...] > Select file “el-CC-2-of-2.json” > [Open] > [Next]> [No].
Note: As Electrum doesn’t have a Keystone plugin (we are working on that), Keystone can’t generate a Electrum skeleton json file. So you have to export the Electrum skeleton json file from Coldcard to set up the watch-only wallet on Electrum.
IV. Sending bitcoin from the 2/2 multisig address (Keystone & Coldcard)
- Generate multisig transaction on watch-only wallet(Electrum) and export unsigned multisig transaction file to microSD card.
1. Click on [Send] > Enter destination address and amount > [Pay] > [Send].
2. Click on [Export] > [For hardware device; include xpubs] > [Export for file] > [Save].
- Partially sign multisig transaction on Coldcard
1. Take out the microSD card from PC/Mac and insert it into Coldcard.
2. [Ready To Sign] > Select transaction file.
3. Confirm and export partially signed multisig transaction file to microSD card.
- Complete sign multisig transation on Keystone
1. Take out the microSD card from Coldcard and insert it into Keystone.
2. Enter Multisig Wallet > Press "microSD card" icon on the top right > Select the partially signed transaction file > Confirm transation details and press [Sign].
3. Password Verification > Press [Export] to export fully signed multisig transaction file to the microSD card.
- Broadcast multisig transaction with Electrum
1. Click on [Tools] > [Load transaction] > [From file] > Select fully signed multisig transaction file > [Open] > [Broadcast].
​
 Instructions recommended: Delete Multisig Wallet on Keystone 、Electrum 2/3 PSBT Multi-sig​
Electrum 2/3 PSBT Multi-sig
Delete Multisig Wallet